Astronomy The Universe at a Glance Eric Chaisson Test Bank

Type:

Test Bank

Resource:

Astronomy The Universe at a Glance

Edition:

1st Edition

Author(s):

Eric Chaisson Steve McMillan

Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 1 The Night Sky 1) The distances to bodies in the solar system are a few light minutes to light hours.

Answer: TRUE Diff: 2 Section Ref: 1.1 2) A light-year is a measurement of time.

Answer: FALSE Diff: 1 Section Ref: 1.1 3) Constellations are close clusters of stars, all at about the same distance from the Sun. Answer: FALSE Diff: 1 Section Ref: 1.2 4) From the South Pole, Polaris would appear directly overhead.

Answer: FALSE Diff: 1 Section Ref: 1.2 5) Only at the equator are all the stars visible over the course of the year.

Answer: TRUE Diff: 2 Section Ref: 1.2 6) Over the course of a night, Polaris moves less than any other visible star in the sky.

Answer: TRUE Diff: 3 Section Ref: 1.2 7) There are 3,600 arc seconds in a degree.

Answer: TRUE Diff: 2 Section Ref: 1.2 8) If a star rises about 9 PM tonight, and with the sidereal day being four minutes less than the solar one, then in a month it will rise about 7 PM. Answer: TRUE Diff: 3 Section Ref: 1.4

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9) The Full Moon rises around sunrise, and sets around sunset.

Answer: FALSE Diff: 1 Section Ref: 1.4 10) From full Moon to third quarter Moon takes about a week.

Answer: TRUE Diff: 2 Section Ref: 1.4 11) The first quarter Moon will rise about noon, and set about midnight.

Answer: TRUE Diff: 2 Section Ref: 1.4 12) As it orbits the Earth, the Moon appears to move eastward about its own diameter every hour.

Answer: TRUE Diff: 3 Section Ref: 1.4 13) At apogee, the Moon is at its farthest from Earth and thus appears smaller than normal.

Because of this it can produce only annular solar eclipses, but not total solar eclipses.

Answer: TRUE Diff: 2 Section Ref: 1.5 14) At apogee, the Moon is at its farthest from the Earth and thus appears larger than normal.

Because of this, it can produce total solar eclipses, but not annular solar eclipses.

Answer: TRUE Diff: 2 Section Ref: 1.5 15) When the Moon passes directly between the Sun and the Earth, we see a lunar eclipse.

Answer: FALSE Diff: 1 Section Ref: 1.5 16) It was Aristotle who used the scientific method to show the Earth was a sphere.

Answer: TRUE Diff: 2 Section Ref: 1.6

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17) No one knew that the Earth was round (spherical) until the 1500s, when explorers such as Magellan sailed around the world.

Answer: FALSE Diff: 1 Section Ref: 1.6 18) Which of the choices below correctly lists things in order from largest to smallest?

A) Sun, Earth, Solar System, Milky Way, Universe B) Universe, Milky Way, Sun, Earth, Solar System C) Solar System, Earth, Sun, Universe, Milky Way D) Universe, Milky Way, Solar System, Sun, Earth E) Milky Way, Universe, Solar System, Sun, Earth Answer: D Diff: 2 Section Ref: 1.1 19) Where did most of the chemical elements that make up our bodies come from?

A) The Sun B) Vanished Stars C) The Big Bang D) Other planets Answer: B Diff: 1 Section Ref: 1.1 20) Which of the following can be described as the totality of all space, time, matter, and energy?

A) The universe B) Astronomy C) The Milky Way D) The Earth E) The solar system Answer: A Diff: 1 Section Ref: 1.1 21) About how many stars are visible on a clear, dark night with the unaided eye alone?

A) A few dozen B) A few hundred C) A few thousand D) Tens of thousands E) Millions and millions Answer: C Diff: 1 Section Ref: 1.2

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22) Into how many constellations is the celestial sphere divided?

A) 12 B) 44 C) 57 D) 88 E) 110 Answer: D Diff: 1 Section Ref: 1.2 23) What are constellations?

A) Groups of galaxies gravitationally bound and close together in the sky B) Groups of stars making an apparent pattern in the celestial sphere C) Groups of stars gravitationally bound and appearing close together in the sky D) Ancient story boards, useless to modern astronomers E) Apparent groupings of stars and planets visible on a given evening Answer: B Diff: 2 Section Ref: 1.2 24) Where on Earth would you be if Polaris were directly overhead?

A) North Pole B) Arctic Circle C) Tropic of Cancer D) Equator E) It lies overhead everywhere on Earth.

Answer: A Diff: 2 Section Ref: 1.2 25) Where on Earth can you observe all the stars in the sky over an entire year?

A) North Pole B) Arctic Circle C) Tropic of Cancer D) Equator E) Everyone on Earth can see the whole sky.

Answer: D Diff: 2 Section Ref: 1.2

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26) How many arc seconds are in a degree?

A) 60 B) 3600 C) 600 D) 86400 E) None; seconds measure time and degrees measure temperature.

Answer: B Diff: 2 Section Ref: 1.2 27) The angular size of an object depends on which two quantities?

A) The object's actual size and its mass B) The object's distance from us and its brightness C) The object's actual size and its distance from us D) The object's brightness and its mass Answer: C Diff: 2 Section Ref: 1.2 28) While watching a star, you see it moves 15 degrees across the sky. How long have you been watching it?

A) 1 hour B) 3 hours C) 15 minutes D) 15 seconds E) 1 minute Answer: A Diff: 2 Section Ref: 1.3

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29) This diagram explains

A) the difference between solar time and sidereal time.

B) precession.

C) the solar day's relation to the Moon.

D) the sidereal day's relation to the seasons.

Answer: A Diff: 1 Section Ref: 1.3 30) How long is the precession cycle?

A) 1 day B) 29.5 days C) 365.24 days D) 18 years, 11.3 days E) 26,000 years Answer: E Diff: 1 Section Ref: 1.3

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31) The place the Sun stops its northward motion along the ecliptic is the A) equator.

B) prime meridian.

C) summer solstice.

D) vernal equinox.

Answer: C Diff: 1 Section Ref: 1.3 32) The places where the Sun crosses the equator are called the A) annalemmas.

B) prime meridians.

C) zeniths.

D) equinoxes.

E) solstices.

Answer: D Diff: 1 Section Ref: 1.3 33) Seasons on Earth are primarily caused by A) the distance from the Earth to the Sun. B) the tilt of the Earth's rotational axis.

C) the tilt of the Earth's magnetic axis.

D) the precession of the Earth's rotational axis.

E) the dates of the solstices and equinoxes.

Answer: B Diff: 1 Section Ref: 1.3 34) A year is defined as A) the time it takes for Earth to complete a rotation on its axis.

B) the time it takes for the Moon to complete an orbit of Earth.

C) the time it takes for the Moon to complete a phase cycle.

D) the time it takes for Earth to complete an orbit around the Sun. E) the time it takes for the Sun to complete an orbit around Earth.

Answer: D Diff: 2 Section Ref: 1.3

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35) From a location in the United States of America, a star is observed to be rising due East.

Where will this star be located 6 hours later?

A) Directly overhead B) High in the Northern sky C) High in the southern sky D) Setting due West E) The location of the star cannot be determined from the information given.

Answer: C Diff: 2 Section Ref: 1.3 36) Which statement about the ecliptic is FALSE? A) The Sun appears to move about a degree per day eastward long it.

B) It is tilted 23.5 degrees with respect to the equator.

C) The year is marked by the Sun's return to the same place along it.

D) The Moon can never leave it, but moves twelve times faster than the Sun. E) The major planets stay close to it, but not always on it.

Answer: D Diff: 2 Section Ref: 1.3 37) You note that a particular star is directly overhead. It will be directly overhead again in A) 1 hour.

B) 12 hours.

C) 23 hours 56 minutes.

D) 24 hours.

E) 24 hours 4 minutes.

Answer: C Diff: 2 Section Ref: 1.3 38) That Polaris will not always be the pole star is due to A) the sidereal day being shorter than the solar day.

B) precession shifting the celestial pole.

C) the Moon following the ecliptic, instead of the equator.

D) the Earth's revolution being slightly less than exactly 365.25 days.

E) the Solar winds blowing the Earth farther away from the Sun. Answer: B Diff: 2 Section Ref: 1.3

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39) What celestial line is a product of the Earth's orbit around the Sun? A) Ecliptic B) Prime Meridian C) Equator D) Galactic Plane E) Analemma Answer: A Diff: 2 Section Ref: 1.3 40) Where would you be if the Sun sets for six continuous months, beginning about September 23rd?

A) North Pole B) Arctic Circle C) Equator D) Antarctic Circle E) South Pole Answer: A Diff: 2 Section Ref: 1.3 41) Where would you be if the Sun passes directly overhead on December 21st?

A) Equator B) Tropic of Cancer C) Tropic of Capricorn D) Antarctic Circle E) South Pole Answer: C Diff: 3 Section Ref: 1.3 42) The constellations of the zodiac fall along A) the ecliptic.

B) the celestial equator.

C) lines of longitude.

D) lines of latitude.

Answer: A Diff: 1 Section Ref: 1.3

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43) When the Sun rises it is located in the constellation Gemini. When the Sun sets later that same day it will be A) in the constellation Aries.

B) in the constellation Taurus.

C) in the constellation Gemini.

D) in the constellation Cancer.

E) in the constellation Leo. Answer: C Diff: 3 Section Ref: 1.3 44) If the Moon rose tonight at 6 PM, then tomorrow it will rise about A) the same time.

B) 7 PM. C) 5 PM. D) dawn.

E) midnight.

Answer: B Diff: 1 Section Ref: 1.4 45) Which statement about the first quarter Moon is FALSE? A) It rises about noon.

B) From the Earth, it appears 25% sunlit.

C) It is the half Moon of the evening sky.

D) It is highest in the sky at sunset.

E) It occurs about a week after new Moon.

Answer: B Diff: 2 Section Ref: 1.4 46) If new Moon fell on March 2nd, what is the Moon's phase on March 14th?

A) Waxing crescent B) First quarter C) Waxing gibbous D) Full E) Waning crescent Answer: C Diff: 2 Section Ref: 1.4

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47) Why is there a two-day difference in the sidereal and synodic months?

A) The Moon speeds up at perigee, and slows down at apogee.

B) The sidereal day is four minutes shorter than the solar day, and it adds up.

C) The Earth is closer to the Sun during the sidereal month.

D) The Earth is also revolving around the Sun, so the Moon must "catch up."

E) The Moslem lunar year is only 354 days long, on average.

Answer: D Diff: 2 Section Ref: 1.4 48) The Last Quarter phase of the Moon A) rises at sunrise.

B) sets at sunrise.

C) crosses the meridian at sunrise.

D) rises at sunset.

E) sets at sunset.

Answer: C Diff: 2 Section Ref: 1.4 49) A solar eclipse can only happen during a A) new Moon.

B) solstice.

C) first quarter Moon.

D) full Moon.

E) perihelion passage of the Sun. Answer: A Diff: 1 Section Ref: 1.5 50) A lunar eclipse can only happen during a A) new Moon.

B) equinox.

C) full Moon.

D) perigee.

E) aphelion.

Answer: C Diff: 1 Section Ref: 1.5

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51) If you are in the Moon's umbral shadow, then you will witness A) nighttime.

B) a total solar eclipse.

C) a total lunar eclipse.

D) a partial solar eclipse.

E) some kind of lunar eclipse.

Answer: B Diff: 1 Section Ref: 1.5 52) What conditions are necessary for an annular solar eclipse?

A) New Moon on equator at perigee B) Full Moon on ecliptic at perihelion C) New Moon on ecliptic at perigee D) New Moon on equator at apogee E) New Moon on ecliptic at apogee Answer: E Diff: 2 Section Ref: 1.5 53) What conditions are necessary for a total solar eclipse?

A) New Moon on ecliptic near perigee B) Full Moon on ecliptic near aphelion C) New Moon on equator at perigee D) Full Moon on equator at perigee E) New Moon on ecliptic near aphelion Answer: A Diff: 2 Section Ref: 1.5 54) What conditions are necessary for a partial solar eclipse?

A) New Moon on ecliptic, with us in the penumbral shadow B) Full Moon on equator, with us in the umbral shadow C) New Moon at perigee D) Full Moon at apogee E) First or third quarter Moon crossing the ecliptic Answer: A Diff: 2 Section Ref: 1.5

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55) Some type of solar eclipse will happen about A) every month at new Moon.

B) every week at full Moon.

C) every month at full Moon.

D) about every six months at new Moon.

E) every year at new Moon.

Answer: D Diff: 3 Section Ref: 1.5 56) Modern scientific theories are NOT A) testable.

B) continuously tested.

C) simple.

D) perfect.

E) elegant.

Answer: D Diff: 1 Section Ref: 1.6 57) An effective theory must A) have been proven.

B) must have been around for centuries or longer.

C) be continuously tested.

D) include mathematical formulae.

Answer: C Diff: 2 Section Ref: 1.6 58) Aristotle's hypothesis was that A) lunar eclipses were created by our shadow.

B) only a spherical Earth would always cast a circular shadow on the Moon.

C) lunar eclipses would have to happen every full Moon.

D) the Sun lay at the center of the planet orbits.

E) the Moon orbited the Earth.

Answer: B Diff: 2 Section Ref: 1.6 59) The distances to other stars are best measured in ________.

Answer: light-years Diff: 1 Section Ref: 1.1

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60) The Milky Way galaxy contains about ________ stars.

Answer: 100 billion Diff: 1 Section Ref: 1.1 61) The ________ of the Earth causes the Sun and Moon to rise in the east and set in the west.

Answer: rotation Diff: 1 Section Ref: 1.1 62) The ________ is the totality of all space, time, matter, and energy.

Answer: universe Diff: 1 Section Ref: 1.1 63) The celestial sphere appears to move fastest above the ________.

Answer: equator Diff: 1 Section Ref: 1.2 64) Early astronomers picture the Earth as stationary, with the ________ spinning, moving the stars along with it.

Answer: celestial sphere Diff: 2 Section Ref: 1.2 65) The Sun's lowest position in the sky occurs at the ________.

Answer: winter solstice Diff: 1 Section Ref: 1.4 66) The two days when the Sun rises due east and sets due west are the ________.

Answer: equinoxes.

Diff: 1 Section Ref: 1.4 67) The four extra minutes in the solar day are due to our ________ around the Sun. Answer: revolution Diff: 1 Section Ref: 1.4 68) A solar eclipse can only happen during a ________ Moon.

Answer: new Diff: 2 Section Ref: 1.5

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69) A solar eclipse can only happen during a ________ Moon.

Answer: full Diff: 2 Section Ref: 1.5 70) A ________ is a framework of ideas and assumption used to explain some set of observations and make predictions about the real world.

Answer: theory Diff: 1 Section Ref: 1.6 71) If a theory is testable, its underlying ________ and its ________ can be exposed to experimental verification.

Answer: assumptions; predictions Diff: 2 Section Ref: 1.6 72) What is the name of the point on the celestial sphere that all stars seem to circle around, when viewing the sky from North America?

Answer: North Celestial Pole Diff: 3 Section Ref: 1.2 73) How far above or below the ecliptic can the Sun move?

Answer: The Sun follows the ecliptic eastward across the sky, never leaving it.

Diff: 2 Section Ref: 1.2 74) Which is longer, the sidereal or solar day? By how much?

Answer: The solar day is approximately four minutes longer than the sidereal day.

Diff: 1 Section Ref: 1.2 75) How far above and below the celestial equator can the Sun move?

Answer: The Sun never appears more than 23.5 degrees above or the below the celestial equator.

Diff: 2 Section Ref: 1.3 76) If intending to teach his students the constellations by season, why would an astronomy instructor be advised to always assign the stars in the current western sky at the beginning of each term?

Answer: As the Earth revolves around the Sun, the Sun appears to move one degree eastward per day. These stars are, therefore, soon lost in the Sun's glare.

Diff: 2 Section Ref: 1.3

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77) If the bright star Sirius transits my local meridian tonight at 6:43 PM, when will it transit tomorrow?

Answer: At 6:39 PM tomorrow night, as the Earth spins once in a sidereal day Diff: 3 Section Ref: 1.3 78) If the Moon rises exactly at sunset, what will its phase be? Why? Answer: The phase will be full because it is rising opposite the Sun. If the Moon is directly opposite the Sun in the sky, its phase will be full.

Diff: 2 Section Ref: 1.4 79) The first quarter Moon rises about noon today; what will its phase be, and when will it rise tomorrow?

Answer: It will be waxing gibbous, and rise about 1 PM by the next day.

Diff: 2 Section Ref: 1.4 80) Why are some solar eclipses total, and others annular?

Answer: The Moon's orbit is not a perfect circle. When the Moon is closer to Earth it is big enough to cover the Sun completely; when it it is too far away it appears smaller, so a ring of sunlight is still seen.

Diff: 2 Section Ref: 1.5 81) In what sense is our unique Earth just "ordinary" from a cosmic perspective?

Answer: We are not in the center of our solar system, which is not in the center of the Milky Way, which is just one of billions of known galaxies in the universe. Our planet is made of common minerals that are abundant throughout the known universe, and are probably part of almost any planet forming around any other star now.

Diff: 2 Section Ref: 1.1 82) Of all visible objects in the celestial sphere, which appears to move the least? Why? Answer: Polaris, because it lies very close to the north celestial pole, making everything else seem to revolve around it as the Earth rotates on its axis daily.

Diff: 2 Section Ref: 1.2 83) What is the significance of the zodiacal signs, and why can all twelve not be seen on a given night?

Answer: They are twelve constellations along the ecliptic, the apparent path of the Sun. Thus the Sun's glare will typically hide at least two of them at any given time.

Diff: 2 Section Ref: 1.4

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84) Why are summers hotter than winters? Relate this to the Sun's position in the celestial sphere and the length of the days.

Answer: The Sun is 47 degrees higher in the noon sky for northern hemisphere observers in June than in December, and also gives several extra hours of daylight as well.

Diff: 2 Section Ref: 1.4 85) What are some observable consequences of the Earth's revolution around the Sun in relation to the zodiacal constellations?

Answer: Month by month, our revolution causes the Sun to appear to move eastward by about a degree per day, or through a new sign of the zodiac every month.

Diff: 3 Section Ref: 1.4 86) Why can many more people witness a total lunar eclipse than a total solar eclipse?

Answer: For a total solar eclipse to be seen, the observer must be in the Moon's umbra, a shadow only about a hundred miles across, while everyone on the night side of the Earth can look up to witness the full Moon moving though our shadow.

Diff: 2 Section Ref: 1.5 87) How did Aristotle apply the scientific method to lunar eclipses?

Answer: He noted that during all lunar eclipses, the Earth always casts a circular shadow considerably larger than the Moon's disk, so hypothesized the Earth was in fact a sphere and predicted that future eclipses would show the same curved shadow of Earth.

Diff: 2 Section Ref: 1.6 88) Describe how Erastothenes measured the circumference of our planet.

Answer: Using the fact that the noon solstice Sun was directly overhead at Syene, on the Tropic of Cancer, yet was 7 degrees south of his zenith in Alexandria, Erastothenes realized this was due to the curvature of the Earth, and that the 7 degrees was about 1/50th of the Earth's total circumference, so the Earth must be about fifty times larger in circumference than the 800 kilometer separation between Alexandria and Syene, or about 40,000 kilometers around.

Diff: 3 Section Ref: 1.6

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 2 Light and Telescopes 1) You would perceive a change in a visible light wave's amplitude as a change in its color.

Answer: FALSE Diff: 1 Section Ref: 2.1 2) Gamma Rays are a type of electromagnetic radiation.

Answer: TRUE Diff: 1 Section Ref: 2.1 3) X-rays travel at a greater speed than radio waves.

Answer: FALSE Diff: 1 Section Ref: 2.1 4) Wave energy can only be transmitted through a material medium.

Answer: FALSE Diff: 2 Section Ref: 2.1 5) As white light passes through a prism, the red (longer) wavelengths bend less than the blue (shorter) wavelengths, so forming the rainbow of colors.

Answer: TRUE Diff: 2 Section Ref: 2.2 6) Observations in the X-ray portion of the spectrum are routinely done from the surface of the Earth.

Answer: FALSE Diff: 2 Section Ref: 2.2 7) A blue star has a higher surface temperature than a red star.

Answer: TRUE Diff: 1 Section Ref: 2.3 8) In blackbody radiation, the energy is radiated uniformly in every region of the spectrum, so the radiating body appears black in color.

Answer: FALSE Diff: 2 Section Ref: 2.3

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9) As a star's temperature increases, the frequency of peak emission also increases.

Answer: TRUE Diff: 2 Section Ref: 2.3 10) An observer will measure the wavelength of waves emanating from a source that is moving away as longer than it really is.

Answer: TRUE Diff: 2 Section Ref: 2.3 11) The absorption lines for a cool thin gas are identical in color and energy to the emission lines of the same gas if hot enough to glow.

Answer: TRUE Diff: 1 Section Ref: 2.4 12) The spectral lines of each element are distinctive to that element, whether we are looking at emission or absorption lines.

Answer: TRUE Diff: 1 Section Ref: 2.4 13) The shorter a wave's wavelength, the greater its energy.

Answer: TRUE Diff: 1 Section Ref: 2.5 14) The red hydrogen alpha line carries more energy per photon than the blue-green hydrogen beta line does.

Answer: FALSE Diff: 2 Section Ref: 2.5 15) In an atom, electrons can have only specific, allowed orbital energies.

Answer: TRUE Diff: 1 Section Ref: 2.5 16) An X-ray photon has more energy than a visible photon.

Answer: TRUE Diff: 2 Section Ref: 2.5

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17) Molecular spectra, like elemental ones, involve only the vibration of the particles.

Answer: FALSE Diff: 2 Section Ref: 2.5 18) The primary purpose of an astronomical telescope is to magnify the images of distant objects, making them appear closer.

Answer: FALSE Diff: 1 Section Ref: 2.6 19) The light gathering ability of a telescope is most dependent on the diameter of its primary objective.

Answer: TRUE Diff: 1 Section Ref: 2.6 20) All radio telescopes are reflectors in design.

Answer: TRUE Diff: 2 Section Ref: 2.7 21) In addition to visible light, Hubble can do some work in the infrared and ultraviolet portions of the spectrum.

Answer: TRUE Diff: 2 Section Ref: 2.8 22) Due to our ozone layer, ultraviolet astronomy must be done from space.

Answer: TRUE Diff: 2 Section Ref: 2.8 23) A wave's velocity is the product of the A) frequency times the period of the wave.

B) period times the energy of the wave.

C) amplitude times the frequency of the wave.

D) frequency times the wavelength of the wave.

E) amplitude times the wavelength of the wave.

Answer: D Diff: 1 Section Ref: 2.1

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24) The number of waves passing the observer per second is A) the wavelength in angstroms.

B) the amplitude in nm.

C) the frequency in Hertz.

D) the period in seconds.

E) the energy in milliwatts.

Answer: C Diff: 1 Section Ref: 2.1 25) Consider this diagram. Which statement is TRUE?

A) The wavelength is 4.

B) The wavelength is 6.

C) The wavelength is 8.

D) The wavelength is 12.

E) The wavelength cannot be determined from this diagram.

Answer: B Diff: 2 Section Ref: 2.1 26) Consider this diagram. Which statement is TRUE?

A) The amplitude is 4.

B) The amplitude is 6.

C) The amplitude is 8.

D) The amplitude is 12.

E) The amplitude cannot be determined from this diagram.

Answer: A Diff: 2 Section Ref: 2.1

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27) If a wave's frequency doubles, its wavelength A) is halved.

B) is also doubled.

C) is unchanged, as c is constant.

D) is now 4 times longer.

E) becomes 16 times longer.

Answer: A Diff: 2 Section Ref: 2.1 28) Which of these is constant for ALL types of electromagnetic radiation in a vacuum?

A) Amplitude B) Wavelength C) Frequency D) Velocity E) Photon energy Answer: D Diff: 1 Section Ref: 2.1 29) Of all the forms of electromagnetic radiation, the one with the lowest frequency is A) gamma rays.

B) ultraviolet rays.

C) visible light.

D) microwaves.

E) radio waves.

Answer: E Diff: 1 Section Ref: 2.2 30) The two forms of electromagnetic radiation that penetrate the atmosphere best are A) X-rays and gamma rays.

B) ultraviolet and visible light.

C) visible and infrared light.

D) visible and radio waves.

E) infrared and microwaves.

Answer: D Diff: 1 Section Ref: 2.2

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31) The visible color of electromagnetic radiation that has the shortest wavelength is A) red.

B) orange.

C) green.

D) blue.

E) violet.

Answer: E Diff: 2 Section Ref: 2.2 32) Which type of radiation can be observed well from Earth's surface?

A) Gamma ray B) X-ray C) Ultraviolet D) Visible E) Infrared Answer: D Diff: 3 Section Ref: 2.2 33) The temperature scale that places zero at the point where all atomic and molecular motion ceases is A) Fahrenheit.

B) Celsius.

C) Kelvin.

D) centigrade.

E) Ransom.

Answer: C Diff: 2 Section Ref: 2.3 34) The hottest objects with temperatures in the millions of Kelvins, give off most of their radiation in which part of the electromagnetic spectrum?

A) Visible B) Radio C) Ultraviolet D) X-ray E) Gamma ray Answer: D Diff: 2 Section Ref: 2.3

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35) What is TRUE of a blackbody?

A) It appears black to us, regardless of its temperature.

B) Its energy is not a continuum.

C) Its energy peaks at the wavelength determined by its temperature.

D) If its temperature doubled, the peak in its curve would be doubled in wavelength.

E) It has a complete absence of thermal energy.

Answer: C Diff: 1 Section Ref: 2.3 36) The wavelength at which a blackbody radiates most depends on its A) radius.

B) mass.

C) magnetic fields.

D) temperature.

E) direction of motion.

Answer: D Diff: 2 Section Ref: 2.3 37) Stars like our Sun emit most of their light in which part of the electromagnetic spectrum?

A) The visible B) The X-ray C) The ultraviolet D) The radio E) The infrared Answer: A Diff: 2 Section Ref: 2.3

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38) To see the Sun's hot corona (a temperature of 1,000,000 K), which part of the electromagnetic spectrum should one observe?

A) The visible B) The X-ray C) The ultraviolet D) The radio E) The infrared Answer: B Diff: 2 Section Ref: 2.3 39) The Doppler Effect is a phenomenon that allows one to measure an object's A) temperature.

B) radius.

C) line-of-sight speed.

D) chemical composition.

Answer: C Diff: 1 Section Ref: 2.3 40) The light from an object moving tangentially (to your left or right) will exhibit A) a blueshift.

B) a redshift.

C) a shift in peak wavelength towards the red.

D) a shift in peak wavelength towards the blue.

E) no shift.

Answer: E Diff: 2 Section Ref: 2.3 41) If a light source is approaching you at a speed very close to the speed of light, it will appear A) redder than it is.

B) bluer than it is.

C) brighter than it is.

D) fainter than it is.

E) lower temperature than it is.

Answer: B Diff: 2 Section Ref: 2.3

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42) What is spectroscopy?

A) An analysis of the way in which atoms absorb and emit light B) A study of the geometry of rainbows C) An observational technique to measure the brightness of light at different colors D) The use of CCDs to capture light more efficiently than with photographic film E) A method to freeze atmospheric turbulence for better resolution Answer: A Diff: 1 Section Ref: 2.4 43) The Orion Nebula, M-42, is a hot, thin cloud of glowing gas, so its spectrum is A) a continuum, strongest in the color red.

B) a few bright lines against a dark background.

C) a few dark lines in the continuum.

D) a continuum, but with both bright and dark lines mixed in.

E) not in the visible portion of the spectrum.

Answer: B Diff: 2 Section Ref: 2.4 44) A neon light (thin hot neon gas in a sealed tube) gives us A) a continuous spectrum, since the neon is hot enough to glow.

B) a few bright emission lines, telling us the gas is neon.

C) a continuum, with dark lines identifying the neon atoms that are present.

D) a lot of random bright red lines due to the motion of the hot atoms.

E) nothing visible to us, but a lot of infrared lines as heat.

Answer: B Diff: 2 Section Ref: 2.4 45) A hydrogen atom consists of an electron and a(n) A) proton.

B) ion.

C) neutrino.

D) neutron.

E) lepton.

Answer: A Diff: 1 Section Ref: 2.5

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46) An emission spectrum can be used to identify a(n) A) proton.

B) electron.

C) neutron.

D) atom.

E) neutrino.

Answer: D Diff: 1 Section Ref: 2.5 47) The classical model of the hydrogen atom that explains its spectral line structure is due to A) Kirchhoff.

B) Bohr.

C) Fraunhofer.

D) Newton.

E) Mendeleev.

