Essential Cosmic Perspective, The, 9th edition Jeffrey O. Bennett Test Bank.pdf (12)

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Essential Cosmic Perspective

Edition: Author(s):

9th Edition Jeffrey O. Bennett Megan Donahue Nicholas Schneider Mark Voit

The Cosmic Perspective, 9e (Bennett et al.)

Chapter 1 A Modern View of the Universe Section 1.1 1) About where is our solar system located within the Milky Way Galaxy?

A) at the center of the galaxy B) about 10 percent of the way from the center of the galaxy to the edge of the galactic disk C) about halfway from the center of the galaxy to the edge of the galactic disk D) near the far edge of the galactic disk E) in the halo of the galaxy above the galactic disk Answer: C 2) When we speak of the entire universe (as opposed to the observable universe), we mean A) all the stars and galaxies that we can see with telescopes.

B) all material located within about 14 billion light-years of Earth.

C) the sum total of all matter and energy.

D) all the matter in galaxies, but not the spaces between the galaxies.

Answer: C 3) Which of the following is the smallest distance?

A) diameter of a typical planet B) 1 light-second C) 1 AU D) diameter of a typical star Answer: A 4) Which of the following is the largest distance?

A) diameter of a typical galaxy B) diameter of Pluto's orbit C) distance to the nearest star (other than our Sun) D) 1 light-year Answer: A 5) Which of the following statements does not use the term light-year in an appropriate way?

A) It's about 4 light-years from here to Alpha Centauri.

B) It will take me light-years to complete this homework assignment.

C) A light-year is about 10 trillion kilometers.

D) It will take the Voyager spacecraft about 20,000 years to travel just 1 light-year.

E) The Milky Way Galaxy is about 100,000 light-years in diameter.

Answer: B

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6) One light-minute is the distance that light travels in one minute. How far is this, in kilometers? (Recall that the speed of light is 300,000 km/s.) A) 300,000 km B) 18 million km C) 100 million km D) 1.08 billion km E) 9.46 trillion km Answer: B 7) One light-year is approximately A) the distance from the Sun to Earth. B) the speed at which Earth orbits the Sun. C) 10 trillion kilometers. D) the same as one regular year. Answer: C 8) Light takes approximately one second to travel from Earth to the Moon. This means that the Moon is approximately A) 1 astronomical unit from Earth. B) 1 light-year from Earth. C) 3000 kilometers from Earth. D) 300,000 kilometers from Earth. E) near the top of Earth's atmosphere. Answer: D 9) Sunlight takes about 8.4 minutes to travel from the Sun to Earth.

When NASA's New Horizons Spacecraft passed Pluto in 2015, it was about 32 AU from Earth. About how long did it take for transmitted images of Pluto to travel from the spacecraft to Earth? A) one Plutonian year B) 4-1/2 hours C) 2-1/4 days D) 3 weeks E) They arrived almost instantaneously. Answer: C 10) The Voyager 2 Spacecraft is currently on its way out of our solar system at a speed of about 50,000 kilometers per hour. It will reach the distance of the nearest star system (beyond our solar system) in about ________ years. A) 100 B) 1000 C) 10,000 D) 100,000 E) 1,000,000 Answer: D

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11) Suppose we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest? A) the one that is farthest away B) the one that is reddest in color C) the one that is bluest in color D) the one that is closest to us E) the one that appears smallest in size Answer: A 12) The farthest galaxies visible in Hubble Space Telescope photos are about ________ light- years away.

A) 1 million B) 12 million C) 1 billion D) 12 billion E) 12 trillion Answer: D 13) Suppose we imagine the Sun to be about the size of a grapefruit. Which of the following best describes the size and distance of Earth on the same scale? A) Earth is the size of a tip of a ballpoint pen about 1 meter from the Sun. B) Earth is the size of a golf ball about 1 meter from the Sun. C) Earth is the size of a tip of a ballpoint pen about 15 meters from the Sun. D) Earth is the size of a golf ball about 15 meters from the Sun. E) Earth is the size of a marble about 25 miles from the Sun. Answer: C 14) Suppose we imagine the Sun to be about the size of a grapefruit. How big an area would the orbits of the eight planets of the solar system cover? A) the size of a typical dorm room B) the size of a typical campus building C) the size of a typical campus D) the size of a small city E) the size of a western state (e.g., Colorado) Answer: C 15) Which of the following best describes the Milky Way Galaxy? A) a spiral galaxy with a disk about 100,000 light-years in diameter B) a spiral galaxy with a disk about 1 billion kilometers in diameter C) a spiral galaxy with a disk about 1000 lightyears in diameter D) a spherically shaped galaxy that is about 4 light-years in diameter E) a spherically shaped galaxy that is about 100,000 light-years in diameter Answer: A

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16) If we use 1 millimeter to represent 1 light-year, about how large in diameter is the Milky Way Galaxy?

A) 100 millimeters B) 100 meters C) 1 kilometer D) 100 kilometers E) 1 million millimeters Answer: B 17) How long would it take to count all the stars in the Milky Way Galaxy at a rate of one star per second?

A) several days B) several weeks C) several years D) several thousand years E) hundreds of thousands of years Answer: D 18) About how many galaxies are there in the observable universe?

A) roughly (within about a factor of 10) the same as the number of stars in our galaxy B) a few dozen C) a few thousand D) about as many as the number of grains of sand on all the beaches on Earth E) an infinite number Answer: A 19) If you represented each star by a grain of sand, about how much sand would it take to represent all the stars in the observable universe?

A) all the sand in a typical playground sandlot B) all the sand on Miami Beach C) all the sand on the beaches of California D) one cubic meter of sand E) all the sand on all the beaches on Earth Answer: E 20) Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case A) we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2.

B) we can't say anything about these galaxies except for their distances.

C) we are seeing Galaxy 1 as it looked at a later time in the history of the universe than Galaxy 2.

Answer: A

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21) The distance of Mars from the Sun is about 1.5 AU. How far is this in kilometers? (You do not need a calculator to answer this question. You do need to know what an AU is, within a factor of 1000.)

A) 1.5 150,000,000 km B) 1.5 150,000 km C) 150,000,000,000 / 1.5 km D) 150,000,000 / 1.5 km E) 1.5 150,000,000,000 km Answer: A Section 1.2 1) Shortly after the Big Bang, the chemical composition of the universe was A) almost entirely hydrogen and helium.

B) hydrogen only.

C) about equal amounts of all the elements.

D) about the same as it is today.

Answer: A 2) About what percentage of the original hydrogen and helium of the universe had been converted into heavier elements by the time our solar system was born?

A) 20% B) 10% C) 50% D) 2% Answer: D 3) What is nuclear fusion?

A) an explosion caused by putting together two volatile chemicals B) the process of splitting nuclei to produce energy C) the process of turning matter into pure energy D) the process of combining lightweight nuclei to make heavier nuclei E) a process that only occurs in bombs Answer: D 4) Earth is made mostly of metals and rocks. Where did most of the elements that make up these materials (carbon, silicon, iron, etc.) form?

A) They were produced by the Big Bang.

B) They were produced by chemical reactions in interstellar gas clouds.

C) They were produced by stars.

D) They were produced in our Sun. E) They were produced by nuclear fission of uranium and other radioactive materials in space.

Answer: C

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5) Why did Carl Sagan say that we are star stuff?

A) The composition of most stars (mostly hydrogen and helium) is about the same as the composition of our bodies.

B) Cosmic rays reaching Earth from distant astronomical sources may be one source of mutations that help evolution along.

C) Nearly every atom from which we are made once (before the solar system formed) was inside of a star.

D) Nearly every atom from which we are made was once inside our star, the Sun. E) Sagan thought that all of us have the potential to be movie (or TV) stars like he was.

Answer: C 6) The Sun is made primarily of A) hydrogen and oxygen.

B) hydrogen and helium.

C) carbon and nitrogen.

D) oxygen and carbon.

E) nearly equal portions of all the elements.

Answer: B 7) Our Sun formed ________ our galaxy formed.

A) before B) at the same time that C) billions of years after D) within about 10 million years after Answer: C 8) In what sense are galaxies cosmic recycling plants?

A) Every time one star dies, a new one of exactly the same size and mass is born.

B) As a galaxy rotates, its stars cycle around the galaxy center again and again, each time returning to exactly where they started.

C) New stars in galaxies form from gas that has been ejected by previous generations of stars.

D) New galaxies are continuously being formed from the remains of older galaxies.

Answer: C 9) On the scale of the cosmic calendar, in which the history of the universe is compressed to 1 year, when did the Sun and Earth form?

A) January B) December C) September D) February Answer: C

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10) On the scale of the cosmic calendar, in which the history of the universe is compressed to 1 year, how long has human civilization (i.e., since ancient Egypt) existed? A) about half the year B) about a month C) a few hours D) a few seconds E) less than a millionth of a second Answer: D 11) On the scale of the cosmic calendar, in which the history of the universe is compressed into 1 year, when did the dinosaurs become extinct? A) in late December B) in late November C) in late October D) in late September E) in late August Answer: A 12) On the scale of the cosmic calendar, in which the history of the universe is compressed into 1 year, when did Kepler and Galileo first discover that we live on a planet in a solar system? A) 1 second ago B) 1 day ago C) 1 week ago D) December 25 E) December 30 Answer: A 13) On the scale of the cosmic calendar, in which the history of the universe is compressed into 1 year, how long is the average human life span? A) 0.2 millisecond B) 0.2 second C) 2 seconds D) 2 minutes E) 2 hours Answer: B 14) Your textbook discusses the cosmic calendar, a model of the history of the universe scaled to a single year. The length of time represented by one month on this cosmic calendar is therefore closest to A) 1 billion years. B) 1 1000 years. C) 10 million years. D) 10 billion years. E) 1 million years. Answer: A

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15) What made most of the oxygen nuclei in the solar system?

A) stars B) Nothing makes elements–oxygen has always been present in the universe.

C) the Big Bang D) our Sun E) high energy collisions of dust and cosmic rays Answer: A Section 1.3 1) Approximately how fast is a person located at the Earth's equator moving around Earth's axis due to the rotation of the Earth?

A) 17,000 km/hr B) 1700 km/hr C) 170 km/hr D) 17 km/hr E) not moving at all Answer: B 2) Earth's rotation causes a person at the North Pole to ________ relative to the center of the Earth.

A) move at a speed of about 1670 km/hr B) spin in place once each year C) remain completely stationary D) spin in place once each day Answer: D 3) The ecliptic plane is A) the plane of Earth's orbit around the Sun. B) the plane of the Moon's orbit around Earth.

C) the plane of our solar system's orbit around the Milky Way Galaxy.

D) a flat disk of material that lies between the Sun and Earth.

E) the plane defined by Earth's equator.

Answer: B 4) We say that Earth has an axis tilt of 23-1/2° because this is the angle between Earth's A) rotation axis and a line perpendicular (vertical) to the ecliptic plane.

B) rotation axis and the star Polaris.

C) equator and rotation axis.

D) rotation axis and north pole.

E) rotation axis and magnetic axis.

Answer: A

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5) Patterns of stars in constellations hardly change in appearance over times of even a few thousand years. Why? A) Stars are fixed and never move. B) Stars move, but they move very slowly–only a few kilometers in a thousand years. C) Although most stars move through the sky, the brightest stars do not, and these are the ones that trace the patterns we see in the constellations. D) The stars in our sky actually move rapidly relative to us– thousands of kilometers per hour– but are so far away that it takes a long time for this motion to make a noticeable change in the patterns in the sky. E) Stars within a constellation move together as a group, which tends to hide their actual motion and prevent the pattern from changing. Answer: D 6) About how long does it take our solar system to complete one orbit around the center of the Milky Way Galaxy?

A) 10,000 years B) 1 million years C) 230 million years D) 4-1/2 billion years E) 14 billion years Answer: C

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7) Which of the following correctly lists the described speeds from slowest to fastest?

A) Earth's orbital speed about the Sun Earth's speed of rotation on its axis Earth's orbital speed about the Sun typical speeds of stars in the local solar neighborhood relative to us the speed of our solar system orbiting the center of the Milky Way Galaxy the speeds of very distant galaxies relative to us B) typical speeds of stars in the local solar neighborhood relative to us Earth's speed of rotation on its axis Earth's orbital speed about the Sun the speed of our solar system orbiting the center of the Milky Way Galaxy the speeds of very distant galaxies relative to us C) Earth's speed of rotation on its axis Earth's orbital speed about the Sun the speed of our solar system orbiting the center of the Milky Way Galaxy the speeds of very distant galaxies relative to us typical speeds of stars in the local solar neighborhood relative to us D) Earth's orbital speed about the Sun the speeds of very distant galaxies relative to us Earth's speed of rotation on its axis typical speeds of stars in the local solar neighborhood relative to us the speed of our solar system orbiting the center of the Milky Way Galaxy E) typical speeds of stars in the local solar neighborhood relative to us the speed of our solar system orbiting the center of the Milky Way Galaxy Earth's orbital speed about the Sun the speeds of very distant galaxies relative to us Earth's speed of rotation on its axis Answer: A 8) What evidence leads astronomers to conclude that most of the Milky Way's mass consists of a mysterious dark matter?

A) We observe many dark clouds of gas that block the light of stars behind them.

B) The galaxy's rotation indicates that it must contain much more matter than we can observe with our telescopes.

C) Observations indicate that most stars are dimmer than the Sun, so we say they are "dark."

D) Stars are separated from one another by vast distances, and therefore most places in the galaxy would be dark to our eyes.

Answer: B 9) Most of the mass in the Milky Way Galaxy is located A) in the halo (above/below the disk).

B) within the disk.

C) in the stars in the spiral arms.

D) in the gas and dust.

E) in the central bulge of the galaxy.

Answer: A

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10) The amount and distribution of matter in the Milky Way Galaxy is determined by A) counting the number of stars in the galaxy.

B) determining the amount of gas and dust in the galaxy.

C) studying where stars are located in the Milky Way. D) studying the rotation of the galaxy.

E) adding together the mass of the galaxy's stars and gas.

Answer: D 11) What evidence leads astronomers to conclude that the universe contains a mysterious dark energy?

A) The expansion of the universe is accelerating with time.

B) The gravity of distant galaxies is stronger than that of galaxies nearby.

C) Studies of galactic motion indicate that there is more matter in the universe than we can account for with stars and gas.

D) Stars shine much more brightly than we would expect from nuclear fusion.

E) The existence of such dark energy is the only way to account for evil in the universe.

Answer: A 12) From the fact that virtually every galaxy is moving away from us and more distant galaxies are moving away from us at a faster rate than closer ones, we conclude that A) the Milky Way Galaxy is expanding.

B) we are located at the center of the universe.

C) even nearby galaxies will eventually be moving faster than the speed of light.

D) the universe is expanding.

E) the universe is shrinking.

Answer: D 13) What do astronomers mean when they say the universe is expanding?

A) Everything in the universe is gradually growing in size.

B) Average distances are increasing between most galaxies.

C) Average distances are increasing between most stars.

D) The universe is expanding from a single point.

Answer: B 14) By studying distant galaxies in the 1920s, Hubble made the following important discovery that led us to conclude that the universe is expanding.

A) All galaxies contain billions of stars, and all galaxies have spiral shapes.

B) All galaxies were born at the same time, and all will die at the same time.

C) All galaxies outside the Local Group are moving away from us, and the farther away they are, the faster they're going.

D) All galaxies outside the Local Group are orbiting the Local Group.

E) Galaxies are in motion throughout the universe, with about equal numbers moving toward us and away from us.

Answer: C

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15) Imagine that we put a raisin cake into the oven, with each raisin separated from the others by 1 cm. An hour later, we take it out and the distances between raisins are 3 cm. If you lived in one of the raisins and watched the other raisins as the cake expanded, which of the following would you observe? A) All raisins would be moving away from you at the same speed. B) More distant raisins would be moving away from you faster. C) More distant raisins would be moving away from you more slowly. D) It depends: If you lived in a raisin near the edge of the cake, you'd see other raisins moving away from you, but they'd be coming toward you if you lived in a raisin near the center of the cake. E) The raisins would be expanding too, so you'd never notice any changes in the cake. Answer: B 16) Recall the raisin cake model of the universe and its analogy to our expanding universe.

Suppose away fromyou measure the recession velocity (the speed at which any object is moving us) of Galaxy A to be 2000 km/s and the recession velocity of Galaxy B to be 6000 km/s.

What can you conclude about the relative distances of these two galaxies?

A) Galaxy A is 3 times as far from us as Galaxy B. B) Galaxy B is 3 times as far from us as Galaxy A. C) Galaxy A is 6 times as far from us as Galaxy B. D) Galaxy B is 6 times as far from us as Galaxy A. E) The relative distances cannot be determined from the information in this problem.

Answer: B 17) The reason that we observe more distant galaxies to be moving away from us at higher speeds than nearby galaxies is that A) the more distant galaxies were flung outward faster by the Big Bang.

B) the more distant galaxies are smaller and less massive, so they can move faster.

C) the nearby galaxies are slowed by our own galaxy's gravitational pull.

D) there is more space to expand between us and the distant galaxies.

Answer: D 18) How do scientists estimate the age of the universe?

A) They look up the answer in a book or they Google it.

B) They measure the abundances of radioactive elements in meteorites, and use their halflives to calculate the age of the meteorites, which are the oldest solids in the solar system.

C) They measure the speeds and distances of galaxies, and calculate the time it took for them to travel that distance (away from us).

D) They make a guess: no one really knows how old the universe is.

E) They measure how fast the Sun is losing energy, and how much energy it has left to lose.

Answer: C

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19) According to astronomers, approximately how old is the universe?

A) 14 billion years B) 14 trillion years C) infinite D) 14 million years Answer: A 20) According to current scientific estimates, when did the Big Bang occur?

A) about 4.5 billion years ago B) about 20 billion years ago C) about 65 million years ago D) about 14 billion years ago E) about 10 billion years ago Answer: D 21) We observe that most galaxies are moving away from us. If we could (somehow) communicate with an observer in a distant galaxy, what would that observer say about what it sees?

A) Most galaxies are moving away from me, except for yours.

B) Most galaxies are moving away from me, including yours.

C) Most galaxies are moving away from you, and about half are moving towards me.

Answer: B Section 1.4 1) Which scientists played a major role in overturning the ancient idea of an Earth-centered universe, and about when?

A) Copernicus, Kepler, and Galileo; about 400 years ago B) Aristotle and Copernicus; about 400 years ago C) Newton and Einstein; about 100 years ago D) Huygens and Newton; about 300 years ago E) Aristotle and Plato; about 2000 years ago Answer: A General Chapter Questions 1) One light-year is the distance light travels in one year. The speed of light is about 300,000 km/s (3 × 105 km/s). How far is 1 light-year?

A) 3 × 105 km B) 1.8 × 107 km C) 1.08 × 109 km D) 9.46 × 1012 km Answer: D

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2) Light travels at a speed of 300,000 km/s. About how far is a light-year?

A) 10 million meters B) 10 billion km C) 300,000 km D) 10 million km E) 10 trillion km Answer: E 3) Consider how the Moon moves through the Solar System and complete the following sentence. The Moon orbits the Sun A) once a month.

B) once a year.

C) once a day.

Answer: B 4) Suppose you know the speed of a spacecraft in kilometers per second. How would you calculate its speed in kilometers per hour?

A) Multiply by 60 and then multiply by 60 again.

B) Divide by 60 and then divide by 60 again.

C) Multiply by 24.

D) Divide by 24.

Answer: B 5) How many seconds are in one year? (Calculate this, do not look it up.)

A) about 380 million (380,000,000, or 3.8 × 108) B) about 30 million (30,000,000, or 3 × 107) C) about 86 thousand (86,000, or 8.6 × 105) D) about 3600 (3.6 × 103) Answer: B 6) One light-hour is the distance light travels in one hour. The speed of light is about 300,000 km/s (3 × 105 km/s). If Jupiter is 0.72 light hours from the Sun, how far is this?

A) 216 thousand km (2.16 × 105 km) B) 13 million km (1.3 × 107 km) C) 778 million km (7.78 × 108 km) D) 1.5 billion km (1.5 × 109 km) Answer: C 7) The planet Mars is, on average, about 228 million km from the Sun. How long does it take light from the Sun to reach Mars? (Recall that the speed of light is about 300,000 km/s.)

A) about 8.4 minutes B) about 12.7 minutes C) about 1.52 light seconds D) about 1.52 hours Answer: B

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8) The Earth has a radius of about 6000 km. How long would it take for an object traveling at the speed of light to circle the Earth? (Recall that the speed of light is 300,000 km/s.) A) 1/300,000 of a second (0.0000033 s) B) 1/6000 of a second (0.000017 s) C) 1/8 of a second (0.0125 s) D) 1/2 of a second (0.5 s) Answer: C 9) Our solar system is located about 27,000 light-years from the galactic center. About how far does our solar system travel in one orbit? A) 54,000 light-years B) 85,000 light-years C) 100,000 light-years D) 170,000 light-years Answer: D 10) Astronomer Alan says the universe is expanding at one rate and Astronomer Wendy says it is expanding at a faster rate. All other things being equal, which astronomer would say that the universe is older? A) Wendy B) Alan C) neither Answer: B 11) Astronomers have used observations from the Hubble Space Telescope to measure the rate at which the universe is expanding, and have estimated the age of the universe from that measured rate. Suppose the expansion turns out to be faster than current measurements indicate. In that case, our new estimate for the age of the universe would be A) unaffected. B) younger (less time between now and the Big Bang). C) older (more time between now and the Big Bang). Answer: B 12) You observe two distant galaxies (well outside our Local Group of galaxies). You find that Galaxy W is moving away from us at a speed of 35,000 km/s and Galaxy X is moving away from us at a speed of 70,000 km/s. What can you say about the distances to those galaxies? A) Galaxy W is four times as far as Galaxy X. B) Galaxy W is twice as far as Galaxy X. C) She can't say anything about the distances to Galaxy W or X. D) Galaxy X is four times as far as Galaxy W. E) Galaxy X is twice as far as Galaxy W. Answer: B

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Short Answer Questions 1) The speed of light is 300,000 km/s. How far is a light-year? Be sure to show all work clearly on your calculations.

Answer: 1 light-year = (speed of light) × (1 yr) = × = 9,460,000,000,000 km 2) Earth's actual diameter is about 12,800 kilometers. What is Earth's diameter in a 1-to-10 billion scale model solar system? Show your work clearly.

Answer: Scaled radius of Earth = actual radius/1010 = 6,378 km/1010 = 6,378 × 105 cm/1010 = 6.378 × 108 cm/1010 = 6.378 × 10−2 cm = 0.6 mm This is about the size of the tip of a (fine tip) ballpoint pen.

Reading Quiz Questions 1) Which of the following is a general difference between a planet and a star?

A) Stars shine with energy released by nuclear fusion while planets shine primarily with light reflected from stars.

B) Stars are found in galaxies, but planets are not part of galaxies.

C) Stars are made of gas and planets are made of rock.

D) Stars are stationary while planets orbit stars.

Answer: A 2) Our solar system consists of A) the Sun and all the objects that orbit it.

B) the Sun and the planets, and nothing else.

C) a few hundred billion stars, bound together by gravity.

D) the Sun and several nearby stars, as well as the planets and other objects that orbit these stars.

Answer: A 3) A typical galaxy is a A) collection of millions or billions of stars, bound together by gravity and orbiting a common center.

B) large, glowing ball of gas powered by nuclear energy.

C) nearby object orbiting a planet.

D) relatively small, icy object orbiting a star.

E) system consisting of one or a few stars orbited by planets, moons, and smaller objects.

Answer: A

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4) Which of the following best describes what we mean by the term universe?

A) the sum total of all matter and energy B) a vast collection of stars that number as many as the grains of sand on all the beaches on Earth C) all the galaxies in all the superclusters D) our Milky Way Galaxy Answer: A 5) An astronomical unit (AU) is A) any very large unit, such as a light-year.

B) the average distance between Earth and the Sun. C) the current distance between Earth and the Sun. D) the average distance between any planet and the Sun. Answer: B 6) A light-year is A) about 10 trillion kilometers.

B) the time it takes light to reach the nearest star.

C) the time it takes light to travel around the Sun. D) about 300,000 kilometers per second.

Answer: A 7) A television advertisement claiming that a product is light-years ahead of its time does not make sense because A) it doesn't specify the number of light-years.

B) it uses "light-years" to talk about time, but a light-year is a unit of distance.

C) a light-year is an astronomically large unit, so a product could not possibly be so advanced.

D) light-years can only be used to talk about light.

Answer: B 8) The term observable universe refers to A) the portion of the universe that we have so far photographed through telescopes.

B) the portion of the universe that can be seen by the naked eye.

C) the portion of the universe that is not hidden from view by, for example, being below the horizon.

D) the portion of the universe that we can see in principle, given the current age of the universe.

Answer: D 9) On a scale where the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is A) small enough to fit within your hand.

B) about 1 meter.

C) about 5 meters.

D) about 30 meters.

Answer: A

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10) On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun? A) 100 meters B) about the distance across 50 football fields C) about the distance across the state of Delaware D) about the distance across the United States Answer: D 11) The number of stars in the Milky Way Galaxy is approximately A) a few hundred.

B) a few hundred thousand.

C) a few hundred billion.

D) a few hundred million.

Answer: C 12) What do astronomers mean by the Big Bang?

A) the event that marked the beginning of the expansion of the universe B) a gigantic explosion that blew all the galaxies in the universe to smithereens C) the explosion of a massive star at the end of its life D) the event that marked the birth of our solar system Answer: A 13) What do we mean when we say that the universe is expanding?

A) Everything in the universe is gradually growing in size.

B) Within galaxies, average distances between star systems are increasing with time.

C) The statement is not meant to be literal; rather, it means that our knowledge of the universe is growing.

D) Average distances between galaxies are increasing with time.

Answer: D 14) Based on observations of the universal expansion, the age of the universe is about A) 14,000 years B) 14 million years C) 14 billion years D) 14 trillion years Answer: C 15) If the 14 billion year history of the universe were compressed to one year, and "now" is exactly midnight December 31, approximately how long ago were your grandparents born?

A) 0.15 second ago B) 1 second ago C) 1 minute ago D) 1 hour ago Answer: C

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16) What is the ecliptic plane? A) the plane of Earth's orbit around the Sun B) the plane of Earth's equator C) the plane of the Sun's equator D) the plane of the Milky Way Galaxy Answer: A 17) How long does it take the Earth to complete one orbit around the Sun? A) one year B) one day C) one month D) one week E) The time it takes Earth to orbit the Sun changes significantly from one orbit to the next. Answer: A 18) What is the "raisin cake analogy" to the expanding universe intended to explain? A) That as a raisin cake expands, every raisin moves away from every other raisin, just as galaxies move away from each other in an expanding universe. B) That raisins, like galaxies, expand in size as the cake or universe expands. C) That from within the raisin cake, you would see other raisins moving away from you only if you were on the central raisin, just as you see galaxies moving away only if you are in the center of the universe. D) That the universe heats up as it expands, just as the raisin cake heats up as it bakes. Answer: A Concept Quiz Questions 1) Which of the following has your "cosmic address" in the correct order? A) you, Earth, solar system, Local Group, Local Supercluster, Milky Way Galaxy, universe B) you, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe C) you, Earth, Local Group, Local Supercluster, solar system, Milky Way Galaxy, universe D) you, Earth, solar system, Local Group, Milky Way Galaxy, Local Supercluster, universe E) you, Earth, Milky Way Galaxy, solar system, Local Group, Local Supercluster, universe Answer: B 2) When we look at an object that is 1,000 light-years away we see it A) as it was 1,000 years ago. B) as it was 1,000 light-years ago. C) as it is right now, but it appears 1,000 times dimmer. D) looking just the same as our ancestors would have seen it 1,000 years ago. Answer: A

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3) Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case A) Galaxy 1 must be twice as big as Galaxy 2.

B) we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2.

C) we are seeing Galaxy 1 as it looked at a later time in the history of the universe than Galaxy 2.

D) Galaxy 2 must be twice as old as Galaxy 1.

Answer: B 4) Could we see a galaxy that is 20 billion light-years away? (Assume that we mean a "lookback time" of 20 billion years.)

A) no, because it would be beyond the bounds of our observable universe B) yes, if we had a big enough telescope C) no, because a galaxy could not possibly be that far away D) Yes, we have already detected galaxies at that distance.

Answer: A 5) Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit.

Which of the following best describes what the planets would look like?

A) The planets are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the rest planets are spread much farther apart.

B) The planets are all much smaller than the Sun and are spread out evenly over a distance about the length of a large classroom.

C) The planets are all much smaller than the Sun. Four planets are located within a few centimeters of the Sun, and four planets are located at distances ranging up to about a meter.

D) The planets range in size from about the size of a marble to the size of a baseball. They are spread out over a region about the size of a football field.

Answer: A 6) If you could count stars at a rate of about one per second, how long would it take to count all the stars in the Milky Way Galaxy?

A) several days B) several weeks C) several years D) several thousand years Answer: D 7) The total number of stars in the observable universe is about A) 100 billion.

B) the same as the number of grains of sand in a school sandbox.

C) the same as the number of grains of sand on all the beaches on Earth.

D) the same as the number of atoms that make up the Earth.

Answer: C

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8) Using the ideas discussed in your text, in what sense are we "star stuff"? A) The overall chemical composition of our bodies is about the same as that of stars. B) Movie stars and other people are all made of the same stuff, so we all have the potential to be famous. C) Nearly every atom from which we are made was once inside of a star. D) We could not survive without light from our star, the Sun. Answer: C 9) How are galaxies important to our existence? A) Without galaxies, there could not have been a Big Bang. B) Without galaxies, the universe could not be expanding. C) Deep in their centers, galaxies created the elements from which we are made. D) Galaxies recycle material from one generation of stars to the next, and without this recycling, we could not exist. Answer: D 10) If we imagine the history of the universe compressed into one year, with the present as the stroke of midnight at the very end of that year, dinosaurs became extinct A) about 6 months ago. B) about 3 weeks ago. C) yesterday morning. D) about an hour ago. Answer: C 11) Relative to the age of the universe, how old is our solar system? A) It is about 1% as old as the universe. B) It is between about 5 and 10% as old as the universe. C) It is about one third the age of the universe. D) It is nearly the same age as the universe. Answer: C 12) How do the speeds at which we are moving with Earth's rotation and orbit compare to the speeds of more familiar objects? A) Earth's rotation carries most people around the axis faster than a commercial jet travels, and Earth's orbit carries us around the Sun faster than the Space Station orbits Earth. B) Earth's rotation carries most people around the axis at about the speed of a commercial jet, and Earth's orbit carries us around the Sun at about the speed of a military jet. C) Earth's rotation carries most people around the axis at about the speed of a car on the freeway, and Earth's orbit carries us around the Sun at about the speed of a commercial jet. D) Earth's rotation carries most people around the axis at about the speed at which the Space Station orbits Earth, and Earth's orbit carries us around the Sun at nearly the speed of light. Answer: A

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13) Why do the patterns of the stars in our sky look the same from year to year? A) because the stars in the constellations are so far away B) because the stars in the constellations are not moving C) because the stars in the constellations all move at the same speeds and in the same directions, so they don't change their relative positions D) because the stars in the constellations typically move so slowly – typically about the speed of a snail – that their motions are not noticeable Answer: A 14) Where is our solar system located within the Milky Way Galaxy? A) very near the center of the galaxy B) at the far edge of the galaxy's visible disk C) roughly halfway between the center and the edge of the visible disk of the galaxy D) in the halo of the galaxy Answer: C 15) Consider a raisin cake expanding uniformly in an oven. Viewed from one of the raisins, you would see A) all other raisins moving away from you, with more distant raisins moving faster. B) all other raisins moving away from you, with more distant raisins moving slower. C) all other raisins moving away from you at the same speed. D) all raisins, including your own, growing in size as the cake expands. Answer: A 16) Astronomers infer that the universe is expanding because distant galaxies all appear to A) be growing in size. B) be moving away from us, with more distant ones moving faster. C) be made mostly of dark matter. D) rotate rapidly. Answer: B 17) Which statement about motion in the universe is not true? A) The mysterious dark matter is the fastest-moving material in the universe. B) Some stars in the Milky Way Galaxy are moving toward us and others are moving away from us. C) Except for a few nearby galaxies, all other galaxies are moving away from us. D) Your speed of rotation around Earth's axis is faster if you live near the equator than if you live near the North Pole.

Answer: A 18) When did humans learn that the Earth is not the center of the universe? A) within the past 500 years B) about 2,500 years ago C) about 1,000 years ago D) We haven't; there is still considerable scientific debate about whether Earth is the center of the universe. Answer: A

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Visual Quiz Questions 1) Each box in this figure represents a different level of structure in our universe. Each box is labeled with one of the numbers 1—5. Which box represents the Milky Way Galaxy?

A) 1 B) 2 C) 3 D) 4 E) 5 Answer: C

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2) What does this photograph show?

A) It is a picture of our own Milky Way Galaxy.

B) It is a picture of the Andromeda galaxy, located about 2.5 million light-years away.

C) It is a picture of a cloud of gas known as the Orion Nebula.

D) It is a picture of our own solar system.

E) It is a picture of a young star in the process of being born.

Answer: B 3) This painting represents the Sun and planets (and two dwarf planets) of our solar system.

What is not to scale in this painting?

A) The sizes of the planets are not correctly scaled compared to each other or the Sun. B) The distances between the planets are not shown to scale.

C) The Sun is too big compare to the planets.

D) Everything is correctly scaled, but the planets are shown in the wrong order from the Sun. E) Neither distances nor sizes are correctly scaled.

Answer: B 4) What is the significance of this photograph?

A) It shows the first person ever to land on Mars.

B) It shows a person standing on the most distant world ever visited by a human being.

C) It shows the first person ever to go into space.

D) It was taken Jan. 1, 2000, to commemorate the turn of the millennium.

Answer: B

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5) Suppose we made a scale model of our Milky Way Galaxy in which the disk of the galaxy is the size of a football field. Which (if any) diagram represents the Sun on the same scale?

A)

B) C) D) The Sun on this scale would be about two feet in diameter and too big to show on the screen.

E) The Sun on this scale would be microscopic and too small to see on the screen.

Answer: E 6) These photos show two different astronomical objects. Which object is bigger, and by about how much?

A) Object 2 is more than a trillion times as large as Object 1. B) Object 2 is approximately 1,000 times as large as Object 1. C) Object 2 is about 10 times as large as Object 1. D) Object 1 is about 10 times as large as Object 2. E) Both objects are about the same size. Answer: A

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7) This diagram represents Earth's rotation and orbit. What do we call the flat blue plane shown in this diagram?

A) the solar plane B) the ecliptic plane C) Earth's axis D) the galactic plane E) an astronomical unit Answer: B 8) Notice that Earth's axis is shown with an arrowhead in this diagram. What does the arrow point to?

A) the Sun B) the ecliptic plane C) the center of the Milky Way Galaxy D) Polaris, the North Star E) the Northern lights Answer: D

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9) These diagrams show a raisin cake before it is put in the oven and again one hour later after it has expanded during baking. Suppose you lived in Raisin 3 (the raisin labeled "3").

What would you have noticed about Raisin 2 during baking?

A) Raisin 2 is moving away from you at a speed of 4 cm/hr.

B) Raisin 2 always stays in the same place but gets bigger in size.

C) Raisin 2 is moving away from you at a speed of 2 cm/hr.

D) Raisin 2 is moving away from you at a speed of 6 cm/hr.

E) Raisin 2 is moving toward you at a speed of 2 cm/hr.

Answer: C 10) Nearly all of the objects that you can see in this photograph are

A) planets.

B) stars.

C) galaxies.

D) astronomical units.

Answer: C

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

The figure above shows the sizes of Earth and the Moon to scale; the scale used is 1 cm = 4000 km.

Using what you've learned about astronomical scale in this chapter, answer the following questions. Hint: If you are unsure of the answers, you can calculate them using the data given above.

1) If you wanted to show the distancebetween Earth and the Moon on the same scale, about how far apart would you need to place the two photos?

A) 10 centimeters (about the width of your hand) B) 1 meter (about the length of your arm) C) 100 meters (about the length of a football field) D) 1 kilometer (a little more than a half mile) Answer: B 2) Suppose you wanted to show the Sun on the same scale. About how big would it need to be?

A) 3.5 centimeters in diameter (the size of a golf ball) B) 35 centimeters in diameter (a little bigger than a basketball) C) 3.5 meters in diameter (about 11-1/2 feet across) D) 3.5 kilometers in diameter (the size of a small town) Answer: C

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3) About how far away from Earth would the Sun be located on this scale?

A) 3.75 meters (about 12 feet) B) 37.5 meters (about the height of a 12-story building) C) 375 meters (about the length of four football fields) D) 37.5 kilometers (the size of a large city) Answer: C 4) Could you use the same scale to represent the distances to nearby stars? Why or why not?

Answer: No. The nearest stars would not fit on Earth using this scale. The total distance to the nearest star would wrap around the Earth about 2.5 times!

Chapter Review Questions 1) Briefly describe the major levels of structure (such as planet, star, galaxy) in the universe.

2) Define astronomical unit and light-year.

3) Explain the statement "The farther away we look in distance, the further back we look in time."

4) What do we mean by the observable universe? Is it the same thing as the entire universe?

5) Using techniques described in the chapter, put the following into perspective: the size of our solar system; the distance to nearby stars; the size and number of stars in the Milky Way Galaxy; the number of stars in the observable universe.

6) What do we mean when we say that the universe is expanding, and how does expansion lead to the idea of the Big Bang and our current estimate of the age of the universe?

7) In what sense are we "star stuff"?

8) Use the cosmic calendar to describe how the human race fits into the scale of time.

9) Briefly explain Earth's daily rotation and annual orbit, defining the terms ecliptic plane and axis tilt.

10) Briefly describe our solar system's location and motion within the Milky Way Galaxy.

11) Why do scientists suspect that most of our galaxy's mass consists of dark matter? Briefly describe the mystery of dark matter and dark energy.

12) What key observations lead us to conclude that the universe is expanding? Use the raisin cake model to explain how these observations imply expansion.

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Does It Make Sense?

Decide whether or not each of the following statements makes sense (or is clearly true or false).

Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.

Example: I walked east from our base camp at the North Pole.

Solution: The statement does not make sense because east has no meaning at the North Pole–all directions are south from the North Pole.

13) Our solar system is bigger than some galaxies.

14) The universe is billions of light-years in age.

15) It will take me light-years to complete this homework assignment!

16) Someday we may build spaceships capable of traveling a light-year in only a decade.

17) Astronomers recently discovered a moon that does not orbit a planet.

18) NASA will soon launch a spaceship that will photograph our Milky Way Galaxy from beyond its halo.

19) The observable universe is larger today than it was a few billion years ago.

20) Photographs of distant galaxies show them as they were when they were much younger than they are today.

21) At a nearby park, I built a scale model of our solar system in which I used a basketball to represent Earth.

22) Because nearly all galaxies are moving away from us, we must be located near the center of the universe.

Quick Quiz 23) Which of the following correctly lists our "cosmic address" from small to large? A) Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe B) Earth, solar system, Local Group, Local Supercluster, Milky Way Galaxy, universe C) Earth, Milky Way Galaxy, solar system, Local Group, Local Supercluster, universe Answer: No Correct Answer Was Provided. 24) An astronomical unit is A) any planet's average distance from the Sun. B) Earth's average distance from the Sun. C) any large astronomical distance. Answer: No Correct Answer Was Provided.

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25) The star Betelgeuse is about 600 light-years away. If it explodes tonight A) we'll know because it will be brighter than the full Moon in the sky.

B) we'll know because debris from the explosion will rain down on us from space.

C) we won't know about it until about 600 years from now.

Answer: No Correct Answer Was Provided.

26) If we represent the solar system on a scale that allows us to walk from the Sun to Pluto in a few minutes, then A) the planets are the size of basketballs and the nearest stars are a few miles away.

B) the planets are marble-size or smaller and the nearest stars are thousands of miles away.

C) the planets are microscopic and the stars are light-years away.

Answer: No Correct Answer Was Provided.

27) The total number of stars in the observable universe is roughly equivalent to A) the number of grains of sand on all the beaches on Earth.

B) the number of grains of sand on Miami Beach.

C) infinity.

Answer: No Correct Answer Was Provided.

28) When we say the universe is expanding, we mean that A) everything in the universe is growing in size.

B) the average distance between galaxies is growing with time.

C) the universe is getting older.

Answer: No Correct Answer Was Provided.

29) If stars existed but galaxies did not A) we would probably still exist anyway.

B) we would not exist because life on Earth depends on the light of galaxies.

C) we would not exist because we are made of material that was recycled in galaxies.

Answer: No Correct Answer Was Provided.

30) Could we see a galaxy that is 50 billion light-years away?

A) yes, if we had a big enough telescope B) no, because it would be beyond the bounds of our observable universe C) no, because a galaxy could not possibly be that far away Answer: No Correct Answer Was Provided.

31) The age of our solar system is about A) one-third of the age of the universe.

B) three-fourths of the age of the universe.

C) two billion years less than the age of the universe.

Answer: No Correct Answer Was Provided.

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32) The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that A) the universe is expanding.

B) galaxies repel each other like magnets.

C) our galaxy lies near the center of the universe.

Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

33) Group Discussion: What does a scientist look like?

The purpose of this exercise is to help you identify preconceptions that you or others may have about science and scientists. a) Working independently, make a simple sketch of a professional scientist and write down five words that describe the scientist in your sketch. Then join with a group of two to three other students to share your sketches and word lists. b) Make a list of all the words the group wrote down, then rank them in order of how often they were used. c) Discuss any similarities, differences, or patterns you notice among the scientists described by the group members. d) Discuss whether you and the other members of your group feel as if you have much in common with professional scientists. e) Discuss how your beliefs about what you have (or do not have) in common with scientists might affect your approach to scientific thinking.

The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

34) Earth as a Planet.For most of human history, scholars assumed Earth was the center of the universe. Today, we know that our Sun is just one star in a vast universe. How did science make it possible for us to learn these facts about Earth?

35) Thinking About Scale. One key to success in science is finding simple ways to evaluate new ideas, and making a simple scale model is often helpful. Suppose someone tells you that the reason it is warmer during the day than at night is that the day side of Earth is closer to the Sun than the night side. Evaluate this idea by thinking about the size of Earth and its distance from the Sun in a scale model of the solar system.

36) Looking for Evidence. In this first chapter, we have discussed the scientific story of the universe but have not yet discussed most of the evidence that backs it up. Choose one idea presented in this chapter–such as the idea that there are billions of galaxies in the universe, or that the universe was born in the Big Bang, or that the galaxy contains more dark matter than ordinary matter–and briefly discuss the type of evidence you would want to see before accepting the idea. (Hint: It's okay to look ahead in the book to see the evidence presented in later chapters.)

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37) A Human Adventure. Astronomical discoveries clearly are important to science, but are they also important to our personal lives? Defend your opinion. 38) Infant Species. In the last few tenths of a second before midnight on December 31 of the cosmic calendar, we have developed an incredible civilization and learned a great deal about the universe, but we also have developed technology with which we could destroy ourselves. The midnight bell is striking, and the choice for the future is ours. How far into the next cosmic year do you think our civilization will survive? Defend your opinion.

39) Group Activity: Counting the Milky Way's Stars. Work as a group to answer each part.

Note: This activity works particularly well in groups of four students, with each student taking on one of the following roles: Scribe–takes notes on the group's activities; Proposer–suggests tentative explanations to the group; Skeptic–points out weaknesses in proposed explanations; Moderator– leads group discussion and makes sure everyone contributes. a) Work together to estimate the number of stars in the Milky Way from just these two facts: (1) the number of stars within 12 light-years of the Sun, which you can count in Appendix F; (2) the total volume of the Milky Way's disk (100,000 light-years in diameter and 1000 light-years thick), which is about 1 billion times the volume of the region of your star count. b) Discuss how your value from part a compares to the value given in this chapter. Make a list of possible reasons why your technique may have underestimated or overestimated the actual number.

Investigate Further 40) Alien Technology. Some people believe that Earth is regularly visited by aliens who travel here from other star systems. For this to be true, how much more advanced than our own technology would the alien space travel technology have to be? Write one to two paragraphs to give a sense of the technological difference. (Hint: The ideas of scale in this chapter can help you contrast the distance the aliens would have to travel with the distances we currently are capable of traveling.)

41) Raisin Cake Universe. Suppose that all the raisins in a cake are 1 centimeter apart before baking and 4 centimeters apart after baking. a) Draw diagrams to represent the cake before and after baking. b) Identify one raisin as the Local Raisin on your diagrams. Construct a table showing the distances and speeds of other raisins as seen from the Local Raisin. c) Briefly explain how your expanding cake is similar to the expansion of the universe.

42) Scaling the Local Group of Galaxies. Both the Milky Way Galaxy and the Andromeda Galaxy (M31) have a diameter of about 100,000 light-years. The distance between the two galaxies is about 2.5 million light-years. a) Using a scale on which 1 centimeter represents 100,000 light-years, draw a sketch showing both galaxies and the distance between them to scale. b) Howon does the separation between galaxies compare to the separation between stars?

Based your answer, discuss the likelihood of galactic collisions in comparison to the likelihood of stellar collisions.

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43) The Hubble eXtreme Deep Field. The photo that opens this chapter is called the Hubble eXtreme Deep Field. Find this photo on the Hubble Space Telescope website. Learn how it was taken, what it shows, and what we've learned from it. Write a short summary of your findings.

44) The Cosmic Perspective. Write a short essay describing how the ideas presented in this chapter affect your perspectives on your own life and on human civilization.

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

45) Distances by Light.Just as a light-year is the distance that light can travel in 1 year, we define a light-second as the distance that light can travel in 1 second, a light-minute as the distance that light can travel in 1 minute, and so on. Calculate the distance in both kilometers and miles represented by each of the following: a) 1 light-second. b) 1 light-minute. c) 1 light-hour. d) 1 light-day.

46) Spacecraft Communication. We use radio waves, which travel at the speed of light, to communicate with robotic spacecraft. How long does it take a message to travel from Earth to a spacecraft at a) Mars at its closest to Earth (about 56 million km)? b) Mars at its farthest from Earth (about 400 million km)? c) Pluto at its average distance from Earth (about 5.9 billion km)?

47) Saturn vs. the Milky Way. Photos of Saturn and photos of galaxies can look so similar that children often think the photos show similar objects. In reality, a galaxy is far larger than any planet. About how many times larger is the diameter of the Milky Way Galaxy than the diameter of Saturn's rings? (Data: Saturn's rings are about 270,000 km in diameter; the Milky Way is 100,000 light-years in diameter.)

48) Galaxy Scale. Consider the 1-to-1019 scale, on which the disk of the Milky Way Galaxy fits on a football field. On this scale, how far is it from the Sun to Alpha Centauri (real distance: 4.4 light-years)? How big is the Sun itself on this scale? Compare the Sun's size on this scale to the actual size of a typical atom (about 10−10 m in diameter).

49) Universal Scale. Suppose we wanted to make a scale model of the Local Group of galaxies in which the Milky Way Galaxy was the size of a marble (about 1 cm in diameter). a) How far from the Milky Way Galaxy would the Andromeda Galaxy be on this scale? b) How far would the Sun be from Alpha Centauri on this scale? c) How far would it be from the Milky Way Galaxy to the most distant galaxies in the observable universe on this scale?

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50) Driving Trips. Imagine that you could drive your car at a constant speed of 100 km/hr (62 mi/hr), even across oceans and in space. (In reality, the law of gravity would make driving through space at a constant speed all but impossible.) How long would it take to drive a) around Earth's equator? b) from the Sun to Earth? c) from the Sun to Pluto? d) to Alpha Centauri?

51) Faster Trip. Suppose you wanted to reach Alpha Centauri in 100 years. a) How fast would you have to go, in km/hr? b) How many times faster is the speed you found in part a than the speed of our fastest current spacecraft (around 50,000 km/hr)?

52) Galactic Rotation Speed. We are located about 27,000 light-years from the galactic center and we orbit the center about once every 230 million years. How fast are we traveling around the galaxy, in km/hr?

53) Earth Rotation Speed. Mathematical Insight 1.4 shows how to find Earth's equatorial rotation speed. To find the rotation speed at any other latitude, you need the following fact: The radial distance from Earth's axis at any latitude is equal to the equatorial radius times the cosine of the latitude. Use this fact to find the rotation speed at the following latitudes. (Hint: When using the cosine (cos) function, be sure your calculator is set to recognize angles in degree mode, not in radian or gradient mode.) a) 30°N b) 60°N c) your latitude 54) Order of Magnitude Estimate. Mathematical Insight 1.3 defines order of magnitude estimates, and in the text we estimated there are about 1022 stars in the observable universe by assuming that 100 billion large galaxies each have about 100 billion stars. Now, assume that there are also 1 trillion small galaxies, but that each has only 10 million stars on average. How will this affect the estimate of the total number of stars in the observable universe? Explain your answer without calculating.

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The Cosmic Perspective, 9e (Bennett et al.) Chapter 2 Discovering the Universe for Yourself Section 2.1 1) At midnight, on a clear and moonless night, the number of stars that are distinctly visible to the eye is in the range A) 2000-5000. B) 20,000-50,000. C) 200,000-500,000. D) 2 million-5 million. Answer: A 2) Which of the following best describes the modern definition of a constellation? A) a region of the celestial sphere B) a pattern of bright stars in the sky C) a Greek mythological figure D) a collection of stars that are near one another in space E) a group of stars that all lie at about the same distance from Earth Answer: A 3) While the historical definition of a constellation is "a pattern or figure of stars in the sky," the modern definition used by astronomers is A) a group of stars in the sky that are all very close to each other. B) a specifically named and bordered region of the celestial sphere. C) any grouping of very bright stars in our galaxy, often hosting a star cluster. D) no definition; astronomers no longer use the term constellation.

Answer: B 4) The number of official constellations (as defined by the International Astronomical Union) is A) 56. B) 88. C) 123. D) 205. Answer: B 5) The stars stay in "fixed" positions on the celestial sphere because they A) are all located at precisely the same distance from Earth. B) are so far away that our eyes don't notice their motions through space. C) remain stationary relative to our solar system in space. D) were given their names by ancient civilizations. Answer: B

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6) The celestial sphere is A) the central spherical region of the Milky Way Galaxy, dense with stars.

B) a spherical galaxy, centered on the Sun. C) a useful illusion used to map the stars and other objects in the sky.

D) the star-sphere discovered by the Greeks and other ancient civilizations which shows the physical location in space of the nearby stars.

E) another name for our spherical Sun. Answer: C 7) Which of the following statements about the celestial sphere is not true?

A) When we look in the sky, the stars all appear to be located on the celestial sphere.

B) Earth is placed at the center of the celestial sphere.

C) The celestial sphere does not exist physically.

D) The "celestial sphere" is just another name for our universe.

E) From any location on Earth, we can see only half the celestial sphere at any one time.

Answer: D 8) What is the ecliptic?

A) when the Moon passes in front of the Sun B) the Moon's apparent path along the celestial sphere C) the constellations commonly used in astrology to predict the future D) the Sun's daily path across the sky E) the Sun's apparent annual path around the celestial sphere Answer: E 9) What is the celestial equator?

A) another name for the ecliptic B) the path the Sun appears to trace through the constellations each year C) a projection of Earth's equator into space D) the technical name of the Sun's equator Answer: C 10) On the celestial sphere, the Sun A) circles once each year along the path called the ecliptic.

B) stays always at the same fixed point among the stars.

C) circles daily around the celestial equator.

D) is the central object.

Answer: A 11) Which of the following statements about the celestial equator is true at all latitudes?

A) It lies along the band of light we call the Milky Way. B) It represents an extension of Earth's equator onto the celestial sphere.

C) It cuts the dome of your sky exactly in half.

D) It extends from your horizon due east, through your zenith, to your horizon due west.

E) It extends from your horizon due north, through your zenith, to your horizon due south.

Answer: B

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12) What is the name of the path on the celestial sphere that goes through the constellations of the zodiac?

A) the celestial equator B) the ecliptic C) the Milky Way D) the meridian E) the horizon Answer: A 13) The "Milky Way" in the night sky looks like a blurry circle of light in the sky because A) we are seeing the stars and gas that lie in disk of our Milky Way Galaxy.

B) our Sun is located at the center of our galaxy.

C) the stars within this band of light are much farther away than other stars.

D) our rotating Earth blurs our view of stars in the Milky Way Galaxy.

Answer: A 14) When we look toward the constellation Sagittarius, we are looking A) at the galaxy's central bulge.

B) toward Polaris, the "Pole Star."

C) toward the Winter Triangle.

D) out toward the outer Milky Way. Answer: A 15) When we look into the band of light in our sky that we call the Milky Way, can we see distant galaxies? Why or why not? (Assume we are looking with visible light telescopes.)

A) Yes, distant galaxies appear as small, fuzzy patches of light within the Milky Way band.

B) yes, but only when we look in the direction of the constellation Sagittarius C) no, because the stars, gas, and dust of the Milky Way block our view of more distant objects D) no, because galaxies exist only above and below the plane of the Milky Way E) no, because distant galaxies are too dim to be seen even with powerful telescopes Answer: C 16) Which of the following correctly describes the meridian in your sky?

A) a half-circle extending from your horizon due east, through your zenith, to your horizon due west B) a half-circle extending from your horizon due north, through your zenith, to your horizon due south C) a half-circle extending from your horizon due east, through the north celestial pole, to your horizon due west D) the point directly over your head E) the boundary between the portion of the celestial sphere you can see at any moment and the portion that you cannot see Answer: B

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17) You experience night-time when A) the Moon blocks the Sun's light. B) Earth is on the opposite side of the celestial sphere from the Sun. C) you are located on the side of the Earth that faces away from the Sun. D) you are located on the side of the Earth that faces toward stars. Answer: C 18) If Earth's rotation slowed down so that it completed exactly one rotation about its axis in 100 hours (instead of 24), what would be the typical time interval between sunrise and sunset? A) 50 hours B) 100 hours C) 12 hours D) 25 hours E) 24 hours Answer: A 19) Why do we experience night and day on Earth? A) Earth rotates on its axis once every 24 hours. B) The Sun orbits Earth once every 24 hours. C) The Moon circles Earth once every 24 hours. D) The Sun moves around in a circle once every 24 hours, shining like a spotlight on Earth. Answer: A 20) Do all galaxies out beyond the Milky Way rise in the east and set in the west (if they aren't circumpolar)? A) Impossible to say for sure, since we haven't yet seen all of the galaxies in the universe. B) no C) yes Answer: C 21) We can describe the position of an object in our local sky by stating its A) altitude and meridian. B) altitude and direction. C) latitude and direction. D) latitude and longitude.

E) meridian and longitude. Answer: B 22) How many arcminutes are in 1°? A) 60 B) 360 C) 3600 D) 100 E) 10,000 Answer: A

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23) How many arcseconds are in 1 arcminute? A) 60 B) 360 C) 3600 D) 100 E) 10,000 Answer: A 24) How many arcseconds are in 1°? A) 60 B) 360 C) 3600 D) 100 E) 10,000 Answer: C 25) If you hold your fist at arm's length, you will see it spanning an angle of about A) 1 arcsecond. B) 1°. C) 10°. D) 45°. E) 90°. Answer: C 26) The angular sizes of the Sun and Moon are about the same because A) both objects have the same physical size. B) both objects are located the same distance away. C) the Sun is larger in size than the Moon by the same factor (about 400) that it is farther in distance. D) their angular sizes are an illusion created by the apparent locations on the celestial sphere.

Answer: C 27) Which of the following statements does not use the term angular size or angular distance correctly? A) The angular size of the Moon is about 1/2 degree. B) The angular distance between those two houses in the distance is 30°. C) The angular distance between those two bright stars in the sky is about 2 meters. D) The angular size of the Sun is about the same as that of the Moon. E) You can use your outstretched hand to estimate angular sizes and angular distances. Answer: C

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28) We can describe the location of a point on Earth's surface by stating its A) altitude and meridian. B) altitude and direction. C) latitude and direction. D) latitude and longitude. E) meridian and longitude. Answer: D 29) Is there any place on Earth where we can see stars rise in the west and set in the east (rather than rising in the east and setting in the west)? Why or why not? A) yes, in the Southern Hemisphere, because the sky appears backward there B) yes, on Earth's equator, because it is halfway between the poles C) no, because the rising and setting of stars is caused by Earth's west to east rotation D) no, because the stars that rise in the west and set in the east are too dim to be seen by the naked eye Answer: C 30) If it is midnight in New York, it is A) daytime in Sydney, Australia. B) midnight in Sydney, Australia. C) midnight in Los Angeles. D) midday in Rio de Janeiro, Brazil. E) midnight everywhere. Answer: A 31) What is a circumpolar star? A) a star that rises in the east and sets in the west B) a star that appears to circle from the north celestial pole to the south celestial pole C) a star that always remains above your horizon D) a star that appears to make a full circle around us each day E) a star that is visible from the North or South pole Answer: C 32) Which of the following statements about circumpolar stars is true at all latitudes? A) They are the stars close to the north celestial pole. B) They always remain above your horizon. C) They make relatively small circles, traveling clockwise around the north celestial pole. D) Like all other stars, they rise in the east and set in the west. E) You cannot see them from the Southern Hemisphere. Answer: B

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33) What makes the North Star, Polaris, special?

A) It is the brightest star in the sky.

B) It is the star straight overhead.

C) It appears very near the north celestial pole.

D) It is the star directly on your northern horizon.

E) It can be used to determine your longitude on Earth.

Answer: C 34) You are standing on Earth's equator. Which way is Polaris, the North star?

A) 30 degrees up, due West B) on the northern horizon C) directly overhead D) The answer depends on whether it's winter or summer.

E) The answer depends on what time of day (or night) it is.

Answer: B 35) By locating the north celestial pole (NCP) in the sky, how can you determine your latitude?

A) The altitude of the NCP is the same as your latitude.

B) The altitude of the NCP is your angular distance from the North Pole.

C) The azimuth of the NCP is the same as your latitude.

D) The azimuth of the NCP is the angular distance from the North Pole.

E) The altitude of the NCP is the same as your distance from the North Pole.

Answer: A 36) If you locate the north celestial pole in your local sky and measure its altitude, then you will know A) your latitude and longitude.

B) your latitude and the direction that is due north for you.

C) your longitude and the direction that is due north for you.

D) your latitude and the local time.

E) your latitude, longitude, and local time.

Answer: B 37) If you see Polaris directly overhead, you must be very close to A) the equator.

B) the South Pole.

C) the Tropic of Cancer.

D) the North Pole.

Answer: D 38) You are standing at the North Pole. Which way is Polaris, the North star?

A) The answer depends on what time of day (or night) it is.

B) The answer depends on whether it's winter or summer.

C) directly overhead D) 30 degrees up, due West E) on the northern horizon Answer: C

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39) The constellation Orion is visible on winter evenings but not on summer evenings because of A) blockage by the full moon. B) the tilt of Earth's rotation axis. C) the location of Earth in its orbit around the Sun. D) the precession of Earth's rotation axis. Answer: C 40) Looking through your telescope tonight, you observe a distant galaxy called RXJ1800 and notice that it is very near in the sky to the bright star Vega. What can you conclude from this observation? A) RXJ1800 and Vega will both set in the west at about the same time. B) Vega orbits the center of mass of RXJ1800. C) Vega and RXJ1800 must be no more than a few light-years apart. D) If you observe them again in a few nights, RXJ1800 and Vega will be farther apart than they appear tonight. Answer: A 41) We see two stars separated by one degree on the celestial sphere. What can we infer about these stars? A) They are very close together in space. B) They have similar luminosities. C) They rise and set at about the same time. D) They were born about the same time. Answer: C Section 2.2 1) Seasons on Earth are caused by A) Earth's axis tilt. B) Earth's varying distance from the Sun. C) Earth's varying orbital speed around the Sun. D) the gravitational influence of the Moon. E) the Sun's gravity. Answer: A 2) When it is summer in the Northern Hemisphere, it is ________ in the Southern Hemisphere. A) winter B) fall C) spring D) summer Answer: A

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3) Why is it summer in the Northern Hemisphere when it is winter in the Southern Hemisphere?

A) The Northern Hemisphere is "on top" of Earth and therefore receives more sunlight during the Northern Hemisphere summer.

B) The Northern Hemisphere is tilted away from the Sun and receives more indirect sunlight during the Northern Hemisphere summer.

C) The Northern Hemisphere is tilted toward the Sun and receives more direct sunlight during the Northern Hemisphere summer.

D) It isn't: both hemispheres have the same seasons at the same time.

E) The Northern Hemisphere is closer to the Sun than the Southern Hemisphere during the Northern hemisphere summer.

Answer: C 4) It is summer in the Northern Hemisphere when A) the Northern Hemisphere is located closer to the Sun than the Southern Hemisphere.

B) the Northern Hemisphere is tilted toward the Sun and the Southern Hemisphere is tilted away.

C) Earth is at its nearest point to the Sun along its orbit.

D) Earth's axis points toward the North Star, Polaris.

Answer: B 5) The Northern and Southern hemispheres have equal illumination from the Sun A) on the June and December solstices.

B) on the March and September equinoxes.

C) on all four of the equinoxes and solstices.

D) only on the March equinox.

E) at all times.

Answer: B 6) Consider a set of hypothetical planets that are identical in their orbits and properties except they have different axis tilts. Which of the following axis tilts would give its planet the most extreme differences between their seasons? (Axis tilt is measured relative to a line drawn perpendicular to the planet's orbit.)

A) 23.5 degrees B) 90 degrees C) 0 degrees D) 45 degrees Answer: B

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7) Suppose that Earth's rotation axis were tilted by 45 degrees instead of 23.5 degrees. Which of the following would be true, and why?

A) The seasons would be more extreme, because the Sun's rays would be more direct in summer and less direct in winter.

B) The seasons would be more extreme, because the Earth's surface would be closer to the Sun in the summer and farther from the Sun in the winter.

C) The seasons would be less extreme, because the Sun's rays would be less direct in summer and more direct in winter.

D) The seasons would be less extreme, because the Earths' surface would be farther from the Sun in the summer and closer to the Sun in the winter.

Answer: A 8) Suppose Earth's rotation axis were tilted by 45 degrees instead of 23.5 degrees. How would the number of daylight hours be different on December 21 in the United States (or any northern hemisphere country)?

A) There would be more hours of daylight than we have with a 23.5 degree tilt.

B) There would be fewer hours of daylight than we have with a 23.5 degree tilt.

C) The number of daylight hours would be about the same as it is if its tilt were 23.5 degrees.

Answer: B 9) The line representing latitude 45 degrees north runs through the state of Michigan. In Michigan, when is the Sun is directly overhead, at your zenith?

A) every day B) only on the spring and fall equinoxes C) only on the summer solstice, noon D) never Answer: D 10) Today the Sun appears to be located in the middle of the constellation Virgo. Therefore, tomorrow the Sun will be in the constellation A) Libra.

B) Virgo.

C) Leo. D) Sagittarius.

Answer: B 11) Why is January a cold month in the northern United States?

A) Earth is near its farthest point from the sun.

B) There's more snow in January.

C) The northern hemisphere is farther from the sun than the southern hemisphere.

D) The northern hemisphere is tilted away from the sun.

Answer: D

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12) Has Polaris always been a good "North Star"? Why or why not?

A) yes, because stars stay fixed on the celestial sphere B) no, because it is a young star which formed only a few hundred years ago C) no, because Earth's axis slowly changes the direction it points D) no, because ancient people did not know how to describe directions on Earth Answer: C Section 2.3 1) The time from one new moon to the next is approximately A) one week.

B) two weeks.

C) three weeks.

D) one month.

E) two months.

Answer: D 2) Which of the following is not the name of one of the phases of the Moon?

A) first-quarter moon B) third-quarter moon C) half moon D) new moon E) full moon Answer: C 3) We say that the Moon is gibbous when A) it appears to be more than half illuminated, but not full.

B) it appears to be less than half illuminated, but not new.

C) it is exactly half illuminated.

D) we see a thin crescent of light.

E) the Moon is visible in the morning.

Answer: A 4) In which general direction should you look to see the Moon rise?

A) north B) south C) east D) west E) It depends on the phase of the Moon.

Answer: C 5) When we see a crescent moon, the rest of the face that we see is not completely dark because A) it is partially facing toward the Sun. B) it is slightly illuminated by sunlight reflected by Earth.

C) it is slightly illuminated by starlight.

D) it is slightly illuminated by the light of Earth's cities.

Answer: B

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6) In which general direction should you look to see the Moon set? A) north B) south C) east D) west E) It depends on the phase of the Moon. Answer: D 7) Which of the following statements about the Moon is not true? A) The Moon goes through its cycle of phases in about a month. B) The Moon's orbit around Earth is tilted about 5° to the ecliptic plane. C) The Moon's distance from Earth varies during its orbit. D) The Moon is visible in our sky only at night. E) The Moon rotates once in the same amount of time that it takes to orbit around Earth. Answer: D 8) Why do we see essentially the same face of the Moon at all times? A) because the other face points toward us only at new moon, when we can't see the Moon B) because the Moon does not rotate C) because the Moon's rotational and orbital periods are equal D) because the Sun illuminates only one half of the Moon at a time E) because the Moon has a nearly circular orbit around Earth Answer: C 9) Suppose you live on the Moon. When people on Earth see a first-quarter phase, what phase do you see for Earth? A) new Earth B) first-quarter Earth C) crescent Earth D) third-quarter Earth E) full Earth Answer: D 10) Suppose it is a crescent moon, as seen from Earth. How would Earth appear to someone on the Moon at this time? A) The side of Earth facing the Moon is completely bright. B) The illumination of the Earth does not change, as viewed from the Moon. C) Half of the side of Earth facing the Moon is bright and half is dark. D) Most of the side of Earth facing the Moon is bright. Answer: D

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11) Suppose you live on the Moon. About how long is a day (i.e., from sunrise to sunrise)?

A) 23 hours 56 minutes B) 24 hours C) a month D) a year E) about 18 years Answer: C 12) If the Moon is setting at 6 A.M., the phase of the Moon must be A) first quarter.

B) third quarter.

C) full.

D) new.

E) waning crescent.

Answer: C 13) If the Moon is setting at noon, then it rose at A) 6 A.M. B) 9 A.M. C) noon.

D) 6 P.M. E) midnight.

Answer: E 14) If the Moon is setting at noon, the phase of the Moon must be A) full.

B) first quarter.

C) third quarter.

D) waning crescent.

E) waxing crescent.

Answer: C 15) If the Moon is rising at midnight, the phase of the Moon must be A) full.

B) first quarter.

C) third quarter.

D) waning crescent.

E) waxing crescent.

Answer: C 16) At approximately what time would a full moon be on your meridian?

A) 6 A.M. B) 9 A.M. C) noon D) 6 P.M. E) midnight Answer: E

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17) At approximately what time would a first-quarter moon rise?

A) 6 A.M. B) 9 A.M. C) noon D) 6 P.M. E) midnight Answer: C 18) Approximately when does a first-quarter moon set?

A) sunset B) noon C) midnight D) sunrise Answer: C 19) Approximately when does a third-quarter moon rise?

A) sunset B) noon C) midnight D) sunrise Answer: C 20) Approximately when does a third-quarter moon set?

A) sunset B) noon C) midnight D) sunrise Answer: B 21) If the Moon rises around 3 A.M., its phase must be A) full.

B) first quarter.

C) third quarter.

D) waning crescent.

E) waxing crescent.

Answer: D 22) Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?

A) a crescent moon B) Your friend won't see the Moon tonight, because in South America, it will be visible only in the morning.

C) a gibbous moon D) a first-quarter moon Answer: A

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23) You observe a full moon rising at sunset. What will you see 6 hours later? A) a full moon on or near your meridian B) waning gibbous moon C) first-quarter moon D) a thirdquarter moon Answer: A 24) If the Moon is full at midnight, what will its phase be 6 hours later? A) full moon B) first-quarter moon C) new moon D) third-quarter moon Answer: A 25) Tonight the Moon is full. Therefore, in one week, the Moon will be A) full.

B) first quarter. C) third quarter. D) new. Answer: C 26) You see a waxing crescent moon.

You email your friend in New Zealand and ask her what moon phase she sees that night.

She says A) waxing crescent. B) waning crescent. C) waning gibbous. D) waxing gibbous.

Answer: A 27) All of the following statements are true. Which one explains the reason why there is not a solar eclipse at every new moon? A) The nodes of the Moon's orbit precess with an approximately 18-year period. B) The orbital plane of the Moon is tilted by about 5° to the ecliptic plane. C) The Moon rotates synchronously with its orbit around Earth. D) The Moon's orbital period is slightly shorter than the time it takes for a cycle of phases. E) The Moon's orbital distance varies as it orbits around Earth. Answer: B 28) Which of the following would be true about solar eclipses if the Moon's orbital plane was exactly aligned with the ecliptic plane? A) Solar eclipses would be rarer. B) Solar eclipses would occur more often. C) Solar eclipses would last much longer. D) Solar eclipses would be both rarer and would last much longer. E) Solar eclipses would both occur more often and would last much longer. Answer: B

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29) If the plane of the Moon's orbit around the Earth was perfectly aligned with the ecliptic plane (instead of being tilted by about 5°), a solar eclipse would be visible on some parts of Earth A) once a day.

B) never.

C) about once a month.

D) about once every six months.

E) about once a year.

Answer: C 30) The conditions required for a solar eclipse are A) (1) the phase of the Moon must be new; (2) the nodes of the Moon's orbit must be nearly aligned with Earth and the Sun. B) (1) the phase of the Moon must be full; (2) the nodes of the Moon's orbit must be nearly aligned with Earth and the Sun. C) (1) the phase of the Moon can be either new or full; (2) the nodes of the Moon's orbit must be nearly aligned with Earth and the Sun. D) (1) the phase of the Moon must be new; (2) the Moon must be located at the nearest point in its orbit around Earth.

E) (1) the phase of the Moon must be full; (2) the Moon must be located at the nearest point in its orbit around Earth.

Answer: A 31) Why are lunar eclipses more commonly seen than solar eclipses?

A) Lunar eclipses occur at night and are easier to see.

B) The Moon goes around the Earth faster than the Earth goes around the Sun. C) Earth casts a bigger shadow than the Moon.

D) The tilt of the Moon's axis is smaller than the Earth's.

E) The Moon is much closer to Earth than to the Sun. Answer: C 32) The conditions required for a lunar eclipse are A) (1) the phase of the Moon must be new; (2) the nodes of the Moon's orbit must be nearly aligned with Earth and the Sun. B) (1) the phase of the Moon must be full; (2) the nodes of the Moon's orbit must be nearly aligned with Earth and the Sun. C) (1) the phase of the Moon can be either new or full; (2) the nodes of the Moon's orbit must be nearly aligned with Earth and the Sun. D) (1) the phase of the Moon must be new; (2) the Moon must be located at the nearest point in its orbit around Earth.

E) (1) the phase of the Moon must be full; (2) the Moon must be located at the nearest point in its orbit around Earth.

Answer: B

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33) In addition to the conditions required for any solar eclipse, what must also be true in order for you to observe a total solar eclipse? A) Earth must lie completely within the Moon's full shadow (umbra). B) Earth must lie completely within the Moon's partial shadow (penumbra). C) Earth must be near aphelion in its orbit of the Sun. D) The Moon's full shadow (umbra) must touch the area where you are located. E) The Moon's partial shadow (penumbra) must touch the area where you are located. Answer: D 34) When only part of the Moon is covered by Earth's full shadow (umbra), we see a(n) A) total lunar eclipse. B) penumbral lunar eclipse. C) partial lunar eclipse. D) partial solar eclipse. E) annular eclipse. Answer: C 35) If a solar eclipse occurs when the Moon is relatively far from Earth, so that its full shadow (umbra) does not reach Earth, then people directly behind the full shadow will experience A) a penumbral eclipse. B) a total solar eclipse. C) a partial solar eclipse. D) an annular eclipse. E) no eclipse. Answer: D 36) During a lunar eclipse, the Moon's phase must be A) first quarter. B) third quarter. C) full. D) new. Answer: C 37) During a solar eclipse, the Moon's phase must be A) first quarter. B) third quarter. C) full. D) new. Answer: D 38) Imagine that you are on the Moon while your friend experiences a total solar eclipse on Earth. What do you see? A) You also see a solar eclipse, except with the Sun completely covered by the Earth. B) You see a relatively small shadow on an otherwise full Earth. C) You see a full Earth, just as you would if there were no eclipse at this time. D) You cannot see the Earth because it is blocked by the Sun. Answer: B

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39) When are eclipse seasons?

A) in the spring and fall B) in the summer and winter C) when the nodes of the Moon's orbit are nearly aligned with the Sun D) when Earth and the Sun are aligned with one another E) during an eclipse Answer: C 40) What effect does the precession of the Moon's nodes have on eclipses?

A) It causes us to have lunar eclipses exactly every 6 months.

B) It causes eclipses to occur a little less often than they would if the nodes did not precess.

C) It causes eclipses to occur a little more often than they would if the nodes did not precess.

D) Without this precession, eclipses could never occur.

E) Without this precession, eclipses would occur every month.

Answer: C 41) What is the saros cycle?

A) the roughly 6-month period between eclipse seasons B) the approximately 18-year, 11-day cycle over which the pattern of eclipses repeats C) the average time between total solar eclipses D) the average time between a total solar eclipse and a total lunar eclipse E) the 26,000 year cycle over which Earth's axis sweeps out a cone in space Answer: B 42) Ancient people who knew the saros cycle could A) completely predict the details of all eclipses.

B) completely predict the details of solar eclipses, but not lunar eclipses.

C) completely predict the details of lunar eclipses, but not solar eclipses.

D) predict the date and time of the next total solar eclipse that would be visible at their location.

E) predict when lunar and solar eclipses would occur, but not necessarily whether the eclipse would be partial or total, or exactly where it would be visible.

Answer: E Section 2.4 1) Which of the following objects was not recognized as a planet in ancient times?

A) Mercury B) Mars C) Jupiter D) Saturn E) Neptune Answer: E

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2) What happens during the apparent retrograde motion of a planet? A) The planet rises in the west and sets in the east. B) The planet appears to move westward with respect to the stars over a period of weeks to months. C) The planet moves backward through the sky over the course of a night. D) The planet moves backward in its orbit around the Sun. E) The planet moves through constellations that are not part of the zodiac. Answer: B 3) What causes the apparent retrograde motion of the planets? A) It is an illusion created as we pass by a planet in our orbit (or the planet passes by us). B) It occurs when the planets reverse the direction of their orbits around the Sun. C) It is caused by the motion of planets around small circles that in turn go around bigger circles. D) It is an illusion created by our lack of depth perception in space. E) It is something we see only for planets that orbit the Sun in the opposite direction of Earth. Answer: A 4) Which of the following objects never appears to exhibit retrograde motion in our sky? A) The Sun B) Venus C) Mars D) Jupiter E) Saturn Answer: A 5) Which of the following statements about parallax is not true? A) You can demonstrate parallax simply by holding up a finger and looking at it alternately from your left and right eyes. B) The existence of stellar parallax is direct proof that Earth orbits the Sun. C) Measurement of stellar parallax allows us to determine distances to nearby stars. D) Observing stellar parallax requires only a single photograph taken through a powerful telescope. E) Ancient astronomers were unable to detect stellar parallax and used the absence of observed parallax as an argument in favor of an Earth-centered universe. Answer: D 6) Which of the following stars would exhibit the largest amount of stellar parallax? A) the star that is nearest to us B) the star that is farthest from us C) the star that is brightest in our sky D) the star that is dimmest in our sky E) the star that is moving at the highest speed relative to Earth Answer: A

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7) We can't detect stellar parallax with naked-eye observations. Which of the following would make parallax easier to observe?

A) increasing the size of Earth's orbit B) speeding up Earth's rotational motion C) slowing down Earth's rotational motion D) speeding up the precession of Earth's axis E) getting away from streetlights Answer: A 8) Why were ancient peoples unable to detect stellar parallax?

A) They did not look for it.

B) They could not see distant stars.

C) They did not have the ability to measure very small angles.

D) They did not observe for long enough periods of time.

E) They did detect it, but they rejected the observations.

Answer: C 9) The parallax of two stars is reported in a star catalog. Which star is farther?

A) The one with the larger amount of parallax B) You can't tell, since parallax has nothing to do with distance.

C) The one with the smaller amount of parallax Answer: C General Chapter Questions 1) Which of the following explains why Polaris will no longer be the North Star 1,000 years from now?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: C 2) Choose the answer that fills in the three blanks in the correct order: Earth rotates once each ________, Earth orbits the Sun once each ________, and the Moon orbits Earth about once each ________.

A) day, year, month B) day, year, week C) year, day, month D) hour, day, year E) hour, day, month Answer: A

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3) The reason we don't see stars in the daytime is because A) the sky is too bright.

B) stars shine only at night.

C) there are no stars in the direction of the Sun. D) stars disappear in the daytime.

Answer: A 4) Which of the following explains why, about 13,000 years from now, Vega will be a better North Star than Polaris?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: C 5) Which of the following explains why the Big Dipper will look different 100,000 years from now than it does today?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: D 6) Which of the following explains why the Moon rises in the east and sets in the west?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: A 7) Which of the following explains why the stars of Orion's belt rise in the east and set in the west?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: A

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8) Which of the following explains why, a million years from now, Alpha Centauri will no longer be the nearest star system to our own?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: D 9) Which of the following explains why the Sun appears to move gradually eastward along the path called the ecliptic on the celestial sphere?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: D 10) Which of the following explains why we see different constellations at different times of year?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: D 11) Which of the following explains why the stars visible in our sky just after sunset are different from those visible just before sunrise?

A) Earth rotates once each day.

B) Earth orbits the Sun once each year.

C) The direction of Earth's axis in space precesses with a period of about 26,000 years.

D) Stars appear to move randomly relative to our Sun in the local solar neighborhood.

E) The universe is expanding.

Answer: A 12) If Earth rotated once every 48 hours (instead of 24 hours), but everything else was the same, which of the following statements would be false?

A) There would still be summer and winter seasons.

B) The length of the year would be longer.

C) The Sun would appear to move across the sky at a slower rate.

D) The length of a day would be longer.

Answer: B

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13) Suppose you see a photo showing Jupiter half in sunlight and half in shadow (i.e., a firstquarter Jupiter). This photo might have been taken by A) the Keck telescope, on Mauna Kea, Hawaii.

B) the Arecibo radio telescope in Puerto Rico.

C) the Hubble Space Telescope (which orbits Earth).

D) the Juno spacecraft that is orbiting Jupiter.

Answer: D Reading Quiz Questions 1) About how many stars are visible to the naked eye on a clear, dark night away from city lights?

A) a few dozen B) a couple thousand C) several million D) a few hundred billion Answer: B 2) What do astronomers mean by a constellation?

A) A constellation is a region in the sky as seen from Earth.

B) A constellation is a group of stars related through an ancient story.

C) A constellation is any random grouping of stars in the sky.

D) A constellation is a group of stars that are all located in about the same place in space.

Answer: A 3) What is the ecliptic?

A) the path the Sun appears to trace around the celestial sphere each year B) the Sun's daily path from east to west in our sky C) the path traced by the Moon's shadow on Earth during a solar eclipse D) a half-circle extending from your horizon due north, through your zenith, to your horizon due south Answer: A 4) What is the celestial sphere?

A) The celestial sphere is a representation of how the entire sky looks as seen from Earth.

B) The celestial sphere is a model that shows the true locations in space of the Sun and a few thousand of the nearest stars.

C) The celestial sphere is a model of how the stars are arranged in the sky relative to our Sun, which is in the middle of the sphere.

D) It represents a belief in an Earth-centered universe, and hence is no longer considered to have any use.

Answer: A

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5) What do we mean when we talk about the Milky Way in our sky?

A) The patchy band of light that outlines the plane of the Milky Way Galaxy as seen from Earth.

B) The whitish patch of light we see when we look toward the center of the Milky Way Galaxy.

C) The spiral-shaped galaxy in which we live.

D) The bright stars of the constellations that lie along the ecliptic in our sky.

Answer: A 6) Which of the following correctly describes the meridian in your local sky?