Answer: B Diff: 1 Section Ref: 2.5 48) In Bohr's model of the atom, electrons A) only make transitions between orbitals of specific energies.

B) are not confined to specific orbits.

C) are spread uniformly through a large, positive mass.

D) can be halfway between orbits.

E) move from orbit to orbit in many small steps.

Answer: A Diff: 2 Section Ref: 2.5 49) Why are molecular lines more complex than elemental spectral lines?

A) Molecules have two or more atoms.

B) Molecules can vibrate and rotate as well.

C) Molecules are heavier than atoms.

D) Molecules are the basis of life.

E) Most of the universe is made of molecules, not individual atoms.

Answer: B Diff: 2 Section Ref: 2.5

10 ..

50) What is the primary purpose of an astronomical telescope?

A) To magnify and make distant objects appear closer.

B) To separate light into its component colors.

C) To measure the intensity of light very accurately.

D) To access wavelengths that we cannot see visually.

E) To collect a lot of light and bring it to a focus.

Answer: E Diff: 1 Section Ref: 2.6 51) What is the resolution of a telescope?

A) Its ability to see very faint objects B) Its ability to distinguish two adjacent objects close together in the sky C) Its ability to make distant objects appear much closer to us D) Its ability to separate light into its component colors for analysis E) Its ability to focus more than just visible light for imaging Answer: B Diff: 1 Section Ref: 2.6 52) What is the light-gathering power of an 8-inch telescope compared to a 4-inch telescope?

A) 2× better B) 4× better C) 8× better D) 16× better E) 32× better Answer: B Diff: 2 Section Ref: 2.6 53) What are two advantages of large scopes over smaller ones?

A) Large scopes have a larger field of view and sharper focus.

B) Large scopes are not subject to atmospheric turbulence and opacity like smaller ones.

C) Large scopes are easier to mount and control than small ones.

D) Large telescope have more light gathering power and better resolution.

E) Large telescopes give higher magnification and are easier to build.

Answer: D Diff: 2 Section Ref: 2.6

11 ..

54) What problem does adaptive optics correct?

A) Defects in the optics of the telescope, such as the original Hubble mirror B) The opacity of the Earth's atmosphere to some wavelengths of light C) The light pollution of urban areas D) Turbulence in the Earth's atmosphere which creates twinkling E) Chromatic aberration due to use of only a single lens objective Answer: D Diff: 2 Section Ref: 2.6 55) What is TRUE of radio telescopes?

A) They have poorer angular resolution than a refractor.

B) They have better angular resolution than a reflector.

C) They are the smallest, most compact telescopes.

D) They can only be used above the atmosphere.

E) They are most sensitive to the opacity of the ozone layer.

Answer: A Diff: 1 Section Ref: 2.7 56) Which of the following is a problem inherent in all large radio telescopes?

A) They are badly affected by poor seeing and atmospheric turbulence.

B) The lightest breeze shakes them, making the observations blurry.

C) Their waves are blocked by water vapor, so they must be located in deserts.

D) Radio waves have long wavelengths, so radio telescopes have poor resolution.

E) The dust clouds in the Milky Way block almost all wavelengths except light.

Answer: D Diff: 2 Section Ref: 2.7 57) Radio dishes are large in order to A) attract funding from NASA and the NSF. B) give greater magnification.

C) increase their angular resolution and collect the very weak radio photons.

D) increase the range of waves they can collect.

E) detect shorter waves than optical telescopes for superior resolution.

Answer: C Diff: 2 Section Ref: 2.7

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58) Compared to optical telescopes, radio telescopes are built large because A) they're less expensive to make than optical telescopes.

B) radio photons don't carry much energy.

C) atmospheric turbulence is more of a problem.

D) radio sources are harder to find.

E) radio waves are absorbed by the atmosphere.

Answer: B Diff: 3 Section Ref: 2.7 59) In astronomy, an interferometer can be used to A) yield better seeing conditions with optical telescopes.

B) decrease the effects of light pollution in getting darker sky backgrounds.

C) improve the angular resolution of radio telescopes.

D) increase the sensitivity of infrared telescopes to longer wavelengths.

E) speed up the processing of CCD images.

Answer: C Diff: 2 Section Ref: 2.7 60) This design combines the radiation from two different telescopes to greatly enhance resolution via computer synthesis.

A) Cassegrain reflector B) Newtonian reflector C) Prime focus reflector D) Refractor E) Interferometer Answer: E Diff: 2 Section Ref: 2.7 61) Which of the following greatly improves the angular resolution of radio maps?

A) Schmidt corrector plates B) More sensitive spectrometers C) Switching from film to CCD imaging D) Use of interferometers E) Chilling the infrared detectors Answer: D Diff: 2 Section Ref: 2.7

13 ..

62) Advantages of radio astronomy include A) radio waves are not scattered or deflected by Earth's atmosphere.

B) radio observations can be made even when the Sun is in the sky.

C) radio observations can be made even when the sky is obscured by clouds.

D) radio observations let astronomers study things that emit little visible light.

E) all of the above.

Answer: E Diff: 1 Section Ref: 2.7 63) A typical space telescope is operated by how many astronauts?

A) 7 B) 5 C) 3 D) 1 E) 0 Answer: E Diff: 1 Section Ref: 2.8 64) The gas between stars that has a temperature below a few hundred kelvins is best studies with which kind of telescope?

A) Radio B) Infrared C) Optical D) Ultraviolet E) X-ray Answer: B Diff: 1 Section Ref: 2.8 65) In which part of the electromagnetic spectrum have astronomers been unable to get any information?

A) Gamma rays B) X-rays C) Ultraviolet D) Microwaves E) We now can access information in all spectral lengths.

Answer: E Diff: 1 Section Ref: 2.8

14 ..

66) The design of modern X-ray telescopes depends on A) lenses made of germanium.

B) the prime focus design, with mirrors made of iron.

C) grazing incidence optics.

D) achromatic lenses to keep the X-rays in focus.

E) the Cassegrain design, with mirrors made of lead.

Answer: C Diff: 2 Section Ref: 2.8 67) The product of the wavelength times the frequency of a wave is its ________.

Answer: velocity Diff: 1 Section Ref: 2.1 68) In a wave, the distance from peak to peak is called the wave's ________.

Answer: wavelength Diff: 2 Section Ref: 2.1 69) The part of the electromagnetic spectrum with the shortest wavelengths is called ________.

Answer: gamma rays or gamma Diff: 2 Section Ref: 2.2 70) ________ is the color of the lowest frequency visible light.

Answer: Red Diff: 1 Section Ref: 2.2 71) The Earth's atmosphere is transparent to ________, as well as some radio and near-infrared wavelengths.

Answer: visible light Diff: 2 Section Ref: 2.2 72) The Sun's blackbody curve peaks in the ________ portion of the spectrum.

Answer: visible Diff: 1 Section Ref: 2.3 73) Stars that appear blue or white in color are ________ than our yellow Sun. Answer: hotter Diff: 1 Section Ref: 2.3

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74) Knowing the peak emission wavelength of a blackbody allows you to determine its ________.

Answer: temperature Diff: 2 Section Ref: 2.3 75) ________ is the scientific study of the distribution of electromagnetic waves by energy and how these patterns are created in atoms and molecules.

Answer: Spectroscopy Diff: 1 Section Ref: 2.4 76) The emission line for a given atom shows spectral features at the ________ location as in its absorption spectrum.

Answer: same Diff: 1 Section Ref: 2.4 77) The colors of a neon light arise because it is a(n) ________ spectrum.

Answer: emission (or bright line) Diff: 2 Section Ref: 2.4 78) The longer the wavelength of the photon, the ________ the energy it carries.

Answer: lower Diff: 1 Section Ref: 2.5 79) Because the changes in energy levels happen in discrete steps, we refer to these as ________ leaps.

Answer: quantum Diff: 1 Section Ref: 2.5 80) The spectra of molecules are more complex because molecules can vibrate and ________ instead of just exhibiting electronic transitions like atoms.

Answer: rotate Diff: 2 Section Ref: 2.5 81) The light-gathering power of a telescope varies with the ________ of the diameter of the lens or mirror.

Answer: square Diff: 1 Section Ref: 2.6

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82) The ability of a telescope to separate two closely spaced stars is called ________.

Answer: resolution Diff: 2 Section Ref: 2.6 83) Radio astronomy uses ________ to achieve better resolution than optical telescopes.

Answer: interferometry Diff: 1 Section Ref: 2.7 84) Radio telescopes image a universe much ________ in temperature than with visible light.

Answer: colder Diff: 2 Section Ref: 2.7 85) It takes ________ astronauts to operate the Hubble Space Telescope.

Answer: zero Diff: 1 Section Ref: 2.8 86) No one can hear you scream (or fire a weapon) in space, regardless of the Hollywood special effects. Explain why.

Answer: Sound waves must travel though a material medium, and cannot pass through a vacuum. The blast might be seen, but the boom will not be heard.

Diff: 1 Section Ref: 2.1 87) How do sound and light waves differ?

Answer: Sound waves travel much slower, and need a physical medium, such as air, to be transmitted. Light travels best in the vacuum of space.

Diff: 2 Section Ref: 2.1 88) Describe the relationship between frequency and wavelength.

Answer: The higher the frequency, the shorter the wavelength.

Diff: 2 Section Ref: 2.1 89) What two regions of the electromagnetic spectrum are best utilized by ground-based astronomers, and why?

Answer: The atmosphere is opaque to most radiation except visible and radio waves.

Diff: 2 Section Ref: 2.2

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90) What do infrared and ultraviolet waves have in common? How do they differ?

Answer: Both are forms of electromagnetic radiation, both travel at c in a vacuum, and both are largely absorbed by our atmosphere. They differ greatly in frequency, wavelength, and photon energy, however, with UV much more penetrating than IR, as anyone who has experienced a sunburn is aware.

Diff: 2 Section Ref: 2.2 91) What information about a star can be inferred from its Doppler shift?

Answer: The Doppler shift gives the star's velocity along our line-of-sight, either towards or away from us.

Diff: 2 Section Ref: 2.3 92) State the relationship between photon energy, frequency, and wavelength.

Answer: The higher the frequency, the greater the energy the photon carries, but the shorter its wavelength.

Diff: 2 Section Ref: 2.5 93) Explain how Bohr's model creates emission and absorption lines in the spectrum.

Answer: Bohr's model has the electron orbitals quantized into discrete energies. Each upward transition to a higher energy state produces an absorption line (energy is absorbed). Each downward transition produces an emission line (energy is given off). The energy absorbed or emitted is exactly equal to the difference in energy levels.

Diff: 3 Section Ref: 2.5 94) Why doesn't the Hubble Space Telescope need adaptive optics?

Answer: Adaptive optics correct poor seeing in our atmosphere, but above the atmosphere, Hubble always has perfect seeing and sharp images all the time.

Diff: 3 Section Ref: 2.6 95) Why do stars appear to twinkle?

Answer: In space, the light of the stars appears steady and images are sharp. But in passing through our atmosphere, the narrow shafts of star light are shifted constantly by turbulence, hence the images dance around in the eyepiece for us on the ground.

Diff: 1 Section Ref: 2.6 96) Why is the angular resolution of radio telescopes much worse than that of smaller optical telescopes?

Answer: Radio waves are much longer in wavelength than light waves, so they carry little energy, and a lot of them are needed for sharp images.

Diff: 2 Section Ref: 2.7 18 ..

97) Why do gamma ray telescopes have poor angular resolution?

Answer: Because scientists have not yet developed a way to focus these.

Diff: 2 Section Ref: 2.8 98) Why is UV astronomy difficult to do from the ground?

Answer: The atmosphere blocks most of the UV waves before they reach the ground. In order to see a wide range of UV wavelengths, you have to get very high in the atmosphere, such as with a balloon observatory, or above the atmosphere.

Diff: 2 Section Ref: 2.8 99) What is meant by the wavelength of light? By its frequency? Explain how they are related to each other.

Answer: The wavelength is the distance between successive wave crests, while the frequency is the number of waves that pass the observer per second. All forms of EM radiation travel in a vacuum at 300,000 km/sec., and this velocity is the product of the wavelength X the frequency of the radiation.

Diff: 2 Section Ref: 2.1 100) What is white light? Why do we perceive different colors with a prism?

Answer: White light is composed of all the colors blended together uniformly. The colors are all present, as is shown when a prism spreads them back apart; each color corresponds to a different wavelength of EM radiation.

Diff: 3 Section Ref: 2.2 101) How can a star's blackbody spectrum be used to determine the temperature of a star?

Answer: Careful analysis of the blackbody curve of the star's entire radiation spectrum will reveal a peak that is unique to a given photospheric temperature. Basically, the bluer the star's radiation, the hotter its surface will be.

Diff: 1 Section Ref: 2.3 102) Why would a hotter star appear blue-white while a cooler star appear red or not be visible at all?

Answer: The hotter the star the shorter the wavelength it peaks at. A star that emits light across the entire visible spectrum would appear white. One that peaked beyond the visible would appear blue-white. A cooler star may peak in the red part of the spectrum, or even in the infrared.

Diff: 2 Section Ref: 2.3

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103) Give an example of the Doppler Effect being used in a baseball game.

Answer: The Doppler "gun" can focus on the motion of the baseball, and give us the speed that the pitcher is delivering it to the plate.

Diff: 1 Section Ref: 2.3 104) Give and explain an example of the use of the Doppler Effect on the highway.

Answer: The radar gun of a highway patrolman sends out a pulsed beam to be reflected back, thus giving the speed of your car and perhaps netting you a ticket.

Diff: 2 Section Ref: 2.3 105) Why is spectroscopy important to astronomers?

Answer: Virtually all the information we receive about the universe comes in the form of electromagnetic waves, such as light waves. Analyzing the light with spectroscopy can give us the temperature, composition, and motion of the source, so this is the basis of modern astrophysics.

Diff: 1 Section Ref: 2.4 106) Define absorption and emission lines.

Answer: Absorption: When light from a continuous source, such as the dense photosphere of a star, is passed though a thin, cool gas, certain energies from the continuum are absorbed, depending on which elements are present, creating a pattern of dark lines which identify the elements and molecules present in the cool gas cloud. Emission: A hot, thin gas cools off by emitting photons, but only at discrete wavelengths determined by the electron transitions downward of the component atoms. These appear as a pattern of bright emission lines.

Diff: 3 Section Ref: 2.4 107) How are we able to determine the chemical composition and temperature of any visible object?

Answer: When an electron moves from one energy level to another (makes a transition) in an atom of a given element, it produces a photon of light at a wavelength that is unique to that transition for that element. If this spectral line with this wavelength is observed then, we know that it must have been produced by that element. Which transitions occur are determined largely by the temperature of the gas; for instance, hydrogen shows up best at 10,000 K, while helium lines require even higher temperatures.

Diff: 3 Section Ref: 2.5 108) Compare how doubling the diameter of a mirror will affect both resolution and light gathering power.

Answer: The resolution would now be twice as sharp, but the increase in surface area, with the squaring for the area, would now detect stars four times fainter than before.

Diff: 2 Section Ref: 2.6 20 ..

109) Why must radio dishes be built so large?

Answer: Radio waves carry little energy, so a lot of them must be collected to give resolution and image quality comparable to light telescopes.

Diff: 2 Section Ref: 2.7 110) What are some advantages of radio telescopes over optical scopes?

Answer: Radio telescopes can be used day or night, they are much less affected by cloudy skies, and they open a new window to observe the Universe. They allow us to observe astronomical objects at a different wavelength than an optical telescope, thus giving an opportunity to compare and contrast the images.

Diff: 2 Section Ref: 2.7 111) How do radio interferometers greatly enhance resolution in radio wavelengths?

Answer: Hooking two or more radio dishes together with a computer lets us get resolution not equal to the diameters of the dishes, but to the separations between the scopes.

Diff: 2 Section Ref: 2.7

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 3 The Solar System 1) When a planet retrogrades, it appears to move westward.

Answer: TRUE Diff: 1 Section Ref: 3.1 2) Like the Sun and the Moon, the planets appear to move from west to east from one day to the next.

Answer: TRUE Diff: 2 Section Ref: 3.1 3) Like the Sun and the Moon, the stars appear to move from west to east from one day to the next.

Answer: TRUE Diff: 2 Section Ref: 3.1 4) The parallax shift of a star would be greater if viewed from Mars than from Earth.

Answer: TRUE Diff: 2 Section Ref: 3.2 5) Galileo's observations of the entire phase cycle of Venus proved that Ptolemy's epicycles could not be correct in keeping Venus between us and the Sun. Answer: TRUE Diff: 1 Section Ref: 3.3 6) Galileo's observations of sunspots proved the Sun was rotating, like the Earth.

Answer: TRUE Diff: 2 Section Ref: 3.3 7) Kepler found the orbits of planets are ellipses, not circles.

Answer: TRUE Diff: 1 Section Ref: 3.4 8) The orbits of most of the planets in our solar system have eccentricities close to zero.

Answer: TRUE Diff: 1 Section Ref: 3.4

1 ..

9) Kepler based his theories on the precise planetary observations of Tycho Brahe.

Answer: TRUE Diff: 1 Section Ref: 3.4 10) The eccentricity of a perfectly circular orbit is 1.

Answer: FALSE Diff: 2 Section Ref: 3.4 11) Kepler determined the shape of each planet's orbit by triangulation from different points on Earth's orbit, using observations made at many different times of the year.

Answer: TRUE Diff: 2 Section Ref: 3.4 12) Mercury, with a higher eccentricity orbit, should change its orbital speed more than do Venus or Earth.

Answer: TRUE Diff: 2 Section Ref: 3.4 13) A planet (or comet) will speed up as it approaches the Sun. Answer: TRUE Diff: 2 Section Ref: 3.4 14) Newton's Laws completely replaced the incorrect work of Kepler.

Answer: FALSE Diff: 2 Section Ref: 3.5 15) Newton's modification of Kepler's Third Law lets us measure the mass of the Sun. Answer: TRUE Diff: 2 Section Ref: 3.5 16) Newton's Law of Gravity would explain why Saturn, so far from the Sun, moves so slowly across the sky.

Answer: TRUE Diff: 2 Section Ref: 3.5 17) It the mass of a body were doubled, its gravity would become 4 times stronger.

Answer: FALSE Diff: 2 Section Ref: 3.5 2 ..

18) According to Newton's second law, if you double the force acting on a body, the acceleration will double.

Answer: TRUE Diff: 2 Section Ref: 3.5 19) Transits of Venus were critical in early determinations of the AU. Answer: TRUE Diff: 2 Section Ref: 3.6 20) All the jovian planets lie beyond the asteroid belt.

Answer: TRUE Diff: 2 Section Ref: 3.7 21) Of all the terrestrial planets, Mercury's orbit is most eccentric and tilted most above the ecliptic.

Answer: TRUE Diff: 2 Section Ref: 3.7 22) All the terrestrial planets lie inside the asteroid belt.

Answer: TRUE Diff: 1 Section Ref: 3.7 23) Due to their great masses, all four jovian worlds are much denser than the Earth.

Answer: FALSE Diff: 2 Section Ref: 3.7 24) The most accurate Greek attempt to explain planetary motion was the model of A) Aristotle.

B) Pythagoras.

C) Hipparchus.

D) Ptolemy.

E) Erastothenes.

Answer: D Diff: 1 Section Ref: 3.1

3 ..

25) The Ptolemaic model of the universe A) explained and predicted the motions of the planets with deferents and epicycles.

B) is the basis of our modern cosmology.

C) could not account for the stellar parallax observed by Hipparchus.

D) describes the orbits of the planets as being ellipses, not circles.

E) always kept Mars and Mercury between the Earth and Sun. Answer: A Diff: 2 Section Ref: 3.1 26) Scientists today do not accept the Ptolemaic model because A) it is ancient history.

B) it was too complicated, compared to Copernicus' heliocentric model.

C) it has been shown that Ptolemy faked his data.

D) it had no explanation for retrograde motion.

Answer: B Diff: 1 Section Ref: 3.2 27) To fully describe the apparent motion of the planets in the sky, Ptolemy's model invoked A) ellipses.

B) constant speeds.

C) a heliocentric view.

D) epicycles.

E) Occam's Razor.

Answer: D Diff: 2 Section Ref: 3.1 28) Occam's Razor A) divides the inner planets from the outer planets.

B) tells scientists to use the simplest model, all other things being equal.

C) is the term that describes how thin the rings of the Jovian planets are.

D) describes how a planet's orbital period and distance from the Sun are related.

E) is the tool that Copernicus used to shave.

Answer: B Diff: 1 Section Ref: 3.1

4 ..

29) Which of the following describes parallax?

A) It is best measured over exactly one year intervals.

B) It is inversely proportional to the distance to the star.

C) It was first observed by Galileo with his new telescope.

D) It is only applicable to objects within the solar system.

E) It is more accurate as the distances to objects becomes greater.

Answer: B Diff: 3 Section Ref: 3.2 30) A star with a large parallax A) is at a great distance from Earth.

B) is moving at a great speed with respect to Earth.

C) is at a short distance from Earth.

D) is moving at a slow speed with respect to Earth.

E) is not moving with respect to Earth.

Answer: C Diff: 3 Section Ref: 3.2 31) Scientists today do not accept the Ptolemaic model because A) it is ancient history.

B) it was too complicated, compared to Copernicus' heliocentric model.

C) it has been shown that Ptolemy faked his data.

D) it had no explanation for retrograde motion.

E) the work of Tycho and Kepler showed the heliocentric model was more accurate.

Answer: E Diff: 1 Section Ref: 3.2 32) On which of these assumptions do Ptolemy and Copernicus agree?

A) The Earth must be the center of all motion in the Cosmos.

B) All orbits must be perfect circles.

C) The Sun was bigger than the Earth.

D) Venus must always stay between us and the Sun. E) The Sun must orbit us, but the planets do orbit the Sun. Answer: B Diff: 1 Section Ref: 3.2

5 ..

33) The heliocentric model was actually first proposed by A) Aristotle.

B) Archimedes.

C) Aristarchus.

D) Alexander the Great.

E) Hipparchus.

Answer: C Diff: 2 Section Ref: 3.2 34) According to Copernicus, the retrograde motion for Mars must occur A) at inferior conjunction, when Mars laps the Earth and passes between us and the Sun. B) at superior conjunction, when Mars lies on the far side of the Sun. C) at quadrature, when Mars lies exactly 90 degrees east or west of the Sun. D) at greatest elongation, when Mars can get up to 47 degrees from the Sun. E) at opposition, when the Earth overtakes Mars and passes between Mars and the Sun. Answer: E Diff: 2 Section Ref: 3.2 35) Which of the statements below is part of both the Ptolemaic and Copernican models?

A) The Earth orbits the Sun once a year.

B) The Sun lies in the center of the Cosmos.

C) The Moon orbits the Earth once a month.

D) Epicycles are needed to explain retrograde motion of the planets.

E) Venus' epicycle must always lie between us and the Sun. Answer: C Diff: 3 Section Ref: 3.2 36) Which of these was NOT seen telescopically by Galileo?

A) Sunspots B) Venus' phase cycle C) Four moons around Jupiter D) Stellar parallax E) Craters and mare on the Moon Answer: D Diff: 1 Section Ref: 3.3

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37) Which of the following was NOT a contribution of Galileo to astronomy?

A) Sunspots showed the Sun was rotating on its axis, like the Earth does.

B) The four moons of Jupiter are a model for the solar system motions in general.

C) The phases of Venus prove it orbits completely around the Sun. D) The changing appearance of Saturn's rings corresponds to our seasons.

E) The craters and mountains of the Moon prove it a world in its own right.

Answer: D Diff: 2 Section Ref: 3.3 38) Which of the following is a contribution to astronomy made by Galileo?

A) The astronomical telescope can show us far more detail than the eye can.

B) Jupiter has four moons orbiting it.

C) The Moon has craters, mountain, valleys, and dark flat areas on its surface.

D) Venus appears almost fully lit when it lies on the far side of the Sun. E) all of the above Answer: E Diff: 2 Section Ref: 3.3 39) Which of these observations of Galileo refuted Ptolemy's epicycles?

A) The complete cycle of Venus' phases B) The rotation of sunspots across the Sun's surface C) The revolution of Jupiter's moons around it D) The craters on the Moon E) The visibility of many more stars with the telescope Answer: A Diff: 2 Section Ref: 3.3 40) A fatal flaw with Ptolemy's model is its inability to predict the observed phases of A) the Sun during an eclipse.

B) the Moon in its monthly cycle.

C) Mercury and Venus.

D) Mars and Jupiter.

E) Jupiter and Saturn.

Answer: C Diff: 2 Section Ref: 3.3

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41) It took two centuries for the Copernican model to replaced the Ptolemaic model because A) in Copernicus' time, there were no telescopes.

B) the Church wouldn't let anyone talk about Copernicus' model for 200 years.

C) there was no scientific evidence to support either model until Galileo made his observations.

D) the Ptolemaic model was simpler and more aesthetically pleasing.

E) the Copernican model required complicated new terms to explain it correctly.

Answer: C Diff: 3 Section Ref: 3.3 42) Galileo found the rotation period of the Sun was approximately A) a day.

B) a week.

C) a month.

D) three months.

E) a year.

Answer: C Diff: 3 Section Ref: 3.3 43) Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as A) elliptical, not circular.

B) much larger than Copernicus had envisioned.

C) around the Sun, not the Earth.

D) being on equants instead of epicycles.

E) complex, with epicycles to account for retrograde motions.

Answer: A Diff: 1 Section Ref: 3.4 44) Tycho Brahe's contribution to Kepler's Laws of Planetary Motion were A) his detailed and accurate observations of the planet's position.

B) his observations of Jupiter's moons.

C) a mathematical explanation of epicycles.

D) a precise lunar calendar.

E) the correct explanation of lunar phases.

Answer: A Diff: 1 Section Ref: 3.4

8 ..

45) A circular orbit would have an eccentricity of A) 0.

B) between 0 and 0.5.

C) between 0.5 and 1.

D) exactly 1.0.

E) infinity.

Answer: A Diff: 1 Section Ref: 3.4 46) Upon which point do Copernicus and Kepler disagree?

A) The Moon orbits the Earth.

B) The Earth orbits the Sun. C) Retrograde motion occurs when one planet overtakes another.

D) The orbits of the planets are ellipses, with one focus at the Sun. E) Venus will appear as a crescent when she retrogrades between us and the Sun. Answer: D Diff: 2 Section Ref: 3.4 47) The planet's orbital period is A) the time it takes it to rotate and have the same face toward us again.

B) the time it takes to return to the same location in the sky, relative to the Sun. C) the time it takes for a satellite to orbit it.

D) the time it takes for it to retrograde back to the same position as we pass it.

E) the time its magnetic field takes to spin once.

Answer: B Diff: 1 Section Ref: 3.4 48) What contribution to astronomy was made by Tycho Brahe?

A) The planets' orbits around the Sun are ellipses, not circles.

B) The Earth is not the center of the Universe.

C) His observations of planetary motion with great accuracy proved circular orbits could not work.

D) His telescope revealed the moons of Jupiter before Galileo noted them.

E) Retrograde motion must be explained by epicycles larger than those of Ptolemy.

Answer: C Diff: 2 Section Ref: 3.4

9 ..

49) Which concept was NOT a part of Kepler's Laws of Planetary Motion?

A) All planetary orbits are ellipses.

B) The square of the planet's period is equal to the cube of its average distance.

C) A planet must move fastest in its orbit at perihelion.

D) Epicycles are needed to explain the varying brightnesses of the planets.

Answer: D Diff: 2 Section Ref: 3.4 50) According to Kepler's third law, the square of the planet's period in years is A) equal to its perihelion distance from the Sun in AU. B) inversely proportional to its mass in kilograms.

C) equal to the fourth power of its average temperature in degrees Kelvin.

D) proportional to the cube of its semimajor axis in AU. E) equal to the square of its aphelion distance in AU. Answer: D Diff: 2 Section Ref: 3.4 51) What does Kepler's third law imply about planetary motion?

A) All planets orbit the Sun at the same speed.

B) Planets closer to the Sun orbit at a slower speed than planets further from the Sun. C) Planets further from the Sun orbit at a slower speed than planets closer to the Sun. D) Planets further from the Sun orbit at a faster speed than planets closer to the Sun. E) This law implies nothing about a planet's motion.

Answer: C Diff: 3 Section Ref: 3.4 52) A planet whose distance from the Sun is 3 AU would have an orbital period of how many Earth-years?

A) 3 B) C) D) 9 E) 81 Answer: B Diff: 3 Section Ref: 3.4

10 ..

53) The force of gravity varies with the A) product of the two masses.

B) inverse of the distance separating the two bodies.

C) inverse square of the distance separating the two bodies.

D) Both A and B are correct.

E) Both A and C are correct.

Answer: E Diff: 1 Section Ref: 3.5 54) The Law of Universal Gravitation was developed by A) Kepler.