A) a half-circle extending from your horizon due east, through your zenith, to your horizon due west B) a half-circle extending from your horizon due east, through the north celestial pole, to your horizon due west C) a half-circle extending from your horizon due north, through your zenith, to your horizon due south D) the point directly over your head Answer: C 7) The point directly over your head is called A) the meridian.

B) the zenith.

C) the north celestial pole.

D) the North Star.

Answer: B 8) Which of the following celestial objects do not rise in the east and set in the west? (Assume that all of these objects are visible from your location on Earth, and that none of them are circumpolar.)

A) stars B) the Sun C) the Moon D) galaxies E) All of these objects rise in the east and set in the west.

Answer: E 9) Which of the following statements does not use the term angular size or angular distance correctly?

A) The angular distance between those two houses in the distance is 30 degrees.

B) The angular distance between those two bright stars in the sky is about 2 meters.

C) The angular size of the Sun is about the same as that of the Moon.

D) You can use your outstretched hand against the sky to estimate angular sizes and angular distances.

Answer: B

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10) Stars that are visible in the local sky on any clear night of the year, at any time of the night, are called A) bright.

B) seasonal.

C) circumpolar.

D) celestial.

Answer: C 11) We describe a location on Earth's surface by stating its A) altitude and direction (or azimuth).

B) meridian and longitude.

C) latitude and direction.

D) latitude and longitude.

Answer: D 12) If you are located in the Northern Hemisphere, which of the following correctly describes a relationship between the sky and your location?

A) The altitude of the north celestial pole equals your latitude.

B) The altitude of the celestial equator equals your latitude.

C) The altitude of the north celestial pole equals your longitude.

D) The longitude of the north celestial pole is circumpolar, and therefore crosses your zenith at the meridian.

Answer: A 13) Which of the following best describes why we have seasons on Earth?

A) The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.

B) Earth's elliptical orbit means we are closer to the Sun and therefore receive more intense sunlight at some times of year than at others.

C) The tilt of Earth's axis causes the Northern Hemisphere to be closer to the Sun than the Southern Hemisphere in summer, and vice versa in winter.

D) The varying speed of Earth in its orbit around the Sun gives us summer when we are moving fastest and winter when we are moving slowest.

Answer: A

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14) Each choice describes how a few astronomical phenomena are related to time periods. Which list is entirely correct? (Careful: some lists are partially correct.)

A) Earth's rotation defines a day.

The cycle of the Moon's phases takes about a month.

Earth's orbit defines a year.

Earth's cycle of axis precession takes 26,000 years.

B) Earth's rotation defines a day.

The cycle of the Moon's phases takes about a week.

Earth's orbit defines a year.

Earth's cycle of axis precession defines a month.

C) Earth's rotation defines a day.

The Sun's rotation defines a week.

The Moon's rotation defines a month.

Earth's orbit defines a year.

D) Earth's rotation defines a day.

The Saros cycle of eclipses defines a month.

Earth's orbit defines a year.

Earth's cycle of axis precession takes 26,000 years.

Answer: A 15) If we have a new moon today, when we will have the next full moon?

A) in about two weeks B) in about one week C) in about a month D) in about six months Answer: A 16) We cannot see a new moon in our sky because A) it is obscured by Earth's shadow.

B) no sunlight is illuminating the Moon.

C) a new moon is quite near the Sun in the sky.

D) it is above the horizon during the daytime.

Answer: C 17) The Moon always shows nearly the same face to Earth because A) the Moon does not rotate.

B) sunlight always hits the same face of the Moon.

C) the Moon rotates once in the same amount of time that it takes Earth to orbit the Sun once.

D) the Moon rotates once in the same amount of time that it takes the Moon to orbit Earth once.

Answer: D 18) Lunar eclipses can occur only when the phase of the Moon is A) new.

B) first quarter.

C) full.

D) third quarter.

Answer: C

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19) What is the Saros cycle?

A) the 26,000-year cycle of the Earth's precession B) the roughly 18-year cycle over which the pattern of eclipses repeats C) the roughly one-month cycle of lunar phases in the sky D) the annual cycle of the seasons Answer: B 20) During the time that a planet is in its period of apparent retrograde motion A) The planet moves backwards (clockwise as viewed from above Earth's north pole) in its orbit of the Sun. B) The planet appears to rise in the west and set in the east, rather than the usual rising in the east and setting in the west.

C) Over many days or weeks, the planet moves westward relative to the stars, rather than the usual eastward relative to the stars.

D) The planet is getting closer to the Sun in its orbit.

Answer: C 21) What is stellar parallax?

A) It is the daily rise and set of the stars.

B) It describes the fact that stars are actually moving relative to one another, even though to our eyes the stars appear fixed in the constellations.

C) It is the slight back-and-forth shifting of star positions that occurs as we view the stars from different positions in Earth's orbit of the Sun. D) It is the change in the set of constellations that we see at different times of year in the evening sky.

Answer: C 22) If a star's distance from Earth increased, its parallax shift would A) decrease.

B) increase.

C) not change.

Answer: A Concept Quiz Questions 1) Which of the following statements about the celestial sphere is not true?

A) The Earth is placed at the center of the celestial sphere.

B) When we look in the sky, the stars all appear to be located on the celestial sphere.

C) The celestial sphere is another name for our universe.

D) The celestial sphere does not exist physically.

Answer: C

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2) The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda.

Suppose instead it were located in the same direction in space as the center of the Milky Way Galaxy (but still at its current distance). How would it appear to the eye in that case?

A) We could not see it at all.

B) It would look about the same but would be in the constellation Sagittarius instead of Andromeda.

C) It would be much brighter because it would be illuminated by the many stars in the center of our galaxy.

D) It would look about the same, but it would be harder to pick out because its cloud-like appearance would make it blend in with the cloud-like appearance of the Milky Way in our sky.

Answer: A 3) An angle of 1 arcsecond is A) about the width of your fist held at arm's length.

B) about the width of a finger held at arm's length.

C) less than the thickness of a human hair held at arm's length.

D) slightly more than the width of a basketball held at arm's length.

Answer: C 4) When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting A) brighter.

B) dimmer.

C) higher in the sky.

D) lower in the sky.

Answer: C 5) Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon. Then you must be located at A) latitude 40 degrees north.

B) latitude 50 degrees south.

C) latitude 40 degrees south.

D) longitude 40 degrees.

Answer: C 6) Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?

A) to the right of Polaris; that is, 90 degrees counterclockwise from its current position B) to the left of Polaris; that is, 90 degrees clockwise from its current position C) directly above Polaris D) still in the same place, below Polaris Answer: A

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7) In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because A) our evening view of space depends on where Earth is located in its orbit around the Sun. B) during some times of year, some constellations drop below the southern horizon.

C) some constellations are circumpolar.

D) on any particular night, we can only see stars that are directly opposite (180 degrees away from) the Sun in the sky.

Answer: A 8) The Sun's path, as viewed from the equator, is highest in the sky on A) the December solstice.

B) the March and September equinoxes.

C) the June solstice.

D) the day when Earth is closest to the Sun. Answer: B 9) Suppose Earth's axis tilt was significantly greater than its current 23.5 degrees, but Earth's rotation period and orbital period were unchanged. Which statement below would not be true?

A) Summers and winters would be more severe (for example, hotter and colder, respectively) than they are now.

B) The region of Earth where the Sun does not rise on the winter solstice would be larger (extending farther south) than it is now.

C) The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now.

D) Polaris would not be our North star.

Answer: C 10) If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth's rotation period and axis tilt were unchanged, then A) stars would take twice as long to rise and set.

B) the cycle of precession would take 13,000 years instead of 26,000 years.

C) the four seasons would each be twice as long as they are now.

D) the Earth would not have seasons.

Answer: C 11) How does Earth's varying distance from the Sun affect our seasons?

A) It doesn't; Earth's orbital distance plays no significant role in the seasons.

B) It makes summer warmer in the Northern Hemisphere than in the Southern Hemisphere.

C) It is responsible for the fact that the seasons are opposite in the Northern and Southern hemispheres.

D) It causes the seasons to be more extreme than they would be if the Earth's distance from the Sun were always the same.

Answer: A

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12) Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?

A) Your friend will see a gibbous moon.

B) Your friend will also see a crescent moon.

C) Your friend will see a first-quarter moon.

D) Your friend won't see the Moon tonight because it is up only in the morning.

Answer: B 13) Suppose it is full moon. What phase of Earth would someone on the Moon see at this time?

A) full Earth B) new Earth C) first-quarter Earth D) Earth does not go through phases as seen from the Moon.

Answer: B 14) It's 6 a.m. and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon's phase?

A) new B) first quarter C) full D) third quarter Answer: D 15) You observe a full Moon rising at sunset. What will you see at midnight?

A) a full moon high in the sky B) a first-quarter moon C) a waning gibbous moon D) a third-quarter moon Answer: A 16) All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon?

A) The nodes of the moon's orbit precess with an 18-year period.

B) The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.

C) The Moon is only about one-fourth as large as Earth in diameter.

D) The Moon goes through a complete cycle of phases about every 29-1/2 days.

Answer: B 17) For most of history, the lack of observable stellar parallax was interpreted to mean that A) stars must all lie at the same distance from Earth, on the celestial sphere.

B) stars were too far away for parallax to be measured with available technology.

C) Earth is stationary at the center of the universe.

D) Galileo's theories of the universe were essentially correct.

Answer: C

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18) During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space? A) Mars is moving around the Sun in the opposite direction from which Earth is moving around the Sun. B) Earth and Mars are getting closer together. C) Earth is catching up with and passing by Mars in their respective orbits. D) Earth and Mars are on opposite sides of the Sun. Answer: C 19) Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first quarter Jupiter).

This photo might have been taken by A) a spacecraft orbiting Jupiter. B) the Hubble Space Telescope (which orbits Earth). C) the Keck telescope on Mauna Kea, Hawaii. D) the Arecibo radio telescope in Puerto Rico. Answer: A Visual Quiz Questions 1) This diagram represents a simplified model of the celestial sphere. The unlabeled circle that is highlighted in purple represents

A) the celestial equator.

B) the meridian.

C) the ecliptic.

D) the spring equinox.

Answer: A

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2) This diagram represents a person's local sky. What does the red semicircle represent?

A) the horizon B) the meridian C) the zenith D) the celestial equator Answer: B 3) What is the approximate latitude and longitude of the South American location marked by the black dot on this diagram?

A) latitude = 15ºS, longitude = 45ºW B) latitude = 30ºW, longitude = 60ºN C) latitude = 15ºN, longitude = 45ºW D) latitude = 15ºS, longitude = 75ºW Answer: A

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4) Diagrams like this one are commonly used in discussions of seasons and they can be quite useful. However, this diagram greatly exaggerates A) the size of Earth relative to the size of Earth's orbit around the Sun. B) the size of the Sun relative to the size of Earth's orbit around the Sun. C) the amount by which Earth's orbit differs from a perfect circle.

D) all of the answers listed.

E) only the first and third choices.

Answer: D 5) Which position in this diagram represents Earth on the day that we have the longest amount of daylight in the continental United States?

A) 1 B) 2 C) 3 D) 4 Answer: B 6) Which position in this diagram represents Earth at the beginning of spring for the Southern Hemisphere?

A) 1 B) 2 C) 3 D) 4 Answer: C

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7) Which photo shows what we call a first-quarter moon? (Note: Assume these photos were taken in the Northern Hemisphere.)

A) 1 B) 2 C) 3 D) 4 Answer: B 8) Which photo shows what we call a gibbous moon? (Note: Assume these photos were taken in the Northern Hemisphere.)

A) 1 B) 2 C) 3 D) 4 Answer: C 9) This multiple exposure photograph shows the apparent retrograde motion of Mars. To make this picture, the photographer needed to combine individual photos of Mars taken over a period of

A) one full night.

B) about one hour.

C) about 3 nights.

D) several months.

Answer: D

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10) What is this a picture of?

A) a total solar eclipse B) a total lunar eclipse C) the saros cycle D) a full moon Answer: A End-of-Chapter Questions

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Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

The figure above is a typical diagram used to describe Earth's seasons.

The figure above (based on Figure 2.14) shows the Sun's path through the constellations of the zodiac.

1) Which of the four labeled points (A through D) represents the day with the most hours of daylight for the Northern Hemisphere?

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2) Which of the four labeled points represents the day with the most hours of daylight for the Southern Hemisphere? Answer: D 3) Which of the four labeled points represents the beginning of spring for the Southern Hemisphere? Answer: C 4) The diagram exaggerates the sizes of Earth and the Sun relative to the orbit. If Earth were correctly scaled relative to the orbit in the figure, how big would it be? A) about half the size shown B) about 2 millimeters across C) about 0.1 millimeter across D) microscopic Answer: D 5) Given that Earth's actual distance from the Sun varies by less than 3% over the course of a year, why does the diagram look so elliptical? A) It correctly shows that Earth is closest to the Sun at points A and C and farthest at points B and D. B) The elliptical shape is an effect of perspective, since the diagram shows an almost edge-on view of a nearly circular orbit. C) The shape of the diagram is meaningless and is done only for artistic effect. Answer: B 6) As viewed from Earth, in which zodiac constellation does the Sun appear to be located on April 21? A) Leo B) Aquarius C) Libra D) Aries Answer: D 7) If the date is April 21, what zodiac constellation will be visible on your meridian at midnight? A) Leo B) Aquarius C) Libra D) Aries Answer: C

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8) If the date is April 21, what zodiac constellation will you see setting in the west shortly after sunset?

A) Scorpius B) Pisces C) Taurus D) Virgo Answer: C Chapter Review Questions 1) What are constellations? How did they get their names?

2) Suppose you were making a model of the celestial sphere with a ball. Briefly describe all the things you would need to mark on your celestial sphere.

3) On a clear, dark night, the sky may appear to be "full" of stars. Does this appearance accurately reflect the way stars are distributed in space? Explain.

4) Why does the local sky look like a dome? Define horizon, zenith, and meridian. How do we describe the location of an object in the local sky?

5) Explain why we can measure only angular sizes and angular distances for objects in the sky.

What are arcminutes and arcseconds?

6) What are circumpolar stars? Are more stars circumpolar at the North Pole or in the United States? Explain.

7) What are latitude and longitude? Does the sky vary with latitude? Does it vary with longitude?

Explain.

8) What is the zodiac, and why do we see different parts of it at different times of year?

9) Suppose Earth's axis had no tilt. Would we still have seasons? Why or why not?

10) Briefly describe key facts about the solstices and equinoxes.

11) What is precession? How does it affect what we see in our sky?

12) Briefly describe the Moon's cycle of phases. Can you ever see a full moon at noon? Explain.

13) Why do we always see the same face of the Moon?

14) Why don't we see an eclipse at every new and full moon? Describe the conditions needed for a solar or lunar eclipse.

15) What do we mean by the apparent retrograde motion of the planets? Why was this motion difficult for ancient astronomers to explain? How do we explain it today?

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16) What isstellar parallax? How did an inability to detect it support the ancient belief in an Earth-centered universe?

Does It Make Sense?

Decide whether or not each of the following statements makes sense (or is clearly true or false).

Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.

Example: I walked east from our base camp at the North Pole.

Solution: The statement does not make sense because east has no meaning at the North Pole–all directions are south from the North Pole.

17) The constellation Orion didn't exist when my grandfather was a child.

18) When I looked into the dark lanes of the Milky Way with my binoculars, I saw a cluster of distant galaxies.

19) Last night the Moon was so big that it stretched for a mile across the sky.

20) I live in the United States, and during a trip to Argentina I saw many constellations that I'd never seen before.

21) Last night I saw Jupiter in the middle of the Big Dipper. (Hint: Is the Big Dipper part of the zodiac?)

22) Last night I saw Mars move westward through the sky in its apparent retrograde motion.

23) Although all the known stars rise in the east and set in the west, we might someday discover a star that will rise in the west and set in the east.

24) If Earth's orbit were a perfect circle, we would not have seasons.

25) Because of precession, someday it will be summer everywhere on Earth at the same time.

26) This morning I saw the full moon setting at about the same time the Sun was rising.

Quick Quiz

27) Two stars that are in the same constellation A) must both be part of the same cluster of stars in space.

B) must both have been discovered at about the same time.

C) may actually be very far away from each other.

Answer: No Correct Answer Was Provided.

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28) The north celestial pole is 35° above your northern horizon. This tells you that you are at A) latitude 35°N. B) longitude 35°E. C) latitude 35°S. Answer: No Correct Answer Was Provided.

29) Beijing and Philadelphia have about the same latitude but different longitudes. Therefore, tonight's night sky in these two places will A) look about the same.

B) have completely different sets of constellations.

C) have partially different sets of constellations.

Answer: No Correct Answer Was Provided.

30) In winter, Earth's axis points toward the star Polaris. In spring, the axis points toward A) Polaris.

B) Vega.

C) the Sun. Answer: No Correct Answer Was Provided.

31) When it is summer in Australia, the season in the United States is A) winter.

B) summer.

C) spring.

Answer: No Correct Answer Was Provided.

32) If the Sun rises precisely due east A) you must be located at Earth's equator.

B) it must be the day of either the March or the September equinox.

C) it must be the day of the June solstice.

Answer: No Correct Answer Was Provided.

33) A week after full moon, the Moon's phase is A) first quarter.

B) third quarter.

C) new.

Answer: No Correct Answer Was Provided.

34) The fact that we always see the same face of the Moon tells us that the Moon A) does not rotate.

B) rotates with the same period that it orbits Earth.

C) looks the same on both sides.

Answer: No Correct Answer Was Provided.

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35) If there is going to be a total lunar eclipse tonight, then you know that A) the Moon's phase is full.

B) the Moon's phase is new.

C) the Moon is unusually close to Earth.

Answer: No Correct Answer Was Provided.

36) When we see Saturn going through a period of apparent retrograde motion, it means A) Saturn is temporarily moving backward in its orbit of the Sun. B) Earth is passing Saturn in its orbit, with both planets on the same side of the Sun. C) Saturn and Earth must be on opposite sides of the Sun. Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

37) Cultural Constellations.Many cultures have created their own sets of constellations that differ from those used officially in astronomical research. Learn about the constellations of a particular culture of interest to you. How do the patterns of your chosen constellation(s) relate to the patterns of the official constellations listed in Appendix H? Which set of patterns makes more sense to you personally? 38) Group Discussion: Sharing the Sky. Astronomers around the world are fond of saying "we all share the same sky." Gather in groups of two to four students to discuss the meaning of this statement. a) Give each group member a chance to describe the similarities and differences you would expect between the sky you see during a 24-hour period and the sky seen by someone on the opposite side of the world or on the other side of the equator. b) Discuss whether you think that people making independent studies of the sky in different locations would come to similar conclusions about how the universe works. Would their conclusions be more accurate if they shared perspectives with people from other places? Why or why not? c) Discuss whether the skies that people saw 2000 years ago differ in any significant ways from the skies we see today. d) Do you think that people living 2000 years from now will have experiences of the sky that are similar to your own?

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The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

39) Earth-Centered or Sun-Centered?

Decide whether each of the following phenomena is consistent or inconsistent with a belief in an Earth-centered system. If consistent, describe how.

If inconsistent, explain why, and also explain why the inconsistency did not immediately lead people to abandon the Earth-centered model. a) The daily paths of stars through the sky b) Seasons c) Phases of the Moon d) Eclipses e) Apparent retrograde motion of the planets 40) Shadow Phases. Many people incorrectly guess that the phases of the Moon are caused by Earth's shadow falling on the Moon. How would you convince a friend that the phases of the Moon have nothing to do with Earth's shadow? Describe the observations you would use to show that Earth's shadow can't be the cause of phases.

41) Earth-Centered Language. Many common phrases reflect the ancient Earth-centered view of our universe. For example, although we now know that day and night arise from Earth's rotation, we speak of "sunrise" or "sunset" as though the Sun were moving around us daily. Identify other common phrases that imply an Earth-centered viewpoint. Do you think this language creates any difficulties in teaching science? Why or why not?

42) A Flat Earth? A few relatively famous people have recently made the claim that the Earth is flat. Working in small groups, first find out the basis on which they make these claims, then make a list of key observations that refute the flat Earth claims. Based on what you learn, how can you tell which websites discussing flat Earth claims are scientifically valid and which are not, and what lessons the flat Earth claims may contribute to the more general issue of "fake news" in our modern society?

43) Group Activity: Lunar Phases and Time of Day. Make a copy of the diagram below representing the Moon's orbit as seen from above Earth's North Pole.Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39; you may also find it useful to watch the video "Moon Phases, Part 2."

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a) Label each of the eight Moon positions with the phase that it represents. b) What time of day corresponds to each of the four tick marks on Earth? Label each tick mark accordingly. c) Why doesn't the Moon's phase change during the course of one night? Explain your reasoning. d) At what times of day would a full moon be visible to someone on Earth? Write down when a full moon rises and explain why it appears to rise at that time. e) At what times of day would a third-quarter moon be visible to someone on Earth? Write down when a third-quarter moon sets and explain why it appears to set at that time. f) At what times of day would a waxing crescent moon be visible to someone on Earth? Write down when a waxing crescent moon rises and explain why it appears to rise at that time.

Investigate Further 44) New Planet. A planet in another solar system has a circular orbit and an axis tilt of 35°.

Would you expect this planet to have seasons? If so, would you expect them to be more extreme than the seasons on Earth? If not, why not?

45) Your View of the Sky. a) What are your latitude and longitude? b) Where does the north (or south) celestial pole appear in your sky? c) Is Polaris a circumpolar star in your sky? Explain.

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46) View from the Moon. Assume you live on the Moon, near the center of the face that looks toward Earth. a) Suppose you see a full earth in your sky. What phase of the Moon would people on Earth see?

Explain. b) Suppose people on Earth see a full moon. What phase would you see for Earth? Explain. c) Suppose people on Earth see a waxing gibbous moon. What phase would you see for Earth?

Explain. d) Suppose people on Earth are viewing a total lunar eclipse. What would you see from your home on the Moon? Explain.

47) View from the Sun. Suppose you lived on the Sun (and could ignore the heat). Would you still see the Moon go through phases as it orbits Earth? Why or why not?

48) A Farther Moon. Suppose the distance to the Moon were twice its actual value. Would it still be possible to have a total solar eclipse? Why or why not?

49) A Smaller Earth. Suppose Earth were smaller. Would solar eclipses be any different? If so, how? What about lunar eclipses?

50) Project: Observing Planetary Motion. Find out which planets are currently visible in your evening sky. At least once a week, observe the planets and draw a diagram showing the position of each visible planet relative to stars in a zodiac constellation. From week to week, note how the planets are moving relative to the stars. Can you see any of the apparently wandering features of planetary motion? Explain.

51) Project: Eclipse Trip. Find details about a future total solar eclipse that you may be able to observe. Create a plan for a trip to see the eclipse, including details of where you will view it, how you will get there, and what you should expect to see.

52) Project: A Connecticut Yankee. Read A Connecticut Yankee in King Arthur's Court by Mark Twain. What role does an eclipse play in the story? Discuss its significance.

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

53) Arcminutes and Arcseconds.

There are 360° in a full circle. a) How many arcminutes are in a full circle? b) How many arcseconds are in a full circle? c) The Moon's angular size is about °. What is this in arcminutes? In arcseconds?

54) Latitude Distance. Earth's radius is approximately 6370 km. a) What is Earth's circumference? b) What distance is represented by each degree of latitude? c) What distance is represented by each arcminute of latitude? d) Can you give similar answers for the distances represented by a degree or arcminute of longitude? Why or why not?

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55) Angular Conversions I. The following angles are given in degrees and fractions of degrees. Rewrite them in degrees, arcminutes, and arcseconds. a) 24.3° b) 1.59° c) 0.1° d) 0.01° e) 0.001° 56) Angular Conversions II. The following angles are given in degrees, arcminutes, and arcseconds. Rewrite them in degrees and fractions of degrees. a) 7° 38' 42" b) 12' 54" c) 1° 59' 59" d) 1' e) 1" 57) Sun Diameter. Use the Sun's approximate distance of 150 million km and angular diameter of about 0.5° to calculate the Sun's physical diameter. Compare your answer to the actual value of 1,390,000 km. 58) Betelgeuse Diameter. Estimate the diameter of the supergiant star Betelgeuse from its angular diameter of 0.05 arcsecond and distance of about 600 light-years. Compare your answer to the size of our Sun and the Earth-Sun distance. 59) Eclipse Conditions. The Moon's precise equatorial diameter is 3476 km, and its orbital distance from Earth varies between 356,400 and 406,700 km. The Sun's diameter is 1,390,000 km, and its distance from Earth ranges between 147.5 and 152.6 million km. a) Find the Moon's angular size at its minimum and maximum distances from Earth. b) Find the Sun's angular size at its minimum and maximum distances from Earth. c) Based on your answers to parts a and b, is it possible to have a total solar eclipse when the Moon and Sun are both at their maximum distance? Explain.

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The Cosmic Perspective, 9e (Bennett et al.)

Chapter 3 The Science of Astronomy Section 3.1 1) People of central Africa learned to predict rainfall patterns by tracking rainfall amounts and A) recording the seasonal changes in average temperature.

B) observing the path of the planets across the sky.

C) observing the length of the lunar cycle.

D) observing the orientation of the crescent Moon relative to the horizon.

E) observing the location of the Moon relative to the Sun in the sky.

Answer: D 2) Which of the following hypotheses best explains the success of the central African rainfall prediction technique of observing the waxing crescent Moon?

A) When the Moon is aligned in a U-shape, it can hold more water, so there is more rain. When it is tilted, it can hold less, so the weather is drier.

B) When the Moon is in Capricorn, there is always more tempestuous weather, while when in Pisces, it is just plain rainy.

C) Clouds cover part of the Moon's surface, so the smaller the crescent, the more likely it is to rain.

D) The Moon's orientation varies seasonally, and so does the weather.

E) The Moon causes the tides and affects the weather.

Answer: D 3) The names of the seven days of the week are based on the A) seven naked-eye objects that appear to move among the constellations.

B) seven planets closest to the Sun. C) seven brightest stars in the prominent constellation Orion.

D) most popular Norse gods.

E) seven largest constellations of the ancient world.

Answer: A 4) Historians trace the origins of our dividing a day into 24 hours to A) the druids of Stonehenge.

B) the ancient Egyptians.

C) the Mayans.

D) the Aztecs.

E) the Babylonian astronomer, Meton.

Answer: B

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5) At the Sun Dagger in New Mexico, a dagger-shaped beam of sunlight pierced a spiral A) every day at noon. B) at noon on the summer solstice. C) at sunset on the spring equinox.

D) at noon on the day of full Moon each month. E) during the totality of a total solar eclipse.

Answer: B 6) The Metonic cycle is the A) 29-1/2-day period of the lunar cycle. B) 12-month period of a lunar calendar. C) 19-year period over which the lunar phases occur on about the same dates. D) 18-year, 11-day period over which the pattern of eclipses repeats. E) period between successive Easters.

Answer: C 7) How did the Egyptians use "star clocks" to estimate the time? A) They catalogued where particular stars appeared in the sky at various times of night throughout the year. B) They counted the number of stars visible at different times of night. C) They observed shadows cast by large obelisks blocking starlight. D) They measured the angular distance between the Moon and the brightest star in the sky. E) They created a catalog of where and when different planets would appear in particular locations among the constellations. Answer: A Section 3.2 1) How did Eratosthenes estimate the size of Earth in 240 B.C.? A) by observing the duration of a solar eclipse B) by measuring the size of Earth's shadow on the Moon in a lunar eclipse C) by comparing the maximum altitude of the Sun in two cities at different latitudes on the summer solstice D) by sending fleets of ships around Earth E) We don't know how he did it since all his writings were destroyed. Answer: C 2) Why did Ptolemy have the planets orbiting Earth on "circles upon circles" in his model of the universe? A) to explain why more distant planets take longer to make a circuit through the constellations of the zodiac B) to explain the fact that planets sometimes appear to move westward, rather than eastward, relative to the stars in our sky C) to explain why the Greeks were unable to detect stellar parallax D) to properly account for the varying distances of the planets from Earth E) to explain why Venus goes through phases as seen from Earth Answer: B

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3) Which of the following was an important reason why most ancient Greeks rejected the notion that the Earth orbits the Sun? A) They could not measure how big the Earth was. B) They weren't as smart as we are. C) They believed that the Sun is a God. D) They could not measure small changes in the positions of stars that occur as Earth orbits the Sun. Answer: D 4) During the Dark Ages in Europe, the scientific work of the ancient Greeks was preserved and further developed primarily by scholars in A) Baghdad (Iraq). B) Athens (Greece). C) Rome (Italy). D) Mumbai (India). E) Beijing (China). Answer: A 5) Which person below developed a system for predicting planetary positions that remained in use for some 1500 years? A) Tycho Brahe B) Copernicus C) Kepler D) Galileo E) Ptolemy Answer: E 6) The Greek philosopher Plato asserted that all heavenly objects move in perfect circles at constant speeds around the Earth. Which of the following observations most directly challenged this model? A) the apparent retrograde motion of planets B) the changing size of the Sun as the Earth gets closer and farther away C) solar eclipses D) seasonal changes in weather E) the differences in the lengths of shadows cast at different latitudes Answer: A 7) In terms of the history of science, we give special credit to the ancient Greeks because as far as is known, they A) were the first to seek natural explanations for what they observed. B) were the first to make written records of observations. C) were the first to be able to predict eclipses. D) were the first to write books. E) were the most technologically advanced civilization. Answer: A

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8) Tonight Mars is in the portion of its orbit where we see it undergoing apparent retrograde motion. Which statement is true?

A) Mars will be relatively bright in the night sky.

B) Mars will rise in the west and set in the east.

C) Mars will be visible in the night sky, but will appear much fainter than it does at other times.

D) Mars will not be visible because it is above the horizon only in the daytime.

Answer: A Section 3.3 1) Where was the Sun in Ptolemy's model of the universe?

A) at the center B) slightly offset from the center C) between Earth and the Moon's orbit D) between the orbits of Venus and Mars E) at the outer edge, beyond Saturn's orbit Answer: D 2) Which person below wrote a book, published in 1543 (the year of his death), suggesting that Earth and other planets orbit the Sun? A) Tycho Brahe B) Copernicus C) Kepler D) Galileo E) Ptolemy Answer: B 3) Which person below was the first to prove that comets lie beyond Earth's atmosphere?

A) Tycho Brahe B) Copernicus C) Kepler D) Galileo E) Aristotle Answer: A 4) Which person below discovered that the orbits of planets are ellipses?

A) Tycho Brahe B) Copernicus C) Kepler D) Galileo E) Ptolemy Answer: C

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5) Which person below did the following? He tried fitting perfect circles to Tycho's data, but in doing so found discrepancies of up to 8 arc minutes. Because he was confident that Tycho's data had uncertainties of only 1 arc minute, he abandoned perfect circles, which led him to a model using elliptical orbits.

A) Galileo B) Newton C) Copernicus D) Kepler Answer: D 6) Which person below discovered that Jupiter has moons?

A) Tycho Brahe B) Aristotle C) Kepler D) Galileo E) Ptolemy Answer: D 7) Which person below created a model of the solar system that put the Sun in the center, but that was not very accurate because he assumed that the orbits of the planets must be perfect circles?

A) Galileo B) Newton C) Copernicus D) Kepler E) Tycho Answer: C 8) Which person below angered the Pope with his assertion that the Earth moved around the Sun? A) Galileo B) Copernicus C) Kepler D) Tycho Answer: A 9) The point along a planet's orbit where it is closest to the Sun is called the orbit's A) perihelion.

B) aphelion.

C) eccentricity.

D) semimajor axis.

E) period.

Answer: A

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10) Kepler's second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, implies that A) a planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun. B) a planet's period does not depend on the eccentricity of its orbit. C) planets that are farther from the Sun move at slower average speeds than nearer planets. D) the period of a planet does not depend on its mass. E) planets have circular orbits. Answer: A 11) Kepler's third law, p2 = a3, implies that A) a planet's orbital period does not depend on the eccentricity of its orbit.

B) all orbits with the same semimajor axis have the same period.

C) the orbital period of a planet does not depend on its mass.

D) planets that are farther from the Sun move at slower average speeds than nearer planets.

E) All of the above are correct.

Answer: E 12) In its original form, Kepler's third law states that p2 = a3. What units must p and a use?

A) p must be years and a must be astronomical units.

B) p must be months and a must be astronomical units.

C) p must be years and a must be kilometers.

D) p must be days and a must be miles.

E) p must be months and a must be kilometers.

Answer: A 13) According to Kepler's third law (p2 = a3), a hypothetical planet that is twice as far from the Sun as Earth should have an orbital period of A) exactly 1/2 Earth year.

B) exactly 2 Earth years.

C) between 1 and 2 Earth years.

D) between 2 and 3 Earth years.

E) It depends on the planet's mass.

Answer: D 14) According to Kepler's third law (p2 = a3), an asteroid with an orbital period of 8 years lies at an average distance from the Sun equal to A) 2 astronomical units.

B) 4 astronomical units.

C) 8 astronomical units.

D) 16 astronomical units.

E) It depends on the asteroid's mass.

Answer: B

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15) According to Kepler's third law (p2 = a3), if a planet were discovered with an average distance from the Sun of 100 AU, its period would be A) 10,000 years B) 1000 years C) Not enough information to say D) 1 million years Answer: B 16) According to Kepler's third law (p2 = a3), how does a planet's mass affect its orbit around the Sun? A) A planet's mass has no effect on its orbit around the Sun. B) A more massive planet must have a larger semimajor axis.

C) More massive planets orbit the Sun at higher average speed.

D) More massive planets must have more circular orbits.

Answer: A 17) Imagine that Earth were instantly replaced in its orbit by a speck of dust. Which statement best describes the subsequent orbital motion of that piece of dust?

A) The dust particle will spiral into the Sun. B) The dust particle will be ejected from the solar system.

C) The dust particle will continue in the same orbit as the Earth did, orbiting the Sun in 1 year.

D) The dust particle will move to a smaller orbit and orbit the Sun in less than 1 year.

E) The dust particle will move to a larger orbit and orbit the Sun in more than 1 year.

Answer: C 18) Suppose an astronaut is working outside the Space Station and lets go off the handholds, so she is no longer attached to the Space Station in any way. Which of the following correctly explains what will happen?

A) Orbital speed does not depend on mass, so she will remain very close to the Space Station.

B) Her lower mass means she'll orbit much slower, so the Space Station will race rapidly away from her.

C) Her lower mass means she'll orbit much faster, so she will rapidly race ahead of the Space Station.

D) Because she is no longer attached to the orbiting Space Station, she'll rapidly lose altitude and fall back to Earth.

Answer: A 19) Which of the following statements about Kepler's laws is true?

A) Kepler's laws provide mathematical descriptions of the motion of the planets.

B) Kepler's laws explain how gravity is responsible for keeping planets in orbit around the Sun. C) Kepler's laws tell us the precise sizes and distances of all the planets.

D) All of the above are true.

Answer: A

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20) Which of the following statements best describes the accomplishments of these three people?

A) Newton collected the data, Tycho provided the model in the form of laws, Kepler explained the model in terms of gravity.

B) Tycho collected the data, Kepler provided the model in the form of laws, Newton explained the model in terms of gravity.

C) Kepler collected the data, Tycho provided the model in the form of laws, Newton explained the model in terms of gravity.

D) Tycho collected the data, Newton provided the model in the form of laws, Kepler explained the model in terms of gravity.

Answer: B 21) Which of the following was not observed by Galileo?

A) craters on the Moon B) stellar parallax C) sunspots D) Jupiter's moons E) phases of Venus Answer: B 22) In the Ptolemaic model of the solar system, which of the following phases could Venus exhibit?

A) new and crescent phases only B) gibbous and full phases only C) all phases D) Venus would not have phases in the Ptolemaic model.

Answer: A 23) Which of the following phases does Venus actually display as viewed from Earth?

A) new and crescent phases only B) gibbous and full phases only C) all phases D) Venus does not exhibit phases.

Answer: C 24) When we see Venus in its new phase, what phase would Earth be in as seen by a hypothetical person living on Venus?

A) full B) new C) first quarter D) third quarter E) waning crescent Answer: A

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25) Which of the following observations provided direct proof that Earth is not the center of all motion in the universe? A) the apparent retrograde motion of the planets B) the phases of the Moon C) eclipses of the Sun D) Galileo's observation of stars in the Milky Way E) Galileo's observations of the moons of Jupiter Answer: E Section 3.4 1) Which of the following statements about scientific models is true? A) A model tries to represent all aspects of nature. B) A model tries to represent only one aspect of nature. C) A model can be used to explain and predict real phenomena. D) All models that explain nature well are correct. E) All current models are correct. Answer: C 2) What do scientists mean by verifiable observations? A) statements that a person can, in principle, verify for himself or herself B) statements that anyone would agree are obvious C) observations that can be interpreted in only one way D) observations that a model does not have to predict E) observations that support a scientific theory Answer: A 3) What is meant by a hypothesis?

A) a natural phenomenon that requires explanation B) a tentative explanation for a phenomenon that can be tested with observations or experiments C) a confirmed explanation for a natural phenomenon D) a pseudoscientific idea E) a historical theory that has been proved inaccurate Answer: B 4) What is meant by Occam's Razor? A) the idea that a well-designed experiment can help us decide between two competing models B) the idea that scientific models should not invoke supernatural explanations C) the idea that scientists should prefer the simpler of two models that agree equally well with observations D) the fine line between science and pseudoscience E) the shaving implement of a medieval scholar Answer: C

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5) Which of the following statements expresses what we mean by a scientific theory?

A) a simple model that explains a wide variety of phenomena and that has survived repeated tests B) an explanation for a physical phenomenon, an explanation that hasn't been tested yet C) an educated guess D) a hypothesis Answer: A 6) Which of the following is not necessary of a good scientific theory?

A) A scientific theory must be proven true beyond all doubt to be accepted.

B) A scientific theory should be based on natural processes and should not invoke the supernatural or divine.

C) A scientific theory must explain a wide variety of phenomena observed in the natural world.

D) A scientific theory must make testable predictions that, if found to be incorrect, could lead to its own modification or demise.

Answer: A 7) Why do scientists consider Einstein's General Theory of Relativity to be a better theory of gravity than Newton's theory of gravity?

A) Einstein's gravity makes correct predictions in a few cases where Newton's theory does not.

B) The two theories always make very different predictions, and only Einstein's theory works.

C) Newton's theory was never useful, so it had to be replaced by something.

D) Einstein's theory is newer, and scientists always prefer newer theories.

Answer: A Section 3.5 1) The ancient goal of astrology was to A) understand the origin of Earth.

B) make a more accurate model of the universe.

C) predict the passing of the seasons.

D) predict human events.

E) antagonize astronomers.

Answer: D 2) Most horoscopes give advice such as "today is a good day to try new things." Is this a valid scientific prediction?

A) No. The statement is too vague to be objectively tested.

B) No. It is never a good day to try new things.

C) Yes. You can try something new and see if the outcome is good.

D) Yes. It is always a good day to try new things.

E) No. This statement is not true for everyone.

Answer: A

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3) An astrologer makes 100 predictions and 90 of them turn out to be true. Would this support the scientific validity of astrology?

A) only if the 90 correct predictions are significantly higher than what we would expect by chance B) yes, since 90 out of 100 is a very high number of correct predictions C) no, since the astrologer got 10 predictions wrong D) only if the astrologer can clearly explain how they made their predictions E) only if the astrologer used all of the planets to make their predictions Answer: A 4) There are 12 astrological "Sun signs," spaced evenly through the year. A person's astrological Sun sign is based on the constellation the Sun is in on the calendar day they were born (to be technical, if they were born on the same date about 2000 years ago). What is the chance that a person will correctly guess another person's Sun sign by random chance?

A) about 1 in 12 B) Zero: it would be impossible to guess correctly randomly.

C) about 1 in 100 D) about 1 in a million E) about 1 in 2 Answer: A General Chapter Questions 1) When did humans first confirm that Earth is not the center of the universe?

A) about 400 years ago B) about 2000 years ago C) around the time that early humans acquired language D) We haven't; there is still considerable scientific debate about whether Earth is the center of the universe.

Answer: A 2) Which of the following statements can in principle be tested by scientific experiment(s)?

A) War is morally justified.

B) Picasso was the best artist of his generation.

C) A supernatural being created the world.

D) The locations of the Sun and planets among the constellations at your birth predict your personality and health.

Answer: D 3) Which one of the following statements is testable by scientific methods?

A) Picasso was a better artist than Rembrandt.

B) Childhood vaccinations do not affect the rate of autism.

C) If Robert Kennedy had not been killed, he would have become president of the United States.

D) The universe was created by God. Answer: B

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4) In science, when we state that a measurement has "uncertainty," we mean A) we don't know the exact value of the measurement, but we can be very confident that it lies within some well-determined range.

B) we are uncertain of exactly what it is that we are measuring.

C) the measurement was unsuccessful, and we still have no idea what its true value might be.

D) the measurement may or may not be correct, and we can say nothing more about its validity.

Answer: A 5) Consider a set of ellipses that all have the same semimajor axis length. Which statement is true?

A) The ellipse with the largest distance between its foci has the greatest eccentricity.

B) The ellipse with the smallest distance between its foci has the greatest eccentricity.

C) All the ellipses must also have the same eccentricity.

D) All the ellipses must also have the same semiminor axis length.

E) All the ellipses must be identical.

Answer: A 6) Suppose that a study finds a strong positive correlation between acupuncture treatments and recovery of patients from, say, cocaine addiction. However, also assume that there is no known mechanism of action (i.e., how acupuncture could cure addiction) that can explain the correlation. Is it possible that acupuncture is responsible for the patients' recovery?

A) No. If there is no plausible mechanism of action, then acupuncture cannot be responsible for their healing.

B) Yes. Just because we don't understand the mechanism doesn't mean the process does not occur.

C) No. Acupuncture is not accepted by most medical doctors; therefore, it isn't effective.

D) Yes. If the patients got better, then the acupuncture must be effective.

Answer: B 7) Suppose that a study finds a strong positive correlation between acupuncture treatments and recovery of patients from, say, cocaine addiction. However, also assume that there is no known mechanism of action (i.e., how acupuncture could cure addiction) that can explain the correlation. Can we conclude that acupuncture is definitely responsible for the patients' recovery?

A) No. Acupuncture may be responsible for the healing, or it may not. Correlation does not necessarily imply causation.

B) Yes. If the study was run by qualified M.D.s, then we should respect their findings that acupuncture cured these patients.

C) No. Acupuncture is hippie, new age stuff, and is not respected by reputable doctors.

D) Yes. The patients stated afterwards that they knew it had helped, and these people know their own bodies better than we do.

Answer: A

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Short Answer Questions 1) Why was a knowledge of the stars so important to Polynesians?

Answer: The Polynesian people live on a group of widely separated islands in the South Pacific.

Knowledge of the stars allowed navigators to determine their latitude and direction, both essential for traveling the large distances from island to island.

2) Describe how Eratosthenes first measured the size of Earth over 2000 years ago.

Answer: Eratosthenes used measurements of the angle of the Sun in the sky at noon on the summer solstice in two places in Egypt. It was directly overhead in Syene and cast no shadows.

In Alexandria, however, there was a slight shadow, indicating that the Sun was 7 degrees away from overhead. Eratosthenes concluded that Alexandria lies at a latitude 7 degrees north of Syene. The circumference of Earth is then the distance between Syene and Alexandria divided by the fraction of the circle (7/360) that the two cities span.

3) Give a scientific explanation of the success of the central African rainfall-prediction technique of observing the waxing crescent Moon. Can the Moon's phase cause a change in rainfall?

Answer: The Moon's orientation varies seasonally, and so does the weather, so the orientation and the weather are correlated, but one does not cause the other.

4) Suppose you think you know the answer to a scientific question. Is it scientifically valid to look only for evidence to support your answer? Why or why not?

Answer: No, you must look for all evidence relating to your question, whether that evidence supports or refutes it. Looking only for supportive evidence is often called "cherry picking" of data to support an idea because it ignores evidence that may refute it.

Reading Quiz Questions 1) What practical value did astronomy offer to ancient civilizations?

A) It helped them keep track of time and seasons, and it was used by some cultures for navigation.

B) It allowed them to predict eclipses with great accuracy.

C) It helped them understand our cosmic origins.

D) It helped them find uses for ancient structures like Stonehenge.

Answer: A 2) Scientific thinking is A) based on everyday ideas of observation and trial-and-error experiments.

B) completely different from any other type of thinking.

C) a difficult process that only a handful of people can do well.

D) an ancient mode of thinking first invented in Egypt.

Answer: A

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3) The names of the 7 days of the week are based on A) the names of the seven planets closest to the Sun. B) the seven most prominent constellations in the summer sky. C) the names of prophets in the Bible. D) the seven naked-eye objects that appear to move among the constellations. Answer: D 4) The fact that the lunar phases repeat on the same solar dates about every 19 years (the Metonic cycle) can be used to A) keep lunar calendars approximately synchronized with solar calendars. B) predict the future orientation of the Earth's axis in space. C) keep the dates of solstices and equinoxes about the same from year to year. D) predict the dates of future eclipses. Answer: A 5) Ptolemy was important in the history of astronomy because he A) developed a model of the solar system that made sufficiently accurate predictions of planetary positions to remain in use for many centuries.

B) developed the first scientific model of the universe. C) was the first to create a model of the solar system that placed the Sun rather than the Earth at the center. D) was the first to believe that all orbits are perfect circles. Answer: A 6) The ancient Greeks get a lot of attention for their contributions to science because A) they were the first people known to try to explain nature with models based on reason and mathematics, without resorting to the supernatural. B) the books of every other culture were lost in the destruction of the library of Alexandria. C) they were the first people to realize that Earth is a planet orbiting the Sun. D) they were the only ancient culture that kept written records of their astronomical observations. Answer: A 7) What do we mean by a geocentric model of the universe? A) a model designed to explain what we see in the sky while having the Earth located in the center of the universe B) a model designed to explain what we see in the sky while having the Earth orbit the Sun C) It is the name given to sphere-shaped models that show all the constellations as they appear in our sky on the celestial sphere. D) a model of the Milky Way Galaxy that has our solar system located at its center Answer: A

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8) What was the Ptolemaic model?

A) an Earth-centered model of planetary motion published by Ptolemy B) the Earth-centered model of the cosmos in which the Earth was surrounded by seven perfect spheres, one each for the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn C) the first scientific model to successfully predict solar and lunar eclipses D) a Sun-centered model of planetary motion published by Ptolemy Answer: A 9) The great contribution of Nicholas Copernicus was to A) create a detailed model of our solar system with the Sun at the center.

B) prove that the Earth is not the center of the universe.

C) discover the laws of planetary motion.

D) discover the law of gravity.

Answer: A 10) The great contribution of Tycho Brahe was to A) observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion.

B) discover four moons orbiting Jupiter, thereby lending strong support to the idea that the Earth is not the center of the universe.

C) offer the first detailed model of a Sun-centered solar system, thereby beginning the process of overturning the Earth-centered model of the Greeks.

D) discover that planets orbit the Sun in elliptical orbits with varying speed.

Answer: A 11) Which of the following was not observed by Galileo?

A) stellar parallax B) mountains and valleys on the Moon C) four moons orbiting Jupiter D) phases of Venus Answer: A 12) Which of the following statements about an ellipse is not true?

A) The focus of an ellipse is always located precisely at the center of the ellipse.

B) A circle is considered to be a special type of ellipse.

C) The semimajor axis of an ellipse is half the length of the longest line that you can draw across an ellipse.

D) An ellipse with a large eccentricity looks much more elongated (stretched out) than an ellipse with a small eccentricity.

Answer: A

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13) Which of the following is not one of, nor a direct consequence of, Kepler's Laws?

A) The force of attraction between any two objects decreases with the square of the distance between their centers.

B) As a planet moves around its orbit, it sweeps out equal areas in equal times.

C) The orbit of each planet about the Sun is an ellipse with the Sun at one focus.

D) More distant planets orbit the Sun at slower speeds.

E) A planet or comet in a noncircular orbit travels faster when it is nearer to the Sun and slower when it is farther from the Sun. Answer: A 14) Scientific models are used to A) present the scale of the solar system to the general public.

B) make specific predictions that can be tested through observations or experiments.

C) make miniature representations of the universe.

D) prove that past paradigms no longer hold true.

Answer: B 15) Which of the following claims can be tested by scientific means?

A) People born when the Sun appears in the constellation Leo have larger average incomes than other people.

B) Abraham Lincoln's final thoughts were about the fate of his country.

C) God exists.

D) Blue is the best color for walls.

Answer: A 16) In science, a broad idea that has been repeatedly verified so as to give scientists great confidence that it represents reality is called a A) paradigm.

B) hypothesis.

C) Ptolemaic model.

D) theory.

Answer: D 17) Which of the following best describes how modern astronomers view astrology?

A) Astrology played an important part in the development of astronomy in ancient times, but it is not a science by modern standards.

B) Astrology is a synonym for astronomy.

C) Astrology was a great idea until it was disproved by the work of Copernicus, Tycho, Kepler, and Galileo.

D) Astrology is new age mumbo-jumbo that was a waste of time when it was invented thousands of years ago and remains a waste of time today.

Answer: A

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Concept Quiz Questions 1) Suppose the planet Uranus were much brighter in the sky, so that it was as easily visible to the naked eye as Jupiter or Saturn. Which one of the following statements would most likely be true in that case?

A) A week would have 8 days instead of 7.

B) Its brightness would make it possible to read by starlight at night.

C) Its gravity would cause the tides to be much higher than they actually are.

D) The discovery that the Earth is a planet going around the Sun would have come hundreds of years earlier.

E) Its slow motion through the sky would have led it to be named after the Goddess of Procrastination.

Answer: A 2) How does a 12-month lunar calendar differ from our 12-month solar calendar?

A) It has about 11 fewer days.

B) It does not have seasons.

C) Its new year always occurs in February instead of on January 1.

D) It uses a 23-hour rather than a 24-hour day.

Answer: A 3) Which of the following best describes a set of conditions under which archaeoastronomers would conclude that an ancient structure was used for astronomical purposes?

A) The structure has numerous features that align with the Sun's path at special times of year and cultural heritage claimed that the rulers were descendants of the Sun. B) They find that, looking out from the center of the building, there are two windows that align with the rise and set points of two bright stars.

C) The structure consists of lines in the desert that make patterns visible only from high above.

D) The structure has the same dome shape as modern astronomical observatories.

Answer: A 4) How did the Ptolemaic model explain the apparent retrograde motion of the planets?

A) The planets moved along small circles that moved on larger circles around the Earth.

B) The planets sometimes stopped moving and then reversed to move backward along their circular orbits.

C) The model showed that apparent retrograde motion occurs as Earth passes by another planet in its orbit of the Sun. D) The planets resided on giant spheres that sometimes turned clockwise and sometimes turned counterclockwise.

Answer: A

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5) When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not?

A) Copernicus used perfect circles for the orbits of the planets.

B) Copernicus placed the planets in the wrong order going outward from the Sun. C) Copernicus misjudged the distances between the planets.

D) Copernicus placed the Sun at the center but did not realize that the Moon orbits the Earth.

Answer: A 6) Earth is farthest from the Sun in July and closest to the Sun in January. During which Northern Hemisphere season is Earth moving fastest in its orbit?

A) spring B) summer C) fall D) winter Answer: D 7) According to Kepler's third law (p2 = a3), how does a planet's mass affect its orbit around the Sun? A) A planet's mass has no effect on its orbit around the Sun. B) More massive planets orbit the Sun at higher average speed.

C) More massive planets must have more circular orbits.

D) A more massive planet must have a larger semimajor axis.

Answer: A 8) All the following statements are true. Which one follows directly from Kepler's third law (p2 = a3)?

A) Venus orbits the Sun at a slower average speed than Mercury.

B) Venus is more massive than Mercury.

C) Venus takes longer to rotate than it does to orbit the Sun. D) Venus has a thicker atmosphere than Mercury.

Answer: A 9) Suppose a comet orbits the Sun on a highly eccentric orbit with an average (semimajor axis) distance of 1 AU. How long does it take to complete each orbit, and how do we know?

A) 1 year, which we know from Kepler's third law B) It depends on the eccentricity of the orbit, as described by Kepler's second law.

C) It depends on the eccentricity of the orbit, as described by Kepler's first law.

D) Each orbit should take about 2 years because the eccentricity is so large.

Answer: A 10) Galileo challenged the idea that objects in the heavens were perfect by A) showing that heavy objects fall at the same rate as lighter objects.

B) observing sunspots on the Sun and mountains on the Moon.

C) proving Kepler's laws were correct.

D) inventing the telescope.

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11) Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun? A) phases of Venus B) four moons of Jupiter C) patterns of shadow and sunlight near the dividing line between the light and dark portions of the Moon's face D) The Milky Way is composed of many individual stars.

Answer: A 12) Which of the following is not consistent with the major hallmarks of science?

A) Science consists of proven theories that are understood to be true explanations of reality.

B) Scientific explanations should be based solely on natural causes.

C) Science progresses through the creation and testing of models that explain observation as simply as possible.

D) A scientific model must make testable predictions.

Answer: A 13) Which of the following is not part of a good scientific theory?

A) A scientific theory cannot be accepted until it has been proven true beyond all doubt.

B) A scientific theory must make testable predictions that, if found to be incorrect, could lead to its own modification or demise.

C) A scientific theory must explain a wide variety of phenomena observed in the natural world.

D) A scientific theory should be based on natural processes and should not invoke the supernatural or divine.

Answer: A 14) Only one of the statements that follow uses the term theory in its correct, scientific sense.

Which one?

A) Einstein's theory of relativity has been tested and verified thousands of times.

B) Evolution is only a theory, so there's no reason to think it really happened.

C) I have a new theory about the cause of earthquakes, and I plan to start testing it soon.

D) I wrote a theory that is 152 pages long.

Answer: A 15) Which of these hypothetical observations (none of them are real) would force us to reconsider our modern, Sun-centered view of the solar system?

A) We discover a small planet beyond Saturn that rises in the west and sets in the east each day.

B) We discover an Earth-sized planet orbiting the Sun beyond the orbit of Pluto.

C) We find that we are unable to measure any parallax for a distant galaxy.

D) We discover that the universe is actually contracting, not expanding.

Answer: A

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16) The astrology practiced by those who cast predictive horoscopes can be tested by A) comparing how often the predictions come true to what would be expected by pure chance B) asking astrologers if it works C) polling people to find out what percentage believe their horoscopes to be accurate D) counting how many times the predictions come true Answer: A Visual Quiz Questions 1) Central Africans learned long ago to use observations of the waxing crescent moon (once each month) to predict when the rainy season was coming. Use the graph for Central Africa. In what month(s) does this region get about 200 millimeters of rainfall?

A) April and August B) July C) February and October D) June and July E) March through June Answer: A

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2) Each of these photos shows an ancient structure used for astronomical purposes. Which one is located in the United States?

A)

B)

C)

D)

Answer: D

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3) This figure shows the circle on circle motion of a planet in the Ptolemaic model. At which point(s) is the planet in the middle of its period of retrograde motion in our sky?

A) point 1 only B) point 2 only C) point 3 only D) points 1 and 3 Answer: B 4) This figure shows the circle on circle motion of a planet in the Ptolemaic model. At which point(s) is the planet in the middle of its period of retrograde motion in our sky?

A) 1 B) 2 C) 3 D) 4 Answer: D

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5) What, if anything, is wrong with the planetary orbit shown?

A) The Sun is not at one focus, as Kepler's first law requires.

B) The shape of the orbit is not an ellipse, as Kepler's first law requires.

C) The orbital path violates Kepler's third law.

D) There is nothing wrong with this orbit; it is fine as shown.

Answer: A 6) This diagram shows a planet at four points in its orbit around the Sun. At which of the points shown is it traveling slowest in its orbit? (The planet is not real, as all the planets of our solar system have orbits much more circular than the one shown.)

A) 1 B) 2 C) 3 D) 4 Answer: D

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7) Assume you knew nothing else about the planets but what is shown in this diagram. What could you conclude?

A) The square of a planet's period in years is equal to the cube of its average distance from the Sun in AU. B) Earth takes less than a third as long to orbit the Sun as Mars.

C) The outer planets are more massive than the inner planets.

D) Saturn orbits the Sun faster than any other planet.

Answer: A

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8) This diagram shows a graphical interpretation of Kepler's third law. Suppose there were a planet in our solar system that orbited the Sun with an average speed of 11 km/s. In terms of its average distance, this planet would be located

A) between Jupiter and Saturn.

B) beyond the orbit of Saturn.

C) between Venus and Mars.

D) between Mars and Jupiter.

E) It is impossible to determine from the information given.

Answer: A 9) Look carefully at this telescopic photo of the Moon. All the following statements are true.

Which one is proved by the fact that the line dividing the dark and bright regions is not perfectly straight?

A) The Moon's surface is not perfectly smooth but rather has mountains and valleys.

B) The Moon goes around the Earth.

C) This is a first-quarter moon.

D) Some parts of the Moon's surface are darker in color than others.

Answer: A

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10) Study this diagram, which shows why we see phases of Venus, as first observed by Galileo.

When should we expect to see a full Venus in our night sky?

A) never B) at midnight, when Venus is on the opposite side of its orbit from Earth C) at midnight, when Venus is on the same side of its orbit from Earth D) only when Earth is at the opposite side of the Sun from what is shown in this diagram Answer: A

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

Study the two graphs above, based on Figure 3.19. Use the information in the graphs to answer the following questions.

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1) Approximately how fast is Jupiter orbiting the Sun? A) This cannot be determined from the information provided. B) 20 km/s C) 10 km/s D) a little less than 15 km/s Answer: D 2) An asteroid with an average orbital distance of 2 AU will orbit the Sun at an average speed that is A) a little slower than the orbital speed of Mars.

B) a little faster than the orbital speed of Mars.

C) the same as the orbital speed of Mars.

Answer: A 3) Uranus, not shown on graph b, orbits about 19 AU from the Sun. Based on the graph, its approximate orbital speed is between about A) 20 and 25 km/s.

B) 15 and 20 km/s.

C) 10 and 15 km/s.

D) 5 and 10 km/s.

Answer: D 4) Kepler's third law is often stated as p2 = a3. The value a3 for a planet is shown on A) the horizontal axis of graph a.

B) the vertical axis of graph a.

C) the horizontal axis of graph b.

D) the vertical axis of graph b.

Answer: A 5) On graph a, you can see Kepler's third law (p2 = a3) from the fact that A) the data fall on a straight line.

B) the axes are labeled with values for p2 and a3.

C) the planet names are labeled on the graph.

Answer: A 6) Suppose graph a showed a planet on the red line directly above a value of 1000 AU3 along the horizontal axis. On the vertical axis, this planet would be at A) 1000 years2.

B) 10002 years2. years2.

C) D) 100 years.

Answer: A

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7) How far does the planet in question 6 orbit from the Sun? A) 10 AU B) 100 AU C) 1000 AU D) AU Answer: A Chapter Review Questions 1) In what way is scientific thinking natural to all of us, and how does modern science build upon this everyday type of thinking?

2) Why did ancient peoples study astronomy? Describe an astronomical achievement of at least three ancient cultures.

3) Describe the astronomical origins of our day, week, month, and year.

4) What is a lunar calendar? How can it be kept roughly synchronized with a solar calendar?

5) What do we mean by a model in science?

6) Summarize the development of the Greek geocentric model through Ptolemy. How did the Ptolemaic model account for apparent retrograde motion?

7) What was the Copernican revolution, and how did it change the human view of the universe?

8) What is an ellipse? Define its foci, semimajor axis, and eccentricity.

9) State and explain the meaning of each of Kepler's laws of planetary motion.

10) Describe the three hallmarks of science and how we can see them in the Copernican revolution. What is Occam's razor? Why doesn't science accept personal testimony as evidence?

11) What is the difference between a hypothesis and a theory in science?

12) What is the basic idea behind astrology? Explain why this idea seemed reasonable in ancient times but is no longer accepted by scientists.

Science or Nonscience?

Decide whether the claim made in each of the following statements could be evaluated scientifically or falls into the realm of nonscience. Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.

13) The Yankees are the best baseball team of all time.

14) Several kilometers below its surface, Jupiter's moon Europa has an ocean of liquid water.

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15) My house is haunted by ghosts who make the creaking noises I hear each night.

16) There are no lakes or seas on the surface of Mars today.

17) Dogs are smarter than cats.

18) Children born when Jupiter is in the constellation Taurus are more likely to be musicians than other children.

19) Aliens can manipulate time and memory so that they can abduct and perform experiments on people who never realize they were taken.

20) Newton's law of gravity works as well for explaining orbits of planets around other stars as it does for explaining orbits of the planets in our own solar system.

21) God created the laws of motion that were discovered by Newton.

22) A huge fleet of alien spacecraft will land on Earth and introduce an era of peace and prosperity on January 1, 2035.

Quick Quiz 23) In the Greek geocentric model, the retrograde motion of a planet occurs when A) Earth is about to pass the planet in its orbit around the Sun. B) the planet actually goes backward in its orbit around Earth.

C) the planet is aligned with the Moon in our sky.

Answer: No Correct Answer Was Provided.

24) Which of the following was not a major advantage of Copernicus's Sun-centered model over the Ptolemaic model?

A) It made significantly better predictions of planetary positions in our sky.

B) It offered a more natural explanation for the apparent retrograde motion of planets in our sky.

C) It allowed calculation of the orbital periods and distances of the planets.

Answer: No Correct Answer Was Provided.

25) When we say that a planet has a highly eccentric orbit, we mean that A) it is spiraling in toward the Sun. B) its orbit is an ellipse with the Sun at one focus.

C) in some parts of its orbit it is much closer to the Sun than in other parts.

Answer: No Correct Answer Was Provided.

26) Earth is closer to the Sun in January than in July. Therefore, in accord with Kepler's second law A) Earth travels faster in its orbit around the Sun in July than in January.

B) Earth travels faster in its orbit around the Sun in January than in July.

C) it is summer in January and winter in July.

Answer: No Correct Answer Was Provided.

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27) According to Kepler's third law A) Mercury travels fastest in the part of its orbit in which it is closest to the Sun. B) Jupiter orbits the Sun at a faster speed than Saturn. C) all the planets have nearly circular orbits. Answer: No Correct Answer Was Provided. 28) Tycho Brahe's contribution to astronomy included A) inventing the telescope. B) proving that Earth orbits the Sun. C) collecting data that enabled Kepler to discover the laws of planetary motion. Answer: No Correct Answer Was Provided. 29) Galileo's contribution to astronomy included A) discovering the laws of planetary motion. B) discovering the law of gravity. C) making observations and conducting experiments that dispelled scientific objections to the Sun-centered model. Answer: No Correct Answer Was Provided. 30) Which of the following is not true about scientific progress? A) Science progresses through the creation and testing of models of nature. B) Science advances only through the scientific method. C) Science avoids explanations that invoke the supernatural. Answer: No Correct Answer Was Provided. 31) Which of the following is not true about a scientific theory? A) A theory must explain a wide range of observations or experiments. B) Even the strongest theories can never be proved true beyond all doubt. C) A theory is essentially an educated guess. Answer: No Correct Answer Was Provided. 32) When Einstein's theory of gravity (general relativity) gained acceptance, it demonstrated that Newton's theory had been A) wrong. B) incomplete. C) really only a guess. Answer: No Correct Answer Was Provided.

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Inclusive Astronomy Use these questions to reflect on participation in science.

33) Group Discussion: Ancestral Astronomy.

No matter what your background, you had ancestors who watched the sky and observed how celestial objects move through it. a) Working independently, choose a particular branch of your ancestry to explore, then gather historical information dating back as far as possible (ideally at least several centuries) about how and why your ancestors made use of their observations of the sky. b) Gather in small groups (two to four students) and take turns sharing what you learned through your research. Be clear about the ancestral group you have chosen and the time period your research covers. c) Make a list of the major uses of astronomical knowledge that your group members found, categorizing the uses as practical, ceremonial/religious, or other. Which uses were most common? Do you see any noticeable differences among the cultures? d) Discuss how cultural or geographical factors may have influenced the astronomical knowledge of these different ancestral groups.

The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

34) What Makes It Science?Choose a single idea in the modern view of the cosmosas discussed in Chapter 1, such as "The universe is expanding," "The universe began with a Big Bang," "We are made from elements manufactured by stars," or "The Sun orbits the center of the Milky Way Galaxy once every 230 million years." a) Describe how this idea reflects each of the three hallmarks of science, discussing how it is based on observations, how our understanding of it depends on a model, and how that model is testable. b) Describe a hypothetical observation that, if it were actually made, might cause us to call the idea into question. Then briefly discuss whether you think that, overall, the idea is likely or unlikely to hold up to future observations.

35) The Importance of Ancient Astronomy. Why was astronomy important to people in ancient times? Discuss both the practical importance of astronomy and the importance it may have had for religious, ceremonial, or philosophical traditions. Which of those roles (practical or religious/ceremonial/philosophical) do you think was more important in leading to the development of modern astronomy? Defend your opinion.

36) The Impact of Science. The modern world is filled with ideas, knowledge, and technology that developed through science and application of the scientific method. Discuss some of these things and how they affect our lives. Which of these impacts do you think are positive? Which are negative? Overall, do you think science has benefited the human race? Defend your opinion.

37) Astronomy and Astrology. Why do you think astrology remains so popular around the world even though it has failed all scientific tests of its validity? Do you think the popularity of astrology has any positive or negative social consequences? Defend your opinions.

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38) Group Activity: Galileo on Trial. Conduct a mock trial in which you consider the following three pieces of evidence: (1) observations of mountains and valleys on the Moon; (2) observations of moons orbiting Jupiter; (3) observations of the phases of Venus. Note: This activity works particularly well in groups of four or more students, in which • One student takes the role of Galileo, arguing in favor of the idea that Earth orbits the Sun. • One student takes the role of Prosecutor, arguing against the idea that Earth orbits the Sun. • The remaining students serve as a jury and render a verdict after hearing the arguments and rebuttals from Galileo and the prosecutor.

Investigate Further 39) Earth's Shape. It took thousands of years for humans to deduce that Earth is spherical. For each of the following alternative models of Earth's shape, identify one or more observations that you could make for yourself that would invalidate the model. a) A flat Earth b) A football-shaped Earth c) A cylindrical Earth, like that proposed by Anaximander 40) Lunar Calendars. a) Find the dates of the Jewish festival of Chanukah for this year and the next three years. Based on what you have learned in this chapter, explain why the dates change as they do. b) Find the dates of the Muslim fast for Ramadan for this year and the next three years. Based on what you have learned in this chapter, explain why the dates change as they do.

41) Copernican Players. Using a bulleted-list format, make a one-page "executive summary" of the major roles that Copernicus, Tycho, Kepler, and Galileo played in overturning the ancient belief in an Earth-centered universe.

42) Easter Timing. Research when different denominations of Christianity celebrate Easter and why they use different dates. Summarize your findings in a one- to two-page report.

43) Greek Astronomers. Many ancient Greek scientists had ideas that, in retrospect, seem well ahead of their time. Choose one ancient Greek scientist to study, and write a one- to two-page "scientific biography" of your chosen person.

44) Influence on History. Based on what you have learned about the Copernican revolution, write a one- to two-page essay about how you believe it altered the course of human history.

45) Cultural Astronomy. Choose a particular culture of interest to you, and research the astronomical knowledge and accomplishments of that culture. Write a two- to three-page summary of your findings.

46) Astronomical Structures. Choose an ancient astronomical structure of interest to you (e.g., Stonehenge, Templo Mayor, Pawnee lodges), and research its history. Write a two- to three-page summary of your findings. If possible, also build a scale model of the structure or create detailed diagrams to illustrate how the structure was used.

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Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

47) The Metonic Cycle.The length of our calendar year is 365.2422 days, and the Moon's monthly cycle of phases averages 29.5306 days in length. By calculating the number of days in each, confirm that 19 solar years is almost precisely equal to 235 cycles of the lunar phases.

Show your work clearly; then write a few sentences explaining how this fact can be used to keep a lunar calendar roughly synchronized with a solar calendar.

48) Chinese Calendar. The traditional Chinese lunar calendar has 12 months in most years but adds a 13th month to 22 of every 60 years. How many days does this give the Chinese calendar in each 60-year period? How does this compare to the number of days in 60 years on a solar calendar? Based on your answers, explain how this scheme is similar to the scheme used by lunar calendars that follow the Metonic cycle. (Hint: You'll need the data given in Problem 47.)

49) Method of Eratosthenes I. You are an astronomer on planet Nearth, which orbits a distant star. It has recently been accepted that Nearth is spherical in shape, though no one knows its size.

One day, while studying in the library of Alectown, you learn that on the equinox your sun is directly overhead in the city of Nyene, located 1000 kilometers due north of you. On the equinox, you go outside and observe that the altitude of your sun is 80°. What is the circumference of Nearth? (Hint: Apply the technique used by Eratosthenes to measure Earth's circumference.)

50) Method of Eratosthenes II. You are an astronomer on planet Tirth, which orbits a distant star.

It has recently been accepted that Tirth is spherical in shape, though no one knows its size. One day, you learn that on the equinox your sun is directly overhead in the city of Tyene, located 400 kilometers due north of you. On the equinox, you go outside and observe that the altitude of your sun is 86°. What is the circumference of Tirth? (Hint: Apply the technique used by Eratosthenes to measure Earth's circumference.)

51) Mars Orbit. Find the perihelion and aphelion distances of Mars. (Hint: You'll need data from Appendix E.) 52) Eris Orbit. The dwarf planet Eris orbits the Sun every 557 years. What is its average distance (semimajor axis) from the Sun? How does its average distance compare to that of Pluto?

53) New Planet Orbit. A newly discovered planet orbits a distant star with the same mass as the Sun at an average distance of 112 million kilometers. Its orbital eccentricity is 0.3. Find the planet's orbital period and its nearest and farthest orbital distances from its star.

54) Halley Orbit. Halley's Comet orbits the Sun every 76.0 years and has an orbital eccentricity of 0.97. a) Find its average distance from the Sun (semimajor axis). b) Find its perihelion and aphelion distances.

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The Cosmic Perspective, 9e (Bennett et al.)

Chapter 4 Making Sense of the Universe Section 4.1 1) Which of the following is an example in which you are traveling at constant speed, but not at constant velocity?

A) rolling freely down a hill in a cart, traveling in a straight line B) driving backward at exactly 50 km/hr C) driving around in a circle at exactly 100 km/hr D) jumping up and down exactly 60 times per minute E) none of the above Answer: C 2) Which of the following correctly states the value and units of the acceleration of gravity on Earth?

A) 9.8 m/s2 B) 9.8 m/s C) 9.8 km/s2 D) 9.8 m2/s E) 9.8 km/s Answer: A 3) Momentum is defined as A) mass times speed.

B) mass times velocity.

C) force times velocity.

D) mass times acceleration.

E) force times acceleration.

Answer: B 4) If an object's velocity is doubled, its momentum is A) halved.

B) unchanged.

C) doubled.

D) quadrupled.

E) dependent on its acceleration.

Answer: C 5) As long as an object is not gaining or losing mass, a net force on the object will cause a change in A) acceleration.

B) direction.

C) weight.

D) speed.

E) velocity.

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6) If your mass is 60 kilograms on Earth, what would your mass be on the Moon?

A) 10 pounds B) 10 kilograms C) 360 kilograms D) 60 kilograms E) 60 pounds Answer: D 7) In which of the following cases would you feel weightless?

A) while walking on the Moon B) while falling from an airplane with your parachute open C) while traveling through space in an accelerating rocket D) while falling from a roof E) none of the above Answer: D 8) Under what conditions is an object weightless? (Ignore effects of air resistance.)

A) when it is in free-fall B) when it is on the Moon C) when it is detached from Earth's surface (such as in an airplane) D) when it is moving in at constant velocity Answer: A 9) Astronauts are weightless inside the International Space Station because A) the station and the astronauts are constantly falling toward Earth.

B) the station has rockets that fire to counteract Earth's gravity.

C) there is no gravity in space.

D) the station is too far from Earth for gravity to be noticeable.

Answer: A 10) You are standing on a scale in an elevator and notice that your weight is lower than your normal weight. What do you conclude is occurring?

A) The elevator is accelerating upward.

B) The elevator is moving at a constant velocity upward.

C) The elevator is accelerating downward.

D) The elevator is moving at a constant velocity downward.

E) Your diet is working.

Answer: C 11) Two bowling balls with different masses are dropped from the same height. How do their accelerations compare?

A) The heavier bowling ball accelerates faster.

B) They both fall with the same acceleration.

C) The lighter bowling ball accelerates faster.

Answer: B

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12) You conduct the following three ball drops, in each case measuring the time it takes for the ball to fall to the ground; the mass is the mass of the ball and the height is the height from which you drop the ball: Ball Drop 1. Mass 0.5 kilograms, height 20 meters Ball Drop 2. Mass 5.0 kilograms, height 20 meters Ball Drop 3. Mass 0.5 kilograms, height 30 meters Which pair of ball-drops will best test whether mass affects the acceleration of gravity? A) ball drops 2 and 3 B) ball drops 1 and 3 C) ball drops 1 and 2 Answer: C 13) How could you test the hypothesis that the acceleration of gravity does not depend on mass? (Ignore effects of air resistance.) A) Drop two objects with the same mass from the same height. B) Drop two objects with the same mass from different heights. C) Drop two objects with different masses from the same height. D) Drop two objects with different masses from different heights. Answer: C 14) Suppose you drop a feather and a hammer on the Moon from the same height at the same time. What will happen? A) The feather will hit the ground first. B) They will hit the ground at the same time. C) The hammer will hit the ground first. D) They will float at the height you release them. Answer: B 15) Suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen? A) The 10-pound weight will hit the ground before the 5-pound weight. B) Both will hit the ground at the same time. C) Both weights will float freely, since everything is weightless on the Moon. Answer: B Section 4.2 1) Suppose an object is moving in a straight line at 50 miles/hr. According to Newton's first law of motion, the object will A) continue to move in a straight line at 50 miles/hr forever, no matter what happens. B) continue to move in a straight line at 50 miles/hr until it is acted upon by a net force. C) eventually slow down and come to a stop. D) continually slow down, but never quite come to a complete stop. Answer: B

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2) You observe an object to be moving in a straight line at a constant speed. What can you conclude? (Assume the object does not have any engines or other power source.) A) The net force acting on the object is zero. B) No forces of any kind are acting on the object. C) The only force acting on the object is gravity. D) The only force acting on the object is air resistance. E) Some unseen force must be keeping the object in motion. Answer: A 3) An astronaut in space swings a ball attached to a string in a circular motion. If the string suddenly breaks, how will the ball move? A) It will move in a straight line in whichever direction it was moving when the string broke. B) It will continue to move in the same circular path it had been following before the string broke. C) It will instantly come to a stop. D) It will move toward the astronaut. E) It will move in a large elliptical path around the astronaut. Answer: A 4) Consider Newton's second law states, often written as force = mass × acceleration. Based on this law, what property can you determine if you observe the acceleration of an object with a known mass? A) the net force acting on the object B) the strength of gravity acting on the object C) the current velocity of the object D) the current location of the object Answer: A 5) Consider Newton's second law states, often written as force = mass × acceleration. If a known force is applied to an object with a known mass, what does this law predict for the object's acceleration? A) acceleration = mass × force B) acceleration = mass / force C) acceleration = force / mass D) Newton's second law is irrelevant for solving this problem. Answer: C 6) If a net force is applied to an object, what is guaranteed to change? A) the object's momentum B) the object's speed C) the object's direction of motion D) the object's mass E) the object's weight Answer: A

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7) The idea that we live in a universe (literally, "one story"), in which the same law of gravity applies both on Earth and in space, was established through the work of A) Newton.

B) Copernicus.

C) Kepler.

D) Galileo.

Answer: A 8) Which person realized the laws of gravity applied to objects both on Earth and in space?

A) Newton B) Copernicus C) Kepler D) Galileo Answer: A 9) The Earth exerts a gravitational force on a person standing on the surface. The person also exerts a gravitational force on the Earth. Based on Newton's third law of motion, how do these two forces compare?

A) The forces exerted by the Earth and the person are the same.

B) The Earth exerts a much stronger force than the person.

C) The person exerts a much stronger force than the Earth.

D) The Earth exerts a slightly stronger force than the person.

E) The person exerts a slightly stronger force than the Earth.

Answer: A Section 4.3 1) How does a rocket take off?

A) Its rocket engines push against the launch pad, propelling the rocket upward.

B) It converts mass-energy to kinetic energy.

C) It achieves lift from its wings in the same way that airplanes do.

D) Hot gas shoots out from the back of the rocket and, by conservation of momentum, the rocket moves in the opposite direction.

E) The hot rocket exhaust expands the air beneath the rocket, propelling it forward.

Answer: D 2) How does a rocket launch upward? Choose the statement that correctly answers the question.

A) By expelling gas downward, the rocket is propelled upward.

B) Expelling gas downward, which by pushing against the ground, propels the rocket upward.

Answer: A

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3) Angular momentum depends upon A) mass and velocity.

B) mass, velocity, and radius.

C) force and radius.

D) force, velocity, and radius.

E) momentum and angular velocity.

Answer: B 4) Which law explains why a skater can spin faster by pulling his arms closer to his body, or spin slower by spreading his arms out?

A) the law of gravity B) Newton's third law of motion C) the law of conservation of momentum D) the law of conservation of angular momentum E) the law of conservation of energy Answer: D 5) Suppose the Sun were to suddenly shrink in size but its mass remained the same. According to the law of conservation of angular momentum, what would happen?

A) The Sun's angular size in our sky would increase.

B) The Sun's rate of rotation would slow.

C) The Sun's rate of rotation would remain the same.

D) The Sun rate of rotation would increase.

Answer: D 6) Which of the following is not a conserved quantity?

A) energy B) momentum C) angular momentum D) radiation Answer: D 7) Which of the following is the standard international unit for measuring energy?

A) Kelvin B) joule C) watt D) newton E) meter Answer: B 8) Radiative energy is A) heat energy.

B) energy from nuclear power plants.

C) energy carried by light.

D) energy used to power home radiators.

E) energy of motion.

Answer: C

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9) Gasoline can be used to power cars because it has A) gravitational potential energy. B) chemical potential energy. C) electrical potential energy. D) kinetic energy. E) radiative energy. Answer: B 10) Which of the following has the most kinetic energy? A) a 4-ton truck moving 20 km/hr B) a 3-ton truck moving 30 km/hr C) a 2-ton truck moving 40 km/hr D) a 1-ton truck moving 50 km/hr E) A, B, C, and D all have the same kinetic energy. Answer: C 11) Which of the following represents the smallest range of temperatures? A) 50-100° Kelvin B) 50-100° Celsius C) 50-100° Fahrenheit D) They all represent the same range in temperature. Answer: C 12) What does temperature measure? A) the average mass of particles in a substance B) the average size of particles in a substance C) the average kinetic energy of particles in a substance D) the total number of particles in a substance E) the total potential energy of particles in a substance Answer: C 13) On a hot day, molecules of air ________ than on a cold day. A) move faster on average B) move slower on average C) are more massive D) are less massive E) contain more atoms Answer: A 14) The amount of gravitational potential energy released as an object falls depends on A) its mass, the distance it falls, and the acceleration of gravity. B) its mass and its speed at the time it begins falling. C) its mass and its speed when it hits the ground. D) only its mass and the acceleration of gravity. E) only the acceleration of gravity. Answer: A

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15) In the formula E = mc2, what does E represent?

A) the kinetic energy of a moving object B) the radiative energy carried by light C) the gravitational potential energy of an object held above the ground D) the mass-energy or potential energy stored in an object's mass E) the electric charge of the object Answer: D 16) According to Einstein's equation, E = mc2, which of the following statements is true?

A) Mass can be turned into energy, but energy cannot be turned back into mass.

B) It takes a large amount of mass to produce a small amount of energy.

C) A small amount of mass can be turned into a large amount of energy.

D) Mass can be turned into energy if it is accelerated to the speed of light.

E) One kilogram of mass represents 1 joule of energy.

Answer: C 17) Which of the following statements correctly describes the law of conservation of energy?

A) An object always has the same amount of energy.

B) Energy can change between many different forms, such as potential, kinetic, and thermal, but it is ultimately destroyed.

C) Energy can change between many different forms, such as potential, kinetic, and thermal, but the total quantity of energy in the universe never changes.