B) Galileo.

C) Newton.

D) Copernicus.

E) Einstein.

Answer: C Diff: 1 Section Ref: 3.5 55) The force of gravity between two objects A) increases with the masses of the bodies, but decreases with their separations.

B) increases with the masses of the bodies, but decreases with the square of the distances between them.

C) increases with the square of their masses, but decreases with the cube of their periods of orbit about the Sun. D) depends on the density, not the mass of the bodies.

E) depends on the temperature, density, and size of the bodies.

Answer: B Diff: 1 Section Ref: 3.5 56) According to Newton's Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would A) increase by a factor of 3.

B) decrease by a factor of 3.

C) increase by a factor of 9.

D) decrease by a factor of 9.

E) stay the same.

Answer: D Diff: 2 Section Ref: 3.5

11 ..

57) How much stronger is the gravitational pull of the Sun on Earth, at 1 AU, than it is on Saturn at 10 AU? A) 5X B) 10X C) 25X D) 100X E) 250X Answer: D Diff: 2 Section Ref: 3.5 58) Which of these was a contribution of Newton to astronomy?

A) Artificial satellites could be put into orbit about the Earth.

B) The Sun's gravity is greatest on a planet at perihelion, so the planet must speed up.

C) The Moon pulls as strongly on us as we do on it.

D) His differential calculus lets us calculate planetary motions more accurately.

E) All of these were due to Newton's work.

Answer: E Diff: 2 Section Ref: 3.5 59) Jupiter lies about 5 AU from the Sun, so at its distance A) the Sun's gravity is just as strong as it is here at Earth.

B) the Sun's gravity must be five times stronger to hold massive Jupiter in orbit.

C) the Sun's gravity is five times weaker there than at one AU distance.

D) the Sun's gravity is 25 times weaker than its pull on the Earth.

E) the Sun's gravity is so weak that ultimately Jupiter will escape the solar system.

Answer: D Diff: 2 Section Ref: 3.5 60) Given that the planet orbiting the nearby star 51 Pegasi is about 20X larger than the Earth, but 400X more massive, on that world you would weigh A) the same as you do here.

B) twice as much as you do here.

C) half as much as you do here.

D) 20X more that you do here.

E) 400X more than you do here.

Answer: A Diff: 3 Section Ref: 3.5

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61) How does Newton's Universal Law of Gravitation explain Kepler's laws?

A) Universal gravitation implies that the orbits of the planets must be elliptical (Kepler's first law).

B) Universal gravitation implies that the planets will sweep out equal areas in equal times (Kepler's second law).

C) Universal gravitation implies that the planets further from the Sun will move more slowly than the planets closer to the Sun (Kepler's third law).

D) Universal gravitation implies that when a planet is closer to the Sun in its orbit, it will move faster than when it is farther from the Sun (Kepler's second law).

E) Both C and D are correct.

Answer: E Diff: 3 Section Ref: 3.6 62) During the eighteenth and nineteenth centuries, attempts to precisely measure the astronomical unit relied largely on rare A) total solar eclipses.

B) transits of the inferior planets across the Sun. C) passages of comets close to the Earth.

D) maximum elongations of Venus.

E) oppositions of Mars.

Answer: B Diff: 2 Section Ref: 3.6 63) Today we rely largely on what technique to precisely measure distances in the solar system?

A) Transits of Venus across the Sun B) Radar echo timings C) Measurement of stellar parallaxes.

D) Timings of the eclipses of its moons by Jupiter's shadow E) Precise measurements of length of the year with atomic clocks Answer: B Diff: 2 Section Ref: 3.6 64) What is TRUE about solar system densities?

A) The denser planets lie closer to the Sun. B) In differentiated bodies, the denser materials lie near their surfaces.

C) The asteroids all have about the same density.

D) Saturn has the same density as water.

E) Planetary density increases with increasing distance from the Sun. Answer: A Diff: 2 Section Ref: 3.7

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65) Masses of the planets are easiest to determine if A) they are terrestrial and the extra size of the planet's disk can be measured.

B) they are jovian and their oblateness can be found.

C) they have natural satellites whose motions can be precisely measured.

D) they are dense and easily deflect the path of passing spacecraft.

E) they move rapidly and their periods are easily measured.

Answer: C Diff: 2 Section Ref: 3.7 66) The average density of each planet in the solar system is determined by taking its mass and dividing that by its A) radius.

B) diameter.

C) surface area.

D) radius squared.

E) volume.

Answer: E Diff: 2 Section Ref: 3.7 67) In order to determine the mass of a planet by applying Newton's laws of motion and gravity, the planet must have A) rings.

B) moons.

C) a solid surface.

D) a known size and distance from Earth.

E) planets further from the Sun than itself.

Answer: B Diff: 2 Section Ref: 3.7 68) The plane in which almost all planets orbit the Sun is called the A) equator of the solar system.

B) ecliptic.

C) equant.

D) node.

E) galactic plane.

Answer: B Diff: 1 Section Ref: 3.7

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69) Which statement about the motion of the planets is INCORRECT? A) Most orbit above the Sun's equator.

B) All revolutions of major planets are counterclockwise.

C) The orbits of most planets are almost circular, with low eccentricities.

D) Most planets move in the Earth's equatorial plane.

E) Most planets rotate in the counterclockwise direction when viewed from the North.

Answer: D Diff: 2 Section Ref: 3.7 70) Mercury's most unusual orbital feature, as compared to the other planets, is A) the size of its orbit.

B) the shape of its orbit.

C) its orbital period.

D) the size of the planet.

E) that it has no moons.

Answer: B Diff: 2 Section Ref: 3.7 71) What aspects of the planets orbits are nearly the same for most planets?

A) Orbital period and shape B) Shape and tilt from the ecliptic C) Shape and distance from the Sun D) Orbital period and distance from the Sun E) Tilt from the ecliptic and distance from the Sun Answer: B Diff: 2 Section Ref: 3.7 72) Planetary orbits A) are evenly spaced throughout the solar system.

B) are highly inclined to the ecliptic.

C) are almost circular, with low eccentricities.

D) have the Sun at their exact center.

E) are spaced more closely together as they get further from the Sun. Answer: C Diff: 2 Section Ref: 3.7

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73) How do the densities of the jovian and terrestrial planets compare?

A) Made from the same solar nebula, they are all similar.

B) More massive jovians all have high densities, compared to the tiny terrestrials.

C) All terrestrials are more dense than any of the jovians.

D) The closer a planet lies to the Sun, the less its density.

E) No real pattern here; densities vary greatly and are very individual to each world.

Answer: C Diff: 1 Section Ref: 3.7 74) Which of the following are the jovian planets?

A) Jupiter, Saturn, Uranus, Neptune, and Pluto B) Only Jupiter C) Only Jupiter and Saturn D) Jupiter, Saturn, Uranus, and Neptune only E) Everything past Mars and the asteroid belt Answer: D Diff: 1 Section Ref: 3.7 75) Because he failed to observe stellar ________, Aristotle wrongly concluded we could not be in orbit around the Sun. Answer: parallax Diff: 1 Section Ref: 3.1 76) To explain retrograde motion as well as changes in planetary brightness, Ptolemy's model used ________.

Answer: epicycles Diff: 2 Section Ref: 3.1 77) Galileo's discovery of four moons orbiting ________ provided new support for the ideas of Copernicus.

Answer: Jupiter Diff: 2 Section Ref: 3.3 78) Galileo's observations of the phases of ________ could not be explained by Ptolemy's epicyclic model.

Answer: Venus Diff: 1 Section Ref: 3.3

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79) Planets do not move on a straight line. According to Newton's First Law of Motion, that means that there must be an outside ________ acting on them.

Answer: force Diff: 1 Section Ref: 3.5 80) According to Newton's second law, when the same force acts on two bodies, the body with the larger mass will have the ________ acceleration.

Answer: smaller Diff: 1 Section Ref: 3.5 81) According to Newton, the gravity of the ________ is needed to explain planetary orbits.

Answer: Sun Diff: 1 Section Ref: 3.6 82) Newton's modification of Kepler's Laws allows us to find the ________ of the planets, if we can observe satellites in orbit about them.

Answer: masses Diff: 2 Section Ref: 3.6 83) In the eighteenth and nineteenth centuries, the rare transits of ________ were critical in determining the astronomical unit's length.

Answer: Venus Diff: 2 Section Ref: 3.6 84) In terms of ________, all the terrestrials are greater than any of the jovians.

Answer: density Diff: 1 Section Ref: 3.7 85) How did Ptolemy explain the retrograde motion of Mars?

Answer: Mars will retrograde on the inner portion of its epicycle, when it is closest to us and its motion on the epicycle is more obvious than its motion along its deferent.

Diff: 3 Section Ref: 3.1 86) Explain Occam's Razor.

Answer: Occam's Razor is the principle that says when two theories make the same predictions and explain the facts equally well, then the simpler one is better.

Diff: 2 Section Ref: 3.1

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87) Explain how Copernicus would account for the retrograde loops of superior planets.

Answer: The Earth moves faster than these outer worlds, so at opposition we overtake them and as we sweep past them, they appear to retreat westward for a few weeks.

Diff: 2 Section Ref: 3.2 88) Why was stellar parallax not measured until the 19th century?

Answer: Stars are so far away that even the closest stars have parallax less than an arcsecond, which could not be measured without the technological developments that did not occur until the 19th century.

Diff: 2 Section Ref: 3.2 89) What did Galileo discover about Jupiter that supported Copernicus?

Answer: Its four moons were a model solar system, orbiting a larger central body just as the smaller planets orbit the Sun. Diff: 2 Section Ref: 3.3 90) What did Galileo discover when looking at the Sun with his telescope, and how did this support Copernicus?

Answer: Sunspots, which rotated across the Sun's face, showing that the Sun was not perfect and it (and Earth) could rotate on its axis.

Diff: 3 Section Ref: 3.3 91) We are at ________ in January, when we are closest to the Sun in our elliptical orbit.

Answer: perihelion Diff: 1 Section Ref: 3.4 92) While both Ptolemy and Copernicus assumed all orbits were ________, Kepler's first law corrected this and made planetary motion predictable.

Answer: circles Diff: 1 Section Ref: 3.4 93) While the orbits of planets are nearly circular, the eccentricities of the orbits of ________ are near one.

Answer: comets Diff: 2 Section Ref: 3.4

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94) Of all his laws, Kepler was proudest of the third. Why was it so appealing in his search for cosmic harmony?

Answer: He found a simple math relation that directly connected the periods of revolution of each planet to its average distance from the Sun, so that P2 = D3.

Diff: 3 Section Ref: 3.4 95) Explain how the eccentricity describes the shape of an ellipse.

Answer: The higher the eccentricity, the more elongated the oval; a circle has an eccentricity of zero, while very stretched out comet orbits approach an eccentricity of one.

Diff: 3 Section Ref: 3.4 96) Using Newton's first law, describe the motion of a body is moving in the absence of any net external force.

Answer: in a straight line at constant speed forever Diff: 2 Section Ref: 3.5 97) Why do Newton's Laws show a force must be acting on the planets?

Answer: The planets are moving in elliptical orbits (not a straight line). According to First Law, if no force acts on the body, it must move in a straight line. Since the planets do not, there must be a force acting on them.

Diff: 3 Section Ref: 3.5 98) What is meant by the Astronomical Unit?

Answer: The Astronomical unit, or AU, is the mean distance between the Earth and Sun. Diff: 2 Section Ref: 3.6 99) Contrast the densities of the terrestrial and Jovian planets.

Answer: Forming close to the Sun, terrestrials are denser, with iron and silicates as major components. Far out beyond the ice limit, the jovians are far less dense, with compositions much like the gases of the Sun. Diff: 1 Section Ref: 3.7 100) How would Ptolemy explain the rising of the Sun? Contrast this to Copernicus' explanation of the same event.

Answer: Ptolemy would say that the celestial sphere rotated westward, carrying the Sun over our eastern horizon. Copernicus said that we, the Earth, rotate eastward once a day, and we turn to see the Sun on our eastern horizon at sunrise.

Diff: 3 Section Ref: 3.2

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101) Of the Ptolemaic and Copernican models, who wins the battle of Occam's Razor for the simplest explanation of retrograde motions?

Answer: Copernicus simply had retrograde motion resulting from the different speeds of the planets, with retrograding occurring any time one planet overtook another. Ptolemy by contrast needed complex deferents, epicycles, and equants to handle the complex planetary motions.

Diff: 3 Section Ref: 3.2 102) How did Galileo's observations of Venus disprove the Ptolemaic model?

Answer: Ptolemy said that the epicycles for both Venus and Mercury were centered on the Earth-Sun line, so they must always lie between us and the Sun, so would always appear as crescents in the telescope. Galileo found Venus went through the entire phase cycle, proving that she revolved completely around the Sun, as predicted by Copernicus in his heliocentric model.

Diff: 2 Section Ref: 3.3 103) How does Kepler's First Law refine the Copernican model greatly?

Answer: Copernicus, like the Greeks, thought all orbits were circular. But when Kepler used elliptical orbits, particularly with Mars and Mercury, the theory fit the actual observations of planetary motion much better than did the old Ptolemaic one.

Diff: 2 Section Ref: 3.4 104) Relate Kepler's Second Law to the speeds of the planets.

Answer: In equal time intervals, the lines that connect each of the planets to the Sun must all sweep out equal areas. The longer this line, the slower the planet could move and still sweep out this constant area. Thus more distant planets orbit the Sun slower, and each planet will speed up at perihelion and slow down at aphelion.

Diff: 3 Section Ref: 3.4 105) According to Newton's third law, the Voyager probes pulled just as hard on Jupiter as it did on them when they flew past it. Why were they accelerated enough to leave the solar system but Jupiter still is in orbit about the Sun? Answer: Jupiter was much more massive than the Voyagers, so by the second law, they slowed Jupiter down a tiny bit, but it accelerated the probes so much they escaped the gravity of the Sun itself.

Diff: 3 Section Ref: 3.5 106) How can astronomers determine the mass of the Sun? Answer: Using Newton's Laws, we know that gravity keeps the Earth in orbit around the Sun. Since the Earth's path is nearly circular, we can determine the size of the force keeping it on this path. Combining this equation (for centripetal force) with the gravity equation allows astronomers to calculate the Sun's mass.

Diff: 3 Section Ref: 3.6 20 ..

107) How is density determined, and how do the densities of the terrestrial and jovian worlds relate to their distances from the Sun? Answer: Density is mass per unit volume; all terrestrials have been heated by the Sun enough to drive away lighter gases, so they are rocky worlds with densities between 3-6 g/cc, while all jovians formed far enough out to be made of lighter hydrogen and helium, and have densities much less than any of the inner worlds.

Diff: 2 Section Ref: 3.7 108) Name several characteristics the orbits of the eight planets share.

Answer: All orbit in almost circular orbits of low eccentricity, close to the ecliptic plane and in the Sun's equatorial plane, and all revolve counterclockwise around the Sun; most also rotate counterclockwise as well, and most moons orbit their planets in the same counterclockwise directions the original solar nebula had.

Diff: 3 Section Ref: 3.7 109) What physical characteristics of Mercury distinguish it among all the planets in our solar system?

Answer: Mercury has the most eccentric orbit of any of the planets. Mercury's orbital plane has the highest inclination to the ecliptic. Mercury is the smallest body considered a planet in the solar system.

Diff: 2 Section Ref: 3.7

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 4 Earth and Its Moon 1) The hydrosphere covers about 50% of the Earth's crust.

Answer: FALSE Diff: 1 Section Ref: 4.1 2) The average density of the Moon is less than that of the Earth.

Answer: TRUE Diff: 1 Section Ref: 4.1 3) The Moon's crust is thicker on the side of the Moon that faces the Earth.

Answer: FALSE Diff: 1 Section Ref: 4.1 4) The Sun's effect on tides is greater than the Moon's because of its greater mass.

Answer: FALSE Diff: 1 Section Ref: 4.2 5) When the Moon is described as tidally locked, that means that it does not rotate.

Answer: FALSE Diff: 2 Section Ref: 4.2 6) Seismic S-waves can travel through Earth's liquid outer core.

Answer: FALSE Diff: 2 Section Ref: 4.3 7) Seismic P-waves can travel through both solid and liquid materials.

Answer: TRUE Diff: 2 Section Ref: 4.3 8) The most important factor contributing to the differences in the internal structure of the Moon and Earth is size.

Answer: TRUE Diff: 1 Section Ref: 4.3

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9) Without greenhouse gases in our atmosphere, the Earth's oceans would not be liquid.

Answer: TRUE Diff: 1 Section Ref: 4.4 10) The continuing rise in the carbon dioxide in our atmosphere should cause our surface temperatures to rise.

Answer: TRUE Diff: 1 Section Ref: 4.4 11) The ozone layer lies in the mesosphere.

Answer: FALSE Diff: 2 Section Ref: 4.4 12) The three most abundant gases in our atmosphere are nitrogen, oxygen, and argon.

Answer: TRUE Diff: 2 Section Ref: 4.4 13) Almost all the oxygen in Earth's atmosphere is unique among the planets in our solar system.

Answer: TRUE Diff: 2 Section Ref: 4.4 14) Infrared radiation is trapped close to our surface by the greenhouse effect.

Answer: TRUE Diff: 2 Section Ref: 4.4 15) The most abundant gas in Earth's atmosphere is oxygen.

Answer: FALSE Diff: 2 Section Ref: 4.4 16) In the past, most of the landmass on Earth was concentrated in a single, large continent.

Answer: TRUE Diff: 1 Section Ref: 4.5 17) When tectonic plates collide, they fuse together and come to rest.

Answer: FALSE Diff: 2 Section Ref: 4.5

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18) Few of the Moon's craters are actually due to volcanism, as was widely thought prior to Apollo.

Answer: TRUE Diff: 1 Section Ref: 4.6 19) The crust of the Earth is covered by about ________ water in the hydrosphere.

A) 50% B) 60% C) 70% D) 80% E) 90% Answer: C Diff: 1 Section Ref: 4.1 20) Compared to the density of water, our Earth averages about A) the same density, similar to Saturn.

B) 3 times denser, much like our Moon.

C) 4 times denser, similar to Mars.

D) 5 times denser, like the Mercury and Venus.

E) 10 times denser, due to our core of iron and nickel.

Answer: D Diff: 2 Section Ref: 4.1 21) What can we conclude about the structure of Earth's interior knowing that the average density of Earth is higher than the average density of the rock on the continents and seafloor?

A) That Earth's most dense material must be water B) That Earth's most dense material must be the seafloor and the continents C) That Earth's most dense material must be beneath the surface D) That Earth's least dense material must be the seafloor and the continents E) That Earth's least dense material must be beneath the surface Answer: C Diff: 2 Section Ref: 4.1 22) From the center outward, the correct order is A) liquid iron inner core, solid nickel outer core, rocky mantle, silicate crust.

B) solid metallic inner core, molten metal outer core, silicate mantle and crust.

C) solid metal core, molten metal hydrosphere, rocky lithosphere, gases in atmosphere.

D) solid rock core, liquid metal mantle, solid rock crust.

E) molten metal hydrosphere, molten rock lithosphere, solid silicate crust.

Answer: B Diff: 2 Section Ref: 4.1 3 ..

23) The relative size of the mantle of Earth compared to the solid inner core of Earth is most similar to A) the peel of an orange as compared to the meat of the orange.

B) the rind of a watermelon as compared to the meat of the watermelon.

C) the skin of a grape as compared to the meat of the grape.

D) the meat of a peach as compared to the pit of the peach.

E) the meat of a cherry as compared to the pit of the cherry.

Answer: E Diff: 2 Section Ref: 4.1 24) The Moon's density, when compared to Earth's, is about A) 10% as large.

B) 25% as large.

C) 50% as large.

D) 60% as large.

E) the same.

Answer: D Diff: 2 Section Ref: 4.1 25) What is the best description of the Earth's rotation over its entire history?

A) It has periodically reversed directions, as the magnetic polarity reversals show.

B) It has been constant over the entire history of the solar system.

C) It undergoes abrupt changes, as the magnetic variations show.

D) It has slowed down very gradually at about .0015 seconds per century.

E) It has sped up at about .013 seconds per century.

Answer: D Diff: 1 Section Ref: 4.2 26) Where does the energy come from to create tidal bulges?

A) The Sun's gravity B) The orbital and rotational motion of the Earth and Moon C) The heat from Earth's core D) The movement of the Earth's oceans.

E) The temperature difference between the Moon's surface and its core Answer: B Diff: 2 Section Ref: 4.2

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27) Which body has the greatest gravitational pull on Earth?

A) The Sun B) The Moon C) Mars D) Jupiter E) None has an impact, as all are too distant.

Answer: A Diff: 1 Section Ref: 4.2 28) At what phase are the tides least noticeable?

A) New Moon B) Full Moon C) Third quarter D) Waxing crescent E) Waning gibbous Answer: C Diff: 2 Section Ref: 4.2 29) What is TRUE of spring tides?

A) The third quarter Moon would be high overhead at dawn.

B) The difference between low and high tides would be greatest.

C) There would be one high and one low tide each day.

D) The Moon's phase will be first quarter.

E) The difference between low and high tides would be smallest.

Answer: B Diff: 2 Section Ref: 4.2 30) At what phase would tidal variation be the least during the entire day?

A) New Moon B) First quarter C) Waxing gibbous D) Full Moon E) Waning crescent Answer: B Diff: 2 Section Ref: 4.2

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31) We determine the structure of the Earth's core using A) deep mine shafts.

B) satellite imaging.

C) radar and sonar.

D) seismic wave data.

E) magnetic resonance imaging.

Answer: D Diff: 1 Section Ref: 4.3 32) Seismic waves are most useful for mapping A) the surface of Venus with Magellan.

B) the surface of Mars with Global Surveyor.

C) the Earth's core and mantle.

D) the density of the hydrosphere.

E) the depths of the oceans.

Answer: C Diff: 1 Section Ref: 4.3 33) Like other solid bodies in the solar system, Earth's surface was kept molten by A) radioactivity.

B) differentiation.

C) convection.

D) bombardment by small bodies.

E) the solar nebula.

Answer: D Diff: 2 Section Ref: 4.3 34) In noting that our world is "differentiated," we mean that A) the density of its materials decreases as you go downward toward the core.

B) the Earth has evolved in a different pattern than any other planet.

C) the iron and nickel core is denser than the silicate mantle and crust.

D) radioactive heating in the core is at a slower pace than when the Earth was new.

E) the Earth's magnetic field is different now in polarity than it was 700,000 years ago.

Answer: C Diff: 2 Section Ref: 4.3

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35) Which statement about seismic waves is TRUE? A) Only S waves can travel through liquid.

B) P waves travel faster, and thus arrive sooner than do the S waves.

C) In the shadow zones, neither type is observed.

D) S waves can travel though the outer core, but P waves cannot.

E) On the far side of the Earth, only the S waves on the surface can be detected.

Answer: B Diff: 3 Section Ref: 4.3 36) Which statement about seismic waves is FALSE? A) Both S and P waves can be detected by seismographs.

B) Close to the epicenter, both S and P waves can be recorded.

C) P waves travel faster, so the gap between their arrival times gives the source's distance.

D) Only P waves can be detected in the shadow zone.

E) S waves are blocked by the fluid outer core and cannot be observed on the other side of the planet from the epicenter.

Answer: D Diff: 3 Section Ref: 4.3 37) Moonquakes on the Moon were detected by A) the radar observations over time from Earth.

B) the seismographs left these by the Apollo astronauts.

C) laser beams reflected off mirrors left on the Moon by Apollo missions.

D) seismographs attached to the Russian Lunar rovers.

E) telescopic observations of lunar landslides.

Answer: B Diff: 2 Section Ref: 4.3 38) Moonquakes release about as much energy as A) a moderate earthquake.

B) a nuclear fission bomb.

C) the eruption of Mt. St. Helens in 1980.

D) a firecracker.

E) nothing. There are no moonquakes since the Moon is geologically dead.

Answer: D Diff: 2 Section Ref: 4.3

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39) Scientists are confident that the Moon does not have a large, dense nickel-iron core because A) the Moon's surface rocks are similar in density to the Moon's average density.

B) deep samples taken by the Apollo astronauts found almost no iron.

C) the Earth's magnetic field would pull anything with a lot of iron into the Earth.

D) unmanned Soviet missions drilled into the Moon's core and did not find iron.

E) a thick atmosphere is required for there to be a metal core.

Answer: A Diff: 1 Section Ref: 4.3 40) Without the greenhouse effect operating in our atmosphere A) We would not have to worry about any warming problems in the future.

B) Earth would have an average temperature of -23 degrees Celsius.

C) The ice in the polar regions would have melted long ago.

D) The ozone layer would not be weakening.

E) The Earth would have become much more like Venus long ago.

Answer: B Diff: 1 Section Ref: 4.4 41) How is the existence of Earth's unique atmosphere explained?

A) The oxygen in Earth's atmosphere is a result of early life on Earth.

B) Volcanic gases containing nitrogen were outgassed from Earth's interior.

C) As Earth cooled, water vapor fell out of the atmosphere to form the oceans.

D) Ultraviolet radiation from the Sun freed the hydrogen, allowing it to escape.

E) When Earth formed, its atmosphere formed from the gases most common in the early solar system.

Answer: A Diff: 1 Section Ref: 4.4 42) What gas is the primary constituent of our atmosphere?

A) Oxygen B) Carbon dioxide C) Nitrogen D) Hydrogen E) Helium Answer: C Diff: 1 Section Ref: 4.4

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43) Which major atmospheric component is chiefly a product of life processes?

A) Carbon dioxide B) Water C) Oxygen D) Hydrogen sulfide E) Nitrogen Answer: C Diff: 1 Section Ref: 4.4 44) The critical part of the atmosphere for protecting life on the ground from excessive ultraviolet radiation is the A) hydrosphere.

B) troposphere.

C) ozone layer.

D) stratosphere.

E) ionosphere.

Answer: C Diff: 1 Section Ref: 4.4 45) In what part of our atmosphere do we live?

A) Troposphere B) Stratosphere C) Mesosphere D) Ionosphere E) Exosphere Answer: A Diff: 1 Section Ref: 4.4 46) What is the process that physically transfers heat from a lower (hotter) to a higher (cooler) level?

A) Radiation B) Translation C) Convection D) Reflection E) Conduction Answer: C Diff: 2 Section Ref: 4.4

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47) Above about 80 km, the Sun's radiation ionizes the gases. What is this part of Earth's atmosphere called?

A) The troposphere B) The stratosphere C) The mesosphere D) The ionosphere E) The magnetosphere Answer: D Diff: 2 Section Ref: 4.4 48) The principal greenhouse gases in our present atmosphere are A) hydrogen and helium.

B) hydrogen sulfide and carbon disulfide.

C) water vapor and carbon dioxide.

D) methane and ammonia.

E) sulfuric acid vapor and carbon dioxide.

Answer: C Diff: 2 Section Ref: 4.4 49) Almost all of our atmospheric gases lie in the A) ionosphere.

B) stratosphere.

C) troposphere.

D) ozone layer.

E) mesosphere.

Answer: C Diff: 2 Section Ref: 4.4 50) The Greenhouse Effect works by trapping A) incoming ultraviolet radiation from the Sun. B) outgoing ultraviolet radiation from the Earth.

C) incoming infrared radiation from the Sun. D) outgoing infrared radiation from the Earth.

E) the heat from the Sun in Earth's atmosphere.

Answer: D Diff: 2 Section Ref: 4.4

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51) What is the percentage of Earth's atmosphere (by volume) that is carbon dioxide (CO2)?

A) 78 B) 21 C) 3 D) 0.9 E) 0.03 Answer: E Diff: 2 Section Ref: 4.4 52) Within Earth's atmosphere the ozone layer is located A) in the troposphere.

B) between the troposphere and the stratosphere.

C) in the stratosphere.

D) between the stratosphere and the mesosphere.

E) in the mesosphere.

Answer: C Diff: 2 Section Ref: 4.4 53) Within Earth's atmosphere, in which layer does convection occur?

A) The troposphere B) The stratosphere C) The mesosphere D) The ionosphere E) Convection occurs in all layers of Earth's atmosphere.

Answer: A Diff: 2 Section Ref: 4.4 54) When two tectonic plates collide A) they both stop moving.

B) they always produce high mountain chains like the Himalayas.

C) volcanoes always mark the boundary between them.

D) they continue moving, producing a variety of large deformations.

E) that region is safe from earthquakes now the plates are fixed.

Answer: D Diff: 1 Section Ref: 4.5

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55) Which of these is not a product of plate tectonics and hot spots?

A) Hawaii B) Yellowstone and Old Faithful C) The Mid Atlantic Rift D) The Andes E) The Grand Canyon's eroded depths Answer: E Diff: 2 Section Ref: 4.5 56) The motion of the tectonic plates is driven by A) the gravitational pull of the Moon and Sun. B) the elliptical nature of Earth's orbit.