D) The fact that you can fuse hydrogen into helium to produce energy means that helium can be turned into hydrogen to produce energy.

E) It is not really possible for an object to gain or lose potential energy because energy cannot be destroyed.

Answer: C 18) Where does your body get the energy it uses to make your heart beat?

A) It comes from the radiative energy of the sunlight that hits your skin.

B) It comes from the chemical potential energy of the food you eat.

C) It comes from the thermal energy of the water you drink.

D) It comes from the kinetic energy of the molecules in the air that you breathe in.

E) It is created by your brain during the time that you rest or sleep.

Answer: B

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19) Based on fundamental laws of motion and gravity, which of the following best explains why Kepler's second law (planets move faster in the parts of their orbit that are closer to the Sun and slower when they are farther from the Sun) is true?

A) A planet's angular momentum must be conserved as it moves around its orbit.

B) The speed of a planet at any point in its orbit depends on its temperature, which varies with distance from the Sun. C) The strength of gravity is inversely proportional to the square of the distance between two objects.

D) The gravitational influence of other planets determines the speed of any particular planet's orbit.

Answer: A 20) As an interstellar gas cloud shrinks in size, the law of conservation of angular momentum predicts it will A) heat up.

B) slow down in its rotation.

C) cool off.

D) continue shrinking.

E) rotate faster.

Answer: E 21) How does a comet's orbital angular momentum vary over its orbit?

A) Its angular momentum is greatest when the comet is closest to the Sun. B) Its angular momentum is greatest when the comet is farthest away from the Sun. C) Its angular momentum is the same throughout its orbit.

Answer: C 22) When is a comet's orbital speed at its maximum?

A) when it is closest to the Sun B) when it is farthest from the Sun C) Its orbital speed does not change.

Answer: A 23) If a spinning star gets larger in diameter, what happens to its rotation rate?

A) It increases.

B) It will not change.

C) It decreases.

Answer: C 24) A comet has an elliptical orbit around the Sun. Its total orbital energy is A) greatest when it is farthest from the Sun. B) greatest when it is closest to the Sun. C) the same throughout its orbit.

Answer: C

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25) When a rock is held above the ground, we say it has some gravitational potential energy.

When we let it go, it falls and we say the gravitational potential energy is converted to kinetic energy. Finally, the rock hits the ground (and stays there). What has happened to the energy?

A) The rock keeps the energy inside it in the form of mass-energy.

B) The energy goes into the ground and, as a result, the orbit of Earth about the Sun is slightly changed.

C) It is transformed back into gravitational potential energy.

D) The energy goes to producing sound and to heating the ground, rock, and surrounding air.

Answer: D Section 4.4 1) According to the universal law of gravitation, the force due to gravity is A) directly proportional to the square of the distance between objects.

B) inversely proportional to the square of the distance between objects.

C) directly proportional to the distance between objects.

D) inversely proportional to the distance between objects.

E) not dependent on the distance between objects.

Answer: B 2) According to the universal law of gravitation, if the masses of both attracting objects double, then the gravitational force between them will A) not change at all.

B) increase by a factor of 2.

C) decrease by a factor of 2.

D) increase by a factor of 4.

E) decrease by a factor of 4.

Answer: D 3) Which orbital shapes are possible under the force of gravity?

A) ellipses only B) ellipses and spirals C) ellipses, parabolas, and hyperbolas D) ellipses, spirals, and parabolas E) spirals, circles, and squares Answer: C 4) Which of the following shapes is not an allowed trajectory of an object orbiting a star?

(Assume no gas or dust is affecting the object's orbit.)

A) a hyperbola B) a parabola C) a spiral D) an ellipse Answer: C

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5) Where is the center of mass of a binary system consisting of two stars with different masses? A) the center of the more massive star B) the center of the less massive star C) the point halfway in between the two stars D) a point between the two stars that is closer to the more massive star E) a point between the two stars that is closer to the less massive star Answer: D 6) What information is needed to calculate the mass of Jupiter?

A) the orbital period and distance of Jupiter's orbit around the Sun B) the orbital period and distance of one of Jupiter's moons C) the orbital speed of one of Jupiter's moons D) the Sun's mass and how Jupiter's speed changes during its elliptical orbit around the Sun E) the Sun's mass and the average distance of Jupiter from the Sun Answer: B 7) Gravity follows an inverse square law. This means that if the distance between two masses is decreased by a factor of 4, the gravitational force between those two masses A) increases by a factor of 16.

B) increases by a factor of 4.

C) increases by a factor of 2.

D) decreases by a factor of 4.

E) decreases by a factor of 16.

Answer: A 8) The gravitational force between two objects can be described using the equation Fg = G M1 M2 / d2. In this equation, what does d represent?

A) the universal gravitational constant B) the density of the smaller object C) the distance between the two objects D) the diameter of the larger object Answer: C 9) The gravitational force between two objects can be described using the equation Fg = G M1 M2 / d2. In this equation, what does G represent?

A) the universal gravitational constant B) the density of the smaller object C) the distance between the two objects D) the gravitational mass of the larger object Answer: A

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10) The gravitational force between two objects can be described using the equation Fg = G M1 M2 / d2. According to this equation, if the distance between two objects increases, what happens to the gravitational force between them?

A) The force increases.

B) The force decreases.

C) The force drops instantly to zero.

D) The gravitational force is not affected by distance.

Answer: B 11) Imagine we've discovered a planet orbiting another star at an average distance of 1 AU with an orbital period of 6 months. The planet has a moon that orbits the planet at the same distance as our Moon, but it takes 2 months to complete an orbit. What can we infer about this planet?

A) It is more massive than Earth.

B) It is less massive than Earth.

C) It has the same mass as Earth.

D) We cannot answer the question without knowing the mass of the star.

E) We cannot answer the question without knowing the mass of the moon.

Answer: B 12) A planet is orbiting a star. Which of the following statements is true for the acceleration and gravitational forces in this situation?

A) The acceleration of the planet is much more than the acceleration of the star, and the gravitational force on the planet is much more than the gravitational force on the star.

B) The acceleration of the planet is much more than the acceleration of the star, but the gravitational force on the star is the same but opposite the gravitational force on the planet.

C) The gravitational force on the star is much smaller than the gravitational force on the planet, but the accelerations are equal and opposite.

Answer: B 13) If the Sun instantaneously shrunk dramatically in size but retained the same mass, what would happen to the Earth?

A) Earth's orbit would be unchanged.

B) Earth would gradually spiral into the shrunken Sun. C) Earth would be ejected from the solar system.

D) Earth would be rapidly sucked into the shrunken Sun. Answer: A 14) If we found a solar system where the central star's mass was double that of the Sun, what would be the period a planet orbiting 1 AU from the central star?

A) more than a year B) less than a year C) about a year D) impossible to say, since we need to know the mass of the planet to predict its period Answer: B

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Section 4.5 1) What would happen if a rocket were launched into space with a speed greater than Earth's escape velocity?

A) It would travel away from Earth into the solar system.

B) It would fall back to the Earth.

C) It would enter into orbit around the Earth.

D) It would reach the orbit of the Moon, but could go no farther.

E) It is not possible to reach speeds that high.

Answer: A 2) Which of the following best describes why Earth has tides?

A) Earth gets stretched out because the gravitational force from the Moon is stronger on parts of the Earth that are nearer to the Moon.

B) Earth gets stretched out because the Moon pulls from one side, while the Sun pulls from the other.

C) Earth's sea level changes constantly because of rainfall.

D) Earth bulges near its equator because it is spinning.

E) Air pressure from the atmosphere pushes on the surface of the ocean.

Answer: A 3) At which lunar phase(s) are tides most pronounced (e.g., the highest high tides)?

A) first quarter B) new Moon C) full Moon D) both new and full Moons E) both first and third quarters Answer: B 4) At which lunar phase(s) are tides least pronounced (e.g., the lowest high tides)?

A) first quarter B) new Moon C) full Moon D) both new and full Moons E) both first and third quarters Answer: E 5) The escape velocity for a 100-kg object on Earth is about 11 km/s. What is the escape velocity of a 50-kg object on the surface of Earth?

A) 11 km/s B) 22 km/s C) 5.5 km/s D) 44 km/s E) 2.75 km/s Answer: A

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6) Which of the following caused the Moon to show (nearly) the same face to the Earth at all times?

A) tidal friction B) spring tides C) conservation of energy D) atmospheric drag E) gravitational encounters Answer: A General Chapter Questions 1) The source of energy that powers the Sun is A) chemical potential energy of hydrogen.

B) mass energy released by nuclear fusion.

C) gravitational potential energy of the contraction of the gas cloud that formed the Sun. D) kinetic energy of the orbital motion of the Sun. E) thermal energy of the hydrogen atoms in the Sun. Answer: B 2) The orbital period of a geosynchronous satellite is A) the same as Earth's precise rotation period.

B) the same as the Moon's precise orbital period around Earth.

C) the same as Earth's orbital period around the Sun. D) about 12 years.

E) about 26,000 years.

Answer: A 3) A basketball player jumps to make a basket and remains in the air for a moment. A sportscaster then remarks that she has "defied gravity." Which of the following accurately describes the situation?

A) The player did stay in the air in spite of the Law of Gravitation, but a single counterobservation is not enough to warrant revisiting a theory that usually works.

B) The player produced enough force with her legs to accelerate upward and remains above ground only until the acceleration of gravity brought her back down.

C) The player can "defy gravity" because the Universal Law of Gravitation makes an exception for basketball players.

D) The player has defied gravity, so scientists must go back into the lab to refine their theory.

Answer: B 4) Earth is farthest from the Sun in July and closest to the Sun in January. During which Northern Hemisphere season is Earth moving fastest in its orbit?

A) winter B) spring C) summer D) fall Answer: A

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5) Newton's version of Kepler's third law states: p2 =

× a3

In this equation, what does a represent?

A) the orbital period B) the average distance between the two objects C) the masses of the two objects D) the universal gravitational constant Answer: B 6) Newton's version of Kepler's third law states: p2 =

× a3

In this equation, what does G represent?

A) the orbital period B) the average distance between the two objects C) the masses of the two objects D) the universal gravitational constant Answer: D 7) Newton's version of Kepler's third law states: p2 =

× a3

According to this, what observational information does one need in order to calculate the combined mass of a planet and its moon?

A) the orbital period and the density of the two objects B) the average distance between the two objects and the orbital period C) the radius of the two planets in meters and the average distance between them D) It is impossible to determine the mass of any astronomical object.

Answer: B 8) Newton's version of Kepler's third law states: p2 =

× a3

Solve this equation to find the combined mass of a planet and its satellite, given the orbital period and average separation. × 2 A) M1+ M= 2Gπ 4 B) M1 + M2 =

×

C) M1 + M2 =

×

D) M1+ M=2

×

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9) Suppose that Earth rotated once every 48 hours (instead of 24 hours), but Earth's orbit and the Moon's distance were still the same (and their masses were still the same). Which of the following statements would be true?

A) Along coastlines, the time between one high tide and the next would be longer.

B) The length of the year would be longer.

C) Along coastlines, the time between one high tide and the next would be shorter.

D) The Moon's orbital period would be longer.

E) There would be more days in each year.

Answer: A 10) Consider the following three hypothetical planets orbiting a star with the same mass as the Sun (one solar mass): Planet X: one Earth mass and 1 AU from the star Planet Y: two Earth masses and 1 AU from the star Planet Z: two Earth masses and 2 AU from the star The shortest orbital period belongs to (Ignore very small differences in orbital period that might be attributed to the planet masses alone.)

A) Planet X alone B) Planet Y alone C) Planet Z alone D) Planets X and Y, which have about the same orbital period E) Planets Y and Z, which have about the same orbital period F) all three planets, since they all have about the same orbital period Answer: D 11) Consider a star with 2 identical planets, both with nearly circular orbits, except the orbit of Planet A is closer to the star than the orbit of Planet B. Which of the following statements is true?

A) Planet A is moving slower than Planet B. B) Planet A moves with the same speed as Planet B. C) Planet A is moving faster than Planet B. Answer: C Short Answer Questions 1) You are alone in space and your tether brakes and you are floating motionless relative to your spaceship, which is located a frustrating 10 meters away. Your spacesuit has no jet pack and you have no air to spare. All you have is your wrench. How can you return to your ship?

Answer: Throw the wrench in the opposite direction (utilizing the conservation of momentum).

With a 1-lb (2.2 kg) wrench and a 30-mph (13 m/s) throw, you'll be back in a minute.

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Reading Quiz Questions 1) Which of the following describes a velocity (as opposed to a speed)?

A) 20 kilometers per hour, headed north B) 300,000 kilometers per second C) 9.8 meters per second squared (m/s2) D) 15 newtons E) 5 light-years Answer: A 2) The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?

A) 30 m/s B) 10 m/s C) 30 m/s2 D) 10 m/s2 E) 20 m/s Answer: A 3) Momentum is defined as A) mass multiplied by velocity.

B) mass multiplied by speed.

C) force multiplied by velocity.

D) mass multiplied by acceleration.

Answer: A 4) Which of the following examples describes a situation where a car is experiencing a net force?

A) The car is holding constant speed around a curve.

B) The car is holding constant speed down a straight hill because the driver is applying the brakes.

C) The car is moving at constant speed in a straight line.

D) The car is stopped on a hill.

Answer: A 5) Suppose you lived on the Moon. Which of the following would be true?

A) weight would be less than your weight on Earth, but your mass would be the same as Your it is on Earth.

B) Both your weight and your mass would be less than they are on Earth.

C) Your mass would be less than your mass on Earth, but your weight would be the same as it is on Earth.

D) Both your weight and your mass would be the same as they are on Earth.

Answer: A 17

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6) In which of the following cases would you feel weightless?

A) while falling from a roof B) while parachuting from an airplane C) while accelerating downward in an elevator D) while walking on the Moon Answer: A 7) Which of the following statements is not one of Newton's Laws of Motion?

A) What goes up must come down.

B) The rate of change of momentum of an object is equal to the net force applied to the object.

C) In the absence of a net force acting on it, an object moves with constant velocity.

D) For any force, there always is an equal and opposite reaction force.

Answer: A 8) Newton's Second Law of Motion tells us that the net force applied to an object equals its A) mass multiplied by acceleration.

B) mass multiplied by energy.

C) momentum multiplied by velocity.

D) mass multiplied by velocity.

Answer: A 9) Suppose that two objects collide. Which of the following things is not necessarily the same both before and after the collision? (In other words, which quantity is not conserved according to the laws of physics?)

A) the total temperature of the objects B) the total momentum of the objects C) the total angular momentum of the objects D) the total energy of the objects Answer: A 10) When a spinning ice skater pulls in his arms, he spins faster because A) his angular momentum must be conserved, so reducing his radius must increase his speed of rotation.

B) there is less friction with the air.

C) there is less friction with the ice.

D) there exists an unbalanced reaction force.

Answer: A 11) The energy attributed to an object by virtue of its motion is known as A) kinetic energy.

B) potential energy.

C) radiative energy.

D) mass-energy.

Answer: A

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12) Radiative energy is A) energy carried by light.

B) heat energy.

C) energy from nuclear power plants.

D) energy of motion.

Answer: A 13) Absolute zero is A) 0 Kelvin.

B) 0º Celsius.

C) 0° Fahrenheit.

D) 100º Celsius.

Answer: A 14) What does temperature measure?

A) the average kinetic energy of particles in a substance B) the average mass of particles in a substance C) the total potential energy of particles in a substance D) the total amount of heat in a substance Answer: A 15) In the formula E = mc2, what does E represent?

A) the mass-energy, or potential energy stored in an object's mass B) the kinetic energy of a moving object C) the radiative energy carried by light D) the gravitational potential energy of an object held above the ground E) the electric field produced by a charge Answer: A 16) According to the universal law of gravitation, if you triple the distance between two objects, then the gravitational force between them A) decreases by a factor of 9.

B) increases by a factor of 9.

C) decreases by a factor of 3.

D) increases by a factor of 3.

Answer: A 17) What is the difference between a bound orbit and an unbound orbit around the Sun? A) An object on a bound orbit follows the same path around the Sun over and over, while an object on an unbound orbit approaches the Sun just once and then never returns.

B) A bound orbit is an orbit allowed by the universal law of gravitation, and an unbound orbit is not.

C) An object on a bound orbit has a gravitational attraction to the Sun, while an object on an unbound orbit does not.

D) A bound orbit is circular, while an unbound orbit is elliptical.

Answer: A

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18) The allowed shapes for the orbits of objects responding only to the force of gravity are A) ellipses, parabolas, and hyperbolas.

B) ellipses only.

C) ellipses, spirals, and parabolas.

D) circles and ellipses.

Answer: A 19) Why is Newton's version of Kepler's third law so useful to astronomers?

A) It can be used to determine the masses of many distant objects.

B) It allows us to calculate distances to distant objects.

C) It tells us that more-distant planets orbit the Sun more slowly.

D) It explains why objects spin faster when they shrink in size.

Answer: A 20) What do we mean by the orbital energy of an orbiting object (such as a planet, moon, or satellite)?

A) Orbital energy is the sum of the object's kinetic energy and its gravitational potential energy as it moves through its orbit.

B) Orbital energy is the object's kinetic energy as it moves through its orbit.

C) Orbital energy is a measure of the object's speed as it moves through its orbit.

D) Orbital energy is the amount of energy required for the object to leave orbit and escape into space.

Answer: A 21) Which statement must be true for a rocket to travel from Earth to another planet?

A) It must attain escape velocity from Earth.

B) It must carry a lot of extra fuel.

C) It must have large engines.

D) It must be launched from space, rather than from the ground.

Answer: A 22) Approximately where is it currently high tide on Earth?

A) on the portion of Earth facing directly toward the Moon and on the portion of Earth facing directly away from the Moon B) only on the portion of the Earth facing directly toward the Moon C) wherever it is currently noon D) anywhere that ocean water laps up on the shore Answer: A Concept Quiz Questions 1) Which of the following represents a case in which you are not accelerating?

A) driving in a straight line at 100 kilometers per hour B) going from 0 to 100 kilometers per hour in 10 seconds C) slamming on the brakes to come to a stop at a stop sign D) driving 100 kilometers per hour around a curve Answer: A

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2) Suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen? A) Both will hit the ground at the same time. B) The 10-pound weight will hit the ground before the 5-pound weight. C) The 5pound weight will hit the ground before the 10-pound weight. D) Both weights will float freely because everything is weightless on the Moon. Answer: A 3) Why are astronauts weightless in the Space Station? You may find it helpful to watch the video "Newton's Laws of Motion." A) because the Space Station is constantly in free-fall around the Earth B) because the Space Station is traveling so fast C) because there is no gravity in space D) because the Space Station is moving at constant velocity Answer: A 4) A net force acting on an object will always cause a change in the object's A) momentum. B) speed. C) mass.

D) direction. Answer: A 5) Suppose you are in an elevator that is traveling upward at constant speed. How does your weight compare to your normal weight on the ground? A) It is the same. B) It is greater. C) It is less. D) You are weightless. Answer: A 6) The planets never travel in a straight line as they orbit the Sun. According to Newton's second law of motion, this must mean that A) a force is acting on the planets. B) the planets are always accelerating. C) the planets have angular momentum. D) the planets will eventually fall into the Sun. Answer: A

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7) Suppose the Sun were suddenly to shrink in size but that its mass remained the same.

According to the law of conservation of angular momentum, what would happen?

A) The Sun would rotate faster than it does now.

B) The Sun's rate of rotation would slow.

C) The Sun's angular size in our sky would stay the same.

D) This could never happen because it is impossible for an object to shrink in size without an outside torque.

Answer: A 8) Suppose you kick a soccer ball straight up to a height of 10 meters. Which of the following is true about the gravitational potential energy of the ball during its flight?

A) The ball's gravitational potential energy is greatest at the instant when the ball is at its highest point.

B) The ball's gravitational potential energy is greatest at the instant it returns to hit the ground.

C) The ball's gravitational potential energy is always the same.

D) The ball's gravitational potential energy is greatest at the instant the ball leaves your foot.

Answer: A 9) Suppose you heat an oven to 400°F (about 200°C) and boil a pot of water. Which of the following explains why you would be burned by sticking your hand briefly in the pot but not by sticking your hand briefly in the oven?

A) The water can transfer heat to your arm more quickly than the air.

B) The water has a higher temperature than the oven.

C) The molecules in the water are moving faster than the molecules in the oven.

D) The oven has a higher temperature than the water.

Answer: A 10) Which of the following scenarios involves energy that we would typically calculate with Einstein's formula E = mc2?

A) A small amount of the hydrogen in of a nuclear bomb becomes energy as fusion converts the hydrogen to helium.

B) An object accelerated to a great speed has a lot of kinetic energy.

C) A mass raised to a great height has a lot of gravitational potential energy.

D) A burning piece of wood produces light and heat, therefore giving off radiative and thermal energy.

Answer: A 11) A rock held above the ground has potential energy. As the rock falls, this potential energy is converted to kinetic energy. Finally, the rock hits the ground and stays there. What has happened to the energy?

A) The energy goes to producing sound and to heating the ground, rock, and surrounding air.

B) The energy goes into the ground, and as a result, the orbit of the Earth about the Sun is slightly changed.

C) The rock keeps the energy inside it in the form of mass-energy.

D) It is transformed back into gravitational potential energy.

Answer: A

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12) Suppose that the Sun shrank in size but that its mass remained the same. What would happen to the orbit of the Earth?

A) Earth's orbit would be unaffected.

B) The size of Earth's orbit would shrink, and it would take less than one year to orbit the Sun. C) Earth's orbit would expand, and it would take more than one year to orbit the Sun. D) Earth would change from a bound orbit to an unbound orbit and fly off into interstellar space.

Answer: A 13) Imagine another solar system, with a star of the same mass as the Sun. Suppose a planet with a mass twice that of Earth (2MEarth) orbits at a distance of 1 AU from the star. What is the orbital period of this planet?

A) 1 year B) 6 months C) 2 years D) It cannot be determined from the information given.

Answer: A 14) Imagine another solar system, with a star more massive than the Sun. Suppose a planet with the same mass as Earth orbits at a distance of 1 AU from the star. How would the planet's year (orbital period) compare to Earth's year?

A) The planet's year would be shorter than Earth's.

B) The planet's year would be longer than Earth's.

C) The planet's year would be the same as Earth's.

D) An orbit at a distance of 1 AU would not be possible around a star more massive than the Sun. Answer: A 15) Newton showed that Kepler's laws are A) natural consequences of the law of universal gravitation.

B) seriously in error.

C) actually only three of seven distinct laws of planetary motion.

D) the key to proving that Earth orbits our Sun. Answer: A 16) Each of the following lists two facts. Which pair of facts can be used with Newton's version of Kepler's third law to determine the mass of the Sun? A) Earth is 150 million km from the Sun and orbits the Sun in one year.

B) Mercury is 0.387 AU from the Sun and Earth is 1 AU from the Sun. C) The mass of Earth is 6 × 1024 kg and Earth orbits the Sun in one year.

D) Earth rotates in one day and orbits the Sun in one year.

Answer: A

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17) When space probe Voyager 2 passed by Saturn, its speed increased (but not due to firing its engines). What must have happened?

A) Saturn must have lost a tiny bit of its orbital energy.

B) Voyager 2 must have dipped through Saturn's atmosphere.

C) Saturn's rotation must have sped up slightly.

D) Saturn must have captured an asteroid at precisely the moment that Voyager 2 passed by.

Answer: A 18) Suppose that a lone asteroid happens to be passing Jupiter on an unbound orbit (well above Jupiter's atmosphere and far from all of Jupiter's moons.) Which of the following statements would be true?

A) The asteroid's orbit around Jupiter would not change, and it would go out on the same unbound orbit that it came in on.

B) Jupiter's gravity would capture the asteroid, making it a new moon of Jupiter.

C) Jupiter's gravity would suck in the asteroid, causing it to crash into Jupiter.

D) There is no way to predict what would happen.

Answer: A 19) Which of the following best describes the origin of ocean tides on Earth?

A) Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth.

B) The Moon's gravity pulls harder on water than on land because water is less dense than rock.

C) Tides are caused by the 23.5-degree tilt of the Earth's rotational axis to the ecliptic plane.

D) Tides are caused on the side of the Earth nearest the Moon because the Moon's gravity attracts the water.

Answer: A 20) At which lunar phase(s) are tides most pronounced (for example, the highest high tides)?

A) both new and full moons B) both first and third quarters C) full moon only D) new moon only E) third-quarter moon only Answer: A 21) Which of the following best explains why the Moon's orbital period and rotation period are the same?

A) The Moon once rotated faster, but tidal friction slowed the rotation period until it matched the orbital period.

B) The Moon was once closer to Earth, but the force of gravity got weaker as the Moon moved farther away.

C) The law of conservation of angular momentum ensured that the Moon must have the same amount of rotational angular momentum as it has of orbital angular momentum.

D) The equality of the Moon's orbital and rotation periods is an extraordinary astronomical coincidence.

Answer: A

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22) Suppose the Moon's orbit were unchanged, but it rotated faster (meaning it did not have synchronous rotation). Which of the following would be true?

A) The Moon would go through its cycle of phases (from one new moon to the next) in less time than it does now.

B) We would no longer always see nearly the same face of the Moon.

C) Tides would be stronger; that is, higher high tides and lower low tides.

D) High tides would occur more frequently than they do now.

E) All of the listed choices are true.

Answer: B Visual Quiz Questions 1) Which person is weightless during the activity shown?

A)

B)

C)

D)

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2) Which of the following statements about the force attracting these two galaxies true? is

A) It is the same force that causes an apple to fall to the ground.

B) It is a force unlike any force that we ever experience on Earth.

C) It is a mysterious force, whose nature remains completely unknown to scientists.

D) The force will get weaker as time passes.

Answer: A

3) The diagram shows a planet at four positions in its orbit. At which position does it have the greatest angular momentum?

A) 1 B) 2 C) 3 D) 4 E) The angular momentum is the same at all four points.

Answer: E 4) The diagram shows a planet at four positions in its orbit. At which position does it have the greatest gravitational potential energy?

A) 1 B) 2 C) 3 D) 4 E) The gravitational potential energy is the same at all four positions.

Answer: C

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5) The diagram shows a planet at four positions in its orbit. At which position does it have the greatest total orbital energy? (Orbital energy is the sum of the planet's kinetic and gravitational potential energy.) A) 1 B) 2 C) 3 D) 4 E) The total orbital energy is the same at all four positions. Answer: E 6) Which of the paths shown represent unbound orbits?

A) 1 only B) 2 only C) 3 only D) both 2 and 3 E) There is no such thing as an unbound orbit.

Answer: D

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7) Suppose you are aboard a rocket that is orbiting Earth in the low, circular orbit shown. If you want to escape from Earth and head to the Moon or Mars along the "escape" path shown, what do you need to do?

A) Fire the rocket engine in your direction of travel, so that you gain speed.

B) The only way to end up on the "escape" path is to first return to Earth, then launch your rocket with escape velocity.

C) Turn the rocket around, and fire the engine so that you lose speed.

D) Throw some excess supplies overboard, so that your rocket becomes less massive.

Answer: A

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8) Which of the following correctly shows tidal bulges on Earth when the Moon is in the position shown?

A)

B)

C)

D)

Answer: A

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9) In which position(s) of the Moon do we experience the highest high tides?

A) 1 B) 2 C) 3 D) 4 E) 1 and 3 F) 2 and 4 Answer: E 10) In which position(s) of the Moon do we experience the lowest low tides?

A) 1 B) 2 C) 3 D) 4 E) 1 and 3 F) 2 and 4 Answer: E

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

The figure above, based on Figure 4.24, shows how the Moon causes tides on Earth. Note that the North Pole is in the center of the diagram, so the numbers 1 through 4 label points along Earth's equator.

1) What do the three black arrows represent? A) the tidal force Earth exerts on the Moon B) the Moon's gravitational force at different points on Earth C) the direction in which Earth's water is flowing D) Earth's orbital motion Answer: B 2) Where is it high tide? A) point 1 only B) point 2 only C) points 1 and 3 D) points 2 and 4 Answer: C 3) Where is it low tide? A) point 1 only B) point 2 only C) points 1 and 3 D) points 2 and 4 Answer: D

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4) What time is it at point 1?

A) noon B) midnight C) 6 a.m.

D) cannot be determined from the information in the figure Answer: D 5) The light blue ellipse represents tidal bulges. In what way are these bulges drawn inaccurately?

A) There should be only one bulge rather than two.

B) They should be aligned with the Sun rather than the Moon.

C) They should be much smaller compared to Earth.

D) They should be more pointy in shape.

Answer: C Chapter Review Questions 1) Define speed, velocity, and acceleration. What are the units of acceleration? What is the acceleration of gravity?

2) Define momentum and force. What do we mean when we say that momentum can be changed only by a net force?

3) What is free-fall, and why does it make you weightless? Briefly describe why astronauts are weightless in the Space Station.

4) State Newton's three laws of motion. For each law, give an example of its application.

5) Describe the laws of conservation of momentum, of angular momentum, and of energy. Give an example of how each is important in astronomy.

6) Define kinetic energy, radiative energy, and potential energy, with at least two examples of each.

7) Define and distinguish temperature and thermal energy.

8) What is mass-energy? Explain the formula E = mc2.

9) Summarize the universal law of gravitation both in words and with an equation.

10) What is the difference between a bound and an unbound orbit? What orbital shapes are possible?

11) What do we need to know if we want to measure an object's mass with Newton's version of Kepler's third law? Explain.

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12) Explain why orbits cannot change spontaneously, and how a gravitational encounter can cause a change. How can an object achieve escape velocity? 13) Explain how the Moon creates tides on Earth. Why do we have two high and low tides each day? How do the tides vary with the phase of the Moon? 14) What is tidal friction? What effects does it have on Earth? How does it explain the Moon's synchronous rotation?

Does It Make Sense?

Decide whether or not each of the following statements makes sense (or is clearly true or false). Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.

Example: I walked east from our base camp at the North Pole.

Solution: The statement does not make sense because east has no meaning at the North Pole–all directions are south from the North Pole.

15) I've never been to space, so I've never experienced weightlessness.

16) Suppose you could enter a vacuum chamber (a chamber with no air in it) on Earth. Inside this chamber, a feather would fall at the same rate as a rock.

17) If an astronaut goes on a space walk outside the Space Station, she will quickly float away from the station unless she has a tether holding her to the station.

18) I used Newton's version of Kepler's third law to calculate Saturn's mass from orbital characteristics of its moon Titan.

19) If the Sun were magically replaced with a giant rock that had precisely the same mass, Earth's orbit would not change.

20) The fact that the Moon rotates once in precisely the time it takes to orbit Earth once is such an astonishing coincidence that scientists probably never will be able to explain it.

21) Venus has no oceans, so it could not have tides even if it had a moon (which it doesn't).

22) If an asteroid passed by Earth at just the right distance, Earth's gravity would capture it and make it our second moon.

23) When I drive my car at 30 miles per hour, it has more kinetic energy than it does at 10 miles per hour.

24) Someday soon, scientists are likely to build an engine that produces more energy than it consumes.

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Quick Quiz 25) A car is accelerating when it is A) traveling on a straight, flat road at 50 miles per hour. B) traveling on a straight uphill road at 30 miles per hour. C) going around a circular track at a steady 100 miles per hour. Answer: No Correct Answer Was Provided. 26) Compared to their values on Earth, on another planet your A) mass and weight would both be the same. B) mass would be the same but your weight would be different. C) weight would be the same but your mass would be different.

Answer: No Correct Answer Was Provided. 27) Which person is weightless? A) a child in the air as she plays on a trampoline B) a scuba diver exploring a deep-sea wreck C) an astronaut on the Moon Answer: No Correct Answer Was Provided. 28) Consider the statement "There's no gravity in space." This statement is A) completely false. B) false if you are close to a planet or moon, but true in between the planets. C) completely true. Answer: No Correct Answer Was Provided. 29) To make a rocket turn left, you need to A) fire an engine that shoots out gas to the left. B) fire an engine that shoots out gas to the right. C) spin the rocket clockwise.

Answer: No Correct Answer Was Provided. 30) Compared to its angular momentum when it is farthest from the Sun, Earth's angular momentum when it is nearest to the Sun is A) greater. B) less. C) the same. Answer: No Correct Answer Was Provided. 31) The gravitational potential energy of a contracting interstellar cloud A) stays the same at all times. B) gradually transforms into other forms of energy. C) gradually grows larger. Answer: No Correct Answer Was Provided.

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32) If Earth were twice as far from the Sun, the force of gravity attracting Earth to the Sun would be A) twice as strong.

B) half as strong.

C) one quarter as strong.

Answer: No Correct Answer Was Provided.

33) According to the universal law of gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?

A) Earth would be quickly sucked into the black hole.

B) Earth would slowly spiral into the black hole.

C) Earth's orbit would not change.

Answer: No Correct Answer Was Provided.

34) If the Moon were closer to Earth, high tides would A) be higher than they are now.

B) be lower than they are now.

C) occur three or more times a day rather than twice a day.

Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

35) The Dual Power of Knowledge.Einstein's discovery that energy and mass are equivalent has led to technological developments that are both beneficial and dangerous. List as many of these developments as you can, categorizing them as positive, negative, or neutral. Overall, do you think the human race would be better or worse off if we had never discovered that mass is a form of energy? Defend your opinion.

36) Group Discussion: Hidden Figures. The 2017 movie Hidden Figures (inspired by the 2016 book by Margot Lee Shetterly) popularized the contributions of Katherine Johnson, Dorothy Vaughan, and Mary Jackson to America's space program. a) Form groups of three students. Within your group, decide who will research each of the three "hidden figures" listed above, learning about her scientific specialty, how this specialty relates to human understanding of the laws of motion and gravity, and how her work contributed to putting astronauts in space. b) After completing your individual research, report to the other members of your group on what you have learned. c) Discuss: In what sense were these individuals pioneers? Is there more than one way in which they can be considered pioneers?

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The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

37) Testing Gravity.Scientists are continually trying to learn whether our current understanding of gravity is complete or must be modified. Describe how the observed motion of spacecraft headed out of our solar system (such asVoyager the spacecraft) can be used to test the accuracy of our current theory of gravity.

38) How Does the Table Know? Thinking deeply about seemingly simple observations sometimes reveals underlying truths that we might otherwise miss. For example, think about holding a golf ball in one hand and a bowling ball in the other. To keep them motionless you must actively adjust the tension in your arm muscles so that each arm exerts a different upward force that exactly balances the weight of each ball. Now, think about what happens when you set the balls on a table. Somehow, the table also exerts exactly the right amount of upward force to keep the balls motionless, even though their weights are very different. How does a table "know" to make the same type of adjustment that you make when you hold the balls motionless in your hands? (Hint: Think about the origin of the force pushing upward on the objects.)

39) Perpetual Motion Machines. Every so often, someone claims to have built a machine that can generate energy perpetually from nothing. Why isn't this possible according to the known laws of nature? Why do you think claims of perpetual motion machines sometimes receive substantial media attention?

40) Group Activity: Your Ultimate Energy Source. Work as a group to answer each part.Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39. a) According to the law of conservation of energy, the energy your body is using right now had to come from somewhere else. Work in groups to make a list going backwards in time describing how the energy you are using right now has proceeded through time. b) For each item on the group's list, identify the energy as kinetic energy, gravitational potential energy, chemical potential energy, electrical potential energy, mass-energy, or radiative energy.

Investigate Further 41) Weightlessness. Astronauts are weightless when in orbit in the Space Station. Are they also weightless during launch to the station? How about during their return to Earth? Explain.

42) Units of Acceleration. a) If you drop a rock from a very tall building, how fast will it be going after 4 seconds? b) As you sled down a steep, slick street, you accelerate at a rate of 4 meters per second squared.

How fast will you be going after 5 seconds? c) You are driving along the highway at a speed of 60 miles per hour when you slam on the brakes. If your acceleration is at an average rate of −20 miles per hour per second, how long will it take to come to a stop?

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43) Gravitational Potential Energy. For each of the following, which object has more gravitational potential energy, and how do you know? a) A bowling ball perched on a cliff ledge or a baseball perched on the same ledge b) A diver on a 10-meter platform or a diver on a 3-meter diving board c) A 100-kilogram satellite orbiting Jupiter or a 100-kilogram satellite orbiting Earth (Assume both satellites orbit at the same distance from their planet's center.)

44) Einstein's Famous Formula. a) What is the meaning of the formula E = mc2? Be sure to define each variable. b) How does this formula explain the generation of energy by the Sun? c) How does this formula explain the destructive power of nuclear bombs?

45) The Gravitational Law. a) How does quadrupling the distance between two objects affect the gravitational force between them? b) Suppose the Sun were somehow replaced by a star with twice as much mass. What would happen to the gravitational force between Earth and the Sun? c) Suppose Earth were moved to one-third of its current distance from the Sun. What would happen to the gravitational force between Earth and the Sun? 46) Allowable Orbits? a) Suppose the Sun were replaced by a star with twice as much mass. Could Earth's orbit stay the same? Why or why not? b) Suppose Earth doubled in mass (but the Sun stayed the same as it is now). Could Earth's orbit stay the same? Why or why not?

47) Head-to-Foot Tides. You and Earth attract each other gravitationally, so you should also be subject to a tidal force resulting from the difference between the gravitational attraction felt by your feet and that felt by your head (at least when you are standing). Explain why you can't feel this tidal force.

48) Synchronous Rotation. Suppose the Moon had rotated more slowly when it formed than it does now. Would it still have ended up in synchronous rotation? Why or why not?

49) Geostationary Orbit. A satellite in geostationary orbit appears to remain stationary in the sky as seen from any particular location on Earth. a) Briefly explain why a geostationary satellite must orbit Earth in 1 sidereal day, rather than 1 solar day. b) Explain why a geostationary satellite must be in orbit around Earth's equator, rather than in some other orbit (such as around the poles). c) Home satellite dishes (such as those used for television) receive signals from communication satellites. Explain why these satellites must be in geostationary orbit.

50) Space Station Laws. Visit NASA's website for the International Space Station. Choose two photos that illustrate some facet of Newton's laws of motion or gravity, then briefly explain how these laws can help you understand what each photo shows.

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51) Elevator to Orbit. Some people have proposed building a giant elevator from Earth's surface to the altitude of geosynchronous orbit. The top of the elevator would then have the same orbital distance and period as any satellite in geosynchronous orbit. a) Suppose you were to let go of an object at the top of the elevator. Would the object fall? Would it orbit Earth? Explain. b) Briefly explain why (not counting the huge costs for construction) the elevator would make it much cheaper and easier to put satellites in orbit or to launch spacecraft into deep space. c) Research ideas for actually building a space elevator. Do you think it is feasible? Do you think it would be a good idea? Explain.

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

52) Energy Comparisons.Use the data in Table 4.1. a) Compare the energy of a 1-megaton H-bomb to the energy released by a major earthquake. b) If the United States obtained all its energy from oil, how much oil would be needed each year? c) Compare the Sun's annual energy output to the energy released by a supernova.

53) Moving Candy Bar. Table 4.1 shows that metabolizing a candy bar releases about 106 joules.

How fast must the candy bar travel to have the same 106 joules in the form of kinetic energy? mv2, Assume the candy bar's mass is 0.2 kg and use the formula kinetic energy = where m is the object's mass and v is its velocity. Is your answer a faster or slower speed than you expected?

54) Spontaneous Human Combustion. Suppose that all the mass in your body were suddenly converted into energy according to the formula E = mc2. How much energy would be released?

Compare this to the energy released by a 1-megaton H-bomb (see Table 4.1). What effect would your disappearance have on your surroundings?

55) Fusion Power. No one has yet succeeded in creating a commercially viable way to produce energy through nuclear fusion. However, suppose we could build fusion power plants using the hydrogen in water as a fuel. Based on the data in Table 4.1, how much water would we need each minute to meet U.S. energy needs? Could such a reactor power the entire United States with the water flowing from your kitchen faucet? Explain. (Hint: Use the annual U.S. energy consumption to find the energy consumption per minute, and then divide by the energy yield from fusing 1 liter of water to figure out how many liters would be needed each minute.)

56) Understanding Newton's Version of Kepler's Third Law. Find the orbital period for the planet in each case. (Hint: The calculations for this problem are so simple that you will not need a calculator.) a) A planet with twice Earth's mass orbiting at a distance of 1 AU from a star with the same mass as the Sun b) A planet with Earth's mass orbiting at a distance of 1 AU from a star with four times the Sun's mass

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57) Using Newton's Version of Kepler's Third Law. a) Calculate Earth's approximate mass from the fact that the Moon orbits Earth every 27.3 days at an average distance of 384,000 kilometers. b) Calculate Jupiter's approximate mass from the fact that its moon Io orbits every 42.5 hours at an average distance of 422,000 kilometers. c) Calculate the orbital distance for a planet that has an orbital period of 63 days around a star with the mass of the Sun. d) Calculate the combined mass of Pluto and its moon Charon from the fact that Charon orbits Pluto every 6.4 days with a semimajor axis of 19,700 kilometers. e) Calculate the orbital period of a spacecraft in an orbit 300 kilometers above Earth's surface. f) Calculate the approximate mass of the Milky Way Galaxy from the fact that the Sun orbits the galactic center every 230 million years at a distance of 27,000 light-years. (As discussed in Chapter 19, this calculation tells us only the mass of the galaxy within the Sun's orbit.)

58) Escape Velocity. Calculate the escape velocity from each of the following, using data as needed from Appendix E. a) The surface of Mars b) The surface of Mars's moon Phobos c) The surface (cloud tops) of Jupiter d) Our solar system, starting from Earth's orbit (Hint: The mass of our solar system is approximately the same as the mass of the Sun.) e) Our solar system, starting from Saturn's orbit 59) Weights on Other Worlds. Calculate the acceleration of gravity on the surface of each of the following worlds, using data as needed from Appendix E. How much would you weigh, in pounds, on each of these worlds? a) Mars b) Venus c) Jupiter's moon Europa d) Mars's moon Phobos 60) Gees. Acceleration is sometimes measured in gees, or multiples of the acceleration of gravity: 1 gee (1g) means 1 × g, or 9.8 m/s2; 2 gees (2g) means 2 × g, or 2 × 9.8 m/s2 = 19.6 m/s2; and so on. Suppose you experience 6 gees of acceleration in a rocket. a) What is your acceleration in meters per second squared? b) You will feel a compression force from the acceleration. How does this force compare to your normal weight? c) Do you think you could survive this acceleration for long? Explain.

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61) Extra Moon. Suppose Earth had a second moon, called Swisscheese, with an average orbital distance double the Moon's and a mass about the same as the Moon's. a) Would Swisscheese's orbital period be longer or shorter than the Moon's? Explain. b) Use Kepler's third law to find the approximate orbital period of Swisscheese. (Hint: You can solve this problem with Kepler's original version of his third law by using the ratios of the orbital periods and distances of the two moons.) c) Describe how you would expect tides on Earth to differ because of the presence of this second moon. Consider cases in which the two moons are (i) on the same side of Earth, (ii) on opposite sides of Earth, and (iii) 90° apart in their orbits.

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The Cosmic Perspective, 9e (Bennett et al.) Chapter 5 Light and Matter Section 5.1 1) If a material is transparent, then it A) reflects light well. B) absorbs light well. C) transmits light well. D) scatters light well. E) emits light well. Answer: C 2) Grass appears green because A) it emits green light and absorbs other colors. B) it absorbs green light and emits other colors. C) it transmits green light and emits other colors. D) it reflects green light and absorbs other colors. Answer: D 3) Everything looks red through a red filter because A) the filter emits red light and absorbs other colors. B) the filter absorbs red light and emits other colors. C) the filter transmits red light and absorbs other colors. D) the filter reflects red light and transmits other colors. Answer: C 4) Which of the following is an example of reflection or scattering? A) Red light hits a red sweatshirt. B) Visible light does not pass through a black wall. C) Blue light hits a red sweatshirt. D) Light comes from your computer screen. Answer: A 5) Which statement correctly describes units that can be used to measure energy and power?

A) Energy is measured in joules and power is measured in joules per second. B) Energy and power are both measured in units of joules. C) Energy and power are both measured in units of watts. D) Energy is measured in watts and power is measured in watts per second. E) Energy is measured in watts and power is measured in newtons.

Answer: A

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6) How much energy is needed to power a 100-watt light bulb for 1 second? A) 6000 joules B) 100 joules C) 1 joule D) 100 watts E) 6000 watts Answer: B 7) We can see each other in the classroom right now because we A) emit visible light. B) emit thermal radiation. C) emit infrared light. D) reflect visible light. E) reflect infrared light. Answer: D Section 5.2 1) A wave has peaks and troughs that can move matter up and down when the wave interacts with matter. The frequency of a wave is A) the number of peaks passing by any point each second. B) the speed at which a wave moves through space. C) the distance between two adjacent peaks of a wave. Answer: A 2) The wavelength of a wave is A) how strong the wave is. B) the distance between a peak of the wave and the next trough. C) the distance between two adjacent peaks of the wave. D) the distance between where the wave is emitted and where it is absorbed. E) equal to the speed of the wave times the wave's frequency. Answer: C 3) How are wavelength, frequency, and energy related for photons of light? A) Longer wavelength means lower frequency and lower energy. B) Longer wavelength means higher frequency and lower energy. C) Longer wavelength means higher frequency and higher energy. D) Longer wavelength means lower frequency and higher energy. E) There is no simple relationship because different photons travel at different speeds. Answer: A

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4) From lowest energy to highest energy, which of the following correctly orders the different regions of electromagnetic radiation? A) infrared, visible light, ultraviolet, x-rays, gamma rays, radio B) radio, infrared, visible light, ultraviolet, x-rays, gamma rays C) visible light, infrared, x-rays, ultraviolet, gamma rays, radio D) gamma rays, x-rays, visible light, ultraviolet, infrared, radio E) radio, x-rays, visible light, ultraviolet, infrared, gamma rays Answer: B 5) From lowest frequency to highest frequency, which of the following correctly orders the different regions of electromagnetic radiation? A) infrared, visible light, ultraviolet, x-rays, gamma rays, radio B) radio, infrared, visible light, ultraviolet, xrays, gamma rays C) visible light, infrared, x-rays, ultraviolet, gamma rays, radio D) gamma rays, x-rays, visible light, ultraviolet, infrared, radio E) Radio, x-rays, visible light, ultraviolet, infrared, gamma rays Answer: B 6) From shortest wavelength to longest wavelength, which of the following correctly orders the different regions of electromagnetic radiation? A) infrared, visible light, ultraviolet, x-rays, gamma rays, radio B) radio, infrared, visible light, ultraviolet, x-rays, gamma rays C) visible light, infrared, xrays, ultraviolet, gamma rays, radio D) gamma rays, x-rays, visible light, ultraviolet, infrared, radio E) radio, x-rays, visible light, ultraviolet, infrared, gamma rays Answer: D 7) Which of the following statements about x-rays and radio waves is not true? A) X-rays have shorter wavelengths than radio waves. B) X-rays and radio waves are both forms of light, or electromagnetic radiation. C) X-rays have higher frequency than radio waves. D) X-rays have higher energy than radio waves. E) X-rays travel through space faster than radio waves. Answer: E 8) Which of the following statements about x-rays and radio waves is true? A) X-rays have the same wavelengths as radio waves. B) X-rays have the same frequency as radio waves. C) X-rays have the same energy as radio waves. D) Xrays travel through space at the same speed as radio waves. Answer: D

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9) Red light has a lower energy per photon than blue light. Therefore, red light has A) higher frequency, shorter wavelength than blue light.

B) lower frequency, longer wavelength than blue light.

C) lower frequency, shorter wavelength than blue light.

D) higher frequency, longer wavelength than blue light.

Answer: B 10) Which statement about photons is true?

A) An infrared photon has less energy than an x-ray photon, but travels at the same speed.

B) An infrared photon has less energy than an x-ray photon, and travels more slowly.

C) An infrared photon has more energy than an x-ray photon, and travels more quickly.

D) An infrared photon has more energy than an x-ray photon, but travels at the same speed.

Answer: A 11) Photons behave like A) waves.

B) particles.

C) both waves and particles.

D) neither waves nor particles.

Answer: C 12) Why can't we see radio waves?

A) Radio waves have wavelengths too long for the eye to detect.

B) Radio waves are sound waves, so we hear them.

C) Radio waves fade away before they can reach our eyes.

D) We do see radio waves, but we interpret them as the color red.

E) Radio waves have too low energy to be detected by any means.

Answer: A 13) The visible light portion of the electromagnetic spectrum has wavelengths ranging from about 400 to 700 nanometers (nm). Which of the following statements is true?

A) Blue light has wavelength of about 400 nm, red light has wavelength of about 700 nm.

B) Blue light has wavelength of about 700 nm, red light has wavelength of about 400 nm.

C) Blue light and red light can both have wavelengths that may be anywhere between 400 and 700 nm.

D) Blue light and red light both have wavelengths of about 550 nm.

Answer: A Section 5.3 1) Which of the following best describes the sizes of atoms?

A) Atoms are so small that millions of them could fit across the period at the end of this sentence.

B) Atoms are too small to see by eye, but can be seen with a handheld magnifying glass.

C) Most atoms are about a millionth of a meter (1 micrometer) in diameter.

D) Atoms are roughly the same size as typical bacteria.

Answer: A

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2) What is a molecule? A) a group of two or more atoms bound together B) a particle that is part of an atomic nucleus C) the smallest known particle in nature D) an atom that has lost or gained an electron so that it is electrically charged E) a form of an atom that has more or less neutrons than normal Answer: A 3) The diameter of a typical atom is about ________ the diameter of its nucleus. A) the same as B) 10 times C) 100 times D) 1/10 of E) 100,000 times Answer: E 4) What is the overall electrical charge of an atom with 6 protons, 6 neutrons, and 5 electrons? A) +17 B) −5 C) +7 D) +1 E) +6 Answer: D 5) Which of the following statements about electrical charge is true? A) Two negative charges will attract each other. B) Two positive charges will attract each other. C) A positive charge and a negative charge will repel each other. D) A positive charge and a negative charge will attract each other. Answer: D 6) An iron atom has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have? A) 26 protons, 30 neutrons, 26 electrons B) 26 protons, 30 neutrons, 30 electrons C) 26 protons, 56 neutrons, 26 electrons D) 13 protons, 43 neutrons, 13 electrons E) 13 protons, 56 neutrons, 13 electrons Answer: A

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7) A gold atom has an atomic number of 79 and an atomic mass number of 197. If it is neutral, how many protons, neutrons, and electrons does it have?

A) 79 protons, 118 neutrons, 79 electrons B) 79 protons, 118 neutrons, 118 electrons C) 79 protons, 118 neutrons, 39 electrons D) 118 protons, 79 neutrons, 118 electrons E) 118 protons, 39 neutrons, 118 electrons Answer: A 8) Oxygen has atomic number 8. How many times must an oxygen atom be ionized to create an O+5 ion, and how many electrons will the ion have?

A) It must be ionized three times; it will have five electrons.

B) It must be ionized five times; it will have five electrons.

C) It must be ionized five times; it will have three electrons.

D) It doesn't have to be ionized; it just needs to gain five protons.

E) It doesn't have to be ionized; it already has only three electrons.

Answer: C 9) If a proton inside the nucleus of an atom suddenly turned into a neutron, while the atom retained its original number of electrons, what properties of the atom would change?

A) only its atomic number B) only its atomic mass number C) only its electrical charge D) both its atomic number and atomic mass number, but not its electrical charge E) both its atomic number and electrical charge, but not its atomic mass number Answer: E 10) At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter?

A) a gas of rapidly moving molecules B) a plasma consisting of positively charged ions and free electrons C) a gas consisting of individual, neutral atoms, but no molecules D) a plasma consisting of rapidly moving, neutral atoms E) matter cannot exist at extremely high temperatures.

Answer: B 11) Molecular dissociation is the process in which A) the bonds between atoms in a molecule are broken.

B) a molecule goes from the solid phase to the gas phase.

C) the bonds between electrons around an atomic nucleus are broken.

D) an element changes into another form.

E) an electron is shared between atomic nuclei.

Answer: A

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12) When a neutral atom loses an electron, we say that it becomes A) vaporized. B) dissociate. C) ionized. D) an isotope. E) a plasma. Answer: C 13) An electron-volt is A) the charge of one electron. B) the energy of one electron. C) the energy jump between the first and second energy levels of hydrogen. D) an amount of energy much smaller than a joule. E) an amount of energy much larger than a joule. Answer: D 14) The idea that energy in atoms has distinct energy levels is part of the branch of physics that is called A) special relativity. B) general relativity. C) quantum physics. D) classical physics. E) particle physics. Answer: C Section 5.4 1) What do we see when white light passes through a cool cloud of gas? A) visible light B) infrared light C) thermal radiation D) an absorption line spectrum E) an emission line spectrum Answer: D 2) When an electron in an atom goes from a higher energy level to a lower energy level, the atom may A) emit a photon of a specific wavelength. B) absorb a photon of a specific wavelength. C) absorb several photons of a specific wavelength. D) emit a photon of any wavelength. E) absorb a photon of any wavelength. Answer: A

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3) An electron in an atom can go from a lower energy level to a higher energy level if the atom A) emits a photon of a specific wavelength.

B) absorbs a photon of a specific wavelength.

C) emits several photons of a specific wavelength.

D) emits a photon of any wavelength.

E) absorbs a photon of any wavelength.

Answer: B 4) When an electron drops to a lower energy level in an atom, but no other interactions take place A) the atom may emit a photon of light of a specific wavelength.

B) the total energy of the atom remains unchanged.

C) the atom must slow its speed moving through space.

D) the atom must increase its speed moving through space.

E) the electron must become slightly more massive.

Answer: A 5) What must be true in order for an atom to absorb a photon?

A) The photon must have energy matching the difference in energy between two energy levels in the atom.

B) The atom must have lost all of its electrons.

C) The photon must have enough energy to remove an electron from the atom.

D) A or C E) B or C Answer: D 6) Spectra from neutral atoms compared with spectra from ionized atoms of the same element A) are the same.

B) are slightly redshifted.

C) are slightly blueshifted.

D) have different sets of spectral lines.

E) have the same sets of spectral lines but different widths for those lines.

Answer: D 7) How does the spectrum of a molecule differ from the spectrum of an atom?

A) A molecule does not have spectral lines due to electrons changing energy levels.

B) A molecule has additional spectral lines due to changes in its rotational and vibrational energies.

C) Molecules only have spectral lines at ultraviolet wavelengths.

D) Most atoms only have spectral lines at infrared wavelengths.

E) An atom has a wider range of spectral lines than molecules.

Answer: B

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8) Which of the following objects does not produce a spectrum that is a close approximation to a thermal radiation spectrum?

A) a hot, transparent gas B) a star C) a filament in an ordinary (incandescent) light bulb D) you E) a planet Answer: A

9) The diagram above represents energy levels in a hydrogen atom. Each level is labeled with its energy (above the ground state of Level 1) in units of electron/volts (eV). The labeled transitions represent an electron moving between energy levels. Which transition represents an electron that absorbs a photon with 10.2 eV of energy?

A) A B) B C) C D) D E) E Answer: B

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10) The diagram above represents energy levels in a hydrogen atom. Each level is labeled with its energy (above the ground state of Level 1) in units of electron/volts (eV). The labeled transitions represent an electron moving between energy levels. Which transition represents the electron that emits a photon with the highest energy?

A) A B) B C) C D) D E) E Answer: A 11) The diagram above represents energy levels in a hydrogen atom. Each level is labeled with its energy (above the ground state of Level 1) in units of electron/volts (eV). The labeled transitions represent an electron moving between energy levels. Which transition represents an electron that is breaking free of the atom?

A) A B) B C) C D) D E) E Answer: E 12) The diagram below represents energy levels in a hydrogen atom. Each level is labeled with its energy (above the ground state of Level 1) in units of electron/volts (eV). The labeled transitions represent an electron moving between energy levels. Which transition, as shown, is not possible?

A) A B) B C) C D) D E) E Answer: D 13) Thermal radiation is defined as A) radiation produced by a hot object.

B) radiation in the infrared part of the spectrum.

C) radiation that depends only on the emitting object's temperature.

D) radiation in the form of emission lines from an object.

E) radiation that is felt as heat.

Answer: C

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14) Which of the following statements about thermal radiation is always true?

A) A hot object emits more x-rays than a cool object.

B) A hot object emits more radio waves than a cool object.

C) A hot object emits more total radiation than a cool object.

D) A hot object emits more total radiation per unit surface area than a cool object.

E) A hot object emits less total radiation than a cool object.

Answer: D 15) A gas heated to millions of degrees would emit A) mostly radio waves.

B) mostly x-rays.

C) mostly ultraviolet light.

D) an equal amount of all wavelengths of light.

E) no light because it is too hot.

Answer: B 16) You are heating two chunks of metal of the same size and shape. One is made of lead and is heated to 400 K. The other is made of iron and is heated to 350 K. Which of the following statements apply to the thermal radiation the two chunks emit?

A) The two spectra peak at the same wavelength.

B) The spectra cannot be compared because they come from different materials.

C) The lead spectrum peak is at a shorter wavelength than the iron spectrum peak.

D) The lead spectrum peak is at a longer wavelength than the iron spectrum peak.

Answer: C 17) You are heating two chunks of metal of the same size and shape. One is made of lead and is heated to 400 K. The other is made of iron and is also heated to 400 K. Which of the following statements apply to the thermal radiation the two chunks emit?

A) The two spectra peak at the same wavelength.

B) The spectra cannot be compared because they come from different materials.

C) The lead spectrum peak is at a shorter wavelength than the iron spectrum peak.

D) The lead spectrum peak is at a longer wavelength than the iron spectrum peak.

Answer: A 18) Which of the following stars has the hottest surface temperature?

A) the blue star B) the orange star C) the yellow star D) the red star Answer: A

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19) Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)

A) The red star is more massive than the blue star.

B) The blue star is more massive than the red star.

C) The red star is farther away than the blue star.

D) The blue star has a hotter surface temperature than the red star.

E) The red star has a hotter surface temperature than the blue star.

Answer: D 20) From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?

A) The star is moving toward us.

B) The star is moving away from us.

C) The star is getting hotter.

D) The star is getting colder.

E) The "star" actually is a planet.

Answer: B 21) We have obtained spectra of two hydrogen gas clouds and are studying an emission line that has a laboratory wavelength of 656.3 nm. This emission line appears in Cloud A's spectrum with a wavelength of 660.1 nm and in Cloud B's spectrum at 670.2 nm. What can we conclude about these clouds?

A) They are both moving toward us, and Cloud A is moving faster than Cloud B. B) They are both moving away from us, and Cloud A is moving faster than Cloud B. C) They are both moving away from us, and Cloud B is moving faster than Cloud A. D) They are both moving toward us, and Cloud B is moving faster than Cloud A. Answer: C 22) One of the absorption lines of hydrogen has a rest wavelength of 656 nm. Suppose you observe this line in four different stars, and find this line at the wavelengths show below. Which wavelength represents the star that is moving toward Earth the fastest?

A) 630 nm B) 656 nm C) 670 nm D) 640 nm Answer: A 23) If a hydrogen emission line appears at 656 nm in the laboratory, what can we say about a cloud of hydrogen gas, with an emission line at 680 nm?

A) It is receding away from us.

B) It is moving toward us.

C) It is neither receding nor approaching us.

D) There is not enough information to say anything about the cloud's motion.

Answer: A

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24) The spectrum of Star A has an absorption line of hydrogen at 660.0 nm. The spectrum of Star B has an absorption line at 666 nm. The wavelength of this transition in the laboratory is 656 nm. What can I say about Star A and Star B? A) Both stars are moving away from me, Star A is faster than Star B. B) Both stars are moving toward me, Star A is faster than Star B. C) Both stars are moving toward me, Star B is faster than Star A D) Both stars are moving away from me, Star B is faster than Star A. Answer: D 25) If one object has a large redshift and another object has a small redshift, what can we conclude about these two objects? A) The one with the large redshift is moving toward us faster than the one with the small redshift. B) The one with the large redshift is moving away from us, and the one with the small redshift is moving toward us. C) The one with the large redshift is moving away from us faster than the one with the small redshift. D) The one with the large redshift is hotter and therefore is putting out more radiation. E) The one with the large redshift is redder in color than the other one. Answer: C 26) You observe the same spectral line in two stars that are identical in every way except that one rotates faster than the other. How does the spectral line differ between the two? A) There is no difference. B) The line in the faster rotating star is blueshifted. C) The line in the faster rotating star is redshifted. D) The line in the faster rotating star is broader. E) The line in the faster rotating star is narrower. Answer: D General Chapter Questions 1) One star is emitting mostly visible light, and another star is emitting mostly infrared light. Which star is hotter? A) The temperature also depends on the radius of the star, so one can't decide based on the information provided. B) Both stars are the same temperature. C) The star emitting visible light. D) The star emitting infrared light. Answer: C

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2) Which of the following stars is the hottest?

A) a blue star B) an orange star C) a yellow star D) a green star E) a red star Answer: A 3) When an atom's electrons fall down to lower energy levels in a thin cloud of hot gas, what is produced?

A) thermal radiation B) an absorption line spectrum C) an emission line spectrum D) an infrared spectrum E) new interstellar compounds Answer: C 4) We know the Sun is primarily made from hydrogen and helium on the basis of its A) luminosity.

B) spectrum.

C) age.

D) color.

E) mass.

Answer: B 5) One star is emitting primarily visible light, and another star is emitting primarily infrared light. Which star is hotter?

A) There is not enough information to answer the question.

B) Both stars are the same temperature.

C) The star emitting visible light is hotter.

D) The star emitting infrared light is hotter.

Answer: C 6) Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

A) It is moving away from us.

B) Its surface is cooler than the surface of the Sun. C) It is much more massive than the Sun. D) It is much brighter than the Sun. Answer: B

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7) Which of the following describes the light that can be detected from a person? A) The person reflects many wavelengths of visible light and emits infrared light. B) The person emits many wavelengths of visible light and reflects infrared light. C) The person emits a few narrow wavelengths of visible light based on the elements that make up the human body. D) The person reflects a few narrow wavelengths of visible light based on the elements that make up the human body. Answer: A 8) Four different objects have spectra that peak in the wavelength regions listed below. Which peak wavelength region is associated with the coldest of the four objects? A) x-rays B) visible light C) infrared D) ultraviolet Answer: A 9) We know how fast a distant galaxy is moving away from us on the basis of its A) mass. B) color. C) spectrum. D) age. E) luminosity. Answer: C 10) Which of the following objects would produce an emission line spectrum? A) a hot, low-density neon gas B) a star like our Sun C) a light bulb D) the Earth Answer: A 11) We can see other people because people A) emit thermal radiation. B) emit visible light. C) emit infrared light. D) reflect visible light. E) reflect infrared light. Answer: D 12) We can see the Moon because it A) emits visible light. B) emits thermal radiation. C) reflects infrared light. D) reflects visible light. E) glows through radioactive decay. Answer: D

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13) Which of the following observational techniques is most appropriate for measuring Doppler shifts? A) spectroscopy (taking a spectrum) B) imaging (taking a picture) C) timing (measuring how the amount of light changes with time) Answer: A 14) If two objects are the same size, but one object has a temperature 3 times as hot (in Kelvin) as the other object, the hotter object emits A) 3 times as much energy.

B) 9 times as much energy.

C) 12 times as much energy.

D) 81 times as much energy.

E) 27 times as much energy.

Answer: D 15) Hydrogen has an absorption line at a rest wavelength of 656.28 nm. This line is shifted to 656.50 nm in the spectrum of a star. How fast is the star moving? Hint: The Doppler shift formula is = where the speed of light is c ≈ 300,000 km/ A) about 100 km/s away from us.

B) about 100 km/s toward us.

C) about 1000 km/s away from us.

D) about 1000 km/s toward us.

Answer: A 16) Suppose that an ion has an absorption line at a rest wavelength of 1000.0 nm. This line is shifted to 1000.1 nm in the spectrum of a star. How fast is the star moving? Hint: The Doppler shift formula is = where the speed of light is c ≈ 300,000 km/ A) about 300 km/s away from us.

B) about 300 km/s toward us.

C) about 3000 km/s away from us.

D) about 3000 km/s toward us.

Answer: A

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Reading Quiz Questions 1) What is the difference between energy and power? A) Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time. B) Power is measured in joules and energy is measured in watts. C) Power is used to describe energy of light, whereas the term energy has a broader meaning. D) There's no difference; energy and power are different names for the same thing. Answer: A 2) A red shirt is red because it A) reflects red light but absorbs other colors. B) transmits red light. C) emits red light only. D) absorbs red light but reflects other colors. Answer: A 3) Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond? A) They have a frequency of 2 hertz. B) They have a frequency of 4 hertz. C) We can calculate the wavelength of the ripples from their frequency. D) They have a wavelength of two cycles per second. Answer: A 4) Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon? A) its wavelength and energy B) its temperature C) its acceleration D) the chemical composition of the object that emitted it Answer: A 5) When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called A) photons. B) wavicles. C) gamma rays. D) frequencies. Answer: A

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6) From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation? A) gamma rays, x-rays, ultraviolet, visible light, infrared, radio B) infrared, visible light, ultraviolet, x-rays, gamma rays, radio C) radio, infrared, visible light, ultraviolet, x-rays, gamma rays D) gamma rays, x-rays, visible light, ultraviolet, infrared, radio Answer: A 7) Which forms of light are lower in energy and frequency than the light that our eyes can see? A) infrared and radio B) ultraviolet and x-rays C) visible light D) infrared and ultraviolet Answer: A 8) Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend? A) several kilometers B) a few meters C) several centimeters D) to the Sun Answer: A 9) Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)? A) They have different numbers of protons in their nucleus. B) They have different atomic mass numbers. C) They have different numbers of electrons. D) They have different names. Answer: A 10) Consider an atom of carbon in which the nucleus contains six protons and seven neutrons. What is its atomic number and atomic mass number? A) atomic number = 6; atomic mass number = 13 B) atomic number = 6; atomic mass number = 7 C) atomic number = 13; atomic mass number = 6 D) atomic number = 7; atomic mass number = 13 Answer: A 11) An atom which has 4 protons and 6 neutrons will be electrically neutral if it contains A) 4 electrons. B) 6 electrons. C) 10 electrons. D) at least 1 electron. Answer: A

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12) Vaporization is the process in which A) molecules go from the liquid or solid phase to the gas phase. B) molecules go from the solid phase to the liquid phase. C) molecules go from the liquid phase to the solid phase. D) electrons are stripped from atoms. Answer: A 13) Which of the following transitions within an atom is not possible? A) An electron begins in an excited state and then gains enough energy to jump to the ground state. B) An electron begins in the ground state and then gains enough energy to jump to an excited state. C) An electron begins in the ground state and then gains enough energy to become ionized. D) An electron begins in an excited state and then gains enough energy to become ionized. Answer: A 14) An atom that has fewer electrons than protons is called a(n) A) ion.

B) molecule. C) solid. D) plasma. Answer: A 15) Suppose you look at a detailed spectrum of visible light from some object. How can you decide whether it is an emission line spectrum or an absorption line spectrum? A) An emission line spectrum consists of bright lines on a dark background, whereas an absorption line spectrum consists of dark lines on a rainbow background. B) An emission line spectrum consists of a long bright line, whereas an absorption line spectrum consists of a long dark line. C) The only way to decide is to make a graph of the intensity of the light at every wavelength, and then analyze the graph carefully. D) The emission line spectrum is produced by electrons jumping up in energy level, whereas the absorption line spectrum is produced by electrons jumping down in energy level. Answer: A 16) Thermal radiation is defined as A) radiation with a spectrum whose shape depends only on the temperature of the emitting object. B) radiation produced by an extremely hot object. C) radiation that is felt as heat.

D) radiation in the form of emission lines from an object. Answer: A

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17) According to the laws of thermal radiation, hotter objects emit photons with A) a shorter average wavelength.

B) a lower average frequency.

C) a lower average energy.

D) a higher average speed.

Answer: A 18) Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?

A) the wavelengths of spectral lines in the star's spectrum B) the peak energy of the star's thermal radiation C) the Doppler shift of the star's spectrum D) whether the star's spectrum has more emission lines or more absorption lines Answer: A 19) The spectra of most galaxies show redshifts. This means that their spectral lines A) have wavelengths that are longer than normal.

B) always are in the red part of the visible spectrum.

C) have wavelengths that are shorter than normal.

D) have a higher intensity in the red part of the spectrum.

Answer: A 20) You observe a distant galaxy. You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum. What can you conclude?

A) The galaxy is moving away from you.

B) The galaxy is moving toward you.

C) The galaxy has weak gravity.

D) The galaxy is made purely of hydrogen.

Answer: A Concept Quiz Questions 1) Suppose you have a 100-watt light bulb that you leave turned on for one minute. How much energy does it use?

A) 6,000 joules B) 6,000 watts C) 100 watts D) 100 joules Answer: A 2) Which of the following statements is true of green grass?

A) It absorbs red light and reflects green light.

B) It absorbs red light and emits green light.

C) It transmits all colors of light except green.

D) It means the lawn is healthy.

Answer: A

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3) Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz (megahertz). Which of the following statements is true?

A) The radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second.

B) The radio waves from the radio station have a wavelength of 97 million meters.

C) The "radio waves" received by your radio are not light waves like those we talk about in astronomy, but rather are a special type of sound wave.

D) The radio station broadcasts its signal with a power of 97 million watts.

Answer: A 4) Gamma rays have a small A) wavelength.

B) energy.

C) frequency.

D) mass.

Answer: A 5) Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength?

A) 1 meter B) 1/300,000 meter C) 300 million meters D) A photon's wavelength cannot be determined from its frequency.

Answer: A 6) Which of the following best describes why we say that light is an electromagnetic wave?

A) The passage of a light wave can cause electrically charged particles to move up and down.

B) Light can be produced only by electric or magnetic appliances.

C) Light is produced only when massive fields of electric and magnetic energy collide with one another.

D) The term electromagnetic wave arose for historical reasons, but we now know that light has nothing to do with either electricity or magnetism.

Answer: A 7) Which of the following statements about x-rays and radio waves is not true?

A) X-rays travel through space faster than radio waves.

B) X-rays have shorter wavelengths than radio waves.

C) X-rays and radio waves are both forms of light, or electromagnetic radiation.

D) X-rays have higher frequency than radio waves.

Answer: A

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8) Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?

A) Atom 1: nucleus with seven protons and eight neutrons, surrounded by seven electrons Atom 2: nucleus with seven protons and seven neutrons, surrounded by seven electrons B) Atom 1: nucleus with six protons and eight neutrons, surrounded by six electrons Atom 2: nucleus with seven protons and eight neutrons, surrounded by seven electrons C) Atom 1: nucleus with eight protons and eight neutrons, surrounded by eight electrons Atom 2: nucleus with eight protons and eight neutrons, surrounded by seven electrons D) Atom 1: nucleus with four protons and five neutrons, surrounded by four electrons Atom 2: nucleus with five protons and five neutrons, surrounded by four electrons Answer: A 9) Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature?

A) It would vaporize (evaporate) into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.

B) The liquid molecules would quickly dissociate into a liquid of individual oxygen atoms.

These atoms would then vaporize (evaporate) into a gas, and then become ionized to make a plasma.

C) It would vaporize (evaporate) into a gas, then the molecules would lose electrons until no electrons were left, then the molecules would dissociate into individual oxygen nuclei.

D) The liquid oxygen first would solidify. The solid would then vaporize (sublimate) into a gas, which would then become a plasma as the molecules lost their electrons, until finally it consisted of bonded pairs of oxygen nuclei stripped bare of any electrons.

Answer: A 10) Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion?

A) charge = +2; number of remaining electrons = 6 B) charge = +2; number of remaining electrons = 8 C) charge = −2; number of remaining electrons = 10 D) charge = +2; number of remaining electrons = 2 Answer: A 11) Which of the following statements about electrons is not true?

A) Electrons orbit the nucleus rather like planets orbiting the Sun. B) Within an atom, an electron can have only particular energies.

C) An electron has a negative electrical charge.

D) Electrons have little mass compared to protons or neutrons.

E) Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels.

Answer: A

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12) Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space? A) The cloud is cool and lies between you and a hot star.

B) The cloud is extremely hot. C) The cloud is visible primarily because it reflects light from nearby stars. D) The cloud is cool and dense, so that you cannot see any objects that lie behind it. Answer: A 13) No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum? A) a hot, thin (low-density, nearly transparent) gas B) a filament in a standard (incandescent) light bulb C) a star D) you Answer: A 14) Which of the following statements about thermal radiation is always true?

A) A hot object emits more radiation per unit surface area than a cool object. B) A cold object produces more total infrared and radio emission per unit surface area than a hot object. C) A hot object produces more total infrared emission than a cooler object. D) All the light emitted by hot object has higher energy than the light emitted by a cooler object.

Answer: A 15) Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color? A) Its surface is cooler than the surface of the Sun. B) It is much brighter than the Sun. C) It is much more massive than the Sun. D) It is moving away from us. Answer: A 16) The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun? A) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum. B) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the blue light that is present in the Sun's spectrum. C) Neptune's spectrum would peak at a much longer wavelength than the Sun's spectrum. D) There is no way to predict the answer to this question because planets and stars are made of such different things. Answer: A

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17) All of the following statements about the Sun's corona are true. Which one explains why it is a source of X-rays? A) The temperature of the corona's gas is some 1 to 2 million Kelvin. B) The corona lies above the visible surface of the Sun. C) The corona's gas consists mostly of hydrogen and helium. D) The corona's structure is largely shaped by magnetic fields. Answer: A 18) Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude? A) The star is moving toward us. B) The star is moving away from us. C) The star is getting hotter. D) The star is getting colder. Answer: A 19) Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude? A) Star X is moving away from us faster than Star Y. B) Star Y is moving away from us faster than Star X. C) Star X is hotter than Star Y. D) Star X is moving away from us and Star Y is moving toward us. E) Star X is coming toward us faster than Star Y. Answer: A 20) If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet? A) The planet is rotating. B) We must actually be observing moons orbiting the planet in opposite directions, not the planet itself. C) The planet is in the process of falling apart. D) The planet is in the process of formation. Answer: A 21) Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true? A) The total amount of light in the spectrum tells us the star's radius. B) The peak of the star's thermal emission tells us its temperature; hotter stars peak at shorter (bluer) wavelengths. C) We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals. D) Shifts in the wavelengths of spectral lines compared to the wavelengths of those same lines measured in a laboratory on Earth can tell us the star's speed toward or away from us.

Answer: A

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22) Suppose that two stars are identical in every way; for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth, except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?

A) The faster rotating star has wider spectral lines than the slower rotating star.

B) The faster rotating star will have an emission line spectrum whereas the slower rotating star will have an absorption line spectrum.

C) The peak of thermal emission will be at a shorter wavelength for the faster rotating star than for the slower rotating star.

D) There is no way to tell the stars apart spectroscopically because their spectra will be identical.

Answer: A Visual Quiz Questions

1) The diagram represents energy levels in a hydrogen atom. The labeled transitions (A through E) represent an electron moving between energy levels. Which labeled transition represents an electron that absorbs a photon with 10.2 eV of energy?

A) A B) B C) C D) D E) E Answer: B

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2) The diagram represents energy levels in a hydrogen atom. The labeled transitions (A through E) represent an electron moving between energy levels. If an electron at level 1 in a hydrogen atom absorbs 10.2 eV of energy, it moves to level 2. What typically happens next?

A) The electron returns to level 1 by emitting an ultraviolet photon with 10.2 eV of energy.

B) The electron jumps to level 3 as soon as it absorbs any additional energy.

C) The electron remains in level 2 until it absorbs an additional 10.2 eV of energy.

D) A different electron drops into level 1 because it is now unoccupied.

Answer: A

3) Assume the woman in the figure uses her prism to look at a spectrum of light coming from the object(s) shown. In which case will she see a continuous rainbow of thermal radiation?

A) Case 1 B) Case 2 C) Case 3 D) Case 4 Answer: A 4) In which case will the woman see a rainbow of color interrupted by a few dark absorption lines?

A) Case 1 B) Case 2 C) Case 3 D) Case 4 Answer: B

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5) In which case will the woman see a just a spectrum that is almost entirely black except for few bright emission lines? A) 1 B) 2 C) 3 D) 4 Answer: C 6) Suppose you decide to make a graph of intensity against wavelength for the spectrum shown here. Which of the following shows what the graph will look like?

A)

B)

C)

D)

Answer: B

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7) This photo shows the visible light spectrum of the Sun. Why does it have all those dark lines on it?

A) The dark lines represent wavelengths of light at which atoms near the Sun's surface absorb radiation from the hotter solar interior.

B) The dark lines come from sunspots on the Sun, which are dark in color.

C) The dark lines are caused by Doppler shifts.

D) The dark lines are not real, but rather are artifacts of the photographic process used to record the spectrum.

Answer: A 8) This figure shows idealized thermal radiation spectra from several stars and a human. Based on this graph, at about what wavelength does a 15,000 K star emit its most intense light?

A) about 100 nanometers B) about 1,000 nanometers C) about 20 nanometers D) about 100,000 nanometers Answer: A

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9) Consider the spectra of the four objects shown beneath the laboratory spectrum. Based on these spectra, what can you conclude about Object 1?

A) It is moving away from us.

B) It is composed mostly of hydrogen, helium, and iron.

C) It is a star with a thin upper atmosphere.

D) It is a hot object, with a temperature above 1 million K. E) It is moving toward us.

Answer: A 10) Now consider Object 2. What can you say about Object 2 in comparison to Object 1?

A) Object 2 is moving away from us faster than Object 1.

B) Object 2 contains more hydrogen than Object 1.

C) Object 1 had a higher temperature than Object 2.

D) Object 2 is moving toward us while Object 1 is moving away from us.

Answer: A

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

The graph above is a schematic spectrum of the planet Mars; it is the same spectrum shown in Figure 5.13. Keeping in mind that Mars reflects visible sunlight and emits infrared light, refer to the numbered features of the graph and answer the following questions.

1) Which of the six numbered features represents emission lines?

Answer: 1 2) Which of the six numbered features represents absorption lines? Answer: 5 3) Which portion(s) of the spectrum represent(s) reflected sunlight? A) 1 only B) 2, 3, and 4 C) 3 and 6 D) the entire spectrum Answer: B 4) What does the wavelength of the peak labeled 6 tell us about Mars? A) its color B) its surface temperature C) its chemical composition D) its orbital speed Answer: B 5) What feature(s) of this spectrum indicate(s) that Mars appears red in color? A) the wavelength of the peak labeled 3 B) the wavelength of the peak labeled 6 C) the fact that the intensity of region 4 is higher than that of region 2 D) the fact that the peak labeled 3 is higher than the peak labeled 6 Answer: C

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Chapter Review Questions 1) What is the difference between energy and power? What units do we use to measure power?

2) What are the four major ways light and matter can interact? Give an example of each from everyday life.

3) Why do we say that light is an electromagnetic wave? Describe the relationship among wavelength, frequency, and speed for light.

4) What is a photon? In what way is a photon like a particle? In what way is it like a wave?

5) List the different forms of light in order from lowest to highest energy. Is the order the same from lowest to highest frequency? From shortest to longest wavelength? Explain.

6) Briefly describe the structure and size of an atom. How big is the nucleus in comparison to the entire atom?

7) Define atomic number and atomic mass number. Under what conditions are two atoms different isotopes of the same element? What is a molecule?

8) What is electrical charge? Will an electron and a proton attract or repel each other? How about two electrons? Explain.

9) Describe the phase changes of water as you heat it, starting from its solid phase, ice. What happens at very high temperatures? What is a plasma?

10) Describe the energy levels that we find for electrons in atoms. Under what circumstances can energy level transitions occur?

11) How do we convert a spectrum shown as a band of light (like a rainbow) into a graph of the spectrum?

12) Describe the conditions that lead to each of the three basic types of spectra. Which type is the Sun's visible-light spectrum, and why?

13) How can we use emission or absorption lines to determine the chemical composition of a distant object?

14) Describe two ways in which the thermal radiation spectrum of an 8000 K star would differ from that of a 4000 K star.

15) Describe the Doppler effect for light and what we can learn from it. What does it mean to say that radio waves are blueshifted? Why does the Doppler effect widen the spectral lines of rotating objects?

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16) Describe each of the key features of the spectrum in Figure 5.25 and explain what it tells us about the object.

Does It Make Sense?

Decide whether or not each of the following statements makes sense (or is clearly true or false).

Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.

Example: I walked east from our base camp at the North Pole.

Solution: The statement does not make sense because east has no meaning at the North Pole–all directions are south from the North Pole.

17) The walls of my room are transparent to radio waves.

18) Because of their higher frequencies, x-rays must travel through space faster than radio waves.

19) If you could see infrared light, you would see a glow from the backs of your eyelids when you closed your eyes.

20) If you had x-ray vision, you could read this entire book without turning any pages.

21) Two isotopes of the element rubidium differ in their number of protons.

22) A "white hot" object is hotter than a "red hot" object.

23) If the Sun's surface became much hotter (while the Sun's size remained the same), the Sun would emit more ultraviolet light but less visible light than it currently emits.

24) If you could view a spectrum of light reflecting off a blue sweatshirt, you'd find the entire rainbow of color (looking the same as a spectrum of white light).

25) Galaxies that show redshifts must be red in color.

26) If a distant galaxy has a substantial redshift (as viewed from Earth), then anyone living in that galaxy would see a substantial redshift in a spectrum of the Milky Way Galaxy.

Quick Quiz

27) Why is a sunflower yellow?

A) It emits yellow light.

B) It absorbs yellow light.

C) It reflects yellow light.

Answer: No Correct Answer Was Provided.

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28) Compared to red light, blue light has higher frequency and A) higher energy and shorter wavelength. B) higher energy and longer wavelength. C) lower energy and shorter wavelength. Answer: No Correct Answer Was Provided.

29) Radio waves are A) a form of sound.

B) a form of light.

C) a type of spectrum.

Answer: No Correct Answer Was Provided.

30) Compared to an atom as a whole, an atomic nucleus is A) very tiny but has most of the mass.

B) quite large and has most of the mass.

C) very tiny and has very little mass.

Answer: No Correct Answer Was Provided.

31) Some nitrogen atoms have seven neutrons and some have eight neutrons; these two forms of nitrogen are A) ions of each other.

B) phases of each other.

C) isotopes of each other.

Answer: No Correct Answer Was Provided.

32) Ionization is the process by which A) electrons escape from atoms.

B) liquid material enters the gas phase.

C) molecules break apart into individual atoms.

Answer: No Correct Answer Was Provided.

33) If you heat a rock until it glows, its spectrum will be A) a thermal radiation spectrum.

B) an absorption line spectrum.

C) an emission line spectrum.

Answer: No Correct Answer Was Provided.

34) The set of spectral lines that we see in a star's spectrum depends on the star's A) interior temperature.

B) chemical composition.

C) rotation rate.

Answer: No Correct Answer Was Provided.

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35) Compared to the Sun, a star whose spectrum peaks in the infrared is A) cooler. B) hotter. C) larger. Answer: No Correct Answer Was Provided. 36) A spectral line that appears at a wavelength of 321 nm in the laboratory appears at a wavelength of 328 nm in the spectrum of a distant object. We say that the object's spectrum is A) redshifted. B) blueshifted. C) whiteshifted. Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

37) Pair Discussion: The Curies.The married couple Marie and Pierre Curie were pioneers in the study of matter. a) Working independently, learn about the Nobel prizes the Curies won, the reasons for those prizes, and the differing roles Marie and Pierre assumed in carrying out their research. Also, find the overall fraction of Nobel prizes in science that have gone to women. b) Pair up with another student, one of you talking about Marie Curie and the other about Pierre Curie. Take turns describing what each scientist did to help earn their Nobel prizes. Then discuss whether you think they both deserved the Nobel prizes they received, and how well you think they worked together and supported each other. c) Discuss the fraction of Nobel prizes that have gone to women. Does it seem surprising to you?

Why or why not?

The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

38) Newton's Prisms.Review the brief discussion in this chapter of how Newton proved that the colors seen when light passes through a prism come from the light itself rather than from the prism. Suppose you wanted to test Newton's findings. Assuming you had two prisms and a white screen, describe how you would arrange the prisms to duplicate Newton's discovery.

39) Elements in Space. Astronomers claim that objects throughout the universe are made of the same chemical elements that exist here on Earth. Given that most of these objects are so far away that we can never hope to visit them, why are astronomers so confident that these objects are made from the same set of chemical elements, rather than some completely different types of materials?

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40) The Changing Limitations of Science. Review the box "Extraordinary Claims: We Can Never Learn the Composition of Stars," which gives an example of how new discoveries can change the apparent limitations of science. Today, other questions seem beyond the reach of science, such as the question of how life began on Earth. Do you think such questions will ever be answerable through science? Defend your opinion. 41) Democritus and the Path of History. Besides his belief in atoms, Democritus held several other strikingly modern notions. For example, he maintained that the Moon was a world with mountains and valleys and that the Milky Way was composed of countless individual stars– ideas that weren't generally accepted until the time of Galileo, more than 2000 years later.

Unfortunately, we know of Democritus's work only secondhand, because none of the 72 books he is said to have written survived the destruction of the Library of Alexandria. Do you think history might have been different if the work of Democritus had not been lost?

Defend your opinion. 42) Group Activity: Light Around You. Working in groups, look carefully at all the ways in which light and matter are interacting in the room around you to answer the following questions; explain all your answers clearly. Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39. a) What is emitting light? b) What is absorbing light? c) What is responsible for the colors you see? d) What would the room look like if you observed it with an infrared camera? With an ultraviolet camera? With an x-ray camera? e) Are there any radio waves in the room? How do you know?

Investigate Further

43) Atomic Terminology Practice I. a) The most common form of iron has 26 protons and 30 neutrons. State its atomic number, atomic mass number, and number of electrons (if it is neutral). b) Consider the following three atoms: Atom 1 has 7 protons and 8 neutrons; atom 2 has 8 protons and 7 neutrons; atom 3 has 8 protons and 8 neutrons. Which two are isotopes of the same element? c) Oxygen has atomic number 8. How many times must an oxygen atom be ionized to create an O+5 ion? How many electrons are in an O+5 ion?

44) Atomic Terminology Practice II. a) What are the atomic number and atomic mass number of a fluorine atom with 9 protons and 10 neutrons? If we could add a proton to this fluorine nucleus, would the result still be fluorine?

What if we added a neutron to the fluorine nucleus? Explain. b) The most common isotope of gold has atomic number 79 and atomic mass number 197. How many protons and neutrons does the gold nucleus contain? If the isotope is electrically neutral, how many electrons does it have? If it is triply ionized, how many electrons does it have? c) Uranium has atomic number 92. Its most common isotope is 238U, but the form used in nuclear bombs and nuclear power plants is 235U. How many neutrons are in each of these two isotopes of uranium?

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45) The Fourth Phase of Matter. a) Explain why nearly all the matter in the Sun is in the plasma phase. b) Based on your answer to part a, explain why plasma is the most common phase of matter in the universe. c) If plasma is the most common phase of matter in the universe, why is it so rare on Earth?

46) Energy Level Transitions. The diagram below shows five transitions (labeled with capital letters A through E) representing an electron moving between energy levels in a hydrogen atom.

Explain your answers clearly.

a) Which transition could represent an atom that absorbs a photon with 10.2 eV of energy? b) Which transition could represent an atom that emits a photon with 10.2 eV of energy? c) Which transition represents an electron that is breaking free of the atom? d) Which transition, as shown, is not possible? e) Does transition A represent emission or absorption of light, and how would the wavelength of the emitted or absorbed photon compare to that of the photon involved in transition C? 47) Spectral Summary. Clearly explain how studying an object's spectrum can allow us to determine each of the following properties of the object. a) The object's surface chemical composition b) The object's surface temperature c) Whether the object is a low-density cloud of gas or something more substantial d) Whether the object has a hot upper atmosphere e) Whether the object is reflecting blue light from a star f) The speed at which the object is moving toward or away from us g) The object's rotation rate

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48) Orion Nebula. Much of the Orion Nebula looks like a glowing cloud of gas. What type of spectrum would you expect to see from the glowing parts of the nebula? Why? 49) The Doppler Effect. In hydrogen, the transition from level 2 to level 1 has a rest wavelength of 121.6 nm. Suppose you see this line at a wavelength of 120.5 nm in Star A, 121.2 nm in Star B, 121.9 nm in Star C, and 122.9 nm in Star D. Which stars are coming toward us? Which are moving away? Which star is moving fastest relative to us? Explain your answers without doing any calculations.

50) Your Microwave Oven. A microwave oven emits microwaves that have just the right wavelength to cause energy level changes in water molecules. Use this fact to explain how a microwave oven cooks your food. Why doesn't a microwave oven make a plastic dish get hot?

Why do some clay dishes get hot in the microwave? Why do dishes that aren't themselves heated by the microwave oven sometimes still get hot when you heat food on them? (Note: It's not a good idea to put empty dishes in a microwave.)

51) Light Bulbs. Look up typical spectra of traditional incandescent light bulbs, compact fluorescent light (CFL) bulbs, and LED bulbs. (Or, if you have a diffraction grating [which you can buy for about $1], observe the spectra for yourself.) How do the spectra of the different types of light bulbs compare? Use what you find to explain why CFLs and LEDs can be much more energy efficient than incandescent bulbs.

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

52) Human Wattage.A typical adult uses about 2500 Calories of energy each day. Use this fact to calculate the typical adult's average ( 1 Calorie = 4184 powerrequirement, in watts.Hint: joules.)

53) Electric Bill. Your electric utility bill probably shows your energy use for the month in units of kilowatt-hours. A kilowatt-hour is defined as the energy used in 1 hour at a rate of 1 kilowatt (1000 watts); that is, 1 kilowatt-hour = 1 kilowatt × 1 hour. Use this fact to convert 1 kilowatthour into joules. If your bill says you used 900 kilowatt-hours, how much energy did you use in joules?

54) Radio Station. What is the wavelength of a radio photon from an AM radio station that broadcasts at 1120 kilohertz? What is its energy?

55) UV Photon. What is the energy (in joules) of an ultraviolet photon with wavelength 120 nm?

What is its frequency?

56) X-Ray Photon. What is the wavelength of an x-ray photon with energy 10 keV (10,000 eV)?

What is its frequency? (1 eV = 1.60 × 10−19 joule.)

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57) How Many Photons? Suppose that all the energy from a 100-watt light bulb came in the form of photons with wavelength 600 nm. (Note: In reality, light bulbs distribute energy over many wavelengths; see Exercise 51.) a) Calculate the energy of a single photon with wavelength 600 nm. b) How many 600-nm photons would have to be emitted each second to account for all the light from this 100-watt light bulb? c) Based on your answer to part b, explain why we don't notice the particle nature of light in our everyday lives.

58) Thermal Radiation Laws. a) Find the emitted power per square meter and wavelength of peak intensity for a 3000 K object that emits thermal radiation. b) Find the emitted power per square meter and wavelength of peak intensity for a 50,000 K object that emits thermal radiation.

59) Hotter Sun. Suppose the surface temperature of the Sun were about 12,000 K, rather than 6000 K. a) How much more thermal radiation would the Sun emit? b) What would happen to the Sun's wavelength of peak emission? c) Do you think it would still be possible for life to exist on Earth? Explain.

60) Taking the Sun's Temperature. The Sun radiates a total power of about 4 × 1026 watts into space. The Sun's radius is about 7 × 108 meters. a) Calculate the average power radiated by each square meter of the Sun's surface. (Hint: The formula for the surface area of a sphere is A = 4ℼr2.) b) Using your answer from part a and the Stefan-Boltzmann law, calculate the average surface temperature of the Sun. (Note: The temperature calculated this way is called the Sun's effective temperature.)

61) Doppler Calculations. In hydrogen, the transition from level 2 to level 1 has a rest wavelength of 121.6 nm. Find the speed and direction (toward or away from us) of a star in which this line appears at wavelength a) 120.5 nm. b) 121.2 nm. c) 121.9 nm. d) 122.9 nm.

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The Cosmic Perspective, 9e (Bennett et al.)

Chapter 6 Telescopes Section 6.1 1) What is the purpose of the lens in an eye?

A) to bend light entering the eye so that it is focused onto the retina B) to collect light to send to the brain to be interpreted C) to interpret the light collected by the eye as colors D) to adjust the amount of light entering the eye so it is not too much or too little E) to determine what color the eye will be Answer: A 2) The place where light is brought into focus (to form an image) in the human eye is called the A) retina.

B) optic nerve.

C) lens.

D) pupil.

E) cornea.

Answer: A 3) A camera is designed to bring light into focus (to form an image) on its A) detector.

B) shutter.

C) lens.

Answer: A 4) What is the benefit of a longer exposure time when making an image?

A) It allows the detector to collect more total light.

B) It allows the detector to measure rapid variations in light intensity.

C) It allows the detector to record light at very short wavelengths.

D) It allows the detector to achieve higher angular resolution.

Answer: A Section 6.2 1) How do the light-collecting area and best possible angular resolution of telescope with a 10meter diameter mirror compare to that of a telescope with a 5-meter diameter mirror?

A) The 10-meter telescope has double the light collecting area, and its angular resolution is better by a factor of 2.

B) The 10-meter telescope has 4 times the light collecting area, and its angular resolution is better by a factor of 2.

C) The 10-meter telescope has 4 times the light collecting area, and its angular resolution is better by a factor of 4.

D) The 10-meter telescope has 10 times the light collecting area, and its angular resolution is better by a factor of 5.

Answer: B

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2) How does the light-collecting area of a telescope with a 10-meter diameter mirror compare to that of a telescope with a 5-meter diameter mirror? A) The 10-meter telescope has 2 times the light collecting area. B) The 10-meter telescope has 4 times the light collecting area. C) The 10-meter telescope has 10 times the light collecting area. Answer: B 3) How does the best possible angular resolution of a telescope with a 10-meter diameter mirror compare to that of a telescope with a 5-meter diameter mirror? A) The 10meter telescope's angular resolution is better by a factor of 2. B) The 10-meter telescope's angular resolution is better by a factor of 4. C) The 10-meter telescope's angular resolution is better by a factor of 10. Answer: A 4) Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes? A) You will not be able to see these two stars at all. B) The two stars will look like a single point of light. C) The two stars will appear to be touching, looking rather like a small dumbbell. D) You will see two distinct stars. E) You will see only the larger of the two stars, not the smaller one. Answer: B 5) Suppose two stars are separated in the sky by 0.1 arcseconds. If you take a picture of them with the SOAR telescope, which has an angular resolution of 0.6 arcsecond, what will you see? A) one point of light that is the blurred image of both stars B) two separate points of light C) nothing at all Answer: A 6) If you want to see the image formed by a telescope, you should place your eye at the location of the telescope's A) focus. B) primary mirror. C) secondary mirror. D) central hole in the primary mirror. E) Cassegrain. Answer: A

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7) Which of the following is one important reason why most large astronomical telescopes are reflecting telescopes rather than refracting telescopes?

A) Reflecting telescopes have their heaviest component (the mirror) at the bottom rather than the top of the telescope's tube.

B) Reflecting telescopes take up less space than refracting telescopes.

C) Reflecting telescopes are taller than refracting telescopes.

D) For a mirror and lens of the same diameter, a mirror will collect more light.

Answer: A 8) Which of the following measurements can be made only by recording and comparing the amount of light received from an astronomical source at many different times?

A) the rate at which a variable star brightens and dims B) the general shape of an interstellar cloud of gas C) the color of a planet D) the number of bright stars in a nearby star cluster Answer: A 9) Which of the following could not be determined by an observation that only uses spectroscopy?

A) the chemical composition of a distant star B) the speed at which a distant galaxy is moving away from us C) the surface temperature of a distant star D) the rotation rate of a distant star E) the angular size of a distant galaxy Answer: E 10) What is meant by spectral resolution?

A) It is a measure of how much energy an object emits in different parts of the electromagnetic spectrum.

B) It is a measure of how close two spectral lines can be and still be distinguishable.

C) It is a measure of how close two stars can be in the sky and still be distinguishable.

D) It is the same as angular resolution but applied to telescopes operating at different wavelengths.

Answer: B 11) Some stars vary in brightness. What observing technique is best for observing the details of the changes in brightness?

A) Time-monitoring because we want to track how the brightness changes with time.

B) Imaging because an image will show the star getting brighter and dimmer.

C) Spectroscopy because changing brightness means changing temperature.

D) All of the above are equally useful in detecting variation in brightness.

Answer: A

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Section 6.3 1) What do astronomers mean by light pollution? A) Light pollution refers to pollution caused by light industry as opposed to heavy industry. B) Light pollution refers to harmful gases emitted by common street lights. C) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations. D) Light pollution refers to the lights that must be used inside major observatories and that make it difficult for astronomers' eyes to adapt to darkness. E) Light pollution is another name for sunlight, which makes it impossible to see stars in the daytime. Answer: C 2) What causes stars to twinkle? A) It is intrinsic to the stars—their brightness varies as they expand and contract. B) variations in the absorption of light at different depths in Earth's atmosphere C) variable absorption by interstellar gas along the line of sight to the star D) bending of light rays by turbulent motions of air in Earth's atmosphere E) the inability of the human eye to focus on small points of light Answer: D 3) What causes stars to twinkle? A) Stars constantly vary in brightness as they expand and contract. B) Interstellar gas along the line of sight to the star absorbs different amounts of radiation. C) The human eye has difficulty seeing faint objects. D) Moving gases in Earth's atmosphere randomly bend light rays from stars. Answer: D 4) What is the purpose of adaptive optics? A) to improve the angular resolution of telescopes in space B) to reduce the distorting effects of atmospheric turbulence for telescopes on the ground C) to increase the collecting area of telescopes on the ground D) to increase the magnification of telescopes on the ground E) to allow several small telescopes to work together like a single larger telescope Answer: B 5) Which of the following is not a good reason to place an observatory on a remote mountain to? A) reduce the impact of light pollution B) reduce the twinkling caused by Earth's atmosphere C) allow study of infrared light D) allow observations at ultraviolet and x-ray wavelengths Answer: D

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6) Which of the following wavelength regions cannot be studied at all with telescopes on the ground? A) radio B) infrared C) x-rays D) both radio and x-rays E) both infrared and xrays Answer: C 7) Earth's atmosphere is most transparent to all wavelengths of ________ light. A) infrared B) visible C) ultraviolet D) x-ray E) both visible and ultraviolet Answer: B 8) What is the best reason to put a visible-light telescope in space instead of on the ground?

A) The telescope is above the atmosphere so the light does not get distorted by turbulent air. B) A space telescope is closer to the source of the light, so it can make a clearer image.

C) Space telescopes are not affected by earthquakes. D) It is easier to launch very large space telescopes into space than to find places for them on the ground. Answer: A Section 6.4 1) Radio telescopes are generally ________ than visible-light telescopes. A) much larger B) much smaller C) much more expensive D) located at much higher altitudes Answer: A 2) The largest diameter telescopes are used to observe A) radio waves. B) infrared light. C) visible light. D) ultraviolet light. E) x-rays. Answer: A

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3) Which of the following would be the most useful ultraviolet telescope?

A) a 2.5-meter telescope in space B) a 30-meter telescope on a mountain C) a 1-meter telescope in space D) a 10-meter telescope on a mountain Answer: A 4) Which of the following best describes how and why x-ray telescopes differ from visible light telescopes?

A) X-ray telescopes use grazing incidence mirrors because x-ray photons will penetrate a normal mirror.

B) X-ray telescopes must be much larger because of the small number of x-ray photons.

C) X-ray telescopes cannot do spectroscopy because all x-ray photons have the same wavelength.

D) X-ray telescopes have to be built with very thick mirrors because x-ray photons will penetrate a thin mirror.

E) X-ray telescopes do not use mirrors because x-ray photons cannot be focused.

Answer: A 5) What does the technique of interferometry allow?

A) It allows two or more telescopes to obtain a total light-collecting area much larger than the total light-collecting area of the individual telescopes.

B) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.

C) It allows us to determine the chemical composition of stars.

D) It allows astronomers to make astronomical observations without interference from light pollution.

E) It allows the same telescope to make images with both radio waves and visible light.

Answer: B 6) Astronomers sometimes make use of "neutrino telescopes," which are typically located deep underground. What are neutrinos?

A) a type of light-weight subatomic particle B) a very high-energy form of light C) a very low-energy form of light D) a type of wave predicted to exist by Einstein's general theory of relativity Answer: A 7) Are cosmic rays a form of light?

A) No, they consist of high-energy subatomic particles, not of electromagnetic waves.

B) Yes, they are light waves with higher energy than gamma rays.

C) Yes, they are light waves with lower energy than radio waves.

D) Yes, they are the name we give to all rays of light that come from the cosmos.

Answer: A

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8) What are gravitational waves?

A) a type of energy that is different from light and that has been detected from sources such as merging neutron stars and black holes B) a form of light with higher energy than gamma rays C) a form of light with lower energy than radio waves D) the name we give to electromagnetic waves that come from astronomical objects that have gravity Answer: A 9) Which technology was used by the Event Horizon Telescope project to obtain the first image of a black hole?

A) gravitational wave detection B) adaptive optics C) interferometry D) high-speed time monitoring Answer: C General Chapter Questions 1) Which of the following telescopes is best suited for studying the hottest intergalactic gas (10 million K) in a cluster of galaxies?

A) Very Large Array Radio Telescope B) Hubble Space Telescope (UV, optical, and some infrared) C) Chandra X-ray Telescope D) Herschel Infrared Telescope Answer: C 2) Which of the following observational techniques is most appropriate for measuring Doppler shifts?

A) spectroscopy (taking a spectrum) B) imaging (taking a picture) C) time monitoring (measuring how the amount of light changes with time) Answer: A Short Answer Questions 1) Suppose an astronomer proposed to build a major, world class telescope (to observe visible light) on your school campus. Would your campus make a good observing site? Why or why not?

Answer: In general, campuses are bright environments and thus poor sites for optical telescopes.

The lights from local cities, and poor weather might also make for suboptimal conditions.

Nearby high elevation sites, if accessible, would be preferred.

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Reading Quiz Questions 1) Which of the following best describes what we mean by the focal plane of a telescope? A) It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope. B) It is the upper surface of the telescope's primary lens or mirror. C) It is the lower surface of the telescope's primary lens or mirror. D) It is the surface of the lens on the eyepiece, through which you would look to see objects in the telescope's field of view. Answer: A 2) When your eye forms an image, the ________ plays a role analogous to the detector in a camera. A) retina B) lens C) pupil D) optic nerve Answer: A 3) What does angular resolution measure? A) the angular size of the smallest features that the telescope can see B) the brightness of an image C) the size of an image D) the number of electromagnetic waves captured by an image Answer: A 4) What is the angular resolution of the human eye? A) about 1 arcminute, or 1/60 of a degree B) about 1 degree C) about 1 arcsecond (1/3600 of a degree) D) about 1 milliarcsecond Answer: A 5) Which of the following statements best describes the two principle advantages of telescopes over eyes? A) Telescopes can collect far more light with far better angular resolution. B) Telescopes can collect far more light with far greater magnification. C) Telescopes collect more light and are unaffected by twinkling. D) Telescopes have much more magnification and better angular resolution. Answer: A

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6) Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?

A) A refracting telescope uses a transparent glass lens to focus light, whereas a reflecting telescope uses a mirror to focus light.

B) A refracting telescope produces refracted images, whereas a reflecting telescope produces reflected images.

C) Reflecting telescopes make much clearer images than refracting telescopes of the same size.

D) It is much easier to make a large refracting telescope than a large reflecting telescope.

Answer: A 7) What do we mean by the diffraction limit of a telescope?

A) It is the angular resolution the telescope could achieve if nothing besides the size of its lightcollecting area affected the quality of its images.

B) It describes the farthest distance to which the telescope can see.

C) It is the maximum size to which any telescope can be built.

D) It describes the maximum exposure time for images captured with the telescope.

Answer: A 8) Which of the following is not one of the three main categories of observation generally used by astronomers?

A) filtering to look at just a single color from an object B) time monitoring to track how an object's brightness varies with time C) spectroscopy to spread an object's light into a spectrum D) imaging to get a picture of an astronomical objects Answer: A 9) Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have?

A) high spectral resolution B) high angular resolution C) high turbulence D) a radio telescope Answer: A 10) Which of the following is always true about images captured with x-ray telescopes?

A) They are always shown with colors that are not the true colors of the objects that were photographed.

B) They always are made with adaptive optics.

C) They show us light with extremely long wavelengths compared to the wavelengths of visible light.

D) They always have high angular resolution.

E) They are always pretty.

Answer: A

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11) What do astronomers mean by light pollution?

A) Light pollution is light from human sources that makes it difficult to see the stars at night.

B) Light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium.

C) Light pollution means contamination of light caused by chemicals in the Earth's atmosphere.

D) Light pollution is a term used to describe the appearance of the sky in regions that are crowded with stars.

Answer: A 12) The stars in our sky twinkle in brightness and color because of A) turbulence in the Earth's atmosphere.

B) rapid changes in the brightness and colors of stars caused by changes in their spectra.

C) light pollution.

D) the bubbling and boiling of gases on the surfaces of stars.

Answer: A 13) What is the purpose of adaptive optics?

A) It reduces blurring caused by atmospheric turbulence for telescopes on the ground.

B) It allows several small telescopes to work together like a single larger telescope.

C) It is a special technology that allows the Hubble Space Telescope to adapt to study many different types of astronomical objects.

D) It allows ground-based telescopes to observe ultraviolet light that normally does not penetrate the atmosphere.

Answer: A 14) Which of the following wavelength regions can be studied with telescopes on the ground?

A) radio, visible, and very limited portions of the infrared and ultraviolet regions B) all light with wavelengths longer than ultraviolet wavelengths C) all light with wavelengths shorter than infrared wavelengths D) infrared, visible, and ultraviolet light Answer: A 15) What is the purpose of interferometry?

A) It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.

B) It allows two or more small telescopes to achieve a larger light-collecting area than they would have independently.

C) It is designed to prevent light pollution from interfering with astronomical observations.

D) It reduces the twinkling of stars caused by atmospheric turbulence.

Answer: A

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16) Why are astronomers interested in building observatories capable of detecting neutrinos, cosmic rays, and gravitational waves?

A) These things are not forms of light, and therefore can provide different types of information than light about objects that emit them.

B) These things are the highest energy forms of light, even more energetic than gamma rays, and therefore can tell us about explosive processes in the universe.

C) These things should in principle be much easier to detect than light, which means we could build these observatories cheaply.

D) These things are emitted from the same objects that emit x-rays, but unlike x-rays they can be detected with observatories on the ground.

Answer: A Concept Quiz Questions 1) Why does the Sun's image look distorted in shape at sunset?

A) The distortion arises because of the way air affects the paths of light.

B) The distortion is an illusion that you notice by eye but does not show up in photographs.

C) Air scatters different colors of light by different amounts.

D) The distortion is an artifact of the photographic process that your eyes would not actually see.

Answer: A 2) Suppose you have a camera attached to a telescope, and you want to record an image of a faint galaxy. Which of the following will help the most?

A) a lot of pixels and a long exposure time B) a lot of pixels and a short exposure time C) a small number of pixels and a long exposure time D) a small number of pixels and a short exposure time Answer: A 3) Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp, while the other one becomes fuzzy (grainy) looking. Which of the following statements is true?

A) The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy.

B) The one that looks fuzzy at large size has better angular resolution (smaller) than the one that looks sharp.

C) Both photographs have the same angular resolution because they were both printed at the same sizes in each case.

D) Both photographs have the same angular resolution because they are both photographs of the same object.

Answer: A

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4) The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see? A) The photo will seem to show only one star rather than two. B) The two stars will appear to be touching, looking rather like a small dumbbell. C) The stars will not show up at all in your photograph. D) You will see two distinct stars in your photograph. Answer: A 5) The lightcollecting area of an 8-meter telescope is ________ times that of a 2-meter telescope. A) 16 B) 4 C) 8 D) 6 Answer: A 6) Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light? A) Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light. B) Radio telescopes are designed to collect sound rather than light. C) It is because radio telescopes are used in the daytime and visible light telescopes are used at night. D) Objects that emit radio waves are always much larger than objects that emit visible light, and therefore require larger telescopes. Answer: A 7) Which of the following studies is best suited to astronomical observations that fall into the category called time monitoring? A) studying how a star's brightness varies over a period of 3 years B) studying how different planets differ in their surface compositions C) measuring the rotation rate of a distant star D) determining the age of the solar system Answer: A 8) Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates? A) The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping. B) Being on a high mountain top means being relatively high in the atmosphere, which tends to limit turbulence. C) Dry regions mean less rain and clouds, and mountaintops in dry regions may even allow some infrared observations. D) Mountaintops far from cities are generally subject to less light pollution than locations nearer to cities. Answer: A

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9) Which of the following effects is caused by atmospheric turbulence?

A) twinkling of stars B) light pollution C) magnification of images D) diffraction of light Answer: A 10) Which of the following is not an advantage of the Hubble Space Telescope over groundbased telescopes?

A) It is closer to the stars.

B) Stars do not twinkle when observed from space.

C) It can observe infrared and ultraviolet light, as well as visible light.

D) It never has to close because of cloudy skies.

Answer: A 11) The Chandra X-ray Observatory must operate in space because A) x-rays do not penetrate Earth's atmosphere.

B) x-rays are too dangerous to be allowed on the ground.

C) x-ray telescopes require the use of grazing incidence mirrors.

D) it was built by NASA. Answer: A 12) Which of the following telescopes benefits most from adaptive optics?

A) the Keck I telescope on Mauna Kea B) the Hubble Space telescope C) the Arecibo radio telescope in Puerto Rico D) the Chandra X-ray Observatory Answer: A 13) Why can't x-ray and gamma-ray telescopes use the same designs as visible-light telescopes?

A) X-rays and gamma rays have so much energy that they cannot be reflected in the same way as visible light.

B) X-rays and gamma rays do not penetrate Earth's atmosphere.

C) X-rays and gamma rays are so intense that they would melt the glass in a visible-light telescope.

D) Visible-light telescopes can only reflect light that we see, not any other kind of light.

Answer: A 14) Astronomers have begun to build instruments to detect "cosmic messengers" that are not forms of light, such as neutrinos, cosmic rays, and gravitational waves, because they A) provide information about distant objects that we cannot obtain from light.

B) provide higher angular resolution than we can obtain with light.

C) are unaffected by the turbulence of Earth's atmosphere.

D) can allow us to see beyond the horizon of the observable universe.

Answer: A

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15) Consider two future observatories in space: Observatory A consists of a single 50meter telescope. Observatory B is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.) A) Observatory A can detect dimmer stars, and Observatory B reveals more detail in images. B) Observatory B can detect dimmer stars, and Observatory A reveals more detail in images. C) Observatory A both detects dimmer stars and reveals more detail in images. D) Observatory B both detects dimmer stars and reveals more detail in images. E) Both observatories have the same capabilities, but Observatory B would be cheaper to build. Answer: A Visual Quiz Questions 1) Notice the numbered points on this diagram of a reflecting telescope. Which point represents the place where the starlight is in focus?

A) Point 1 B) Point 2 C) Point 3 D) None of the listed choices is correct. This telescope has no focus because there is a hole in the primary mirror.

Answer: A

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2) Notice the numbered points on this photo of the Gemini North reflecting telescope. Where is the secondary mirror located?

A) Point 1 B) Point 2 C) Point 3 D) Point 4 Answer: C 3) This photo shows a single star photographed by the Hubble Space Telescope. Why doesn't the star appear as a single, sharp point of light?

A) The wave properties of light make this type of blurring an unavoidable feature of any telescope.

B) We are seeing a planetary system around the star.

C) The image of the star is overexposed.

D) The telescope was not properly focused when it took this photo.

Answer: A

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4) The first telescopic photo shows what appears to be a single star. The second photo shows the same object, now revealed to be two distinct stars. What is the difference between the two photos?

A) The second photo has better (smaller) angular resolution than the first photo.

B) The second photo was taken with a telescope that has greater light-collecting area.

C) The second photo was taken by two telescopes rather than one.

D) The second photo comes from a radio telescope, whereas the first photo comes from a visiblelight photo.

Answer: A 5) This x-ray image was taken by the Chandra X-ray Observatory. Without knowing anything more about the object that is shown, what can you conclude from looking at this image?

A) Some parts of the object emit more x-rays than others.

B) The x-rays from this object come in a variety of different colors.

C) This object emits much more light in the form of x-rays than in the form of visible light.

D) Yellow regions emit the highest-energy x-rays and red regions emit the lowest-energy x-rays.

Answer: A

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6) This graph shows alight curvefor a star. What can you conclude from this graph?

A) The star periodically dims and brightens, with a brightness peak about once a year.

B) The star is orbited by a large planet.

C) The star is about 100 times as bright as the Sun. D) The star is moving alternately toward and away from us.

Answer: A 7) What do you see orbiting Earth in this photo?

A) the Hubble Space Telescope B) the world's largest visible-light telescope C) the Spitzer infrared telescope D) the International Space Station Answer: A

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8) This diagram shows the approximate depths to which different wavelengths of light penetrate Earth's atmosphere. Why does it show an airplane?

A) Much of the infrared spectrum can be observed from an airplane that flies above most clouds.

B) Airplanes are useful for astronomical observations at all wavelengths of light that do not reach the ground.

C) Telescopes on airplanes are better than telescopes on the ground for both visible-light and infrared observations.

D) The airplane is just decorative, indicating that astronomers use airplanes to fly to groundbased observatories.

Answer: A 9) This photo shows a satellite dish on a house. In essence, the dish is

A) the primary mirror of a radio telescope.

B) a decoding device that translate radio signals into video.

C) a tiny interferometer.

D) a receiver with high angular resolution that makes it capable of displaying high-definition television.

Answer: A

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10) What kinds of light are these telescopes designed to detect?

A) radio waves B) x-rays C) infrared and visible light D) ultraviolet light E) light with extremely short wavelengths Answer: A

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

The figure repeats the portion of Figure 6.23 showing the approximate depths to which different wavelengths of light penetrate Earth's atmosphere. Use this figure to answer the following questions.

1) Only very small amounts of infrared and ultraviolet light can penetrate all the way to the ground. Based on the diagram, which statement is? true A) A small percentage of the incoming light at every infrared and ultraviolet wavelength reaches the ground, while the remaining light at the same wavelengths does not reach the ground.

B) Most infrared and ultraviolet wavelengths do not reach the ground at all; the only wavelengths that do are the ones closest to the visible portion of the spectrum.

C) Most infrared and ultraviolet wavelengths do not reach the ground at all; the only wavelengths that do are the ones closest to the radio and x-ray portions of the spectrum.

Answer: B 2) (Choose all that apply.) Observatories on mountaintops can detect A) visible light.

B) x-rays.

C) a small portion of the infrared spectrum.

D) very-long-wavelength infrared light.

E) radio waves.

Answer: A, C, E

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3) (Choose all that apply.) An observatory in space could in principle detect A) visible light.

B) x-rays. C) infrared light. D) ultraviolet light. E) radio waves. F) gamma rays. Answer: A, B, C, D, E, F 4) What kind of light can be detected from an airplane but not from the ground?

A) most infrared light B) only the shortest-wavelength infrared light C) radio waves D) xrays Answer: A Chapter Review Questions 1) How does your eye focus light? How is a glass lens similar? What do we mean by the focal plane of a lens? 2) How does a camera record light? How are images affected by exposure time? What are pixels? 3) What are the two key properties of a telescope, and why is each important? 4) What is the diffraction limit, and how does it depend on a telescope's size and the wavelength of light being observed? 5) How do reflecting telescopes differ from refracting telescopes? Which type is more commonly used by professional astronomers, and why? 6) What are the three basic categories of astronomical observation, and how is each conducted? 7) What do we mean when we speak of images made from invisible light, such as x-ray or infrared images? What do the colors in these images mean? 8) What do we mean by spectral resolution? Why is higher spectral resolution more difficult to achieve? 9) List at least three ways in which Earth's atmosphere can hinder astronomical observations. What problem can adaptive optics help with? 10) Describe how deeply each portion of the electromagnetic spectrum penetrates Earth's atmosphere. Based on your answers, why are space telescopes so important? 11) Briefly describe how telescopes for invisible wavelengths differ from those for visible light. Besides light, what other types of "cosmic messengers" can astronomers now observe?

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12) What isinterferomet ry, and how can it improve astronomical observations?

Does It Make Sense?

Decide whether or not each of the following statements makes sense (or is clearly true or false).

Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.

Example: I walked east from our base camp at the North Pole.

Solution: The statement does not make sense because east has no meaning at the North Pole–all directions are south from the North Pole.

13) The image was blurry because the detector was not placed at the focal plane.

14) I wanted to see faint details in the Andromeda Galaxy, so I photographed it with a very short exposure time.

15) I have a reflecting telescope in which the secondary mirror is bigger than the primary mirror.

16) The photograph shows what appear to be just two distinct stars, but each of those stars is actually a binary star system.

17) My 14-inch telescope has a lower diffraction limit than most large professional telescopes.

18) Now that I've bought a spectrograph, I can use my home telescope for spectroscopy as well as imaging.

19) If you lived on the Moon, you'd never see stars twinkle.

20) New technologies will soon allow astronomers to use x-ray telescopes on Earth's surface.

21) Thanks to adaptive optics, telescopes on the ground can now make ultraviolet images of the cosmos.

22) Thanks to interferometry, a properly spaced set of 10-meter radio telescopes can achieve the angular resolution of a single 100-kilometer radio telescope.

Quick Quiz

23) How much greater is the light-collecting area of a 6-meter telescope than that of a 3-meter telescope?

A) two times B) four times C) six times Answer: No Correct Answer Was Provided.

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24) Suppose you look at two stars that are separated in the sky by 0.1 arcsecond, using a telescope with an angular resolution of 0.5 arcsecond. What will you see?

A) two distinct stars B) one point of light that is the blurred image of both stars C) nothing at all Answer: No Correct Answer Was Provided.

25) The diffraction limit is a limit on a telescope's A) size.

B) angular resolution.

C) spectral resolution.

Answer: No Correct Answer Was Provided.

26) The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is A) larger.

B) closer to the stars.

C) above Earth's atmosphere.

Answer: No Correct Answer Was Provided.

27) What does it mean if you see the color red in an x-ray image from the Chandra X-Ray Observatory?

A) The object is red in color.

B) The red parts are hotter than the blue parts.

C) It depends; the colors are chosen arbitrarily to represent something about the x-rays recorded by the telescope.

Answer: No Correct Answer Was Provided.

28) The twinkling of stars is caused by A) variations in stellar brightness with time.

B) light pollution.

C) motion of air in our atmosphere.

Answer: No Correct Answer Was Provided.

29) To achieve the same angular resolution as a visible-light telescope, a radio telescope would need to be A) much larger.

B) slightly larger.

C) in space.

Answer: No Correct Answer Was Provided.

30) Where should you put a telescope designed for ultraviolet observations?

A) in Earth orbit B) on an airplane C) on a high mountaintop Answer: No Correct Answer Was Provided.

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31) Which technology can allow a single ground-based telescope to achieve images as sharp as those from the Hubble Space Telescope?

A) adaptive optics B) grazing incidence mirrors C) interferometry Answer: No Correct Answer Was Provided.

32) Interferometry uses two or more telescopes to achieve A) a light-collecting area equivalent to that of a much larger telescope.

B) an angular resolution equivalent to that of a much larger telescope.

C) both the light-collecting area and the angular resolution of a much larger telescope.

Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

33) A Telescope Near You.For either your current residence, your birthplace, or your home town, find the location of the nearest ground-based, visible-light telescope with a mirror larger than about 2 meters in diameter. What is this telescope used for? Is it open to the public? Discuss whether or how you think this telescope may benefit your community.

34) Pair Discussion: The Herschels. William and Caroline Herschel–brother and sister–were pioneers in using large telescopes to study the night sky. a) Working independently, find out when the Herschels lived, the kinds of telescopes they had at their disposal, and the major accomplishments credited to each of them. b) Pair up with another student, and decide which one of you will focus on William and which one on Caroline. Then take a turn describing the major accomplishments of the sibling you focus on. c) Discuss the relationship between William and Caroline Herschel. Were they equal partners?

Did they have similar opportunities to make major astronomical discoveries? Why or why not?

The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

35) Technology-Driven Science.Choose one technology described in this chapter and summarize how its development (or improvement) has allowed us to learn more about the universe. Then discuss how we might expect this technology to improve further during the next few decades, and identify at least one currently unanswered question about the universe that will likely be answered with the help of the improved technology.

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36) Research Funding. Technological innovation clearly drives scientific discovery in astronomy, but the reverse is also true. For example, Newton made his discoveries in part because he wanted to explain the motions of the planets, but his discoveries led to new technologies that have had far-reaching effects on our civilization. Congress often must decide between funding programs with purely scientific purposes (basic research) and programs designed to develop new technologies. If you were a member of Congress, how would you allocate spending between basic research and technology? Why? 37) LIGO. Learn about how the Laser Interferometer Gravitational-wave Observatory (LIGO) detects gravitational waves. How small are the length changes it can measure in its arms? Why do astronomers need more than one detector to be confident of its discoveries? Briefly summarize how LIGO works and its latest discoveries.

38) Group Activity: Which Telescope? You represent a research group that wishes to observe matter around a black hole; assume that the matter is emitting photons at all wavelengths. You have the opportunity to make your observations with one of the following four telescopes: • A radio telescope, 300 meters in diameter, located in Puerto Rico • An infrared telescope, 2 meters in diameter, on a spacecraft in orbit around Earth and observing at a wavelength of micrometers (2 × 10−6 m) • An infrared telescope, 10 meters in diameter, equipped with adaptive optics, located on Mauna Kea in Hawaii and observing at a wavelength of micrometers (10−5 m) • An x-ray telescope, 2 meters in diameter, located at the South Pole Discuss the pros and cons of each telescope for this observing task, then come to a group consensus in which you rank the four choices from best to worst. Compare your rankings to those of other groups in your class. Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39.

Investigate Further

39) Image Resolution. What happens if you take a photograph and blow it up to a larger size? Does it contain more detail than it did before? Explain clearly, and relate your answer to the concepts of magnification and angular resolution in astronomical observations.

40) Filters. What would an American flag look like if you viewed it through a filter that transmits only red light? What would it look like through a filter that transmits only blue light?

41) Type of Observation. For each of the following, decide what type of observation (imaging, spectroscopy, timing) you would need to make. Explain clearly. a) Studying how a star's hot upper atmosphere changes with time b) Learning the composition of a distant star c) Determining how fast a distant galaxy is moving away from Earth 42) Telescope Location. Considering the pros and cons of different locations for groundbased

25

Copyright 2020 Pearson Inc. observatories, do you think the place©where you liveEducation, is a good location for a visible-light telescope? Why or why not?

43) Technology Choice. Suppose you were building a space-based observatory consisting of five individual telescopes. Which would be the better way to use these telescopes: as five individual telescopes with adaptive optics or as five telescopes linked together for interferometry (without adaptive optics)? Explain your reasoning clearly.

44) Major Ground-Based Observatories. Take a virtual tour of one of the world's major astronomical observatories. Write a short report on why the observatory is so useful.

45) Space Observatory. Visit the website of a major space observatory, either existing or under development. Write a short report about the observatory, including its purpose, its orbit, and how it operates.

46) Really Big Telescopes. Learn about one of the projects to build a very large telescope, such as the Giant Magellan Telescope, the Thirty Meter Telescope, or the European Extremely Large Telescope. Write a short report about the telescope's current status and potential capabilities.

47) A Lunar Observatory. Some people have proposed building an astronomical observatory on the Moon. Research the pros and cons of this idea, considering it both in isolation and in the context of plans for a human return to the Moon. If it were up to you, would you recommend that Congress begin funding a program to develop such an observatory? Defend your opinion.

48) Project: Twinkling Stars. Using a star chart, identify a few bright stars that should be visible in the early evening. On a clear night, observe each of these stars for a few minutes. Note the date and time, and for each star record the following information: approximate altitude and direction in your sky, brightness compared to other stars, color, and how much the star twinkles compared to other stars. Study your record. Can you draw any conclusions about how brightness and position in your sky affect twinkling? Explain.

49) Project: Personal Telescope Review. Find three telescopes that you could buy for under $1000 and evaluate each on the following criteria: light-collecting area, angular resolution, construction quality, and portability. Give each telescope a rating of 1 to 4 stars (4 is best), and state which one you would recommend for purchase.

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

50) Light-Collecting Area. a) How much greater is the light-collecting area of one of the 10-meter Keck telescopes than that of the 5-meter Hale telescope? b) Suppose astronomers built a 100-meter telescope. How much greater would its light-collecting area be than that of the 10-meter Keck telescope?

51) Close Binary System. Suppose that two stars in a binary star system are separated by a distance of 100 million kilometers and are located at a distance of 100 light-years from Earth.

What is the angular separation of the two stars? Give your answer in both degrees and arcseconds. Can the Hubble Space Telescope resolve the two stars?

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52) Finding Planets. Suppose you were looking at our own solar system from a distance of 10 light-years. a) What angular resolution would you need to see the Sun and Jupiter as distinct points of light? b) What angular resolution would you need to see the Sun and Earth as distinct points of light? c) How do the angular resolutions you found in parts a and b compare to the angular resolution of the Hubble Space Telescope? Comment on the challenge of making images of planets around other stars.

53) Diffraction Limit of the Eye. a) Calculate the diffraction limit of the human eye, assuming a wide-open pupil so that your eye acts like a lens with a diameter of 0.8 centimeter, for visible light of 500-­nanometer wavelength. How does this compare to the diffraction limit of a 10-meter telescope? b) Now remember that humans have two eyes that are approximately 7 centimeters apart.

Estimate the diffraction limit for human vision, assuming that your two eyes act as an "optical interferometer" that gives you the angular resolution of a single "eye" that is 7 centimeters in diameter. 54) The Size of Radio Telescopes. What is the diffraction limit of a 100-meter radio telescope observing radio waves with a wavelength of 21 centimeters?

Compare this to the diffraction limit of the Hubble Space Telescope for visible light. Use your results to explain why, to be useful, radio telescopes must be much larger than optical telescopes. 55) Your Satellite Dish. Suppose you have a satellite dish that is 0.5 meter in diameter and you want to use it as a radio telescope. What is the diffraction limit on the angular resolution of your dish, assuming that you want to observe radio waves with a wavelength of 21 centimeters? Would it be very useful as an astronomical radio telescope?

56) Hubble's Field of View. Large telescopes often have small fields of view. For example, the advanced camera of the Hubble Space Telescope (HST) has a field of view that is roughly square and about 0.06° on a side. a) Calculate the angular area of the HST's field of view in square degrees. b) The angular area of the entire sky is about 41,250 square degrees. How many pictures would the HST have to take with its camera to obtain a complete picture of the entire sky? 57) Hubble Sky Survey? In Problem 56, you found out how many pictures the HST would need to take to photograph the entire sky. If you assume that it would take 1 hour to produce each picture, how many years would it take the HST to obtain photos of the entire sky? Use your answer to explain why astronomers would like to have more than one large telescope in space. 58) Visible-Light Interferometry.

Technological advances are now making it possible to link visible-light telescopes so that they can achieve the same angular resolution as a single telescope over 300 meters in size.

What is the angular resolution (diffraction limit) of such a system of telescopes for observations at a wavelength of 500 nanometers?

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The Cosmic Perspective, 9e (Bennett et al.)

Chapter 7 Our Planetary System Section 7.1 1) How much of the solar system's total mass is contained in the Sun? A) about half B) about 90% C) about 95% D) about 99.8% E) exactly 100% Answer: D 2) If we could combine all the planets together, their total mass would be about ________ the Sun's mass.

A) 1/1000 of B) 1/10 of C) the same as D) double E) half of Answer: A 3) Where does nuclear fusion occur in the Sun? A) on the surface B) in a layer just below the surface C) deep in its core D) in a layer just above the visible surface E) all of the above Answer: C 4) Which planet has the most extreme differences between its daytime and nighttime temperatures?

A) Mercury B) Venus C) Earth D) Mars E) Jupiter Answer: A 5) Which planet is most similar in size and mass to Earth?

A) Mercury B) Venus C) Mars D) Jupiter E) Neptune Answer: B

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6) What is surprising about Earth's Moon?

A) It is surprisingly large in comparison to the size of its planet.

B) It orbits surprisingly far away from Earth.

C) It has a surprisingly large number of craters.

D) The fact that it lacks a significant atmosphere.

Answer: A 7) Which of the following indicates that past conditions on Mars may have been suitable for life?

A) There are very large extinct volcanoes on Mars.

B) Mars has two small Moons, Phobos, and Deimos.

C) There are dried up riverbeds, rock-strewn floodplains, and minerals that form in water.

D) Mars has polar caps.

E) Mars has been studied by numerous spacecraft, including both orbiters and landers.

Answer: C 8) Which planet is orbited by the four "Galilean moons" known individually as Io, Europa, Ganymede, and Callisto?

A) Saturn B) Uranus C) Mars D) Jupiter E) Neptune Answer: D 9) The most massive planet in our solar system is A) Saturn.

B) Uranus.

C) Mars.

D) Jupiter.

E) Neptune.

Answer: D 10) Uranus's large axis tilt causes it to A) have extreme seasonal variations.

B) be very hot.

C) be very cold.

D) have very short days and nights.

E) keep one side facing the Sun at all times.

Answer: A

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11) Neptune's largest moon, Triton, orbits in a direction opposite to the direction in which Neptune rotates. Which of the following is most likely implied by this fact?

A) Triton experiences very strong tidal forces.

B) Triton probably formed as the result of a giant impact.

C) Triton probably was captured into orbit by Neptune.

D) Triton probably formed in its current orbit around Neptune.

E) Triton probably has a rocky, asteroid-like composition.

Answer: C 12) Which statement about Pluto is not true?

A) Its surface temperature is very cold.

B) It is made mostly of rock and ice.

C) It is both smaller and less massive than Earth.

D) It is the most massive object in the Kuiper belt.

E) It was visited by the New Horizons spacecraft in 2015.

Answer: D 13) Which of the following factors was very important to the decision to classify Pluto as a dwarf planet rather than a "regular" planet?

A) its small size and mass B) its large distance from the Sun C) its composition of ice and rock D) its relatively large moon, Charon Answer: A 14) In what region of the solar system is Pluto found?

A) the asteroid belt B) the Kuiper belt C) the Oort cloud D) the terrestrial planet region Answer: B 15) Which planet has the highest average surface temperature and why?

A) Mercury, because it is closest to the Sun B) Mercury, because of its dense carbon dioxide atmosphere C) Venus, because of its dense carbon dioxide atmosphere D) Mars, because of its red color E) Jupiter, because it is so big Answer: C 16) Other than Earth, which of the following has visible polar caps?

A) Mercury B) Venus C) The Moon D) Mars E) Jupiter Answer: D

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17) Which of the following worlds could an astronaut visit without the need for a spacesuit (and survive)? A) Mercury B) Venus C) The Moon D) Mars E) None of the above; an astronaut would need a spacesuit to survive a visit to any world in the solar system (aside from Earth). Answer: E Section 7.2 1) Which of the following is not an observed pattern of motion in our solar system? A) Most planets orbit the Sun at the same speed. B) All planets orbit the Sun in the same direction. C) Most planetary orbits lie nearly in the same plane. D) Most planets rotate in the same direction in which they orbit. E) Almost all moons orbit their planet in the same direction as the planet's rotation. Answer: A 2) Which of the following planets has a ring system? A) Jupiter B) Saturn C) Uranus D) Neptune E) All of the above Answer: E 3) Which of the following is not a characteristic of all the terrestrial planets? A) They are smaller than the jovian planets. B) They have solid, rocky surfaces. C) They are located closer to the Sun than the jovian planets. D) They have substantial atmospheres. E) They have higher densities than the jovian planets. Answer: D 4) Which of the following is not a characteristic of the jovian planets? A) They have higher average densities than the terrestrial planets. B) They have thick atmospheres. C) They are primarily made of hydrogen, helium, and hydrogen compounds. D) They are located further from the Sun than the terrestrial planets. E) They have rings. Answer: A

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5) Which of the following best described the major ingredients of the jovian planets?

A) rocky minerals and water B) hydrogen, helium, and hydrogen compounds C) rock and metal D) hydrogen compounds and carbon dioxide E) hydrogen and helium only Answer: B 6) Where are most asteroids found?

A) between the orbits of Mars and Jupiter B) between the orbits of Jupiter and Saturn C) in the Oort cloud D) inside the orbit of Earth E) between the orbits of Earth and Mars Answer: A 7) The Oort cloud is A) a roughly spherical region larger than the orbit of Pluto that may contain a trillion comets.

B) a region in the same plane as the planets that contains hundreds of thousands of comets.

C) a circular region between the orbits of Mars and Jupiter that contains most known asteroids.

D) the cloud of gas from which the solar system formed.

E) a vast cloud of gas that encircles the solar system at a great distance from the Sun. Answer: A 8) Which of the following is farthest from the Sun? A) Pluto B) Neptune C) an asteroid in the asteroid belt D) a comet in the Kuiper belt E) a comet in the Oort cloud Answer: E 9) What is the major difference between asteroids and comets?

A) Asteroids are rocky and comets are icy.

B) Asteroids are low in density and comets are high in density.

C) Asteroids never have tails and comets always have tails.

D) Asteroids are smaller than comets.

E) Asteroids are larger than comets.

Answer: A 10) Astronomers estimate the total number of comets in the solar system to be about A) 100 million.

B) 1 billion.

C) 10 billion.

D) 100 billion.

E) 1 trillion.

Answer: E

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11) Which of the following is not an exception to the general patterns in the solar system?

A) the "backward" rotation of Venus B) the relatively large size of Earth's Moon compared to Earth C) the fact that Saturn has rings D) the extreme axis tilt of Uranus E) the "backward" orbit of Triton around Neptune Answer: C 12) What is unusual about the planet Venus? A) It rotates in a direction opposite to the direction of its orbit. B) It orbits the Sun faster than it should give the size of its orbit. C) It orbits the Sun in a direction opposite that of all the other planets. D) It does not orbit the Sun in the same plane as the other planets.

E) It rotates extremely rapidly around its axis. Answer: A Section 7.3 1) Which of the following is a significant drawback for a flyby mission as compared to an orbiter to a distant world? A) The flyby cannot have instruments as sophisticated as the orbiter. B) The flyby cannot get as close to the planet as the orbiter. C) The flyby cannot reach the planet as quickly as the orbiter. D) The flyby can study the planet for a much shorter time than the orbiter. Answer: D 2) When scientists speak of a "sample return mission" to Mars, what do they mean? A) a mission that scoops up rock on Mars and brings it to Earth B) a mission that provides an example of how other missions might work in the future C) a mission that lands humans on Mars D) a mission that reuses a spacecraft that has already been to Mars once Answer: A 3) Which of the following is a technique that can be used to speed up a spacecraft without the need for extra fuel? A) a gravitational slingshot, in which the spacecraft gains momentum by flying near a planet B) releasing unnecessary weight after takeoff to make the spacecraft lighter C) flattening after takeoff to make the spacecraft more aerodynamic D) landing on a fast-moving asteroid and relaunching at high speed E) collect material in space that can power the spacecraft Answer: A

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4) Why would it not be a good idea to send a lander to one of the jovian planets? A) The jovian planets have no solid surface to land on. B) The jovian planets are too far away. C) It would be impossible to slow the lander down sufficiently to avoid a catastrophic crash.

D) There's too much risk of hitting a boulder in the planet's rings on the way down. E) There is nothing interesting to find on the jovian planets. Answer: A General Chapter Questions 1) Which planet experiences the strongest gravitational force from the Sun? A) Mercury B) Earth C) Jupiter D) Saturn E) Neptune Answer: A Short Answer Questions 1) Describe at least two things that make Earth unique in the solar system? Answer: Possible answers: It is the only planet with an oxygen-rich atmosphere and abundant liquid water on its surface. Its surface temperature is such that water can exist in three phases: solid, liquid, and gaseous. Compared to its size, Earth also has a very large moon.

It is the only planet with plate tectonics. It is the only planet we know of that harbors life.

2) Identify at least three patterns of motion or planetary arrangement/location that a theory of solar system formation should be able to explain. Answer: Answers may include: 1. Planets orbit in the same direction. 2. Orbital direction is the same direction as the Sun's spin. 3. Most planets spin in the same direction that they orbit. 4. Bigger planets are in the outer solar system. 5. Large planets have many moons. 6. Planets lie in approximately the same plane. 3) List at least three of the notable exceptions to the general patterns of the solar system. Answer: Several possibilities: (a) The rotational axes of Uranus and Pluto are substantially tilted. (b) Venus rotates backward, that is, clockwise. (c) Unlike other terrestrial planets, Earth has a large moon. (d) Some of the moons of the jovian planets orbit in the opposite direction of their planets' rotation.

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Reading Quiz Questions 1) Which of the following lists the planets of our solar system in the correct order from closest to farthest from the Sun? A) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune B) Mercury, Earth, Venus, Mars, Jupiter, Saturn, Neptune, Uranus C) Mercury, Venus, Mars, Earth, Saturn, Jupiter, Neptune, Uranus D) Earth, Mars, Mercury, Venus, Jupiter, Saturn, Uranus, Neptune Answer: A 2) Suppose you view the solar system from high above Earth's North Pole. Which of the following statements about planetary orbits will be true? A) All the planets orbit counterclockwise around the Sun. B) The inner planets orbit the Sun counterclockwise, whereas the outer planets orbit the Sun clockwise. C) All the planets except Uranus orbit the Sun counterclockwise; Uranus orbits in the opposite direction. D) The inner planets orbit the Sun clockwise, whereas the outer planets orbit the Sun counterclockwise. Answer: A 3) Which of the following statements about our Sun is not true? A) The Sun's diameter is about 5 times that of Earth. B) The Sun is a star. C) The Sun contains more than 98% of all the mass in our solar system. D) The Sun is made mostly of hydrogen and helium. Answer: A 4) Which of the following is not true of Mercury? A) Even on Mercury's night side, the temperature is hot enough to melt lead. B) Mercury rotates exactly three times for every two orbits it makes around the Sun. C) Its surface is heavily cratered. D) Mercury has essentially no atmosphere. Answer: A 5) Which of the following statements about Mars is not true? A) We could survive on Mars without spacesuits, as long as we brought oxygen in scuba tanks. B) We have landed robotic spacecraft on its surface. C) It has mountains that are taller than the tallest mountains on Earth. D) Its surface is frozen today, but evidence indicates it had flowing water in the distant past. Answer: A

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6) The planet in our solar system with the highest average surface temperature is A) Venus B) Mercury C) Earth D) Neptune Answer: A 7) Which moons of our solar system are sometimes called the Galilean moons? A) the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto B) the two largest moons in the solar system: Ganymede and Titan C) the moons that orbit their planet "backward" compared to their planet's rotation, such as Neptune's moon Triton D) the moons orbiting Uranus, which was once named "planet Galileo" Answer: A 8) Which of the following statements about Pluto is true? A) It has more in common with other icy objects in the Kuiper belt than it does with the jovian planets (Jupiter, Saturn, Uranus, Neptune). B) It is the most massive object that orbits the Sun beyond the orbit of Neptune. C) It is orbited by only one moon. D) It is the only object in our solar system that is categorized as a "dwarf planet." Answer: A 9) The terrestrial planets in our solar system are A) Mercury, Venus, Earth, and Mars. B) Jupiter, Saturn, Uranus, and Neptune. C) Pluto and Eris. D) Mars, Jupiter, Saturn, Uranus, and Neptune. Answer: A 10) The jovian planets in our solar system are A) Jupiter, Saturn, Uranus, and Neptune. B) Mercury, Venus, Earth, and Mars.

C) Pluto and Eris. D) Io, Europa, Ganymede, and Callisto. Answer: A 11) Which jovian planets in our solar system have rings? A) Saturn only B) Jupiter and Saturn only C) all but Neptune D) all four of the jovian planets have rings. Answer: D

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12) When we say that jovian planets contain significant amounts of , hydrogen compounds except we mean all the following chemicals except A) carbon dioxide.

B) water.

C) ammonia.

D) methane.

Answer: A 13) Which of the following most clearly distinguishes asteroids and comets from planets?

A) Asteroids and comets are much smaller than planets.

B) Asteroids and comets are made of different materials than any planets.

C) Unlike planets, asteroids and comets do not orbit the Sun. D) Asteroids and comets are only found at much greater distances from the Sun than planets.

Answer: A 14) What is the Kuiper belt?

A) a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets B) a region of the solar system that extends almost a fourth of the way to the nearest stars and contains a trillion comets with orbits going in all directions around the Sun C) a technical name for the asteroid belt D) the most prominent ring of Saturn that is visible in photographs Answer: A 15) What is the Oort cloud?

A) It's not really a cloud at all, but rather refers to the trillion or so comets thought to orbit the Sun at great distances.

B) It is another name for the cloud of gas from which our solar system was born.

C) It is a great cloud of gas that resides far beyond the orbit of Pluto.

D) It is a giant storm in the atmosphere of Saturn.

Answer: A 16) The spacecraft called Curiosity is A) a rover on Mars.

B) an orbiter studying Jupiter.

C) a robotic lander on Venus.

D) currently orbiting Saturn.

Answer: A 17) Which of the following types of robotic mission to a planet is generally the cheapest?

(Assume that the spacecraft destination is the same in all cases.)

A) flyby B) orbiter C) lander D) sample return mission Answer: A

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Concept Quiz Questions 1) Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is A) much larger.

B) about the same.

C) much smaller.

D) just slightly less.

Answer: A 2) How is Einstein's famous equation, E = mc2, important in understanding the Sun? A) of It explains the fact that the Sun generates energy to shine by losing some 4 million tons

mass each day.

B) It explains why the Sun's surface temperature is about 6,000°C. C) It explains why the Sun is so massive.

D) It explains atmospheres of why the Sun has a magnetic field strong enough to influence the the planets.

Answer: A 3) Venus has a higher average surface temperature than Mercury. Why?

A) because its surface is heated by an extreme greenhouse effect B) because it is closer to the Sun C) because its surface is covered with hot lava from numerous active volcanoes D) because its slow rotation gives it more time to heat up in sunlight Answer: A 4) In what way is Venus most similar to Earth?

A) Both planets are nearly the same size.

B) Both planets have similar atmospheres.

C) Both planets have similar surface geology.

D) Both planets have warm days and cool nights.

Answer: A 5) Mars has two moons, Phobos and Deimos, that are most similar in character to A) small asteroids.

B) comets.

C) Earth's Moon.

D) particles in the rings of Saturn.

Answer: A 6) Imagine that an alien spaceship crashed onto Earth. Which statement would most likely be true?

A) It would crash in the ocean.

B) The aliens' home world is another planet in our own solar system.

C) The crash would create a noticeable crater.

D) 51 All in the evidence of the crash would be quickly whisked off by the U.S. military to Area Nevada.

Answer: A

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7) Which planet listed has the most extreme seasons?

A) Uranus B) Mars C) Earth D) Jupiter Answer: A 8) In which of the following ways are Pluto and Eris more like comets than like any of the terrestrial or jovian planets?

A) They are made mostly of rock and ice.

B) They sometimes enter the inner solar system.

C) They have long tails.

D) They have thick atmospheres.

Answer: A 9) Which of the following is not a major pattern of motion in the solar system?

A) Nearly all comets orbit the Sun in same direction and roughly the same plane.

B) Most of the solar system's large moons orbit in their planet's equatorial plane.

C) The Sun and most of the planets rotate in the same direction in which the planets orbit the Sun. D) All of the planets orbit the Sun in the same direction; counterclockwise as viewed from above Earth's north pole.

Answer: A 10) Which of the following is not a major difference between the terrestrial and jovian planets in our solar system?

A) Terrestrial planets contain large quantities of ice and jovian planets do not.

B) Terrestrial planets orbit much closer to the Sun than jovian planets.

C) Terrestrial planets are higher in average density than jovian planets.

D) Jovian planets have rings and terrestrial planets do not.

Answer: A 11) Consider the following statement: "Rocky asteroids are found primarily in the asteroid belt and Kuiper belt, while icy comets are found primarily in the Oort cloud." What's wrong with this statement?

A) The Kuiper belt contains icy comets, not rocky asteroids.

B) Asteroids are not really made of rock.

C) Comets are not really icy.

D) The Oort cloud has nothing to do with comets.

E) The statement is accurate as written.

Answer: A

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12) Which of the following is not a real difference between asteroids and comets?

A) Asteroids orbit the Sun, whereas comets just float randomly around in the Oort cloud.

B) Most asteroids are located much nearer to the Sun than most comets.

C) It is thought that comets are far more numerous than asteroids.

D) Asteroids are made mostly of rock and comets are made mostly of ice.

Answer: A 13) The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system?

A) The diameter of Earth's Moon is about 1/4 that of Earth.

B) Venus does not have a moon.

C) Jupiter has a small axis tilt.

D) Saturn has no solid surface.

Answer: A 14) Why was it advantageous for the Voyager missions to consist of flybys rather than orbiters?

A) Each individual spacecraft was able to visit more than one planet.

B) Spacecraft making flybys can return to Earth more quickly than orbiters.

C) It was easier for data to be radioed back to Earth with flybys than orbiters.

D) Flyby spacecraft can get closer to a planet than an orbiting spacecraft.

Answer: A 15) Why has NASA sent recent orbiters to Mars on trajectories that required them to skim through Mars's atmosphere before settling into their final orbits?

A) It saves money because the spacecraft uses atmospheric drag to slow down rather than needing to carry enough fuel to slow by firing rocket engines.

B) It allowed the orbiters to get higher resolution pictures of the surface as it came close when skimming through the atmosphere.

C) It allowed the spacecraft to collect samples of the atmospheric gas for return to Earth.

D) Each spacecraft also carried a lander, and the lander could only be dropped to the Martian surface when the spacecraft passed through the atmosphere.

Answer: A

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Visual Quiz Questions 1) This famous photograph taken by the Voyager spacecraft shows

A) Earth as viewed from the outskirts of the solar system.

B) a close-up of the rings of Neptune.

C) the cloud of gas and dust in which our solar system was born.

D) the Sun as viewed from the next-nearest star.

Answer: A 2) In this perspective view of the solar system, the sizes of the planets are ________ relative to the sizes of their orbits.

A) exaggerated about 1,000 times B) correctly scaled C) exaggerated about 10 times D) exaggerated about 100 million times Answer: A

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3) Which pair of photos shows Earth correctly scaled in comparison to the Sun? A)

B)

C)

D)

Answer: A

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4) Which pair of photos below shows Earth correctly scaled in comparison to Jupiter?

A)

B)

C)

D)

Answer: A

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5) What planet is this, and how do you know?

A) Saturn because of its colors and bright, wide rings B) Saturn because it is the only planet with rings C) Jupiter because it is the biggest planet and has the biggest rings D) Neptune because it has the brightest rings of any planet E) Jupiter because of its colors and bright, wide rings Answer: A 6) What do we see in this photo?

A) Neptune B) Venus C) Mars D) Pluto E) Eris Answer: A

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7) What object is shown in this photo?

A) Mars B) Venus C) Mercury D) Ganymede Answer: A 8) This photograph was taken on the surface of another world in our solar system. What world is it?

A) Mars B) Venus C) the Moon D) Triton Answer: A

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9) In this photograph, the large and bright object in the sky is

A) a comet.

B) an asteroid.

C) a meteor.

D) the northern lights Answer: A 10) This photo shows

A) an asteroid B) Pluto C) a dwarf planet D) Mercury Answer: A

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

The plots above show the masses of the eight major planets on the vertical axis and their radii on the horizontal axis. The plot on the left shows the information on a linear scale, meaning that each tick mark indicates an increase by the same amount. The plot on the right shows the same information plotted on an exponential scale, meaning that each tick mark represents another factor-of-ten increase. Before proceeding, convince yourself that the points on each plot are the same.

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1) Based on the information given in Table 7.1, which dots on each plot correspond to which planets? Which correspond to the terrestrial planets, and which to the jovian planets?

Answer: A = Mercury, B = Mars, C = Venus, D = Earth, E = Neptune, F = Uranus, G = Saturn, H = Jupiter; dots A to D are the terrestrial planets, and dots E to H are the jovian planets.

2) Notice how the eight planets group roughly into pairs on the graphs. Which planets are in each pair?

Answer: The pairs are Mercury and Mars, Venus and Earth, Neptune and Uranus, Saturn and Jupiter.

3) Which statement most accurately describes the relationship between the largest and smallest planets?

A) The largest planet is 6000 times as wide (in diameter) and 30 times as massive as the smallest.

B) The largest planet is 6000 times as wide (in diameter) and 6000 times as massive as the smallest.

C) The largest planet is 30 times as wide (in diameter) and 30 times as massive as the smallest.

D) The largest planet is 30 times as wide (in diameter) and 6000 times as massive as the smallest.

Answer: D 4) Answer each of the following questions to compare the two plots. a) Which plot, if either, better shows mass and radius information for all the planets? b) Which plot, if either, better emphasizes the differences between Jupiter and Saturn? c) Which plot, if either, could more easily be extended to show a planet with twice Jupiter's mass or radius?

Answer: a) The exponential plot on the right shows information on low-mass planets that can't be seen on the linear plot. b) The linear plot on the left c) The exponential plot on the right Chapter Review Questions 1) What do we mean by comparative planetology? Does it apply only to planets?

2) What would the solar system look like to your naked eye if you could view it from beyond the orbit of Neptune?

3) Briefly describe the overall layout of the solar system as it is shown in Figure 7.1. What are the four major features of our solar system that provide clues to how it formed?

4) For each of the objects in the solar system tour(pages 194—203), describe at least two features that you find interesting.

5) Briefly describe the patterns of motion that we observe among the planets and moons of our solar system.

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6) What are the basic differences between the terrestrial and jovian planets? Which planets fall into each group?

7) What do we mean by hydrogen compounds? In what kinds of planets or small bodies are they major ingredients?

8) What are asteroids? What are comets? Describe the basic differences between the two, and where we find them in our solar system.

9) What kind of object is Pluto? Explain.

10) What is the Kuiper belt? What is the Oort cloud? How do the orbits of comets differ in the two regions?

11) Describe at least two "exceptions to the rules" that we find in our solar system.

12) Describe and distinguish between space missions that are flybys, orbiters, landers or probes, and sample return missions. What are the advantages and disadvantages of each type?

Does It Make Sense?

Decide whether or not each of the following statements makes sense (or is clearly true or false).

Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.

Example: I walked east from our base camp at the North Pole.

Solution: The statement does not make sense because east has no meaning at the North Pole–all directions are south from the North Pole.

13) Uranus orbits the Sun in a direction opposite that of all the other planets.

14) If Pluto were as large as the planet Mercury, we would classify it as a terrestrial planet.

15) Comets in the Kuiper belt and Oort cloud have long, beautiful tails that we can see when we look through telescopes.

16) Our Moon is about the same size as moons of the other terrestrial planets.

17) The mass of the Sun compared to the mass of all the planets combined is like the mass of an elephant compared to the mass of a cat.

18) On average, Venus is the hottest planet in the solar system–even hotter than Mercury.

19) The weather conditions on Mars today are much different than they were in the distant past.

20) Moons cannot have atmospheres, active volcanoes, or liquid water.

21) Saturn is the only planet in the solar system with rings.

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22) We could probably learn more about Mars by sending a new spacecraft on a flyby than by any other method of studying the planet.

Quick Quiz 23) The largest terrestrial planet and jovian planet are, respectively A) Venus and Jupiter.

B) Earth and Jupiter.

C) Earth and Saturn.

Answer: No Correct Answer Was Provided.

24) Which terrestrial planets have had volcanic activity at some point in their histories?

A) only Earth B) Earth and Mars C) all of them Answer: No Correct Answer Was Provided.

25) How many of our solar system's large moons orbit their planets in the same direction as their planet rotates?

A) very few B) about half C) most Answer: No Correct Answer Was Provided.

26) Which of the following three kinds of objects resides closest to the Sun on average?

A) comets B) asteroids C) jovian planets Answer: No Correct Answer Was Provided.

27) What's unusual about our Moon?

A) It's the only moon that orbits a terrestrial planet.

B) It's by far the largest moon in the solar system.

C) It's surprisingly large relative to the planet it orbits.

Answer: No Correct Answer Was Provided.

28) Planetary orbits are A) very eccentric (stretched-out) ellipses and in the same plane.

B) fairly circular and in the same plane.

C) fairly circular but oriented in every direction.

Answer: No Correct Answer Was Provided.

29) Which have more moons on average?

A) jovian planets B) terrestrial planets C) Terrestrial and jovian planets both have about the same number of moons.

Answer: No Correct Answer Was Provided.

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30) The most abundant ingredient of the Sun and Jupiter is A) ionized metal.

B) hydrogen.

C) ammonia.

Answer: No Correct Answer Was Provided.

31) Are there any exceptions to the rule that planets rotate with small axis tilts and in the same direction as they orbit the Sun? A) no B) Venus is the only exception.

C) Venus and Uranus are exceptions.

Answer: No Correct Answer Was Provided.

32) The Cassini spacecraft A) flew past Pluto.

B) landed on Mars.

C) orbited Saturn.

Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

33) Group Discussion: Who Named the Planets?

The names of the five planets that can be seen with the naked eye have been in use in the western world for thousands of years. However, beginning with the discoveries of Uranus in 1781 and Neptune in 1846, scientists needed to find names for planets and other newly discovered objects. a) Working in small groups, find out how Uranus and Neptune came to have their current names in English. Do you think these name choices made sense? Do you think the process that led to these names was "fair"? Why or why not? b) Each member of your group should learn about the names of Uranus and Neptune in two other languages, at least one of which is non-European.

Discuss the similarities and differences you find among the names in different languages. c) Find out what names were considered for Pluto after its discovery in 1930, who suggested the name "Pluto," and how it came to be official. Are you surprised about who suggested the name? d) Find out how newly discovered objects (such as moons and asteroids) and surface features (such as those recently identified on Mars, Ceres, and Pluto) get their official names today. Do you think this process is appropriate? Make a list of other possibilities that might be considered (for example, allowing the discoverers to choose names or choosing through public, online competitions). If your group were in charge, would you change the current naming process in any way?

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The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

34) Why Wait? To explore a planet, we often send first a flyby, then an orbiter, then a probe or a lander. There's no doubt that probes and landers give the most close-up detail, so why don't we send this type of mission first? For the planet of your choice, based just on the information in this chapter, give an example of why such a strategy might cause a mission to provide incomplete information about the planet or to fail outright.

35) Planetary Priorities. Suppose you were in charge of developing and prioritizing future planetary missions for NASA. What would you choose as your first priority for a new mission, and why?

36) Group Activity: Comparative Approach. Work as a group to answer each part.Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39. a) This chapter advocates learning about how planets work by comparing the planets in general, as opposed to studying the individual planets in great depth. Discuss how this approach compares to the way you have been taught about the planets in the past (for example, in grade school or high school). b) Make a list of advantages and any disadvantages of the comparative approach for planetary science. c) Make a list of a few other fields (such as other sciences or social sciences) in which you think a comparative approach is useful. Describe why in each case.

Investigate Further 37) Planetary Tour. Based on the brief planetary tour in this chapter, which planet besides Earth do you think is the most interesting, and why? Defend your opinion clearly in two or three paragraphs.

38) Patterns of Motion. In one or two paragraphs, explain why the existence of orderly patterns of motion in our solar system suggests that the Sun and the planets all formed at one time from one cloud of gas, rather than as individual objects at different times.

39) Solar System Trends. Answer the following based on the data in Table 7.1. a) Describe the relationship between distance from the Sun and surface temperature. Explain the reason behind the general trend, as well as any notable exceptions to the trend. b) Describe in general how the columns for density, composition, and distance from the Sun support the classification of planets into the terrestrial and jovian categories, with Pluto fitting neither category. c) Describe the trend in orbital periods, and explain it in terms of Kepler's third law.

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40) Comparing Planetary Conditions. Use both Table 7.1 and Appendix E to answer each of the following. a) Which column of data would you use to find out which planet has the shortest days? Are there any notable differences in the length of a day for the different types of planets? Explain. b) Which column of data would you use to find out which planets should have seasons? Explain. c) Which column tells you how much a planet's orbit deviates from a perfect circle? For each planet, use that column to decide whether you would expect its average surface temperature to vary over the course of its orbit, and why.

41) Escape Velocity. Use Appendix E to explore how escape velocity is related to mass and radius. Is the trend what you expect based on what you learned about escape velocity in Chapter 4? Explain.

42) Current Spacecraft Mission. Visit the website for a current or upcoming robotic mission of your choice. Write a one- to two-page summary of the mission's basic design, goals, and current status.

43) Mars Missions. Visit the website for NASA's Mars Exploration Program. Write a one- to two-page summary of the plans for future exploration of Mars.

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

44) Size Comparisons.How many Earths could fit inside Jupiter (assuming you could fill up all the volume)? How many Jupiters could fit inside the Sun? The equation for the volume of a sphere isV = πr3.

45) Asteroid Orbit. Ceres, the largest asteroid, has an orbital semimajor axis of 2.77 AU. Use Kepler's third law to find its orbital period. Compare your answer with the value in Table 7.1, and name the planets that orbit just inside and outside Ceres's orbit.

46) Density Classification. Calculate the density of a hypothetical planet in our solar system with a mass of 5.97 × 1025 kilograms and a radius of 12,800 kilometers; give your answer in units of grams per cubic centimeter. Based just on its density, would we consider it the largest terrestrial planet or the smallest jovian planet? Explain.

47) Comparative Weight. Suppose you weigh 100 pounds. Calculate how much you would weigh on each of the other planets in our solar system. Assume you can stand either on the surface or in an airplane in the planet's atmosphere. (Hint: Recall from Chapter 4 that weight is mass times the acceleration of gravity; the "surface gravity"column in Appendix E tells you how the acceleration of gravity on other planets compares to that on Earth.)

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48) New Horizons Speed. On its trajectory to Pluto, the New Horizons spacecraft traveled a total distance of about 34 AU over a period of about 9-1/2 years. a) About how fast was it traveling on average? Give your answer in AU per year and kilometers per hour. b) If it continued at this speed, about how long would New Horizons take to reach the nearest stars, if it were heading in the correct direction?

49) Planetary Parallax. Suppose observers at Earth's North Pole and South Pole use a transit of the Sun by Venus to discover that the angular size of Earth as viewed from Venus would be 62.8 arcseconds. Earth's radius is 6378 kilometers. Estimate the distance between Venus and Earth in kilometers and AU. Compare your answer with information from the chapter.

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The Cosmic Perspective, 9e (Bennett et al.) Chapter 8 Formation of the Solar System Section 8.1 1) Which of the following is a feature of our solar system that should be predicted by a successful theory of solar system formation? A) the age of our solar system B) the fact that all the planets in our solar system orbit the Sun in the same direction C) the fact that there are exactly four terrestrial planets and exactly four jovian planets D) the fact that Earth has a 23-1/2° axis tilt E) the fact that Jupiter has the most known moons in the solar system Answer: B 2) The "close encounter hypothesis" suggested that the planets formed after a near-collision between our Sun and another star. If this hypothesis were correct, which of the following would be true? A) Planetary systems would be very rare. B) Planetary systems would be very common. C) Most planetary systems would have their jovian planets closer to their stars and their terrestrial planets farther from their stars. D) Most planetary systems would have the same number of planets as our own. E) All planetary systems would be at least 4 billion years old. Answer: A 3) Where did most elements heavier than hydrogen and helium come from? A) They were produced in the Big Bang. B) They evolved from hydrogen and helium shortly after the Big Bang. C) They were produced by stars. D) They were produced inside interstellar gas clouds. E) all of the above Answer: C 4) Have astronomers ever seen a gas cloud that looks like it contains planetary systems that are in the process of forming? A) Yes, there are many such clouds, including the Orion Nebula. B) Yes, but only the original cloud that formed our own solar system. C) Yes, but only in distant galaxies, not in our own Milky Way. D) No, there is no evidence that any interstellar clouds are currently giving birth to stars. Answer: A

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5) Which of the following is NOT a pattern of motion in our Solar System?

A) Most planets rotate in the same direction they orbit.

B) Most planetary orbits lie in the same plane.

C) Most planets orbit in the same direction.

D) Almost all large moons orbit their planet in the same direction as the planet's rotation.