C) heat moving by convection.

D) magnetic repulsion.

E) Earth's subsurface convection cycle.

Answer: E Diff: 2 Section Ref: 4.5 57) The chief erosive agent now on the Moon is A) lunar ice melting and refreezing in the polar regions.

B) lava flows welling up in the mare.

C) volcanic vents in the rugged highlands.

D) the rain of micrometeorites chewing up the regolith.

E) rain from cometary debris melting as it enters the Moon's atmosphere.

Answer: D Diff: 2 Section Ref: 4.6 58) The rate of cratering A) has remained constant over the last 4.6 billion years.

B) has recently increased with more collisions in the asteroid belt.

C) fluctuates over time, with massive bodies occasionally coming in from the Oort Cloud.

D) shows that large asteroid impacts are more common now than in the past.

E) shows that most interplanetary debris was swept up soon after the formation of the solar system.

Answer: E Diff: 2 Section Ref: 4.6

12 ..

59) The rate of cratering in the lunar highlands shows us that A) they must be younger than the older, darker mare.

B) they range from 4.6 - 4.4 billion years old, on average.

C) the largest impacts are the youngest, such as Copernicus and Tycho.

D) the oldest rocks are at least as old as the mare, but some craters are much younger.

E) most of the asteroids must have hit the Moon, not the Earth.

Answer: B Diff: 2 Section Ref: 4.6 60) The average rate of erosion on the Moon is far less than on Earth because A) the crust of the Moon is much denser than the Earth's crust.

B) the Moon is much younger than the Earth.

C) the Moon lacks wind, water and an atmosphere.

D) the Moon's magnetic field protects it from the solar wind better than ours does.

E) the Moon's mare long ago dried up, so there is no more wave erosion there.

Answer: C Diff: 2 Section Ref: 4.6 61) Which type of feature is the best evidence of lunar volcanism?

A) Rays around the latest eruptions B) Craters all over the Moon C) Vents seen erupting in the mountainous highlands D) Rilles associated with lava flows accompanying the mare formation E) The Orientale Basin Answer: D Diff: 2 Section Ref: 4.6 62) These are found on the side of the Moon that faces Earth, but not on the far side.

A) Highlands B) Maria C) Craters D) Mountains E) Valleys Answer: B Diff: 1 Section Ref: 4.6

13 ..

63) Which lunar feature most resembles the Moon's original crust?

A) Valleys B) Craters C) Maria D) Bright rays E) Highlands Answer: E Diff: 1 Section Ref: 4.6 64) When strong solar winds are displaced poleward by our magnetic fields, we get A) the Van Allen radiation belts.

B) intense auroral displays.

C) sunspots.

D) hurricanes in the tropics.

E) droughts and dust bowls in the American West.

Answer: B Diff: 1 Section Ref: 4.7 65) The region around Earth where the magnetic field traps charged particles is the A) ozone layer.

B) exosphere.

C) Van Allen Radiation Belts.

D) corona.

E) aurora borealis and australis.

Answer: C Diff: 2 Section Ref: 4.7 66) The presence of a magnetic field is a good indication that A) the Earth's interior is similar to Mercury's, as both have fields.

B) a huge iron meteorite lies somewhere high up in the mantle, not in the core.

C) we have a liquid metal outer core, spinning rapidly as we rotate.

D) the Earth's interior must be completely molten to the center.

E) the Earth's interior has had time to solidify, with a rigid bar magnet created.

Answer: C Diff: 2 Section Ref: 4.7

14 ..

67) The Dynamo Theory holds that A) lightning plays a major role in generating our magnetic fields.

B) any other planet of similar density will also have a strong magnetic field.

C) the Earth's core, like Mercury's, is now a solid, rigid bar magnet.

D) magnetic fields are generated by rapidly spinning, fluid magnetic interiors.

E) the Earth's magnetic field must switch polarities every few million years.

Answer: D Diff: 2 Section Ref: 4.7 68) Earth's magnetic field A) prevents charged particles in the solar wind from reaching the surface.

B) is a remnant of the solar nebula's magnetic field.

C) is weakening the Van Allen radiation belts.

D) is the force behind plate tectonics.

E) lines intersect the atmosphere at the equator.

Answer: A Diff: 2 Section Ref: 4.7 69) The Moon's crust is thickest on the ________ side.

Answer: far Diff: 2 Section Ref: 4.1 70) The Moon's crust is ________ km thick on the Earth side and ________ km thick on the far side.

Answer: 30, 45 Diff: 3 Section Ref: 4.1 71) The Earth's atmosphere and magnetosphere contribute ________% to the total mass of the Earth.

Answer: Less than 0.1 Diff: 2 Section Ref: 4.1 72) Each day, there are ________ high tides on Earth.

Answer: 2 Diff: 1 Section Ref: 4.2 73) Because of ________, the Moon is moving away from the Earth at about 4 centimeters per century.

Answer: tides Diff: 2 Section Ref: 4.2 15 ..

74) Evidence that the Earth was nearly molten at one time comes from the differentiation of materials by ________ from core to crust.

Answer: density Diff: 2 Section Ref: 4.3 75) A hot, molten body of different materials will become ________.

Answer: differentiated Diff: 2 Section Ref: 4.3 76) Which side of the Moon has the thicker crust? Why? Answer: The far side, because our tides pulled the molten core toward us, making the Earth side crust thinner.

Diff: 2 Section Ref: 4.3 77) Most of the information about the Moon's internal structure comes from ________ left on the lunar surface by Apollo astronauts.

Answer: seismographs Diff: 1 Section Ref: 4.3 78) The partial trapping of solar radiation is known as the ________.

Answer: Greenhouse Effect Diff: 1 Section Ref: 4.4 79) The various layers of the atmosphere are distinguished by the behavior of the ________.

Answer: temperature Diff: 1 Section Ref: 4.4 80) Plate ________ is the process by which convection within the mantle reforms the crust above it.

Answer: tectonics Diff: 1 Section Ref: 4.5 81) The lunar regolith is constantly eroded by ________.

Answer: meteorite impacts Diff: 2 Section Ref: 4.6

16 ..

82) Lunar ________ are the result of ancient lava flows on the Moon.

Answer: maria Diff: 1 Section Ref: 4.5 83) When strong solar wind storms are diverted poleward by our magnetic fields, we often observe ________ in the ionosphere.

Answer: aurorae Diff: 2 Section Ref: 4.7 84) The auroral displays occur in our ________.

Answer: ionosphere Diff: 2 Section Ref: 4.7 85) List the six main regions of the Earth, in order, starting from the center.

Answer: core, mantle, crust, hydrosphere, atmosphere, magnetosphere Diff: 3 Section Ref: 4.1 86) What layers of the Earth's structure are not present in the Moon's structure?

Answer: hydrosphere, atmosphere, magnetosphere Diff: 2 Section Ref: 4.1 87) What does it mean when we say the Earth's interior is differentiated?

Answer: In a molten state, the denser materials sank to our core, and the lighter material rose to form our crust.

Diff: 1 Section Ref: 4.3 88) What were the two primary courses of heating that let the Earth differentiate? Which is more important to us today?

Answer: Impacts of asteroids and radioactive decay. Radiation decay of radioactive elements still provides the energy to drive plate tectonics.

Diff: 2 Section Ref: 4.3 89) Why did the Moon's internal heat escape more rapidly than Earth's?

Answer: Because of the Moon's small size, heat could escape more quickly. The Earth's rocky layers act as a layer of insulation, making it harder for the heat to escape.

Diff: 1 Section Ref: 4.3

17 ..

90) Which side of the Moon has the thicker crust? Why? Answer: The far side, because our tides pulled the molten core toward us, making the Earth side crust thinner.

Diff: 2 Section Ref: 4.3 91) Weather occurs in which layer of the atmosphere? Why? Answer: The troposphere is where convection occurs, which leads to weather.

Diff: 1 Section Ref: 4.4 92) Name the four layers of the Earth's atmosphere, going up from the surface.

Answer: troposphere, stratosphere, mesosphere, ionosphere Diff: 2 Section Ref: 4.4 93) Note at least three surface features that are driven by plate tectonics.

Answer: Rift valleys, trenches, mountain ranges, volcanic chains, faults, etc.

Diff: 1 Section Ref: 4.5 94) Where is the newest material in the Earth's crust found?

Answer: At the mid-ocean ridges, where plate tectonics constantly extrudes new lava.

Diff: 2 Section Ref: 4.5 95) What is the primary source of erosion on the Moon today?

Answer: Meteorite and micrometeorite bombardment of the surface slowly reduces and alters the features, creating a thick layer of dust.

Diff: 3 Section Ref: 4.6 96) Name two consequences of the Earth's magnetic field detected from space.

Answer: The Van Allen radiation belts lie around our equator, and the tail of charged particles much like a comet's tail extending past the Moon.

Diff: 3 Section Ref: 4.7 97) Compare and contrast the structure of the Earth and the Moon.

Answer: Both objects have layers. Both have cores, mantles and crusts. The Earth's core is divided into two layers: inner (solid) and outer (molten) cores. The Earth has a hydrosphere, an atmosphere and a magnetosphere that the Moon lacks.

Diff: 2 Section Ref: 4.1

18 ..

98) Explain what causes high tides on Earth.

Answer: The Moon is closest to the side facing it, so the pull is strongest there. The oceans on that side bulge towards the Moon. The Moon is a little further from the basically solid Earth, so it pulls more on that than on the oceans on the far side. The oceans on the far side are "left behind," creating a second bulge there.

Diff: 2 Section Ref: 4.2 99) Describe the two different kinds of seismic waves. Distinguish between them by describing how they move through Earth's interior.

Answer: S-waves cause side-to-side motion. These waves cannot travel through liquid, so they do not make it through Earth's liquid outer core. P-waves vibrate the material through which they pass back and forth along the direction of travel of the wave. P-waves go a little faster than Swaves. Also P-waves can travel through liquid so these can be seen on the other side of the planet from the earthquake source.

Diff: 3 Section Ref: 4.3 100) How do earthquakes allow us to model the structure of Earth's core?

Answer: Examining the different seismic waves we find P and S waves are not recorded by all over the planet. There is a blind spot for S waves on the side of Earth opposite the earthquake, and there is a shadow zone part way around the surface from the earthquake. Since we know S waves cannot travel through liquid and P waves can, we conclude the Earth's core is liquid. Since P waves bend when they enter the liquid core, but some travel straight through, it implies there is a solid center to the liquid outer core.

Diff: 3 Section Ref: 4.3 101) What is the greenhouse Effect and why is it vital to life here?

Answer: The gases carbon dioxide and water vapor trap infrared energy close to the Earth's surface, warming us enough to keep the hydrosphere liquid. With no Greenhouse heating, the surface temperature of Earth would average -23 degrees Celsius and the oceans would freeze.

Diff: 2 Section Ref: 4.4 102) What are some of the consequences that could happen if the average global temperature increases by 5 Kelvin, as predicted if the carbon dioxides continue to rise at the current rate?

Answer: Melting of polar ice caps and dramatic climate change. Also (not directly mentioned), melting of glaciers, rise in sea level of up to a meter, longer and more extreme periods of severe weather, crop failures, expansion of deserts in equatorial regions and increase numbers of mosquitoes and other pests.

Diff: 2 Section Ref: 4.4

19 ..

103) Relate the formation of the Himalayas to plate tectonics.

Answer: In the last 30 million years, the northward motion of the Indian plate has caused it to ram into Eurasia, with the light continental plates in collision having no way to go but up, making the roof of the world.

Diff: 2 Section Ref: 4.5 104) Describe several features on the Earth's crust explained by plate tectonics.

Answer: Mountain ranges, volcanic mountain chains, mid-ocean rifts, oceanic trenches, faults, earthquakes, and plate motion.

Diff: 2 Section Ref: 4.5 105) What is the principal evidence that new plate material is continually being formed?

Answer: The material in the Mid-Atlantic Rift is very new, and as you go either eastward or westward from it, the igneous rocks are older by radioactive dating. Similar trends are seen on the volcanoes of Hawaii.

Diff: 3 Section Ref: 4.5 106) Why do volcanic mountain chains, such as the Andes, accompany deep trenches like the Nazca Trench off South America?

Answer: When plate tectonics causes a denser oceanic plate beneath a moving continent, the basalt sinks down into a deep trench, but the heat of subduction causes molten magma to rise up under the edge of the continent, creating volcanoes.

Diff: 3 Section Ref: 4.5 107) Explain how crater counts allow us to estimate the ages of surfaces throughout the solar system.

Answer: Craters are the rule...everybody was a target in the early days of accretion. The longer the surface has sat without internal deformation, the more impacts have cratered the surface. If craters are absent, it is because other processes, such as lava flows or erosion, have replaced the older cratering.

Diff: 2 Section Ref: 4.6 108) What is the primary source of erosion on the Moon? Why does change there take so long?

Answer: A constant fall of meteoroids from space pelts the Moon, pulverizing the surface with tiny craters. But really big impacts are rare, and these microscopic changes take a long time to show up as seen from Earth. Our erosive agents like wind, water, and ice can make much more dramatic changes in short periods of time, such as floods, sandstorms, glaciers, etc.

Diff: 3 Section Ref: 4.6

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 5 The Eight Planets 1) Scarps on Mercury are formed by tectonic uplift.

Answer: FALSE Diff: 2 Section Ref: 5.1 2) On Venus, the Coronae are volcanic features.

Answer: TRUE Diff: 1 Section Ref: 5.1 3) The tallest volcano in the solar system is Mauna Kea, when measured from its base on the ocean floor to its highest point.

Answer: FALSE Diff: 1 Section Ref: 5.1 4) Running water played a major role in shaping Mars in ancient times.

Answer: TRUE Diff: 2 Section Ref: 5.2 5) Running water continues to be the major erosive factor of Mars today.

Answer: FALSE Diff: 2 Section Ref: 5.2 6) The surface temperature of Venus is 750 K, even hotter than Mercury.

Answer: TRUE Diff: 2 Section Ref: 5.3 7) Venus' clouds are water vapor and are similar to clouds in Earth's atmosphere.

Answer: FALSE Diff: 1 Section Ref: 5.3 8) Atmospheric pressure on Mars is roughly half that of Earth's at sea level.

Answer: FALSE Diff: 2 Section Ref: 5.3

1 ..

9) Colors in Jupiter's clouds are largely due to helium compounds.

Answer: FALSE Diff: 2 Section Ref: 5.4 10) Saturn's cloud layer is over twice as thick as Jupiter's cloud layer.

Answer: TRUE Diff: 2 Section Ref: 5.4 11) The Great Dark Spot on Neptune is probably as stable as Jupiter's famed Great Red Spot.

Answer: FALSE Diff: 2 Section Ref: 5.4 12) Europa is the most promising of the bodies in the outer solar system for life in its salty seas.

Answer: TRUE Diff: 2 Section Ref: 5.5 13) We have found Titan's surface to be perfect living condition for earthlike life.

Answer: FALSE Diff: 2 Section Ref: 5.5 14) Life is thought to be unlikely in subsurface oceans, such as those in Europa, because sunlight does not reach these oceans.

Answer: FALSE Diff: 2 Section Ref: 5.5 15) Relative to the size of the planet, Mercury has the largest core of any planet.

Answer: TRUE Diff: 2 Section Ref: 5.6 16) Mars has a weak magnetic field.

Answer: TRUE Diff: 2 Section Ref: 5.6 17) Jupiter puts back into space twice the energy it gets from the Sun. Answer: TRUE Diff: 2 Section Ref: 5.6

2 ..

18) All 4 jovian planets have a layer of molecular hydrogen above a layer of metallic hydrogen.

Answer: FALSE Diff: 2 Section Ref: 5.6 19) Jupiter's magnetic field is much stronger than Earth's, and has a magnetic tail that extends beyond the orbit of Saturn.

Answer: TRUE Diff: 2 Section Ref: 5.7 20) Saturn has a magnetic field whose strength is similar to the Earth's.

Answer: TRUE Diff: 2 Section Ref: 5.7 21) Uranus' rotation axis is tipped over 98 degrees, so its magnetosphere is tipped over the same amount.

Answer: FALSE Diff: 2 Section Ref: 5.7 22) Both have strangely tilted magnetic fields, but that of Uranus is even farther off the rotational axis than that of Neptune.

Answer: TRUE Diff: 2 Section Ref: 5.7 23) The scarps on Mercury were probably caused by A) tectonic activity.

B) meteorite bombardment.

C) a tidal bulge.

D) volcanism.

E) the interior cooling and shrinking.

Answer: E Diff: 2 Section Ref: 5.1 24) Mercury's surface most resembles that of which other body?

A) Earth B) Moon C) Venus D) Mars E) Io Answer: B Diff: 1 Section Ref: 5.1 3 ..

25) Which of the following characterizes a shield volcano?

A) It is dormant.

B) It can erupt only briefly before being dragged off the hot spot.

C) It sits above a hot spot in the planet's crust or mantle.

D) It forms along a plate boundary.

E) It cannot grow very large, for it has a very short span of eruption.

Answer: C Diff: 2 Section Ref: 5.1 26) Which statement is TRUE of Venus' surface?

A) It has remained unchanged for billions of years.

B) Atmospheric pressure is very low.

C) There is an extensive hydrosphere.

D) There are no shield volcanoes.

E) There are two continent sized uplands.

Answer: E Diff: 2 Section Ref: 5.1 27) The most striking and largest valley in the solar system is A) the Grand Canyon in Arizona.

B) Gwenivere on Venus.

C) the Discovery Scarp of Mercury.

D) Valles Marineris on Mars.

E) Valhalla on Callisto.

Answer: D Diff: 1 Section Ref: 5.1 28) The largest shield volcano yet discovered is A) Maxwell Mons on Venus.

B) Kilimanjaro on Earth.

C) Olympus Mons on Mars.

D) Prometheus on Io. E) Caloris on Mercury.

Answer: C Diff: 1 Section Ref: 5.1

4 ..

29) The largest difference between Mars' northern and southern hemispheres is that A) the southern appears older, with more impact craters.

B) the northern has all the outflows and must have been much hotter.

C) the northern is higher overall, despite some high volcanoes in the south.

D) the southern has a polar cap, but none ever forms in the north.

E) the southern is much darker, with large mare-like basaltic lava flows.

Answer: A Diff: 2 Section Ref: 5.1 30) That the Tharsis region on Mars has so few craters A) proves tectonic activity is taking place.

B) is due to the regions very low elevation.

C) suggests it is the youngest region on the planet.

D) suggests it is at the center of a particularly strong magnetic field.

E) is due to annual flooding and water erosion.

Answer: C Diff: 3 Section Ref: 5.1 31) The outflow channels on Mars indicate a flood period in the history of Mars. During this time, based on the width and depth of the remaining riverbed, it is thought that the flow rate must have been A) just a small trickle, barely more than a stream of water.

B) moderate, about the flow rate of the Ohio River.

C) fairly large, about the flow rate of the current Colorado River.

D) significantly large, about the flow rate of the Amazon River.

E) enormous, as much as 100 times the flow rate of the Amazon River.

Answer: E Diff: 2 Section Ref: 5.2 32) The runoff channels on Mars were most likely formed by A) melting underground ice.

B) catastrophic, but rare flooding C) the annual melting of the polar ice caps.

D) glaciers.

E) rain that was part of a water cycle.

Answer: B Diff: 2 Section Ref: 5.2

5 ..

33) Evidence of liquid water in Mars' distant past suggests that it had a substantial atmosphere compared to what it has presently. What happened to its water vapor?

A) The carbon dioxide in its atmosphere dissolved in the water and combined with surface rocks.

B) Its atmosphere was mostly hydrogen and helium. Mars' gravity is too weak to hold them.

C) The water vapor has frozen out into the polar ice caps and permafrost as Mars has cooled.

D) Mars initially had such a large greenhouse effect that the atmosphere became quite hot and slowly escaped.

E) It has now all been lost in space, including the carbon dioxide and water vapor.

Answer: C Diff: 2 Section Ref: 5.2 34) The atmospheric pressure on Venus A) shows an extreme change with the seasons.

B) is much lower than on Earth.

C) is about the same as on Mercury.

D) is much higher than on Earth.

E) causes variations in surface temperature.

Answer: D Diff: 1 Section Ref: 5.3 35) What is the result of the Greenhouse effect on the surface environment of Venus?

A) It has little or no effect.

B) Its effect is about the same as on Earth.

C) It has reduced the surface temperature by about 30 degrees Celsius.

D) It has raised the surface temperature by hundreds of degrees Celsius.

E) It causes the surface temperature of Venus to become hotter than the Sun. Answer: D Diff: 1 Section Ref: 5.3 36) What is the main constituent of the atmosphere of Venus?

A) Oxygen B) Nitrogen C) Hydrogen D) Carbon dioxide E) Sulfuric acid Answer: D Diff: 1 Section Ref: 5.3

6 ..

37) What is the composition of the clouds of Venus?

A) Water, like Earth's clouds B) Frozen carbon dioxide, as on Mars C) A combination of ammonia and methane, like Uranus D) Sulfur and sulfuric acid droplets E) Hydrogen sulfide and ammonia Answer: D Diff: 2 Section Ref: 5.3 38) The main constituent of the Martian atmosphere is A) hydrogen.

B) helium.

C) methane.

D) carbon dioxide.

E) nitrogen.

Answer: D Diff: 1 Section Ref: 5.3 39) Venus and Mars probably evolved differently from Earth because A) they are slightly bigger than Earth.

B) they are more massive than Earth.

C) they have thicker atmospheres than the Earth.

D) they formed sooner than Earth.

E) they orbit at different distances from the Sun. Answer: E Diff: 1 Section Ref: 5.3 40) Compare the atmospheres of Mars and Venus.

A) Both are made of hydrogen and helium, like the jovians.

B) Like Earth, nitrogen is the chief atmospheric gas.

C) Both are chiefly carbon dioxide, but at Mars it can freeze as dry ice.

D) Mars is rich in oxygen, like ours, accounting for its red surface.

E) Both are too hot for water to now exist as a liquid at the surface.

Answer: C Diff: 2 Section Ref: 5.3

7 ..

41) Essentially, the Great Red Spot is A) Neptune's largest atmospheric feature.

B) a large cyclonic storm (hurricane).

C) always located within 10 degrees of Jupiter's north pole.

D) composed primarily of iron oxide.

E) traveling north and south across Jupiter's face.

Answer: B Diff: 1 Section Ref: 5.4 42) The most striking "cloudmark" in Jupiter's atmosphere is the A) Great Dark Spot.

B) Cassini Division.

C) Great Red Spot.

D) Black Hole.

E) Brown Dwarf.

Answer: C Diff: 1 Section Ref: 5.4 43) The belts of Jupiter are best described as follows A) regions of downward moving material and low pressure.

B) regions of upward moving material and low pressure.

C) regions of upward moving material and high pressure.

D) regions of downward moving material and high pressure.

E) turbulent regions with no organized circulation pattern.

Answer: A Diff: 2 Section Ref: 5.4 44) Together which two gases make up 99% of Jupiter's atmosphere?

A) Ammonia and methane B) Water vapor and methane C) Helium and ammonia D) Hydrogen and ammonia E) Hydrogen and helium Answer: E Diff: 3 Section Ref: 5.4

8 ..

45) Alternating zones of rising and sinking gas in Jupiter's atmosphere A) create light and dark bands.

B) cause Jupiter's magnetic field to ripple.

C) produced the ring system discovered by Voyager.

D) generate their own magnetic fields.

E) circle the planet from pole to pole.

Answer: A Diff: 3 Section Ref: 5.4 46) The atmosphere of Saturn is composed mostly of A) methane and ammonia.

B) carbon dioxide and ethane.

C) hydrogen and helium.

D) hydrogen sulfide and ammonia.

E) nitrogen and oxygen.

Answer: C Diff: 1 Section Ref: 5.4 47) Saturn's cloud surface appears more uniform than Jupiter's because A) there is a thick outer cloud covering of water ice overlying the colorful ices.

B) due to Saturn's lower gravity, the colorful cloud layers escaped.

C) it is composed of completely different gases than Jupiter's.

D) the cloud layers are thicker, allowing fewer holes to see the colorful layers.

E) due to Saturn's greater distance from the Sun, the colorful cloud layers are just not visible.

Answer: D Diff: 2 Section Ref: 5.4 48) Saturn's bands, oval storm systems, and turbulent flow patterns are powered by A) convective motion and rapid rotation.

B) the greenhouse effect.

C) a liquid metallic hydrogen interior.

D) the fusion in Saturn's core.

E) the tides of Titan.

Answer: A Diff: 1 Section Ref: 5.4

9 ..

49) Neptune and Uranus have a bluish tint because A) at their distances, the Sun appears blue, the red absorbed by dust in the ecliptic.

B) they are far away and distance makes objects appear bluish.

C) their atmospheres contain methane, which absorbs red light.

D) their atmospheres contain hydrogen and helium.

E) ammonia ice reflects blue light better than any other color.

Answer: C Diff: 1 Section Ref: 5.4 50) In 1989, Neptune was found to have a huge storm named the A) South Tropical Disturbance.

B) Great Red Spot.

C) Great Dark Spot.

D) Hellas Basin.

E) Galileo Regio.

Answer: C Diff: 2 Section Ref: 5.4 51) The most abundant component of the atmospheres of Uranus and Neptune is A) hydrogen.

B) helium.

C) methane.

D) ammonia.

E) nitrogen.

Answer: A Diff: 2 Section Ref: 5.4 52) Which planet had the Great Dark Spot in 1989, but had lost it by 1995?

A) Jupiter B) Saturn C) Uranus D) Neptune E) Mars Answer: D Diff: 2 Section Ref: 5.4

10 ..

53) In addition to Mars, which jovian moon shows some promise of life, with a surface not that different from the Arctic Ocean?

A) Titan B) Miranda C) Europa D) Io E) Triton Answer: C Diff: 2 Section Ref: 5.5 54) Evidence of liquid water has not been seen on which of these jovian moons?

A) Titan B) Ganymede C) Europa D) Mimas Answer: D Diff: 2 Section Ref: 5.5 55) If jovian moons harbor life, this life is likely to resemble what terrestrial organisms?

A) Bacteria B) Extremophiles C) Dolphins D) Moss E) Dinosaurs Answer: B Diff: 1 Section Ref: 5.5 56) How does Mercury's magnetic field compare to our own?

A) Like Venus, Mercury has no detectable magnetic field.

B) Like Mars and the Earth, it too has undergone polarity reversals.

C) It is much weaker than Earth's, but does deflect the solar wind to some degree.

D) It is amazingly strong, comparable to our own.

E) It was predicted from Mercury's rapid rotation and molten core.

Answer: C Diff: 2 Section Ref: 5.6

11 ..

57) What two properties of Mercury imply that it is differentiated?

A) Its size and magnetic field B) Its large average density and its surface features C) Its surface features and its size D) Its large average density and its magnetic field E) Its magnetic field and its surface features Answer: D Diff: 2 Section Ref: 5.6 58) The presence of a Mercurian magnetic field surprised the planetary scientists on the Mariner 10 team because A) Mercury is low in iron.

B) Mercury spins too rapidly to produce a stable dynamo.

C) it's still too hot for its core to have differentiated.

D) the dynamo theory predicted that Mercury was spinning too slowly for one.

E) Mercury lacks an iron core.

Answer: D Diff: 2 Section Ref: 5.6 59) Mars' magnetic field is so weak because A) it spins much slower than Earth does.

B) it core may no longer be molten.

C) its core contains less iron than our own.

D) Both B and C are probable.

E) All of the above are correct.

Answer: D Diff: 3 Section Ref: 5.6 60) How does the heat Jupiter radiates compare to the energy it receives from the Sun? A) They are equal, as you would expect for a highly reflective planet.

B) Jupiter's dark belts absorb most of the solar radiation, so it is cooler in the infrared.

C) Jupiter radiates back into space about twice the energy it gets from the Sun. D) Jupiter is a brown dwarf, about a hundred times less luminous than the Sun. E) Jupiter is a red dwarf, about a tenth the Sun's luminosity.

Answer: C Diff: 2 Section Ref: 5.6

12 ..

61) What is the source of Jupiter's excess energy?

A) Helium rain falling through its interior B) The decay of radioactive elements in its dense core C) Nuclear fusion in its hot, sunlike core of hydrogen D) The slow escape of gravitational energy released during the planet's formation E) The tidal stresses of the large Galilean moons Answer: D Diff: 2 Section Ref: 5.6 62) What is thought to lie at the center of Jupiter?

A) A hot sea of liquid metallic hydrogen B) A solid core of crystalline helium C) A massive core of rocky materials with some iron mixed in D) Gaseous hydrogen and helium, for Jupiter is not differentiated like Earth E) A fusion core like the Sun's, with hydrogen being turned into helium Answer: C Diff: 2 Section Ref: 5.6 63) Why does the atmosphere of Saturn appear to have only half the helium content of Jupiter?

A) Because Saturn is so much colder, helium does not show up as strongly in its spectrum.

B) Saturn was formed farther from the helium rich Sun. C) A red dwarf, Jupiter has fused some of its hydrogen into helium, whereas Saturn, a colder planet, has not.

D) Much of Saturn's helium has differentiated towards its center.

E) Much of Saturn's helium has reacted with water and formed helium oxide.

Answer: D Diff: 2 Section Ref: 5.6 64) Why does Saturn radiate even more excess energy than Jupiter?

A) Saturn is still radiating heat left over from its formation.

B) Saturn's thick cloud layer contributes to a larger greenhouse effect.

C) Helium rain gives off heat as it differentiates toward Saturn's center.

D) Saturn's atmosphere contains much methane, creating a large greenhouse effect.

E) Saturn can fuse hydrogen into helium in its core, like the Sun. Answer: C Diff: 2 Section Ref: 5.6

13 ..

65) An important structural feature of Jupiter and Saturn, that is not found in Uranus and Neptune, is A) a large core with a composition similar to a terrestrial planet.

B) a hydrosphere.

C) plate tectonics.

D) a thick layer of metallic hydrogen.

E) a thick layer of molecular hydrogen.

Answer: D Diff: 2 Section Ref: 5.6 66) What is TRUE of Jupiter's magnetosphere?

A) Although its surface field is greater, since the planet is larger the total field is actually weaker than Earth's.

B) It does not trap protons and electrons, as Earth's Van Allen belts do.

C) It has a tail that extends at least to Saturn's orbit.

D) It is most extensive on the sunward side of the planet.

E) It is only slightly stronger than Saturn's.

Answer: C Diff: 2 Section Ref: 5.7 67) What is the source of Jupiter's intense magnetic field?

A) Charged particles trapped in Jupiter's solid iron core similar to Earth B) Liquid metallic hydrogen swirling in the rapidly spinning mantle C) The ionized sulfur ejected into a torus around Jupiter by Io D) The auroral displays in the polar regions, just like with the Earth E) A liquid iron and nickel outer core, just like the Earth's magnetic field Answer: B Diff: 2 Section Ref: 5.7 68) Compared to its rotational axis, Jupiter's magnetic field A) is exactly in alignment.

B) lies about 10 degrees off, much like our own rotation and magnetic field.

C) is tilted about 23.5 degrees, much like our own axial tilt.

D) is tilted 98 degrees, much like the case of Uranus.

E) has yet to be detected.

Answer: B Diff: 2 Section Ref: 5.7

14 ..

69) How large is Jupiter's magnetosphere?

A) It is about as large as the Earth's.

B) It is so large it extends out to the orbit of Io. C) It is a million times the volume of the Earth's, extending beyond the orbit of Saturn.

D) It extends inward to the orbit of Mars.

E) It envelopes even the Sun and rest of the solar system.

Answer: C Diff: 2 Section Ref: 5.7 70) What do our magnetic field and Jupiter's share?

A) Similar field strength B) Same polarity C) Auroral displays in the polar regions D) Fields that extend inward all the way to the Sun E) Fields that extend outward past Pluto Answer: C Diff: 2 Section Ref: 5.7 71) How does the magnetic tilt of Jupiter compare with our field?

A) Both are exactly perpendicular to our equator, aligned with our rotation axis.

B) Jupiter's lies perpendicular to the ecliptic, while ours is tilted 23.5 degrees.

C) Both are tilted about 10 degrees, but Jupiter is opposite in polarity.

D) Both are tilted about 27 degrees, much like Saturn's.

E) Like Uranus, Jupiter is flopped over on its side.

Answer: C Diff: 3 Section Ref: 5.7 72) At the surface of Saturn's atmosphere the strength of the magnetic field is A) about the same as Mercury's magnetic field at its surface.

B) about the same as Venus' magnetic field at its surface.

C) about the same as Earth's magnetic field at its surface.

D) about the same as Mars' magnetic field at its surface.

E) about the same as Jupiter's magnetic field at its atmospheric surface.

Answer: C Diff: 2 Section Ref: 5.7

15 ..

73) The magnetic field tilts of which two bodies are the most unusual?

A) Mercury and Earth B) Jupiter and Saturn C) Uranus and Neptune D) Saturn and Venus E) Mars and Saturn Answer: C Diff: 2 Section Ref: 5.7 74) In strength, the magnetic fields of Uranus and Neptune are A) very different, with flopped over Uranus having no field, and Neptune a strong one.

B) similar, with both about 100 times stronger than our own.

C) even stronger than that of Jupiter.

D) perfect fits for the Dynamo theory.

E) like Jupiter and Saturn, due to mantles of liquid metallic hydrogen.

Answer: B Diff: 3 Section Ref: 5.7 75) Which statements about the magnetic fields of Uranus and Neptune is FALSE? A) Neither fits the Dynamo model very well.

B) Uranus' field is tilted 60 degrees off its already tilted rotational axis.

C) Neptune's field is tilted 47 degrees to its more conventional rotational axis.

D) Both pass directly through the cores of their planets, like all other fields.

E) Both may have ammonia water replacing the liquid metallic hydrogen.

Answer: D Diff: 3 Section Ref: 5.7 76) While it has some high volcanoes, most of Venus is relatively ________ in elevation.

Answer: low Diff: 2 Section Ref: 5.1 77) The ________ hemisphere of Mars is lower, smoother, and younger than the other one.

Answer: northern Diff: 2 Section Ref: 5.1 78) The largest volcano in the solar system, ________, is found on Mars.

Answer: Olympus Mons Diff: 2 Section Ref: 5.1

16 ..

79) Most of Mars' water is now locked in a ________ layer below the surface.

Answer: permafrost Diff: 2 Section Ref: 5.2 80) The greenhouse effect on Venus is due to ________ in its atmosphere.

Answer: carbon dioxide Diff: 1 Section Ref: 5.3 81) Venus' high surface temperature is due to the ________ effect.

Answer: greenhouse Diff: 1 Section Ref: 5.3 82) The apparent "surface" of Jupiter is actually the tops of ________.

Answer: clouds Diff: 1 Section Ref: 5.4 83) Compared to Jupiter, Saturn's upper atmosphere is notably lacking in the element ________.

Answer: helium Diff: 2 Section Ref: 5.4 84) Saturn's cloud layers are thicker than Jupiter's, due to Saturn's ________ gravity.

Answer: lower or weaker Diff: 2 Section Ref: 5.4 85) The Great ________ Spot of Neptune was striking in 1989, but gone by 1995.

Answer: Dark Diff: 1 Section Ref: 5.4 86) Because of its high mean density and magnetic field, Mercury's large core must be made chiefly of ________.

Answer: iron Diff: 1 Section Ref: 5.6 87) Jupiter radiates twice as much energy as it receives from solar light; the source of this "excess" energy is ________.

Answer: gravitational contraction Diff: 2 Section Ref: 5.6 17 ..

88) Jupiter has a large ________ created by the interaction between the planet's magnetic field and the solar wind.

Answer: magnetosphere Diff: 2 Section Ref: 5.7 89) What are coronae?

Answer: large, circular volcanic upwells on the surface of Venus Diff: 3 Section Ref: 5.1 90) Describe the primary difference between the northern and southern hemispheres on Mars.

Answer: The northern hemisphere is primarily plains (lowlands) with few craters and extensive lava flows. The southern hemisphere is heavily cratered highlands.

Diff: 2 Section Ref: 5.1 91) The vast flood deposits support the hypothesis that Mars once had much running water.

Assuming that Mars did have water once, what happened to it?

Answer: As Martian volcanism died down, the atmosphere became too thin for greenhouse gases to keep the water liquid. Most froze in the polar caps or as tundra underground, and some was also lost into space.

Diff: 2 Section Ref: 5.2 92) Where is most of the water on Mars believed to be?

Answer: In the polar caps and a layer of permafrost just below the surface.

Diff: 2 Section Ref: 5.2 93) If Mars' atmosphere is mostly carbon dioxide, why isn't it as hot as Venus?

Answer: Although it has a carbon dioxide atmosphere, Mars' atmosphere is very thin, much less dense than Venus' or even Earth's.

Diff: 1 Section Ref: 5.3 94) What is the primary effect the carbon dioxide in Venus' atmosphere has on the planet.

Answer: The high concentration of carbon dioxide has caused a runaway greenhouse effect which results in very high surface temperatures.

Diff: 2 Section Ref: 5.3 95) Why is the atmospheric pressure at the surface of Venus so much higher than Earth's?

Answer: The atmosphere is much more massive than Earth's and extends to a much greater height above the surface.

Diff: 3 Section Ref: 5.3 18 ..

96) What are the two principal components of Jupiter's atmosphere? How do they relate to its density?

Answer: Hydrogen and helium; these light elements, even under high compression, give Jupiter a density only about a quarter that of the Earth.

Diff: 1 Section Ref: 5.4 97) Contrast the compositions of Jupiter's belts and zones.

Answer: The zones are high, cold regions of ammonia ice crystals, white in color. But the lower, warmer belts are brownish from complex chemistry involving hydrogen sulfide, ammonia, and other chemicals.

Diff: 2 Section Ref: 5.4 98) Discuss the role that methane plays in the appearances of Neptune and Uranus.

Answer: At Uranus and Neptune, methane is the chief coloring agent, absorbing red light strongly, and reflecting the blue light back into space.

Diff: 2 Section Ref: 5.4 99) What evidence is there for liquid water under Europa's surface?

Answer: There are features on Europa that are similar to pressure ridges seen on ice floes on Earth. Chunks of ice that resemble icebergs have been seen to change position, indicating moving water under them. There is at least one region where the icy surface seems to have been pulled apart, with new material filling in.

Diff: 2 Section Ref: 5.5 100) Explain where the energy to keep water liquid in Europa comes from?

Answer: As Europa orbits Jupiter, tidal forces cause it to flex. This heats the interior.

Diff: 2 Section Ref: 5.5 101) Saturn's magnetic field is weaker than Jupiter's because it has less ________.

Answer: metallic hydrogen.

Diff: 2 Section Ref: 5.7 102) In what ways are the magnetic fields of Uranus and Neptune unusual?

Answer: Unlike the magnetic fields of Earth, Jupiter and Saturn, the fields of Uranus and Neptune are not aligned with the rotational axis of their planet. Additionally, both fields are offset from their planet's center by a significant amount.

Diff: 3 Section Ref: 5.7

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103) Relate the formation of Mercury's scarps to its differentiation.

Answer: As Mercury was molten, the dense iron and nickel sank to the core. But smaller Mercury cooled much faster than larger Earth and Venus, so as its core cooled, it also contracted as it solidified. The crust above wrinkled and formed the scarps due to this shrinkage.

Diff: 2 Section Ref: 5.1 104) What is the evidence that suggests the past and present existence of surface water on Mars?

Answer: Runoff channels from old rivers and outflow channels from catastrophic flooding in the distant past. Recent mudflows down the sides of some canyons and crater walls suggest occasional eruptions of liquid water persist to this day, as imaged by the Global Surveyor. The Rovers in 2004 also found clear evidence of sedimentary rocks formed under water at both the landing sites, on opposite sides of the globe.

Diff: 3 Section Ref: 5.2 105) Describe how conditions on Venus have produced a runaway greenhouse effect.

Answer: Because of Venus' proximity to the Sun, carbon dioxide never got absorbed by surface rocks due to higher temperature. Carbon dioxide is a greenhouse gas and traps heat, so this led to still higher temperature, leading to even more carbon dioxide released from rocks in a vicious cycle. The result is a surface temperature of 730 K. Diff: 3 Section Ref: 5.3 106) Describe the circulation of Jupiter's belts and zones.

Answer: The white zones are upwellings, where ammonia ice forms as the currents expand and cool off; the cool gases descend into the darker belts, where hydrogen sulfide adds color and causes them to appear brown.

Diff: 2 Section Ref: 5.4 107) What element is notably deficient in Saturn's atmosphere, and why?

Answer: Helium seems to be condensing and raining downward toward Saturn's mantle.

Diff: 2 Section Ref: 5.4 108) Explain why the two outermost gas giant planets, Uranus and Neptune, appear so different from the innermost gas giant planets Saturn and Jupiter.

Answer: Uranus and Neptune appear significantly different from Jupiter and Saturn because of the differing amounts of ammonia and methane in their outer atmospheres. The amount of ammonia decreases with distance from the Sun because it freezes out below 70 K. Thus Uranus and Neptune have little gaseous ammonia in their atmospheres. Methane is found in increasing abundance with distance from the Sun and gives a blue color to the planets. Uranus appears bluish-green and Neptune, very blue.

Diff: 3 Section Ref: 5.4 20 ..

109) Why was the discovery of a substantial magnetic field around Mercury a surprise? How was it detected?

Answer: In its close passes by Mercury, Mariner 10 found a field that is much stronger than Mercury's very slow rotation would have led us to expect with the dynamo theory.

Diff: 2 Section Ref: 5.6 110) What material makes up most of Jupiter's volume, and why is it not found here?

Answer: Liquid metallic hydrogen can be formed only under tremendous pressure, not found even in the Earth's interior, much less on its surface.

Diff: 2 Section Ref: 5.6 111) Compare and contrast the magnetospheres of Earth and Jupiter. Discuss strength and reaction to solar winds.

Answer: Jupiter's magnetosphere is the strongest of any planet in the solar system. Like Earth's magnetosphere, Jupiter's traps a vast sea of energetic charged particles that surround the planet.

Due to the fast rotation of Jupiter, however, these particles are in a thin, flat current sheet that is located at the planet's magnetic equator. Jupiter's magnetosphere is also less stable than Earth's in the outermost regions. When gusts of solar winds occur, the magnetosphere deflates.

Diff: 2 Section Ref: 5.7 112) In what ways do the magnetic fields of both Uranus and Neptune defy the conventional Dynamo Theory for planetary magnetic fields?

Answer: The planet's rotation, as the word dynamo implies, is paramount in generating the magnetic field, so the field should align itself with the rotational axis; in other words, the N needle on a compass should really point north. For Saturn, it is fine, but at Earth and Jupiter, the field is off by about 10 degrees. However, for Uranus this magnetic tilt is 59 degrees, and even for Neptune it is 47 degrees off. Also, the core of the planet should contain the electrically conductive fluid that generates the field, but for both green giants, the fields do not pass anywhere close to this core.

Diff: 3 Section Ref: 5.7

21 ..

Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 6 Small Bodies in the Solar System 1) All the Galilean moons are in synchronous rotation, with the same face always pointed toward Jupiter, except for tidally stressed Io. Answer: TRUE Diff: 1 Section Ref: 6.1 2) Ganymede has many features that look like its history may be similar to the Earth's Moon's, but with water on Ganymede playing the role of rock on the Moon.

Answer: TRUE Diff: 1 Section Ref: 6.1 3) The most geologically active moon in our solar system is Ganymede.

Answer: FALSE Diff: 1 Section Ref: 6.2 4) The lakes on Titan are almost pure methane.

Answer: FALSE Diff: 1 Section Ref: 6.3 5) Triton shows similar cratering to the Lunar highlands, which suggests that it too is an old surface.

Answer: FALSE Diff: 2 Section Ref: 6.3 6) The leading hemisphere of Iapetus is much darker than the back side, which is icy.

Answer: TRUE Diff: 2 Section Ref: 6.4 7) The moons of Saturn are darker than those of Uranus.

Answer: FALSE Diff: 1 Section Ref: 6.4 8) Most of the midsized jovian moons show heavy cratering.

Answer: TRUE Diff: 1 Section Ref: 6.4

1 ..

9) A typical ring particle is about the size of a snowball.

Answer: TRUE Diff: 2 Section Ref: 6.5 10) Saturn's two shepherd moons herd the particles in the F ring.

Answer: TRUE Diff: 2 Section Ref: 6.5 11) The rings of Saturn occupy the region inside Saturn's Roche limit.

Answer: TRUE Diff: 1 Section Ref: 6.6 12) The particles making up the ring of Jupiter are composed of bright, reflective ice.

Answer: FALSE Diff: 1 Section Ref: 6.6 13) The rings of Uranus were discovered from Earth when the planet passed in front of a star.

Answer: TRUE Diff: 1 Section Ref: 6.6 14) As with Saturn's F ring, shepherd moons play a major role in the structure of the thin narrow rings around Uranus.

Answer: TRUE Diff: 2 Section Ref: 6.6 15) When initially discovered by Voyager 2, Neptune's rings appeared as ring arcs, and are more clumpy and less regular than most other rings.

Answer: TRUE Diff: 2 Section Ref: 6.6 16) All known asteroids can be found in the asteroid belt.

Answer: FALSE Diff: 2 Section Ref: 6.7 17) Pluto is smaller than many moons in the solar system.

Answer: TRUE Diff: 1 Section Ref: 6.8 2 ..

18) Pluto is visible to the naked eye on extremely dark nights.

Answer: FALSE Diff: 2 Section Ref: 6.8 19) Pluto is probably one of the largest of the Kuiper Belt bodies beyond Neptune.

Answer: TRUE Diff: 2 Section Ref: 6.8 20) Which of the Galilean moons is the densest and most geologically active?

A) Io B) Europa C) Ganymede D) Callisto E) Titan Answer: A Diff: 1 Section Ref: 6.1 21) What is the origin of the jovian moons?

A) They all formed with the planet.

B) They were main belt asteroids, captured by Jupiter's strong gravity.

C) They are Trojan asteroids, orbiting 60 degrees ahead or behind Jupiter.

D) The four Galilean moons formed with Jupiter, most others were later captures.

E) They were ripped from the planet's interior in an early cataclysmic event.

Answer: D Diff: 2 Section Ref: 6.1 22) The surface of which jovian moon most resembles the pack ice of the Arctic Ocean?

A) Amalthea B) Io C) Europa D) Ganymede E) Callisto Answer: C Diff: 2 Section Ref: 6.1

3 ..

23) Of the Galilean satellites, which has the oldest, most heavily cratered surface?

A) Titan B) Io C) Europa D) Callisto E) Ganymede Answer: D Diff: 2 Section Ref: 6.1 24) Of the Galilean moons, the one with striking grooved terrain and icy tectonic features as well as older craters is A) Amalthea.

B) Io. C) Europa.

D) Ganymede.

E) Callisto.

Answer: D Diff: 2 Section Ref: 6.1 25) Which of the jovian moons is the largest and also the largest moon in the solar system, even bigger than Mercury?

A) Titan B) Triton C) Ganymede D) Callisto E) Umbriel Answer: C Diff: 2 Section Ref: 6.1 26) In size, from largest to smallest, the correct order for the Galilean moons is A) Callisto, Ganymede, Europa, Io. B) Ganymede, Callisto, Io, Europa.

C) Io, Europa, Callisto, Ganymede.

D) Europa, Ganymede, Io, Callisto.

E) Ganymede, Callisto, Europa, Io. Answer: B Diff: 3 Section Ref: 6.1

4 ..

27) Which of the four Galilean moons is not differentiated?

A) Io B) Europa C) Ganymede D) Callisto E) None of the above. All the moons are differentiated.

Answer: D Diff: 3 Section Ref: 6.1 28) What is thought to be the cause of Io's volcanoes?

A) Jupiter's magnetosphere and its charged particles B) Jupiter's gravity and the heat it creates C) Tidal stresses from both Jupiter and Europa D) Solar radiation focused by Jupiter's gravity E) Radioactive decay in Io's interior Answer: C Diff: 1 Section Ref: 6.2 29) What is the major component of Io's volcanic flows?

A) Basaltic lava, like the lunar mare B) Liquid nitrogen, like the eruptions of Triton C) Sulfur and its compounds D) Carbon dioxide and water vapor, as with our eruptions E) Iron oxide, as on Mars Answer: C Diff: 2 Section Ref: 6.2 30) The largest volcano on Io, Loki, is similar in size, but a bit larger than A) Texas.

B) India.

C) Mauna Kea. D) Maryland.

E) Manhattan.

Answer: D Diff: 2 Section Ref: 6.2

5 ..

31) The highest temperatures of volcanic lava on Io that are A) similar to that of hot springs on Earth.

B) similar to volcanic lava on Earth.

C) similar to the surface temperature of Venus.

D) far hotter than any earthly volcano.

E) just barely hot enough to melt water ice.

Answer: D Diff: 2 Section Ref: 6.2 32) On Io, volcanic eruptions, such as those from Prometheus, can send material how far above the surface?

A) 150 km or more B) 2-3 km C) A few meters D) Just far enough to get a surface flow E) Nowhere—volcanoes are not found on moons.

Answer: A Diff: 2 Section Ref: 6.2 33) What is interesting about Saturn's large moon Titan?

A) It is one of Saturn's two large moons.

B) It has a 2:1 resonance with Mimas and a 4:1 resonance with the Cassini gap.

C) It has its own moon.

D) It orbits Saturn in a retrograde sense.

E) It has an atmosphere.

Answer: E Diff: 2 Section Ref: 6.3 34) The atmosphere of Titan is composed mostly of A) oxygen.

B) methane.

C) carbon dioxide.

D) hydrogen.

E) nitrogen.

Answer: E Diff: 2 Section Ref: 6.3

6 ..

35) What did the Huygens and Cassini probes find on the surface of Titan?

A) Rocks and no water B) Methane oceans C) An ocean and some lakes of methane, ethane, and other hydrocarbons D) Lakes and oceans of water E) No methane, no water; just rocks Answer: C Diff: 2 Section Ref: 6.3 36) What mission landed on Titan in early 2005?

A) Galileo's probe B) Huygens C) New Horizons D) Rover Spirit E) Cassini orbiter Answer: B Diff: 3 Section Ref: 6.3 37) What is the prediction for the future of Triton?

A) It will provide the raw material for a future Neptunian ring.

B) It will develop active volcanoes as Neptune's tidal stresses become greater.

C) It will crash into Nereid when the smaller moon comes too close.

D) Its orbit, while retrograde, is very stable and will not change.

E) Its retrograde orbit will throw it back out into the Kuiper Belt again, with Pluto.

Answer: A Diff: 2 Section Ref: 6.3 38) What is erupting out of the geysers on Triton?

A) Liquid water B) Liquid methane C) Liquid nitrogen D) Liquid carbon dioxide E) Liquid hydrogen Answer: C Diff: 2 Section Ref: 6.3

7 ..

39) In addition to Saturn's Titan, which other moon has a nitrogen atmosphere?

A) Jupiter's Europa B) Uranus' Titania C) Neptune's Triton D) Jupiter's Ganymede E) Pluto's Charon Answer: C Diff: 2 Section Ref: 6.3 40) What evidence suggests that Enceladus has ongoing geological activity?

A) Voyager 2 photographed liquid nitrogen geysers 10 kilometers tall.

B) Lack of impact craters on much of its surface, evidence of ice flows from possible volcanic activity, and geysers that supply material for the E-ring.

C) Voyager 1 showed sulfur eruptions all over its pizza-pie colored surface.

D) Enceladus is located within Saturn's Roche limit, and ready to blow up.

E) Enceladus undergoes severe tidal stresses from its resonance with Titan.

Answer: B Diff: 2 Section Ref: 6.4 41) How many medium-sized moons does Saturn have?

A) Too many to count B) 18 C) 9 D) 6 E) 1 Answer: D Diff: 2 Section Ref: 6.4 42) The "wispy terrain" on Rhea was revealed by the Cassini spacecraft to be A) ice cliffs created by tectonic fractures.

B) water ice flows from past impacts that cracked its icy surface.

C) the icy ash of water volcanoes.

D) "maria" created during the period of high impacts.

E) water ice flows from geyser-like activity.

Answer: A Diff: 2 Section Ref: 6.4

8 ..

43) While not yet observed in eruption, it is likely that ________ has active volcanoes; it certainly has one hemisphere greatly reworked by tectonic and volcanic forces.

A) Dione B) Titan C) Enceladus D) Mimas E) Rhea Answer: C Diff: 3 Section Ref: 6.4 44) What makes Mimas a distinct moon?

A) It suffered a huge meteorite impact that must have nearly shattered it.

B) It helps maintain a wide apparent gap in Saturn's rings, known as Encke's Division.

C) It has a rich atmosphere that may resemble that of the early Earth.

D) It is the largest of Saturn's moons.

E) The leading hemisphere is very dark, while the back side is bright ice.

Answer: A Diff: 3 Section Ref: 6.4 45) Radiation darkening explains why A) there are so many dark craters on the jovian moons.

B) Uranus' moons are darker than Saturn's.

C) Earth's Moon is made of rock, but jovian moons are icy.

D) Iapetus has a two-faced appearance.

Answer: B Diff: 2 Section Ref: 6.4 46) What are Saturn's rings?

A) A great disk of liquid helium B) Large rocky boulders moving in orbit around Saturn C) A glowing, flat magnetospheric auroral display D) A solid thin disc of material encircling Saturn E) Small icy particles moving in orbit around Saturn Answer: E Diff: 1 Section Ref: 6.5

9 ..

47) What did the Voyager mission discover about the main rings of Saturn?

A) There are hundreds of small moons in the ring system.

B) They were less dense than the rings of Jupiter.

C) There are several small moons inside the inner-most ring.

D) The ring system is much thicker than originally believed.

E) They are composed of tens of thousands of narrow ringlets.

Answer: E Diff: 1 Section Ref: 6.5 48) Why are Saturn's rings so noticeable?

A) They are made of metallic hydrogen.

B) They are made of lots of fresh, bright icy particles from a recent breakup.

C) The particles in the rings are highly polished from numerous collisions with other particles.

D) They are made of nitrogen frost, like the bright surface of Triton.

E) Saturn is so bright, the rings reflect a lot of light from both Saturn and the Sun. Answer: B Diff: 1 Section Ref: 6.5 49) Shepherd satellites are defined as A) satellites in the coma of a comet.

B) moons that confine a narrow ring.

C) a type of moon that orbits another moon.

D) moons that follow the exact orbit of another, larger, moon.

E) moons that orbit inside the system of rings.

Answer: B Diff: 2 Section Ref: 6.5 50) What did the Voyager mission discover about the Cassini Division?

A) It actually contains one or more moons.

B) It contains several ringlets.

C) It is completely filled with a ring of very dark material.

D) The spokes originate from it.

E) It is actually completely empty of all ring material.

Answer: B Diff: 2 Section Ref: 6.5

10 ..

51) The reason the rings of Saturn exist is because A) the ring material lies within the Roche limit of Saturn.

B) the gravitational influence of Titan confines them to those orbits.

C) the eruptions of Mimas' volcanoes are keeping them supplied with ice.

D) there has not been sufficient time for the ring particles to form a moon.

E) Saturn's rapid rotation is spinning material away from its equator, out into space.

Answer: A Diff: 1 Section Ref: 6.6 52) A moon that goes inside the Roche Limit will A) get heated by the strong magnetic fields.

B) collide with a major satellite.

C) escape its planet's gravity.

D) be torn apart by the planet's tidal forces.

E) become a planet.

Answer: A Diff: 2 Section Ref: 6.6 53) The Roche limit is the point at which A) the mass of an object classifies it as a moon.

B) a moon orbiting a planet experiences synchronous rotation.

C) the external tidal forces on an object are strong enough to be felt by the object.

D) the external tidal forces on an object become greater than the internal forces that hold it together.

E) the internal forces that hold an object together weaken so that the object falls apart.

Answer: D Diff: 1 Section Ref: 6.6 54) Which of the following played the most important role in the ring's formation?

A) Saturn's differential rotation B) Saturn's Roche limit C) Saturn's distance from the Sun D) Debris from volcanoes on Mimas E) Tidal resonance with Titan Answer: B Diff: 1 Section Ref: 6.6

11 ..

55) One of the discoveries made by the Voyager probes while near Jupiter was A) Io has a featureless surface that never changes.

B) a thin ring of dust around the equator.

C) the absence of a magnetic field around the giant planet.

D) that the Great Red Spot is uniform and featureless.

E) each of the four large moons produces a strong magnetic field.

Answer: B Diff: 2 Section Ref: 6.6 56) The rings of Uranus and Neptune are found A) by the Hubble Space Telescope.

B) above their equators.

C) in the ecliptic plane.

D) outside the Roche limit.

E) all of the above Answer: B Diff: 2 Section Ref: 6.6 57) The rings of Neptune A) were confirmed by the Voyager 2 in 1989.

B) number five, with three narrow, two more diffuse.

C) all lie within Neptune's Roche Limit.

D) often appear as clumpy ring arcs, rather than complete and symmetrical.

E) All of these are correct.

Answer: E Diff: 2 Section Ref: 6.6 58) The orbits of most asteroids A) lie beyond Neptune.

B) lie entirely beyond the orbit of Mars.

C) cross the orbit of Mars.

D) cross the orbit of Earth.

E) cross the orbits of all four terrestrial planets.