E) The planets orbit the Sun in a direction opposite that of the Sun's rotation.

Answer: E Section 8.2 1) Which of the following is most important in causing a cloud of gas to collapse to form a star and planets?

A) Gravity pulls all the gas inward.

B) Pressure from other gas clouds pushes the gas inward.

C) Opposite charges in the gas attract.

D) Some gas is sent outward, causing the rest to move inward to conserve momentum.

E) Pressure from light from nearby stars pushes the gas inward.

Answer: A 2) Why did the solar nebula heat up as it collapsed?

A) Nuclear fusion occurring in the core of the forming Sun produced energy that heated the nebula.

B) As it shrank in size, gravitational potential energy was converted to thermal energy.

C) It was heated by radiation from nearby stars.

D) The shock wave from a nearby supernova heated the gas.

E) Collisions among planetesimals generated friction and heat.

Answer: B 3) If an interstellar gas cloud shrinks in size, what does the law of conservation of energy predict it will do?

A) heat up B) spin slower C) cool off D) continue shrinking E) spin faster Answer: A 4) According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?

A) the two laws of thermal radiation B) the law of conservation of angular momentum C) the law of universal gravitation D) the law of conservation of energy Answer: D

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5) If an interstellar gas cloud shrinks in size, what does the law of conservation of angular momentum predict it will do?

A) heat up B) spin slower C) cool off D) continue shrinking E) spin faster Answer: E 6) According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?

A) Einstein's law that E = mc2 B) the law of conservation of angular momentum C) Kepler's first law of planetary motion D) the law of universal gravitation Answer: B 7) Why did the solar nebula flatten into a disk?

A) The interstellar cloud from which the solar nebula formed was originally somewhat flat.

B) The force of gravity from the Sun pulled the material downward into a flat disk.

C) As the nebula cooled, the gas and dust settled onto a disk.

D) It flattened as a consequence of collisions between particles in the spinning nebula, changing random motions into more orderly ones.

E) The force of gravity from the planets pulled the material downward into a flat disk.

Answer: D 8) Which of the following statements best explains why all the planets orbit the Sun in the same direction and in nearly the same plane?

A) The planets formed from a disk of rotating gas, and their orbits therefore orbit as this gas did.

B) The Sun's rotation spun out the planets as it formed.

C) No one knows: planets form randomly, so it's a puzzle why they orbit with such a pattern.

D) The Sun's gravity is strongest as its equator, so it pulled all the planets into this orbital alignment.

Answer: A 9) What is our best hypothesis for why all the planets in our solar system orbit in the same direction as the Sun rotates?

A) The planets and Sun formed from the same, single, rotating gas cloud.

B) It's a complete coincidence.

C) The planets were pulled out of the Sun by a major interaction with another star.

D) Almost everything in our Galaxy rotates in the same direction.

E) The Sun did not initially rotate, but the planets gravity caused it to start rotating in the direction in which the planets orbit.

Answer: A

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10) Which of the following observations of an extrasolar planet system would be inconsistent with what we expect from the nebular theory of solar system formation?

A) a system which has two terrestrial planets close in and two jovian planets farther out B) a system in which some planets have small moons orbiting in a direction opposite to the planet's rotation C) a system in which some planets rotate in a direction opposite to their orbits D) a system in which all the planets orbit in completely different planes Answer: D 11) According to our theory of solar system formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane?

A) The original solar nebula happened to be disk shaped by chance.

B) Any planets that once orbited in the opposite direction or a different plane were ejected from the solar system.

C) The laws of conservation of energy and conservation of angular momentum ensure that any rotating, collapsing cloud will end up as a spinning disk.

D) The Sun formed first, and as it grew in size it spread into a disk, rather like the way a ball of dough can be flattened into a pizza by spinning it.

E) It is a coincidence, as we would expect that most other solar systems would not have all their planets orbiting in such a pattern.

Answer: C 12) Which of the following ingredients was least abundant in the solar nebula?

A) metal B) rock C) hydrogen compounds D) hydrogen E) helium Answer: B 13) Which of the following lists the ingredients of the solar nebula from highest to lowest percentage of mass of the nebula?

A) hydrogen and helium gas, hydrogen compounds, rocks, metals B) hydrogen compounds, hydrogen and helium gas, rocks, metals C) hydrogen and helium gas, hydrogen compounds, metals, rocks D) hydrogen compounds, hydrogen and helium gas, metals, rocks E) hydrogen compounds, rocks, metals, hydrogen and helium gas Answer: A 14) About what percentage of the mass of the solar nebula consisted of elements other than hydrogen and helium?

A) 0 percent B) 0.1 percent C) 2 percent D) 20 percent E) 80 percent Answer: C

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15) About what percentage of the mass of the solar nebula consisted of hydrogen and helium gas?

A) 0.5 percent B) 5 percent C) 50 percent D) 98 percent E) 100 percent Answer: D 16) The very first generation of star systems in the universe must have been born from gas that consisted entirely of hydrogen and helium (and no other elements). Which of the following statements is most likely to have been true about these first-generation star systems?

A) They had terrestrial planets but no jovian planets.

B) They did not have any planets or asteroids or comets.

C) They had asteroids and comets but no large planets.

D) They did not have and disks of gas around them as they formed.

Answer: B 17) What happened during the accretion phase of the early solar system?

A) Atoms of hydrogen and helium gas bonded together and solidified.

B) Particles grew by colliding and sticking together.

C) The solar nebula differentiated into metals inside of the frost line and ices beyond.

D) Large planetesimals captured atmospheres from the solar nebula.

E) Earth gained its oceans from icy planetesimal capture.

Answer: B 18) Beyond the frost line of the solar system, temperatures were low enough for A) metals to condense into solid form.

B) rocks to condense into solid form.

C) hydrogen compounds to condense into solid ices.

D) asteroids to form.

E) hydrogen and helium to condense into ice.

Answer: C 19) The frost line of the solar system was located approximately between A) the Sun and the present-day orbit of Mercury.

B) the present-day orbits of Mercury and Venus.

C) the present-day orbits of Mars and Jupiter.

D) the present-day orbits of Venus and Earth.

E) the present-day orbits of Uranus and Neptune.

Answer: C

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20) What do we mean by the frost line when we discuss the formation of planets in the solar nebula? A) It is another way of stating the temperature at which water freezes into ice. B) It is a particular distance from the Sun, beyond which the temperature was low enough for ices to condense. C) It marks the special distance from the Sun at which hydrogen compounds become abundant; closer to the Sun, there are no hydrogen compounds. D) It is the altitude in a planet's atmosphere at which snow can form. Answer: B 21) Why are the inner planets made of denser materials than the outer planets? A) The Sun's gravity pulled denser materials toward the inner part of the solar nebula, while lighter gases escaped more easily. B) Denser materials were heavier and sank to the center of the nebula. C) In the inner part of the nebula only metals and rocks were able to condense because of the high temperatures, whereas hydrogen compounds, although more abundant, were only able to condense in the cooler outer regions. D) When the solar nebula formed a disk, materials naturally segregated into bands, and in our particular solar system, the denser materials settled nearer the Sun, while lighter materials are found in the outer part. E) In the beginning, when the protoplanetary disk was spinning faster, centrifugal forces flung the lighter materials toward the outer parts of the solar nebula.

Answer: C 22) Why did terrestrial planets form in the inner solar system and jovian planets in the outer solar system? A) As the solar nebula shrank, it settled into a spinning disk and separated into individual planets. B) Denser, heavier materials, such as rocks and metals, settled to the center of the nebula, and therefore, planets that formed there were more likely to be made primarily from rock and metal. C) In the inner part of the nebula, only metals and rocks were able to condense because of the high temperatures, whereas hydrogen compounds, although more abundant, were only able to condense in the cooler outer regions. Answer: C 23) According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system? A) The solid material that accreted in the outer solar system included ices, while the solid material of the inner solar system consisted only less abundant metal and rock. B) There was more time for accretion in the outer solar system before the solar wind cleared the nebula away. C) The gas in the outer solar system contained a larger proportion of rock, metal, and hydrogen compound than the gas in the inner solar system. D) Gravity was stronger in the outer solar system, allowing more solid material to collect. Answer: A

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24) Which of the following is the origin of most of the large moons around the jovian planets? A) They are captured asteroids. B) They are captured comets. C) They are captured planets. D) They were formed by condensation and accretion in a disk of gas around the planet. E) They were formed by giant impacts. Answer: D 25) The nebular theory predicts that the young Sun should have been rotating quite rapidly, but the Sun rotates slowly today. Can this fact be explained by the nebular theory? A) Yes; the young Sun's solar wind would have carried away angular momentum, slowing the Sun's rotation.

B) Yes, objects always slow their rotations over time. C) No, it is a complete mystery as to why the Sun would rotate slowly today. Answer: A 26) According to our theory of solar system formation, why does the Sun rotate slowly today? A) The Sun once rotated much faster, but it transferred angular momentum to charged particles caught in its magnetic field and then blew the particles away with its strong solar wind. B) The Sun once rotated much faster, but it transferred angular momentum to the planets during the parts of their orbits where they come closest to the Sun. C) The Sun once rotated much faster, but it lost angular momentum due to internal friction. D) The Sun once rotated much faster, but it lost angular momentum because everything slows down with time. E) The Sun was born rotating slowly because the solar nebula had very little angular momentum. Answer: A 27) Hydrogen compounds in the solar nebula could condense into ice at temperatures of about 150 K. Suppose they instead could have condensed only at temperatures below 50 K? What would have been different in the solar nebula? A) The frost line would have been farther from the Sun. B) The frost line would have been closer to the Sun. C) Terrestrial planets would have formed outside the frost line. D) Jovian planets would have formed inside the frost line. Answer: A 28) Observations of young stars suggest that when the Sun was young, the solar wind A) was weaker than it is today. B) was stronger than it is today.

C) was about the same strength as it is today. D) was nonexistent. E) blew outward only along the Sun's poles. Answer: B

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29) According to the nebular theory, what are asteroids and comets?

A) leftover planetesimals that never accreted into planets B) chunks of rock or ice that condensed long after the planets had formed C) the shattered remains of collisions between moons D) the shattered remains of collisions between planets E) chunks of rock or ice that have been expelled from the planets by volcanoes Answer: A 30) Comets are made mostly of A) rock.

B) hydrogen gas.

C) rock and metal.

D) metal.

E) rock and ice.

Answer: E 31) The period we call the "heavy bombardment" was A) the first few hundred thousand years of the solar system's history.

B) the most recent hundred million years of the solar system's history.

C) the first few hundred million years of the solar system's history.

D) a period of a few hundred million years that began when the solar system was about 1 billion years old.

E) the time during which an asteroid hit the Earth and caused the extinction of the dinosaurs.

Answer: C 32) What happened during the heavy bombardment?

A) The planets of the solar system suffered many impacts.

B) The planets collided with one another.

C) Planetesimals collided with one another and stuck together to form planets.

D) A supernova disrupted a gas cloud, causing it to start collapsing to form the solar system.

E) A large meteor collided with Earth, killing the dinosaurs.

Answer: A 33) Which of the following is not evidence supporting the giant impact theory for the formation of the Moon?

A) Computer simulations show that the Moon could really have formed in this way.

B) The composition of the Moon is similar to that of Earth's outer layers.

C) The Moon is depleted of easily vaporized materials, as we would expect from the heat of an impact.

D) Scientists have found several meteorites that appear to be the remains of the object that caused the giant impact.

Answer: D

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34) What is the giant impact hypothesis for the origin of the Moon?

A) The Moon originally was about the same size as Earth, but a giant impact blasted most of it away so that it ended up much smaller than Earth.

B) The Moon formed just like Earth, from accretion in the solar nebula.

C) The Moon formed from material blasted out of Earth's mantle and crust by the impact of a Mars-size object.

D) The Moon formed when two gigantic asteroids collided with one another.

Answer: C 35) Based on our current theory of Earth's formation, the water we drink likely comes from A) ice that condensed in the solar nebula in the region where Earth formed.

B) chemical reactions that occurred in Earth's crust after Earth formed.

C) chemical reactions that occurred in Earth's core after Earth formed.

D) material left behind during the giant impact that formed the Moon.

E) water-bearing planetesimals that formed beyond the frost line and then impacted Earth.

Answer: E 36) We know that Earth has water. However, according to our theory of solar system formation, the inner solar system was too hot for hydrogen compounds like water to condense. What do we conclude?

A) Water arrived on Earth at a time when it rained throughout the inner solar system.

B) Earth's water likely was brought here by asteroids or comets that formed beyond the frost line.

C) Our theory of solar system formation will need modification because it is unable to account for the existence of water on Earth.

D) Earth's water probably originated through chemical reactions among the rock and metal of Earth's interior.

Answer: B 37) According to our theory of solar system formation, why do we find some exceptions to the general rules and patterns of the planets?

A) Our theory is not quite correct because it cannot explain these exceptions.

B) Most of the exceptions are the result of giant impacts or close gravitational encounters.

C) The exceptions probably represent objects that formed recently, rather than early in the history of the solar system.

D) The exceptions probably represent objects that were captured by our solar system from interstellar space.

E) The exceptions are probably the result of the Sun passing very close to another star billions of years ago.

Answer: B 38) What is the best explanation for how the solar nebula was cleared of debris?

A) The strong solar wind of the young Sun blew away material not accreted by the planets.

B) The planets accreted all the material around them, leaving no debris.

C) All of the debris eventually fell into the Sun. D) The debris collapsed to form moons.

E) The debris all disappeared through radioactive decay.

Answer: A

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39) Suppose the Sun had been born with less mass, making it a smaller, cooler star. Which of the following consequences would we expect according to the nebular theory? A) The frost line would have been farther from the Sun, so jovian planets could form only at greater distances than in our solar system. B) The frost line would have been closer to the Sun, so jovian planets could form at nearer distances than in our solar system. C) The planets would have formed just as they did for our actual Sun, but the weaker gravity of a smaller Sun would have allowed the planets to escape into interstellar space. D) There would have been no solar nebula in which material could condense to form planets.

Answer: B 40) Suppose the Sun had been born with more mass, making it larger and hotter. Which of the following consequences would we expect according to the nebular theory? A) There would be no comets. B) Asteroids would have formed closer to the Sun. C) Jovian planets would have formed farther from the Sun. D) There would have been no solar nebula in which material could condense to form planets. Answer: C Section 8.3 1) The age of our solar system is approximately A) 10,000 years. B) 3.8 million years. C) 4.5 million years. D) 4.5 billion years. E) 14 billion years. Answer: D 2) How do we know how old the solar system is? A) by measuring the rate of the expansion of the universe B) We estimate the age based on how fast the terrestrial planets cooled and solidified. C) by radiometric dating of meteorites D) by measuring how much mass the Sun has lost through fusion over time Answer: C 3) The age of the solar system can be established by radiometric dating of A) the oldest Earth rocks. B) the oldest rocks on the Moon. C) the oldest meteorites. D) the atmosphere of Mars. E) the oldest rocks on Jupiter's moon Io. Answer: C

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4) Uranium-238 decays into lead-206 with a half-life of 4.5 billion years. Suppose you found a rock in which only 1/4 of the original uranium-238 remained (the other ¾ having become lead-206). How old would the rock be? A) 9 billion years B) 4.5 billion years C) 2.25 billion years D) 13.5 billion years Answer: A 5) Potassium-40 decays to argon-40 has a half-life of 1.25 billion years. Suppose you find a rock that has only 1/8 of its original potassium-40 still remaining. How old is the rock? A) 3.75 billion years B) 5.25 billion years C) 2.5 billion years D) 1.25 billion years E) 4.5 billion years Answer: A 6) Why do Earth rocks have much younger ages than most meteorites? A) Earth formed billions of years after most meteorites formed. B) The rocks solidified long after the formation of the solar nebula. C) The atoms that make up Earth rocks are generally younger than the atoms that make up meteorites. D) Most meteorites come from other planetary systems that formed before our solar system. Answer: B 7) What is the half-life of a radioactive isotope?

A) the amount of time for half of a sample of the isotope to decay into a different element or isotope B) the amount of time for half of a sample of the element to decay into nothing C) half of the total time that the isotope has been in existence D) half of the amount of that element in the universe E) half of the age of the solar system Answer: A 8) If a radioactive isotope with a half-life of 5 hours is injected into your bloodstream for medical imaging purposes, how many hours do you have to wait before the amount of this isotope in your body is 1/16 its original amount? A) 15 B) 10 C) 25 D) 5 E) 20 Answer: E

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General Chapter Questions 1) What is the most likely reason that there are no other jovian planets in our solar system beyond Neptune?

A) Any planets forming beyond Neptune would have drifted out of the solar system due to the weakness of the Sun's gravity at this distance.

B) There was no material to create planetesimals beyond the orbit of Neptune.

C) By the time planetesimals grew to a large enough mass to capture hydrogen and helium gas from the solar nebula, the gas had been cleared by the solar wind.

D) Any planet forming beyond Neptune's orbit would have been scattered outside of the solar system by gravitational encounters.

E) Formation of another planet was prevented by orbital resonances with Neptune.

Answer: C 2) Consider the five facts listed below. The nebular theory of the formation of the solar system successfully accounts for four of these facts, while one can be considered to be just a coincidence. Which fact is a coincidence?

A) Our solar system has an equal number of terrestrial and jovian planets.

B) The planets all orbit around the Sun in nearly circular orbits in nearly the same plane.

C) The planets divide into two major types, terrestrial and jovian.

D) The solar system has many small bodies, and these are concentrated in the regions known as the asteroid belt, Kuiper belt, and the Oort cloud.

E) There are many impact craters on the Moon.

Answer: A 3) How do astronomers explain the fact that some planetary systems (besides our own) have jovian-size planets that orbit very close to their stars?

A) The planets likely formed farther out, then migrated inward.

B) The solar nebula theory must be wrong because jovian planets cannot be that close.

C) Jovian planets must be objects from outside the system that were captured.

D) Jovian planets must be created by collisions of terrestrial planets.

E) The observations must have been misinterpreted.

Answer: A 4) Which of the following measurements of other solar systems would require us to change our current solar system formation theory?

A) The age of another solar system is significantly older than our solar system.

B) The planets in other solar systems mostly orbit their central stars in the same plane and same direction as the other planets in that solar system.

C) Some stars have no planets.

D) Some stars have many planets.

E) Many other stars have planets orbiting in many different directions and at many different angles.

Answer: E

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Short Answer Questions 1) List at least two of the notable exceptions to the general patterns of the solar system.

Answer: Several possibilities: The rotational axes of Uranus and Pluto are substantially tilted.

Venus rotates backward relative to its orbit. Earth has a surprisingly large Moon. Pluto has a moon that is almost as large as itself. Triton orbits "backward" relative to Neptune's rotation.

Many small moons of the jovian planets orbit in the opposite direction of Jupiter's rotation.

2) Suppose the entire solar nebula had cooled to a very low temperature before the solar wind cleared it away. Do you think Earth would be the same? Why or why not?

Answer: Ices would have condensed in the inner solar system, significantly increasing the size and mass (or possibly number) of terrestrial planets. Water and other hydrogen compounds would be much more abundant.

3) Suppose the planet Jupiter had never formed. How do you think the distribution of asteroids and comets in our solar system would be different? Explain.

Answer: There would likely be no asteroid belt because without Jupiter's gravitational effects, the material in that region could have accreted into a single planet. There also would likely be few comets in the Oort cloud because many of those comets were presumably flung into Oort cloud orbits by gravitational encounters with Jupiter.

4) A scientific theory must produce testable predictions that are then evaluated when data are available. Describe at least two predictions of the nebular theory that can be tested through observations of other planetary systems.

Answer: Possible answers include: Planets should be common around other stars; most or all planets should orbit in the same direction and nearly the same plane around their star; rocky worlds should be closer to their stars and icy worlds farther away; all planetary systems should have "leftovers" like asteroids and comets.

Reading Quiz Questions 1) In essence, the nebular theory holds that A) our solar system formed from the collapse of an interstellar cloud of gas and dust.

B) nebulae are clouds of gas and dust in space.

C) the planets each formed from the collapse of its own separate nebula.

D) the planets formed as a result of a near-collision between our Sun and another star.

Answer: A 2) According to modern science, what was the approximate chemical composition of the solar nebula?

A) 98% hydrogen and helium, 2% everything else B) 50% hydrogen and helium, 50% everything else C) 98% hydrogen, 2% helium D) roughly equal proportions of hydrogen, helium, water, and methane Answer: A

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3) The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did the elements heavier than hydrogen and helium come from? A) They were produced by stars that lived and died before our solar system was born. B) They were produced by gravity in the solar nebula as it collapsed. C) They have been present in the universe since its birth. D) They were made by chemical reactions in interstellar gas. Answer: A 4) According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size? A) It got hotter, its rate of rotation increased, and it flattened into a disk. B) Its mass, temperature, and density all increased. C) It gained energy, it gained angular momentum, and it flattened into a disk. D) Its gas clumped up to form the terrestrial planets, nuclear fusion produced heavy elements to make the jovian planets, and central temperatures rose to more than a trillion Kelvin. Answer: A 5) Which of the following types of material can condense into what we call ice at low temperatures? A) hydrogen compounds B) hydrogen and helium C) rock D) metal Answer: A 6) According to our present theory of solar system formation, which of the following lists the major ingredients of the solar nebula in order from the most abundant to the least abundant? A) hydrogen and helium gas; hydrogen compounds; rock; metal B) hydrogen compounds; hydrogen and helium gas; metal; rock C) hydrogen and helium gas; rock; metal; and hydrogen compounds D) hydrogen; water; methane; and helium Answer: A 7) In the context of the formation of planets in the solar nebula, the frost line marks the distance from the Sun beyond which A) the temperature was low enough for hydrogen compounds to condense into ices. B) the temperature was low enough for solid rock to condense from the gas. C) hydrogen compounds were particularly abundant. D) planets could be cold enough to have snow. Answer: A

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8) What do we mean by accretion in the context of planet formation?

A) the growth of planetesimals from smaller solid particles that collided and stuck together B) the formation of moons around planets C) the solidification of ices, rocks, and metal from the gas of the solar nebula D) the growth of the Sun as the density of gas increased in the center of the solar nebula Answer: A 9) According to the nebular theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system?

A) because only metal and rock could condense in the inner solar system, whereas ice also condensed in the outer solar system B) because the Sun's gravity was stronger in the outer solar system, allowing more solid material to collect C) because gas in the outer solar system contained a larger proportion of rock, metal, and hydrogen compounds than the gas in the inner solar system D) because only the outer planets captured hydrogen and helium gas from the solar nebula Answer: A 10) According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?

A) As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks.

B) Because of their strong gravity, the jovian planets were able to capture numerous asteroids that happened to be passing nearby, and these became the major moons of the jovian planets.

C) The large moons of the jovian planets originally formed in the inner solar system and these moons then migrated out to join up with the jovian planets.

D) The many moons of the jovian planets remains one of the unexplained mysteries of the formation of our solar system.

Answer: A 11) According to our theory of solar system formation, what are asteroids and comets?

A) leftover planetesimals that never accreted into planets B) the shattered remains of collisions between planets C) chunks of rock or ice that condensed after the planets and moons finished forming D) chunks of rock or ice that were expelled from planets by volcanoes Answer: A 12) What do we mean by the period of heavy bombardment in the context of the history of our solar system?

A) the first few hundred million years after the planets formed, which is when most impact craters were formed B) the time before planetesimals finished accreting into planets, during which time many growing planetesimals must have shattered in collisions C) the time during which heavy elements condensed into rock and metal in the solar nebula D) the period about 65 million years ago when an impact is thought to have led to the extinction of the dinosaurs Answer: A

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13) What is the giant impact hypothesis for the origin of the Moon?

A) The Moon formed from material blasted out of the Earth's mantle and crust by the impact of a Mars-size object.

B) The Moon formed when two gigantic asteroids collided with one another.

C) The Moon originally was about the same size as Earth, but a giant impact blasted most of it away so that it ended up much smaller than Earth.

D) The Moon formed just like the Earth, from accretion in the solar nebula.

Answer: A 14) Consider a radioactive substance with a half-life of 10 years. If you start with 1 kilogram of this substance, after 20 years, ________ of the radioactive substance will remain.

A) 0.25 kilogram B) none C) 0.75 kilogram D) 0.5 kilogram Answer: A 15) According to modern scientific dating techniques, approximately how long ago did Earth and the other planets of our solar system form?

A) 4.5 billion years B) 10,000 years C) 4.5 million years D) 14 billion years Answer: A Concept Quiz Questions 1) Which of the following best explains why we can rule out the idea that planets are usually formed by near collisions between stars?

A) Stellar near collisions are far too rare to explain all the planets now known to orbit nearby stars.

B) Studies of the trajectories of nearby stars relative to the Sun show that the Sun is not in danger of a near collision with any of them.

C) A near collision might have created planets, but it could not have created moons, asteroids, or comets.

D) A near collision should have left a trail of gas extending out behind the Sun, and we see no evidence of such a trail.

Answer: A

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2) According to modern science, which of the following best explains why the vast majority of the mass of our solar system consists of hydrogen and helium gas?

A) Hydrogen and helium are the most common elements throughout the universe.

B) Gravity only acted on hydrogen and helium.

C) All the elements besides hydrogen and helium escaped from the solar nebula before the Sun and planets formed.

D) All elements besides hydrogen and helium were swept out of the solar system by the solar wind.

Answer: A 3) According to the nebular theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?

A) the law of conservation of energy B) the law of conservation of angular momentum C) Newton's third law D) the two laws of thermal radiation Answer: A 4) According to the nebular theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?

A) the law of conservation of angular momentum B) the law of conservation of energy C) the law of universal gravitation D) Einstein's law E = mc2 Answer: A 5) According to the nebular theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?

A) As the nebula shrank and rotated faster, collisions between orbiting particles caused it to flatten into a disk.

B) The nebula was fairly flat to begin with, and retained this flat shape as it collapsed.

C) The force of gravity pulled material that was spherically distributed downward into a flat disk.

D) the law of conservation of energy Answer: A 6) What is the primary basis on which we divide the ingredients of the solar nebula into the four categories hydrogen/helium, hydrogen compounds, rock, and metal?

A) the temperatures at which various materials can condense from gaseous form to solid form B) the atomic mass numbers of various materials C) the locations of various materials in the solar nebula D) the amounts of energy required to ionize various materials Answer: A

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7) According to the nebular theory of solar system formation, what key difference in their early formation explains why the jovian planets ended up so different from the terrestrial planets?

A) The terrestrial planets formed inside the frost line of the solar nebula and the jovian planets formed beyond it.

B) The jovian planets formed in a region with a much higher density of hydrogen and helium gas.

C) The terrestrial planets accreted from rock and metal, while the jovian planets were formed by giant balls of pure hydrogen and helium gas.

D) The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.

Answer: A 8) Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support the nebular theory's scenario for the formation of the terrestrial planets?

A) The appearance and composition of these meteorites is just what we'd expect if metal and rock condensed and accreted as the nebular theory suggests.

B) The sizes of these meteorites are just what we'd expect if metal and rock condensed and accreted as the nebular theory suggests.

C) The overall composition of these meteorites is just what we believe the composition of the solar nebula to have been: mostly hydrogen and helium.

D) The appearance and composition of these meteorites matches what we observe in comets today, suggesting that they were once pieces of icy planetesimals.

Answer: A 9) According to present understanding, which of the following statements about the solar wind is not true?

A) It is even stronger today than it was when the Sun was young.

B) It helped in the transfer of angular momentum from the young Sun to particles that blew into interstellar space, which explains why the Sun rotates so slowly today.

C) It swept vast amounts of gas from the solar nebula into interstellar space.

D) It consists of charged particles blown off the surface of the Sun. Answer: A 10) According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?

A) The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.

B) The water was mixed in the other materials in the planetesimals that accreted at our distance from the Sun. C) The water was formed by chemical reactions among the minerals in the Earth's core.

D) Earth formed in the relatively narrow region of the solar nebula in which liquid water was plentiful.

Answer: A

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11) What is the primary reason that astronomers suspect that some jovian moons were captured into their current orbits? A) Some moons have orbits that are backward (compared to their planet's rotation) or highly inclined to their planet's equator. B) Some moons have a composition that differs from the composition of the planets. C) Astronomers have observed moons being captured. D) Some moons are surprisingly large in size. Answer: A 12) Which of the following is not a line of evidence supporting the hypothesis that our Moon formed as a result of a giant impact? A) The Pacific Ocean appears to be a large crater, probably the one made by the giant impact. B) Computer simulations show that the Moon could really have formed through a giant impact. C) The Moon's average density suggests it is made of rock much more like that of the Earth's outer layers than that of the Earth as a whole. D) The Moon has a much smaller proportion of easily vaporized materials than Earth. Answer: A 13) About 2% of our solar nebula consisted of elements besides hydrogen and helium. However, the first generation of star systems in the universe probably consisted only of hydrogen and helium. Which of the following statements is most likely to have been true about these first- generation star systems? A) There were no comets or asteroids in these first-generation star systems. B) Jovian planets in these first-generation star systems had clouds made of water and other hydrogen compounds. C) These first-generation star systems typically had several terrestrial planets in addition to jovian planets. D) Like the jovian planets in our solar system, the jovian planets in these first-generation systems were orbited by rings. Answer: A 14) Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40) present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solidified. How old is the rock? A) 3.75 billion years B) 1.25 billion years C) 2.5 billion years D) 5.0 billion years Answer: A 15) How do scientists determine how long ago Earth first formed? A) radiometric dating of meteorites B) radiometric dating of Moon rocks C) radiometric dating of the oldest Earth rocks D) Models of planetary formation tell us how long it took Earth to grow to its present size. Answer: A

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Visual Quiz Questions 1) What does this photo show?

A) an interstellar cloud that will ultimately give birth to thousands of star systems B) an interstellar cloud that probably looks almost identical to the way the solar nebula looked about 4.5 billion years ago C) stars viewed through the atmosphere of Venus D) a galaxy much like our Milky Way Galaxy Answer: A 2) What is the significance of this image?

A) It shows an actual disk of material orbiting another star, providing strong evidence the planets really do form in such disks.

B) It shows an artist's conception of what our solar system might have looked like when the planets were first forming.

C) It proves that jovian planets form farther from their stars than terrestrial planets.

D) The large gap visible in the image represents the frost line of a young planetary system, demonstrating that such a line really exists.

Answer: A

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3) This sequence of paintings shows how a large gas cloud can collapse to become a much smaller, spinning disk of gas. What law explains why cloud spins faster as it shrinks in size?

A) the law of conservation of energy B) the universal law of gravitation C) the law of conservation of angular momentum D) Kepler's third law E) Newton's second law of motion Answer: C 4) This sequence of paintings shows how a large gas cloud can collapse to become a much smaller, spinning disk of gas. What law explains why the center of the cloud becomes so much hotter as the cloud shrinks in size?

A) the law of conservation of energy B) the universal law of gravitation C) the law of conservation of angular momentum D) Newton's second law of motion Answer: A

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5) This diagram represents the solar nebula early in its history and shows the locationfrost of the line. Suppose you discover an object that is made of metal, rock, and ice. In which of the four regions shown in the diagram did it form?

A) Region 1 B) Region 2 C) Region 3 D) Region 4 Answer: D 6) This photo shows a slice of a meteorite. What is its significance?

A) The shiny metal flakes embedded in rock are just what we expect if condensation really occurred as the nebular theory predicts.

B) It shows that accretion really did make objects many kilometers in size during the early stages of the formation of our solar system.

C) The surprisingly flat face of the meteorite indicates that the solar nebula must have been hot in the region in which this meteorite formed.

D) The structure and composition of the meteorite show that material that condensed beyond the frost line really did differ from material that condensed within the frost line.

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7) What is being shown in the zoom-out box of this painting?

A) the formation of a jovian planet B) the solar nebula C) the formation of a terrestrial planet D) the formation of Saturn's rings Answer: A 8) This painting shows an object colliding with Earth. What is thought to have happened as a result of this collision?

A) It blasted away debris that then accreted in Earth orbit to form the Moon.

B) It led to the extinction of the dinosaurs.

C) The impact released the heat that allowed Earth to undergo differentiation.

D) The impact changed Earth's orbit from one on which life would have been unlikely to our current orbit in which life flourishes.

Answer: A

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9) What can you conclude from studying this graph?

A) Potassium-40 has a half-life of 1.25 billion years.

B) Argon-40 has a half-life of 1.25 billion years.

C) Both potassium-40 and argon-40 have half-lives of 1.25 billion years.

D) It takes 5 billion years to turn potassium-40 into argon-40.

Answer: A 10) You find a rock containing radioactive potassium-40 and its decay product argon-40. You assume that all the argon-40 was made from radioactive decay of potassium-40. The rock now has twice as much argon-40 as potassium-40; that is, 2/3 of the original potassium-40 has decayed into argon-40, whereas 1/3 remains in the rock. Based on this graph, about how old is the rock?

A) 1 billion years B) 1.25 billion years C) 2 billion years D) 2.5 billion years Answer: C

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

The graph above, similar to Figure 8.14, shows the radioactive decay of uranium-235 to lead-207. (Uranium-235 also decays to lead-206, but we'll ignore that reaction for the sake of clarity in this example.)

1) Compare the graph above to Figure 8.14, which shows the decay of potassium-40. Which element is more radioactive (undergoes radioactive decay more quickly)?

A) uranium-235 B) potassium-40 C) Both are equally radioactive.

Answer: A 2) What fraction of the original uranium-235 should be left after 3.5 billion years?

A) 1/2 B) 1/4 C) 1/8 D) 1/32 E) 1/64 Answer: D 25 Copyright © 2020 Pearson Education, Inc.

3) You find a mysterious rock on the ground and determine that 60% of its uranium-235 has been converted into lead-207. What is the most likely origin of the rock, based on its radiometric age?

A) It's older than our solar system, so it must have come from another solar system.

B) It's a meteorite dating back to the formation of the solar system.

C) It's a volcanic rock nearly a billion years old.

D) It was just formed this year during the eruption of a nearby volcano.

Answer: C Chapter Review Questions 1) Briefly describe the four major features of our solar system that a formation theory must explain.

2) What is the nebular theory, and why is it widely accepted by scientists today?

3) What do we mean by the solar nebula? What was it made of, and where did it come from?

4) Describe the three key processes that led the solar nebula to take the form of a spinning disk.

What observational evidence supports this scenario?

5) List the approximate condensation temperature and abundance for each of the four categories of materials in the solar nebula. Which ingredients are present in terrestrial planets? In jovian planets? In comets and asteroids?

6) What was the frost line? Which ingredients condensed inside and outside the frost line? What role did it play in the formation of two distinct types of planets?

7) Briefly describe the process by which terrestrial planets are thought to have formed.

8) How was the formation of jovian planets similar to that of the terrestrial planets? How was it different? Why did the jovian planets end up with so many moons?

9) What is the solar wind, and what roles did it play in the early solar system?

10) How did planet formation lead to the existence of asteroids and comets?

11) What was the heavy bombardment, and when did it occur?

12) What is the leading hypothesis for the Moon's formation, and what evidence supports this hypothesis?

13) Describe the technique of radiometric dating. What is a half-life?

14) How old is the solar system, and how do we know?

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Surprising Discoveries?

Suppose we found a solar system with the property described. (These are not real discoveries.) In light of what you've learned about the formation of our own solar system, decide whether the discovery should be considered reasonable or surprising. Explain your reasoning.

15) A solar system has five terrestrial planets in its inner solar system and three jovian planets in its outer solar system. 16) A solar system has four large jovian planets in its inner solar system and seven small terrestrial planets in its outer solar system. 17) A solar system has ten planets that all orbit the star in approximately the same plane. However, five planets orbit in one direction (e.g., counterclockwise), while the other five orbit in the opposite direction (e.g., clockwise). 18) A solar system has 12 planets that all orbit the star in the same direction and in nearly the same plane. The 15 largest moons in this solar system orbit their planets in nearly the same direction and plane as well. However, several smaller moons have highly inclined orbits around their planets. 19) A solar system has six terrestrial planets and four jovian planets. Each of the six terrestrial planets has at least five moons, while the jovian planets have no moons at all. 20) A solar system has four Earth-size terrestrial planets. Each of the four planets has a single moon that is nearly identical in size to Earth's Moon. 21) A solar system has many rocky asteroids and many icy comets. However, most of the comets orbit in the inner solar system, while the asteroids orbit in far-flung regions much like the Kuiper belt and Oort cloud of our solar system. 22) A solar system has several planets similar in composition to the jovian planets of our solar system but similar in mass to the terrestrial planets of our solar system. 23) A solar system has several terrestrial planets and several larger planets made mostly of ice.

(Hint: What would happen if the solar wind started earlier or later than in our solar system?) 24) Radiometric dating of the oldest meteorites from another solar system shows that they are a billion years younger than rocks from the terrestrial planets of the same system.

Quick Quiz 25) How many of the planets orbit the Sun in the same direction as Earth does?

A) a few B) most C) all Answer: No Correct Answer Was Provided.

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26) The nebular theory holds that A) our solar system formed from the collapse of an interstellar cloud of gas and dust.

B) each planet formed from the collapse of its own separate nebula.

C) the planets formed as a result of a near-collision between our Sun and another star.

Answer: No Correct Answer Was Provided.

27) The solar nebula was 98% A) rock and metal.

B) hydrogen compounds.

C) hydrogen and helium.

Answer: No Correct Answer Was Provided.

28) Which of the following did not occur during the collapse of the solar nebula?

A) spinning faster B) heating up C) concentrating denser materials nearer the Sun Answer: No Correct Answer Was Provided.

29) What is Jupiter's main ingredient?

A) rock and metal B) hydrogen compounds C) hydrogen and helium Answer: No Correct Answer Was Provided.

30) Which of the following lists the major steps of solar system formation in the correct order?

A) collapse, accretion, condensation B) collapse, condensation, accretion C) accretion, condensation, collapse Answer: No Correct Answer Was Provided.

31) Which of the following is not true of the young Sun? A) It rotated much faster than it does today.

B) It was much brighter and hotter than it is today.

C) It had a much stronger solar wind than it does today.

Answer: No Correct Answer Was Provided.

32) Leftover ice-rich planetesimals are called A) comets.

B) asteroids.

C) meteorites.

Answer: No Correct Answer Was Provided.

33) The leading hypothesis for the origin of the Moon is that it A) formed along with Earth.

B) formed from material ejected from Earth in a giant impact.

C) split out of a rapidly rotating Earth.

Answer: No Correct Answer Was Provided.

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34) About how old is the solar system?

A) 4.5 million years B) 4.5 billion years C) 4.5 trillion years Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

35) Group Discussion: Solar Origin Stories.

Ancient cultures understood the immense importance of the Sun and told many stories about its origins. This chapter has told a different origin story, based on the nebular theory, which scientists consider to be supported by a wide body of evidence. a) Working independently, learn about an origin story for the Sun from a culture different from your own, taking the time necessary to understand the value and purpose of that story for the culture that told it. b) Gather in small groups and take turns sharing the origin stories you learned about. c) Make a list of notable similarities and differences among the origin stories your group learned about, then discuss any commonalities you see in the roles the stories played in their cultures. d) Discuss the similarities and differences between the ancient origin stories and the nebular theory. What do you think are the value and purpose of the nebular theory to our own culture? e) Discuss the potential value of the ancient origin stories to our own culture. What do we learn by seeking them out and retelling them?

The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

36) Explaining the Past.Test the nebular theory against each of the three hallmarks of science discussed in Chapter 3. Be as detailed as possible in explaining whether the theory does or does not satisfy these hallmarks. Use your findings to discuss whether it is really possible for science to inform us about how our solar system formed. Defend your opinion.

37) Theory and Observation. Discuss the interplay between theory and observation that has led to our modern theory of solar system formation. What role does technology play in allowing us to test this theory?

38) Unanswered Questions. As discussed in this chapter, the nebular theory explains many but not all questions about the origin of our solar system. Choose one important but unanswered question about the origin of our solar system and write two or three paragraphs in which you discuss how we might answer this question in the future. Be as specific as possible, focusing on the type of evidence necessary to answer the question and how the evidence could be gathered.

What are the benefits of finding answers to this question?

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39) Group Activity: A Cold Solar Nebula. The excess gas of the solar nebula is presumed to have been cleared away (by the solar wind) at a time when the frost line was located between the orbits of Mars and Jupiter, but study of planets around other stars suggests that gas may be cleared out earlier or later in other solar systems. In this activity, you'll consider how our solar system might have turned out differently if the excess gas of the solar nebula had not been cleared away until the entire disk of gas had cooled to 50 K. Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39. a) Make a list of ingredients that will condense at 50 K. b) Make a list of ways in which the terrestrial planets might have turned out differently under this alternative formation scenario. c) Repeat part b for the jovian planets. d) Discuss the likelihood that your predicted changes would match the actual characteristics of this alternative solar system. e) Come up with additional "what if" scenarios, discussing various ways in which planets might have turned out differently.

Investigate Further 40) An Early Solar Wind. Suppose the solar wind had cleared away the solar nebula before the seeds of the jovian planets could gravitationally draw in hydrogen and helium gas. How would the planets of the outer solar system be different? Would they still have many moons? Explain your answer in a few sentences.

41) Angular Momentum. Suppose our solar nebula had begun with much more angular momentum than it did. Do you think planets could still have formed? Why or why not? What if the solar nebula had started with zero angular momentum? Explain your answers in one or two paragraphs.

42) Two Kinds of Planets. The jovian planets differ from the terrestrial planets in a variety of ways. Using sentences that members of your family would understand, explain why the jovian planets differ from the terrestrial planets in each of the following: composition, size, density, distance from the Sun, and number of satellites.

43) Two Kinds of Planetesimals. Why are there two kinds of "leftovers" from solar system formation? List as many differences between comets and asteroids as you can.

44) Understanding Radiometric Dating. Imagine you had the good fortune to find a rocky meteorite in your backyard. Qualitatively, how would you expect its ratio of potassium-40 to argon-40 to be different from that of other rocks in your yard? Explain why, in a few sentences.

45) Rocks from Other Solar Systems. Many "leftovers" from planetary formation were likely ejected from our solar system, and the same has presumably happened in other star systems.

Given that fact, should we expect to find meteorites that come from other star systems? How rare or common would you expect them to be? (Be sure to consider the distances between stars.)

Suppose that we did find a meteorite identified as a leftover from another stellar system. What could we learn from it?

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46) Dating the Past. Radiometric dating is used in many branches of science. For example, it is used to determine ages of fossils that help us learn the history of life on Earth and ages of relics that teach us about the rise of civilization. Research one use of radiometric dating outside of astronomy, writing a short report on how studies are conducted (such as what materials are dated and what radioactive elements are used) and what these studies have concluded. 47) Lucky to Be Here? Considering the overall process of solar system formation, do you think formation of a planet like Earth was likely? Could random events in the early history of the solar system have prevented our being here today? What implications do your answers have for the possibility of finding planets with Earth-like conditions around other stars? Defend your opinions.

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

48) Radiometric Dating.You are dating rocks by their proportions of parent isotope potassium40 (half-life 1.25 billion years) and daughter isotope argon-40. Find the age for each of the following. a) A rock that contains equal amounts of potassium-40 and argon-40 b) A rock that contains three times as much argon-40 as potassium-40 49) Lunar Rocks. You are dating Moon rocks based on their proportions of uranium-238 (halflife of about 4.5 billion years) and its ultimate decay product, lead. Find the age for each of the following. a) A rock for which you determine that 55% of the original uranium-238 remains, while the other 45% has decayed into lead b) A rock for which you determine that 63% of the original uranium-238 remains, while the other 37% has decayed into lead 50) Carbon-14 Dating. The half-life of carbon-14 is about 5700 years. a) You find a piece of cloth painted with organic dye. By analyzing the dye, you find that only 77% of the carbon-14 originally in the dye remains. When was the cloth painted? b) A well-preserved piece of wood found at an archaeological site has 6.2% of the carbon-14 it must have had when it was living. Estimate when the wood was cut. c) Is carbon-14 useful for establishing Earth's age? Why or why not?

51) Collapsing Cloud. The time it takes for a cloud 100,000 AU in radius to collapse in "freefall" to form a new star is half the time it would take for an object to orbit the star on an extremely elliptical orbit with a semimajor axis of 50,000 AU (half the 100,000 AU radius). Use Kepler's third law to find the collapse time, assuming the star has the same mass as the Sun. 52) Icy Earth. How massive would Earth have to have been to accrete hydrogen compounds in addition to rock and metal? Assume the same proportions of the ingredients as listed in Table 8.1. What would Earth's mass have to have been for Earth to capture hydrogen and helium gas in the proportion listed in the table?

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53) What Are the Odds? The fact that all the planets orbit the Sun in the same direction is cited as support for the nebular hypothesis. Imagine that there's a different hypothesis in which planets can be created orbiting the Sun in either direction. Under this hypothesis, what is the probability that eight planets would end up traveling in the same direction? (Hint: It's the same probability as that of flipping a coin eight times and getting all heads.)

54) Spinning Up the Solar Nebula. The orbital speed of the material in the solar nebula at Pluto's average distance from the Sun was about 5 km/s. What was the orbital speed of this material when it was 40,000 AU from the Sun (before it fell inward with the collapse of the nebula)? Use the law of conservation of angular momentum(see Section 4.3).

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The Cosmic Perspective, 9e (Bennett et al.) Chapter 9 Planetary Geology Section 9.1 1) In order of size from smallest to largest, the five terrestrial worlds are A) Mercury, Venus, Earth, Moon, Mars. B) Mercury, Moon, Venus, Earth, Mars. C) Moon, Mercury, Venus, Earth, Mars. D) Moon, Mercury, Mars, Venus, Earth. E) Mercury, Moon, Mars, Earth, Venus.

Answer: D 2) Which of the following properties is used to distinguish between the core, mantle, and crust of a planet? A) geological activity B) temperature C) rock strength D) density E) color Answer: D 3) The lithosphere of a planet is the layer that consists of A) material above the crust. B) material between the crust and the mantle. C) the rigid rocky material of the crust and uppermost portion of the mantle. D) the softer rocky material of the mantle. E) the lava that comes out of volcanoes. Answer: C 4) Why do terrestrial planet cores contain mostly metal? A) The entire planets are made mostly of metal. B) Metals condensed first in the solar nebula and the rocks then accreted around them. C) Metals are denser than rocks, so they sank to the center when the interiors were molten. D) Radioactivity created metals in the core from the decay of uranium. E) Convection in the mantle carried the metals to the core. Answer: C 5) Which of the following worlds have the thinnest lithospheres? (Hint: The answer is the same no matter whether you think of "thinnest" in actual depth in kilometers or as a proportion of the planet's radius.) A) Earth and the Moon B) Venus and the Moon C) Mercury and Venus D) Earth and Mars E) Earth and Venus Answer: E

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6) Which of the following best describes differentiation in planetary geology? A) Gravity separates molten materials according to density. B) Different types of minerals form a conglomerate rock. C) One planet's surface evolves differently from another planet's surface. D) One part of a planet's surface evolves differently from another part of the same planet's surface. E) Dense materials condense at higher temperatures than less dense materials. Answer: A 7) Which of the following must be true for differentiation to occur in a planet? A) The planet must have a rocky surface. B) The planet must be made of both metal and rock. C) The planet must have an atmosphere. D) The planet must be geologically active, that is, have volcanoes, planetquakes, and erosion from weather. E) The planet must have a molten interior. Answer: E 8) Which internal energy source(s) produce(s) heat by converting gravitational potential energy into thermal energy? A) accretion B) differentiation C) radioactivity D) both accretion and differentiation E) all three of accretion, differentiation, and radioactivity Answer: D 9) Which internal energy source is the most important in continuing to heat the terrestrial planets today? A) accretion B) differentiation C) radioactivity D) tidal heating Answer: C 10) What are the three main sources of internal heat for terrestrial planets? A) conduction, differentiation, and accretion B) accretion, differentiation, and radioactivity C) accretion, differentiation, and eruption D) convection, differentiation, and eruption E) conduction, convection, and eruption Answer: B

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11) Which of the following best describes convection?

A) Rocks sink in water.

B) Warm material expands and rises while cool material contracts and falls.

C) Warm material gets even warmer and cool material gets even cooler.

D) A liquid separates according to density, such as oil and water separating in a jar.

E) Bubbles of gas move upward through a liquid of the same temperature.

Answer: B 12) What is necessary for convection to occur in a substance?

A) The substance must be subjected to a strong magnetic field.

B) Dense material must be added to the substance.

C) The substance is strongly shaken or disturbed by a strong wind.

D) The substance is strongly cooled from underneath.

E) The substance is strongly heated from underneath.

Answer: E 13) What is the main process by which heat flows upward through the lithosphere?

A) conduction B) convection C) radiation D) accretion E) differentiation Answer: A 14) Heat escapes from a planet's surface into space by thermal radiation. In which wavelength range do planets radiate most of their light?

A) infrared B) radio C) visible D) ultraviolet E) x-rays Answer: A 15) Which terrestrial world has the strongest magnetic field?

A) Mars B) Earth C) the Moon D) Venus E) Mercury Answer: B

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16) Why does Earth have the strongest magnetic field among the terrestrial worlds? A) It is the only one that has a metallic core. B) It rotates much faster than any other terrestrial world. C) It is the only one that has both a convecting core region and reasonably rapid rotation. D) It is by far the largest terrestrial world. E) It is the most volcanically active world. Answer: C 17) Which of the following could explain why Venus does not have a strong magnetic field? A) It does not have a metallic core. B) Its rotation is too slow. C) It is too close to the Sun. D) It is too large. E) It has too thick an atmosphere. Answer: B 18) What conditions are thought to be necessary for a terrestrial planet to have a strong magnetic field? A) a molten metallic core only B) fast rotation only C) a rocky mantle only D) both a molten metallic core and reasonably fast rotation E) both a metal core and a rocky mantle Answer: D Section 9.2 1) Approximately how large (across) is an impact crater compared to the size of the impactor? A) the same size B) 10—20 percent larger C) 10 times larger D) 100 times larger E) 1000 times larger Answer: C 2) An impact crater that is 10 kilometers across was probably made by the impact of an object about ________ across. A) 10 meters B) 100 meters C) 1 kilometer D) 10 kilometers E) 100 kilometers Answer: C

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3) Volcanism is more likely on a planet that A) is closer to the Sun. B) is struck often by meteors and solar system debris.

C) has high internal temperature.

D) doesn't have an atmosphere or oceans.

Answer: C 4) How does the lava that forms a steep-sided volcano (a stratovolcano) compare to the lava that forms a shallow-sloped volcano (a shield volcano)?

A) The lava is thicker (higher viscosity) for the steep-sided stratovolcano.

B) The lava is runnier (lower viscosity) for the steep-sided stratovolcano.

C) The lava comes from deeper in Earth's mantle for the steep-sided stratovolcano.

D) The lava comes from a very shallow layer of Earth's crust for the steep-sided stratovolcano.

E) The lava contains more metal for the steep-sided stratovolcano.

Answer: A 5) Which factor below determines the steepness of a volcano?

A) how easily the lava flows B) the temperature of the lava C) the duration of the eruption D) the age of the volcano E) the volume of lava Answer: A 6) What caused Earth's lithosphere to fracture into plates?

A) impacts of asteroids and planetesimals B) internal temperature changes that caused the crust to expand and stretch C) convection of the underlying mantle D) tidal forces from the Moon and Sun E) volcanism, which produced heavy volcanoes that bent and cracked the lithosphere Answer: C 7) Which of the following best describes tectonics?

A) the creation of bowl-shaped depressions by asteroids or comets striking a planet's surface B) the eruption of molten rock from a planet's interior to its surface C) the disruption of a planet's surface by internal stresses D) the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather Answer: C 8) A planet is most likely to have volcanic and tectonic activity if it has A) low surface gravity.

B) high surface gravity.

C) low internal temperature.

D) high internal temperature.

E) a dense atmosphere.

Answer: D

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9) How were the relatively few craters that we see within the lunar maria formed? A) by impacts that occurred before those that formed most of the craters in the lunar highlands B) by impacts that occurred after those that formed most of the craters in the lunar highlands C) by the same large impactor that led to the formation of the maria D) They are volcanic in origin, rather than from impacts. E) They are sinkholes that formed when sections of the maria collapsed. Answer: B 10) What can we conclude when we see a region of a planet that is not as heavily cratered as other regions? A) There is little volcanic activity to create craters. B) The planet is rotating very slowly and only one side was hit by impactors. C) The planet formed after the age of bombardment and missed out on getting hit by leftover planetesimals. D) The surface in the region is older than the surface in more heavily cratered regions. E) The surface in the region is younger than the surface in more heavily cratered regions. Answer: E Section 9.3 1) How did the relatively smooth regions on the Moon known as the lunar maria form? A) Large impacts fractured the Moon's lithosphere, allowing lava to fill the impact basins. B) The early bombardment created heat that melted the lunar surface in the regions of the maria. C) Volatiles escaping from the Moon's interior heated and eroded the surface in the regions of the maria. D) The giant impact that created the Moon left smooth areas that we call the maria. E) The maria are the result of gradual erosion by micrometeorites striking the Moon. Answer: A 2) Left undisturbed, the footprints left on the Moon by the Apollo astronauts will likely A) already have been erased by erosion. B) remain visible for a few more decades. C) remain visible for millions of years. D) remain permanently visible on the Moon. Answer: C 3) The Caloris Basin on Mercury covers a large region of the planet and contains relatively few smaller craters. From this, we conclude that A) erosion destroyed most of the smaller craters that formed on the basin. B) Mercury's atmosphere prevented smaller objects from hitting the surface. C) only very large impactors hit Mercury's surface in the past. D) the Caloris Basin formed toward the end of the heavy bombardment. E) the Caloris Basin was formed by a volcano. Answer: D

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4) Which of the following is the best explanation for the tremendous cliffs on Mercury? A) They were probably carved in Mercury's early history by running water. B) They were probably formed by tectonic stresses when the entire planet shrank as its core cooled. C) They probably formed when a series of large impacts hit Mercury one after the other. D) They are almost certainly volcanic in origin, carved by flowing lava. E) They represent one of the greatest mysteries in the solar system, as no one has suggested a reasonable hypothesis for their formation. Answer: B Section 9.4 1) Valles Marineris is a A) large valley on the Moon. B) vast plain on Mars. C) huge series of cliffs on Mercury. D) large canyon on Mars. E) large canyon on Venus. Answer: D 2) The polar caps on Mars are composed of A) frozen carbon dioxide only. B) water ice only. C) both frozen carbon dioxide and water ice. D) frozen hydrogen. E) salt deposits. Answer: C 3) Which of the following does not provide evidence that Mars once had large amounts of liquid water on its surface? A) the presence of what looks like dried-up riverbeds B) the presence of impact craters that appear to have formed in mud C) the vast canal system described by Percival Lowell D) the presence of minerals, dry clay, and sedimentary rock that form in water E) some very old craters that appear to have been eroded by rain Answer: C 4) Rovers sent to Mars have discovered A) minerals in Martian rocks that can only form in liquid water. B) clear evidence that life once existed on Mars. C) Mars has more craters than previously thought. D) small pockets of liquid water lying just beneath the Martian soil. Answer: A

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5) Based on current evidence, when is/was liquid water abundant on the surface of Mars?

A) only before about 3 billion years ago B) only during the first 1 million years of Mars's existence C) Water comes and goes, with the most recent water flows occurring a few thousand years ago.

D) only during the most recent 1 billion years of Mars's history Answer: A 6) Which of the following worlds show evidence of dried up rivers and lake beds?

A) the Moon B) Mercury C) Venus D) Mars E) all of the above Answer: D Section 9.5 1) How have we been able to construct detailed maps of surface features on Venus?

A) by studying Venus from Earth with powerful telescopes B) by studying Venus with powerful optical telescopes on spacecraft that were sent to orbit Venus C) by making computer models of geological processes on Venus D) by using radar from spacecraft that were sent to orbit Venus E) by landing spacecraft on the surface for close-up study Answer: D 2) Which two geological processes appear to have been most important in shaping the present surface of Venus?

A) impacts and volcanoes B) impacts and tectonics C) tectonics and erosion D) volcanoes and tectonics E) volcanoes and erosion Answer: D 3) Why can't astronomers study the surface of Venus with visible light telescopes?

A) Venus' thick atmosphere prevents us from seeing the surface.

B) We do not have telescopes with good enough angular resolution.

C) Venus doesn't reflect any visible light.

Answer: A

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Section 9.6 1) What process has played the greatest role in determining the arrangement of the continents on Earth? A) impact cratering B) volcanism C) plate tectonics D) erosion E) acid rain Answer: C 2) Which of the following is not evidence for plate tectonics on Earth? A) Some continental boundaries fit together like pieces of a jigsaw puzzle. B) Similar rocks and fossils are found in different continents. C) high ocean ridges between the continents D) the existence of volcanoes E) earthquakes Answer: D 3) On average, approximately how fast do plates move with plate tectonics on Earth? A) a few centimeters per year B) a few millimeters per century C) a few centimeters per century D) They do not move at all, except during earthquakes. E) a few kilometers per hour Answer: A 4) According to current understanding of plate tectonics, which of the following is true about Earth's seafloors? A) They are built from rocks that are older than the rocks found on the continents. B) They represent the thickest regions of Earth's crust. C) Their material is almost completely recycled over a time period of about 200 million years. D) They should be covered with numerous impact craters dating to the time of the heavy bombardment. Answer: C 5) Ridges in the middle of the ocean are places where A) one plate slides under another, returning older crust to the mantle. B) hot mantle material rises upward, creating volcanic islands. C) hot mantle material rises upward and spreads sideways, pushing the plates apart. D) plates push together, creating ocean mountain chains. E) plates slip sideways relative to one another. Answer: C

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6) Deep trenches in the ocean mark places where A) one plate slides under another, returning older crust to the mantle. B) plates pull apart, leaving great rifts in the crust. C) hot mantle material rises upward and spreads sideways, pushing the plates apart. D) plates push together, creating ocean mountain chains. E) plates slip sideways relative to one another. Answer: A 7) The islands of Hawaii were created by A) thin continental crust separating and creating a rift valley. B) plumes of hot mantle rising in a hot spot within a plate. C) plates that have slipped sideways relative to each other, creating a fault. D) a plate that has run up against an existing continental plate. E) a fault. Answer: B 8) What is the main factor that makes Earth more geologically active than the other terrestrial planets? A) It is larger, so it has retained its internal heat for longer. B) It is farthest from the Sun, so it receives less light. C) It has a large Moon, so it is heated by tidal forces. D) It has far more radioactive material than other planets. E) It formed much later than the other planets. Answer: A General Chapter Questions 1) Which of the following best describes why the smaller terrestrial worlds have cooler interiors than the larger ones? A) They were cooler when they formed. B) The smaller ones are farther from the Sun. C) They have relatively fewer radioactive elements. D) They have relatively more surface area compared to their volumes. E) They had more volcanic eruptions in the past, which released their internal heat. Answer: D 2) Which of the following surface features may result from tectonics? A) mountains B) valleys C) volcanos D) cliffs E) all of the above Answer: E

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3) Spacecraft have landed on all the terrestrial worlds except A) Mercury.

B) Venus.

C) Moon.

D) Mars.

E) Spacecraft have landed on all of the terrestrial worlds.

Answer: E Short Answer Questions 1) Describe the three sources of internal heat of the terrestrial planets.

Answer: Accretion is heat generated by the agglomeration of planetesimals when the planet was formed. Differentiation is heat generated by the energy released as dense objects fall toward the center of a planet during the formation of the core of a planet. Radioactive decay generates heat by releasing nuclear energy when an unstable (radioactive) isotope decays into a more stable element.

2) Explain how we can estimate the geological age of a planetary surface from its number of impact craters.

Answer: Even though impacts still occur today, the vast majority of craters formed during the bombardment period that ended around 3.8 billion years ago. A surface region that is still saturated with craters must have remained essentially undisturbed for the last 3.8 billion years. In contrast, a surface region that has few craters indicates that the original craters must have been "erased" by other geological processes since then.

3) What evidence suggests that Mercury contracted within about a billion years after it formed?

Answer: The surface of Mercury is marked by long, high cliffs. Such features result from tectonic compression, but there are no corresponding features due to tectonic stretching. This suggests the whole planet contracted as it rapidly cooled in its early history. We can date the contraction from the age of the volcanic flows on its surface: volcanic (and all geologic) activity probably came to an abrupt halt as a result of the planet's contraction.

4) List at least three things that make Earth unique among the terrestrial planets.

Answer: Many possible answers, including: It is the only planet with an oxygen-rich atmosphere; it is the only planet with an ozone layer; it is the only planet with surface liquid water; it is the only planet with a surface that has been significantly altered by plate tectonics; its climate has been stable enough for liquid water to persist for billions of years; it has a very large Moon relative to its size; it is the only planet we know of that harbors life.

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Reading Quiz Questions 1) Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of A) a golf ball to a baseball. B) a dust speck to a golf ball. C) a dust speck to a basketball. D) a golf ball to a beach ball. Answer: A 2) From center to surface, which of the following correctly lists the interior layers (defined by density) of a terrestrial world? A) core, mantle, crust B) mantle, core, crust C) mantle, crust, core D) core, crust, lithosphere Answer: A 3) What do we mean when we say that the terrestrial worlds underwent differentiation? A) When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces. B) The five terrestrial worlds all started similarly but ended up looking quite different. C) Their surfaces show a variety of different geological features resulting from different geological processes. D) They lost interior heat to outer space. Answer: A 4) A terrestrial world's lithosphere is A) a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle. B) a thin layer of rock that lies between the mantle and crust. C) the interior region in which the planet's magnetic field is generated. D) a layer of hot, molten rock encompassing the core and part of the mantle. Answer: A

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5) The three major processes that heat the interiors of the terrestrial worlds are A) (1) heat deposited as the planets were built from planetesimals (2) heat deposited as the planets underwent differentiation (3) heat released by radioactive decay.

B) (1) heat deposited as the planets were built from planetesimals (2) heat of accretion (3) heat that came from the gravitational potential energy of incoming planetesimals.

C) (1) heat of accretion (2) heat from convection (3) heat from thermal radiation.

D) (1) volcanism (2) tectonics (3) erosion.

Answer: A 6) Which of the following is an example of convection?

A) warm air expanding and rising, while cooler air contracts and falls B) different kinds of material separating by density, like oil and water C) rocks sinking in water D) gas bubbling upward through a liquid Answer: A 7) What are the basic requirements for a terrestrial world to have a global magnetic field?

A) a core layer of molten, convecting material and sufficiently rapid rotation B) a metal core and rapid rotation C) a metal core, a rocky mantle, and sufficiently rapid rotation D) a core that has a molten layer and a mantle that has convection Answer: A 8) The processes responsible for virtually all surface geology are A) impact cratering, volcanisms, tectonics, and erosion.

B) convection, conduction, and radiation.

C) accretion, differentiation, and radioactive decay.

D) eruptions, lava flows, and outgassing.

Answer: A 9) In the context of planetary geology, what do we mean by outgassing?

A) the release by volcanism of gases that had been trapped in a planetary interior B) the loss of atmospheric gas to outer space C) another name for a volcanic eruption D) the evaporation of water that adds water vapor (a gas) to an atmosphere Answer: A

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10) Which of the following is not an example of tectonics?

A) the gradual disappearance of a crater rim as a result of wind and rain B) the formation of a cliff when the lithosphere shrinks C) the slow movement of Earth's lithospheric plates D) the stretching of the crust by underlying mantle convection Answer: A 11) Which of the following best describes the lunar maria?

A) relatively smooth, flat plains on the Moon B) densely cratered regions on the Moon C) mountainous regions on the Moon D) frozen oceans of liquid water on the Moon Answer: A 12) Why does the Moon have a layer of "powdery soil" on its surface?

A) It is the result of countless tiny impacts by small particles striking the Moon.

B) Recent, large impacts shattered lunar rock to make this soil.

C) It is made by the same processes that make powdery sand on Earth.

D) It exists because the Moon accreted from powdery material after a giant impact blasted the Earth.

Answer: A 13) What observational evidence supports the idea that Mercury once shrank by some 20 kilometers in radius?

A) the presence of many long, tall cliffs B) the presence of many impact craters C) the characteristics of the Caloris Basin D) Mercury's unusually high density Answer: A 14) Olympus Mons is A) a huge shield volcano on Mars.

B) a huge stratovolcano on Venus.

C) a large lava plain on the Moon.

D) a great canyon on Mars.

Answer: A 15) Which of the following is not a key line of evidence supporting the hypothesis that Mars once had abundant liquid water on its surface?

A) the canals of Mars mapped by Percival Lowell B) small, rounded pebbles found in places that look like dry riverbeds C) chemical analysis of minerals found in what appear to be ancient lakebeds D) the eroded rims of ancient craters Answer: A

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16) Based on its surface features, the most important event on Venus in the past billion years or so was A) a global "repaving" that erased essentially all the surface features that had existed earlier B) the eruption of a giant volcano that formed one of Venus's "continents" C) the impact of an unusually large asteroid that left a deep scar on one side of the planet D) the onset of mantle convection, which caused Venus's lithosphere to split into plates like those on Earth Answer: A 17) On average, how fast do the plates move on the Earth?

A) a few centimeters per year B) a few millimeters per century C) about 1 mile per hour D) a few kilometers per year Answer: A 18) How does seafloor crust differ from continental crust?

A) Seafloor crust is thinner, younger, and higher in density.

B) Seafloor crust is thicker, older, and higher in density.

C) Seafloor crust is thicker, younger, and lower in density.

D) Seafloor crust is thinner, older, and lower in density.

Answer: A 19) In the context of plate tectonics, what is a subduction zone?

A) a place where a seafloor plate is sliding under a continental plate B) a place where two plates are slipping sideways against one another C) a place where two plates are pulling apart D) a place where two continental plates are colliding Answer: A 20) Which of the following places is the result of volcanoes erupting over a hot spot in the mantle?

A) Hawaii B) the Himalayas C) the Appalachians D) California Answer: A Concept Quiz Questions 1) The cores of the terrestrial worlds are made mostly of metal because A) metals sunk to the centers a long time ago when the interiors were molten throughout.

B) the terrestrial worlds as a whole are made mostly of metal.

C) the core contained lots of radioactive elements that decayed into metals.

D) over billions of years, convection gradually brought dense metals downward to the core.

Answer: A

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2) Which of the following is not generally true of all the terrestrial world lithospheres?

A) The lithosphere is broken into a set of large plates that float on the softer rock below.

B) Rock in the lithosphere is stronger than rock beneath it.

C) The lithosphere extends from somewhere in the mantle all the way to the surface.

D) The thickness of the lithosphere depends on interior temperature, with cooler interiors leading to thicker lithospheres.

Answer: A 3) Which internal heat source still generates heat within the terrestrial worlds today?

A) heat from radioactive decay B) heat of accretion C) heat from differentiation D) heat from convection Answer: A 4) The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that A) a large baked potato takes longer to cool than a small baked potato.

B) gas bubbles form and rise upward in boiling water.

C) Earth contains more metal than the Moon.

D) thunderstorms tend to form on hot summer days.

Answer: A 5) Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?

A) Not much: on human time scales, the mantle looks like solid rock.

B) hot molten rock rising upward throughout the mantle and cool, solid rock falling downward C) a rapid, up and down churning of the material in the mantle D) dense metals falling downward and low-density rock rising upward Answer: A 6) Scientists suspect that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?

A) Mars's interior has cooled so much that its molten core layer no longer undergoes convection.

B) Mars rotates much slower than the Earth.

C) The Martian core is made of rock, while Earth's core is made of metal.

D) Mars is too far from the Sun to have a global magnetic field.

Answer: A 7) Which of the following most likely explains why Venus does not have a global magnetic field like Earth?

A) Its rotation is too slow.

B) It does not have a metallic core.

C) Unlike Earth, Venus does not have a liquid outer core.

D) It has too thick of an atmosphere.

Answer: A

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8) You discover an impact crater that is 10 kilometers across. Which of the following can you conclude?

A) It was created by the impact of an object about 1 kilometer across.

B) It was created by the impact of an object about 10 kilometers across.

C) It was created within the past 10 million years.

D) It was created within the past 1 billion years.

E) It was created by the impact of an object about 100 kilometers across.

Answer: A 9) Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?

A) The maria formed after the heavy bombardment ended.

B) The maria formed within the past 1 billion years.

C) The regions of the maria were hit by fewer impacts than the densely cratered regions.

D) Erosion affects the maria more than it affects other regions of the Moon.

Answer: A 10) Which of the following is the underlying reason why Venus has so little wind erosion?

A) its slow rotation B) its small size C) its thick atmosphere D) its relatively close distance to the Sun Answer: A 11) Which of the following best describes the geological histories of the Moon and Mercury?

A) Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.

B) Impact cratering is the only major geological process that has affected their surfaces.

C) All four geological processes were important in their early histories, but only tectonics still reshapes their surfaces today.

D) Impact cratering shaped these worlds early in their histories. Then, during the past few million years, they were reshaped by episodes of volcanism and tectonics.

Answer: A 12) Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?

A) the high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle B) the smaller size of Venus, which has allowed it to lose much more internal heat than Earth C) the slow rotation of Venus D) the apparent lack of plate tectonics on Venus Answer: A

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13) All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?

A) Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.

B) Venus has many circular features, called coronae, which appear to be tectonic in origin.

C) Venus's largest features are three elevated regions that look somewhat like continents.

D) Venus appears to lack any water that could lubricate the flow of rock in its crust and mantle.

Answer: A 14) What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?

A) plate tectonics and a high level of erosion B) a dense core and plate tectonics C) significant volcanism and tectonics D) mantle convection and a thick atmosphere Answer: A 15) Why are there fewer large impact craters on Earth's seafloor than on the continents?

A) Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts.

B) The oceans slow large impactors and prevent them from making craters.

C) Erosion erases impact craters must faster on the ocean bottom than on land.

D) Most impacts occur on the land.

Answer: A 16) Why is Earth's continental crust lower in density than seafloor crust?

A) Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones.

B) Continental crust is made from the volcanic rock called basalt.

C) Continental crust comes from volcanoes, while seafloor crust comes from geysers.

D) Continental crust comes from Earth's inner core, while seafloor crust comes from the outer core.

Answer: A 17) Which two factors are most important to the existence of plate tectonics on Earth?

A) mantle convection and a thin lithosphere B) oxygen in the atmosphere and mantle convection C) the existence of life and oxygen in the atmosphere D) Earth's liquid outer core and solid inner core Answer: A

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18) What's the fundamental reason that Mars has so little geological activity compared to Earth? A) its small size compared to Earth B) its large size compared to the Earth C) its farther distance than Earth to the Sun D) its closer distance than Earth to the Sun E) its rapid rotation compared to the Earth F) its slow rotation compared to the Earth Answer: A 19) Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny? A) its size B) its composition C) its distance from the Sun D) whether or not it has liquid water Answer: A 20) The choices describe four hypothetical planets. Which one would you expect to have the hottest interior? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.) A) Size: twice as big as Earth Distance from Sun: same as Mercury Rotation rate: once every 6 months B) Size: same as the Moon Distance from Sun: same as Mars Rotation rate: once every 10 days C) Size: same as Mars Distance from Sun: same as Earth Rotation rate: once every 18 hours D) Size: same as Venus Distance from Sun: same as Mars Rotation rate: once every 25 hours Answer: A

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21) The choices describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.) A) Size: same as the Moon Distance from Sun: same as Mars Rotation rate: once every 10 days B) Size: twice as big as Earth Distance from Sun: same as Mercury Rotation rate: once every 6 months C) Size: same as Mars Distance from Sun: same as Earth Rotation rate: once every 18 hours D) Size: same as Venus Distance from Sun: same as Mars Rotation rate: once every 25 hours Answer: A 22) The choices describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.) A) Size: same as Venus Distance from Sun: same as Mars Rotation rate: once every 25 hours B) Size: same as the Moon Distance from Sun: same as Mars Rotation rate: once every 10 days C) Size: same as Mars Distance from Sun: same as Earth Rotation rate: once every 18 hours D) Size: twice as big as Earth Distance from Sun: same as Mercury Rotation rate: once every 6 months Answer: A

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Visual Quiz Questions 1) This photo was taken from orbit around some planet. What planet is it, and how do you know?

A) Mars because we see dried up riverbeds B) the Moon because it has craters C) Venus because of its yellowish color D) Mercury because we see gigantic cliffs Answer: A 2) The geological feature in this photo is

A) an impact crater.

B) a volcano.

C) the unusual cloud formation in the background.

D) a dried up lake basin.

Answer: A

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3) These four photos show features of Earth that change with time, some fast and some slow.

Which one of these features is being shaped primarily by the process we call tectonics?

A)

B)

C)

D)

Answer: A

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4) Which of the four labeled arrows in this photo of the full moon is point to one of the lunar maria?

A) Arrow 1 B) Arrow 2 C) Arrow 3 D) Arrow 4 Answer: A 5) This photo, taken from orbit of Mars, shows a feature known as

A) Olympus Mons B) Valles Marineris C) Ishtar Terra D) Hellas Basin Answer: A 6) This photo from the Curiosity rover shows what appears to be layered sedimentary rock on Mars. What does this photo seem to be telling us?

A) This region of Mars once held a body of water such as a lake.

B) Mars still has active volcanoes.

C) It still rains on Mars at least once every few million years.

D) There must not be any wind on Mars, or these features would have been erased.

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7) This image shows two tall volcanoes on Venus. Why is it yellow?

A) The yellow color is arbitrary because this image was created with radar data rather than visible light.

B) Lava from volcanoes on Venus is yellow rather than the red of lava on Earth.

C) The camera used to take this photograph had a yellow filter on it.

D) Venus is yellow all over, apparently as a result of some sort of sulfurous dust that coats its surface.

Answer: A 8) What is the significance of the yellow lines on this map of Earth?

A) They represent boundaries between the plates that make up Earth's lithosphere.

B) They represent borders between continents.

C) The yellow lines are lined everywhere by chains of volcanoes.

D) The yellow lines represent the locations of deep trenches.

Answer: A

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9) This diagram represents the conveyor-like action of plate tectonics on Earth. Which numbered position represents a place where new seafloor crust is being made?

A) Position 1 B) Position 2 C) Position 3 D) Position 4 Answer: B

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10) This figure summarizes the geological histories of the terrestrial worlds. Based on this figure, what can you conclude?

A) The most important factor in a planet's geological history is its size.

B) The most important factor in a planet's geological history is its distance from the Sun. C) We can trace almost all the key properties of a planet's geology back to the number of impacts it suffered during the heavy bombardment.

D) Earth is the only planet in the inner solar system capable of harboring life.

Answer: A

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

This image from the MESSENGER spacecraft shows evidence of impact cratering, volcanism, and tectonic activity on Mercury. Answer the following questions based on the image. Remember that craters are bowl-shaped and rough-floored when they form, and wipe out any preexisting features in the area. Lava on Mercury appears to be fairly runny and makes flat smooth plains as it spreads out.

1) Label 1a lies on the rim of a large crater, and label 1b lies on the rim of a smaller one. Which crater must have formed first?

A) crater 1a B) crater 1b C) cannot be determined Answer: A 2) The region around 2b has far fewer craters than the region around 2c) The crater floor at 2a is also flat and smooth, without many smaller craters on it. Why are regions 2a and 2b so smooth?

A) Few small craters ever formed in these regions.

B) Erosion erased craters that once existed in these regions.

C) Lava flows covered craters that once existed in these regions.

Answer: C

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3) A tectonic ridge appears to connect points 3a and 3b, crossing several craters. From its appearance, we can conclude that it must have formed A) before the area was cratered.

B) after the area was cratered.

C) at the same time the area was cratered.

Answer: B 4) Rank the following features in order from oldest to youngest: a) the tectonic ridge from 3a to 3b b) crater 1a c) the smooth floor of crater 1b Answer: b, c, a Chapter Review Questions 1) Describe the core-mantle-crust structures of the terrestrial worlds, and how they imply differentiation. What is a lithosphere, and how does lithospheric thickness vary among the five terrestrial worlds?

2) Summarize the processes by which planetary interiors get hot and cool off. Why do large planets retain internal heat longer than smaller planets?

3) Why does Earth have a global magnetic field? Why don't the other terrestrial worlds have similarly strong magnetic fields?

4) Define each of the four major geological processes, and give examples of features shaped by each process.

5) What is outgassing, and why is it so important to our existence?

6) Why is the Moon so much more heavily cratered than Earth? Explain how crater counts tell us the age of a surface.

7) Summarize the ways in which a terrestrial world's size, distance from the Sun, and rotation rate each affect its relative level of impact cratering, volcanism, tectonics, and erosion.

8) Briefly summarize the geological history of the Moon. How did the lunar maria form?

9) Briefly summarize the geological history of Mercury. How are Mercury's great cliffs thought to have formed?

10) Choose five features on the global map of Mars (Figure 9.25) and explain the nature and likely origin of each.

11) Why isn't liquid water stable on Mars today, and why do we nonetheless think it flowed on Mars in the distant past?

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12) Choose at least three major geological features of Venus and explain how we think each one formed.

13) What evidence tells us that Venus was "repaved" about 750 million years ago? What might account for the lack of plate tectonics on Venus?

14) Describe the conveyor-like action of plate tectonics on Earth, and how it explains the differences between seafloor and continental crust.

15) Briefly explain how each of the following geological features of Earth is formed: seafloors, continents, islands, mountain ranges, rift valleys, and faults.

16) To what extent do we think the geologies of the terrestrial worlds were destined from their birth? Explain.

Surprising Discoveries?

Suppose we were to make the following discoveries. (These are not real discoveries.) In light of your understanding of planetary geology, decide whether the discovery should be considered reasonable or surprising. (In some cases, both views can be defended.) Explain your answer clearly, ideally in terms of fundamental properties of size, distance from the Sun, and rotation rate.

17) New photographs reveal sand dunes on Mercury.

18) Seismographs placed on the surface of Mercury record frequent and violent earthquakes.

19) A new orbiter observes a volcanic eruption on Venus.

20) A Venus radar mapper discovers extensive regions of layered sedimentary rocks.

21) Radiometric dating of rocks brought back from one lunar crater shows that the crater was formed only a few tens of millions of years ago.

22) New high-resolution orbital photographs of Mars show many crater bottoms filled with pools of liquid water.

23) Drilling into the slopes of a Martian volcano, a robotic spacecraft discovers liquid water beneath the surface.

24) Clear-cutting in the Amazon rain forest on Earth exposes terrain that is as heavily cratered as the lunar highlands.

25) Seismic studies on Earth reveal a "lost continent" that held great human cities just a few thousand years ago but is now buried deep under water off the western coast of Europe.

26) We find a planet in another solar system that has Earth-like plate tectonics; the planet is the size of the Moon and orbits 1 AU from its star.

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27) We find a planet in another solar system that is as large as Earth but as heavily cratered as the Moon.

28) We find a planet in another solar system that has Earth-like seafloor crust and continental crust but apparently lacks plate tectonics or any other kind of crustal motion.

Quick Quiz 29) What is the longest-lasting internal heat source responsible for geological activity?

A) accretion B) radioactive decay C) sunlight Answer: No Correct Answer Was Provided.

30) In general, what kind of terrestrial planet would you expect to have the thickest lithosphere?

A) a large planet B) a small planet C) a planet far from the Sun Answer: No Correct Answer Was Provided.

31) The major way in which we learn about Earth's interior is through A) drilling deep into the crust.

B) studying seismic waves.

C) spacecraft imagery.

Answer: No Correct Answer Was Provided.

32) Which of a planet's fundamental properties has the greatest effect on its level of volcanic and tectonic activity?

A) size B) distance from the Sun C) rotation rate Answer: No Correct Answer Was Provided.

33) What is the name of the rigid outer layer of a planet?

A) crust B) mantle C) lithosphere Answer: No Correct Answer Was Provided.

34) Which describes our understanding of flowing water on Mars?

A) It was never important.

B) It was important once, but is no longer.

C) It is a major process on the Martian surface today.

Answer: No Correct Answer Was Provided.