Answer: B Diff: 1 Section Ref: 6.7

12 ..

59) What is the defining property of the Trojan asteroids?

A) Their orbital periods are exactly one year, like ours.

B) They have orbits that cross the orbit of the Earth, but not that of Venus.

C) They have orbits at the distance of Jupiter and 60 degrees ahead of or behind it.

D) They have orbits between Saturn and Uranus.

E) Like Pluto, they are in a 3:2 resonance with Neptune.

Answer: C Diff: 2 Section Ref: 6.7 60) The orbits of most comets A) are like the planets, fairly circular and in the ecliptic plane.

B) lie almost entirely beyond the orbit of Neptune.

C) have perihelions within the orbits of Mercury.

D) go no farther out than Pluto, then return to the sun again.

E) are shorter than the 76 year period for Comet Halley.

Answer: B Diff: 1 Section Ref: 6.7 61) What are comets made of?

A) Silicates and rocky dust B) Metallic dust particles C) Dark colored complex hydrocarbons D) Methane, ammonia, and water ice E) All of the above Answer: E Diff: 1 Section Ref: 6.7 62) The Oort Cloud is thought to be A) the cloud of gas and dust from which our solar system formed.

B) a cloud of debris that occasionally encounters the Earth, causing a meteor shower.

C) the spherical cloud of comets and some larger icy bodies surrounding the outer solar system.

D) a cloud of asteroids moving between the orbits of Mars and Jupiter.

E) the material in the ecliptic plane that creates the zodiacal light.

Answer: C Diff: 2 Section Ref: 6.7

13 ..

63) The nucleus, or main solid body, of a comet has a typical size of A) a few centimeters.

B) a few meters.

C) a few kilometers.

D) a few hundred kilometers.

E) a few thousand kilometers.

Answer: C Diff: 2 Section Ref: 6.7 64) Long period comets are thought to reside mainly in the A) asteroid belt.

B) Kirkwood gaps.

C) Kuiper Belt.

D) Oort Cloud.

E) Interstellar Medium.

Answer: D Diff: 2 Section Ref: 6.7 65) The tail of a comet always points A) toward the Sun and disappears at perihelion.

B) toward Earth and never varies.

C) away from the Sun and disappears at perihelion.

D) away from the Sun and becomes longest and brightest at perihelion.

E) in the direction of the comet's motion.

Answer: D Diff: 1 Section Ref: 6.7 66) The Kuiper Belt objects have orbits that A) carry them thousands of AU beyond the Sun. B) stay out just beyond Neptune and close to the ecliptic.

C) stay sixty degrees ahead of or behind Jupiter.

D) cross the orbit of Mars at perihelion.

E) cross the orbit of Earth at perihelion.

Answer: B Diff: 3 Section Ref: 6.7

14 ..

67) From its orbit, we now recognize Pluto as one of the largest members of the A) moons of Neptune.

B) asteroid belt.

C) Kuiper Belt.

D) Oort Cloud.

E) Zodiacal Belt.

Answer: C Diff: 1 Section Ref: 6.8 68) Pluto's bulk density is A) 3,400 kg/m3, comparable to our Moon's.

B) 2,100 kg/m3, similar to Callisto's mix of rock and ice.

C) 1,200 kg/m3, like Mimas, made of almost pure ice.

D) 700 kg/m3, like Saturn a mix of hydrogen and helium slush.

E) 400 kg/m3, like Comet Halley's nucleus, a ice ball with many gas pockets.

Answer: B Diff: 2 Section Ref: 6.8 69) Pluto was discovered in A) ancient times.

B) 1789.

C) 1859.

D) 1930.

E) 1992.

Answer: D Diff: 2 Section Ref: 6.8 70) Pluto's density is most similar to A) the terrestrial planets.

B) the jovian planets.

C) moons of the jovian planets.

D) Mercury, but nor Venus, Earth, or Mars.

E) Saturn, but not Jupiter, Uranus, or Neptune.

Answer: C Diff: 2 Section Ref: 6.8

15 ..

71) When a formal definition of a planet in the solar system was adopted, Pluto was reclassified as a dwarf planet. What characteristic of planets does not describe Pluto?

A) Planets orbit the sun.

B) Planets are approximately spherical.

C) Planets have cleared the neighborhood around their orbit.

D) Planets orbit in ellipses with low eccentricity.

E) Planets orbit in or very near the ecliptic plane.

Answer: C Diff: 1 Section Ref: 6.8 72) The large moons of Jupiter have low densities suggesting compositions that are a mixture of rocky materials and ________.

Answer: liquid water and/or ices Diff: 2 Section Ref: 6.1 73) Except for Io, the other three Galilean satellites have periods of rotation and revolution that are ________.

Answer: equal Diff: 1 Section Ref: 6.1 74) Io's "pizza pie" colors come from eruptions of ________ and its compounds.

Answer: sulfur Diff: 2 Section Ref: 6.2 75) Io's volcanoes contribute material to a ________ around the planet Jupiter's equator.

Answer: ring or torus-shaped cloud Diff: 3 Section Ref: 6.2 76) The Galileo spacecraft showed that volcanic features on Io could change in ________.

Answer: weeks Diff: 2 Section Ref: 6.2 77) The moon with an atmosphere denser than ours is ________.

Answer: Titan Diff: 1 Section Ref: 6.3

16 ..

78) Titan has oceans made chiefly of liquid ________, along with smaller amounts of methane and propane.

Answer: ethane Diff: 1 Section Ref: 6.3 79) At Titan, the weather is driven by phase changes of ________ gas into liquid or solid forms.

Answer: methane Diff: 2 Section Ref: 6.3 80) Neptune's large moon ________ is the only large satellite known in a retrograde orbit.

Answer: Triton Diff: 2 Section Ref: 6.3 81) The cratered surfaces of Saturn's moons may look like our moons, but in reality they are made chiefly of ________.

Answer: ice Diff: 1 Section Ref: 6.4 82) The moons of Uranus are darker than those of Saturn, due to ________.

Answer: radiation darkening Diff: 2 Section Ref: 6.4 83) Compared to the other rings, those of ________ are the most irregular, with clumps of material and ring arcs.

Answer: Neptune Diff: 2 Section Ref: 6.6 84) The asteroid belt is believed to be debris left over from the age of formation of the solar system; the tidal effects of ________ probably prevented formation of a major planet there.

Answer: Jupiter Diff: 1 Section Ref: 6.7 85) Rocky debris larger than 100 meters in diameter seen to be orbiting the sun are called ________.

Answer: asteroids Diff: 1 Section Ref: 6.7

17 ..

86) Small icy bodies in the solar system which travel about the Sun in highly eccentric orbits and come from all directions are ________.

Answer: comets Diff: 1 Section Ref: 6.7 87) Discovered in the 1990s, the ________ is a vaster, darker version of the more famed asteroid belt between Mars and Jupiter.

Answer: Kuiper Belt Diff: 1 Section Ref: 6.7 88) We now recognize that the largest Kuiper Belt Object could be ________, discovered almost a century ago.

Answer: Pluto Diff: 1 Section Ref: 6.8 89) Discovered in the 1990s, the ________ is a vaster, darker version of the more famed asteroid belt between Mars and Jupiter.

Answer: Kuiper Belt Diff: 1 Section Ref: 6.8 90) Which of the Galilean Moons may have a subsurface layer of liquid water?

Answer: Europa and Ganymede Diff: 2 Section Ref: 6.1 91) What is the origin of Io's volcanism?

Answer: A tidal tug-of-war between Io, Jupiter, and Europa (the next moon out).

Diff: 2 Section Ref: 6.2 92) Why is Titan considered so interesting?

Answer: It has a thick atmosphere which may be similar to that on Earth in ancient times.

Diff: 2 Section Ref: 6.3 93) Volcanic eruptions on one satellite of the outermost jovian planets, Neptune and Uranus, have been photographed by spacecraft. Which satellite, and what is erupting from this type of volcanism?

Answer: Triton is erupting liquid nitrogen.

Diff: 2 Section Ref: 6.3

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94) Explain radiation darkening.

Answer: Solar radiation and high-energy particles break up surface molecules, leading to chemical reactions that slowly form a layer of dark, organic material.

Diff: 2 Section Ref: 6.4 95) Why are Saturn's rings much brighter than any other jovian's ring system?

Answer: They are made of bright, shiny, fairly new water ice with a high reflectivity, and a lot of it.

Diff: 1 Section Ref: 6.5 96) Why do Saturn's rings exist?

Answer: The material in the rings lies inside Saturn's Roche limit, which prevents the debris from condensing into a moon.

Diff: 1 Section Ref: 6.6 97) What is a planet's Roche limit?

Answer: The distance from a planet inside which a moon will be tidally torn apart.

Diff: 2 Section Ref: 6.6 98) Define Trojan asteroids.

Answer: Asteroids found sharing the orbit of Jupiter but 60 degrees ahead of or behind it at the L4 or L5 Lagrange points.

Diff: 2 Section Ref: 6.7 99) Contrast the internal structures of the four Galilean moons. How are their internal differences reflected in the nature of their surfaces and other factors like their mean densities?

Answer: Io: Molten to core, high density (3600 kg/m3), abundance of sulfur. Surface very active. Europa: Water ice crust over liquid water ocean over rocky core. Lower density than Io (3000 kg/m3). Surface somewhat active, with only a few fairly new impact craters. Ganymede, Callisto: Water ice, frozen. Low density (1900 kg/m3). Surface dead and inactive, with many craters.

Diff: 3 Section Ref: 6.1 100) The average density of the planet Jupiter has been known for hundreds of years, but the densities of its Galilean moons were only determined accurately from data obtained during the Voyager by-pass missions. Why? Answer: The density of an object is its mass divided by its volume. Although the sizes of the Galilean moons have been known approximately for some time, their masses have not. The Voyager missions helped determine these masses and, therefore, their densities.

Diff: 3 Section Ref: 6.1 19 ..

101) In what two ways is Titan's atmosphere like our own? Now name two differences.

Answer: Like the earth's, Titan's atmosphere is made chiefly of nitrogen, and it is at about the same barometric pressure as the earth at both surfaces. However, it is much colder, lacks any substantial oxygen, and its clouds are made of methane and other hydrocarbons, not water droplets like ours.

Diff: 2 Section Ref: 6.3 102) Neptune's moon Triton appears to have a nearly uncratered surface. Explain.

Answer: There has been a large amount of surface activity that has obliterated the craters from much of Triton's surface. These are fissures, nitrogen geysers, and large frozen water ice lakes that are indicative of this activity. This probably is generated by the tidal stresses of its retrograde orbit close to Neptune.

Diff: 3 Section Ref: 6.3 103) What will happen to Triton in the distant future, based on its present orbit?

Answer: Due to its retrograde orbit, it will spiral into Neptune and be torn apart into a ring when it reaches Neptune's Roche Limit. Its tidal forces will probably also heat up Neptune still more; it is already warmer than Uranus.

Diff: 3 Section Ref: 6.3 104) How is Mimas responsible for the Cassini Division?

Answer: Mimas has an orbital period precisely twice that of matter in the Cassini Division. As such, it exerts a regular tug on particles there, pulling them to an orbit further out. The particles stay in the outer orbit once they collide with other particles and lose excess energy.

Diff: 2 Section Ref: 6.5 105) Where is Jupiter's ring located? What is it made of, and why?

Answer: Between the top of Jupiter's clouds and the orbit of the closest moon; the ring also orbits just above Jupiter's equator. It may be in part debris from Io's violent volcanoes, and dust from the breakup of the tiny moons Tethys and Adrastea, both so close to Jupiter they are under great tidal stress. Ice particles like Saturn's rings cannot exist to close to hot Jupiter, which gives back into space twice the energy it gets from the Sun. Diff: 3 Section Ref: 6.6

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106) How were the rings of Uranus discovered? How have they since been imaged from Earth better?

Answer: Uranus passed in front of a star, and the star's light fluctuated before and after the occultation. These rapid changes were mapped by photoelectric photometry to map the rings.

Later observations found them brighter in the infrared, for as the dark material absorbs sunlight, the absorbed energy heats up the rings particles to the point that in the infrared, they are hotter than the planet's surface clouds.

Diff: 3 Section Ref: 6.6 107) Nearly every aspect of astronomy is related in some way to the existence of gravity and to the motions which are responsible for a balance against gravity. How does this balance play a role for the miscellaneous objects of the solar system (i.e., the asteroids and comets)? How can some aspect of this be used as a tool to determine masses in the solar system?

Answer: Asteroids and comets all orbit the Sun, some with highly eccentric orbits. Some comets have periods of millions of years. Gravity acting on and between comets and asteroids can be used to determine their masses and the masses of bodies affecting them.

Diff: 2 Section Ref: 6.7 108) Why were the mass and density of Pluto unknown until Charon was found?

Answer: Pluto is so distant that its disk was not resolved well, and it had no discernable gravitational influence on Uranus and Neptune (Lowell's prediction was just luck). But Charon's orbit let us find the mass of both objects, and the series of eclipses allowed us to calculate the sizes of both bodies with great accuracy.

Diff: 3 Section Ref: 6.8

21 ..

Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 7 Formation of Planetary Systems 1) Any model of solar system formation must explain why terrestrial planets and jovian planets formed differently.

Answer: TRUE Diff: 1 Section Ref: 7.1 2) Any model of solar system formation must explain why the planets revolve in the same direction as the Sun rotates.

Answer: TRUE Diff: 1 Section Ref: 7.1 3) Any model of solar system formation must explain why every planet is relatively isolated in space.

Answer: TRUE Diff: 1 Section Ref: 7.1 4) Any model of solar system formation must explain why comets come from the Oort Cloud, with orbits very different from the planets, asteroids, and Kuiper Belt Objects.

Answer: TRUE Diff: 1 Section Ref: 7.1 5) All planets revolve around the Sun counterclockwise, and most also rotate on their axis counterclockwise.

Answer: TRUE Diff: 1 Section Ref: 7.1 6) The asteroids are very young and appear to be made from the same material.

Answer: FALSE Diff: 2 Section Ref: 7.1 7) While most large moons orbit counterclockwise above their planets' equators, the smaller moons often show eccentric or even retrograde orbits, suggesting capture.

Answer: TRUE Diff: 2 Section Ref: 7.1

1 ..

8) The Kuiper Belt is a collection of asteroid-sized icy bodies orbiting the Sun beyond the orbit of Neptune.

Answer: TRUE Diff: 2 Section Ref: 7.1 9) Different temperatures within the solar nebula ultimately determined the compositions of the planets and their moons.

Answer: TRUE Diff: 1 Section Ref: 7.2 10) Jupiter and the other jovian planets may have formed significantly closer to the Sun than their current orbits.

Answer: FALSE Diff: 2 Section Ref: 7.3 11) Most extrasolar planets are hot Jupiters, discovered in the infrared by the Spitzer Space telescope.

Answer: FALSE Diff: 1 Section Ref: 7.5 12) We now know of over 100 jovian exoplanets, but no terrestrial planets around other stars similar to the Sun. Answer: FALSE Diff: 2 Section Ref: 7.5 13) Around other suns, we have found Jupiters where Mercury should be.

Answer: TRUE Diff: 2 Section Ref: 7.5 14) None of the other stars yet studied has more than one planet orbiting it.

Answer: FALSE Diff: 2 Section Ref: 7.5 15) Stars with multiple planets orbiting them are expected to be rare.

Answer: FALSE Diff: 1 Section Ref: 7.5

2 ..

16) Concerning our solar nebula theory, the presence of so many "hot Jupiters" gives us problems with how they can form that close to their star.

Answer: TRUE Diff: 2 Section Ref: 7.5 17) Most hot Jupiters are thought to have formed in the orbits they have been discovered.

Answer: FALSE Diff: 1 Section Ref: 7.5 18) It is expected that most of the planet candidates found by the Kepler mission will eventually be confirmed.

Answer: TRUE Diff: 2 Section Ref: 7.5 19) Super-Earths are earthlike planets where life is possible.

Answer: FALSE Diff: 2 Section Ref: 7.5 20) As the solar nebula contracts due to gravitation, the cloud A) spins faster.

B) expands.

C) becomes more spherical in shape.

D) changes direction of motion.

E) begins to cool.

Answer: A Diff: 3 Section Ref: 7.1 21) The Kuiper Belt is found where in the solar system?

A) Among the orbits of the terrestrial planets B) Beyond the orbit of Neptune C) Between the orbits of Mars and Jupiter D) Between the orbits of Jupiter and Uranus E) Sixty degrees ahead or behind Jupiter Answer: B Diff: 1 Section Ref: 7.1

3 ..

22) Which of these is NOT a characteristic of the solar nebula theory?

A) The ecliptic is the equator for the Sun. B) All the planets should follow the ecliptic plane.

C) All the planets should orbit the Sun counterclockwise.

D) Larger planets should form closer to their star, where there is more debris.

E) Planets should rotate counterclockwise as well.

Answer: D Diff: 2 Section Ref: 7.1 23) What might have made the original solar nebula begin to contract?

A) The Big Bang B) The formation of our arm of the Milky Way C) The shock wave from a nearby exploding star D) Interstellar magnetism generated by pulsars E) The large amount of angular momentum in the nebula Answer: C Diff: 2 Section Ref: 7.1 24) A successful theory of the formation of the solar system must explain A) that all planets rotate in a prograde sense.

B) that all planets have elliptical orbits with high eccentricities.

C) the existence of the asteroid belt between Jupiter and Neptune.

D) that the inner planets have more hydrogen and helium in their atmospheres than do the outer planets.

E) all observed properties of the solar system.

Answer: E Diff: 2 Section Ref: 7.1 25) Planetary orbits A) are evenly spaced throughout the solar system.

B) are highly inclined to the ecliptic.

C) are almost circular, with low eccentricities.

D) have the Sun at their exact center.

E) are spaced more closely together as they get further from the Sun. Answer: C Diff: 2 Section Ref: 7.1

4 ..

26) What happens when a solar nebula contracts?

A) It flattens out.

B) It spins faster.

C) It heats up.

D) All of the above E) None of the above Answer: D Diff: 1 Section Ref: 7.1 27) In light of modern solar system theory, why do the orbits of the planets all lie in the same plane?

A) The Sun's gravity forced them into these orbits.

B) The angular momentum of the solar system was kept to a minimum this way.

C) The early solar nebula flattened into a disk.

D) Comets would have wiped out any not in this protected plane.

E) This happened purely by chance.

Answer: C Diff: 1 Section Ref: 7.1 28) Conservation of angular momentum means that a spinning body tends to A) fly apart.

B) slow down.

C) wobble into an eccentric orbit.

D) gravitationally collapse.

E) keep spinning.

Answer: E Diff: 1 Section Ref: 7.1 29) Dust is an important part of the nebular theory of solar system formation because dust is needed to explain A) how the inner planets came to be rocky bodies.

B) how the outer planets came to be gaseous bodies.

C) how the initial cloud cooled enough to collapse.

D) how the initial cloud heated as it contracted.

E) why the icy bodies are located so far from the Sun. Answer: A Diff: 2 Section Ref: 7.1

5 ..

30) As a rotating gas cloud contracts, it spins A) faster due to an increase in angular momentum.

B) slower due to a decrease in angular momentum.

C) at a constant rate.

D) faster due to conservation of angular momentum.

E) slower due to conservation of angular momentum.

Answer: D Diff: 3 Section Ref: 7.1 31) As the solar nebula contracts it A) flattens out into the ecliptic plane around the Sun's poles.

B) spins faster due to conservation of angular momentum.

C) cools due to condensation.

D) loses angular momentum.

E) reverses it direction of rotation.

Answer: B Diff: 2 Section Ref: 7.1 32) What is the role of irregularities in the solar system in terms of theories of its origin?

A) They are too minor to play a role; astronomers ignore them.

B) They introduce a need for flexibility in theories of the solar system's origin.

C) Theories of the solar system are entirely based on the many irregularities found among the planets and moons.

D) The solar system has no irregularities; it is perfectly regular and orderly.

E) The solar system is chaotic, with irregularities the rule.

Answer: B Diff: 2 Section Ref: 7.2 33) Which objects in the solar system have been least modified since the formation of the solar system?

A) Asteroids B) Kuiper Belt objects C) Meteoroids D) Terrestrial planets E) Jovian moons Answer: B Diff: 3 Section Ref: 7.2

6 ..

34) The jovian planets A) all lie less than 5 AU from the Sun. B) all have rings around their equators.

C) all spin slower than the Earth.

D) have satellite systems with less than 4 moons.

E) are all much more dense than any of the terrestrials planets.

Answer: B Diff: 3 Section Ref: 7.2 35) What factor caused different planets to form out of different types of material?

A) The angular momentum of the forming planet; faster rotating planets lost the lightest elements.

B) The quantity of dust particles in the solar nebula; more dust caused some planets to contain heavier elements.

C) The variation in temperature throughout the solar nebula; the higher the temperature, the lower the percentage of light elements in the forming planet.

D) The angular momentum of the solar nebula pushed the heavy elements towards the outer regions of the nebula.

E) The innate variation of chemical composition of the original nebula; the outer parts of the nebula contained a greater abundance of heavy elements.

Answer: C Diff: 2 Section Ref: 7.2 36) What is the process of accretion?

A) The separation of materials in a protoplanet by density, with dense material in core B) Growth of an object by the accumulation of matter C) The breakup of large objects by violent collisions with other similar-sized objects D) The period of time during which the Sun swept away all the excess material in the solar nebula E) The process by which the solar nebula became heated during its collapse Answer: B Diff: 1 Section Ref: 7.2 37) In the conventional scenario, during phase of planet formation caused the jovian planets to form?

A) Core-accretion B) Fragmentation C) Differentiation D) Collision E) Condensation Answer: A Diff: 1 Section Ref: 7.3 7 ..

38) An alternative to the core-accretion theory that explains the formation of the jovian planets is the A) differentiation theory.

B) collision theory.

C) gravitational instability theory.

D) Big Bang theory.

E) nebular contraction theory.

Answer: C Diff: 2 Section Ref: 7.3 39) The moons of the jovian planets formed by which two processes?

A) Accretion and collisions B) Capture and collisions C) Collisions and differentiation D) Accretion and capture E) Differentiation and capture Answer: D Diff: 2 Section Ref: 7.3 40) As a result of the ejection of planetesimals into the Oort Cloud, simulations indicate that Uranus and Neptune moved A) closer to the Sun. B) further from the Sun. C) along their orbits at a different rate.

D) from the inner solar system to the outer solar system.

E) from the outer solar system to the inner solar system.

Answer: B Diff: 2 Section Ref: 7.3 41) According to the planetary migration model, the jovian planets are thought to have formed A) in the orbit where they are now.

B) further from the Sun than they are now.

C) in another solar system.

D) closer to the Sun than they are now.

E) none of the above.

Answer: B Diff: 2 Section Ref: 7.3

8 ..

42) The Oort Cloud is believed to have been formed by A) planetesimals that were flung far from the Sun in gravitational encounters with the jovian planets.

B) icy bodies formed between stars that have been captured by our solar system's gravity.

C) moons that escaped from the jovian planets.

D) debris from an icy planet that broke apart early in the solar system's history.

E) debris from impacts of planetesimals, asteroids and comets with the jovian planets.

Answer: A Diff: 2 Section Ref: 7.3 43) The Kuiper Belt is A) another name for the Asteroid Belt.

B) a band of icy planetesimals found beyond Neptune's orbit.

C) where all comets come from.

D) the name given to icy bodies found between Jupiter and Saturn.

E) the name given to icy bodies found between Mars and Jupiter.

Answer: B Diff: 1 Section Ref: 7.3 44) When was the first confirmed exoplanet discovered?

A) Shortly after the invention of the telescope, in the early 1600s B) In prehistoric times C) Around 350 BC, by the Ancient Greeks D) Early in the 21st century E) Near the end of the 20th century Answer: E Diff: 2 Section Ref: 7.4 45) The Doppler radial velocity technique works best for A) planets whose orbits are along are line of sight.

B) planets whose orbits are perpendicular to our line of sight.

C) planets whose orbits are nearly circular.

D) planets whose orbits are very eccentric.

Answer: A Diff: 2 Section Ref: 7.4

9 ..

46) When looking for the "Doppler Wobble" (radial velocity changes detected due to Doppler shifts), which mass combination is most likely to be detected?

A) High mass star, high mass planet B) High mass star, low mass planet C) Low mass star, high mass planet D) Low mass star, low mass planet E) A high mass planet; the mass of the star is irrelevant.

Answer: C Diff: 1 Section Ref: 7.4 47) The Kepler mission uses which technique to detect planet candidates?

A) Radial velocity measurements B) Direct imaging C) Measurements of transverse motion D) Planetary transits Answer: D Diff: 1 Section Ref: 7.4 48) Which statement about extrasolar planets found to date is TRUE? A) All are terrestrials, comparable in size to Earth.

B) Few are found by Doppler shifts of their stars, due to their gravity.

C) All lie more than 2 AU from their star.

D) Most have orbital periods of more than a year.

E) Some are so close to their stars that their periods are just a few days.

Answer: E Diff: 2 Section Ref: 7.5 49) Which molecule has not yet been detected in the atmospheres of exoplanets?

A) Methane B) Carbon dioxide C) Oxygen D) Water Answer: C Diff: 2 Section Ref: 7.5

10 ..

50) Planets found in the habitable zone of other stars A) are all rocky planets, like the terrestrial planets in our solar system.

B) are all jovian planets.

C) include some Earths and super-Earths.

D) include hot Jupiters.

E) have been demonstrated to be barren of all life.

Answer: C Diff: 2 Section Ref: 7.5 51) Most of first extrasolar planets found were detected by A) noting the drop in the star's light as the planet transits its disk.

B) imaging them with the HST in the infrared, where they are easier to stop.

C) noting the Doppler shifts of the star as the planet orbits it from side to side.

D) receiving radio transmissions from them, much like Jupiter emits.

E) detecting the oxygen in their atmospheres spectroscopically.

Answer: C Diff: 2 Section Ref: 7.5 52) Super-earths are A) planets that are most earthlike, likely to harbor life.

B) planets that are a few times the mass of the Earth.

C) planets that have earthlike masses, but orbit much closer to their star than the Earth does to the Sun. D) any rocky (or terrestrial) planet.

E) Earth-mass planets that are much lower in density than the Earth, giving them larger radii.

Answer: C Diff: 1 Section Ref: 7.5 53) Most extrasolar Neptunes and Jupiters found to date have A) orbits very close to their parent stars, making them hot Neptunes and hot Jupiters.

B) orbits that are more eccentric than those of planets in our solar system, with eccentricities greater than 0.1 C) orbits that are less eccentric than those of planets in our solar system, with eccentricities less than 0.01.

D) much larger orbits than the jovian planets in our solar system.

Answer: B Diff: 2 Section Ref: 7.5

11 ..

54) When we are lucky enough to see an extra-solar planet transit its star A) It will cause the star to vanish for several hours.

B) We can by the drop in light find the planet's size, mass, and density.

C) We can determine what elements are in its atmosphere.

D) We can determine its shape.

E) We can be certain it is a terrestrial, not a jovian.

Answer: B Diff: 2 Section Ref: 7.5 55) In the process of planetary formation, when would the inward migration of Jupiters have been most likely?

A) Shortly after all of the planets had finished forming B) Just after the system was cleared of the remaining gas C) Before these planets had grown to full size D) After these planets had reached full size, but before terrestrial planets had finished forming E) At least hundreds of millions of years after planetary formation ended Answer: D Diff: 2 Section Ref: 7.6 56) In the currently accepted theory for the formation of the solar system, the planets and other minor bodies and the ________ formed at about the same time.

Answer: Sun Diff: 1 Section Ref: 7.1 57) In general, the surfaces of the planets will be ________ than the age of the solar system.

Answer: younger Diff: 1 Section Ref: 7.1 58) While all planet orbits are ellipses, the orbits of the eight large planets are relatively ________.

Answer: circular Diff: 2 Section Ref: 7.1 59) The Kuiper Belt is located beyond the orbit of ________.

Answer: Neptune.

Diff: 1 Section Ref: 7.1

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60) The ________ theory describes the origin of the planets as having been formed by accretion of small particles into progressively larger and larger bodies.

Answer: condensation Diff: 1 Section Ref: 7.2 61) The chemical composition differences between the planets are basically the result of the fact that different elements condense out of gas at different ________.

Answer: temperatures.

Diff: 1 Section Ref: 7.2 62) Comets that we can see originate in the ________ and ________.

Answer: Kuiper Belt and Oort Cloud Diff: 2 Section Ref: 7.3 63) The Kepler mission uses the ________ technique to detect exoplanets.

Answer: transit Diff: 2 Section Ref: 7.4 64) The radial velocity method is less likely to detect low mass planets than high mass planets because low mass planets cause smaller ________ fluctuations.

Answer: velocity Diff: 1 Section Ref: 7.4 65) Hot jupiters have ________ period orbits.

Answer: short Diff: 1 Section Ref: 7.5 66) The ________ around a star is the region where liquid water could exist on a planet.

Answer: habitable zone Diff: 1 Section Ref: 7.6 67) Name three properties of the solar nebula still seen in planet orbits.

Answer: The planets still orbit in the common counter clockwise direction. This was the direction of the condensing nebula's rotation. The orbits are almost circular, as the nebula formed in concentric rings. All planets move close to the ecliptic, the plane in which the condensing disk flattened out around the Sun's equator.

Diff: 2 Section Ref: 7.1

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68) What is the role of dust in the condensation theory?

Answer: Dust provides the condensation nuclei around which accretion can occur.

Diff: 2 Section Ref: 7.1 69) What support for the solar nebula theory has come from observations of nearby young stars?

Answer: Many show dusty disks, with large infrared excesses, forming around the stars' equators as the stars condense. In some cases, these disks are seen as dark profiles in front of the star, such as in the Orion Nebula.

Diff: 2 Section Ref: 7.1 70) Why do the present methods of finding extrasolar planets (Doppler measurement and planetary transits) not favor finding solar systems like ours?

Answer: Doppler shifts are greatest for rapidly moving stars, where their planets are moving very close to them and with periods of much less than a year. Only Jovian planets will have the mass needed to exert detectible pulls such as this also.

Diff: 2 Section Ref: 7.4 71) Explain how the Doppler Effect has been used to detect invisible planets orbiting other Sunlike stars.

Answer: The Jupiter-like planets are massive enough to pull their star slightly off course as they orbit from one side to the other, producing a cycle of red and blue shifts that allow us to deduce that the planet is present, and how long it takes to orbit its star.

Diff: 3 Section Ref: 7.4 72) Why do instruments that are looking for transiting planets need to look for very small brightness changes?

Answer: Because a transiting planet blocks only a tiny fraction of the star's surface from our view.

Diff: 1 Section Ref: 7.4 73) Extrasolar planets are placed in groups by their approximate masses. What are four of these classes?

Answer: Planets above about 2 times the mass of Neptune are Jupiters. Planets less massive than this, down to about half the mass of Neptune are Neptunes. Super-Earths are less massive than Neptunes down to about twice the mass of Earth. Earths are planets less massive than that.

Diff: 2 Section Ref: 7.5

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74) Why are infrared observations useful when observing extrasolar planets?

Answer: Because planets radiate mostly infrared radiation, it is possible to distinguish this from the parent star's light. This allows some spectral analysis of the atmospheres, letting us know of some molecules and atoms in planetary atmospheres, such as carbon dioxide, methane, hydrogen and sodium. In a few cases, water vapor has been detected, which is of particular interest.

Diff: 3 Section Ref: 7.5 75) What is the most important consideration in the "habitable zone" of a planetary system?

Answer: The distance from its star and temperature of the planet's surface to allow for formation of liquid water for life to evolve in.

Diff: 2 Section Ref: 7.6 76) Explain the effect angular momentum has on a gas cloud as it contracts.

Answer: Angular momentum must be conserved. As the cloud contracts the rotating mass of gas is closer to its axis. In order for the angular momentum to remain the same, the cloud must spin faster, much as an ice skater spins faster when she brings her arms close to her body.

Diff: 2 Section Ref: 7.1 77) What are the properties of the Sun that any theory of the origin of the solar system must explain?

Answer: The Sun contains most of the mass of the solar system. It also has a slow rotation. Its age is consistent with the age of the solar system. The solar equator corresponds to the ecliptic.

Diff: 2 Section Ref: 7.1 78) What are the chemical and physical properties of the solar system that any theory of its origin must explain?

Answer: The inner planets have high densities, moderate atmospheres, and a mostly rocky composition. The outer planets have low densities, thick atmospheres, and a composition of mostly hydrogen and helium. The asteroids are composed of primitive, unevolved material unlike planets and the comets are icy objects that have also remained unchanged since the formation of the solar system.

Diff: 3 Section Ref: 7.1 79) Explain the stage in which the solar system formed pretty much in a plane.

Answer: The flat shape of the solar system is explained by the contraction of a slowly spinning cloud in the solar nebula theory.

Diff: 1 Section Ref: 7.1

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80) Describe how the observable properties of the solar system are related to its process of formation.

Answer: All the orbital and rotational motions can be explained as preserving the original rotation of the nebula from which the solar system formed. Accretion explains planetary isolation. Temperature differences explain differentiation. Asteroids and comets are left over debris. And irregularities can be explained by collisions during the planetesimal era.

Diff: 3 Section Ref: 7.2 81) Briefly outline the theory or hypothesis which best explains the origin of the solar system.

Answer: A large nebula began to collapse gravitationally. As it did so, it began to spin faster, and flattened into a disk. The disk heated up at the center, forming a protosun, and protoplanets began to accrete. Dust played an important role, both in helping radiate off excess heat, and in providing condensation nuclei for material to accrete onto. As protoplanets accreted, their gravity became significant and they became planetesimals. Planetesimals collided, forming planets.

Leftover debris became asteroids and comets. Large planets far from the Sun (the jovian planets) underwent their own similar process, and became miniature solar systems.

Diff: 2 Section Ref: 7.2 82) The processes of giant-planet migration and the formation of the Oort Cloud caused the Uranus to move both inward and outward in the solar system. Which motion was most important? Why? Answer: The giant-planet migration process was probably more significant in that it moved Uranus (as well as Neptune, Saturn, and Jupiter) significantly inward. The formation of the Oort Cloud caused Uranus to move just a few AU. Diff: 2 Section Ref: 7.3 83) Discuss the important features that allow space-based telescopes to search for transiting exoplanets.

Answer: They are exceptionally stable spacecraft, so that they can track small changes without shifting. They are position to continuously monitor a region of the sky; they are not limited to just Earth's nighttime for viewing. They have wide fields of view compared to most space telescopes, so they can monitor thousands of stars at once.

Diff: 3 Section Ref: 7.4 84) Describe two methods that have already been used to study extrasolar planets, and which one gives us the most information.

Answer: Extrasolar planets have been detected by the Doppler shifts they induce in the motion of their home stars, with the periodicity of these shifts telling us their periods. A second method used it to look for the cases where the planet transits its sun; the timing of this light loss gives us the actual masses, sizes, and even densities of the transiting planets.

Diff: 3 Section Ref: 7.4 16 ..

Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 8 The Sun 1) The Sun is a fairly normal star.

Answer: TRUE Diff: 1 Section Ref: 8.1 2) The photosphere is about 100 times the diameter of the Earth.

Answer: TRUE Diff: 1 Section Ref: 8.1 3) At very large distances from the Sun, its corona turns into the solar wind.

Answer: TRUE Diff: 1 Section Ref: 8.1 4) A sunbather on the clear day is receiving about 500 watts of solar power.

Answer: TRUE Diff: 2 Section Ref: 8.1 5) We know the Sun rotates differentially by observing sunspots; as with Jupiter the solar equator rotates the fastest.

Answer: TRUE Diff: 2 Section Ref: 8.1 6) The concept of hydrostatic equilibrium is critical to understanding how the Sun has remained stable long enough for live to evolve here.

Answer: TRUE Diff: 2 Section Ref: 8.2 7) Granulation is the most obvious proof of solar convective energy transport.

Answer: TRUE Diff: 2 Section Ref: 8.2 8) The energy of the Sun starts as radiation, but is actually transported to its surface by convection, where it is radiated off into space at last.

Answer: TRUE Diff: 2 Section Ref: 8.3

1 ..

9) The solar corona is much cooler than the Sun's surface; hence we must wait for a total solar eclipse to glimpse it with the naked eye.

Answer: FALSE Diff: 2 Section Ref: 8.4 10) The solar corona produces a lot more X-rays than it does visible light.

Answer: TRUE Diff: 2 Section Ref: 8.4 11) Large sunspots are larger than our whole planet.

Answer: TRUE Diff: 1 Section Ref: 8.5 12) Sunspots are only about 2,000 K cooler than the much brighter photosphere.

Answer: TRUE Diff: 2 Section Ref: 8.5 13) Prominences hanging off the limb of the Sun are the same as filaments seen in front of the disk.

Answer: TRUE Diff: 3 Section Ref: 8.6 14) Solar activity cannot disrupt communications on Earth.

Answer: FALSE Diff: 1 Section Ref: 8.6 15) The proton-proton chain requires a temperature of 100 million K to get started.

Answer: FALSE Diff: 2 Section Ref: 8.7 16) In the proton-proton cycle, you must first make deuterium, then helium.

Answer: TRUE Diff: 2 Section Ref: 8.7 17) In the proton-proton cycle, .007 of the mass ends up as energy, not helium.

Answer: TRUE Diff: 3 Section Ref: 8.7 2 ..

18) Both the gravitational and electromagnetic forces obey the inverse square law, and extend infinitely outward in their effects.

Answer: TRUE Diff: 2 Section Ref: 8.7 19) The Sun's luminosity is greatest when there are few or no sunspots on the Sun. Answer: FALSE Diff: 2 Section Ref: 8.8 20) The light we see from the Sun comes from which layer?

A) Troposphere B) Chromosphere C) Photosphere D) Ionosphere E) Corona Answer: C Diff: 1 Section Ref: 8.1 21) The temperature of the layer of gas that produces the visible light of the Sun is A) 3,500 K B) 5,800 K C) 12,300 K D) 300,000 K E) 15 million K Answer: B Diff: 1 Section Ref: 8.1 22) Why couldn't you stand on the Sun's surface?

A) The Sun has no surface at all...the photosphere is an illusion.

B) You could stand on the surface.

C) The Sun doesn't have a solid surface.

D) The Sun's surface is too highly magnetized for anything to survive there.

E) You could stand on it, if a sufficiently protective spacesuit could be designed.

Answer: C Diff: 1 Section Ref: 8.1

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23) The density of the Sun is most similar to which object?

A) Halley's Comet's nucleus B) The Earth C) Mercury D) The Moon E) Jupiter Answer: E Diff: 2 Section Ref: 8.1 24) The area in the Sun's atmosphere located above the chromosphere (1,500 - 10,000 km) where the temperature rises dramatically is called the A) photosphere.

B) corona.

C) solar wind.

D) transition zone.

E) convection zone.

Answer: D Diff: 2 Section Ref: 8.1 25) The luminosity of the Sun is a measure of A) the energy received by the Sun on Earth's surface.

B) the energy received by the Sun at the location of Earth.

C) the energy received by the Sun at any location in the solar system.

D) the energy emitted by the Sun at the photosphere.

E) the total energy emitted by the Sun in all directions.

Answer: E Diff: 2 Section Ref: 8.1 26) From inside out, which is in the correct order for the structure of the Sun? A) Core, convective zone, radiative zone B) Photosphere, radiative zone, corona C) Radiative zone, convective zone, chromosphere D) Core, chromosphere, photosphere E) Convective zone, radiative zone, granulation Answer: C Diff: 3 Section Ref: 8.1

4 ..

27) Hydrostatic equilibrium in our Sun is the balance between A) convection and radiation.

B) convection and gravitation.

C) pressure and radiation.

D) radiation and gravitation.

E) gravitation and pressure.

Answer: E Diff: 2 Section Ref: 8.2 28) The vibrations of the Sun reveal information about A) the temperature of the core of the Sun. B) the structure of the atmosphere of the Sun. C) the interior structure of the Sun. D) the production of energy in the Sun. E) the magnetic field of the Sun. Answer: C Diff: 2 Section Ref: 8.2

29) The above diagram indicates that A) the Sun is most dense somewhere between its surface and its core.

B) the Sun is least dense somewhere between its surface and its core.

C) the Sun is more dense at its surface than at its core.

D) the Sun is more dense at its core than at its surface.

E) the Sun has about the same density throughout its interior.

Answer: D Diff: 2 Section Ref: 8.2

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30) The above diagram indicates that A) the Sun is hottest somewhere between its surface and its core.

B) the Sun is coolest somewhere between its surface and its core.

C) the Sun is hotter at its surface than at its core.

D) the Sun is hotter at its core than at its surface.

E) the Sun has about the same temperature throughout its interior.

Answer: A Diff: 2 Section Ref: 8.2 31) The outward pressure of hot gas in the Sun A) is balanced by the inward gravitational pressure.

B) is increasing the Sun's diameter.

C) is cooling the photosphere.

D) is responsible for variations in the sunspot cycle.

E) weakens the magnetic field.

Answer: A Diff: 3 Section Ref: 8.2 32) Studies by the Global Oscillations Network Group, along with satellite observations, indicate A) that the standard solar model requires substantial modification.

B) that all stars show the same kind of vibrations that our Sun does.

C) that there is an unknown energy transport mechanism in the Sun. D) that there is less convection in the Sun than predicted by the standard solar model.

E) that the standard solar model accurately models the observed solar vibrations.

Answer: E Diff: 2 Section Ref: 8.2

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33) What two energy transport mechanisms, in order from outside the core to the surface, is found in the Sun? A) Convection, conduction B) Fadiative diffusion, convection C) Conduction, radiative diffusion D) Fadiative diffusion, conduction E) Conduction, convection Answer: B Diff: 2 Section Ref: 8.3 34) By what mechanism does solar energy reach the Sun's photosphere from the layer just underneath it?

A) Differentiation B) Ionization C) Radiation D) Convection E) Conduction Answer: D Diff: 1 Section Ref: 8.3 35) What is the size of a typical granule or convection cell seen in the photosphere?

A) 10,000 km B) 1,000 km C) 100 km D) 10 km E) 1 km Answer: B Diff: 2 Section Ref: 8.3 36) The pattern of rising hot gas cells all over the photosphere is called A) filaments.

B) granulation.

C) sunspots.

D) convective projections.

E) prominences.

Answer: B Diff: 2 Section Ref: 8.3

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37) When the chromosphere can be seen during a solar eclipse, it appears A) invisible.

B) violet.

C) blue.

D) yellow.

E) red.

Answer: E Diff: 1 Section Ref: 8.4 38) From where does most of the solar wind flow?

A) Granules B) Sunspots C) Flares D) Prominences E) Coronal holes Answer: E Diff: 2 Section Ref: 8.4 39) What is it about the Sun's corona that astronomers don't understand?

A) No one knows why that part of the Sun's atmosphere does not drift away into space.

B) During total solar eclipses, the corona sometimes disappears from view.

C) The corona seems to absorb 2/3 of the neutrinos that pass through it.

D) The corona is much hotter than layers of the Sun that are closer to the solar interior.

E) The Sun's corona extends to the outer reaches of the solar system.

Answer: D Diff: 2 Section Ref: 8.4 40) When we glimpse the chromosphere at the start and end of totality, its color is A) green (the famous flash).

B) yellow, like the photosphere below it.

C) red, due to ionized hydrogen at lower pressure.

D) blue, due to the ionization of nitrogen by the magnetic fields.

E) white from the moonlight.

Answer: C Diff: 2 Section Ref: 8.4

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41) The percentage (by number of atoms) of the Sun that is hydrogen is about A) 91%.

B) 71%.

C) 27%.

D) 9%.

E) less than 1%.

Answer: A Diff: 2 Section Ref: 8.4 42) How long does the sunspot cycle last, on average?

A) Between 25 and 35 days B) 365.25 days C) About seven years D) About 11 years E) About 76 years Answer: D Diff: 1 Section Ref: 8.5 43) Visible sunspots lie in the A) chromosphere.

B) transition zone.

C) corona.

D) radiative zone.

E) granulation in the photosphere.

Answer: E Diff: 2 Section Ref: 8.5 44) As the Sun rotates, an individual sunspot can be tracked across its face. From eastern to western limb, this takes about A) 12 hours.

B) a week.

C) two weeks.

D) a month.

E) 5.5 years.

Answer: C Diff: 2 Section Ref: 8.5

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45) The most striking example of solar variability was the A) Dust Bowl drought of the 1930s.

B) Maunder Minimum from 1645-1715.

C) Sporer Minimum that doomed the Anasazi.

D) fall of Rome.

E) Joseph's seven lean years in the Old Testament.

Answer: B Diff: 2 Section Ref: 8.5 46) Sunspots A) are always found close to the Sun's poles.

B) come in pairs, representing the north and south magnetic fields.

C) were most numerous during the Maunder Minimum.

D) travel over the surface of the Sun from pole to pole.

E) are relatively constant in number every year.

Answer: B Diff: 2 Section Ref: 8.5 47) Sunspots are dark splotches on the Sun. Which statement is TRUE? A) They are hotter than the surrounding areas of the Sun. B) They are extremely cold objects, as cold as Pluto.

C) They are extremely hot, but cooler than the surrounding areas of the Sun. D) They are solid bodies floating on the surface of the Sun. E) They are associated with areas of very low magnetic fields.

Answer: C Diff: 2 Section Ref: 8.5 48) How would sunspots appear if you could magically remove them from the Sun? A) They would appear blue-white, like Sirius but brighter.

B) Because sunspots are dark spots, they would be invisible against the blackness of space.

C) They would shine bright orange in color, like Arcturus.

D) They would not appear any differently than on the surface of the Sun. E) They would shine only with reflected sunlight, appearing similar to Venus.

Answer: C Diff: 2 Section Ref: 8.5

10 ..

49) While observing the Sun, you note a large number of sunspots. What can you conclude?

A) The Sun is less luminous than usual.

B) This is a period of low solar activity.

C) Earth's climate will be unusually cold.

D) The Sun's rotation is slower than average.

E) There are likely to be an above average number of flares and prominences.

Answer: E Diff: 3 Section Ref: 8.5 50) The numbers of sunspots and their activity peak about every A) 36 days.

B) six months.

C) year.

D) eleven years.

E) 76 years.

Answer: D Diff: 1 Section Ref: 8.5 51) On the Sun, what takes approximately 22 years to happen?

A) The Sun takes that time to rotate on its axis.

B) The complete sunspot cycle, including magnetic field reversals.

C) Solar vibrations begin every 22 years.

D) Solar activities goes from its maximum to minimum.

E) The corona reaches its maximum temperature and ejects gas every 22 years.

Answer: B Diff: 2 Section Ref: 8.5 52) Loops of glowing hydrogen seen hanging over the solar limb during totality are A) solar rainbows.

B) haloes.

C) prominences.

D) filaments.

E) flares.

Answer: C Diff: 2 Section Ref: 8.6

11 ..

53) During a period of high solar activity, the corona A) disappears.

B) is more irregular.

C) cools almost to the temperature of the photosphere.

D) becomes smooth and even.

E) shrinks to half its normal size.

Answer: B Diff: 2 Section Ref: 8.6 54) Which of these are NOT associated with the active Sun? A) Sunspots B) Prominences C) Granulation D) Flares E) Aurora Answer: C Diff: 2 Section Ref: 8.6 55) Suppose a large flare is detected optically. How long until radio interference arrives?

A) Simultaneously B) 8.5 minutes later C) About 12 hours D) About four days E) No relation between the two Answer: A Diff: 3 Section Ref: 8.6 56) The critical temperature the core must reach for a star to shine by fusion is A) 5,800 K. B) 11,000 K. C) 127,000 K. D) 10 million K. E) 100 million K. Answer: D Diff: 2 Section Ref: 8.7

12 ..

57) In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happens to the "lost" mass?

A) It is recycled back into hydrogen.

B) It is ejected into space.

C) It is converted to energy.

D) It is transformed into electrons.

E) Conservation of mass dictates no mass can be lost.

Answer: C Diff: 2 Section Ref: 8.7 58) The primary source of the Sun's energy is A) oxidation of carbon in the core.

B) gravitational collapse of the helium coreward.

C) dark energy.

D) the strong force fusing hydrogen into helium.

E) the weak force creating energy from uranium decay.

Answer: D Diff: 2 Section Ref: 8.7 59) In the proton-proton cycle, the positron is A) massless.

B) a spin conservation particle.

C) an anti-electron.

D) the chief means energy reaches the photosphere.

E) intermediate between the proton and neutron in mass.

Answer: C Diff: 2 Section Ref: 8.7 60) What natural barrier tries to prevent two protons from combining?

A) Dark energy B) Antigravity C) Electromagnetic repulsion D) The weak nuclear force E) The strong nuclear force Answer: C Diff: 2 Section Ref: 8.7

13 ..

61) The critical temperature to initiate the proton-proton cycle in the cores of stars is A) 3,000 K. B) 5,800 K. C) 2,300,000 K. D) 10 million K. E) 100 million K. Answer: D Diff: 2 Section Ref: 8.7 62) Which is the net result of the proton-proton chain?

A) 4 protons = 1 helium 4 + a positron + a neutrino + gamma rays B) 2 protons = deuterium + a positron + an antineutrino + X-rays C) 4 protons = 2 heliums 2 + 2 positrons + ultraviolet radiation D) 4 protons = 1 helium 4 + 2 neutrinos + gamma rays E) 6 protons = 2 heliums + 3 positrons + 3 neutrinos + gamma rays Answer: D Diff: 3 Section Ref: 8.7 63) The speed of light is 3.00 × 108 m/s. If 2.00 kg of mass is converted to energy, how much energy will be produced?

A) 1.80 × 1017 J B) 6.00 × 108 J C) 1.50 × 108 J D) 6.00 × 104 J E) 9.00 × 1016 J Answer: A Diff: 3 Section Ref: 8.7 64) The critical temperature the core must reach for a star to shine by fusion is A) 5,800 K. B) 11,000 K. C) 127,000 K. D) 10 million K. E) 100 million K. Answer: D Diff: 2 Section Ref: 8.7

14 ..

65) Which of the following is NOT a property of neutrinos?

A) Can change forms in the eight minutes from the Sun's core to us B) Almost massless C) Can travel very close to the speed of light D) Neutral in charge E) Cannot interact at all with normal matter Answer: E Diff: 2 Section Ref: 8.8 66) Initially, fewer neutrinos were detected than predicted by theoretical models because A) neutrinos changed form to undetected types of neutrinos.

B) the wrong liquid was being used in neutrino detectors.

C) particle physicists did not understand the proton-proton chain.

D) the proton-proton chain does not actually produce neutrinos.

E) neutrinos take many years to pass out of the sun from its core.

Answer: A Diff: 2 Section Ref: 8.8 67) There appears to be a correlation between the 22-year solar cycle and A) droughts in North America.

B) asteroid impacts on Earth.

C) change of which political party has the majority in the U.S. Congress.

D) the length of Mercury's day.

E) the length of Saturn's year.

Answer: A Diff: 2 Section Ref: 8.8 68) Neutrinos travel from the Sun's core to the Earth in A) millions of years.

B) thousands of years.

C) a few days.

D) a few hours.

E) a few minutes.

Answer: E Diff: 1 Section Ref: 8.8 69) The observable ________ is a thin layer of the Sun in which the solar material becomes suddenly much more opaque as we look deeper into the Sun. Answer: photosphere Diff: 1 Section Ref: 8.1

15 ..

70) Energy produced in the solar core is transferred by ________ until it reaches a point about 500,000 km from the center.

Answer: radiation Diff: 2 Section Ref: 8.3 71) Iron is observed in the Sun's ________.

Answer: absorption spectrum Diff: 1 Section Ref: 8.4 72) In spite of its high temperature, we observe the solar corona best during ________.

Answer: a total solar eclipse Diff: 1 Section Ref: 8.4 73) The chromosphere is red because it is hot enough to ________ hydrogen atoms.

Answer: ionize Diff: 2 Section Ref: 8.4 74) In contrast to the photosphere's continuum, the spectrum of the chromosphere is dominated by ________ lines.

Answer: emission Diff: 2 Section Ref: 8.4 75) The solar magnetic field is strongest in those regions called ________, which are poles and usually thus occur in pairs.

Answer: sunspots Diff: 1 Section Ref: 8.5 76) If the last peak in sunspot numbers occurred in 2013, then the next solar max is ________.

Answer: 2024 Diff: 1 Section Ref: 8.5 77) The ________-year solar cycle is characterized by a variation in the number of sunspots and a reversal of the polarity of the Sun as a whole.

Answer: 22 Diff: 2 Section Ref: 8.5

16 ..

78) What do sunspots tell us about the Sun's rotation rate?

Answer: Watching and timing sunspots as they travel across the Sun's face allows us to measure the rotation rate and determine it does not rotate as a solid body. It experiences differential rotation with different rates near the poles and equator.

Diff: 2 Section Ref: 8.1 79) How is energy transfer from the solar interior to surface similar to a process in Earth's atmosphere?

Answer: The process of convection is responsible for energy transfer in both the Sun and Earth's atmosphere.

Diff: 3 Section Ref: 8.3 80) What are the main constituents of the solar wind?

Answer: Protons and electrons are the main constituents of the solar wind.

Diff: 2 Section Ref: 8.4 81) Why is it hard to observe the chromosphere?

Answer: Most of its energy is in the bright red emission line of hydrogen from its low density, so the denser photosphere gives off a lot more in the continuum.

Diff: 2 Section Ref: 8.4 82) What do sunspots tell us about the Sun's rotation rate?

Answer: Watching and timing sunspots as they travel across the Sun's face allows us to measure the rotation rate and determine it does not rotate as a solid body. It experiences differential rotation with different rates near the poles and equator.

Diff: 2 Section Ref: 8.5 83) Two pairs of sunspots appear similar, but if one photo was made in 1990, and the next photo was in 2002, we would note what difference?

Answer: In the 12 years, the magnetic field polarities will have reversed.

Diff: 2 Section Ref: 8.5 84) The sunspot cycle is sometimes described as lasting 11 years, but others prefer to consider it as 22 years; explain the rationale.

Answer: The numbers of sunspots come to a peak about every 11 years, but with the beginning of the next cycle, the polarities of the spot pairs reverse, so it takes 22 years to go through the magnetic polarity cycle.

Diff: 2 Section Ref: 8.5

17 ..

85) What was the Maunder Minimum?

Answer: A period of unusually low solar activity identified by the British astronomer of the same name that occurred between 1645 and 1715. This is also when there was a "little ice age" and less auroral activity.

Diff: 2 Section Ref: 8.5 86) Presently, what is happening to the helium in the sun's core?

Answer: It builds up there, for now the core is not hot enough to fuse it further.

Diff: 3 Section Ref: 8.7 87) What gives the most direct view into the Sun's core?

Answer: Neutrinos travel directly out of the Sun to the Earth in about 8 minutes. Neutrino detectors can detect these, confirming the nuclear reactions happening in the Sun's core.

Diff: 2 Section Ref: 8.8 88) How does solar luminosity vary during the sunspot cycle?

Answer: The Sun is slightly more luminous at periods of sunspot maximum than at sunspot minimum.

Diff: 3 Section Ref: 8.8 89) Describe the transport of energy, from the deep interior of the Sun, to when it finally reaches the Earth. Include the various methods of transport.

Answer: Energy is produced in the core. It enters the radiative zone, where it moves as radiation.

As it gets further out from the center, the gas gets less ionized and so more opaque to radiation.

In this region the energy moves by convection, with hot gas physically rising through the Sun. When it reaches the surface, or photosphere, the low density makes the Sun transparent, and the energy escapes as light.

Diff: 2 Section Ref: 8.3 90) Explain what the granulation of the solar surface is related to.

Answer: The surface of the Sun is highly mottled or granulated. Each granule is about 1,000 km across. The granulation is produced by the convection (boiling) of the Sun's gases. Each granule is the top of a convection cell that is welling up.

Diff: 2 Section Ref: 8.3 91) If the corona is so hot, why must we wait for a total solar eclipse to glimpse it?

Answer: It is so hot that almost all the energy it gives off, by Wien's Law, is not going to be in the visible, but the X-ray portion of the spectrum. Also, it is very low density, so there are far more atoms at 5,800 K giving off a lot of visible light than the few out in the corona.

Diff: 2 Section Ref: 8.4 18 ..

92) Explain what is meant by the solar cycle. What role does magnetism play?

Answer: The solar cycle is the periodic reversal of the Sun's magnetic field and occurs over a 22 year period. It is equal to two sunspot cycles. The north pole of the Sun changes to a south pole in 11 years and changes back to a north pole in another 11 years.

Diff: 2 Section Ref: 8.5 93) A solar flare creates a radio disturbance on Earth a few minutes after going off and again several days later. Explain.

Answer: A flare will give off intense X-rays and ultraviolet light, which travels to Earth in about 8 minutes. But also given off is an intense burst of high energy particles which travel to the Earth at speeds much less than the speed of light. They can take several days to reach the Earth. Both forms of radiation create radio disturbances when they reach the Earth.

Diff: 3 Section Ref: 8.6 94) Describe the method of energy production in the Sun. What is the fuel? What is the end product? What kind of interactions occur? What is the role of temperature in the process? Could we use this process to produce energy on Earth?