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35) What do we conclude if a planet has few impact craters of any size? A) The planet was never bombarded by asteroids or comets. B) Its atmosphere stopped impactors of all sizes. C) Other geological processes have wiped out craters. Answer: No Correct Answer Was Provided. 36) How many of the five terrestrial worlds have surfaces being continually reshaped by plate tectonics? A) one B) two C) three or more Answer: No Correct Answer Was Provided. 37) On how many of the five terrestrial worlds has erosion been an important process? (Be sure that you explain why erosion is important on this many worlds and not more.) A) one B) two C) three or more Answer: No Correct Answer Was Provided. 38) How many of the terrestrial worlds have lava plains or shallow-sloped volcanoes? A) one B) three C) five Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

39) Group Discussion: Putting Women in Charge.

On February 23, 2008, NASA arranged work schedules to put an all-woman team in charge of the Mars Exploration Rovers' tactical operations. It was the first time an all-woman team was given full responsibility for a major NASA mission's operations, even for a single day, and it was done in honor of the upcoming Women's History Month. a) Gather in groups of three and discuss why it was considered unusual to have an all-woman team in charge of a NASA mission's operations. b) Discuss societal factors that may discourage women from pursuing careers in space science or space exploration, and how these might be changed to encourage greater inclusion of and participation by women in these fields. Make a list of specific actions you would recommend NASA take. c) Do you think a symbolic event such as the all-woman Mars Rovers' operations team helps to promote long-term inclusion of women in science? Why or why not?

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The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

40) Mars Attracts.William Herschel, Giovanni Schiaparelli, and Percival Lowell were all respected astronomers who made important and widely accepted discoveries, yet all three jumped to incorrect conclusions about Mars. Scientifically, where do you think each went wrong, and how seriously? Try to frame your answer in terms of the hallmarks of science discussed in Chapter 3. Do you think their mistakes had any long-term impact on the study of Mars?

41) What Is Predictable? Briefly explain why much of a planet's geological history is destined from its birth, and discuss the level of detail that is predictable. For example, was Mars's general level of volcanism predictable? Could we have predicted a mountain as tall as Olympus Mons or a canyon as long as Valles Marineris? Explain.

42) Worth the Effort? Politicians often argue over whether planetary missions are worth the expense involved. If you were in Congress, would you support more or fewer missions? Why? 43) Evidence of Our Civilization. Discuss how Earth's geological processes would affect the evidence of our current civilization in the distant future, under the assumption that our civilization were to end today. For example, what evidence of our civilization would survive in 100,000 years? In 100 million years? Would future archaeologists or alien visitors be able to know that our civilization had existed? Does thinking about the potential end of our civilization affect the way you think about what we can do to help our civilization survive? Explain.

44) Unanswered Questions. Current understanding allows us to paint a broad-brush overview of the geological histories of the terrestrial worlds, but we have much more to learn. Choose one important but unanswered question related to the geology of the terrestrial worlds, and describe why the question is important and how we might answer it in the future. Be as specific as possible, focusing on the type of evidence necessary to answer the question and how the evidence could be gathered.

45) Group Discussion: Real and Imaginary Planets. Work in small groups to discuss Figure 9.16.Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39. a) Figure 9.16 shows seven "cartoon" worlds. Decide which terrestrial world or worlds in our solar system best match the listed characteristics for each cartoon. b) Study the blue annotations associated with each of the seven cartoon worlds. For each cartoon, find a real planetary image in the chapter that exemplifies the principle described by at least one of its annotations; explain clearly. c) Choose one terrestrial world in our solar system (do not choose Earth), and imagine that one of its properties (size, distance, or rotation rate) had been significantly different. How would you expect this world's geological history to have been different? d) Propose two imaginary planets whose size, distance from the Sun, and rotation rates are different from each other and different from those of all of our solar system's terrestrial worlds.

Give your planets names and predict their geological histories, clearly explaining how you make your predictions.

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Investigate Further 46) Dating Planetary Surfaces. We have discussed two basic techniques for determining the age of a planetary surface: studying the abundance of impact craters and radiometric dating of surface rocks. Which technique seems more reliable? Which technique is more practical?

Explain.

47) Comparative Erosion. Of Mercury, Venus, the Moon, and Mars, which world has the greatest erosion? Why? Write a paragraph explaining each world's level of erosion, tracing it back to fundamental properties.

48) Miniature Mars. Suppose Mars had turned out to be significantly smaller than its current size–say, the size of our Moon. How would this have affected the number of geological features due to each of the four major geological processes? Do you think Mars would be a better or worse candidate for harboring extraterrestrial life? Summarize your answers in two or three paragraphs.

49) Change in Fundamental Properties. Choose one property of Earth–either size or distance from the Sun–and suppose that it had been significantly different. Describe how this change might have affected Earth's subsequent geological history and the possibility of our existence today on Earth.

50) Predictive Geology. Suppose another star system has a rocky terrestrial planet twice as large as Earth but at the same distance from its star (which is just like our Sun) and with a similar rotation rate. In one or two paragraphs, describe the type of geology you would expect it to have.

51) Mystery Planet. It's the year 2098, and you are designing a robotic mission to a newly discovered planet around a nearby star that is nearly identical to our Sun. The planet is as large in radius as Venus, rotates with the same daily period as Mars, and lies 1.2 AU from its star. Your spacecraft will orbit but not land on the planet. a) Some of your colleagues believe that the planet has no metallic core. How could you support or refute their hypothesis? b) Other colleagues suspect that the planet has no atmosphere, but the instruments designed to study the planet's atmosphere fail because of a software error. However, the spacecraft can still photograph geological features. How could you use the spacecraft's photos of geological features to determine whether a significant atmosphere is (or was) present on this planet?

52) "Coolest" Surface Photo. Visit the Astronomy Picture of the Day website, and search for archived images of the terrestrial worlds. Look at many of them, and choose the one you think is the "coolest." Write a short description of what it shows, and explain what you like about it.

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53) Experiment: Planetary Cooling in a Freezer. Fill two small plastic containers of similar shape but different sizes with cold water and put both into the freezer at the same time. Every hour or so, record the time and estimate the thickness of the "lithosphere" (the frozen layer) in the two tubs. How long does it take the water in each tub to freeze completely? Describe the relevance of your experiment to planetary geology. Extra credit: Plot your results on a graph with time on the x-axis and lithospheric thickness on the y-axis. What is the ratio of the two freezing times?

54) Amateur Astronomy: Observing the Moon. Any amateur telescope has resolution adequate for identifying geological features on the Moon. The light highlands and dark maria should be evident, and shadowing should be visible near the line between night and day. Try to observe the Moon near the first- or third-quarter phase. Sketch or photograph the Moon at low magnification, and then zoom in on a region of interest. Again sketch or photograph your field of view, labeling its features and identifying the geological process that created them. Look for craters, volcanic plains, and tectonic features. Estimate the size of each feature by comparing it to the size of the entire Moon (radius = 1738 km).

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

55) Surface Area—— to Volume Ratio.Compare the surface area—to—volume ratios of (a) the Moon and Mars and (b) Earth and Venus. In each case, use your answer to discuss differences in the internal heat of the two worlds.

56) Doubling Your Size. Just as the surface area—to—volume ratio depends on size, so can other properties. To see how, suppose that your size suddenly doubled–that is, your height, width, and depth all doubled. (For example, if you were 5 feet tall before, you now are 10 feet tall.) a) By what factor has your waist size increased? b) How much more material will be required for your clothes? (Hint: Clothes cover the surface area of your body.) c) By what factor has your weight increased? (Hint: Weight depends on the volume of your body.) d) The pressure on your weight-bearing joints depends on how much weight is supported by the surface area of each joint. How has this pressure changed?

57) Lunar Footprints. Assume that the Moon is hit by about 25 million micrometeorite impacts each day (this number comes from observations of meteors in Earth's atmosphere) and that these impacts strike randomly around the Moon's surface. Also assume that it takes about 20 such impacts to destroy a footprint. About how long would it take for one of the footprints left by the Apollo astronauts to be erased? (Hints: Use the Moon's surface area to determine the impact rate per square centimeter, and estimate the size of a footprint.)

58) Geological Proportions. Express the approximate height and width of Olympus Mons (26 km tall and 600 km wide) as percentages of Mars's radius. Repeat for Valles Marineris (7 km deep and 4000 km long). Then compare the height of Mount Everest (9 km tall) and the height and width of the Grand Canyon (1.8 km deep and 450 km long) to Earth's radius, and comment on the relative sizes of geological features on the two planets.

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59) Internal vs. External Heating. In daylight, Earth's surface absorbs about 400 watts per square meter. Earth's internal radioactivity produces a total of 30 trillion watts that leak out through our planet's entire surface. Calculate the amount of heat from radioactive decay that flows outward through each square meter of Earth's surface (your answer should have units of watts per square meter). Compare quantitatively to solar heating, and comment on why internal heating drives geological activity.

60) Plate Tectonics. Typical motion of one plate relative to another is 1 centimeter per year. At this are rate, how long would it take for two continents 3000 kilometers apart to collide? What the global consequences of motion like this?

61) More Plate Tectonics. Consider a seafloor spreading zone creating 1 centimeter of new crust over its entire 2000-kilometer length every year. How many square kilometers of surface will be created in 100 million years? What fraction of Earth's surface does this constitute?

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The Cosmic Perspective, 9e (Bennett et al.)

Chapter 10 Planetary Atmospheres Section 10.1 1) Which of the following worlds has the most substantial atmosphere?

A) Mercury B) Venus C) the Moon D) Mars E) Earth Answer: B 2) Which of the following planets has the least substantial atmosphere?

A) Venus B) Earth C) Mars D) Neptune E) Mercury Answer: E 3) A planet with a higher reflectivity will do which of the following?

A) reflect more light and absorb less light B) reflect less light and absorb more light C) emit more light D) emit higher energy light E) transmit more light Answer: A 4) What would happen to Earth's temperature if you painted the entire surface of the Earth black?

A) Its average temperature would go up.

B) Its average temperature would go down.

C) Its temperature would not change.

Answer: A 5) What would happen to Earth's temperature if you painted the entire surface of the Earth white?

A) Its temperature would not change.

B) Its average temperature would go down.

C) Its average temperature would go up.

Answer: B

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6) Which terrestrial world has the highest average surface temperature? A) Mercury B) Venus C) the Moon D) Mars E) Earth Answer: B 7) Which terrestrial world has the greatest difference in temperature between its "no greenhouse" temperature and its actual temperature? A) Mercury B) Venus C) Earth D) the Moon E) Mars Answer: B 8) Why does Venus have such a great difference in temperature between its "no greenhouse" temperature and its actual temperature? A) It has a slow rotation. B) It is so close to the Sun. C) It has a large amount of carbon dioxide in its atmosphere. D) It has a high level of volcanic activity. E) It has no cooling effects from oceans. Answer: C 9) Venus has a higher average surface temperature than Mercury. Why? A) because its surface is covered with hot lava from numerous active volcanoes B) because its slow rotation gives it more time to heat up in sunlight C) because it is closer to the Sun D) because its surface is heated by an extreme greenhouse effect Answer: D 10) Which terrestrial world experiences the greatest change between its daytime temperature and night temperature? A) Mercury B) Venus C) Earth D) Mars E) the Moon Answer: A

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11) If you were all powerful, how could you make the difference between a planet's night and day temperatures larger?

A) Increase the greenhouse gas content of the planet's atmosphere.

B) Increase the tilt of the planet's rotation axis.

C) Make the planet rotate more slowly.

D) Increase the number of impact craters on the planet.

Answer: C 12) Rank these planets in order of the strength of the greenhouse effect on the planet, from the weakest to the strongest greenhouse effect.

A) Mars, Mercury, Earth, Venus B) Mercury, Venus, Earth, Mars C) Mercury, Earth, Mars, Venus D) Mercury, Mars, Earth, Venus E) Mars, Earth, Venus, Mercury Answer: D 13) What are greenhouse gases?

A) gases that absorb visible light B) gases that absorb ultraviolet light C) gases that absorb infrared light D) gases that emit visible light E) gases that transmit infrared light Answer: C 14) How does the greenhouse effect work?

A) Greenhouse gases transmit visible light, allowing it to heat the surface, but then absorb infrared light emitted by the surface, trapping the heat near the surface.

B) The higher pressure of an atmosphere at lower altitudes traps heat more effectively.

C) Greenhouse gases are ionized by sunlight, making them heat up their surroundings.

D) Greenhouse gases absorb x-rays and ultraviolet light from the Sun, which then heat the atmosphere and the surface.

E) Greenhouse gases absorb infrared light from the Sun, which then heats the atmosphere and the surface.

Answer: A 15) Why does increasing the amount a greenhouse gas increase the temperature of a planet?

A) More greenhouse gas means that air molecules are heavier on average.

B) More greenhouse gas means more absorption of visible light from the Sun. C) More greenhouse gas means higher atmospheric pressure.

D) More greenhouse gas means more absorption of infrared light emitted by the planet.

Answer: D

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16) Of the four gases CO2, H2O, N2, and O2, which are greenhouse gases? A) Only CO2 B) CO2 and H2O C) CO2 and N2 D) all except O2 E) all four Answer: B 17) Which of the following is NOT a greenhouse gas?

A) water (H2O) B) molecular oxygen (O2) C) carbon dioxide (CO2) D) methane (CH4) Answer: B 18) What would Earth's average surface temperature be if it had no greenhouse effect?

A) below the freezing point of water B) slightly above the freezing point of water C) about 10°C D) the same temperature as it is with the greenhouse effect E) slightly warmer than it is with the greenhouse effect Answer: A 19) By about how much does the greenhouse effect change the temperature of Earth?

A) 30 K B) 5 K C) −16 K D) 500 K Answer: A 20) What kind of thermal radiation does Earth emit?

A) infrared light B) visible and ultraviolet light C) infrared and visible light D) infrared, visible, and ultraviolet light E) visible light Answer: A 21) Earth's stratosphere is heated primarily by which process?

A) convection from the Earth's surface B) absorption of infrared light by greenhouse gases C) absorption of visible light by ozone D) absorption of ultraviolet light by ozone E) absorption of infrared sunlight Answer: D 4 Copyright © 2020 Pearson Education, Inc.

22) Which of the following gases absorbs ultraviolet light best? A) carbon dioxide B) nitrogen (N2) C) the oxygen we breathe (O2) D) hydrogen E) ozone (O3) Answer: E 23) X-rays from the Sun's corona A) are absorbed in Earth's troposphere.

B) are absorbed in Earth's thermosphere.

C) cause meteor showers.

D) break apart ozone in the stratosphere.

E) generally reach Earth's surface.

Answer: B 24) Which of the following lists the layers of a generic planetary atmosphere in the correct order from lowest to highest altitude?

A) troposphere, stratosphere, exosphere, thermosphere B) thermosphere, troposphere, stratosphere, exosphere C) stratosphere, troposphere, exosphere, thermosphere D) stratosphere, thermosphere, troposphere, exosphere E) exosphere, troposphere, stratosphere, thermosphere Answer: B 25) What is the exosphere?

A) the lowest layer in the atmosphere B) the part of the atmosphere that absorbs optical light C) the part of the atmosphere that absorbs ultraviolet D) the part of the atmosphere in which the greenhouse effect is strongest E) the outermost, very low-density region of the atmosphere Answer: E 26) What is the thermosphere?

A) the lowest layer in the atmosphere B) the part of the atmosphere that absorbs optical light C) the part of the atmosphere that absorbs ultraviolet D) the part of the atmosphere that absorbs x-rays Answer: D 27) What is a stratosphere?

A) a lowest layer in the atmosphere B) a part of the atmosphere that absorbs optical light C) a part of the atmosphere that absorbs ultraviolet light D) a part of the atmosphere that absorbs x-rays E) the highest layer in an atmosphere Answer: C 5 Copyright © 2020 Pearson Education, Inc.

28) Which is true of the troposphere on Earth? A) It is the lowest layer in the atmosphere, in which convection occurs. B) It is the region of the atmosphere that absorbs ultraviolet light from the Sun. C) It is the region of the atmosphere that absorbs x-rays from the Sun. D) It is the highest layer in the atmosphere, marking the boundary with space. Answer: A 29) Which of the following planets has a stratosphere? A) Mercury B) Venus C) Earth D) Mars E) all of the above Answer: C 30) Why doesn't Mars have a stratosphere? A) It is too far from the Sun. B) Its atmosphere does not contain enough of an ultraviolet-absorbing gas. C) Its atmosphere does not contain enough greenhouse gases. D) It is too small in size. E) It lacks a strong enough magnetic field. Answer: B 31) Why is a planet's thermosphere warm? A) It absorbs x-rays. B) It absorbs infrared light. C) It absorbs visible light. D) It contains greenhouse gases. E) It absorbs ultraviolet light. Answer: A 32) In which layer of Earth's atmosphere is ultraviolet light absorbed? A) exosphere B) thermosphere C) stratosphere D) troposphere Answer: C 33) What is the ionosphere? A) a layer of the atmosphere that is above the exosphere B) a layer of the atmosphere characterized by the presence of ozone C) a portion of the thermosphere in which the gas is ionized D) a portion of the troposphere in which ions are common Answer: C

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34) Why is the sky blue? A) Air molecules scatter blue light more effectively than red light.

B) The gases in Earth's atmosphere emit blue light. C) The Sun mainly emits blue light. D) The atmosphere transmits mostly blue light. E) Because of the way light is reflected off of the oceans. Answer: A 35) Why are sunsets and sunrises red? A) The Sun emits more red light when it's near the horizon. B) Sunlight must pass through more atmosphere to reach our eyes at those times, so more blue light is scattered away. C) Sunlight must pass through more atmosphere to reach our eyes at those times, which means it passes through a larger volume of red air molecules. D) The lower temperatures of morning and evening (compared to midday) make the sky redder in color. Answer: B 36) Why does convection occur in the troposphere, but not in the stratosphere? A) The troposphere is warmer than the stratosphere. B) The troposphere is cooler than the stratosphere. C) Temperature decreases with altitude in the troposphere, but this trend reverses in the stratosphere. D) Density decreases with altitude in the troposphere, but this trend reverses in the stratosphere. E) The troposphere contains a smaller proportion of greenhouse gases than the stratosphere. Answer: C Section 10.2 1) What is the difference in meaning between the terms weather and climate? A) Weather refers to local conditions, and climate refers to global conditions. B) Weather refers to short-term variations in conditions, and climate refers to the average of weather over many years. C) Weather refers to small storms, and climate refers to large storms. D) Weather refers to wind and rain, and climate refers to processes like convection. E) Weather refers to day-by-day changes in conditions, and climate refers to seasonal changes in weather. Answer: B 2) How is the atmosphere of a planet affected by the rotation rate? A) The rotation rate determines how much atmosphere a planet has. B) The rotation rate determines how long the planet is able to retain its atmosphere. C) Faster rotation rates raise surface temperatures and thus determine how much material is gaseous versus icy or liquid. D) Faster rotation rates raise the atmospheric temperature. E) Faster rotation rates produce stronger winds. Answer: E

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3) What most strongly affects the strength of a planet's Coriolis effect?

A) a planet's distance from the Sun B) the amount of greenhouse gases in the atmosphere C) a planet's size and rotation rate D) a planet's size and temperature E) the tilt of a planet's axis Answer: C 4) Which of the following would lead to a warmer temperature for a planet?

A) a decrease in the planet's reflectivity B) a decrease in the planet's amount of greenhouse gases C) a decrease in the brightness of the Sun D) a decrease in the number of volcanic eruptions on the planet Answer: A 5) If the tilt of Earth's rotation axis was increased from 23.5° to 40°, what would we expect to change?

A) Seasons on Earth would become more extreme (hotter summers, colder winters).

B) Seasons on Earth would become less extreme (cooler summers, warmer winters).

C) The Earth would not experience seasons anymore.

D) Nothing would change about weather on Earth.

Answer: A 6) Which of the following is the Sun predicted to do in the future based on theoretical models and observations of other stars?

A) The Sun will gradually get brighter over time.

B) The Sun will gradually get dimmer over time.

C) The Sun will maintain the same brightness during its entire lifetime.

D) The Sun will gradually rotate faster.

E) The Sun will get gradually closer to the Earth.

Answer: A Section 10.3 1) Mercury's small amount of atmospheric gas comes from A) volcanic outgassing.

B) evaporation of liquid from the surface.

C) the melting of rocks heated by the Sun. D) surface ejection caused by micrometeorites and high-energy particles and photons.

E) seepage of gases trapped in its core.

Answer: D

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2) In what form does water exist on the Moon? A) There is water ice in craters near the poles. B) There are small pools of liquid water just beneath the surface. C) There are shallow lakes of liquid water in the deepest craters. D) There is water ice in the bright regions of the lunar maria. E) There is no water in any form on the Moon. Answer: A Section 10.4 1) How might Mars's weakened magnetic field have allowed for major changes in its climate? A) Atmospheric gases were left vulnerable to being stripped into space by solar wind particles. B) The heat combined with the magnetic field and disappeared with it. C) Mars has actually heated up since the magnetic field weakened, since the solar rays no longer have such a dense layer to get through. D) They are completely unrelated; there is no possible influence. Answer: A 2) Which of these observations helped test the idea that Mars' atmosphere thinned due to interactions with the solar wind? A) The MAVEN orbiter measured present-day gas loss from Mars' atmosphere. B) The Curiosity rover measured the carbon content of rocks on Mars' surface. C) Astronomers used spectrographs on the Keck telescope to measure the density of Mars' atmosphere. D) Geologists measured the carbon content of Martian rocks that were transported to Earth by asteroid impacts.

Answer: A 3) Suppose that Mars were located at the same distance from the Sun as Earth, but was otherwise the same. Would it still be colder than Earth? Why or why not? A) yes, because Mars has fewer clouds than Earth B) yes, because Mars has a much weaker greenhouse effect than Earth C) yes, because Mars has less gravity than the Earth D) no, because with the same distance from the Sun, the two planets would have the same temperature Answer: B 4) Why does Mars have more extreme seasons than Earth? A) because it is farther from the Sun B) because it has a larger axis tilt C) because it has a more elliptical orbit D) because it has more carbon dioxide in its atmosphere Answer: C

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5) Where is most of the water that Mars has today? A) as water vapor in its clouds B) frozen in its polar caps and in subsurface ground ice C) frozen on the peaks of its tall volcanoes D) in subsurface lakes of liquid water E) deeply buried in its core and mantle Answer: B 6) Why is Mars red? A) It is made primarily of the red rock known as reddite. B) Its surface rocks were rusted by oxygen. C) Its atmosphere scatters blue light more effectively than red light. D) Its surface is made of ices that absorb blue light. E) Its surface is made of ices that absorb red light. Answer: B 7) All the following statements about Mars are true. Which one might be the cause of a significant loss of atmospheric gas to space? A) The rock on Mars is probably red because of chemical reactions with oxygen that had been released into the atmosphere through the outgassing of water molecules.

B) Mars lost its global magnetic field, leaving the atmosphere vulnerable to the solar wind.

C) The axis tilt of Mars is thought to change significantly with time. D) Mars probably once had a much higher density of greenhouse gases in its atmosphere than it does today.

Answer: B Section 10.5 1) Why does Earth's atmosphere contain much less carbon dioxide than Venus's atmosphere? A) Earth's volcanoes did not outgas as much carbon dioxide as those on Venus. B) Most of Earth's carbon dioxide was lost to space during the heavy bombardment. C) Chemical reactions with other gases destroyed the carbon dioxide and replaced it with the nitrogen that is in the atmosphere now. D) Most of Earth's carbon dioxide dissolved in the oceans, where it became incorporated into carbonate rocks. E) Earth formed farther from the Sun, and there was less carbon dioxide at great distances in the solar nebula. Answer: D 2) Venus has a high reflectivity because of its A) light-colored rocks. B) snow. C) clouds. D) dust storms. E) volcanic ash. Answer: C

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3) Venus is much hotter than the Earth. Which of the following explains most of this temperature difference?

A) Venus has much more carbon dioxide in its atmosphere.

B) Venus's clouds have a very high reflectivity.

C) Venus rotates backward compared to its orbital rotation.

D) The sunlight reaching Venus is more concentrated because of its closer distance to the Sun. Answer: A 4) All of the statements below are true. Which one gives the primary reason why the surface of Venus today is some 450°C hotter than the surface of Earth?

A) Venus is only about 73 percent as far from the Sun as Earth.

B) Venus has a much stronger greenhouse effect than Earth.

C) Venus has a much higher reflectivity than Earth.

D) Venus has a higher atmospheric pressure than Earth.

Answer: B 5) Why doesn't Venus have seasons?

A) It does not have an ozone layer.

B) It is too close to the Sun. C) Its rotation axis is nearly perpendicular to its orbital plane.

D) It does not rotate fast enough.

Answer: C 6) Which of the following best describes rain on Venus?

A) It does not have rain.

B) It has sulfuric acid rain that causes erosion on the surface.

C) It has sulfuric acid rain in its atmosphere, but the drops evaporate before hitting the surface.

D) It has liquid water rain that causes erosion on the surface.

Answer: C 7) Venus may have started with an ocean's worth of water. If so, where is its water now?

A) The original water remains vaporized in the atmosphere due to Venus's intense heat.

B) Most of the water is frozen beneath the surface.

C) Most of the water combined with rocks in chemical reactions.

D) The water was lost when ultraviolet light broke apart water molecules and the hydrogen escaped to space.

E) The water changed to carbon dioxide through chemical reactions.

Answer: D 8) Deuterium is more abundant on Venus than elsewhere in the solar system. What do we think this fact tells us about Venus?

A) It was formed in a part of the solar nebula where deuterium condensed easily.

B) It was formed in a part of the solar nebula where deuterium was surprisingly abundant.

C) It once had a substantial amount of water in its atmosphere.

D) It once had an atmosphere made mostly of hydrogen.

E) Its volcanoes outgassed primarily carbon dioxide and deuterium, but little water.

Answer: C

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9) What is deuterium? A) an isotope of hydrogen with one neutron B) an isotope of hydrogen with two protons C) a molecule made from two hydrogen atoms D) a molecule of water with three hydrogen atoms E) an isotope of hydrogen with a heavier than average proton Answer: A Section 10.6 1) Which of the following can act like a long-term "thermostat" that helps keep Earth's average temperature fairly stable?

A) radioactive elements trapped in the Earth's mantle B) heat stored in the Earth's magnetosphere C) heat stored in the Earth's liquid core D) the carbon dioxide cycle that moves carbon dioxide between Earth's atmosphere, oceans, and rock Answer: D 2) Considering just the effects of the carbon dioxide cycle, if the Earth were to warm up a bit, what would happen?

A) More evaporation and rainfall would reduce the atmospheric CO2 levels, and the greenhouse effect would weaken.

B) More evaporation and rainfall would increase the atmospheric CO2 levels, and the greenhouse effect would strengthen.

C) Carbonate materials would form in the oceans more rapidly, the atmospheric CO2 content would decrease, and the greenhouse effect would strengthen.

D) There would be a runaway greenhouse effect, with the Earth becoming ever hotter until the oceans evaporated (as may have happened on Venus).

E) The ice caps would melt and cool the Earth back to its normal temperature.

Answer: A 3) Earth has gone in and out of numerous ice ages over the past couple million years.

Which of the following was generally true during all those ice ages?

A) The atmospheric carbon dioxide concentration was much higher than it is today.

B) The atmospheric carbon dioxide concentration was much lower than it is today.

C) The continents were closer together than they are today.

D) The continents were farther apart than they are today.

E) There were much larger mammals than there 12 are today.

Answer: B Copyright © 2020 Pearson Education, Inc.

4) Geological evidence points to a few very deep "snowball" phases in Earth's history, in which the oceans would have been mostly frozen. How did Earth recover from a snowball phase?

A) The increased ice coverage on Earth's surface absorbed more sunlight than water and rocks, thus gradually heating Earth until the ice melted.

B) Life vanished, leading to an increase in CO2, and increased global warming, eventually melting the ice.

C) Volcanoes continued to inject CO2 into Earth's atmosphere, increasing the greenhouse effect to the point where ice melted.

D) Plate tectonics gradually subducted all the ice below Earth's surface.

E) As the Sun aged, it grew brighter and increased Earth's temperature, melting the ice.

Answer: C 5) Global warming is causing Earth to have less total sea ice. This, in turn, causes A) Earth to absorb more total sunlight, heating our planet even more.

B) Earth to reflect more sunlight, counteracting the effects of global warming.

C) Earth's oceans to get heavier, lowering sea level.

Answer: B 6) Where did the molecular oxygen in Earth's atmosphere come from?

A) photosynthesis by living organisms B) the breakdown of water molecules by sunlight C) outgassing from volcanoes D) evaporation from the oceans E) chemical reactions with surface rocks Answer: B 7) Which of the following is an expected consequence of global warming?

A) more extreme weather events, including extreme winter storms B) ocean water becoming more acidic C) an increase in sea level D) reduced ice coverage in the Arctic Ocean E) All of the above are expected consequences of global warming.

Answer: B 8) Why does the burning of fossil fuels increase the greenhouse effect on Earth?

A) The heat from the flames warms the planet.

B) Burning fossil fuels releases carbon dioxide into the atmosphere.

C) Burning fossil fuels depletes the amount of ozone, thereby warming the planet.

D) Burning fossil fuels produces infrared light, which is then trapped by existing greenhouse gases.

Answer: B

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9) Climate models support the claim that human activity is causing the currently observed global warming because A) the models can perfectly predict all aspects of today's climate.

B) climate models that include contributions by human activity agree much better with actual data than models that consider only natural factors.

C) the models are very sophisticated, with thousands of equations, and this gives scientists confidence that the models must be correct.

D) the models predict that warming will continue in the future.

Answer: B 10) Which of the following describes the most convincing evidence in support of the idea that human activity is causing climate change on Earth?

A) Polls show that a majority of Americans agree that this is the case.

B) The vast majority of scientists say so.

C) The known science behind the greenhouse effect predicts that warming should be occurring as the carbon dioxide concentration rises, and the average temperature is rising as expected.

D) There is no other known process besides the burning of fossil fuels that can lead to any change in Earth's average temperature.

Answer: C 11) The Sun is gradually increasing in brightness as it ages. Why isn't this considered to be an explanation for global warming?

A) A change in the Sun's brightness would not be expected to have any effect on Earth's average temperature.

B) The scientists are covering up this potentially valid explanation.

C) The amount of energy the Earth receives from the Sun remains constant regardless of what the Sun does.

D) The Sun is increasing in brightness much too slowly to be causing the current warming.

Answer: D 12) All of the following statements are true. Which one provides strong observational support for the claim that greenhouse gases make a planet warmer than it would be otherwise?

A) Venus has a higher average temperature than Mercury.

B) Earth is the only planet with an ozone layer in its atmosphere.

C) Earth has a higher average temperature than Mars.

D) Mercury is much hotter than the Moon.

Answer: A 13) If the amount of polar ice decreases, what would happen, and why?

A) cooling, because melted ice cools things off B) warming, because more sunlight is reflected C) cooling, because more sunlight is reflected D) warming, because more sunlight is absorbed Answer: D

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14) Given the rate at which human activity is increasing atmospheric carbon dioxide levels, why can't we expect the natural carbon dioxide cycle to prevent global warming?

A) It operates too slowly.

B) It only affects the rate at which carbon dioxide circulates within the atmosphere, not the total amount of carbon dioxide in the atmosphere.

C) The natural carbon dioxide cycle no longer operates.

D) The carbon dioxide cycle can only affect natural carbon dioxide, not the carbon dioxide released through human activity.

Answer: A 15) In the greenhouse effect, what is the direct cause of extra heating of the Earth's surface?

A) Additional carbon dioxide makes the atmosphere more transparent to infrared light, allowing the sun to more directly heat the surface.

B) Additional carbon dioxide makes the atmosphere more opaque to infrared light, trapping more of the infrared light emitted by Earth.

C) Additional carbon dioxide makes the atmosphere more dense, so heat passes through it more slowly.

D) Additional carbon dioxide makes the atmosphere emit more infrared light which gets trapped near the surface of the Earth.

Answer: B

16) Refer to the figure above. What can you conclude from the data shown on this graph alone?

A) The carbon dioxide concentration varies naturally, but is much higher today than it has been in the past 800,000 years.

B) Human activity has caused the carbon dioxide concentration to rise and fall many times in the past 800,000 years.

C) Changes in the carbon dioxide concentration are the causes of ice ages.

D) If current trends continue, carbon dioxide will soon be the most abundant gas in Earth's atmosphere.

Answer: A

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17) Refer to the figure above. Today's carbon dioxide concentration is about ________ that at any other time in the past 800,000 years.

A) 2 % higher than B) 45% higher than C) double D) 400 times Answer: B General Chapter Questions 1) Which of the following statements about the greenhouse effect is true?

A) Without the naturally occurring greenhouse effect, Earth would be too cold to have liquid oceans.

B) A weak greenhouse effect operates on Mars.

C) The burning of fossil fuels increases the greenhouse effect on Earth because of the release of carbon dioxide.

D) One result of an increased greenhouse effect on Earth may be an increased number of severe storms.

E) All of the above are true.

Answer: E 2) In science, "positive feedback" is a term that applies to A) a process undergoing a self-reinforcing cycle that amplifies some initial effect.

B) commentary that reflects a high opinion of a scientist's work.

C) feedback that has a positive electrical charge.

D) a process that can only continue as long as most scientists continue to support it.

Answer: A 3) In what ways is Earth different from the other terrestrial planets?

A) Its lithosphere is broken into plates that move around.

B) It has a much higher percentage of oxygen in its atmosphere.

C) Most of its surface is covered with liquid water.

D) Life can be found almost everywhere on its surface.

E) All of the above are true.

Answer: E 4) Mars' atmosphere is mostly carbon dioxide. Why does it not experience a runaway greenhouse effect like Venus?

A) Mars is protected by its magnetic field.

B) Mars does not have enough additional water vapor to magnify the warming.

C) Mars' atmosphere is too thin.

D) Mars has a CO2 cycle like Earth that regulates the amount of carbon dioxide.

Answer: C

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5) Which of the following gases in Earth's atmosphere is not primarily a product of volcanic outgassing?

A) water (H2O) B) nitrogen (N2) C) oxygen (O2) D) carbon dioxide (CO2) Answer: C Short Answer Questions 1) Earth and Venus both presumably had similar gases outgassed from their volcanoes.

Briefly explain how their atmospheres ended up so different.

Answer: On Venus, water and carbon dioxide remained in the atmosphere. Over time, ultraviolet light split the water molecules and the hydrogen escaped to space. Thus, Venus has no

more water today and an atmosphere thick with carbon dioxide. On Earth, water condensed to rain now and eventually formed the oceans. Carbon dioxide was absorbed in the oceans and is

locked up in carbonate rocks. Thus, most of the water on Earth remains in the oceans, and most of the carbon dioxide is in rocks, leaving a much thinner atmosphere than that of Venus.

2) Why did Earth retain most of its water while Venus and Mars lost theirs?

Answer: liquid. The basic answer is that Earth was at just the right distance to retain water as Venus lost its water because it was too hot. At its closer proximity to the Sun, Venus was warm enough to keep all its water in gaseous form in the atmosphere. When the runaway greenhouse effect became prominent, Venus became even warmer and the water vapor escaped into

space.

Mars was far enough from the Sun that it was cold enough for the water vapor to freeze out of the atmosphere, resulting in thick polar caps.

3) Why does Earth have so little carbon dioxide in its atmosphere, when Earth should have outgassed about as much of it as Venus?

Answer: The answer to this question is that Earth has oceans. Carbon dioxide can dissolve in water, and the oceans actually contain much more carbon dioxide than the atmosphere.

However,

most of the carbon dioxide is locked up in rocks on the seafloor. Rainfall erodes rocks on Earth's surface. These rocks react with dissolved carbon dioxide in the oceans to form carbonate minerals, which fall to the ocean floor.

4) Why does Earth have so much more oxygen (O2) than Venus or Mars?

17 Answer: The answer to this question is simply that Earth hasInc. life. Photosynthesis supplies Copyright © 2020 Pearson Education, oxygen to the atmosphere by converting CO2 to O2. Oxygen is removed from the atmosphere

5) Why does Earth have an ultraviolet-absorbing stratosphere, while Venus and Mars do not?

Answer: Life and oxygen also explain the presence of Earth's ultraviolet-absorbing stratosphere.

In the upper atmosphere, chemical reactions transformed some of the O2 into molecules of O3, ozone. The ozone molecule absorbs solar ultraviolet energy better than O2, creating the warm stratosphere. Since Mars and Venus lack photosynthetic life, they have too little O2 and too little ozone to form a stratosphere.

6) Briefly describe how human activity is affecting Earth's ozone layer.

Answer: Human-made chemicals called CFCs rise into the stratosphere, where they are split by ultraviolet light. The chlorine ions released in this way catalytically destroy ozone. Thus, human activity is depleting Earth's ozone layer. CFCs are now regulated, and the ozone layer is recovering.

Reading Quiz Questions 1) Briefly describe at least three likely consequences of continued human burning of fossil fuels adding to Earth's greenhouse effect.

Answer: Many possible answers: increased global average temperature; increase in sea level; more severe storms; climate change that causes more species extinction.

2) Which of the following correctly lists the terrestrial worlds in order from the most atmospheric gas to the least? (Mercury and the Moon are listed together since their atmospheres have very similar amounts of gas.)

A) Venus, Earth, Mars, Mercury/Moon B) Earth, Venus, Mars, Mercury/Moon C) Mars, Venus, Earth, Mercury/Moon D) Venus, Mars, Mercury/Moon, Earth Answer: A 3) Which planet(s) have an atmosphere that consists mostly of carbon dioxide?

A) Venus and Mars B) Venus, Earth, and Mars C) Venus only D) Mars only Answer: A 4) Suppose we represent Earth with a basketball. On this scale, most of the air in Earth's atmosphere would fit in a layer that is A) about the thickness of a sheet of paper.

B) about an inch thick.

C) about 6 inches thick.

D) about a half-inch thick.

Answer: A

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5) Why does atmospheric pressure decrease as you go higher in altitude on Earth? A) The weight of the atmosphere above you decreases with altitude. B) Gravity gets much weaker with altitude. C) Temperature decreases with altitude and lower temperature tends to mean lower pressure. D) There are fewer greenhouse gases at higher altitude.

Answer: A 6) In the context of a planetary atmosphere, what is a bar?

A) a unit of pressure roughly equal to the atmospheric pressure at sea level on Earth B) the surface pressure on any planet C) a description of the atmospheric composition on Earth D) a place where planetary scientists can get sodas and other drinks Answer: A 7) Which of the following is the most basic definition of a greenhouse gas?

A) a gas that absorbs infrared light B) a gas that makes a planet much hotter than it would be otherwise, even in small amounts C) a gas that keeps warms air from rising, and therefore warms the surface D) a gas that reflects a lot of sunlight Answer: A 8) Which of the following is not a greenhouse gas?

A) oxygen (O2) B) carbon dioxide (CO2) C) methane (CH4) D) water vapor (H2O) Answer: A 9) If Earth's atmosphere had no greenhouse gases, then Earth's average surface temperature would be A) well below the freezing point of water.

B) about the same as it is now.

C) slightly cooler, but still above freezing.

D) slightly warmer, but still well below the boiling point of water.

Answer: A 10) Which of the following correctly lists the layers of Earth's atmosphere from the ground upward?

A) troposphere, stratosphere, thermosphere, exosphere B) thermosphere, stratosphere, troposphere, exosphere C) exosphere, stratosphere, thermosphere, troposphere D) troposphere, thermosphere, stratosphere, exosphere Answer: A 19 Copyright © 2020 Pearson Education, Inc.

11) Why is the sky blue (on Earth)?

A) because molecules scatter blue light more effectively than red light B) because the Sun emits mostly blue light C) because molecules scatter red light more effectively than blue light D) because deep space is blue in color E) No one knows; this is one of the great mysteries of science.

Answer: A 12) Which of the following general statements about light and Earth's atmosphere is not true?

A) Visible light from the Sun is absorbed in the exosphere.

B) X-rays from the Sun are absorbed in the thermosphere.

C) Ultraviolet from the Sun is absorbed primarily in the stratosphere.

D) Infrared light emitted by Earth itself is absorbed primarily in the troposphere.

Answer: A 13) What is a magnetosphere?

A) a region of space around a planet in which the planet's magnetic field can trap charged particles B) the layer of a planet in which its magnetic field is generated C) the uppermost layer of any planetary atmosphere D) the region in a planet's atmosphere in which auroras occur Answer: A 14) What is the difference between weather and climate?

A) Weather refers to short-term changes in wind, rain, and temperature; climate refers to the long-term average of weather.

B) Weather refers to atmospheric conditions in the troposphere; climate refers to atmospheric conditions in the stratosphere.

C) Weather is something that we can control, and climate is not.

D) Weather refers to small storms; climate refers to large storms.

Answer: A 15) Which of the following describes a primary role of global circulation cells in a planet's atmosphere?

A) They transport heat from the equator toward the poles.

B) They create severe weather such as thunderstorms.

C) They cause air to be diverted into hurricane-like swirls.

D) They keep the poles cold enough to have polar caps.

Answer: A 16) What change in the Sun during the solar system's history is thought to be important to understanding the climates of Venus, Earth, and Mars?

A) a gradual brightening with time B) a gradual dimming with time C) a gradual weakening of the solar wind with time D) a gradual reduction in the amount of ultraviolet and x-ray radiation coming from the Sun Answer: A

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17) Which of the following best describes the nature and origin of the atmospheres of the Moon and Mercury?

A) They have thin exospheres only, with gas coming from impacts of subatomic particles and photons.

B) They have thin tropospheres only, with gas coming from vaporization.

C) They have only small amounts of gas, all of which is left over from outgassing long ago.

D) They have thin atmospheres produced by outgassing, but still have the layers of a troposphere, thermosphere, and exosphere.

Answer: A 18) Why is Mars red?

A) Chemical reactions between surface rock and atmospheric oxygen literally rusted the surface.

B) Martian volcanoes released a much redder lava than volcanoes on Earth.

C) The red color of Mars is a result of the scattering of light in the Martian sky.

D) The red color is caused by water ice chemically bound in surface rock.

Answer: A 19) Scientists suspect that Mars once had abundant liquid water on its surface. For this to have been true, early Mars must have had ________ than Mars today.

A) a much higher atmospheric pressure and much stronger greenhouse effect B) a larger mass and radius C) a smaller axis tilt and less elliptical orbit D) larger polar caps and more dust storms Answer: A 20) What do we mean by a runaway greenhouse effect?

A) a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere B) a greenhouse effect that starts on a planet but later disappears as gases are lost to space C) a greenhouse effect that heats a planet so much that its surface rock melts D) a process that heats a planet's surface, but that doesn't require the presence of greenhouse gases Answer: A 21) Which of the following describes a fundamental difference between Earth's climate history and the climate histories of Venus and Mars?

A) Earth's climate has remained relatively steady throughout our planet's history.

B) Earth got a lot of atmospheric gas from outgassing by volcanoes.

C) Earth had enough water to form oceans in its early history.

D) Earth's climate can be affected by changes in its axis tilt.

Answer: A

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22) Which of the following statements about ozone (in Earth's stratosphere) is not true?

A) The presence of ozone was crucial to the origin of life some 4 billion years ago.

B) Ozone is a form of oxygen.

C) Ozone absorbs harmful ultraviolet light from the Sun. D) Without this ozone, Earth would not have a stratosphere.

Answer: A 23) How did molecular oxygen (O2) get into Earth's atmosphere?

A) It was released by life through the process of photosynthesis.

B) It was captured from the solar nebula.

C) It was outgassed from volcanoes.

D) It came from chemical reactions with surface rocks.

Answer: A 24) What is the importance of the carbon dioxide (CO2) cycle?

A) It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.

B) It makes the growth of continents possible.

C) It allows for an ultraviolet-absorbing stratosphere.

D) It will prevent us from suffering any consequences from global warming.

Answer: A 25) In the context of Earth's climate history, what do we mean by snowball Earth?

A) It refers to one or more deep ice ages that occurred hundreds of millions of years ago.

B) This term is used to describe all the ice ages that have occurred in the past few million years.

C) It refers to a time when polar regions had much more snowfall than normal.

D) It is what we expect to see happen on Earth in about a billion years.

Answer: A 26) Earth has been gradually warming in recent decades, and very strong evidence indicates that the cause of this warming is A) human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere.

B) the increase in forest fires during recent years.

C) a gradual brightening of the Sun. D) the fact that our politicians spout a lot of hot air.

Answer: A Concept Quiz Questions 1) Which of the following general statements about Earth's atmosphere is not true?

A) The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.

B) Atmospheric pressure decreases with altitude.

C) Even in low-Earth orbit, some atmospheric gas is still present.

D) Atmospheric scattering of light explains why our daytime sky is bright and blue.

Answer: A

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2) Suppose that Earth's ice caps melted, but everything else about the Earth's surface and atmosphere stayed the same. What would happen to Earth's average surface temperature?

A) The surface temperature would increase.

B) The temperature would not be affected at all.

C) The surface temperature would decrease.

D) The surface temperature would change radically, until it was equal to the melting temperature of ice.

Answer: A 3) Which of the following best describes how the greenhouse effect works?

A) A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.

B) Greenhouse gases absorb X rays and ultraviolet light from the Sun, and this absorbed radiation then heats the atmosphere and the surface.

C) Greenhouse gases absorb infrared light coming from the Sun, and this absorbed sunlight heats the lower atmosphere and the surface.

D) The greenhouse effect is caused primarily by ozone, which absorbs ultraviolet light and thereby makes the atmosphere much hotter than it would be otherwise.

Answer: A 4) All the statements are true. Which one gives the primary reason why the surface of Venus today is some 450ºC hotter than the surface of Earth?

A) Venus has a much stronger greenhouse effect than Earth.

B) Venus is only about 73% as far from the Sun as Earth.

C) Venus has a much higher reflectivity than Earth.

D) Venus has a higher atmospheric pressure than Earth.

Answer: A 5) Which of the following statements about Earth's troposphere is not generally true?

A) It is the layer of the atmosphere in which ozone absorbs dangerous ultraviolet light from the Sun. B) It is the lowest layer of the atmosphere.

C) It is the layer of the atmosphere in which convection plays the most important role.

D) It is a layer of the atmosphere in which temperature declines with increasing altitude.

Answer: A 6) In general terms, how do the temperature structures of the atmospheres of Venus and Mars differ from that of Earth?

A) They lack ultraviolet-absorbing stratospheres.

B) They lack X-ray absorbing thermospheres.

C) Their atmospheres are similar in structure to Earth's but with much higher temperatures.

D) Temperatures in their tropospheres increase with altitude, rather than decreasing with altitude.

Answer: A

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7) Does Venus have auroras around its poles, like Earth? Why or why not?

A) no, because it lacks a global magnetic field B) yes, because it is bombarded by charged particles from the Sun C) no, because its atmosphere is too thick D) yes, because strong winds generate light near its poles Answer: A 8) All the following statements are true. Which one explains why convection can occur in the troposphere but not in the stratosphere?

A) Temperature declines with altitude in the troposphere but increases with altitude in the stratosphere.

B) Atmospheric pressure is much greater in the troposphere than in the stratosphere.

C) The stratosphere contains significant amounts of ozone but the troposphere does not.

D) Clouds tend to form in the troposphere but not the stratosphere.

Answer: A 9) Which of the following is not caused by the Coriolis effect on Earth?

A) Water going down a drain swirls in opposite directions in the Northern and Southern hemispheres.

B) Earth's global circulation cells are split into three separate cells in each hemisphere.

C) Hurricanes swirl in opposite directions in the Northern and Southern hemispheres.

D) Air or objects moving northward in the Northern Hemisphere are deflected to the east.

Answer: A 10) Why is the Coriolis effect so weak on Venus?

A) because Venus rotates so slowly B) because Venus is so hot C) because Venus has such a thick atmosphere D) because Venus has such a strong greenhouse effect Answer: A 11) All of the following have occurred over long periods of time on Earth. Which one is not thought to have played a major role in long-term changes in Earth's climate?

A) a gradual rise in the atmospheric content of oxygen B) changes in the Earth's axis tilt C) changes in the Earth's overall reflectivity D) changes in the atmospheric concentration of greenhouse gases Answer: A

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12) Which of the following is thought to explain why Venus has so much more atmospheric gas than Earth? A) Most of the gases that have been released from volcanoes on Earth later returned to the surface. B) Venus has gained much more gas through outgassing than has Earth. C) Because of its lack of magnetic field, Venus has been able to gain gas through the impacts of solar wind particles, while Earth has not gained gas in this way. D) Earth has lost much more gas to thermal escape than has Venus. Answer: A 13) Why is thermal escape of atmospheric gas much easier from the Moon than from Earth? A) because the Moon's gravity is so much weaker than Earth's B) because the Moon's average surface temperature is lower than Earth's C) because the Moon lacks a global magnetic field, while Earth has one D) Outgassing on the Moon releases gases with lower masses than does outgassing on Earth. Answer: A 14) Observations indicate that the Moon has water ice in craters near the poles. Where do scientists suspect this water came from? A) ice brought by comet impacts long ago B) ice supplied to the Moon by impacts that occurred within the past century or so C) the ice formed from the condensation of water released by outgassing on the Moon D) The Moon has significant amounts of water bonded in its crust, so some of this water fills the polar craters. Answer: A 15) All the following statements about Mars are true. Which one might have led to a significant loss of atmospheric gas to space? A) Mars lost any global magnetic field that it may once have had. B) The axis tilt of Mars is thought to change significantly with time. C) Outgassed water molecules are split apart, and the oxygen then reacts chemically with surface rock on Mars. D) Mars probably once had a much higher density of greenhouse gases in its atmosphere than it does today.

Answer: A 16) What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure? A) The atmosphere is too cold and thin for liquid water today, yet we see evidence of flowing water in the past. B) We think it for purely theoretical reasons, based on calculations showing that the Sun has brightened with time. C) The presence of inactive volcanoes on Mars tells us that there must once have been a lot of outgassing, and hence a thicker atmosphere. D) The fact that parts of Mars have a lot of craters tell us that Mars must once have been much warmer. Answer: A

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17) Which of the following best explains what scientists think happened to outgassed water vapor on Venus?

A) Ultraviolet light split the water molecules, and the hydrogen then escaped to space.

B) Water was removed from the atmosphere by chemical reactions with surface rock.

C) It is frozen as water ice in craters near the poles.

D) It turned into carbon dioxide by reacting with nitrogen in Venus's atmosphere.

Answer: A 18) What would happen to Earth if we somehow moved our planet to the orbit of Venus?

A) Earth would suffer a runaway greenhouse effect and become as hot as or hotter than Venus.

B) Temperatures would rise only slightly, but enough to melt the polar caps.

C) The fact that we have oceans would moderate the temperature change because of moving our planet, so temperature would hardly change at all.

D) Being so much closer to the Sun would almost immediately cause the surface of Earth to melt, and all our cities would then be destroyed by the hot lava.

Answer: A 19) Deuterium is much more abundant on Venus than Earth. What do scientists think this fact tells us about Venus?

A) that Venus has lost a tremendous amount of water as a result of molecules being split by ultraviolet light and the hydrogen escaping to space B) that Venus once had a much stronger magnetic field than it does today C) that the greenhouse effect on Venus must have been much weaker in the distant past D) that volcanoes on Venus did not outgas as much water as volcanoes on Earth Answer: A 20) Why does Earth have so little carbon dioxide in its atmosphere compared to Venus?

A) Earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate rocks rather than being free in the atmosphere.

B) Earth's volcanoes outgassed far less carbon dioxide than those on Venus.

C) Earth once had a lot of carbon dioxide, but it was lost to space during the heavy bombardment early in our solar system's history.

D) Chemical reactions turned Earth's carbon dioxide into nitrogen.

Answer: A 21) Which characteristic of Earth explains why Earth has the ozone necessary for an ultraviolet-absorbing stratosphere?

A) the existence of photosynthetic life B) the existence of plate tectonics C) the moderate surface temperature D) the existence of oceans Answer: A

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22) Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth? A) plate tectonics and liquid water oceans B) life and atmospheric oxygen C) life and active volcanism D) active volcanism and active tectonics Answer: A 23) Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal?

A) Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released greenhouse effect. by volcanism builds up in the atmosphere and strengthens the

B) Cooler temperatures cause volcanoes to become more active, so they release more carbon dioxide into the atmosphere than they do when temperatures are warmer.

C) Cooler temperatures allow carbon dioxide to form rain and rain out of the atmosphere.

D) Cooler temperatures mean more ice and more erosion, which somehow makes the planet

warm up.

Answer: A 24) According to current science, why didn't oxygen begin to accumulate in the atmosphere for more than a billion years after life appeared on the Earth?

A) Oxygen released by life was removed from the atmosphere by chemical reactions with surface rocks until the surface rock could absorb no more.

B) Early forms of animal life consumed the oxygen released by plants during the first billion years of life on Earth.

C) Early life did not release oxygen, and oxygen-releasing organisms didn't evolve for a billion years after the earliest life.

D) Oxygen released by life was removed from the atmosphere by dissolving in the ocean until the oceans could dissolve no more.

Answer: A 25) Which of the following correctly lists two key pieces of evidence that, together, indicate that we should expect human activity to cause global warming?

A) (1) Carbon dioxide tends to make planets warmer than they would be otherwise.

(2) Measurements demonstrate that human activity is raising the carbon dioxide concentration in the atmosphere.

B) (1) The carbon dioxide cycle regulates Earth's climate.

(2) Human activity has disrupted the carbon dioxide cycle.

C) (1) The burning of fossil fuels is a form of human activity.

(2) Human activity is always bad for the environment.

D) (1) We can learn about past climate from ice cores.

27 (2) Ice cores show that Earth naturally has cooler and warmer periods.

Copyright © 2020 Pearson Education, Inc. Answer: A

26) Which of the following is not an expected consequence of warming ? global A) The entire Earth will warm up by the same amount.

B) an increase in the number and/or severity of extreme weather events C) an increase in sea level D) a decrease in summer ice coverage of the Arctic Ocean Answer: A Visual Quiz Questions 1) What terrestrial world is shown in this visible-light photo?

A) Venus B) Earth C) Mercury D) Mars Answer: A 2) This photograph shows the Space Shuttle orbiting about 300 kilometers above Earth's surface.

What is the significance of the whitish glow around the Shuttle's tail?

A) It shows that Earth's atmosphere still exists, though thinly, at this altitude.

B) It shows that the Space Shuttle can cause auroras along its orbit.

C) It shows that the Shuttle was firing its engines at the time this photo was taken.

D) It shows that the Shuttle lights work in space as well as they work on the ground.

Answer: A

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3) What does this diagram represent?

A) the basic way in which the greenhouse effect works B) the carbon dioxide cycle C) the basic reason that our sky is blue D) the basic mechanism of the Coriolis effect Answer: A

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4) This diagram shows the temperature structure of Earth's atmosphere, and dashed lines separate different atmospheric regions. Which region is the troposphere?

A) Region 1 B) Region 2 C) Region 3 D) Region 4 Answer: A

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5) These four photos show features of Earth that change with time, some fast and some slow.

Which of these features is a direct result of the fact that Earth has a global magnetic field?

A)

B)

C)

D)

Answer: D

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6) This photograph shows a hurricane from space. Why does it have the clockwise swirl?

A) because of the Coriolis effect B) because it is a strong hurricane C) because it is in the Northern Hemisphere D) because of the greenhouse effect Answer: A 7) This diagram represents the carbon dioxide cycle. Which position in the diagram represents the part of the cycle in which carbon dioxide is turned into carbonate minerals and rock?

A) Position 1 B) Position 2 C) Position 3 D) Position 4 Answer: C

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8) This diagram shows Earth's atmospheric carbon dioxide concentration over the past few decades. What is the significance of the up and down wiggles?

A) They show seasonal variations in the concentration.

B) They show that the rise in carbon dioxide concentration is caused by human activity.

C) They show that the carbon dioxide concentration can vary randomly and by large amounts.

D) They show that there is a lot of noise in data that attempt to measure the carbon dioxide concentration.

Answer: A

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9) What does this figure tell us?

A) The current level of carbon dioxide in our atmosphere is higher than it has been at any time during the past 800,000 years.

B) Earth is now warmer than it has been at any time during the past 800,000 years.

C) The current level of carbon dioxide in our atmosphere can be attributed to natural changes in Earth's climate.

D) The level of carbon dioxide in our atmosphere changes randomly with time, so there is no way to predict how it will change during the next century.

E) The current level of carbon dioxide in the atmosphere and the global average temperature are both higher today than at any other time during the past 800,000 years.

Answer: A

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10) On this graph, the black curve represents actual temperature measurements, the red curve represents models of the climate that include human emissions of greenhouse gases, and the blue curve represents models of the climate that include only natural factors but do not include human emissions of greenhouse gases. What is the key message that can be read from this graph?

A) Models support the conclusion that human emissions are driving global warming.

B) Different climate models give different predictions about how much global warming should be occurring.

C) Climate models can successfully reproduce Earth's climate for the first half of the 20th century, but after that, they are unable to account for actual temperature data.

D) Although some models support the idea that global warming is caused by human activity, other models do not and the cause therefore remains controversial.

Answer: A

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

The graph above, a portion of Figure 10.40, shows the atmospheric concentration of carbon dioxide for the past 800,000 years. Use the information in the graph to answer the following questions. Explain your answers.

1) Based on the graph, when was the maximum abundance of CO2 over the past 800,000 years? A) about 300,000 years ago B) about 125,000 years ago C) 1750 D) now Answer: D 2) Today's CO2 abundance is approximately ________ times the average value over the last 800,000 years.

A) 18 B) 1.8 C) 1.18 D) 0.18 Answer: B 36 Copyright © 2020 Pearson Education, Inc.

3) How would you describe the rapid variations in CO2 on the inset graph on the right?

A) The variations occur randomly every few years.

B) The variations occur randomly every few months.

C) The variations occur regularly every few years.

D) The variations occur regularly every year.

E) The variations occur regularly every few months.

Answer: D 4) Which physical mechanism could explain the fact that the atmospheric concentration of CO2 varies slightly over the course of each year?

A) Major volcanic eruptions every decade or so place additional CO2 in the atmosphere.

B) Every few years, another huge coal-powered power plant opens up and produces more CO2.

C) Seasonal changes in plant growth produce a regular yearly variation in CO2 levels, with the Northern Hemisphere (with much more land area) causing almost all the variation.

Answer: C 5) Now study Figure 10.39, which shows global temperatures from 1880. Focus on the period since about 1960, and compare what you notice about the temperatures to what you've learned about carbon dioxide levels in Questions 1—4. Which of the following statements best describes the relationship?

A) The warmest years correlate exactly with the years of greatest CO2 abundance, indicating that CO2 is the single most important factor controlling global temperature changes.

B) The warmest years correlate roughly with the years of greatest CO2 abundance, indicating that CO2 is important but other factors also contribute to global temperature changes.

C) The warmest years are not correlated with years of high CO2 abundance, indicating that factors other than CO2 have the most important effect on global temperature changes.

Answer: B Chapter Review Questions 1) Briefly describe the basic atmospheric characteristics of each of the five terrestrial worlds.

2) Use the balloon analogy to explain the origin of gas pressure. What is atmospheric pressure, and why does it decrease with altitude? What is 1 bar of pressure?

3) Is there any atmosphere at the orbital altitude of the Space Station? Explain.

4) What is the greenhouse effect? Describe how it warms a planet.

5) What factors determine a world's "no greenhouse" surface temperature? Explain the difference between "no green-house" and actual temperatures for each of the terrestrial worlds.

6) Describe Earth's basic atmospheric structure, from the ground up. How do interactions of sunlight and gases explain the existence of each of the atmospheric layers?

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7) Why is the sky blue? Why are sunrises and sunsets red?

8) Why does convection occur in the troposphere, leading to active weather, but not in the stratosphere?

9) What is ozone? How does the absence of ozone on Venus and Mars explain why these planets lack a stratosphere?

10) What is a magnetosphere? Describe its role in protecting any atmosphere from the solar wind and in creating auroras.

11) What is the difference between weather and climate?

12) Describe Earth's global wind patterns and the role of circulation cells. How does rotation affect these cells?

13) What are clouds made of? How does rain or snow form?

14) Describe each of the four factors that can lead to long-term climate change.

15) Describe each process by which atmospheres gain or lose gas. What factors control thermal escape?

16) Why do the Moon and Mercury have so little atmospheric gas?

17) How and why do seasons on Mars differ from seasons on Earth?

18) Describe the leading hypothesis for how Mars lost atmospheric gas. What role does Mars's size play in this process?

19) What do we mean by a runaway greenhouse effect? Explain why this process occurred on Venus but not on Earth.

20) Describe four ways in which Earth's atmosphere is unique among the terrestrial worlds, and how each is important to our existence.

21) What is the carbon dioxide cycle, and why is it so crucial to life on Earth?

22) Briefly summarize the evidence linking human activity to global warming. What are its potential consequences?

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Does It Make Sense?

Decide whether or not each of the following statements makes sense (or is clearly true or false).

Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.

Example: I walked east from our base camp at the North Pole.

Solution: The statement does not make sense because east has no meaning at the North Pole–all directions are south from the North Pole.

23) If Earth's atmosphere did not contain molecular nitrogen, x-rays from the Sun would reach the surface.

24) If the molecular oxygen content of Earth's atmosphere increased, our planet would warm up.

25) Earth's oceans must have formed at a time when no greenhouse effect operated on Earth.

26) In the distant past, when Mars had a thicker atmosphere, it also had a stratosphere.

27) If Earth rotated faster, hurricanes would be more common and more severe.

28) Mars would still have seasons even if its orbit around the Sun were perfectly circular rather than elliptical.

29) Mars once may have been warmer than it is today, but it could never have been warmer than Earth.

30) If the solar wind were much stronger, Mercury might develop a carbon dioxide atmosphere.

31) If Earth had as much carbon dioxide in its atmosphere as Venus, our planet would not have oceans.

32) A planet in another solar system has no life but has an Earth-like atmosphere with plentiful oxygen.

Quick Quiz 33) Which terrestrial world has the most atmosphere?

A) Venus B) Earth C) Mars Answer: No Correct Answer Was Provided.

34) The greenhouse effect occurs in the A) troposphere.

B) stratosphere.

C) lithosphere.

Answer: No Correct Answer Was Provided.

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35) What kind of light warms the stratosphere? A) infrared B) visible C) ultraviolet Answer: No Correct Answer Was Provided.

36) Which of the following is a strong greenhouse gas?

A) nitrogen B) water vapor C) oxygen Answer: No Correct Answer Was Provided.

37) In which direction do hurricanes in the Southern Hemisphere rotate?

A) clockwise B) counterclockwise C) either direction Answer: No Correct Answer Was Provided.

38) What is the leading hypothesis for Venus's lack of water?

A) Venus formed closer to the Sun and accreted very little water.

B) Its water is locked away in the crust.

C) Its water molecules were broken apart, and hydrogen was lost to space.

Answer: No Correct Answer Was Provided.

39) What kind of gas is most affected by thermal escape?

A) greenhouse gases B) light gases C) all gases equally Answer: No Correct Answer Was Provided.

40) About what fraction of Earth's atmosphere is CO2?

A) 90% B) 1% C) less than 0.1% Answer: No Correct Answer Was Provided.

41) What causes the release of oxygen into Earth's atmosphere?

A) outgassing B) vaporization C) photosynthesis Answer: No Correct Answer Was Provided.

42) Where is most of the CO2 that has outgassed from Earth's volcanoes?

A) in the atmosphere B) in space C) in rocks 40 Answer: No Correct Answer Was Provided.

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Inclusive Astronomy Use these questions to reflect on participation in science.

43) Group Discussion: The Global Climate Change Conversation.

Global warming will affect people of all nations, but wealthier nations are often in a better position to study how greenhouse gases affect Earth's climate and to develop technologies and enact policies that minimize those impacts. a) Gather in small groups to discuss and make a list of potential impacts of climate change. In each case, decide if all nations would be affected equally or if effects would be greater for either wealthier or less-developed nations. b) Discuss and make a list of potential steps that could be taken to reduce fossil fuel use and to mitigate climate change and its impacts on how people live. In each case, decide whether the step is likely to be equally difficult for all nations or more difficult for either wealthier or lessdeveloped nations. c) The world's primary forum for sharing scientific assessments of climate change, its impacts and risks, and options for adaptation and mitigation is the Intergovernmental Panel on Climate Change (IPCC), created in 1988 by the United Nations and the World Meteorological Organization. Do you think an organization founded by the United Nations is an appropriate forum for analyzing and sharing scientific findings about climate change? Should the United Nations be making public policy recommendations based on climate-change predictions reported by the IPCC? Defend your opinions to the group. d) Less-developed nations have fewer resources to devote to climate-change research and the development of mitigation technologies, but they will inevitably be affected by the policy decisions made by wealthier nations. To what extent should wealthier nations take this fact into account when developing their own policies? Should they make an active effort to include the voices of less-developed nations in scientific research and/or policy making relating to global warming? Defend your opinions to the group.

The Process of Science 44) Unanswered Questions: Mars. Choose one important but unanswered question about Mars's past, and discuss how we might answer this question in the future. Be as specific as possible, focusing on the type of evidence necessary to answer the question and how the evidence could be gathered. What are the benefits of finding answers to this question?

45) Humans vs. Robots. From a scientific standpoint, discuss what (if anything) we could learn about Mars from human missions that we could not learn from robotic missions. Considering only the scientific benefits and the costs, do you think it is worth sending humans to Mars? Are there other potential benefits of a human mission that would make such a mission more worthwhile? Defend your opinions.

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46) Skeptics' Claims on Global Warming. A small but vocal group of people still dispute that humans are causing global warming. Do some research to find the basis of their claims. Then defend or refute their findings based on your own studies and your understanding of the hallmarks of science discussed in Chapter 3. Note: You may find it useful to visit globalwarmingprimer.com, which features a free online primer (written by one of the authors of this textbook) about global warming and many of the skeptics' claims.

47) Group Discussion: The Politics of Global Warming. Polls show that, today, political beliefs strongly influence whether a person accepts the scientific view of global warming presented in this chapter. Use this question to spur discussion of this political divide and how it might be bridged. a) The basic science of global warming is not new; the first scientist to investigate what would happen if we were to double Earth's atmospheric carbon dioxide concentration was Svante Arrhenius, working more than 100 years ago. Each group member should read about his work by doing a search on "Arrhenius and global warming." Discuss why he concluded that an increase in carbon dioxide would cause warming, and whether there was any political dimension to his work. b) Margaret Thatcher, generally considered to be one of the iconic founders of modern conservatism, was among the first global leaders to speak out on global warming. Each group member should read (or view) the speech she delivered to the United Nations on November 8, 1989. Briefly discuss her words and then discuss why so many people now consider global warming to have a political dimension, when it clearly did not (at least in Thatcher's view) at that time. c) Find examples of conservative groups advocating action on global warming today (such as the Climate Leadership Council, the Green Tea Coalition, and RepublicEN.org). Discuss whether you agree with the goals of these groups, and whether learning about them alters your view on whether global warming should be considered a political issue. d) On college campuses, a coalition of campus Republicans and campus Democrats have joined together to form "Students for Carbon Dividends." In Congress, the "Climate Solutions Caucus" allows a member to join only if he or she also brings along a member of the opposing party.

Learn about and discuss each of these two groups and their prospects for success with their stated missions.

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48) Group Activity: Moon Colony. Several nations are considering establishing a permanent human presence on the Moon, and some private companies are also considering it. a) Working independently, research at least one proposed plan for returning humans to the Moon, including estimated costs for the plan. b) Form groups of three to four students and take turns reporting on your findings from part a. c) Considering what you learned from the research, as well as what you've learned in this textbook, make a list of potential scientific benefits of sending humans back to the Moon. Then make a separate list of any nonscientific (for example, economic, political, or educational) benefits that might arise from a Moon colony. d) Discuss how the colony might be supplied with food, water, and air.

Are there resources on the Moon that could be used to provide any of these, or would they all need to be supplied from Earth? e) Come to a group consensus about whether it is worth the cost of returning to the Moon. If your group is in favor, describe specifics of how you think it should be done; for example, should it be done by individual nations, by an international effort, or by private companies? If your group is against returning humans to the Moon, explain why.

Investigate Further

49) Clouds of Venus. Table 10.2 shows that Venus's surface temperature in the absence of the greenhouse effect is lower than Earth's, even though Venus is closer to the Sun. a) Explain this unexpected result in one or two sentences. b) Suppose Venus had neither clouds nor greenhouse gases. What do you think would happen to the surface temperature of Venus? Why? c) How are clouds and volcanoes linked on Venus? What change in volcanism might result in the disappearance of clouds? Explain.

50) Atmospheric Structure. Study Earth's average atmospheric structure (Figure 10.7). Sketch a similar curve for each of the following cases, and explain how and why the structure would be different in each case. a) Suppose Earth had no greenhouse gases. b) Suppose the Sun emitted no ultraviolet light. c) Suppose the Sun had a higher output of x-rays.

51) Magic Mercury. Suppose we could magically give Mercury the same atmosphere as Earth.

Assuming this magical intervention happened only once, would Mercury be able to keep its new atmosphere? Explain.

52) A Swiftly Rotating Venus. Suppose Venus rotated as rapidly as Earth. Briefly explain how and why you would expect it to be different in terms of each of the following: geological processes, atmospheric circulation, magnetic field, and climate history.

53) Coastal Winds. During the daytime, heat from the Sun tends to make the air temperature warmer over land near the coast than over the water offshore. At night, land cools off faster than the sea, so temperatures tend to be cooler over land. Use these facts to predict the directions in which winds generally blow during the day and at night in coastal regions. Explain your reasoning in a few sentences. (Diagrams might help.)

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54) Sources and Losses. Choose one process by which atmospheres can gain gas and one by which they can lose gas. For each process, write a few sentences that describe it and how it depends on each of the following fundamental planetary properties: size, distance from the Sun, and rotation rate.

55) Two Paths Diverged. Briefly explain how the different atmospheric properties of Earth and Venus can be explained by the fundamental properties of size and distance from the Sun. 56) Change in Fundamental Properties. Choose one property of Earth–either size or distance from the Sun–and suppose that it had been different (for example, size smaller or distance greater). Describe how this change would have affected Earth's subsequent atmospheric history and the possibility of life on Earth.

57) Feedback Processes in the Atmosphere. As the Sun gradually brightens in the future, how can the CO2 cycle respond to reduce the warming effect? Which parts of the cycle will be affected? Is this an example of positive or negative feedback?

58) Earth to Mars. Section 10.5 discusses what might happen to Earth if it were suddenly moved to the orbit of Venus. What do you think would happen to Earth if it were suddenly moved to the orbital distance of Mars? Write a few sentences explaining your answer.

59) Terraforming Mars. Some people have suggested that we might be able to engineer Mars in a way that would cause its climate to warm and its atmosphere to thicken. This type of planet engineering is called terraforming, because its objective is to make a planet more Earth-like and easier for humans to live on. Discuss possible ways to terraform Mars. Do any of these ideas seem practical? Do they seem like good ideas? Defend your opinions.

60) Global Warming Op-Ed. What, if anything, should we be doing that we are not doing already to alleviate the threat of global warming? Write a one-page editorial summarizing and defending your opinion.

Quantitative Problems

61) The Mass of an Atmosphere. What is the total mass of Earth's atmosphere? You may use the fact that 1 bar is the pressure exerted by 10,000 kilograms pushing down on a square meter in Earth's gravity. Remember that every square meter of Earth experiences this pressure from the atmosphere above it. Alternatively, you may start with the English unit value for pressure of 14.7 pounds per square inch and convert to kilograms for your final answer. Remember that the surface area of a sphere of radius r is 4ℼr2.

62) The Role of Reflectivity. By assuming 0% and 100% reflectivity (respectively), find the maximum and minimum possible "no greenhouse" temperatures for a planet at 1 AU. What reflectivity would be necessary to keep the average temperature exactly at the freezing point?

Compare this value to Earth's actual reflectivity in Table 10.2.

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63) The Cooling Clouds of Venus. Table 10.2 shows that Venus's temperature in the absence of the greenhouse effect is lower than Earth's, even though Venus is closer to the Sun. What would Venus's "no greenhouse" temperature be if its clouds were more transparent, giving a reflectivity the same as Earth's? What would the actual surface temperature be in this case if the greenhouse effect increased the surface temperature by the same number of degrees that it does today?

64) Mars's Elliptical Orbit. Mars's distance from the Sun varies from 1.38 AU to 1.66 AU. How much does this affect its "no greenhouse" surface temperature at different times of year?

Comment on how this affects Mars's seasons.

65) Escape from Venus. a) Calculate the escape velocity from Venus's exosphere, which begins about 200 kilometers

above the surface. (Hint: See Mathematical Insight 4.4.) b) Calculate and compare the thermal speeds of hydrogen and deuterium atoms at the exospheric temperature of 350 K. The mass of a hydrogen atom is 1.67 × 10−27 kilogram, and the mass of a deuterium atom is about twice the mass of a hydrogen atom. c) In a few sentences, comment on the relevance of these calculations to the question of whether Venus has lost large quantities of water.

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The Cosmic Perspective, 9e (Bennett et al.)

Chapter 11 Jovian Planet Systems Section 11.1 1) Which of the following planets cannot be seen with the naked eye?

A) Venus B) Mars C) Jupiter D) Saturn E) Neptune Answer: E 2) Why do the jovian planets in our solar system bulge around their equators?

A) They are much more massive than the terrestrial planets.

B) Their large systems of moons and rings gravitationally attract the mass around the equator more.

C) Their rapid rotation flings the mass near the equator outward.

D) Their internal heat sources exert more pressure at the equator.

Answer: C 3) Which planet's existence was correctly predicted based on mathematical calculations of the orbital motions of other planets before it was seen by a telescope?

A) Mercury B) Uranus C) Neptune D) Pluto Answer: C 4) Which jovian planets have compositions dominated by hydrogen compounds such as methane, ammonia, and water?

A) Uranus and Neptune B) Saturn and Uranus C) Jupiter and Neptune D) Saturn, Uranus, and Neptune E) Saturn and Neptune Answer: A

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5) Based on the graph above, what would be the approximate radius of a hydrogen/helium planet with a mass one-tenth that of Jupiter?

A) about 0.7 times the radius of Jupiter B) about 0.5 times the radius of Jupiter C) about the same as the radius of Jupiter D) about 1.1 times the radius of Jupiter Answer: A 6) Based on the graph above, a planet with twice the mass of Jupiter would have a radius that is A) about twice the radius of Jupiter.

B) about 5% larger than the radius of Jupiter.

C) about half the radius of Jupiter.

D) about 10% smaller than the radius of Jupiter.

Answer: B 7) Why is Saturn almost as large in radius as Jupiter despite its smaller mass?

A) Jupiter's greater mass compresses it more, thus increasing its density.

B) Saturn's rings make the planet look bigger.

C) Saturn is farther from the Sun, thus cooler, and therefore less compact.

D) Saturn has a larger proportion of hydrogen and helium than Jupiter, and is therefore less dense.

E) Jupiter's strong magnetic field constrains its size.

Answer: A 8) How much of Jupiter is made of material that is in a gaseous phase?

A) Jupiter is entirely made of gas, all the way down to its center.

B) Jupiter is entirely gaseous except for its rock core.

C) Only about the outer 10% of Jupiter's interior is gaseous.

D) Jupiter does not contain any gaseous phase material; it is all liquid or liquid metallic.

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9) Key evidence indicating that Jupiter contains a lot of internal heat comes from the fact that A) Jupiter's cloudtops are surprisingly hot.

B) Jupiter emits about twice as much energy as it receives from the Sun. C) The Galileo probe measured the temperature deep in Jupiter's interior.

D) Jupiter's moons are hotter than we would expect them to be from sunlight alone.

Answer: B 10) How do astronomers think Jupiter generates most of its internal heat?

A) tidal heating B) internal friction due to its high rotation rate C) chemical processes D) nuclear fusion in the core E) by slowly contracting Answer: E 11) Based on models, how does Jupiter's core compare in size and mass to Earth?

A) It is about the same size and mass as Earth.

B) It is about 10 times as large in both size and mass as Earth.

C) It is about the same mass, but is 10 times as large in size as Earth.

D) It is about the same size, but has about 10 times as much mass as Earth.

E) Jupiter doesn't have a core—it is made entirely from hydrogen and helium.

Answer: D 12) What is Jupiter's Great Red Spot?

A) a giant storm that is about twice as wide as the planet Earth B) a giant crater on the surface of Jupiter C) a portion of strongly heated gas near the surface of Jupiter caused by a collision with a comet D) a huge patch of sulfur in Jupiter's atmosphere E) reflected sunlight that is red for the same reason sunrises and sunsets are red on Earth Answer: A 13) Why is Jupiter denser than Saturn?

A) Jupiter has a higher proportion of hydrogen compounds and rocks than Saturn.

B) Jupiter's greater mass compresses its interior to a greater extent than that of Saturn.

C) Jupiter has a much more massive core than Saturn.

D) Jupiter has a greater proportion of helium compared to hydrogen than Saturn.

Answer: B 14) Why is Neptune denser than Saturn?

A) Neptune has a higher proportion of hydrogen compounds and rocks than Saturn.

B) Neptune has a larger mass and stronger gravity than Saturn.

C) Neptune has a much more massive core than Saturn.

D) Neptune has a greater proportion of helium compared to hydrogen than Saturn.

Answer: A

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15) Which of the following statements is thought to be true of the jovian planets?

A) All have cores of about the same mass, but differ in the amount of surrounding hydrogen and helium.

B) The major differences between the planets can be explained by the different masses of their cores.

C) Jupiter and Saturn are made mostly of ammonia while Uranus and Neptune are mostly methane.

D) Jupiter and Saturn are made mostly of hydrogen while Uranus and Neptune are mostly helium.

Answer: A

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16) Refer to this figure from the textbook:

The Galileo spacecraft dropped a probe into Jupiter's atmosphere that survived to a depth of about 200 kilometers, or 0.3% of Jupiter's radius. Which is the deepest layer in which this probe was able to make measurements?

A) the gaseous hydrogen layer B) the liquid hydrogen layer C) the metallic hydrogen layer D) the core Answer: A 17) Why does Jupiter have several distinct cloud layers?

A) The higher clouds are made of gaseous hydrogen and the lower clouds of liquid hydrogen.

B) Different gases can condense at different altitudes in Jupiter's atmosphere.

C) The atmospheric composition differs at different altitudes in Jupiter's atmosphere.

D) The different cloud layers are a result of differing wind speeds.

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18) Jupiter's "striped" appearance is a result of A) alternating bands of rising and falling air at different latitudes. B) alternating bands of liquid and gaseous material at different latitudes. C) changes in the atmospheric composition with latitude. D) changes in the strength of Jupiter's magnetic field with latitude. Answer: A 19) Why do Uranus and Neptune appear blue? A) Oceans that are visible through their atmospheres are blue. B) The nitrogen gas in their atmospheres absorbs red light. C) The methane gas in their atmospheres absorbs red light. D) Small dust grains preferentially scatter blue light. Answer: C 20) Where do scientists think that Jupiter's strong magnetic field is generated? A) in its rocky core B) in its metallic hydrogen layer C) in its liquid hydrogen layer D) in its gaseous hydrogen layer E) above the cloudtops Answer: B Section 11.2 1) Why do most jovian moons show the same face to their planet? A) because the moons once had atmospheres B) because the entire solar nebula rotated in the same direction C) because of the law of conservation of angular momentum D) because of tidal forces acting on the moons E) No one knows; it is still a mystery. Answer: D 2) The largest Jovian moons have sizes comparable to Mercury.

Why do they have an icy composition compared to Mercury's rocky composition? A) They are captured comets. B) They formed from hydrogen compounds expelled by the jovian planets. C) They experienced many more comet impacts during the heavy bombardment. D) They formed beyond the frost line, where ices were more abundant than metals and rock. Answer: D

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3) The moons of Jupiter are A) all made of rock.

B) all made of ice.

C) made of a mixture of rock and ice.

D) all captured asteroids.

E) made mostly of hydrogen and helium gas.

Answer: C 4) Why are there no impact craters on the surface of Io? A) Io is too small to have experienced many impacts.

B) Jupiter's strong gravity prevents impacts from hitting Io. C) All of Io's impact craters have been buried by lava flows.

D) Any impact craters that once existed on Io were eroded by winds and rain.

E) Io formed only recently, long after the heavy bombardment ended.

Answer: C 5) What mechanism is most responsible for generating the internal heat of Io that drives volcanic activity?

A) accretion B) radioactive decay C) differentiation D) tidal heating E) bombardment Answer: D 6) What makes the surface of Io appear red and orange?

A) sulfur expelled by volcanic eruptions B) Rocks on the surface were rusted by oxygen.

C) clays on the surface formed in past lakes D) reflection of Jupiter's light off of sheets of ice E) Io's thermal spectrum peaks in the red-orange part of the spectrum.

Answer: A 7) Which of the following applies to Io? A) It is the most volcanically active body in the solar system.

B) It is thought to have a deep, subsurface ocean of liquid water.

C) It is the only moon in our solar system with an atmosphere thicker than Earth's atmosphere.

D) It is the largest moon in the solar system.

E) It is probably a captured Kuiper belt object.

Answer: A

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8) Which of the following applies to Europa?

A) It is the most volcanically active body in the solar system.

B) It is thought to have a deep, subsurface ocean of liquid water.

C) It is the only moon in our solar system with an atmosphere thicker than Earth's atmosphere.

D) It is the largest moon in the solar system.

E) It is probably a captured Kuiper belt object.

Answer: B 9) Which of the following applies to Ganymede?

A) It is the most volcanically active body in the solar system.

B) It is the only moon in our solar system with an atmosphere thicker than Earth's atmosphere.

C) It is the largest moon in the solar system.

D) It is probably a captured Kuiper belt object.

Answer: D 10) Which of the following best describes the orbital resonance shared by Io, Europa, and Ganymede?

A) Io completes four orbits in the same time it takes Europa to complete two orbits and Ganymede to complete one orbit.

B) Io, Europa, and Ganymede each have the same orbital period around Jupiter.

C) Io, Europa, and Ganymede all show the same face to Jupiter at all times.

D) Io, Europa, and Ganymede are always oriented in a straight line.

Answer: A 11) Which of the following best describes the surface of Europa?

A) The surface is comprised of ice with many cracks in it.

B) The surface is comprised of very smooth ice.

C) The surface is covered by a liquid water ocean.

D) The surface is rocky and dry.

E) The surface is covered in liquid methane.

Answer: A 12) Based on the given densities, which of these jovian moons contain the greatest percentage of rocky material and the smallest percentage of icy material?

A) Callisto (density = 1.86 grams/cc) B) Europa (density = 2.97 grams/cc) C) Io (density = 3.57 grams/cc) D) Ganymede (density = 1.94 grams/cc) Answer: C 13) Which of the following moons has the most substantial atmosphere?

A) Titan B) Ganymede C) Io D) Europa E) Mimas Answer: A

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14) What is the most abundant gas in Titan's atmosphere?

A) methane B) nitrogen C) hydrogen compounds D) oxygen E) argon Answer: B 15) Which of the following applies to Titan?

A) It is the most volcanically active body in the solar system.

B) It is thought to have a deep, subsurface ocean of liquid water.

C) It is the only moon in our solar system with an atmosphere thicker than Earth's atmosphere.

D) It is the largest moon in the solar system.

E) It is probably a captured Kuiper belt object.

Answer: C 16) Which of the following statements about Saturn's moon Titan is not true?

A) It rains liquid methane and ethane.

B) Its atmosphere contains abundant oxygen.

C) Its temperature is too cold for liquid water to exist on its surface.

D) Its surface is hidden from view by a thick atmosphere.

E) It orbits Saturn.

Answer: B 17) Which of the following describes a major similarity between Titan and Earth?

A) Both have nearly identical atmospheric compositions of nitrogen and oxygen.

B) Both have features of erosion due to a liquid, except on Titan it is liquid methane and ethane rather than liquid water.

C) Both have many active volcanoes erupting with molten rock, except the rock is higher density on Titan.

D) The two worlds have very similar surface temperatures and surface compositions.

Answer: B 18) Which moon did the Huygens probe land on?

A) Ganymede B) Callisto C) Europa D) Titan E) Triton Answer: D

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19) What did the photographs from the Huygens probe reveal as it descended to the surface of Titan?

A) dry, featureless plains B) rivers and lakes of liquid water C) a pockmarked surface covered with volcanos D) features that look like river valleys and an ancient shoreline Answer: D 20) Why were scientists surprised to find evidence of subsurface liquid water on Enceladus?

A) Enceladus was thought to be too far from the Sun to have a subsurface zone of liquid water.

B) Enceladus was thought to be too small to have a subsurface zone of liquid water.

C) Enceladus was not expected to have any water or ice in its composition.

D) Scientists expect that Enceladus would have lost its liquid water to solar wind stripping by now.

Answer: B 21) Why do astronomers suspect that Triton was a Kuiper belt object that was captured by Neptune?

A) It orbits Neptune in the opposite direction of Neptune's rotation.

B) It is too large to have been formed in the jovian nebula that formed Neptune.

C) It has an atmosphere and a measurable greenhouse effect.

D) It undergoes seasonal changes.

E) It is colder than any other moon or planet.

Answer: A 22) Which of the following applies to Triton?

A) It is the most volcanically active body in the solar system.

B) It is thought to have a deep, subsurface ocean of liquid water.

C) It is the only moon in our solar system with an atmosphere thicker than Earth's atmosphere.

D) It is the largest moon in the solar system.

E) It is probably a captured Kuiper belt object.

Answer: E 23) What is the most important reason why an icy moon is more likely to be geologically active than a rocky moon of the same size?

A) Ice is less rigid and has a lower melting point than rock.

B) Ice is colder than rock.

C) Ice contains more radioactive elements than rock.

D) Ice is affected by tidal forces to a greater extent than rock.

E) Ice is less dense than rock.

Answer: A

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Section 11.3 1) Why are Saturn's rings so thin?

A) They are attached to Saturn's very thin equator.

B) The "gap" moons shepherd the particles and maintain its thin profile.

C) Any particle in the ring with an orbital tilt would collide with other ring particles.

D) Solar radiation pressure keeps particles pressed into the rings.

E) They formed from a flat sheet of material that broke apart.

Answer: C 2) Which of the following best describes the composition of the particles that make up Saturn's rings?

A) largely water ice B) shiny metallic grains C) largely methane ice D) dense rock E) hydrogen and helium gas Answer: A 3) Planetary rings are A) nearer to their planet than any of the planet's large moons.

B) orbiting in the equatorial plane of their planet.

C) composed of a large number of individual particles that orbit their planet in accord with Kepler's third law.

D) known to exist for all of the jovian planets in our solar system.

E) All of the above Answer: E 4) Which of the following statements about the rings of the four jovian planets is not true?

A) All rings lie within two to three planetary radii of their planet.

B) All the particle orbits are fairly circular and near their planet's equatorial plane.

C) All have gaps and ringlets.

D) All probably look much the same as they did when the solar system first formed.

E) All are made of individual particles of rock or ice that orbit in accord with Kepler's laws: inner ring particles orbiting faster, and outer ring particles orbiting slower.

Answer: D 5) Which of the jovian planets in our solar system have rings?

A) Jupiter and Saturn only B) Saturn only C) Saturn, Uranus, and Neptune only D) Neptune only E) all four: Jupiter, Saturn, Uranus, and Neptune Answer: E

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General Chapter Questions 1) You are somewhere in the solar system. You can see Jupiter high in the sky, and it looks enormous. You can also see numerous nearby volcanoes, some that are currently erupting.

Where are you?

A) Mars B) Venus C) Europa D) Io Answer: D 2) You are somewhere in the solar system. It's much colder than Earth, and you are airborne in the planet's atmosphere, with blue skies around you. And while you can tell that your planet is rotating fairly rapidly, it is remaining daylight at all times, indicating a very large axis tilt (much larger than Earth's). Where are you?

A) Saturn B) Uranus C) Mars D) Jupiter Answer: B 3) Why do almost all moons exhibit synchronous rotation in which they rotate with the same period as they orbit their planet?

A) The moons formed this way, with the same rotational and orbital periods.

B) Most jovian moons were formed out of their planet's nebula with the same orbital period.

C) The moons probably once orbited farther away and more slowly, but friction with solar nebula gas caused their orbits to come closer to their planet, speeding them up.

D) The moons probably once rotated faster, but tidal friction slowed their rotations to match their orbital periods.

E) Synchronous rotation is caused by orbital resonances with other moons.

Answer: D 4) The mass of Neptune can be calculated from measurements of A) Neptune's orbital period and its distance from the Sun. B) the Sun's mass and how Neptune's speed changes during its elliptical orbit around the Sun. C) the masses of Neptune's moons, Triton and Nereid.

D) the gravitational influence of Jupiter and Saturn on Neptune's orbit around the Sun. E) the orbital period and distance of the moon Triton from Neptune.

Answer: E

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5) Suppose you are head of NASA two decades from and have to make some budget cuts.

Your agency has been planning four different missions to search for life in the solar system, and you need to cancel the least promising one. Which one do you cancel? A) a mission to dig beneath an ancient Martian river bed B) a mission to explore the ice geysers of Saturn's Moon Enceladus C) a mission designed to plunge deep beneath Jupiter's cloud layers D) a mission to drill through the icy surface of Jupiter's Moon Europa Answer: C Short Answer Questions 1) What's the best explanation for jovian planets farther from the Sun having less mass? Answer: The differences in the sizes of the jovian planets are due to their capturing different amounts of gas from the solar nebula, since their cores are all about the same size. Icy planetesimals took longer to accrete in the outer solar system because they were more spread out there. Thus, more distant jovian planets didn't have as much time as Jupiter to capture gas from the solar nebula before the nebula was cleared by the solar wind. 2) What do we mean by "ice geology"? Give an example illustrating why it is important in the outer solar system. Answer: Ice geology is the geology that can occur on icy worlds, which can occur at lower temperature than similar geology on rocky worlds. It is important in the outer solar system because it allows worlds to have active geology at smaller sizes than required for rocky worlds. This explains, for example, why Europa and Enceladus are geologically active despite being relatively small in size. 3) Briefly explain how Uranus and Neptune were discovered. Answer: Uranus was discovered with a telescope (by William and Caroline Herschel). Neptune was discovered based on its gravitational influence on other planets (Uranus, in particular). Reading Quiz Questions 1) Which of the following is a general characteristic of the four jovian planets in our solar system? A) They are significantly lower in average density than are the terrestrial planets. B) They have very high levels of volcanic and tectonic activity. C) They are made predominantly of elements heavier than hydrogen and helium. D) They rotate more slowly than the terrestrial planets. Answer: A

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2) Which of the following best describes the internal layering of Jupiter, from the center outward?

A) core of rock, metal, and hydrogen compounds thick layer of metallic hydrogen layer of liquid hydrogen layer of gaseous hydrogen cloud layer B) core of rock and metal mantle of lower density rock upper layer of gaseous hydrogen cloud layer C) core of solid rock layer of solid metallic hydrogen layer of pure liquid hydrogen cloud layer D) core of liquid hydrogen compounds liquid hydrogen layer metallic hydrogen layer gaseous hydrogen layer cloud layer Answer: A 3) Which of the following statements comparing the jovian interiors is not thought to be true?

A) They all have the same exact set of internal layers, though these layers differ in size.

B) They all have cores of roughly the same mass.

C) They all have cores that contain at least some rock and metal.

D) Deep inside them, they all have pressures far higher than that found on the bottom of the ocean on Earth.

Answer: A 4) The energy in the atmospheres of most of the jovian planets comes A) almost entirely from their interiors.

B) almost entirely from the Sun. C) both the Sun and their interiors, with both contributing significantly.

D) tidal heating.

Answer: C 5) Overall, Jupiter's composition is most like that of A) the Sun. B) Earth.

C) a comet.

D) an asteroid.

Answer: A

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6) Jupiter's colors come in part from its three layers of clouds. Which of the following is not the primary constituent of one of Jupiter's cloud layers?

A) clouds of sulfuric acid B) clouds of water C) clouds of ammonium hydrosulfide D) clouds of ammonia Answer: A 7) How do typical wind speeds in Jupiter's atmosphere compare to typical wind speeds on Earth?

A) They are much faster than hurricane winds on Earth.

B) They are about the same as average winds on Earth.

C) They are slightly faster than average winds on Earth.

D) They are slightly slower than average winds on Earth.

Answer: A 8) What is the Great Red Spot?

A) a long-lived, high-pressure storm on Jupiter B) a hurricane that comes and goes on Jupiter C) a place where reddish particles from Io impact Jupiter's surface D) a region on Jupiter where the temperature is so high that the gas glows with red visible light Answer: A 9) What atmospheric constituent is responsible for the blue color of Uranus and Neptune?

A) methane B) hydrogen C) water D) ammonia Answer: A 10) Jupiter's magnetic field is ________ Earth's magnetic field.

A) about 20,000 times as strong as B) about the same strength as C) about twice as strong as D) much weaker than Answer: A 11) Which of the following statements about the moons of the jovian planets is true?

A) Most of the moons have the potato-like shapes of asteroids, but a few are large enough to be spherical in shape.

B) Even the biggest moons are smaller than any of the planets or dwarf planets in our solar system.

C) All of the moons are barren and essentially airless, like our own Moon.

D) The moons are made almost entirely of rock and metal.

Answer: A

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12) Which statement about Jupiter's moon Io is true?

A) It is the most volcanically active body in our solar system.

B) It is thought to have a deep, subsurface ocean of liquid water.

C) It is the largest moon in the solar system.

D) It is the only moon in the solar system with a thick atmosphere.

Answer: A 13) What is tidal heating?

A) a source of internal heat caused by varying tidal forces acting on a moon or other object B) a source of internal heat that occurs on all moons that are large enough to be spherical C) a source of surface heating caused by the sloshing of water or other liquids D) a source of surface heating caused by active volcanoes like those on Io Answer: A 14) Which moon has a thick atmosphere made mostly of nitrogen?

A) Titan B) Triton C) Ganymede D) Europa Answer: A 15) The Huygens probe took numerous pictures as it descended to the surface of Saturn's moon Titan in 2005. What did the pictures show?

A) features or erosion, including what appeared to be dry river valleys and lakebeds B) primitive life forms C) a densely cratered surface D) lava flows of molten basalt Answer: A 16) Which of the following moons is considered likely to have a deep, subsurface ocean of liquid water?

A) Europa B) Io C) Miranda D) Triton Answer: A 17) Which large jovian moon is thought to have been captured into its present orbit?

A) Triton B) Callisto C) Titan D) Io Answer: A

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18) Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings?

A) countless icy particles, ranging in size from dust grains to large boulders B) a solid, shiny surface, looking much like a piece of a Blu-ray disk or DVD (or vinyl record album) but a lot bigger C) dozens of large "moonlets" made of metal and rock, each a few kilometers across D) long, solid strings of matter, each distinct from the next Answer: A 19) Which statement about planetary rings is not true?

A) Saturn's rings formed along with its moons 4.6 billion years ago.

B) All four jovian planets have rings.

C) Individual ring particles orbit their planet in accord with Kepler's laws, so that particles closer in orbit faster than particles farther out.

D) Rings are always located closer to a planet's surface than any large moons.

Answer: A Concept Quiz Questions 1) According to models of planetary interiors, the differences in mass among the four jovian planets (Jupiter, Saturn, Uranus, and Neptune) are due primarily to differences A) in the amounts of material in the layers extending from the tops of their cores to their surfaces.

B) in their core masses.

C) in composition.

D) in density.

Answer: A 2) According to current models of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?

A) Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula.

B) Ices were able to condense at the distance of Jupiter and Saturn, but only rock and metal could condense at the distances of Uranus and Neptune.

C) The solar nebula had different chemical composition at different distances from the Sun, leading to the differences in mass.

D) The size differences are thought to be a random coincidence.

Answer: A 3) Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?

A) They actually contain relatively little material in a gaseous state.

B) The materials they are made of are not the kinds of thing we usually think of as gases.

C) They are not in any sense "giants."

D) Actually, it's a great description because these worlds are big and gaseous throughout.

Answer: A

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4) What would happen to Jupiter if we could somehow double its mass?

A) Its density would increase, but its diameter would barely change.

B) Its density would decrease and its diameter would double.

C) Its density would stay about the same and its volume would double.

D) It would become a star, with nuclear fusion in its core.

Answer: A 5) Which of the following most likely explains why Jupiter's interior releases so much heat?

A) Jupiter is gradually contracting in size.

B) heat from radioactive decay C) a slow rate of nuclear fusion in Jupiter's core D) tidal heating Answer: A 6) Which planet may have helium rain in its interior, and what does this rain do?

A) Saturn, where it generates heat as it falls downward B) Uranus, where it makes the ground wet C) Neptune, where it is restructuring the planet's interior D) Jupiter, where it may be an energy source for the Great Red Spot Answer: A 7) Why does Jupiter have three distinct layers of clouds?

A) The three layers represent clouds made of gases that condense at different temperatures.

B) Jupiter has three different types of wind, each of which makes a different type of cloud.

C) The three layers reflect regions of Jupiter's atmosphere with different chemical compositions.

D) Clouds form randomly, so on average there are always three layers.

Answer: A 8) Which of the following best explains why we see horizontal "stripes" in images of Jupiter and Saturn?

A) The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds.

B) The dark and light stripes correspond to alternating bands of different chemical composition.

C) There are three different color stripes corresponding to the three different types of clouds found on these planets.

D) Dark stripes are in places with strong winds and light stripes are in places with weak winds.

Answer: A 9) Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which factor explains why?

A) Temperatures on Jupiter and Saturn are too high for methane to condense.

B) Jupiter and Saturn do not contain any methane gas.

C) The rapid rotation of Jupiter and Saturn prevents methane clouds from forming.

D) The stronger gravity on Jupiter and Saturn pulls methane downward so that it can't form clouds.

Answer: A

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10) Which jovian planet has the most extreme seasonal changes, and why?

A) Uranus, because of its extreme axis tilt B) Jupiter, because of its large mass C) Saturn, because it has an axis tilt similar to Earth D) Neptune, because of its varying distance from the Sun Answer: A 11) Why is the radiation so intense in the region that traces Io's orbit around Jupiter (the Io torus)?

A) The region is full of gases that become ionized after they are released from volcanoes on Io. B) Io's gravity allows this region to capture huge numbers of charged particles from the solar wind.

C) An orbital resonance between Io, Europa, and Ganymede makes the radiation intense.

D) Jupiter's strong magnetic field makes the radiation intense everywhere, and the region around Io is no different than any other region.

Answer: A 12) Which of the following is a key factor in explaining why many jovian moons have been more geologically active than the Moon or Mercury?

A) Jovian moons contain much more ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.

B) The jovian moons are considerably larger than the Moon and Mercury and therefore have retained much more internal heat.

C) The jovian moons probably have far more internal heat generated by radioactive decay than do the Moon or Mercury.

D) Because of their greater distances from the Sun, the jovian moons receive much less heat from the Sun. Answer: A 13) All the following statements are true. Which one is most important in explaining the tremendous tidal heating that occurs on Io? A) Io orbits Jupiter on an elliptical orbit as a result of orbital resonances with other moons.

B) Io is the closest to Jupiter of Jupiter's large moons.

C) Io exhibits synchronous rotation, meaning that its rotation period and orbital period are the same.

D) Io orbits Jupiter in the Io torus, and therefore has a surface that is bombarded by many charged particles.

Answer: A 14) Which of the following is not a piece of evidence supporting the idea that Europa may have a subsurface ocean?

A) Astronomers have detected small lakes of liquid water on Europa's surface.

B) Europa has a magnetic field that appears to be induced by Jupiter's magnetic field.

C) Photos of Europa's surface show regions that appear to consist of jumbled icebergs frozen in place.

D) Europa's surface shows few impact craters.

Answer: A

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15) Which of the following is most unlikely to be found on Titan?

A) lakes of liquid water in the warmer equatorial regions B) lakes of liquid methane ethane C) rain or snow consisting of methane or ethane droplets or ice crystals D) volcanic outgassing of methane and other gases Answer: A 16) What major feature of Saturn's moon Enceladus led scientists to suspect it might have a subsurface ocean?

A) fountains of ice spraying out from the surface into space B) surface lakes of liquid methane or ethane C) its large mass and size D) its many active volcanoes Answer: A 17) What key evidence suggests that Triton is a captured moon?

A) Triton orbits Neptune in a direction opposite that of Neptune's rotation.

B) Triton is small and potato-shaped, which is common of captured moons.

C) Triton is too large to have been formed in the "miniature solar nebula" thought to have surrounded Neptune in its early history.

D) Triton appears to be made mostly of ice.

Answer: A 18) Which statement about Saturn's rings is not true?

A) The rings must look much the same today as they did shortly after Saturn formed.

B) The large gap known as the Cassini Division is shaped by an orbital resonance with the moon Mimas, which orbits well outside the rings.

C) Some features of the rings are shaped by small moons that actually orbit within the ring system.

D) The rings are so thin that they essentially disappear from view when seen edge-on.

Answer: A

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Visual Quiz Questions 1) Which of the following shows the four jovian planets correctly scaled in size?

A)

B)

C)

D)

Answer: A

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2) Which of the following photos shows the planet Neptune?

A)

B)

C)

D)

E)

Answer: A

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3) What is the name of the feature indicated by the arrow in this photo?

A) the Great Red Spot B) the Io torus C) the Great Dark spot D) the Cassini Division Answer: A 4) According to this graph, a planet with 10 times the mass of Jupiter would have a radius about ________ as that of Jupiter.

A) the same B) 10 times as large C) 100 times as large D) 60% as large Answer: A

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5) What are all the blue lines connecting to Jupiter supposed to represent in this picture?

A) Jupiter's magnetic field B) the solar wind C) blue light reflected from methane clouds D) the orbits of some of Jupiter's many moons.

Answer: A 6) What are all the black spots on this object?

A) volcanoes on Jupiter's moon Io B) methane lakes on Saturn's moon Titan C) impact craters on Uranus's moon Miranda D) wind streaks on Neptune's moon Triton E) giant cliffs on the planet Mercury Answer: A

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7) What is this object?

A) Jupiter's moon Europa B) Saturn's moon Titan C) Uranus's moon Miranda D) Neptune's moon Triton E) Jupiter's moon Callisto Answer: B 8) What is this object?

A) Jupiter's moon Europa B) Saturn's moon Titan C) Uranus's moon Miranda D) Neptune's moon Nereid E) Jupiter's moon Callisto Answer: A

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9) What is this object?

A) Ice particles and water vapor are spraying out from the surface.

B) A comet is impacting the surface.

C) Pebble-size particles from Saturn's rings are raining down onto the surface.

D) Sunlight is reflecting off clouds in Enceladus's atmosphere.

Answer: A 10) This painting shows an artist's conception of what it would look like to be within Saturn's system of rings. Notice the many whitish "balls" visible in this painting. Based on what you have learned about rings, about how large are each of these "balls," on average?

A) about a size that you could hold in your arms B) about the size of a large asteroid C) about the size of Earth's Moon D) They are microscopic clusters of about 10 to 20 atoms each.

Answer: A

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

Left: Approximate colors of Io in visible light; black spots are volcanoes that are active or have recently gone inactive. Right: Infrared thermal emission from Io; bright spots are active volcanoes. (Both images are from Galileo data and show the same face of Io, but taken at different times.)

1) What do the colors in the right image represent?

A) the actual colors of Io's surface B) the colors we would see if we had infrared vision C) the intensity of the infrared light D) regions of different chemical composition on the surface Answer: C 2) Which color in the right image represents the highest temperatures?

A) blue B) green C) orange D) red E) white Answer: E 3) The right image was obtained when only part of Io was in sunlight. Based on the colors, which part of the surface was in sunlight?

A) the left side B) the right side C) only the peaks of the volcanoes Answer: B

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4) By comparing the two images, what can you conclude about Io's volcanoes?

A) Every black spot in the visible image has a bright spot in the infrared image, so all of Io's volcanoes were active when the photos were taken.

B) There are more black spots in the visible image than bright spots in the infrared image, so many of Io's volcanoes were inactive when the photos were taken.

C) There are more bright spots in the infrared image than black spots in the visible image, so new eruptions must have started after the visible photo was taken.

Answer: B Chapter Review Questions 1) Briefly describe how the differences in composition between the jovian planets can be traced to their formation.

2) Why is Jupiter so much more dense than Saturn? Could a planet be smaller in size than Jupiter but greater in mass?

3) Briefly describe the interior structure of Jupiter and explain why it is layered in this way. How do the interiors of the other jovian planets compare to that of Jupiter?

4) Why does Jupiter have so much internal heat? What generates internal heat on other jovian planets?

5) Briefly describe Jupiter's atmospheric structure and cloud layers. How do the structures and clouds differ on the other jovian planets?

6) How do clouds contribute to Jupiter's colors? Why are Saturn's colors more subdued? Why are Uranus and Neptune blue?

7) Briefly describe Jupiter's weather patterns. What is the Great Red Spot?

8) Why does Jupiter have such a strong magnetic field? Describe a few features of Jupiter's magnetosphere and compare it to the magnetospheres of the other jovian planets.

9) Briefly describe how we categorize jovian moons by size. What is the origin of most of the medium-size and large moons? What is the origin of many of the small moons?

10) Describe key features of Jupiter's four Galilean moons, and the role of tidal heating and orbital resonances in shaping these features.

11) Describe the atmosphere and surface features of Titan. How is Titan's landscape similar to Earth's? How is it different?

12) Summarize the evidence for and some of the mysteries of past or present geological activity on the medium-size moons of Saturn and Uranus.

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13) Why do we think Triton is a captured moon? How might its capture be relevant to its geological activity? 14) Briefly explain why icy moons can have active geology at much smaller sizes than rocky worlds. 15) What are planetary rings made of, and how do they differ among the four jovian planets? Briefly describe the effects of gap moons and orbital resonances on ring systems. 16) Explain why we think that ring particles must be replenished over time, and where we think ring particles come from.

Surprising Discoveries?

Suppose someone claimed to make the following discoveries. (These are not real discoveries.) In light of what you've learned in this chapter, decide whether each discovery should be considered reasonable or surprising. Explain your reasoning.

17) Saturn's core is pockmarked with impact craters and dotted with volcanoes erupting lava. 18) Neptune's deep blue color is not due to methane, as previously thought, but instead is due to its surface being covered with an ocean of liquid water. 19) A jovian planet in another star system has a moon as big as Mars. 20) A planet orbiting another star is made primarily of hydrogen and helium and has approximately the same mass as Jupiter but is the same size as Neptune. 21) A previously unknown moon orbits Jupiter outside the orbits of other known moons. It is the smallest of Jupiter's moons but has several large, active volcanoes. 22) A previously unknown moon orbits Neptune in the planet's equatorial plane and in the same direction that Neptune rotates, but it is made almost entirely of metals such as iron and nickel. 23) An icy, medium-size moon orbits a jovian planet in a star system that is only a few hundred million years old. The moon shows evidence of active tectonics. 24) A jovian planet is discovered in a star system that is much older than our solar system. The planet has no moons but has a system of rings as spectacular as the rings of Saturn. 25) Future observations discover rainfall of liquid water on Titan. 26) During a future mission to Uranus, scientists discover that it is orbited by another 20 previously unknown moons.

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Quick Quiz 27) Which lists the jovian planets in order of increasing distance from the Sun? A) Jupiter, Saturn, Uranus, Pluto B) Saturn, Jupiter, Uranus, Neptune C) Jupiter, Saturn, Uranus, Neptune Answer: No Correct Answer Was Provided. 28) Why does Neptune appear blue and Jupiter red? A) Neptune is hotter, which gives bluer thermal emission. B) Methane in Neptune's atmosphere absorbs red light. C) Neptune's air molecules scatter blue light, much as Earth's atmosphere does. Answer: No Correct Answer Was Provided. 29) Why is Jupiter denser than Saturn? A) It has a larger proportion of rock and metal. B) It has a larger proportion of hydrogen. C) Its higher mass and gravity compress its interior. Answer: No Correct Answer Was Provided. 30) Some jovian planets give off more energy than they receive because of A) fusion in their cores. B) tidal heating. C) ongoing contraction or differentiation. Answer: No Correct Answer Was Provided. 31) The main ingredients of most satellites of the jovian planets are A) rock and metal. B) hydrogen compound ices. C) hydrogen and helium. Answer: No Correct Answer Was Provided. 32) Why is Io more volcanically active than our moon? A) Io is much larger. B) Io has a higher concentration of radioactive elements. C) Io has a different internal heat source. Answer: No Correct Answer Was Provided. 33) What is unusual about Triton? A) It orbits its planet backward. B) It does not keep the same face toward its planet. C) It is the only moon with its own rings.

Answer: No Correct Answer Was Provided.

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34) Which moon shows evidence of rainfall and erosion by some liquid substance?

A) Europa B) Titan C) Ganymede Answer: No Correct Answer Was Provided.

35) Saturn's many moons affect its rings through A) tidal forces.

B) orbital resonances.

C) magnetic field interactions.

Answer: No Correct Answer Was Provided.

36) Saturn's rings A) have looked basically the same since they formed along with Saturn.

B) were created long ago when tidal forces tore apart a large moon.

C) are continually supplied with new particles by impacts with small moons.

Answer: No Correct Answer Was Provided.

Inclusive Astronomy Use these questions to reflect on participation in science.

37) Group Discussion: JUICE and International Collaboration.

The European Space Agency's JUICE (for Jupiter Icy Moons Explorer) mission is designed to explore Jupiter's largest icy moons and to assess their potential for hosting life. a) Working independently, find some background onJUICE the mission. List its main science objectives and dates currently planned for its launch and its arrival at Jupiter. b) The European Space Agency has 22 member nations that are providing the bulk of the funding for the mission. Should the funding provided by each nation be a factor in determining who gets to analyze the data? For example, should scientists from nations that provided more funding get access to the data before the data are released to other scientists? c) The European Space Agency ultimately plans to share data from the JUICE mission widely, but other nations–particularly those in the developing world–may not have the financial resources to support their scientists in analyzing mission data. Should the European Space Agency try to support data analysis by scientists from nations that did not contribute to the mission funding? If so, how? If not, why not? d) Suppose that the mission finds valuable mineral resources on some of these moons. Who should own mineral rights to these resources? Why? The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

38) Europan Ocean.Scientists strongly suspect that Europa has a subsurface ocean, even though we cannot see through the surface ice. Briefly explain why scientists think the ocean exists. Is this "belief" in a Europan ocean scientific? Explain.

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39) Breaking the Rules. As discussed in Chapter 9, the geological "rules" for the terrestrial worlds tell us that a world as small as Io should not have any geological activity. However, Voyager images of Io's volcanoes proved that the old "rules" had been wrong. Based on your understanding of the nature of science [Section 3.4], do you think this should be seen as a failure in the process of science? Defend your opinion. 40) Jovian Planet Mission. We can study terrestrial planets up close by landing on them, but jovian planets have no surfaces to land on. Suppose that you were in charge of planning a long- term mission to "float" in the atmosphere of a jovian planet. Describe the technology you would use and how you would ensure survival for any people assigned to this mission. 41) Jovian Moon Mission. Suppose you could choose any one jovian moon to visit. Which one would you pick, and why? What dangers would you face in your visit to this moon? What kinds of scientific instruments would you want to bring along for studies? 42) Unanswered Questions. Choose one unanswered question about one of the jovian planets or its moons.

Write a few paragraphs discussing the question and the specific types of evidence we would need to answer it. 43) Group Activity: Comparing Jovian Moons. Compare the moons of Jupiter, drawing on the data in Appendix E. Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39. a) Collect data on Jupiter's four largest moons from Table E.2 in Appendix E and determine which moon has the greatest density. b) Use Table E.2 to determine what other solar system moon most resembles the moon from part a in mass, radius, and density. c) Propose a hypothesis about the composition of the moon from part a, based on its resemblance to the moon from part b, and examine potential concerns about the viability of the hypothesis. d) Use Table E.2 to determine whether there is a trend in density with orbital distance among the major moons of Jupiter; briefly describe any trends. e) Suggest a hypothesis that accounts for any trend found in part d, and discuss potential concerns about the hypothesis. f) Develop and describe an experiment that could test the hypotheses in parts c and e.

Investigate Further

44) The Importance of Rotation. Suppose the material that formed Jupiter came together without any rotation so that no "jovian nebula" formed and the planet today wasn't spinning. How else would the jovian system be different? Think of as many effects as you can, and explain each in a sentence.

45) The Great Red Spot. Based on the infrared and visible images in Figure 11.9, is Jupiter's Great Red Spot warmer or cooler than nearby clouds? Is it higher or lower in altitude than the nearby clouds? Explain.

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46) Comparing Jovian Planets. You can do comparative planetology armed only with a telescope and an understanding of gravity. a) The small moon Amalthea orbits Jupiter at about the distance in kilometers at which Mimas orbits Saturn, yet Mimas takes almost twice as long to orbit. From this observation, what can you conclude about how Jupiter and Saturn differ? Explain. b) Jupiter and Saturn are not very different in radius. When you combine this information with your answer to part a, what can you conclude? Explain.

47) Minor Ingredients Matter. Suppose the jovian planets' atmospheres were composed only of hydrogen and helium, with no hydrogen compounds at all. How would the atmospheres be different in terms of clouds, color, and weather? Explain.

48) Galilean Moon Formation. Look up the densities of Jupiter's four Galilean moons in Appendix E, and notice that they follow a trend with distance from Jupiter. Based on what you've learned about condensation in the solar nebula, can you suggest a reason for this trend among the Galilean moons? Next, compare the densities of the moons with the planetary densities in Table E.1. Based on the comparison, do you think it was as hot toward the center of the nebula surrounding Jupiter as it was at the center of the solar nebula? Explain.

49) Super Jupiter. Suppose that the solar wind had not cleared the solar nebula until much later in our solar system's history, so that Jupiter accumulated 40 times as much mass as it actually has today. a) Make a sketch showing how the interior layers of this "Super Jupiter" would compare to the interior layers of the real Jupiter shown in Figure 11.4. b) How would you expect the cloud layers and colors to differ on Super Jupiter? Explain. c) How would you expect the wind speeds to be different on Super Jupiter? Explain. d) How would you expect the magnetic field to be different on Super Jupiter? Explain. e) Do you think Super Jupiter would have more or less excess heat than the real Jupiter? Explain.

50) Observing Project: Jupiter's Moons. Using binoculars or a small telescope, view the moons of Jupiter. Make a sketch of what you see, or take a photograph. Repeat your observations several times (nightly, if possible) over a period of a couple of weeks. Can you determine which moon is which? Can you measure the moons' orbital periods? Can you determine their approximate distances from Jupiter? Explain.

51) Observing Project: Saturn's Rings. Using binoculars or a small telescope, view the rings of Saturn. Make a sketch of what you see, or take a photograph. What season is it in Saturn's northern hemisphere? How far do the rings extend above Saturn's atmosphere? Can you identify any gaps in the rings? Describe any other features you notice.

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Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

52) Disappearing Moon.Io loses about a ton (1000 kilograms) of sulfur dioxide per second to Jupiter's magnetosphere. a) At this rate, what fraction of its mass would Io lose in 4.5 billion years? b) Suppose sulfur dioxide currently makes up 1% of Io's mass. When will Io run out of this gas at the current loss rate?

53) Ring Particle Collisions. Each ring particle in the densest part of Saturn's rings collides with another about every 5 hours. If a ring particle survived for the age of the solar system, how many collisions would it undergo?

54) Prometheus and Pandora. These two moons orbit Saturn at 139,350 and 141,700 kilometers, respectively. a) Using Newton's version of Kepler's third law, find their two orbital periods. Find the percent difference in their distances from Saturn and in their orbital periods. b) Consider the two in a race around Saturn: In one Prometheus orbit, how far behind is Pandora (in units of time)? In how many Prometheus orbits will Pandora have fallen behind by one of its own orbital periods? Convert this number of periods back into units of time. This is how often the satellites pass by each other.

55) Orbital Resonances. Using the data in Appendix E, identify the orbital resonance relationship between Titan and Hyperion. (Hint: If the orbital period of one were 1.5 times the orbital period of the other, we would say that they were in a 3:2 resonance.) Which medium-size moon is in a 2:1 resonance with Enceladus?

56) Titanic Titan. What is the ratio of Titan's mass to that of the other satellites of saturn whose masses are listed in Appendix E? Calculate the strength of gravity on Titan compared to that on Mimas. Comment on how this affects the possibility of an atmosphere on each.

57) Titan's Evolving Atmosphere. Titan's exosphere lies nearly 1400 kilometers above its surface.

What is the escape velocity from this altitude? What is the thermal speed of a hydrogen atom at the exospheric temperature of about 200 K? Use these answers(and the method of Mathematical Insight 10.2) to comment on whether thermal escape of hydrogen is likely to be important for Titan.

58) Saturn's Thin Rings. Saturn's ring system is more than 270,000 kilometers wide and only a few tens of meters thick; let's assume it is 50 meters thick for this problem. Assuming the rings could be shrunk down so that their diameter was the width of a dollar bill (6.6 cm), how thick would the rings be? Compare your answer to the actual thickness of a dollar bill (0.01 cm).

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The Cosmic Perspective, 9e (Bennett et al.)

Chapter 12 Asteroids, Comets, and Dwarf Planets Section 12.1 1) How can you identify an asteroid in a long exposure taken of stars through a telescope?

(Assume the telescope is tracking the sky with Earth's rotation, so that stars appear as points of light.)

A) The asteroid will be much brighter than the surrounding stars.

B) The asteroid will be much dimmer than the surrounding stars.

C) The asteroid will appear as a streak because of its motion relative to the stars.

D) The asteroid will have a noticeable circular disk, rather than being just a point of light like the stars.

E) The asteroid will be recognizable by its long, fuzzy tail.

Answer: C 2) How can asteroids be distinguished from stars in telescope observations?

A) Asteroids move relative to the stars.

B) Asteroids are much dimmer than stars.

C) Asteroids are much redder than stars.

D) Asteroids are much brighter than stars.

E) Asteroids are not spherical.

Answer: A 3) Which of the following statements about comets and asteroids is true?

A) Only asteroids collide with Earth.

B) Comets are balls of ice and dust.

C) Most of the trillions of comets in our solar system have tails.

D) All asteroids lie in the asteroid belt between Mars and Jupiter.

Answer: B 4) What do asteroids and comets have in common?

A) They are leftover planetesimals from the era of planetary formation.

B) They all formed beyond the frost line of the early solar system.

C) They have very similar compositions of ice and rock.

D) They are all much smaller than any moons.

Answer: A 5) An icy leftover planetesimal orbiting the Sun is called a(n) A) comet.

B) moon.

C) asteroid.

D) meteorite.

Answer: A

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6) According to the nebular theory, what are the comets and asteroids? A) chunks of rock or ice that condensed long after the planets had formed B) chunks of rock or ice that have been expelled from the planets by volcanoes C) the shattered remains of collisions between moons D) the shattered remains of collisions between planets E) leftover planetesimals that never accreted into planets Answer: E 7) Why do asteroids and comets differ in composition? A) Asteroids formed inside the frost line, while comets formed outside. B) Asteroids and comets formed at different times. C) Comets formed from the jovian nebula, while asteroids did not. D) Comets are much larger than asteroids. E) Asteroids are much larger than comets. Answer: A 8) How do comets differ from asteroids? A) Comets contain much larger proportions of ice than asteroids. B) Comets contain much smaller proportions of ice than asteroids. C) Comets are much larger in size than asteroids. D) Comets are much smaller in size than asteroids. Answer: A 9) Can an asteroid also be a dwarf planet? A) No; dwarf planets have different compositions from asteroids. B) No; asteroids are too big to be considered "dwarfs." C) Yes, if the asteroid is large enough for its gravity to have made it round. D) Yes, all asteroids are considered to be dwarf planets. Answer: C 10) A typical "shooting star" during a meteor shower is caused by a ________ entering Earth's atmosphere. A) boulder-size particle from an asteroid B) boulder-size particle from a comet C) pebblesize particle from an asteroid D) pebble-size particle from a comet E) microscopic particle of interstellar dust Answer: D 11) When you see the bright flash of a meteor, what are you actually seeing? A) a star that has suddenly shot across the sky B) a bright star moving quickly past our solar system C) emission of visible light from a particle that has not yet entered Earth's atmosphere D) the flash that occurs when a speeding rock from space hits the ground E) the glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere Answer: E

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12) What is a meteorite?

A) a streak of light caused by a star moving across the sky B) a streak of light caused by a small particle from space burning up in Earth's atmosphere C) a fragment of rock that has fallen to Earth's surface from space D) a small moon that orbits one of the jovian planets E) a comet that burns up in Earth's atmosphere Answer: C 13) Why don't most of the particles that make meteors actually reach the surface of Earth?

A) They are too small and burn up in the atmosphere.

B) They reflect off the atmosphere and return to space.

C) They are too small and are slowed to a stop in the atmosphere.

D) They are deflected by the solar wind.

E) They are deflected by the gravity of the Moon.

Answer: A 14) What do we call a small piece of solar system debris that has fallen to the surface of Earth?

A) Iridium B) A comet C) A meteor D) A meteorite E) A shooting star Answer: D 15) Which of the following would be the strongest clue that a rock you have found is a meteorite rather than a terrestrial rock?

A) It contains a lot of iron.

B) It is dark colored.

C) It contains elements and isotopes in proportions that are rare on Earth but common in asteroids.

D) It is too heavy for you to hold in your hand.

Answer: C Section 12.2 1) How does the largest asteroid, Ceres, compare in size to other solar system worlds?

A) It is larger than the planet Mars.

B) It is larger than our Moon but smaller than Mercury.

C) It is larger than Mercury but smaller than Mars.

D) It is about a quarter the diameter of our Moon.

E) It is about the size of the two moons of Mars.

Answer: D

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2) If we know the size of an asteroid, how can we determine its density?

A) comparing its reflectivity to the amount of light it reflects B) looking for brightness variations as it rotates C) determining its mass from its gravitational pull on a spacecraft, satellite, or planet D) radar mapping E) spectroscopic imaging Answer: C 3) Why aren't small asteroids spherical in shape?

A) The strength of gravity of small asteroids is less than the strength of the rock.

B) Small asteroids have odd shapes because they were all chipped off larger objects.

C) Large asteroids became spherical because many small collisions chipped off pieces until only a sphere was left; this did not occur with small asteroids.

Answer: A 4) Which of the following best explains the origin of metal-rich meteorites?

A) They are leftover chunks of rock from the earliest period in the formation of the solar system.

B) They are fragments of comets rather than of asteroids.

C) They are fragments of the core of an asteroid that was shattered by a collision.

D) They are fragments of rock chipped off the planet Mercury.

E) They are fragments of rock chipped off the planet Mars.

Answer: C 5) Which of the following best explains the origin of primitive meteorites?

A) They are leftover chunks of rock from the earliest period in the formation of the solar system.

B) They are fragments of comets rather than of asteroids.

C) They are fragments of an asteroid that was shattered by a collision.

D) They are fragments of rock chipped off the planet Mercury.

E) They are fragments of rock chipped off the planet Mars.

Answer: A 6) How can meteorites from the Moon or Mars have made it to Earth?

A) Impacts on those worlds blasted rocks into space that eventually fell to Earth.

B) Those worlds spin rapidly enough to have sent some rocks from their surfaces into space.

C) The meteorites from the Moon and Mars were never actually part of those worlds; they are just rocks that formed in the same vicinities of the solar system.

D) The solar wind gradually blew material off of the surfaces of these worlds, and once in space it collected together to make the meteorites.

Answer: A 7) Why are collisions between asteroids in the asteroid belt rare?

A) The average distance between asteroids is millions of kilometers.

B) All asteroids orbit in perfect circular orbits at the same speed.

C) Jupiter's gravity keeps asteroids apart.

D) The gas surrounding the asteroids help them repel each other before colliding.

E) There are only a few asteroids in the solar system.

Answer: A

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8) The total mass of all the asteroids in the asteroid belt combined is A) less than that of any terrestrial planet.

B) about the same as that of Earth.

C) about twice that of Earth.

D) about the same as that of Jupiter.

E) more than that of all the planets combined.

Answer: A 9) If all of the asteroids in the solar system were gathered into a single object, how big would it be once gravity compressed it?

A) about half the diameter of Earth's Moon B) about the size of Earth's Moon C) about the size of the Earth D) about the size of a Neptune Answer: A 10) Where are the Trojan asteroids found?

A) orbiting Jupiter B) along Jupiter's orbit, 60° ahead of and behind Jupiter C) in the center of the asteroid belt D) on orbits that cross Earth's orbit E) on orbits that cross Mars's orbit Answer: B 11) How do we know that there are large gaps in the average distances of asteroids from the Sun (within the asteroid belt)?

A) We can see the gaps through telescopes.

B) We can identify the gaps by looking for stellar occultations in which an asteroid passed in front of a star as seen from Earth.

C) We have not actually detected any gaps, but theory says they must exist.

D) We know the gaps must be present to explain how our spacecraft have successfully navigated the asteroid belt without suffering collisions.

E) We notice gaps on graphs showing the distribution of asteroids with different orbital periods.

Answer: E 12) What causes the large gaps in the asteroid belt (often called Kirkwood gaps)?

A) large asteroids that clear certain regions of the asteroid belt B) tidal forces from Jupiter C) tidal forces from the Sun D) orbital resonances with Jupiter E) the competing gravitational tugs of Mars and Jupiter Answer: D

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13) Gaps in the asteroid belt occur at distances where A) the density of asteroids was once so high that collisions pulverized the asteroids into dust.

B) the period of an orbiting asteroid would be a simple fraction (like 1/3 or 1/4) of Jupiter's orbital period.

C) the period of an orbiting asteroid would be the same as Jupiter's orbital period.

D) the period of an orbiting asteroid would be the same as Mars's orbital period.

E) the orbit would take the asteroid beyond the "frost line" in the solar system.

Answer: B 14) This diagram shows the positions of about 150,000 asteroids on a single night.

What would be different if this figure were drawn accurately to scale?

A) The dots that represent individual asteroids would have to be much smaller.

B) The dots that represent individual asteroids would overlap each other.

C) The dots should be farther from the Sun. Answer: A

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15) According to the nebular theory, what is the asteroid belt?

A) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula.

B) It consists of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.

C) It consists of objects that fragmented from the Sun during a catastrophic collision early in the formation of the solar system.

D) It consists of planetesimals that formed between the orbits of Mars and Jupiter but which Jupiter's gravity prevented from becoming a planet.

E) It consists of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.

Answer: D Section 12.3 1) Comets are largely made out of A) rock and ice.

B) hydrogen gas.

C) rock.

D) hydrogen compounds.

E) metal.

Answer: A 2) According to the nebular theory, how did the Kuiper belt form?

A) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula.

B) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.

C) It consists of objects that fragmented from the Sun during a catastrophic collision early in the formation of the solar system.

D) It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet.

E) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.

Answer: B

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3) According to the nebular theory, how did the Oort cloud form?

A) It is material left over from the interstellar cloud that never contracted with the rest of the gases to form the solar nebula.

B) It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.

C) It consists of objects that fragmented from the Sun during a catastrophic collision early in the formation of the solar system.

D) It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet.

E) It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.

Answer: E 4) Which of the following is furthest from the Sun? A) Pluto B) Neptune C) an asteroid in the asteroid belt D) a comet in the Kuiper belt E) a comet in the Oort cloud Answer: E 5) When do comets have tails?

A) when they are relatively close to the Sun B) when they are close to a massive planet like Jupiter C) only after a collision with a smaller object D) when they are young E) Comets always have tails.

Answer: A 6) When a comet is in the inner solar system, what part of it points most directly away from the Sun? A) the denser side of its nucleus B) its coma C) jets of gas emerging from its nucleus D) its tail Answer: D 7) A comets tails (especially its plasma tail) generally point A) away from the Sun. B) toward the Sun. C) directly behind the comet along its orbit.

D) directly ahead of the comet along its orbit.

E) toward the location where the comet's inward trajectory first began.

Answer: A

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8) Where did comets that are now in the Oort cloud originally form?

A) near the jovian planets B) outside Neptune's orbit C) inside Jupiter's orbit D) within the solar nebula, but far outside the orbit of Pluto Answer: A 9) Where did comets that are now in the Kuiper belt originally form?

A) in the asteroid belt B) inside Jupiter's orbit C) between the orbits of Jupiter and Neptune D) near the distance at which they orbit today E) in the Oort cloud Answer: D 10) A comet that has an extremely elliptical orbit most likely came from A) the asteroid belt.

B) the Kuiper belt.

C) the Oort cloud.

D) the Trojan asteroids.

E) outside the solar system.

Answer: C 11) Approximately how many comets are thought to be in the Oort cloud?

A) a thousand B) a million C) a billion D) a trillion E) a quintillion Answer: D 12) What evidence led astronomers to conclude that the Oort cloud is a spherical distribution of comets?

A) the observation that comets enter the solar system from random directions B) direct observation of comets orbiting the sun in the Oort cloud C) Astronomers did not draw that conclusion; the Oort cloud is shaped like a flat ring in the same plane as the planets.

D) observations of comets getting flung out by Jupiter's gravity in random directions Answer: A

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Section 12.4 1) Pluto's composition is most similar to that of a A) terrestrial planet.

B) comet.

C) star.

D) jovian planet.

Answer: B 2) What is Charon?

A) Pluto's largest moon B) the largest known asteroid C) the largest known comet D) one of the Galilean moons of Jupiter E) a moon of Neptune Answer: A 3) Based on its orbit, Pluto is a large member of A) the asteroid belt.

B) the Kuiper belt.

C) the Oort cloud.

D) the moon system around Neptune.

E) an extrasolar planetary system.

Answer: B 4) Will Pluto eventually collide with Neptune?

A) no, because Pluto's orbit is completely outside Neptune's orbit B) no, because Pluto's orbit is completely inside Neptune's orbit C) no, because Pluto's orbit never comes anywhere close to Neptune's orbit D) no, because the two planets have an orbital resonance that prevents them from getting close to each other E) Yes, it's likely that they will eventually.

Answer: D 5) How is Pluto's moon system thought to have formed?

A) from a giant impact B) by gravitational capture of passing asteroids C) by gravitational capture of passing comets D) by stealing them during a close encounter with Neptune Answer: A

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6) What surprising discovery did the New Horizons spacecraft make during its 2015 flyby of Pluto?

A) Pluto has the largest known volcano in the solar system.

B) Pluto's surface consists mostly of rocky material.

C) Pluto's surface shows signs of very recent geological activity.

D) Pluto is an escaped moon of Neptune.

E) all of the above Answer: C 7) What is the likely cause of the haze seen in photographs of Pluto's atmosphere taken by the New Horizons spacecraft?

A) ice particles erupting from geysers on Pluto's surface B) hydrocarbon molecules captured from passing comets C) condensation on the camera lens D) ultraviolet solar radiation breaking down methane and nitrogen molecules Answer: D Section 12.5 1) Why was the Shoemaker-Levy 9 impact on Jupiter so important to astronomers?

A) It dredged up material that allowed us to learn about Jupiter's interior.

B) It wiped out the dinosaurs.

C) It was the first clear evidence that impacts really occur.

D) It confirmed our theory of solar system formation.

E) It was the first event in modern history that was brighter than the full moon in the sky.

Answer: A 2) On average, how often do impactors about 10 km in size, large enough to produce mass extinction, hit Earth?

A) once every century B) once every thousand years C) once every million years D) once every hundred million years E) once in Earth's history Answer: D 3) Which of the following was the first strong evidence for an asteroid impact being the cause of the extinction of the dinosaurs 65 million years ago (as well as 75% of all species alive at the time)?

A) a worldwide layer rich in the element iridium that dates to that time B) the discovery of asteroid fragments in dinosaur bones dating to that time C) the fact that dinosaurs appear to have gone abruptly extinct at about that time D) careful studies of lunar craters suggesting an unusually large number of impact at that time Answer: A

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4) How can a large asteroid impact in one spot on Earth affect the climate of the entire Earth?

A) The impact releases greenhouse gases that immediately make Earth warmer.

B) The impact blasts a hole through Earth's mantle, allowing hot metal from the core to rise up and heat the world.

C) The impact blasts debris into Earth's atmosphere that blocks sunlight, making Earth's surface cooler.

D) The impact tears a hole in Earth's atmosphere, allowing heat energy to escape and thereby cooling our planet.

Answer: C 5) A crater of the correct age to be from the impact thought to have caused the extinction of the dinosaurs was found in A) the Yucatán Peninsula in Mexico.

B) Arizona.

C) Northern Africa.

D) Chelyabinsk, Russia.

E) Tunguska, Siberia.

Answer: A General Chapter Questions 1) Kepler's Third law relates a planet's orbital period and its average distance from the Sun (p2 = a3 ). If a new comet were discovered with an average distance from the Sun of 100 AU, its period would be A) 1000 years.

B) 10,000 years.

C) 150 years.

D) 1 million years.

E) not enough information to say.

Answer: A 2) If a major asteroid collision in the asteroid belt occurs once every 100,000 years on average, then how many major collisions have occurred over the approximately 4.5 billion year history of the solar system?

A) about 45,000 B) about 4.5 million C) about 4.5 billion D) about 4500 Answer: A

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3) Asteroid impacts large enough to cause mass extinction on Earth occur roughly once every 100 million years. Use that fact to estimate the probability that such an event will occur in your lifetime, which you can take to be approximately 100 years. What's your estimate of that probability? A) 1 in 100,000,000 B) 1 in 10,000 C) 1 in 1,000,000 D) 1 in 100,000,000,000 Answer: C 4) Assume that the average rate of 1-km-sized asteroids hitting the Earth is about 1 every million years. The chance of the Earth being hit by a 1km-sized asteroid in the next 100 years is about A) one in 100 million. B) one in ten thousand. C) inevitable, it has to happen sometime. D) zero. E) one in a million. Answer: B Short Answer Questions 1) Describe at least three ways in which our solar system would be different if orbital resonances had never been important. Answer: There are many possible answers. For example, without orbital resonances: (1) Instead of the asteroid belt, the planetesimals in that region might have accreted into a single planet between Mars and Jupiter. (2) Comet orbits would not be nudged, so comets would not collide as frequently with Earth. (3) From the previous two ideas, Earth would not have been as heavily impacted. (4) Earth would not have received as many volatiles from the outer solar system. (5) Saturn's rings would not be broken into rings and gaps. (6) The asteroid belt would not have gaps. (7) Kuiper belt objects would not clump into orbital groups. (8) Pluto and other Kuiper belt objects would not be prevented from colliding with Neptune. (9) Io, Europa, and Ganymede would not be geologically active. 2) Describe some ways in which a meteorite can be distinguished from a terrestrial rock. Answer: Meteorites are usually covered with a dark, pitted crust from their fiery passage through the atmosphere. Some contain enough metal to attract a magnet hanging on a string. The isotopic ratios in meteorites differ from terrestrial rocks and they may also have a higher abundance of rare elements such as iridium than terrestrial rocks. 3) How are asteroid masses measured?

Answer: Asteroid masses can be determined only in those cases where they have a moon or a spacecraft pass close by and feel its gravitational influence. The mass is then determined from Newton's version of Kepler's third law.

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4) Why is the Kuiper belt flat but the Oort cloud spherical?

Answer: The difference is that the comets in the Kuiper belt have not been scattered out by gravitational interactions with giant planets. Kuiper belt comets formed beyond the orbit of Neptune in the flattened solar nebula and their orbits have not been greatly changed. Oort cloud comets, however, formed within the orbit of the jovian planets and have been scattered out (or impacted other bodies in the solar system). The scattering was random so the orbits are in every direction and inclination, resulting in a spherical Oort cloud.

Reading Quiz Questions 1) Which of the following best describes the primary difference between asteroids and comets?

A) Asteroids are rocky and comets are ice-rich.

B) Comets are much larger than asteroids.

C) Comets always have tails and asteroids never have them.

D) Comets tend to orbit the Sun in the inner solar system, while asteroids tend to orbit much farther away.

Answer: A 2) What is Eris?

A) an icy object that orbits in the Kuiper belt and is more massive than Pluto B) the largest known asteroid C) a moon of Pluto D) an extrasolar planet ejected by another solar system and captured by ours Answer: A 3) A typical meteor is created by a particle about the size of a A) pea.

B) baseball.

C) car.

D) basketball.

Answer: A 4) A rock found on Earth that crashed down from space is called a(n) A) meteorite.

B) meteor.

C) asteroid.

D) impact.

Answer: A 5) Which statement about asteroids is not true?

A) If we could put all the asteroids together, they would make an object about the size of Earth.

B) Many but not all orbit the Sun in the asteroid belt.

C) Some are more like loosely bound piles of rubble than solid chunks of rock.

D) Most asteroids are not spherical in shape.

Answer: A

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6) The asteroid belt is located A) between the orbits of Mars and Jupiter.

B) between the orbits of Earth and Mars.

C) between the orbits of Jupiter and Saturn.

D) beyond the orbit of Neptune.

Answer: A 7) What is Ceres?

A) the largest known asteroid B) the first asteroid to have been visited by a spacecraft C) the largest moon of Pluto D) a dwarf planet that orbits the Sun in the Kuiper belt beyond the orbit of Pluto Answer: A 8) What do we mean by a primitive meteorite?

A) a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula almost 4.6 billion years ago B) a meteorite that was discovered by primitive people C) a type of meteorite that is made mostly of high-density metals D) a meteorite that fell to Earth at least 4 billion years ago Answer: A 9) Among discovered meteorites, we have found some with all the following origins except A) being a fragment from Comet Halley.

B) being a fragment from the surface of Mars.

C) being a fragment from the surface of the Moon.

D) being a fragment of a shattered asteroid.

Answer: A 10) Which statement is not thought to be true of all comets in our solar system?

A) Comets always have tails.

B) All comets are icy in composition.

C) All comets orbit the Sun. D) All comets are leftover planetesimals that originally condensed beyond the frost line in the solar nebula.

Answer: A 11) When a comet is within the inner solar system, its visible tails point A) away from the Sun B) opposite the direction the comet is moving in its orbit C) perpendicular to the ecliptic plane D) always almost due north E) in the direction the comet is moving in its orbit Answer: A

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12) When a comet passes near the Sun, part of it takes on the appearance of a large, bright ball from which the tail extends. This part is called the A) coma.

B) nucleus.

C) plasma tail.

D) Oort core.

Answer: A 13) Comets with orbits that take them through the inner solar system shed sand- to pebble-size particles that then follow the comet around its orbit. How do these particles affect Earth?

A) They are the particles that produce meteor showers.

B) They are the particles that produce the lights of auroras.

C) They have been implicated in mass extinctions, including the extinction of the dinosaurs.

D) On rare occasions, they can blanket our entire atmosphere with dust.

Answer: A 14) Which of the following best distinguishes the Kuiper belt from the Oort cloud?

A) Both are made up of many comets, but Kuiper belt comets orbit within a donut-shaped region just beyond the orbit of Neptune, while Oort cloud comets orbit much farther from the Sun and can have orbits of all inclinations.

B) The Kuiper belt is made up of rocky asteroids, while the Oort cloud is made up of icy comets.

C) The Kuiper belt is located between the orbits of Mars and Jupiter, while the Oort cloud lies far beyond Neptune.

D) The Kuiper belt consists of only of very large comets (similar in size to Pluto), while the Oort cloud consists only of very small comets.

Answer: A 15) Which of the following correctly states the number of comets that scientists estimate to be located in the Oort cloud and the number that have actually been observed in the Oort cloud (with telescopes)?

A) estimated number in Oort cloud: 1 trillion observed in Oort cloud: zero B) estimated number in Oort cloud: 1 million observed in Oort cloud: 1,000 C) estimated number in Oort cloud: 100,000 observed in Oort cloud: 50 D) estimated number in Oort cloud: 1 billion observed in Oort cloud: 10,000 Answer: A 16) According to current evidence, Pluto is best described as A) a large member of the Kuiper belt.

B) a terrestrial planet that is surprisingly far from the Sun. C) a small jovian planet.

D) an escaped moon of Jupiter or Saturn.

Answer: A

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17) What is Charon?

A) the largest of Pluto's moons B) the largest known Kuiper belt comet C) the largest known asteroid D) a captured moon of Neptune Answer: A 18) Which of the following was a new discovery about Pluto by the New Horizons mission?

A) evidence of recent geological activity B) the existence of moons orbiting Pluto C) the fact that Pluto has an ice-rich composition D) the fact that Pluto is less massive than Eris Answer: A 19) What do we mean by a mass extinction?

A) the extinction of a large fraction of the world's plant and animal species in a relatively short period of time B) the extinction of large animals, such as dinosaurs C) an extinction caused by the impact of an asteroid or comet D) the extinction of any species of plant or animal that has mass Answer: A 20) If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because A) of global climate effects initiated by dust and smoke that entered the atmosphere after the impact.

B) of injuries suffered from direct hits of pieces of the asteroid or comet.

C) radiation from iridium in the asteroid caused the dinosaurs to die of cancer.

D) the impact caused massive earthquakes worldwide.

Answer: A 21) Objects the size of the one that exploded over Chelyabinsk (Russia), causing significant damage and injuries to more than 1,000 people, probably hit Earth at least A) once a century.

B) once a year.

C) once every 500,000 years.

D) once every 100 million years.

Answer: A Concept Quiz Questions 1) When you see the bright flash of a meteor, what are you actually seeing?

A) the glow of heated air surrounding a small particle as it burns up in our atmosphere B) emission of visible light from a particle that has not yet entered Earth's atmosphere C) a star that has suddenly shot across the sky D) the flash that occurs when a speeding rock from space hits the ground Answer: A

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2) Which of the following statements best describes the size of the largest asteroid, Ceres?

A) a little less than half the diameter of our Moon B) about the size of a terrestrial planet C) smaller than the jovian planets but larger than the terrestrial planets D) no larger than a typical mountain on Earth Answer: A 3) If we could put all the asteroids in the asteroid belt together, their total mass would be A) much less than the mass of Mercury.

B) about the mass of Jupiter.

C) about the mass of Earth.

D) greater than the mass of Earth but less than the mass of Neptune.

Answer: A 4) Why didn't a planet form where the asteroid belt is now located?

A) Gravitational tugs from Jupiter prevented material from collecting together to form a planet.

B) There was not enough material in this part of the solar nebula to form a planet.

C) There was too much rocky material to form a terrestrial planet, but not enough gaseous material to form a jovian planet.

D) The temperature in this portion of the solar nebula was just right to prevent rock from sticking together.

Answer: A 5) Gaps in the asteroid belt (often called Kirkwood gaps) are caused by A) orbital resonances with Jupiter.

B) tidal forces from the Sun. C) tidal forces from Jupiter.

D) the competing gravitational tugs of Mars and Jupiter.

Answer: A 6) How can we determine the reflectivity of an asteroid?

A) by comparing its brightness in visible light to its brightness in infrared light B) by taking a photograph of it C) by measuring its mass and radius D) by where it is located in the asteroid belt Answer: A 7) In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder-size objects. Which of the following real things in our solar system would look most like such science fiction dangers?

A) the rings of Saturn B) the asteroid belt C) the atmosphere of Jupiter D) the Oort cloud Answer: A

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8) Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements must be true?

A) Your meteorite is a fragment from the core of a large asteroid that shattered in a collision.

B) Radiometric dating will show the age of your meteorite to date to the formation of our solar system.

C) Your meteorite was blasted off the surface of Mars by an impact.

D) Your meteorite is a fragment of an object from the Kuiper belt.

Answer: A 9) Which of the following objects are probably not located in the same region of the solar system in which they originally formed?

A) Oort cloud comets B) Kuiper belt comets C) asteroids of the asteroid belt D) Pluto Answer: A 10) Suppose there were no solar wind. How would the appearance of a comet in our inner solar system be different?

A) It would have only one tail instead of two.

B) It would not have a coma.

C) It would not have a nucleus.

D) It would be much brighter in appearance.

Answer: A 11) Suppose we discover a new comet on an orbit that brings it closer to the Sun than Mercury every 125 years. What can we conclude?

A) It has been on its current orbit for only a short time compared to the age of our solar system.

B) It came from the Oort cloud.

C) It came from the Kuiper belt.

D) It has a coma and tail during most of each orbit.

Answer: A 12) When we see a meteor shower, it means that A) Earth is crossing the orbit of a comet.

B) the solar wind is unusually strong.

C) an Earth-approaching asteroid has recently come close to our planet.

D) you should duck and run for cover to avoid being blasted on the head by a rock from space.

Answer: A 13) Why won't Pluto collide with Neptune?

A) Pluto orbits the Sun exactly two times for every three Neptune orbits.

B) Pluto is always much farther from the Sun than Neptune.

C) Pluto's orbit never comes anywhere close to Neptune's orbit.

D) Actually, a collision of the two is inevitable within the next billion years.

Answer: A

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14) What is Pluto's moon Charon thought to have in common with our own Moon? A) It probably formed as a result of a giant impact. B) It has the same basic composition. C) It has the same approximate mass. D) It has the same average density. Answer: A 15) Which of the following is a real piece of evidence (from the New Horizons mission) pointing to recent or ongoing geological activity on Pluto? A) surface regions that suggest glacial movement of frozen ices of nitrogen and methane B) surface regions that show evidence of flooding by liquid water C) crater rims showing evidence of erosion by rainfall D) several towering volcanoes discovered on its surface Answer: A 16) Which of the following is not a piece of evidence supporting the idea that an impact caused the mass extinction that occurred 65 million years ago? A) Fossilized dinosaur bones contain fragments of rock from the impact. B) Unusually large abundances of iridium and other rare metals are found in a layer of clay that dates to 65 million years ago. C) A large impact crater along the coast of Mexico dates to 65 million years ago. D) Grains of quartz formed under high pressure are found in a layer of clay that dates to 65 million years ago. Answer: A 17) Which of the following best describes why scientists seek to identify even small asteroids that could potentially hit Earth? A) to try to prevent an impact that might destroy a town or city B) to try to prevent an impact that might cause the extinction of the human race C) to help us understand the origin of the solar system D) to allow us to capture the asteroids and use them for their resources Answer: A 18) Suppose that large jovian planets had never formed in our solar system. Which of the following would most likely be true? A) Neither the asteroid belt nor Oort cloud would exist. B) Earth would have suffered far fewer impacts. C) There would be a large empty region in our solar system between the orbit of Mars and the Kuiper belt. D) Earth would orbit much closer to the Sun. Answer: A

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Visual Quiz Questions 1) This photo shows Comet Hale-Bopp in the night sky. Suppose you had taken another photograph from the same spot 10 minutes after this photo was taken. How would the scene have appeared at that time?

A) It would have looked virtually the same.

B) We'd still see the same stars, but the comet would be out of sight, having passed below the horizon.

C) We would see lots of smoke coming from the point where the comet crashed into the mountains.

D) We'd still see the same stars, but the comet would have moved far enough so that we'd be able to see only its tails and not its coma above the horizon.

Answer: A

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2) Which photo shows an object that looks most like a typical asteroid?

A)

B)

C)

D)

Answer: A

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3) Each white dot in this figure represents the location of a small body in our solar system. The donut-shaped ring of white dots represents the region of our solar system that we call

A) the asteroid belt.

B) the Kuiper belt.

C) the Oort cloud.

D) the Sun's rings.

Answer: A

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4) This graph shows the number of asteroids with different orbital periods. Notice the gap indicated by the downward-pointing black arrow. What does this graph tell us about this gap?

A) There are few if any asteroids at the indicated orbital period of about 4 years.

B) There are more asteroids concentrated at the orbital period indicated by the arrow than at any other orbital period.

C) Asteroids with an orbital period of about 4 years are all located very close together; so close that collisions occur frequently.

D) There are exactly 495 asteroids with an orbital period of 4 years.

Answer: A

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5) A comet grows tails (plasma tail and dust tail) when it comes close to the Sun. Which of the following diagrams shows a comet's tails correctly oriented as they appear along its orbit?

A)

B)

C)

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D)

Answer: A 6) Each white dot in this figure represents the location of a small body in our solar system. The donut-shaped ring of white dots just beyond Neptune's orbit represents the part of our solar system that we call

A) the asteroid belt.

B) the Kuiper belt.

C) the Oort cloud.

D) the solar nebula.

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7) The following images were all taken by spacecraft. Which one shows a comet?

A)

B)

C)

D)

Answer: A 8) This image shows Pluto photographed by the New Horizonsspacecraft in 2015. What did scientists find most surprising when they saw this image?

A) the smooth areas and other features suggesting relatively recent geological activity B) the round shape C) the presence of numerous impact craters D) the fact that the entire face shown is sunlit in this photo Answer: A

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9) What is the significance of the circular region marked in the image (with location identified on the map)?

A) It outlines the crater from the impact thought to have killed off the dinosaurs.

B) It shows where the coastline of Mexico was located 65 million years ago.

C) It shows the outline of the oldest known impact crater on Earth.

D) Its colors indicate the ocean depth within the circle.

Answer: A

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10) This graph shows the frequency of impacts on Earth by objects of various sizes. According to this graph, objects large enough to cause a mass extinction hit Earth

A) about once every 50 million years.

B) about once every 1,000 years.

C) about once in Earth's history.

D) about once every 500 million years.

Answer: A

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End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

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The graph on the preceding page (Figure 12.33) shows how often impacts occur for objects of different sizes.

The photo shows Comet Tempel 1 moments before the Deep Impact spacecraft crashed into it.

1) Estimate Comet Tempel 1's diameter, using the scale bar in the photo.

Answer: About 5 km, though its unusual shape could lead to answers between 4 and 8 km.

2) According to the graph, how frequently do objects the size of Comet Tempel 1 strike Earth?

A) once in Earth's history B) about once every hundred million years C) about once every million years D) about once every thousand years Answer: B 3) Consider an object twice the size of Comet Tempel 1. What kind of damage would this object cause if it hit our planet?

A) mass extinction B) widespread devastation and climate change C) atmospheric explosion or a small crater Answer: A 4) Meteor Crater in Arizona is about 1.2 kilometers across. According to the graph, about how big was the object that made this crater? (Note: Be sure to read the axis labels carefully.)

A) 1 meter B) 10 meters C) 100 meters D) 1 kilometer Answer: C 5) How often do objects big enough to create craters like Meteor Crater impact Earth?

A) once in Earth's history B) about once every ten thousand years C) about once every few million years D) about once every day, but most burn up in the atmosphere or land in the ocean Answer: B Chapter Review Questions 1) Briefly define asteroid, comet, dwarf planet, meteor, and meteorite. How did the discovery of Eris force astronomers to reconsider the definition of planet?

2) Briefly describe asteroid sizes, shapes, masses, densities, and compositions. How does the total mass of all asteroids compare to the mass of a terrestrial world?

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3) Distinguish between primitive meteorites and processed meteorites in terms of both composition and origin.

4) What do meteorites and spacecraft observations tell us about the geology of asteroids?

5) Where is the asteroid belt located, and why? Explain how orbital resonances with Jupiter affect the asteroid belt.

6) Under what circumstances do we see a comet with a nucleus, coma, and tails? In what direction do the tails point?

7) How are meteor showers linked to comets, and why do they recur at about the same time each year?

8) How do we know the Kuiper belt and Oort cloud exist? Describe each in terms of location, the orbits and number of comets within it, and its likely origin.

9) Briefly describe Pluto and Charon. Why won't Pluto collide with Neptune? How do we think Charon formed?

10) What clues do other Kuiper belt comets offer about the origin of the belt? How is Neptune's moon Triton important to our understanding?

11) Briefly describe how current models explain the origin of the Kuiper belt. What role does planetary migration play?

12) Briefly describe the evidence suggesting that an impact caused the mass extinction that killed off the dinosaurs. How might the impact have led to the mass extinction?

13) How often should we expect impacts of various sizes on Earth? How serious a threat do we face from these impacts?

14) Briefly summarize the role of the jovian planets in shaping the orbits of small bodies in the solar system and in influencing life on Earth.

Surprising Discoveries?

Suppose someone claimed to make the following discoveries. (These are not real discoveries.)

Decide whether each discovery should be considered reasonable or surprising. Explain.

15) A small asteroid that orbits within the asteroid belt has an active volcano.

16) Scientists discover a meteorite that, based on radiometric dating, is 7.9 billion years old.

17) An object that resembles a comet in size and composition is discovered orbiting in the inner solar system.

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18) Studies of a large object in the Kuiper belt reveal that it is made almost entirely of rocky (as opposed to icy) material.

19) Astronomers discover a previously unknown comet that will be brightly visible in our night sky about 2 years from now.

20) A mission to Eris finds that it has lakes of liquid water on its surface.

21) Geologists discover a crater from a 5-kilometer object that impacted Earth more than 100 million years ago.

22) Archaeologists learn that the fall of ancient Rome was caused in large part by an asteroid impact in Asia.

23) In another solar system, astronomers discover an object the size of Earth orbiting its star at the distance of the Kuiper belt.

24) Astronomers discover an asteroid with an orbit suggesting that it will impact Earth in the year 2064.

Quick Quiz

25) The asteroid belt lies between the orbits of A) Earth and Mars.

B) Mars and Jupiter.

C) Jupiter and Saturn.

Answer: No Correct Answer Was Provided.

26) Jupiter nudges the asteroids through the influence of A) tidal forces.

B) orbital resonances.

C) magnetic fields.

Answer: No Correct Answer Was Provided.

27) Can an asteroid be pure metal?

A) No; all asteroids contain rock.

B) Yes; it must have formed where only metal could condense in the solar nebula.

C) Yes; it must be from the core of a shattered asteroid.

Answer: No Correct Answer Was Provided.

28) Did a large terrestrial planet ever form in the region of the asteroid belt?

A) no, because there was never enough mass there B) no, because Jupiter prevented one from accreting C) yes, but it was shattered by a giant impact.

Answer: No Correct Answer Was Provided.

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29) What does Pluto most resemble?

A) a terrestrial planet B) a jovian planet C) a comet Answer: No Correct Answer Was Provided.

30) How big an object causes a typical "shooting star"?

A) a grain of sand or a small pebble B) a boulder C) an object the size of a car Answer: No Correct Answer Was Provided.

31) Which have the most elliptical and tilted orbits?

A) asteroids B) Kuiper belt comets C) Oort cloud comets Answer: No Correct Answer Was Provided.

32) Which are thought to have formed farthest from the Sun? A) asteroids B) Kuiper belt comets C) Oort cloud comets Answer: No Correct Answer Was Provided.

33) About how often does a 1-kilometer object strike Earth?

A) every year B) every million years C) every billion years Answer: No Correct Answer Was Provided.

34) What would happen if a 1-kilometer object struck Earth?

A) It would break up in the atmosphere without causing widespread damage.

B) It would cause widespread devastation and climate change.

C) It would cause a mass extinction.

Answer: No Correct Answer Was Provided.

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Inclusive Astronomy Use these questions to reflect on participation in science.

35) Group Discussion: Who Owns the Asteroids?

Within the next decade or two, it might become profitable for nations or private companies to mine asteroids in pursuit of rare minerals. Several private companies are already laying the groundwork for such mining. a) Gather in small groups (two to four students) and discuss whether nations and/or private companies should be able to claim ownership rights to minerals that they mine from an asteroid and bring to Earth. Make two lists, one of reasons why ownership should be allowed and one of why it shouldn't. b) Debate the pros and cons represented in your two lists and then try to come to a group consensus on whether ownership should be allowed and, if so, what regulations it should be subject to. c) Make a list of ways in which asteroid mining might be used for scientific purposes. If the mining is done for commercial reasons, what obligation should the miners (nations or companies) have to also generate scientific value from their work?

The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

36) The Pluto Debate.Research the decision to demote Pluto to dwarf planet status. In your opinion, is this a good example of the scientific process? Does it exhibit the hallmarks of science described in Chapter 3? Compare your conclusions to opinions you find about the debate, and describe how you think astronomers should handle this or similar debates in the future.

37) Life-or-Death Astronomy. In most cases, the study of the solar system has little direct effect on our lives. But the discovery of an asteroid or comet on a collision course with Earth is another matter. How should the standards for verifiable observations described in Chapter 3 apply in this case? Is the potential danger so great that any astronomer with any evidence of an impending impact should spread the word as soon as possible? Or is the potential for panic so great that even higher standards of verification ought to be applied? What kind of review process, if any, would you set in place? Who should be informed of an impact threat, and when?

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38) Group Activity: Assessing Impact Danger. Work in small groups to assess the risks we face on Earth from meteorite and comet impacts.Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39. a) Consider how you might estimate the chance of human civilization being destroyed by an impact during your lifetime. Determine the kinds of information you would need to come up with an estimate, develop a method for making the estimate, and write down your method. b) Analyze Figure 12.33 and determine whether it contains any of the necessary information. c) Apply your group's method to estimate the probability that civilization will be destroyed by an impact during your lifetime, which you can assume to be 100 years for the purpose of this exercise. d) Estimate the probability that an impact will cause "widespread devastation" somewhere on Earth during your lifetime. e) Finding near-Earth asteroids early greatly increases our chances of deflecting them. Given the probabilities you found in parts c and d and considering the damage these events would cause, decide as a group how much money per year should be spent on finding near-Earth asteroids.

Explain your reasoning.

Investigate Further 39) The Role of Jupiter. Suppose that Jupiter had never existed. Describe at least three ways in which our solar system would be different, and clearly explain why.

40) Life Story of an Iron Atom. Imagine that you are an iron atom in a processed meteorite made mostly of iron. Tell the story of how you got to Earth, beginning when you were part of the gas in the solar nebula 4.6 billion years ago. Include as much detail as possible. Your story should be scientifically accurate but also creative and interesting.

41) Asteroid Discovery. You have discovered two new asteroids and named them Albert and Isaac. Both lie at the same distance from Earth and have the same brightness when you look at them through your telescope, but Albert is twice as bright as Isaac at infrared wavelengths. What can you deduce about the relative reflectivities and sizes of the two asteroids? Which would make a better target for a mission to mine metal? Which would make a better target for a mission to obtain a sample of a carbon-rich planetesimal? Explain.

42) Asteroids vs. Comets. Contrast the compositions and locations of comets and asteroids, and explain in your own words why they have turned out differently.

43) Comet Tails. Describe in your own words why comets have tails. Why do most comets have two distinct visible tails, and why do the tails go in different directions? Why is the third, invisible tail of small pebbles of interest to us on Earth?

44) Oort Cloud vs. Kuiper Belt. Explain in your own words how and why there are two different reservoirs of comets. Be sure to discuss where the two groups of comets formed and what kinds of orbits they travel on.

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45) Rise of the Mammals. Suppose the impact 65 million years ago had not occurred.

How do you think our planet would be different? For example, do you think that mammals still would eventually have come to dominate Earth? Would we be here?

Defend your opinions. 46) Project: Dirty Snowballs. If there is snow where you live or study, make a dirty snowball. (The ice chunks that form behind tires work well.) How much dirt does it take to darken snow? Find out by allowing your dirty snowball to melt in a container and measuring the approximate proportions of water and dirt afterward.

Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

47) Adding Up Asteroids.It's estimated that there are a million asteroids 1 kilometer across or larger. If a million asteroids 1 kilometer across were all combined into one object, how big would it be? How many 1-kilometer asteroids would it take to make an object as large as Earth?

(Hint: You can assume the asteroids are spherical. The expression for the volume of a sphere is πr3, where r is the radius.)

48) Impact Energies. A relatively small impact crater 20 kilometers in diameter could be made by a comet 2 kilometers in diameter traveling at 30 kilometers per second (30,000 m/s). a) Assume that the comet has a total mass of 4.2 × 1012 kilograms. What is its total kinetic energy? (Hint: The kinetic energy is equal to mv2, where m is the comet's mass and v is its speed. If you use mass in kilograms and velocity in m/s, the answer for kinetic energy will have units of joules.) b) Convert your answer from part a to an equivalent in megatons of TNT, the unit used for nuclear bombs. Comment on the degree of devastation the impact of such a comet could cause if it struck a populated region on Earth. (Hint: One megaton of TNT releases 4.2 × 1015 joules of energy.)

49) The "Near Miss" of Toutatis. The 5-kilometer asteroid Toutatis passed a mere 1.5 million kilometers from Earth in 2004. Suppose Toutatis were destined to pass somewhere within 1.5 million kilometers of Earth. Calculate the probability that this "somewhere" would have meant that it slammed into Earth. Based on your result, do you think it is fair to call the 2004 passage a "near miss"? Explain. (Hint: You can calculate the probability by considering an imaginary dartboard of radius 1.5 million kilometers in which the bull's-eye has Earth's radius, 6378 kilometers.)

50) Room to Roam. It's estimated that there are a trillion comets in the Oort cloud, which extends out to about 50,000 AU. What is the total volume of the Oort cloud, in cubic AU? How much space does each comet have in cubic AU, on average? Take the cube root of the average volume per comet to find the comets' typical spacing in AU. (Hints: For the purpose of this calculation, you can assume the Oort cloud fills the whole sphere out to 50,000 AU. The volume of a sphere is given by πr3, where r is the radius.)

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51) Comet Temperatures. Find the "no greenhouse" temperatures for a comet at distances from the Sun of 50,000 AU (in the Oort cloud), 3 AU, and 1 AU(see Mathematical Insight 10.1).

Assume that the comet reflects 3% of the incoming sunlight. At which location will the temperature be high enough for water ice to vaporize (about 150 K)? How do your results explain comet anatomy?

52) Comet Dust Accumulation. A few hundred tons of comet dust are added to Earth daily from the millions of meteors that enter our atmosphere. Estimate the time it would take for Earth to get 0.1% heavier at this rate. Is this mass accumulation significant for Earth as a planet? Explain.

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The Cosmic Perspective, 9e (Bennett et al.)

Chapter 13 Other Planetary Systems Section 13.1 1) About how much brighter is a typical star than the light reflected by a planet orbiting around it?

A) a hundred times brighter B) a thousand times brighter C) ten thousand times brighter D) a million times brighter E) a billion times brighter Answer: E 2) Which of the following makes it very difficult to detect planets around other stars?

A) Planets are constantly orbiting their stars, so we don't know where to point our telescopes to see them.

B) Planets are typically at least a billion times fainter than their host stars.

C) Planets give off only infrared light, not visible light.

D) Planets orbit too far from their stars to be detected.

Answer: B 3) The astrometric method seeks to detect planets by A) precisely measuring distances to stars.

B) directly detecting the light of planets orbiting stars.

C) measuring small changes in the positions of stars on the sky.

D) precisely measuring the velocities of stars moving toward and away from us.

E) measuring small changes in the apparent brightness of stars.

Answer: C 4) The Doppler method seeks to detect planets by A) precisely measuring distances to stars.

B) directly detecting the light of planets orbiting stars.

C) measuring small changes in the positions of stars on the sky.

D) precisely measuring the velocities of stars moving toward and away from us.

E) measuring small changes in the apparent brightness of stars.

Answer: D 5) The transit method seeks to detect planets by A) precisely measuring distances to stars.

B) directly detecting the light of planets orbiting stars.

C) measuring small changes in the positions of stars on the sky.

D) precisely measuring the velocities of stars moving toward and away from us.

E) measuring small changes in the apparent brightness of stars.

Answer: E

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6) The first planets around other stars were discovered A) by Huygens, following his realization that other stars are Suns.

B) by Galileo following the invention of the telescope.

C) about a century ago.

D) in the 1990s.

E) in the 2010s.

Answer: D 7) With current technology, the Doppler method can be used to measure stellar motions that are as small as about A) walking speed.

B) the speed at which continents move with plate tectonics.

C) the speed of cars on a freeway (with no traffic).

D) the cruising speed of an airplane.

E) the orbital speed of Jupiter.

Answer: A 8) What do astronomers mean by the term "hot Jupiters"?

A) planets with masses and composition similar to what we would expect if Jupiter were hotter B) massive planets that orbit stars that are more massive and hotter than our Sun C) planets with masses similar to Jupiter, but that orbit very close to their central star D) planets with masses similar to Jupiter, but compositions that are similar to Mercury E) planets with masses and orbits similar to Jupiter but for which infrared observations indicate they are surprisingly hot in temperature Answer: C 9) What kind of planets are most easily detected using the Doppler method?

A) high mass planets far from their host star B) low mass planets far from their host star C) low mass planets close to their host star D) high mass planets close to their host star E) planets that have been ejected from their systems Answer: D 10) If an extrasolar planet suddenly became larger in radius, but kept the same mass and orbit, what would change in the observed Doppler shift of the star?

A) Nothing. The radius of a planet does not affect the Doppler shift.

B) The time between peaks in the velocity of the star would decrease.

C) The peak velocity of the star would be faster.

D) The shape of the velocity curve would become less symmetric.

E) The lowest velocity of the star would be slower.

Answer: A

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11) If an extrasolar planet suddenly became more massive, but kept the same radius and orbit, what would change in the observed Doppler shift of the star?

A) The peak velocity of the star would be faster.

B) The time between peaks in the velocity of the star would decrease.

C) The time between peaks in the velocity of the star would increase.

D) The shape of the velocity curve would become less symmetric.

E) Nothing. The mass of a planet does not affect the Doppler shift.

Answer: A 12) If an extrasolar planet suddenly became larger in radius, but kept the same mass and orbit, what would change during an observed transit?

A) The amount of starlight would have a larger dip during the transit.

B) The amount of starlight would have a smaller dip during the transit.

C) The time between transits would decrease.

D) The time between transits would increase.

E) Nothing. The radius of a planet does not affect the appearance of a transit.

Answer: A 13) If an extrasolar planet suddenly became more massive, but kept the same radius and orbit, what would change during an observed transit?

A) The amount of starlight would have a larger dip during the transit.

B) The amount of starlight would have a smaller dip during the transit.

C) The time between transits would decrease.

D) The time between transits would increase.

E) Nothing. The mass of a planet does not affect the appearance of a transit.

Answer: E 14) Why do most extrasolar planets discovered by the Doppler method have orbits relatively close to their host stars?

A) They transit more frequently and have thus been more likely to be detected in the short time we have been searching for them.

B) More of the starlight is blocked by the planet when it transits the star.

C) These close-in planets are easier to detect because they cause larger Doppler shifts.

D) The closer to a star, the hotter and therefore brighter the planet is.

E) Planets that are close to a star are heated up and therefore larger.

Answer: C 15) Approximately how many extrasolar planets have been discovered to date?

A) tens B) hundreds C) thousands D) millions E) billions Answer: C

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16) What kind of planet is most easily detected using the transit method? A) large planets in edge-on orbits around small stars B) large planets in face-on orbits around small stars C) small planets in edge-on orbits around big stars D) small planets in face-on orbits around big stars E) Earth-like planets in any orbit Answer: A 17) Which of the following planets in our solar system can we see occasionally transit across the face of the Sun? A) Mercury only B) Mercury and Venus C) Mercury, Venus, and Mars D) Mars, Jupiter, and Saturn E) all of the planets Answer: A 18) Viewed from afar, the transit of Earth would cause the Sun's brightness to dim by approximately A) 10%. B) 5%. C) 1%. D) 0.00001%.

E) 0.01%. Answer: E 19) The Kepler mission discovered thousands of stars by using A) the transit method. B) the Doppler method. C) the astrometric method. D) direct detection. E) gravitational lensing. Answer: A 20) What must be true about the orbit of a planet discovered by the transit method? A) The planet must be closer to its star than Mercury is to the Sun. B) The planet must have a face-on orbit as seen from Earth. C) The planet must have an edge-on orbit as seen from Earth. D) The planet's orbit must be very close to circular. E) The planet's orbit must be very eccentric. Answer: C

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21) Why have most extrasolar planets detected with the transit method been found with orbits fairly close to their host stars?

A) They transit more frequently and are more likely to be detected in the short time we have been searching for them.

B) More of the starlight is blocked by the planet when it transits the star.

C) The wavelength shift of the star's spectrum is larger.

D) The closer to a star, the hotter and therefore brighter the planet is.

E) Planets that are close to a star are heated up and therefore larger.

Answer: A Section 13.2 1) A planet is detected via the Doppler method. What does the time between peaks of the stellar velocity tell us?

A) the planet's size B) the planet's mass C) the planet's density D) the orbital period of the planet E) the orbital eccentricity of the planet Answer: D 2) How can the Doppler method be used to measure the orbital period of a planet?

A) by measuring the speed at which the star orbits the mutual center-of-mass of the star and planet B) by measuring the time it takes for the star's line-of-sight velocity to cycle from peak to peak C) by measuring the asymmetries in the velocity curve D) by measuring the amount by which the starlight is reduced when the planet transits Answer: B 3) How can the Doppler method be used to estimate the average orbital distance of a planet's orbit?

A) by measuring the speed at which the star orbits the mutual center-of-mass of the star and planet, and using Newton's theory of gravity B) by measuring the time it takes for the star's line-of-sight velocity to cycle from peak to peak, and using Newton's version of Kepler's Third law C) by measuring the asymmetries in the velocity curve D) by measuring the amount by which the starlight is reduced when the planet transits Answer: B 4) How can the Doppler method be used to measure the eccentricity of a planet's orbit?

A) by measuring the speed at which the star orbits the mutual center-of-mass of the star and planet, and using Newton's theory of gravity B) by measuring the time it takes for the star's line-of-sight velocity to cycle from peak to peak, and using Newton's version of Kepler's Third law C) by measuring the asymmetries in the velocity curve D) by measuring the amount by which the starlight is reduced when the planet transits Answer: C

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5) Why does the Doppler method only provide a measure of the minimum mass of a planet?

A) Only a small part of the planet's motion is measured.

B) Without a transit observation, the size and therefore density of the planet is unknown.

C) We do not know the exact composition of the planet.

D) The Doppler shift tells only part of a planet's orbital speed (the part toward and away from the observer).

E) We do not have the technology to make a direct image of a planet yet.

Answer: D 6) Current data suggest that ________ have at least one planet.

A) about 1 in 1 million stars B) about 1% of all stars C) about 10% of all stars D) most stars E) 100% of all stars Answer: D 7) Which two methods can be combined to determine an extrasolar planet's density?

A) Doppler and astrometric observations B) Doppler and transit observations C) Doppler and gravitational lensing observations D) astrometric and gravitational lensing observations Answer: B 8) Which two quantities need to be measured in order to determine the density of an extrasolar planet?

A) mass and composition B) orbital period and mass C) radius and orbital period D) radius and composition E) mass and radius Answer: E 9) Current statistical evidence suggests that Earth-sized planets orbiting in the habitable zone are A) extremely rare.

B) likely to exist around at least about 20% of all stars.

C) found around virtually all stars.

Answer: B 10) What type of observation can astronomers use to measure the composition of an extrasolar planet's atmosphere?

A) comparisons of a star's spectrum when a planet is in transit versus when it is eclipsed B) measurements of the host star's velocity throughout an orbital cycle C) measurement of how frequently the planet blocks the host star's light D) combination of a transit observation and a Doppler shift measurement Answer: A

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11) The planet HAT-P-32b has more than twice the radius of Jupiter, yet is only the same mass.

It orbits its star more than a factor of ten closer than Mercury's orbit around the Sun. Which is the most plausible explanation for its large size?

A) The mass measurement is mistaken, and it is actually about 10 times more massive than Jupiter.

B) Planets that are close to a star are hotter, causing them to puff up.

C) It is made of elements other than hydrogen and helium which do not compress under their own gravity.

D) The hydrogen and helium gas compressed under their own gravity.

Answer: B 12) The planet COROT-14b is only slightly larger than Jupiter, but is several times as massive.

Which is the most plausible explanation for its similar size to Jupiter?

A) The mass measurement is mistaken, and it is actually about 10 times more massive than Jupiter.

B) Planets that are close to a star are hotter, causing them to puff up.

C) It is made of elements other than hydrogen and helium which do not compress under their own gravity.

D) The hydrogen and helium gas compressed under their own gravity to a higher density than Jupiter.

Answer: D 13) What is a "super-Earth"?

A) a rocky planet that is more massive than Earth B) a rocky planet that has more water than Earth C) a jovian planet that is approximately the same mass as Earth D) a jovian planet that has a solid surface E) a rocky planet that is closer to its host star than Earth is to the Sun Answer: A Section 13.3 1) How do we think the "hot Jupiters" around other stars were formed?

A) They formed as jovian planets close to the star in the same orbits that they are seen today.

B) They formed as dense, rocky planets close to the star in the same orbits that they are seen today.

C) They formed as jovian planets beyond the frost line and then migrated inward.

D) Many planets were formed around the star but coalesced into a single planet close in.

E) They spun off from the young star when it was rapidly rotating.

Answer: C

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2) How does the theory of planetary migration in disks possibly account for the highly eccentric orbits discovered for some extrasolar planets?

A) When migrating planets collide, they would move onto more eccentric orbits.

B) When migrating planets pass close enough for a gravitational encounter, one may be flung from the system while the other is shifted to a highly elliptical orbit.

C) A migrating planet would create waves in the planet forming disk, which would in turn lead to the formation of planets on highly elliptical orbits.

D) When a planet migrates onto the surface of the star, the additional stellar mass would disrupt the orbits of the remaining planets.

Answer: B 3) What would you expect to be different in a planetary system in which the nebular gas is blown into interstellar space by a stellar wind earlier than occurred in our solar system?

A) No terrestrial planets would form.

B) Jovian planets would be less massive because they had less time to gather hydrogen and helium gas.

C) All planets would be more massive than Jupiter.

D) Most of the planets would be destroyed by migration onto the central star.

Answer: B 4) Which of the following are true statements about the extrasolar planets found so far?

A) Extrasolar planets have a much wider range of densities than the planets in the solar system.

B) Extrasolar planets fall neatly into the terrestrial and jovian categories.

C) Extrasolar planets all have nearly circular orbits.

D) All of the above are correct.

Answer: A 5) Which of the following hypothetical discovery would be most surprising given our current theory of how stars and planets are born?

A) a star system with 7 planets, 2 of which rotate in a direction opposite to their orbital directions B) a star system with 5 planets, each orbiting in a different plane and in different directions C) a star system with a disk of gas but no planets D) a star system with 9 planets, in which 6 of the planets have no moons Answer: B 6) Which of the following hypothetical discoveries would be most surprising given our current theory of how stars and planets are born?

A) A star system has 5 terrestrial planets and 3 jovian planets, with all the terrestrial planets orbiting in one direction all the jovian planets orbiting in the opposite direction.

B) A star system has 12 planets, 3 of which do not seem to fit either the terrestrial or jovian categories.

C) A star system has 20 planets.

D) A star system with 7 planets, 2 of which rotate in a direction opposite to their orbital directions.

Answer: A

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Section 13.4 1) What is the purpose of a "star shade" in efforts to directly detect extrasolar planets?

A) The star shade blocks light from the central star, so planets can be seen.

B) The star shade cools the star, so it does not emit so much contaminating light.

C) The star shade keeps the telescope cooler, so it does not emit as much infrared light.

D) The star shade changes the wavelength of starlight, so it is easier to distinguish from planet light.

E) The star shade separates starlight from planet light based on temperature.

Answer: A General Chapter Questions 1) A transiting extrasolar planet is observed to block 1% of its host star's light. How does the radius of this planet compare to the radius of the host star?

A) The planet's radius is 0.1% of the host star's radius.

B) The planet's radius is 1% of the host star's radius.

C) The planet's radius is 10% of the host star's radius.

D) The planet is the same size as the host star.

Answer: C 2) You use the Doppler method to discover a planet around a nearby star that is very similar to the Sun; the velocity curve that has a period of 6 months. What can you conclude about the planet's orbital distance?

A) The planet's orbital distance is greater than 1 AU. B) The planet's orbital distance cannot be determined based on the information provided.

C) The planet's orbital distance is less than 1 AU. D) The planet's orbital distance is exactly 1 AU. Answer: C 3) You have measured Doppler shifts to plot velocity curves for two otherwise identical stars.

Star A has a period of 6 months and Star B has a period of 1 year. What can you say about the planets causing the motions of these stars?

A) Star A's planet is more massive than Star B's planet.

B) Star A's planet must orbit closer in than Star B's planet.

C) It is impossible to say anything about the planets orbiting these stars.

D) Star B must have a planet like Earth.

Answer: B Short Answer Questions 1) State a testable prediction of the nebular theory that has been confirmed by observations of extrasolar planets. Does this confirmation mean the theory is completely correct?

Answer: One key prediction of nebular theory is that planets should be common around stars, and this has been borne out by discoveries of extrasolar planets. But this does not mean that all aspects of the theory are correct, as they may be other details that will eventually require modification.

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2) Why is Jupiter (in our solar system) not considered to be a "hot Jupiter"?

Answer: Hot Jupiters are Jupiter-like planets that migrated inward to orbit their stars at very close distances, which is what makes their surfaces hot. This large inward migration did not occur in our solar system, perhaps because the nebular gas was cleared by the solar wind before that much migration could occur.

Reading Quiz Questions 1) What is an extrasolar planet?

A) a planet that orbits a star that is not our own Sun B) a planet that is larger than the Sun C) a planet that is extra-large compared to what we'd expect D) a planet that is considered an "extra," in that it was not needed for the formation of its solar system Answer: A 2) The first confirmed detections of extrasolar planets occurred in A) the 1990s.

B) the mid-17th century.

C) the 1920s.

D) 2009.

Answer: A 3) All the following statements are true. Which one makes it possible to learn of the existence of extrasolar planets without seeing the planets themselves?

A) Planets exert gravitational tugs on their stars that cause stars to orbit around the center of mass of their planetary systems.

B) Planets reflect visible light from their stars.

C) Planets emit infrared light.

D) All the planets in a planetary system tend to orbit their star in the same direction and approximately the same plane.

Answer: A 4) The astrometric method looks for planets with careful measurements of a star's A) position in the sky.

B) brightness.

C) velocity toward or away from us.

D) distance from Earth.

Answer: A 5) The transit method searches for extrasolar planets by A) monitoring stars for slight dimming that might occur as unseen planets pass in front of them.

B) obtaining high-resolution photographs of other star systems.

C) observing Doppler shifts in a star's spectrum caused by an unseen planet.

D) looking for slight back and forth shifts in a star's position in our sky.

Answer: A

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6) If we use the Doppler method to measure the period with which a star alternately moves toward and away from us due to an orbiting planet, then we also know the A) orbital period of the planet.

B) mass of the planet.

C) distance to the star.

D) radius of the planet.

Answer: A 7) Suppose we have determined the orbital period of a planet around its star. If we also know the mass of the star, then we can use the planet's orbital period and the star's mass to calculate A) the planet's average orbital distance.

B) mass of the planet.

C) eccentricity of the planet's orbit.

D) radius of the planet.

Answer: A 8) Complete this statement: The larger the decrease in the star's brightness as a planet transits in front of its star, ________ of the planet.

A) the larger the size (radius) B) the larger the mass C) the longer the orbital period D) the larger the orbital distance Answer: A 9) In which of the following cases can we determine the precise mass and density of an extrasolar planet?

A) We have detected the planet with both the transit and Doppler methods.

B) We have detected the planet with the Doppler method, but not any other method.

C) We have detected the planet with the transit method, but not any other method.

D) We have observed both transits and eclipses of the orbiting planet.

Answer: A 10) What do we mean by a "hot Jupiter"?

A) a planet that is Jupiter-like in size but orbits close to its star B) a planet that has a Jupiter-like orbit but is more massive and therefore has a higher internal temperature C) a planet that is Jupiter-like in Size but Earth-like in density D) a planet that has a Jupiter-like orbit but is made of high-melting point materials such as rock and metal Answer: A

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11) What do we mean by a "super Earth"? A) a planet made of metal and rock that is larger in mass than Earth B) a planet that is more massive than Earth and also has surface oceans C) a planet with an Earth-like orbit that has more abundant life than Earth D) a planet similar in size to Earth but orbiting close to its star Answer: A 12) Overall, what do current data suggest about planetary types in other planetary systems? A) Planets come in a wider range of types than the planets in our solar system. B) All planets fall into the same terrestrial and jovian categories as the planets in our solar system. C) Jovian planets are common, while terrestrial planets are rare. D) Planets that fall into either the terrestrial or jovian categories are extremely rare outside of our own solar system. Answer: A 13) Overall, current data suggest that ________ of stars are orbited by one or more planets. A) at least about 70% B) approximately 1% C) approximately 20% D) no more than 30% Answer: A 14) Why were scientists surprised when they first discovered the existence of planets with Jupiter-like masses orbiting close to their stars (the "hot Jupiters")? A) The nebular theory predicts that jovian planets should only form at much larger distances from their stars. B) The surface temperatures of these planets seemed inexplicably high. C) They had expected to detect small, terrestrial planets before large, jovian planets. D) The orbits of these planets did not follow Kepler's laws of planetary motion. Answer: A 15) Which new process was added to the nebular theory of solar system formation to account for the existence of Jupiter-mass planets that orbit close to their stars (the "hot Jupiters")?

A) Planets can migrate from the orbits in which they are born. B) In addition to the categories of terrestrial and jovian, there must be an "in-between" category of planet that has the mass of a jovian planet but the composition of a terrestrial planet. C) In some star systems, it is possible for jovian planets to form in the inner solar system and terrestrial planets to form in the outer solar system. D) Giant impacts can affect planets after they form. Answer: A

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16) Which of the following might explain the lack of "water worlds" (planets made mostly of water or other hydrogen compounds) in our own solar system?

A) In our solar system, the solar wind did not clear out gas until relatively late.

B) There was not enough water in our solar system.

C) Small worlds in our solar system formed only close to the Sun, where it was too hot for hydrogen compounds to condense.

D) Water worlds can form only in systems in which all planets have highly elliptical (eccentric) orbits.

Answer: A 17) How is the GAIA mission relevant to the search for extrasolar planets?

A) It can detect planets through the astrometric method.

B) It can obtain moderate-resolution images of extrasolar planets.

C) It can detect planets through the Doppler method.

D) It can detect planets through the transit method.

Answer: A Concept Quiz Questions 1) From the viewpoint of an alien astronomer, how does Jupiter affect observations of our Sun? A) It causes the Sun to move in a small ellipse with an orbital period of about 12 years.

B) It makes the Sun periodically get somewhat brighter.

C) It makes the Sun appear dimmer when viewed with infrared light.

D) It causes the Sun to move in a small ellipse in the sky, with the same ellipse repeated every night.

Answer: A 2) Which of the following is a major reason why it so difficult to obtain direct images of extrasolar planets?

A) The light of the planets is overwhelmed by the light from their star.

B) Extrasolar planets give off light at different wavelengths than planets in our solar system.

C) No telescope is powerful enough to detect the faint light from a distant planet.

D) Telescopes are too busy with other projects.

Answer: A 3) Suppose you are using the Doppler method to look for planets around another star. What must you do?

A) Compare many spectra of the star taken over a period of many months or years.

B) Compare many spectra of an orbiting planet taken over a period of many months or years.

C) Compare the brightness of the star over a period of many months or years.

D) Carefully examine a single spectrum of an orbiting planet.

E) Carefully examine a single spectrum of the star.

Answer: A

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4) In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?

A) a massive planet that is close to its star B) a massive planet that is far from its star C) a low-mass planet that is close to its star D) a low-mass planet that is far from its star Answer: A 5) Consider a planet orbiting a Sun-like star that has been detected by the Doppler and that has an orbital period of one year. The larger the velocity changes measured for the star, the A) larger the mass of the planet.

B) larger the radius of the planet.

C) smaller the mass of the planet.

D) smaller the radius of the planet.

Answer: A 6) Suppose a planet is discovered by the Doppler method and is then discovered to have transits.

In that case, we can determine all the following about the planet except A) its precise mass.

B) its density.

C) its physical size (radius).

D) its rotation period.

E) its orbital period.

Answer: D 7) The transit method allows us in principle to find planets around A) only a small fraction of stars that have planets.

B) all stars that have planets of any kind.

C) only stars of about the same mass and size as our Sun. D) only stars located within about 100 light-years of Earth.

Answer: A 8) You observe a star similar to our own Sun in size and mass. This star moves slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?

A) The planet must be closer to the star than Earth is to the Sun. B) The planet must have a mass about the same as the mass of Jupiter.

C) The planet must be farther from the star than Neptune is from the Sun. D) You do not have enough information to say anything at all about the planet.

Answer: A

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9) Which of the following will allow you to learn something about a transiting planet's atmospheric composition?

A) Compare spectra obtained before and during an eclipse.

B) Look for slight variations in the time between transits.

C) Use the Doppler method to study the planet throughout a cycle from one transit to the next.

D) Calculate the planet's size, and then use size to infer what its atmospheric composition must be.

Answer: A 10) Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?

A) Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.

B) Within a star's planetary system, all its planets will tend to orbit in the same direction and approximately the same plane.

C) Planets are common, and many or most stars have them.

D) Other planetary systems will have far more numerous asteroids and comets than actual planets.

Answer: A 11) To date, we've found few planets orbiting their stars at distances comparable to the distances of the jovian planets in our solar system. Why do astronomers think this is the case?

A) We have not yet been searching for planets at such distances for a long enough time.

B) Planets at such distances are extremely rare.

C) No known method can detect planets at such large distances.

D) Planets at such distances are probably low in mass.

Answer: A 12) Current evidence suggests that some massive jovian planets orbit at close orbital distances to their stars. How do we think these planets ended up on these close orbits?

A) These planets migrated inward after being born on orbits much farther from their stars.

B) These planets were able to form close to their stars because their solar nebulas were cold in temperature.

C) Despite their large masses, these planets are made of rock and metal and therefore could form in their inner solar systems.

D) These planets were captured from other solar systems.

Answer: A

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13) Assuming that our ideas about how "hot Jupiters" ended up on their current orbits are correct, why didn't our own solar system end up with any hot Jupiters?

A) Our solar nebula must have been blown into space shortly after the formation of the jovian planets.

B) Our jovian planets must have migrated outward from inside the orbit of Mercury.

C) Our solar nebula must have stuck around for an unusually long time after the formation of jovian planets.

D) The existence of Earth and the other terrestrial planets prevented the jovian planets from migrating inward.

Answer: A 14) Based on discoveries to date, which of the following conclusions is justified?

A) Planetary systems are common and planets similar in size to Earth are also common.

B) Although planetary systems are common, few resemble ours with terrestrial planets near the Sun and jovian planets far from the Sun. C) Planets are common, but planets as small as Earth are extremely rare.

D) Most stars have one or more terrestrial planets orbiting within their habitable zones.

Answer: A 15) When is the soonest we are likely to have moderate-resolution images and spectra of Earthlike planets around other stars?

A) in a decade or two, through space observatories now in the early planning stages B) in just a few years, through analysis of observations by the GAIA mission C) any day now, thanks to our largest ground-based telescopes D) in just a few years, through analysis of observations by the James Webb Space Telescope Answer: A

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Visual Quiz Questions

1) The graph shows how a star's orbital speed varies with time because of the gravitational tug of an orbiting planet. These data were obtained by measuring A) the precise wavelengths of spectral lines in the spectrum of the star.

B) the precise wavelengths of spectral lines in the spectrum of the orbiting planet.

C) the precise brightness of the star divided by the precise brightness of the planet.

D) the orbital period of the planet that is orbiting the star.

Answer: A 2) The graph shows how a star's orbital speed varies with time because of the gravitational tug of an orbiting planet. Based on these data, the planet's orbital period is about A) 2 days.

B) 4 days.

C) 6 days.

D) 50 days.

Answer: B

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3) This diagram shows the orbital path of the Sun around the center of mass of our solar system over a 65-year period as it would appear from a distance of 30 light-years. If aliens had constructed this graph at their home star system, they could learn all of the following except

A) the fact that large, icy objects orbit the Sun in the Kuiper belt.

B) the fact that the Sun has more than two planets.

C) the mass and orbital period of Jupiter.

D) the orbital distance of Saturn.

Answer: A 4) This diagram represents a star with an orbiting planet that, as seen from Earth, periodically transits across the face of the star and disappears behind the star. If you measure the brightness of this system, at which point would it be brightest?

A) Point 1 B) Point 2 C) Point 3 D) Point 4 Answer: A

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5) This graph shows the brightness of a star over the course of a transit. Which of the following do we learn about the planet? "

A) It is large enough to block about 2.5% of the star's light.

B) It has an orbital period of less than 2 hours.

C) It is about 2.5% as massive as the star.

D) It is about 97.5% as bright as its star.

Answer: A

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6) This bar graph is based on statistical study of results from the mission. Which of the Kepler following conclusions is supported by the graph?

A) At least about 15% of stars have a planet similar in size to Earth.

B) Most stars with an Earth-sized planet do not have any larger jovian planets orbiting far from their stars.

C) Most stars have five planets.

D) A star orbited by a super-Earth is likely also to be orbited by a mini-Neptune.

Answer: A

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7) Each dot on this graph represents an extrasolar planet detected over about a fouryear period by the Kepler mission. Suppose the mission had been able to continue collecting data for many more years. How would you expect the graph to look different in that case?

A) Additional dots would be found further to the right.

B) Additional dots would be found above the existing dots.

C) Additional dots would be found further to the left.

D) All the existing dots on the graph would move diagonally up and right.

Answer: A

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8) This graph plots planetary mass on the horizontal axis and planetary radius on the vertical axis. Which of the four points marked by one of the bold numbers 1 through 4 represents a planet with the greatest mass?

A) Point 1 B) Point 2 C) Point 3 D) Point 4 Answer: B 9) This graph plots planetary mass on the horizontal axis and planetary radius on the vertical axis. Which of the four points marked by one of the bold numbers 1 through 4 represents a planet with the greatest density?

A) Point 1 B) Point 2 C) Point 3 D) Point 4 Answer: D

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10) This graph plots planetary mass on the horizontal axis and planetary radius on the vertical axis. Which of the four points marked by one of the bold numbers 1 through 4 represents a planet that has about the same composition as Earth but is larger in both size and mass? A) Point 1 B) Point 2 C) Point 3 D) Point 4 Answer: C End-of-Chapter Questions Visual Skills Check Use the following questions to check your understanding of some of the many types of visual information used in astronomy.

This plot, based on Figure 13.4a, shows the periodic variations in the Doppler shift of a star caused by a planet orbiting around it. Positive velocities mean the star is moving away from Earth, and negative velocities mean the star is moving toward Earth. (You can assume that the orbit appears edge-on from Earth.) Answer the following questions based on the information in the graph.

1) How long does it take the star and planet to complete one orbit around their center of mass?

Answer: about 4 days 2) What maximum velocity does the star attain?

Answer: about 50 m/s

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3) Match the star's position at points 1, 2, 3, and 4 in the plot with the descriptions below. a) headed straight toward Earth b) headed straight away from Earth c) closest to Earth d) farthest from Earth Answer: a. 2, b. 4, c. 3, d. 1 4) Match the planet's position at points 1, 2, 3, and 4 in the plot with the descriptions in question 3.

Answer: a. 4, b. 2, c. 1, d. 3 5) What would be the most significant change in the plot if the planet were more massive?

A) It would not change, because it describes the motion of the star, not the planet.

B) The peaks and valleys would get larger (greater positive and negative velocities) because of larger gravitational tugs.

C) The peaks and valleys would get closer together (shorter period) because of larger gravitational tugs.

Answer: B Chapter Review Questions 1) Why are extrasolar planets hard to detect directly?

2) What are the two major approaches to detecting extrasolar planets indirectly?

3) How can gravitational tugs from orbiting planets affect the motion of a star? Explain how alien astronomers could deduce the existence of planets in our solar system by observing the Sun's motion.

4) Briefly describe the astrometric method. What is the GAIA mission?

5) Briefly describe the Doppler method. Summarize the evidence that the planet orbiting 51 Pegasi is a hot Jupiter.

6) How does the transit method work? What was the Kepler mission?

7) Briefly summarize the planetary properties we can in principle measure with current detection methods.

8) Why does the Doppler method generally allow us to determine only minimum planetary masses? In what cases can we be confident that we know precise masses? Explain.

9) How does the transit method tell us planetary size, and in what cases can we also learn mass and density?

10) How do the orbits of known extrasolar planets differ from those of planets in our solar system? Why are these orbits surprising?

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11) Summarize the current state of knowledge about extrasolar planet masses and sizes. Based on the evidence, is it likely that smaller planets or larger planets are more common?

12) Summarize the key features shown in Figure 13.16, and briefly describe the nature of planets that would fit each of the model regions shown on the graph.

13) What is planetary migration, and how may it account for the surprising orbits of many extrasolar planets?

14) How can scientists account for the fact that extrasolar planets seem to come in a wider range of types than the planets of our own solar system?

15) Overall, does the nebular theory seem adequate for describing the origins of other planetary systems? Explain.

16) Based on current evidence, how common are planetary systems?

17) Briefly describe how TESS, CHEOPS, and direct observations should improve our understanding of extrasolar planets in coming years.

Does It Make Sense?

Decide whether or not each of the following statements makes sense (or is clearly true or false).

Explain clearly; not all of these have definitive answers, so your explanation is more important than your chosen answer.

Example: I walked east from our base camp at the North Pole.

Solution: The statement does not make sense because east has no meaning at the North Pole–all directions are south from the North Pole.

18) An extraterrestrial astronomer surveying our solar system with the Doppler method could discover the existence of Jupiter with just a few days of observation.

19) The fact that we have not yet discovered an Earth-size extrasolar planet in an Earth-like orbit tells us that such planets must be very rare.

20) Within the next few years, astronomers expect to confirm all the planet detections made with the astrometric and Doppler methods by observing transits of these same planets.

21) The infrared brightness of a star system decreases when a planet goes into eclipse.

22) Some extrasolar planets are likely to be made mostly of water.

23) Some extrasolar planets are likely to be made mostly of gold.

24) Current evidence suggests that there could be 100 billion or more planets in the Milky Way Galaxy.

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25) It's the year 2025: The TESS mission has announced the discovery of numerous planets with Neptune-like orbits around their stars.

26) It's the year 2025: Astronomers have successfully obtained a high-resolution image of an Earth-size extrasolar planet, showing that it has oceans and continents.

27) It's the year 2040: Scientists announce that our first spacecraft to reach an extrasolar planet is now orbiting a planet around a star located near the center of the Milky Way Galaxy.

Quick Quiz

28) Which method could detect a planet in an orbit that is face-on to Earth? A) Doppler method B) transit method C) astrometric method Answer: No Correct Answer Was Provided. 29) Which detection method or methods measure the gravitational tug of a planet on its star, allowing us to estimate planetary mass? A) the transit method only B) the Doppler method only C) the astrometric and Doppler methods Answer: No Correct Answer Was Provided. 30) Which one of the following can the transit method tell us about a planet? A) its mass B) its size C) the eccentricity of its orbit Answer: No Correct Answer Was Provided. 31) To determine a planet's average density, we can use A) the transit method alone. B) the astrometric and Doppler methods together. C) the transit and Doppler methods together. Answer: No Correct Answer Was Provided. 32) Based on the model types shown in Figure 13.16, a planet made almost entirely of hydrogen compounds would be considered a A) terrestrial planet. B) jovian planet. C) water world.

Answer: No Correct Answer Was Provided.

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33) Look at the dot for Jupiter in Figure 13.16, then at the red dot directly to Jupiter's left.

Compared to the density of Jupiter, the density of the planet represented by that dot is A) higher.

B) lower.

C) the same.

Answer: No Correct Answer Was Provided.

34) The term "super-Earth" refers to a planet that is A) the size of Earth but has more water.

B) larger than Earth but on a close-in orbit that makes it much hotter than Earth.

C) similar in composition to Earth but larger in size.

Answer: No Correct Answer Was Provided.

35) What's the best explanation for the location of hot Jupiters?

A) They formed closer to their stars than Jupiter did.

B) They formed farther out, like Jupiter, but then migrated inward.

C) The strong gravity of their stars pulled them in close.

Answer: No Correct Answer Was Provided.

36) Based on computer models, when is planetary migration most likely to occur in a planetary system?

A) early in its history, when there is still a gaseous disk around the star B) shortly after a stellar wind clears the gaseous disk away C) late in its history, when asteroids and comets occasionally collide with planets Answer: No Correct Answer Was Provided.

37) Based on current data, planetary systems appear to be A) extremely rare.

B) present around about 10% of all stars.

C) present around at least half of all stars.

Answer: No Correct Answer Was Provided.

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Inclusive Astronomy Use these questions to reflect on participation in science.

38) Group Discussion: Astronomy in Color . In 2015, a diverse group of scientists, including some international leaders in the study of extrasolar planets, started a blog called Astronomy in Color. Their blog states that they are "committed to increasing diversity by recognizing, confronting and removing the barriers to racial equity and inclusion." This discussion encourages you to reflect on why the scientists thought such a blog was necessary. a) Prior to the discussion, go to the Astronomy in Color blog, look at some of the posts, and choose one that you would like to read and discuss. b) Gather in groups of three and work together to make a list of reasons some scientists are trying to draw attention to racial equity and inclusion in astronomy. c) For the benefit of the other members of your group, summarize the blog post you read and the issues it highlighted. d) Discuss what you learned from the blog posts. Are the issues they raised connected to broader issues in society? Are some of those issues unique to science in general or to astronomy in particular? e) What advice would your group give to the astronomical community that might help it to become more inclusive?

The Process of Science These questions may be answered individually in short-essay form or discussed in groups, except where identified as group-only.

39) When Is a Theory Wrong?As discussed in this chapter, in its original form the nebular theory of solar system formation does not explain the orbits of many known extrasolar planets, but it can explain them with modifications, such as allowing for planetary migration. Does this mean the theory was wrong or only incomplete before the modifications were made? Explain.Be sure to look back at the discussion in Chapter 3 of the nature of science and scientific theories. 40) Refuting the Theory? Consider the following three hypothetical observations: (1) the discovery of a lone planet that is small and dense like a terrestrial planet but has a Jupiter-like orbit; (2) the discovery of a planetary system in which three terrestrial planets orbit the star beyond the orbital distance of two jovian planets; (3) the discovery that a majority of planetary systems have their jovian planets located nearer to their star than 1 AU and their terrestrial planets located beyond 5 AU. Each of these observations would challenge our current theory of solar system formation, but would any of them shake the very foundations of the theory?

Explain clearly for each of the three hypothetical observations. 41) Unanswered Questions.

As discussed in this chapter, we are only just beginning to learn about extrasolar planets.

Briefly describe one important but unanswered question related to the study of planets around other stars. Then write 2—3 paragraphs in which you discuss how we might answer this question in the future. Be as specific as possible, focusing on the type of evidence necessary to answer the question and how the evidence could be gathered. What are the benefits of finding answers to this question?

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42) Group Activity: Time to Move On. A common theme in science fiction is "leaving home" to find a new planet for humans to live on. Now that we know about thousands of planets, we can start imagining how to choose one.Note: You may wish to do this activity using the four roles described in Chapter 1, Exercise 39. a) Make a list of characteristics that you would look for in a planet that might make a good home. b) Examine the planets in Figure 13.16. Does this graph give enough information to allow you to determine which planets might make good homes, or poor ones? If not, what's missing? c) Suppose you also knew the orbital distance for each of the planets in Figure 13.16. Would that make it easier to find potential good homes? Why or why not?

Investigate Further 43) Explaining the Doppler Method. Explain how the Doppler method works in terms an elementary school child would understand. It may help to use an analogy to explain the difficulty of direct detection and the general phenomenon of the Doppler shift.

44) Comparing Methods. What are the strengths and limitations of the Doppler and transit methods? What kinds of planets are easiest to detect with each method? Are there certain planets that each method cannot detect, even if the planets are very large? Explain. What advantages are gained if a planet can be detected by both methods?

45) No Hot Jupiters Here. How do we think hot Jupiters formed? Why didn't one form in our solar system?

46) Low-Density Planets. Only one planet in our solar system has a density less than 1 g/cm3, but many extrasolar planets do. Explain why in a few sentences. (Hint: Consider the densities of the jovian planets in our solar system, given in Figure 11.1.)

47) A Year on HD 189733b. Imagine you were hovering in the upper atmosphere (in a suitable spacecraft) of the planet that orbits the star HD 189733, for which you can find data in Figures 13.5, 13.12, and 13.16. What would you see, and how would the view be different from the view you would have while floating in Jupiter's atmosphere? Consider factors like local conditions, clouds, how the planet's star would appear, and orbital motion.

48) Project: Detecting an Extrasolar Planet for Yourself. Most colleges and many amateur astronomers have the equipment necessary to detect known extrasolar planets using the transit method. All that's required is a telescope 10 or more inches in diameter, a CCD camera system, and a computer system for data analysis. The basic method is to take exposures of a few minutes' duration over a period of several hours around the times of predicted transit, and then compare the brightness of the star being transited to that of other stars in the same CCD frame. For complete instructions, see the Study Area of Mastering Astronomy.

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Quantitative Problems Be sure to show all calculations clearly and state your final answers in complete sentences.

49) Lost in the Glare.This exercise helps you consider how much harder it would be for an alien astronomer to detect the light from planets in our solar system than to detect the light from the Sun itself. a) Calculate the fraction of the total emitted sunlight that reaches Earth. (Hint: Imagine a sphere around the Sun the size of Earth's orbit , then calculate the fraction of that area taken up by the disk of Earth

.)

b) Earth reflects 29% of the Sun's light. Based on this fact and your answer to part a, find the ratio of the total amount of light emitted by the Sun to the amount reflected by Earth. What does this tell you about the difficulty of detecting a planet like Earth around another star? How would a "star shade" like that discussed in Section 13.4 help? c) Would detecting Jupiter be easier or harder than detecting Earth? Comment on whether you think Jupiter's larger size or greater distance has a stronger effect on its detectability. You may neglect any difference in reflectivity between Earth and Jupiter.

50) Transit of TrES-1. The planet TrES-1, orbiting a distant star, has been detected by both the transit and the Doppler method, so we can calculate its density and get an idea of what kind of planet it is. a) Using the method of Mathematical Insight 13.3, calculate the radius of the transiting planet.

The planetary transits block 2% of the star's light. The star TrES-1 has a radius of about 85% of our Sun's radius. b) The mass of the planet is approximately 0.75 times the mass of Jupiter, and Jupiter's mass is about 1.9 × 1027 kilograms. Calculate the average density of the planet. Give your answer in grams per cubic centimeter. Compare this density to the average densities of Saturn (0.7 g/cm3) and Earth (5.5 g/cm3). Is the planet likely to be terrestrial or jovian in nature? Explain. (Hint: To find the volume of the planet, use the formula for the volume of a sphere: V = πr3. Be careful with unit conversions.)

51) Planet Around 51 Pegasi. The star 51 Pegasi has about the same mass and luminosity as our Sun and is orbited by a planet with an orbital period of 4.23 days and mass estimated to be 0.6 times the mass of Jupiter. a) Use Kepler's third law to calculate the planet's average distance (semimajor axis) from its star.

(Hint: Because the mass of 51 Pegasi is about the same as the mass of our Sun, you can use Kepler's third law in its original form, p2 = a3 [Section 3.3]. Be sure to convert the period into years before using this equation.) b) Suppose the planet reflects 15% of the incoming sunlight. Using Mathematical Insight 10.1, calculate its "no greenhouse" average temperature. How does this temperature compare to that of Earth? c) Repeat part b, but assume that the planet is covered in bright clouds that reflect 80% of the incoming sunlight. d) Based on your answers to parts b and c, do you think it is likely that the conditions on this planet could be conducive to life? Explain.

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52) Identical Planets? Imagine two planets orbiting a star with orbits edge-on to the Earth. The peak Doppler shift for each is 50 m/s, but one has a period of 3 days and the other has a period of 300 days. Calculate the two minimum masses and say which, if either, is larger. (Hint: See Mathematical Insight 13.2.)

53) Finding Orbit Sizes. The Doppler method allows us to find a planet's semimajor axis using just the orbital period and the star's mass (Mathematical Insight 13.1). a) Imagine that a new planet is discovered orbiting a 2MSun star with a period of 5 days. What is its semimajor axis? b) Another planet is discovered orbiting a 0.5MSun star with a period of 100 days. What is its semimajor axis?

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The Cosmic Perspective, 9e (Bennett Chapter et14 al.)Our Star Section 14.1 1) What two forces are balanced in what we call gravitational equilibrium? A) the electromagnetic force and gravity B) outward pressure and the strong force C) outward pressure and inward gravity D) the strong force and gravity E) the strong force and kinetic energy Answer: C 2) How does the Sun generate energy today? A) nuclear fission B) nuclear fusion C) chemical reactions D) gravitational contraction E) gradually expanding in size Answer: B 3) How do we know how old the Sun is? A) from radiometric dating of solar system meteorites B) from Newton's version of Kepler's third law and the orbits of the planets C) from calculating its fuel supply and how fast it is using it up D) from its speed and distance from us E) from radiometric dating of particles in the solar wind Answer: A 4) Where in the Sun do fusion reactions happen? A) core and radiation zone B) only the core C) everywhere inside the Sun Answer: B 5) Scientists in the 1800s suggested that the source of the Sun's energy might be gravitational contraction. What was the major flaw of this hypothesis? A) Contracting objects cool down rather than heat up. B) This process would power the Sun for only about 25 million years, but geologists already had evidence the Earth was much older than that. C) The Sun had been observed to be expanding, not contracting. D) The predicted amount of contraction should have been large enough for astronomers of that time to measure. Answer: B

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6) What keeps the Sun's outer layers from continuing to fall inward in a gravitational collapse?

A) outward pressure due to hot gas B) the strong force between protons C) electromagnetic repulsion between protons D) neutrinos produced by nuclear fusion drag gas outward.

Answer: A 7) Which of the following quantities is equal to the energy per second generated by fusion in the Sun's core?

A) the force of gravity holding the Sun together B) the temperature of the Sun's core C) the temperature at the Sun's photosphere D) the luminosity of the Sun's photosphere Answer: D 8) Why isn't the Sun shrinking or expanding at present?

A) because the Sun has lived for billions of years B) Because the Sun is spinning so fast, the centrifugal forces keep the surface of the Sun supported against collapse.

C) because gas pressure balances gravity in the Sun D) because the Sun is a solid substance Answer: C 9) Which of the following is the best answer to the question "Why does the Sun shine?"

A) The Sun initially began generating energy through nuclear fusion as it formed, but today, it generates energy primarily through the sunspot cycle.

B) The young Sun became hotter through gravitational contraction. Once the core was hot enough, nuclear fusion began and has kept the Sun shining ever since.

C) The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur.

D) As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the Sun reached its current luminosity.

Answer: B 10) We say that the matter in the Sun's interior is a plasma, which mean it is A) a low-density gas.

B) an ionized gas.

C) a thick liquid, like blood.

D) a freely flowing liquid, like water.

E) a very hot but electrically neutral gas.

Answer: B

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11) The Sun's composition (by mass) is approximately A) 100 percent hydrogen and helium. B) 50 percent hydrogen, 25 percent helium, 25 percent other elements. C) 70 percent helium, 28 percent hydrogen, 2 percent other elements. D) 70 percent hydrogen, 28 percent helium, 2 percent other elements. E) 98 percent hydrogen, 2 percent helium, and other elements. Answer: D 12) What is the approximate average temperature of the surface of the Sun? A) 1 million K B) 580,000 K C) 58,000 K D) 5800 K E) 580 K Answer: D 13) What is the approximate temperature of the Sun's core? A) 5800 K B) 10,000 K C) 1 million K D) 15 million K E) 150 million K Answer: D 14) Which layer of the Sun do we see with our eyes? A) photosphere B) corona C) chromosphere D) convection zone E) radiation zone Answer: A 15) The core of the Sun is A) at the same temperature and density as the surface. B) at the same temperature but denser than the surface. C) hotter and denser than the surface. D) constantly rising to the surface through convection. E) composed of iron. Answer: C

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16) Based on its surface temperature of 5800 K, most photons that leave the Sun's surface lie in the ________ region of the electromagnetic spectrum. A) microwave B) infrared C) visible D) ultraviolet E) x-ray Answer: C 17) If the Sun's surface were cooler, how would its appearance change? A) It would appear more red. B) It would appear more blue. C) It would become bright white. D) It would stay the same. Answer: A 18) Order the interior layers of the Sun from hottest to coldest. A) radiation zone, core, convection zone, photosphere B) core, radiation zone, convection zone, photosphere C) photosphere, convection zone, radiation zone, core D) photosphere, convection zone, core, radiation zone Answer: B 19) To estimate the central temperature of the Sun, scientists A) create a version of the Sun in a laboratory. B) use computer models to predict interior conditions. C) send probes to measure the temperature. D) monitor changes in Earth's atmosphere. Answer: B 20) Which of the following properties of the Sun tells us the rate at which energy is being generated in its core? A) surface temperature B) apparent brightness C) mass D) luminosity Answer: D Section 14.2 1) How do today's human-built nuclear power plants on Earth generate energy? A) chemical reactions B) nuclear fusion C) nuclear fission D) converting kinetic energy into electricity E) converting gravitational potential energy into electricity Answer: C

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2) Which has a greater mass: four protons or a helium nucleus with two protons and two neutrons?

A) four protons B) the helium nucleus C) They have the same mass.

Answer: A 3) What temperature is required to fuse hydrogen?

A) thousands of Kelvin B) millions of Kelvin C) billions of Kelvin D) trillions of Kelvin E) any temperature, as long as gravity is strong enough Answer: B 4) What is the primary product created by the fusion of hydrogen in the core of the Sun? A) hydrogen compounds B) plasma C) carbon and oxygen D) radioactive elements like uranium and plutonium E) helium Answer: E 5) Which is the strongest of the fundamental forces in the universe?

A) strong force B) weak force C) electromagnetic force D) gravitational force E) All four forces have the same strength.

Answer: A 6) What is the only known force that can overcome the repulsion between two positively charged nuclei and bind them together in a single nucleus?

A) the strong force B) the weak force C) the electromagnetic force D) the gravitational force E) the Coriolis force Answer: A

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7) About how much mass does the Sun lose through nuclear fusion per second?

A) 4 tons B) 4 million tons C) 600 tons D) 600 million tons E) None; mass is conserved.

Answer: B 8) Suppose you put two protons near each other. Because of the electromagnetic force, what will the two protons do?

A) vollide B) remain stationary C) attract each other D) repel each other E) join together to form a nucleus Answer: D 9) Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?

A) Fusion can only proceed by the proton-proton chain and therefore requires that protons come close enough together to be linked up into a chain.

B) Nuclei have to be very hot in order to fuse, and the only way to get them hot is to bring them close together.

C) Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.

D) Nuclei are attracted to each other by the electromagnetic force, but this force is only strong enough to make nuclei stick when they are very close together.

Answer: C 10) Consider two pairs of protons, one pair moving toward each other at a speed of 1000 km/s and the other at a speed of 10 km/s. Which pair of protons will get closer together before they repel each other?

A) The pair moving toward each other at 1000 km/s/ B) The pair moving toward each other at 10 km/s C) There will be no difference because the protons in both pairs will collide with each other.

D) There will be no difference because they will repel at the same distance regardless of their speeds.

Answer: A 11) The first step in the proton-proton chain produces an antielectron, or positron. What happens to the positron?

A) It slowly works its way to the Sun's surface, where it escapes into space.

B) It rapidly escapes from the Sun, traveling into space at nearly the speed of light.

C) It almost immediately annihilates with an electron, resulting in two gamma-ray photons.

D) It quickly meets an ordinary electron, forming an electron-positron pair that remains stable.

E) It joins with a nearby neutron to form a proton.

Answer: C

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12) Which of the following is the overall fusion reaction by which the Sun currently produces energy?

A) 3 H ⇒ 1 Li + energy B) 3 He ⇒ 1 C + energy C) 4 H ⇒ 4 He + energy D) 6 H ⇒ 1 He + energy E) 4 H ⇒ 1 He + energy Answer: E 13) Why does the Sun's rate of fusion gradually rise over billions of years?

A) The Sun becomes less efficient and must increase the rate of fusion to produce the same amount of energy.

B) Fusion reactions decrease the overall number of particles in the core, causing the core to shrink, converting gravitational potential energy into thermal energy, and increasing the rate of fusion.

C) The radiation produced by fusion reactions that is trapped in the core gradually raises the temperature, increasing the rate of fusion.

D) The Sun gets heavier as it gets older, and the stronger inward pull of gravity increases the fusion rate.

E) The rate of fusion is not rising; it is actually decreasing over time.

Answer: B 14) In what way does our theory of nuclear fusion predict that the Sun should be different today than it was when fusion began about 4-1/2 billion years ago?

A) The Sun's mass should be about 30% higher today.

B) The Sun's mass should be about 30% lower today.

C) The Sun's luminosity should be about 30% higher today.

D) The Sun's radius should be about 30% higher today.

E) The Sun's distance from Earth should be about 30% lower today.

Answer: C 15) Why does the Sun emit neutrinos?

A) Convection releases neutrinos, which random walk through the radiation zone.

B) The Sun does not emit neutrinos.

C) Neutrinos are a by-product of fusion in the Sun's core.

D) Solar flares create neutrinos with magnetic fields.

Answer: C

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16) Which statement best describes what used to be called the solar neutrino problem?

A) Theoretical models predict that neutrinos should be produced in the Sun, but no neutrinos had ever been observed to be coming from the Sun. B) Solar neutrinos were detected in fewer numbers than predicted by theoretical models.

C) Theoretical models did not predict the production of neutrinos by the Sun, yet solar neutrinos were detected.

D) Theoretical models predicted that all solar neutrinos should be destroyed before they arrive at Earth, yet neutrinos were detected on Earth.

E) The neutrinos that were being detected from the Sun had much smaller masses than theoretical models could account for.

Answer: B 17) Which of the following statements about neutrinos is not true?

A) About a thousand trillion neutrinos are passing through your body every second.

B) Neutrinos are created as a by-product of the proton-proton chain.

C) Neutrinos have no electrical charge.

D) Neutrinos have a tendency to pass through just about anything without interactions, making them very difficult to detect.

E) The mass of a neutrino is 30 percent of the mass of an electron.

Answer: E 18) The solar neutrino problem referred to the fact that, a couple decades ago, fewer neutrinos were being detected from the Sun than predicted by our theory of nuclear fusion. What was the solution to this problem?

A) We learned that the Sun is generating energy by means other than nuclear fusion.

B) We learned that the Sun is generating much less energy than we thought it was.

C) We learned that our detectors were mistaking neutrinos for the particles known as cosmic rays.

D) We learned that our detectors were detecting only one of three different types of neutrinos that reach us from the Sun. E) We learned that our detectors were not functioning properly.

Answer: D 19) Suppose that, for some unknown reason, the core of the Sun suddenly became hotter. Which of the following best describes what would happen?

A) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and turn the Sun into a giant star.

B) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal.

C) Higher temperature would cause the rate of fusion to fall, decreasing the internal pressure and causing the core to collapse until the rate of fusion returned to normal.

D) The higher temperature would not affect the fusion rate, but would cause the core to expand and cool until the temperature returned to normal, with the core at a new, slightly larger size.

Answer: B

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20) What would happen to the core of the Sun if its temperature rose slightly? A) The rate at which fusion occurs would decrease, leading to a contraction of the core, which would in turn cause the temperature to rise even further. B) The rate at which fusion occurs would increase, leading to a contraction of the core, which would in turn cause the temperature to rise even further. C) The rate at which fusion occurs would increase, leading to an expansion of the core, which would in turn cause the temperature to drop back down. D) The rate at which fusion occurs would decrease, leading to an expansion of the core, which would in turn cause the temperature to drop back down. Answer: C 21) When the temperature of the Sun's core goes up, what happens next? A) Fusion reactions slow down, core shrinks and heats. B) Fusion reactions speed up, core expands and cools.

C) Fusion reactions speed up, the core shrinks and cools. D) Fusion reactions slow down, the core expands and heats. Answer: B 22) Suppose that, for some unknown reason, the core of the Sun suddenly became hotter and the rate of nuclear fusion thereby increased.

What would happen next? A) The Sun would quickly run out of hydrogen, causing the temperature to return to its original value. B) The rate of fusion would almost instantly skyrocket, causing the Sun to explode. C) The temperature would continue to increase, causing higher and higher fusion rates. D) The core would expand, reducing the pressure and temperature, and the rate of fusion would decrease until it returned to its original level. Answer: D 23) What would happen in the Sun if the temperature of the core decreased? A) The fusion rate increases, then the core expands and cools. B) The fusion rate increases, then the core shrinks and heats. C) The fusion rate decreases, then the core shrinks and heats. D) The fusion rate decreases, then the core expands and heats.

Answer: C 24) What would happen if the fusion rate in the core increased but the core could not expand? A) The Sun's core would heat and the rate of fusion would increase further. B) The Sun's core would reach a new equilibrium, but at a higher temperature. C) The Sun's core would reach a new equilibrium, but at a cooler temperature. D) The Sun's core would cool and the rate of fusion would decrease. Answer: A

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25) Most of the energy produced in the Sun is released in the form of visible light from the photosphere. However, some energy is released from the upper layers of the solar atmosphere.

Which of the following best describes where other forms of light are released?

A) The chromosphere is the source of ultraviolet light, and the corona is the source of x-rays.

B) The chromosphere is the source of infrared light, and the corona is the source of ultraviolet light.

C) The chromosphere is the source of x-rays, and the corona is the source of radio waves.

D) The convection zone is the source of ultraviolet light, and the upper photosphere is the source of x-rays.

E) Radio waves can pass directly through the gas which allows us to see the core.

Answer: A 26) What causes the bubbling pattern of granulation that we see in the Sun's photosphere?

A) underlying convection B) sunspots C) dark areas of the pattern have larger concentrations of carbon D) dust particles E) magnetic fields Answer: A 27) The Sun is gradually increasing in luminosity as it ages. It is about 30% more luminous than it was when it was born. Why isn't this increase considered to be an explanation for global warming?

A) The Sun is increasing in luminosity way too slowly, over many millions of years.

B) What the Sun was doing millions of years ago is what determines Earth's temperature, since the Earth doesn't respond directly to what the Sun is doing today.

C) The amount of energy the Earth receives from the Sun remains constant regardless of what the Sun does.

D) The scientists are covering up this potentially valid explanation.

Answer: A 28) How do we know the interior structure of the Sun? A) from x-ray images of the Sun B) from mathematical models that use the laws of physics and the Sun's observed characteristics C) from probes sent below the surface of the Sun Answer: B 29) What have studies of sunquakes, or helioseismology, revealed?

A) The Sun vibrates only on the surface.

B) "Sunquakes" are caused by similar processes that create earthquakes on Earth.

C) The Sun generates energy by nuclear fusion.

D) Our mathematical models of the solar interior are fairly accurate.

E) Neutrinos from the solar core reach the solar surface easily.

Answer: D

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30) Which of the following provides evidence to support models of how fusion occurs in the Sun's core?

A) solar neutrinos B) solar flares C) Sun spots D) x-ray observations E) careful study of the Sun's atmospheric structure Answer: A

31) This image shows the velocity of gas moving toward or away from us on the Sun's surface, as measured through Doppler shifts; the key indicates the measured velocity, with negative velocities indicating gas moving toward us and positive velocities away from us. Based on this map, about how fast is the sun rotating at its equator? (Hint: determine the speed at which equatorial gas is moving toward us on one side of the equator and away from us on the other.)

A) about 200 m/s B) about 2000 m/s C) about 20,000 m/s D) The Sun is not rotating.

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32) This image shows the velocity of gas moving toward or away from us on the Sun's surface, as measured through Doppler shifts; the key indicates the measured velocity, with negative velocities indicating gas moving toward us and positive velocities away from us. What do the small-scale changes in the shading represent in this map?

A) vibrations of gas moving up or down at the solar surface B) variations in the altitude of the solar surface C) variations in the temperature of the photosphere D) Nothing; this is an artist's rendering of the sun.

Answer: A 33) Which of the following is not a method astronomers use to determine the physical conditions inside the Sun? A) observing x-ray images of the solar interior using satellites B) building mathematical models that use the laws of physics C) detecting solar neutrinos generated in the Sun's core D) measuring Doppler shifts to observe solar vibrations Answer: A 34) Imagine that you are trying to stop neutrinos with a lead shield. How thick would you need to make this shield to ensure that it can stop an average neutrino?

A) about one meter B) about 700,000 kilometers (the radius of the Sun) C) about 150 million kilometers (the size of an astronomical unit) D) about one light-year E) about 14 billion light-years (the size of the observable universe) Answer: D 35) Approximately how many neutrinos pass through your body each second?

A) about a thousand trillion B) about one thousand C) about 1023 D) None; they are blocked by the Earth's atmosphere.

Answer: A 36) About a thousand trillion neutrinos are passing through your body every second. Why don't they hurt you?

A) Neutrinos interact with ordinary matter only through the weak force.

B) Their masses are too low to cause any damage.

C) They are traveling too slowly to cause any damage.

D) Our immune systems release antibodies that counteract the damage the neutrinos cause.

E) Actually, they do—neutrinos are the cause of many cancers.

Answer: A

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Section 14.3 1) Why are sunspots cooler than the surrounding solar surface? A) They are regions where convection carries cooler material downward. B) Strong magnetic fields slow convection and prevent hot plasma from entering the region. C) Magnetic fields trap ionized gases that absorb light. D) There is less fusion occurring there. E) Magnetic fields lift material from the surface of the Sun, cooling off the material faster. Answer: B 2) Why do sunspots appear dark? A) They are composed of different elements than the rest of the sun. B) They are regions that do not emit any radiation. C) They are regions that are significantly cooler than the rest of the photosphere. D) They are regions nearly devoid of gas. Answer: C 3) The intricate patterns visible in an x-ray image of the Sun generally show A) extremely hot plasma flowing along magnetic field lines. B) granulation on the photosphere. C) helioseismological fluctuations. D) structure within sunspots. Answer: A 4) What are coronal holes? A) regions on the photosphere where magnetic lines poke through, creating the cooler areas of the sunspots B) areas of the corona where magnetic field lines project into space, allowing charged particles to escape the Sun, becoming part of the solar wind C) holes in the corona of the Sun that allow us to see the photosphere D) tunnels in the outer layers of the Sun through which photons can escape more quickly than through the radiation zone Answer: B 5) Which of the following statements about the sunspot cycle is not true? A) The number of sunspots peaks approximately every 11 years. B) With each subsequent peak in the number of sunspots, the magnetic polarity of the Sun is the reverse of the previous peak. C) The rate of nuclear fusion in the Sun peaks about every 11 years. D) The cycle is truly a cycle of magnetic activity, and variations in the number of sunspots are only one manifestation of the cycle. E) The number of solar flares peaks about every 11 years. Answer: C

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6) What processes are involved in the sunspot cycle?

A) gravitational contraction of the Sun B) wave motions in the solar interior C) variations of the solar thermostat D) the winding of magnetic field lines due to differential rotation E) the interaction of the Earth's magnetic field with that of the Sun Answer: D 7) What observations characterize solar maximum?

A) The Sun becomes much brighter.

B) The Sun emits light of longer average wavelength.

C) The Sun rotates faster at the equator.

D) We see many sunspots on the surface of the Sun. Answer: D

8) Based on the above graph, the average time between maximums of the sunspot cycle is about A) 110 years.

B) 11 years.

C) 1 year.

D) a few months.

Answer: B 9) Based on the above graph, which statement about the sunspot cycle is true?

A) The period of the cycle is always exactly 11 years.

B) Some solar minima (when the Sun has the fewest sunspots) have significantly fewer sunspots than others.

C) Some solar maxima (when the Sun has the most sunspots) have significantly more sunspots than others.

D) At least 1% of the Sun's surface is covered with sunspots at all times.

Answer: C

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10) While we can't completely rule out a connection between the sunspot cycle and weather cycles on Earth, most scientists doubt there is a significant effect because A) the Sun's luminosity changes less than about 0.1% between minimum and maximums of the sunspot cycle.

B) the Sun is too far away to affect Earth's weather.

C) there are no known cycles in weather or climate that last as long as the sunspot cycle.

D) sunspots are linked to the Sun's magnetic field, which could not possibly have any effect on Earth.

Answer: A 11) We can rule out a connection between changes in the Sun's luminosity and the global warming that is currently occurring on Earth because A) the Sun's luminosity has remained fairly steady even as Earth's temperature as increased.

B) the Sun is too far away to affect Earth's climate.

C) changes in the Sun's luminosity cannot occur on the time scale over which global warming has occurred.

D) Earth's atmosphere prevents changes in the Sun's luminosity from having any effect on Earth's surface.

Answer: A General Chapter Questions 1) Which of the following statements is an inference from a model (rather than an observation)?

A) The Sun emits neutrinos.

B) The photosphere emits visible light.

C) The photosphere is made out of mainly hydrogen and helium.

D) The corona is hotter than the photosphere.

E) The Sun's core is gradually turning hydrogen into helium.

Answer: E 2) Which of the following statements about the Sun is an inference from a model, not an observation?

A) The photosphere emits visible light.

B) The Sun emits neutrinos.

C) The corona is hotter than the photosphere.

D) The convection zone is cooler than the radiation zone.

Answer: D Short Answer Questions 1) Briefly explain how the Sun became hot enough for nuclear fusion.

Answer: The Sun formed from a cloud of gas. As it contracted, its gravitational potential energy was converted to thermal energy. The Sun continued to contract until the core became hot enough to sustain nuclear fusion.

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2) Suppose someone tells you that the Sun generates its light and heat because it is a giant ball of fire. Would you agree? Why or why not?

Answer: No. Fire is produced by chemical burning. The Sun could not possibly have generated chemical energy for billions of years because this process would have burned itself out long ago.

The correct explanation is that the Sun generates its light and heat from nuclear fusion in its core.

3) Briefly describe why the fact that we detect neutrinos coming from the Sun supports the idea that the Sun generates energy by nuclear fusion.

Answer: Laboratory experiments and theory show that fusion produces neutrinos. Therefore, scientists predict that neutrinos should come from the Sun if fusion is occurring in its core.

Theories predict how many and what type of neutrinos should be observed. Thus, the observations that confirm this prediction support the theory.

Reading Quiz Questions 1) According to modern science, approximately how old is the Sun? A) 4 1/2 billion years B) 25 million years C) 10,000 years D) 400 million years Answer: A 2) The Sun will exhaust its nuclear fuel in about A) 5000 AD. B) 5 million years.

C) 5 billion years.

D) 50 billion years.

Answer: C 3) Which of the following correctly describes how the process of gravitational contraction can make a star hot?

A) When a star contracts in size, gravitational potential energy is converted to thermal energy.

B) Gravitational contraction involves nuclear fusion, which generates a lot of heat.

C) Heat is generated when gravity contracts because gravity is an inverse square law force.

D) Gravitational contraction involves the generation of heat by chemical reactions, much like the burning of coal.

Answer: A 4) The source of energy that keeps the Sun shining today is A) nuclear fission.

B) nuclear fusion.

C) gravitational contraction.

D) chemical reactions.

Answer: B

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5) What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?

A) the strong force and the weak force B) gravitational force and outward pressure C) gravitational force and surface tension D) the strong force and the electromagnetic force Answer: B 6) Energy balance in the Sun refers to a balance between A) the rate at which fusion generates energy in the Sun's core and the rate at which the Sun's surface radiates energy into space. B) the mass that the Sun loses each second and the amount of mass converted into energy each second. C) the force of gravity pulling inward and the force due to pressure pushing outward. D) the amount of energy the Sun radiates into space and the amount of energy that reaches Earth. Answer: A 7) When we say that the Sun is a ball of plasma, we mean that A) the Sun is made of material that acts like a liquid acts on Earth.

B) the Sun is made of atoms and molecules. C) the Sun consists of gas in which many or most of the atoms are ionized (missing electrons). D) the Sun is roughly the same color as blood. Answer: C 8) What is the Sun's approximate composition (by mass)? A) 70% hydrogen, 28% helium, 2% other elements B) 100% hydrogen and helium C) 50% hydrogen, 25% helium, 25% other elements D) 90% dark matter, 10% ordinary matter Answer: A 9) From the center outward, which of the following lists the "layers" of the Sun in the correct order? A) core, radiation zone, convection zone, photosphere, chromosphere, corona B) core, radiation zone, convection zone, corona, chromosphere, photosphere C) core, convection zone, radiation zone, corona, chromosphere, photosphere D) core, corona, radiation zone, convection zone, photosphere, chromosphere Answer: A 10) What are the appropriate units for the Sun's luminosity? A) watts B) joules C) newtons D) kilograms Answer: A

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11) The Sun's visible surface (that is, the surface we can see with our eyes) is called the A) photosphere. B) chromosphere. C) corona. D) core. Answer: A 12) The Sun's average surface (photosphere) temperature is about A) 5,800 K. B) 1,000,000 K. C) 1,000 K. D) 37,000 K. Answer: A 13) What is the solar wind?

A) a stream of charged particles flowing outward from the surface of the Sun B) the uppermost layer of the Sun, which lies just above the corona C) the strong wind that blows sunspots around on the surface of the Sun D) the wind that causes huge arcs of gas to rise above the Sun's surface Answer: A 14) The fundamental nuclear reaction occurring in the core of the Sun is A) nuclear fission.

B) radioactive decay.

C) nuclear fusion of hydrogen into helium.

D) nuclear fusion of helium to carbon.

Answer: C 15) The proton—proton chain is A) the specific set of nuclear reactions through which the Sun fuses hydrogen into helium.

B) the linkage of numerous protons into long chains.

C) another name for the force that holds protons together in atomic nuclei.

D) an alternative way of generating energy that is different from the fusion of hydrogen into helium.

Answer: A 16) What is the overall result of the proton—proton chain?

A) 4 H becomes 1 He + energy.

B) 6 H becomes 1 He + energy.

C) p + p becomes 1 deuterium nucleus (2H) + energy.

D) Individual protons are joined into long chains of protons.

Answer: A

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17) To estimate the central temperature of the Sun, scientists A) send probes to measure the temperature.

B) use hot gas to create a small Sun in a laboratory.

C) monitor changes in Earth's atmosphere.

D) use computer models to predict interior conditions.

Answer: D 18) Why are neutrinos so difficult to detect?

A) They have a tendency to pass through just about any material without any interactions.

B) They are extremely rare.

C) They have no mass.

D) No one knows; this is the essence of the "solar neutrino problem."

Answer: A 19) The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about A) a few hundred thousand years ago.

B) 3 days ago.

C) 100 years ago.

D) 1,000 years ago.

Answer: A 20) What happens to energy in the Sun's convection zone?

A) Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.

B) Energy is produced in the convection zone by thermal radiation.

C) Energy slowly leaks outward through the radiative diffusion of photons that repeatedly bounce off ions and electrons.

D) Energy is produced in the convection zone by nuclear fusion.

Answer: A 21) What do sunspots, solar prominences, and solar flares all have in common?

A) They are all strongly influenced by magnetic fields on the Sun. B) They all have about the same temperature.

C) They are all shaped by the solar wind.

D) They all occur only in the Sun's photosphere.

Answer: A 22) Which of the following is not a characteristic of the 11-year sunspot cycle?

A) The sunspot cycle is steady, so that each 11-year cycle is nearly identical to every other 11year cycle.

B) The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common.

C) The Sun's entire magnetic field flip-flops with each cycle, so that the overall magnetic cycle averages 22 years.

D) The number of sunspots on the Sun at any one time gradually rises and falls, with an average of 11 years between the times when sunspots are most numerous.

Answer: A

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23) How is the sunspot cycle directly relevant to us here on Earth?

A) Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.

B) The sunspot cycle strongly influences Earth's weather.

C) The Sun's magnetic field, which plays a major role in the sunspot cycle, affects compass needles that we use on Earth.

D) The brightening and darkening of the Sun that occurs during the sunspot cycle affects plant photosynthesis here on Earth.

E) The sunspot cycle is the cause of recent global warming.

Answer: A Concept Quiz Questions 1) In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot because of gravitational contraction. What was the major drawback to this idea?

A) It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.

B) It predicted that the Sun would shrink noticeably as we watched it, but the Sun appears to be stable in size.

C) It is physically impossible to generate heat simply by making a star shrink in size.

D) It predicted that Earth would also shrink in size with time, which would make it impossible to have stable geology on our planet.

Answer: A 2) When is/was gravitational contraction an important energy generation mechanism for the Sun? A) It was important when the Sun was forming from a shrinking interstellar cloud of gas.

B) It is the primary energy generation mechanism in the Sun today.

C) It has played a role throughout the Sun's history, but it was most important right after nuclear fusion began in the Sun's core.

D) It is important during periods when the Sun is going from solar maximum to solar minimum.

Answer: A 3) What do we mean when we say that the Sun is in gravitational equilibrium?

A) There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.

B) The Sun maintains a steady temperature.

C) The hydrogen gas in the Sun is balanced so that it never rises upward or falls downward.

D) The Sun always has the same amount of mass, creating the same gravitational force.

Answer: A

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4) What do we mean when we say that the Sun is in energy balance?

A) The amount of energy released by fusion in the Sun's core equals the amount of energy radiated from the Sun's surface into space.

B) The Sun maintains a steady rate of energy output into space.

C) The inward force of gravity balances the outward push of pressure.

D) The amount of energy contained in the Sun's magnetic field is in balance with the amount of energy going into solar activity such as sunspots and solar flares.

Answer: A 5) Which of the following is the best answer to the question, "Why does the Sun shine?"

A) As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.

B) As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the Sun reached its current luminosity.

C) The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur.

D) The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle.

Answer: A 6) How does the Sun's mass compare to Earth's mass?

A) The Sun's mass is about 300,000 times the mass of the Earth.

B) The Sun's mass is about 300 times the mass of the Earth.

C) The Sun's mass is about 30 times the mass of the Earth.

D) Both have approximately the same mass.

Answer: A 7) Which of the following best describes why the Sun emits most of its energy in the form of visible light?

A) Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.

B) Nuclear fusion in the Sun's core produces visible light photons.

C) The visible light comes from energy level transitions as electrons in the Sun's hydrogen atoms jump between level 1 and level 2.

D) The Sun's gas is on fire like flames from wood or coal, and these flames emit visible light.

Answer: A 8) The Sun's surface seethes and churns with a bubbling pattern. Why? A) We are seeing hot gas rising and cool gas falling as a result of the convection that occurs beneath the surface.

B) The Sun's surface is boiling.

C) The churning gas is being stirred up by the strong solar wind.

D) The churning is an illusion created by varying radiation; the gas on the Sun's surface is actually quite still.

Answer: A

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9) Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?

A) The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.

B) Both processes involve nuclear fusion, but the Sun fuses hydrogen, while nuclear power plants fuse uranium.

C) The Sun generates energy through nuclear reactions, while nuclear power plants generate energy through chemical reactions.

D) The Sun generates energy through fission, while nuclear power plants generate energy through fusion.

Answer: A 10) Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is A) ejected into space in a solar wind.

B) ejected into space by solar flares.

C) converted to an amount of energy equal to 4 million tons times the speed of light squared.

D) reabsorbed as molecular hydrogen.

Answer: C 11) Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?

A) Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.

B) Nuclei are attracted to each other by the electromagnetic force, but this force is only strong enough to make nuclei stick when they are close together.

C) Nuclei have to be hot to fuse, and the only way to get them hot is to bring them close together.

D) Fusion can proceed only by the proton—proton chain, and therefore requires that protons come close enough together to be linked up into a chain.

Answer: A 12) If the Sun's core suddenly shrank a little bit, what would happen in the Sun? A) The core would heat up, fusion rates would increase, the core would re-expand.

B) The core would cool off and continue to shrink as its density increased.

C) The density of the core would decrease, causing the core to cool off and expand.

D) The core would heat up, causing it to radiate so much energy that it would shrink even more.

Answer: A

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13) Which of the following best explains why the Sun's luminosity gradually rises over billions of years? A) Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity. B) Nuclear reactions in the Sun become more efficient with time, so that each fusion reaction releases more energy when the Sun is old than when it is young; this in turn raises the Sun's luminosity. C) The Sun's core gradually expands with time, and this expansion means there is more room for energy to be generated and hence increases the Sun's luminosity. D) The planets need more and more energy to maintain any life on them as time goes on, and therefore the Sun must bet hotter. Answer: A 14) Which of the following choices is not a way by which we can study the inside of the Sun? A) We can send a space probe into the Sun's photosphere. B) We can probe the interior of the Sun by studying the vibrations in its photosphere. C) We can make a computer model of the Sun's interior that allow us to predict the observable properties of the Sun. D) We can study solar neutrinos. Answer: A 15) Why does the Sun emit neutrinos? A) Solar flares create neutrinos with magnetic fields. B) Fusion in the Sun's core creates neutrinos. C) Convection releases neutrinos, which random walk through the radiation zone. D) The Sun was born with a supply of neutrinos that it gradually emits into space. E) The Sun does not emit neutrinos. Answer: B 16) If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)? A) Fusion reactions in the Sun have ceased within the past few minutes. B) Fusion reactions in the Sun ceased a few hundred thousand years ago. C) Fission reactions in the Sun have ceased. D) The Sun has exhausted its supply of neutrinos. Answer: A 17) A salesman attempts to convince you to purchase a "solar neutrino shield" to protect you and your family. (It's even "on sale!") Why do you turn down this excellent offer? A) Neutrinos rarely, if ever, interact with other matter. B) There's no such thing as a solar neutrino. C) Solar neutrinos are generated by solar winds, but we're in a solar minimum now, so the risk of damage is very low. D) The Earth's natural magnetic field already offers excellent protection against the onslaught of solar neutrinos. Answer: A

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18) Why do sunspots appear dark in pictures of the Sun? A) They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

B) They are too cold to emit any visible light.

C) They are holes in the solar surface through which we can see through to deeper, darker layers of the Sun. D) They are extremely hot and emit all their radiation as X rays rather than visible light.

Answer: A 19) How can we best observe the Sun's chromosphere and corona?

A) The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.

B) The chromosphere is best observed with infrared telescopes and the corona is best observed with ultraviolet telescopes.

C) The chromosphere and corona are both best studied with visible light.

D) The chromosphere and corona are both best studied with radio telescopes.

Answer: A 20) The intricate patterns visible in an X-ray image of the Sun generally show A) helioseismological fluctuations.

B) a bubbling pattern on the photosphere.

C) extremely hot plasma flowing along magnetic field lines.

D) structure within sunspots.

Answer: C 21) How can we measure the strength of magnetic fields on the Sun? A) by looking for the splitting of spectral lines in the Sun's spectrum B) by observing the sizes of sunspots: Bigger sunspots mean a stronger field C) by observing auroras here on Earth D) only by using sophisticated computer models because there are no observational ways of measuring magnetic field strength Answer: A 22) Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because A) it is too dangerous to send the Space Shuttle to service satellites during solar maximum.

B) Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits.

C) of increased magnetic interference.

D) they are more likely to have their electronics "fried" by a solar flare during solar maximum.

Answer: B

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23) We can essentially rule out the Sun as a cause of global warming over the past few decades because A) the amount of incoming sunlight has decreased while Earth's average temperature has increased.

B) the amount of light coming from the Sun does not change over time scales of decades.

C) there is no evidence that the Sun can affect climate.

D) the number of sunspots on the Sun varies in an approximately 11-year cycle.

Answer: A Visual Quiz Questions 1) The arrows in this diagram are meant to show how gravitational equilibrium works in the Sun. What do the different colors and different arrow lengths represent?

A) inward pointing green arrows represent gravity outward pointing red arrows represent pressure longer arrows represent a stronger push or pull B) inward pointing green arrows represent gravity outward pointing red arrows represent the solar wind longer arrows represent a stronger push or pull C) inward pointing green arrows represent conduction outward pointing red arrows represent radiation longer arrows represent greater intensity D) inward pointing green arrows represent downward convection outward pointing red arrows represent upward convection longer arrows represent stronger convection Answer: A

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2) What layer of the Sun are we seeing in this photo?

A) photosphere B) chromosphere C) corona D) radiation zone Answer: A 3) The dark spots in this photo (such as the one indicated by the arrow) represent what we call

A) sunspots.

B) convection zones.

C) coronal holes.

D) solar prominences.

E) Great Dark Spots.

Answer: A

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4) Which photo pair shows Earth correctly scaled in comparison to the Sun? A)

B)

C)

D)

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5) This photograph shows a small portion of the Sun's photosphere. What is going on in the bright regions (such as the bright region indicated by the arrow)?

A) Hot gas is rising up from the solar interior.

B) Cool gas is falling back down into the solar interior.

C) The bright spots are regions of unusually intense magnetic fields.

D) The bright spots are what we call sunspots.

Answer: A

6) This x-ray image shows a loop of hot gas above the surface of the Sun. If we took a visible light photo that looked in the Sun's photosphere just under the two points where the loop of gas comes down (arrows), what would we find?

A) sunspots B) bright prominences C) coronal holes D) radiation zones Answer: A

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