Answer: The Sun produces energy by fusing hydrogen into helium. In net, four hydrogen nuclei fuse to produce one helium nucleus, two neutrinos, and energy. The temperature required is very high (at least 10 million K — the Sun's core is 15 million K). Research is underway to develop a controllable similar process to generate energy on Earth.

Diff: 3 Section Ref: 8.7 95) In the proton-proton cycle, two positrons are produced. What are they similar to, and how are the different? What happens to them?

Answer: Positrons are the antiparticle to the electron. They are like the electron in mass but positive in charge. When positrons inevitably meet electrons, both particle and antiparticle are annihilated and energy is given off.

Diff: 3 Section Ref: 8.7

19 ..

Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 9 Measuring the Stars 1) The nearest naked- eye star to our Sun, Alpha Centauri, is still over a parsec distant.

Answer: TRUE Diff: 1 Section Ref: 9.1 2) The proper motion of a star is its true velocity through space.

Answer: FALSE Diff: 1 Section Ref: 9.1 3) The proper motion of a star, its distance, and Doppler shift can give us its space velocity.

Answer: TRUE Diff: 2 Section Ref: 9.1 4) First magnitude Spica appears 2.5 times brighter than second magnitude Polaris.

Answer: TRUE Diff: 2 Section Ref: 9.2 5) Star A and star B have the same apparent magnitude. Star A is twice as distant as star B. Therefore, star A has twice the luminosity as star B. Answer: FALSE Diff: 3 Section Ref: 9.2 6) If a star were moved 10 times farther away, its absolute magnitude would drop five magnitudes.

Answer: FALSE Diff: 3 Section Ref: 9.2 7) If a star were moved 10 times farther away, its apparent magnitude would drop by five magnitudes.

Answer: TRUE Diff: 3 Section Ref: 9.2 8) A type B9 star is hotter than a type A0.

Answer: TRUE Diff: 1 Section Ref: 9.3

1 ..

9) Hydrogen lines are weaker in both very hot and very cool stars.

Answer: TRUE Diff: 2 Section Ref: 9.3 10) A star of the Sun's diameter, but twice as hot, must be 16X more luminous than the Sun. Answer: TRUE Diff: 3 Section Ref: 9.4 11) On the main sequence, almost all stars have radii between about 0.1 and 10 times the Sun. Answer: TRUE Diff: 3 Section Ref: 9.5 12) The vast majority of stars near us would fall to the bottom right on the H-R diagram.

Answer: TRUE Diff: 3 Section Ref: 9.5 13) For luminosity classification, fat stars have skinny spectral lines.

Answer: TRUE Diff: 1 Section Ref: 9.6 14) In a spectroscopic binary, the star whose lines shift the most weighs the most.

Answer: FALSE Diff: 1 Section Ref: 9.7 15) Eclipsing binaries are the most useful, giving us sizes as well as masses of the pair.

Answer: TRUE Diff: 2 Section Ref: 9.7 16) In a binary system, the more massive stars always stay closer to the center of mass and move slower.

Answer: TRUE Diff: 2 Section Ref: 9.7

2 ..

17) A nearby star has a parallax of 0.2 arc seconds. What is its distance?

A) .1 parsec B) .2 parsec C) .5 parsec D) 5 parsecs E) 50 parsecs Answer: D Diff: 2 Section Ref: 9.1 18) What is proper motion?

A) It is the true, not apparent, motion of a star in space.

B) It is the apparent shift as we go to opposite sides of our orbit every six months.

C) It is the annual apparent motion of a star across the sky.

D) It is the motion of a star towards or away from us, revealed by Doppler shifts.

E) It is the orbital motion of a star around the Galaxy.

Answer: C Diff: 1 Section Ref: 9.1 19) Which statement about stellar motion is incorrect?

A) In general, the closer a star is, the more its proper motion.

B) The radial velocity is measured by the Doppler shift.

C) The transverse velocity is measured by the proper motion and the distance.

D) Like parallax, proper motion is measured over intervals of exactly six months.

E) The Pythagorean theorem relates space, transverse, and radial velocities.

Answer: D Diff: 2 Section Ref: 9.1 20) Which of the following best describes the size and distance relationship of our Sun and the nearest star?

A) A tennis ball here, another on the Moon B) Two beach balls separated by 100 city blocks C) Two grains of sand separated by 100 light-years D) Two golf balls separated by 300 kilometers E) Two baseballs separated by 100 yards Answer: D Diff: 2 Section Ref: 9.1

3 ..

21) If a star has a parallax of 0.05", then its distance in light-years is about A) 6.4 light-years.

B) 12.7 light-years.

C) 20 light-years.

D) 65 light-years.

E) 100 light-years.

Answer: D Diff: 2 Section Ref: 9.1 22) If a star is found by spectroscopic observations to be about 500 parsecs distant, its parallax is A) .2".

B) .5".

C) .02".

D) .002".

E) .005".

Answer: D Diff: 2 Section Ref: 9.1 23) Procyon lies about 13 light-years distant, thus its parallax is about A) 0.01".

B) 0.25".

C) 0.40".

D) 0.65".

E) 1.3".

Answer: B Diff: 3 Section Ref: 9.1 24) In order to turn a star's proper motion into its space velocity, we must also know A) its mass and spectral type.

B) its temperature and age.

C) its distance and radial velocity.

D) its distance and mass.

E) its spectral type and period of rotation.

Answer: C Diff: 3 Section Ref: 9.1

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25) If a star appears to move back and forth relative to other stars over a six-month period, this motion is due to the star's A) transverse motion.

B) radial motion.

C) parallax shift.

D) Doppler shift.

E) true space motion.

Answer: C Diff: 3 Section Ref: 9.1 26) If a star appears to move relative to other stars over a one-year period, this motion is due to the star's A) transverse motion.

B) radial motion.

C) parallax shift.

D) Doppler shift.

E) true space motion.

Answer: E Diff: 3 Section Ref: 9.1 27) Roughly how many stars are within 4 parsecs of the solar system?

A) 3 B) 30 C) 3000 D) 300,000 E) 200 billion Answer: B Diff: 1 Section Ref: 9.1 28) What is the absolute magnitude of our Sun? A) -23.0 B) -4.6 C) -1.4 D) +4.8 E) +9.4 Answer: D Diff: 2 Section Ref: 9.2

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29) The absolute magnitude of a star is its brightness as seen from a distance of A) one million kilometers.

B) one astronomical unit.

C) one light-year.

D) ten parsecs.

E) 10 light-years.

Answer: D Diff: 2 Section Ref: 9.2 30) Perhaps the greatest of the Greek astronomers, ________ compiled the first catalog of stars, accurately measured their positions, and defined the basic system of stellar brightnesses.

A) Erastothenes B) Aristotle C) Ptolemy D) Hipparchus E) Aristarchus Answer: D Diff: 2 Section Ref: 9.2 31) In comparing first magnitude Deneb with second magnitude Polaris, we find that A) Polaris is in reality much more luminous.

B) Deneb must be much hotter than Polaris.

C) Deneb appears 2.5 times brighter to us than does Polaris.

D) Polaris is really 100 times brighter than nearby Deneb.

E) Deneb is really much closer than Polaris.

Answer: C Diff: 2 Section Ref: 9.2 32) At the distance of Jupiter (6 times further away from the Sun than Earth) the amount of sunlight received per square centimeter different by what factor?

A) 6 times less B) 12 times less C) 36 times less D) 6 times more E) 12 times more Answer: C Diff: 3 Section Ref: 9.2

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33) Star A and star B both have an apparent magnitude of 4.0, but star A has an absolute magnitude of 1.0 and star B has an absolute magnitude of 7.0. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.

B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.

C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A. D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B. E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Answer: D Diff: 3 Section Ref: 9.2 34) Star A and star B both have an apparent magnitude of 7.0, but star A is at a distance of 15 pc and star B is at a distance of 30 pc. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.

B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.

C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A. D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B. E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Answer: C Diff: 3 Section Ref: 9.2 35) Star A and star B both have an absolute magnitude of 2.0, but star A is at a distance of 50 pc and star B is at a distance of 20 pc. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.

B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.

C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A. D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B. E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Answer: B Diff: 3 Section Ref: 9.2

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36) Star A and star B both have an absolute magnitude of 2.0, but star A has an apparent magnitude of 5.0 and star B has an apparent magnitude of 7.0. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.

B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.

C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A. D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B. E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Answer: A Diff: 3 Section Ref: 9.2 37) Star A has an absolute magnitude of 2.5 and star B has an apparent magnitude of 2.5, but star A is a main sequence star and star B is a red giant. Which statement below is correct?

A) Star A appears brighter than star B, but star B and star A have the same intrinsic brightness.

B) Star B appears brighter than star A, but star B and star A have the same intrinsic brightness.

C) Star A and star B appear to have the same brightness, but star B is intrinsically brighter than star A. D) Star A and star B appear to have the same brightness, but star A is intrinsically brighter than star B. E) It is impossible to determine how bright these stars are or appear to be relative to one another, given the information above.

Answer: E Diff: 3 Section Ref: 9.2 38) What physical property of a star does the spectral type measure?

A) Density B) Luminosity C) Temperature D) Mass E) Composition Answer: C Diff: 1 Section Ref: 9.3

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39) Star A is a main sequence star of spectral type F2 and star B is a white dwarf of spectral type B4. Which statement below is correct?

A) Star A appears brighter than star B. B) Star B appears brighter than star A. C) Star A is hotter than star B. D) Star B is hotter than star A. E) None of the above can be said about these two stars.

Answer: D Diff: 3 Section Ref: 9.3 40) Star A is a main sequence star of spectral type G5 and star B is a red giant of spectral type K2. Which statement below is correct?

A) Star A appears brighter than star B. B) Star B appears brighter than star A. C) Star A is hotter than star B. D) Star B is hotter than star A. E) None of the above can be said about these two stars.

Answer: C Diff: 3 Section Ref: 9.3 41) Two red stars have surface temperatures of 3000 K, but Star A's luminosity is about 5% of the Sun's and Star B's luminosity is about 32,000 times the luminosity of the Sun. How much bigger is star B than star A? A) They are the same size.

B) Star B's radius is about 16 times larger than star A's radius.

C) Star B's radius is about 800 times larger than star A's radius.

D) Star B's radius is about 640,000 times larger than star A's radius.

E) This cannot be determined from the information given.

Answer: C Diff: 3 Section Ref: 9.4 42) Stars that have masses similar to the Sun's, and sizes similar to the Earth are A) main sequence stars.

B) white dwarfs.

C) red giants.

D) red dwarfs.

E) brown dwarfs.

Answer: B Diff: 1 Section Ref: 9.4

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43) Compared to the size of the Sun, in what range of sizes are nearly all stars found?

A) .5 to 2 solar radii B) 0.1 to 1.0 solar radii C) 0.5 to 50 solar radii D) 1 to 100 solar radii E) 0.01 to 100 solar radii Answer: E Diff: 2 Section Ref: 9.5 44) On the H-R diagram, the Sun lies A) at the top left.

B) at the bottom left.

C) at the bottom right.

D) about the middle of the main sequence.

E) at the top right.

Answer: D Diff: 1 Section Ref: 9.5 45) Which of the following is the most common type of star?

A) High mass main sequence B) Low mass main sequence C) White dwarfs D) Red giants E) Blue supergiants Answer: B Diff: 1 Section Ref: 9.5 46) The Hertzsprung-Russell Diagram plots ________ against the spectral type or temperature.

A) distance B) luminosity or absolute magnitude C) brightness or apparent magnitude D) size or density E) mass Answer: B Diff: 1 Section Ref: 9.5

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47) How might the most common occurring stars be described, based on our stellar neighborhood?

A) White dwarfs B) K giants C) G main sequence D) A main sequence E) M main sequence Answer: E Diff: 2 Section Ref: 9.5 48) On the H-R diagram, red supergiants like Betelgeuse lie A) at the bottom left.

B) at the bottom right.

C) at the top left.

D) at the top right.

E) They can't be plotted, for they are not main sequence.

Answer: D Diff: 2 Section Ref: 9.5 49) On the H-R diagram, white dwarfs lie Sirius B and Procyon B lie A) at the top left.

B) at the top right.

C) close to the Sun, near the center.

D) at the lower left.

E) at the lower right.

Answer: D Diff: 2 Section Ref: 9.5 50) In the H-R diagram, the bright blue-white stars that dominate the naked eye sky lie to the A) top left.

B) top right.

C) middle of the main sequence.

D) top center.

E) bottom left.

Answer: A Diff: 2 Section Ref: 9.5

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51) What are the two most important intrinsic properties used to classify stars?

A) Mass and age B) Luminosity and surface temperature C) Distance and luminosity D) Distance and surface temperature E) Distance and color Answer: B Diff: 1 Section Ref: 9.5 52) Having nothing to do with trigonometry, ________ parallaxes use the width of absorption lines to estimate the star's luminosity and size and distance.

A) bolometric B) photometric C) spectroscopic D) holographic E) videometric Answer: C Diff: 1 Section Ref: 9.6 53) In general, the narrower the spectral line of a star A) the hotter the star is.

B) the bigger the star is.

C) the denser the star is.

D) the smaller the star is.

E) the cooler the star is.

Answer: B Diff: 2 Section Ref: 9.6 54) Upon what data do measurements of sizes of eclipsing binaries depend?

A) Their orbital periods and separations B) Their masses and luminosities C) Their Doppler shifts and durations of stages of their eclipses D) Their temperatures and speeds E) Their temperatures and masses Answer: C Diff: 2 Section Ref: 9.7

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55) Which type of binary can have their sizes measured directly by photometry?

A) Virtual B) Visual C) Eclipsing D) Spectroscopic E) Astrometric Answer: C Diff: 2 Section Ref: 9.7 56) In what range of masses are most stars found?

A) .1 to 2 solar masses B) 1 to 3 solar masses C) .1 to 100 solar masses D) .01 to 100 solar masses E) Stars can have any mass.

Answer: C Diff: 2 Section Ref: 9.7 57) In a visual binary system with circular orbits, if in 20 years the two stars' position angles have shifted by 30 degrees, the pair's period must be A) 60 years.

B) 90 years.

C) 120 years.

D) 240 years.

E) 360 years.

Answer: D Diff: 2 Section Ref: 9.7 58) In a spectroscopic binary system, the star showing the larger blue shift is A) cooler and receding the fastest.

B) less massive of the pair and receding slower.

C) more massive and approaching us.

D) less massive and approaching us at this moment.

E) hotter and receding faster.

Answer: D Diff: 3 Section Ref: 9.7

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59) In a spectroscopic binary, if a pair shows a combined set of lines tonight, but a maximum split two nights later, its orbital period must be A) one day.

B) two days.

C) four days.

D) eight days.

E) twelve days.

Answer: D Diff: 3 Section Ref: 9.7 60) A star with a parallax of 1 second of arc is at a distance of ________ by definition.

Answer: one parsec Diff: 1 Section Ref: 9.1 61) A star's motion across the sky is its ________ motion.

Answer: proper Diff: 2 Section Ref: 9.1 62) The ________ magnitude of a star depends directly upon its luminosity and distance.

Answer: apparent Diff: 1 Section Ref: 9.2 63) From hottest to coolest, the seven letters for the star types are ________.

Answer: OBAFGKM Diff: 1 Section Ref: 9.3 64) If two stars are the same size and one is twice the temperature of the other, how much more luminous is the hotter one?

Answer: 16 times Diff: 2 Section Ref: 9.4 65) Capella is the same temperature as our Sun, but about ten times the Sun's diameter; it must be about ________ times as luminous as our star.

Answer: 100 Diff: 3 Section Ref: 9.4

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66) Knowledge of a star's temperature and ________ enables us to calculate its radius, surface area, and volume from the appropriate radiation law.

Answer: luminosity or absolute magnitude Diff: 2 Section Ref: 9.4 67) On the H-R diagram, most bright naked eye stars would lie at the ________.

Answer: top left Diff: 2 Section Ref: 9.5 68) On the main sequence on an H-R diagram, our Sun lies at about ________.

Answer: the center Diff: 2 Section Ref: 9.5 69) All classes of binary stars yield the basic information on stellar ________.

Answer: masses Diff: 1 Section Ref: 9.7 70) In an eclipsing binary, the longer the stages of the eclipse take, the ________ the star.

Answer: larger Diff: 2 Section Ref: 9.7 71) How is proper motion measured?

Answer: It is the apparent motion of the star, in seconds of arc, over an interval of exactly one year, after the Earth returns to the same place in its orbit, and all parallax is negated.

Diff: 2 Section Ref: 9.1 72) Why must both parallax and proper motion be known to give transverse velocity?

Answer: To turn the star's apparent motion across our line of sight into its real velocity in that direction, we also need to know the actual distance from parallax data.

Diff: 2 Section Ref: 9.1 73) The apparent magnitude of the Sun is -26, while Sirius has an apparent magnitude of -1; how much brighter does the Sun appear than Sirius?

Answer: This is a difference of 25 magnitudes. As each 5 magnitudes is a brightness factor of 100X, then 100 to the fifth power is 10 billion times brighter.

Diff: 2 Section Ref: 9.2

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74) What role does hydrogen play in spectral classification?

Answer: Its spectral lines are most obvious in mid-temperature stars and least obvious in both very hot and very cool stars.

Diff: 2 Section Ref: 9.3 75) How can a white dwarf be hotter than our Sun, yet much less luminous?

Answer: They are only about as big as Earth, so their surface area is about 10,000X less than the Sun's.

Diff: 2 Section Ref: 9.4 76) Contrast main sequence stars of type B and G. Answer: The B star will be hotter, larger, more massive and more luminous.

Diff: 2 Section Ref: 9.5 77) Why is the main sequence main? Why are these stars so common?

Answer: While their masses, luminosities, and temperatures vary greatly, like the Sun, all of them are relatively young, with plenty of hydrogen still left to turn into helium in their cores.

Hydrogen is still the most common element in the universe.

Diff: 3 Section Ref: 9.5 78) How is distance determined to the nearest stars? How far out can this technique be applied?

How many stars can be measured in this way?

Answer: The distance to the nearest stars is measured using parallax. The star is observed when the Earth is on either side of its orbit, six months apart. From the slight motion of the star, resulting from the Earth's change in perspective, and knowing the size of the Earth's orbit, the distance to the star can be calculated. The GAIA mission should be able to measure the distance to billions of stars (10,000 or more parsecs distant).

Diff: 2 Section Ref: 9.1 79) What is proper motion? How is it related to transverse velocity?

Answer: Annual apparent motion of a star across the sky, in arc seconds per year. If we also know the star's distance, this angular motion can be turned into the transverse velocity in km/sec.

Diff: 2 Section Ref: 9.1

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80) What types of observations are necessary to determine the motion of a star through space?

Answer: To determine the true space motion of a star both the radial velocity and transverse velocities must be determined. The radial velocity can be determined directly from observing the spectrum and measuring the Doppler shift of the absorption lines. The transverse velocity is calculated from observations of a star's proper motion and distance. The proper motion is the angular motion per year of the star. Once the radial velocity and transverse velocities are known, the space motion of the star is calculated using the Pythagorean theorem (square root of the sum of the squares of the velocities).

Diff: 3 Section Ref: 9.1 81) Two stars have apparent magnitudes of 0 and 5. If both stars are 117 parsecs away, which star is intrinsically brighter and by what factor is it brighter than the other?

Answer: Since both stars are at the same distance (it does not matter what the distance is), the magnitude 0 star is the brightest. It is intrinsically 100 times brighter than the magnitude 5 star because 5 magnitudes is always a factor of 100 in intrinsic brightness.

Diff: 3 Section Ref: 9.2 82) What types of observations are necessary to determine the absolute luminosity of a star?

Answer: The absolute luminosity of a star, or absolute magnitude, is determined from the apparent magnitude and distance. The apparent magnitude is rather easily measured using a telescope and a photometer. The distance can be much harder to determine. If the star is nearby then its parallax can be measured. If more distant, some other method will have to be used, such as spectroscopic parallax. Spectroscopic parallax will give the absolute magnitude of the star without having to compute distance.

Diff: 3 Section Ref: 9.2 83) Why are spectra of stars different?

Answer: Spectra of stars differ primarily because of differences in their temperatures. Smaller differences occur because of luminosity differences and even smaller differences occur because of slightly different compositions.

Diff: 3 Section Ref: 9.3 84) A star similar to Sirius A has a temperature of about 10,000 K, and a luminosity of around 25 times that of the Sun. Approximately what is its radius?

Answer: Using T in units of 5000 K, that gives T=2, L = 25, so R = sqrt(25) / 2 = 2.5 times the radius of the Sun, consistent with the value of 2.8 times the radius of the Sun for Sirius A. Diff: 3 Section Ref: 9.4

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85) In a large sampling of stars, the largest group represented in the H-R diagram will be the main sequence stars. Why are they so common?

Answer: Like the Sun, they are young enough to have most of their initial hydrogen still not fused into helium; they will not evolve off the main sequence until the helium builds up a lot.

Since hydrogen is by far the most abundant element and the easiest to fuse, most stars are going to use it as their major fuel, as long as the supply lasts. Stars spend the vast majority of their life spans on the main sequence.

Diff: 2 Section Ref: 9.5 86) Explain how the shifting spectral lines of spectroscopic binaries let us find their periods.

Answer: When aligned in our line of sight, there is no radial velocity, and all lines appear single.

A quarter of a period later, one is approaching us with its line blue shifted, and the other is receding. Multiply this time span by four, and the two stars are back in the original positions.

Diff: 2 Section Ref: 9.7

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 10 Star Formation and Evolution 1) Hydrogen is the major gas in the interstellar medium.

Answer: TRUE Diff: 1 Section Ref: 10.1 2) Interstellar matter is distributed very evenly through the galaxy.

Answer: FALSE Diff: 2 Section Ref: 10.1 3) The gas in the interstellar medium consists of mostly heavy elements.

Answer: FALSE Diff: 2 Section Ref: 10.1 4) The birth of stars is a battle between gravity and radiation pressure.

Answer: TRUE Diff: 1 Section Ref: 10.2 5) The fundamental difference between a protostar and a star is that the latter has nuclear fusion as its energy source and the former does not.

Answer: TRUE Diff: 1 Section Ref: 10.2 6) It takes about 1032 hydrogen atoms to make a star.

Answer: FALSE Diff: 2 Section Ref: 10.2 7) The Orion Nebula glows strongly in the infrared.

Answer: TRUE Diff: 1 Section Ref: 10.3 8) Protostars have not been observed, but are consistent with observations of young main sequence stars.

Answer: FALSE Diff: 2 Section Ref: 10.3

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9) Modern astronomers have observed the complete life cycle for many stars, making stellar evolution one of the best-tested astronomical theories.

Answer: FALSE Diff: 1 Section Ref: 10.4 10) Evolution of a star off the main sequence is caused by the loss of mass from hydrogen fusion by the star while a main sequence star.

Answer: FALSE Diff: 1 Section Ref: 10.4 11) When a star becomes a red giant, its core expands to a roughly proportional larger size too.

Answer: FALSE Diff: 1 Section Ref: 10.4 12) As a star begins to evolve away from the main sequence, it gets larger.

Answer: TRUE Diff: 2 Section Ref: 10.4 13) When helium fusion begins in a one solar mass main star, it begins gradually, with this rate slowly increasing over time.

Answer: FALSE Diff: 2 Section Ref: 10.5 14) The shell ejection in making a planetary is spherical and symmetrical in all cases.

Answer: FALSE Diff: 2 Section Ref: 10.5 15) Eventually, all low mass stars will become white, then black, dwarfs.

Answer: TRUE Diff: 1 Section Ref: 10.5 16) All planetary nebulae are slowly-expanding spherical disks ejected by red giants, while their exposed cores appear as white dwarfs.

Answer: FALSE Diff: 2 Section Ref: 10.5

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17) For our Sun, the production of carbon will be the end of its nucleosynthesis.

Answer: TRUE Diff: 3 Section Ref: 10.5 18) Most stars are usually formed singularly or as binaries, not in clusters.

Answer: FALSE Diff: 2 Section Ref: 10.7 19) Interstellar gas is composed of A) only hydrogen.

B) 90% hydrogen, 9% helium by weight.

C) 10% hydrogen, 90% helium by numbers of atoms.

D) some hydrogen, but mainly carbon dioxide.

E) ammonia, methane, and water vapor.

Answer: B Diff: 1 Section Ref: 10.1 20) What effect do even thin clouds of dust have on light passing through them?

A) The light that passes though them is blue shifted due to the cloud's approach.

B) It dims the light of all more distant stars.

C) Even a little can completely block all light, such as the Horsehead Nebula.

D) Its motion causes the light of stars beyond to twinkle.

E) Its motion causes all light to be redshifted as it passes through these clouds.

Answer: B Diff: 1 Section Ref: 10.1 21) Some regions along the plane of the Milky Way appear dark because A) there are no stars in these areas.

B) stars in that region are hidden by interstellar gas.

C) stars in that region are hidden by dark dust particles.

D) many brown dwarfs in those areas absorb light which they turn into heat.

E) many black holes absorb all light from those directions.

Answer: C Diff: 2 Section Ref: 10.1

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22) Which statement is TRUE about the interstellar medium?

A) Gas contains a lot of carbon atoms.

B) Dust blocks the longest electromagnetic wavelengths.

C) Gas obscures the light from distant stars.

D) We know more about the gas than the dust.

E) Dust is spread uniformly through the galaxy.

Answer: D Diff: 2 Section Ref: 10.1 23) The spectra of interstellar gas clouds show that they have the same basic composition as A) interstellar dust.

B) Earth's atmosphere.

C) stars.

D) asteroids.

E) the Martian polar caps.

Answer: C Diff: 2 Section Ref: 10.1 24) The density of interstellar dust is very low, yet it still blocks starlight because A) it is so cold it absorbs higher energy photons.

B) there is 100 times more opaque gas than dust present in the ISM. C) the dust particles are about the same size as the light waves they absorb.

D) the dust particles are irregular in shape.

E) ice particles reflect all light back toward their stars, not toward us.

Answer: C Diff: 2 Section Ref: 10.1 25) In the Milky Way galaxy, gas and dust are found A) in molecular clouds.

B) everywhere.

C) in neutral hydrogen clouds.

D) in dark nebulae.

E) in emission nebulae.

Answer: B Diff: 3 Section Ref: 10.1

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26) What is the force that keeps a main sequence star from blowing apart?

A) Magnetism B) Gravitation C) The strong force D) Radiation pressure E) Electron degeneration pressure Answer: B Diff: 3 Section Ref: 10.2 27) Which event marks the birth of a star?

A) Formation of the planetary nebula B) Fusion of hydrogen atoms into helium atoms C) Collapse of an interstellar cloud D) Formation of a photosphere E) Instability in an interstellar cloud Answer: B Diff: 1 Section Ref: 10.2 28) What happens when an interstellar cloud fragment shrinks?

A) It first becomes opaque.

B) Density rises.

C) Temperature rises.

D) Pressure rises.

E) all of the above Answer: E Diff: 1 Section Ref: 10.2 29) How long does it take for a star like our Sun to form?

A) 100 thousand years B) Two million years C) Fifty million years D) One billion years E) 4.6 billion years Answer: C Diff: 2 Section Ref: 10.2

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30) A typical protostar may be several thousand times more luminous than the Sun. What is the source of this energy?

A) Chemical combustion of hydrocarbons B) Nuclear fusion in its core C) From the release of gravitational energy as the protostar continues to shrink D) The ionization of the gas as it heats up E) From nearby hot stars or supernovae that have initiated the star formation process Answer: C Diff: 2 Section Ref: 10.2 31) Stars form from a collapsing cloud that fragments into smaller and smaller pieces. This process takes about A) 10,000 years.

B) 25,000 years.

C) 100,000 years.

D) a few million years.

E) 100 million years.

Answer: D Diff: 3 Section Ref: 10.2 32) If the initial interstellar cloud in star formation has a mass sufficient to form hundreds of stars, how does a single star form from it?

A) One star forms at its center and blows the rest of the matter back into space.

B) The cloud fragments into smaller clouds and forms many stars at one time.

C) One star forms and the rest of the matter goes into making planets, moons, and other objects of a solar system.

D) The cloud is disrupted by rotation so that it reduces its mass down to that of a typical star.

E) A supernova blows the cloud up and dissipates the majority of the gas.

Answer: B Diff: 2 Section Ref: 10.3 33) The stars found in nebulae like the Orion Nebula probably formed A) within the last few million years.

B) about 10 million years ago.

C) hundreds of millions of years ago.

D) billions of years ago.

E) at the beginning of the universe.

Answer: A Diff: 3 Section Ref: 10.3

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34) Protostars can be observed in A) the Crab Nebula.

B) the Andromeda Galaxy.

C) the Orion Nebula.

D) our Solar System.

E) the Helix Nebula.

Answer: C Diff: 1 Section Ref: 10.3 35) What inevitably forces a star like the Sun to evolve away from being a main sequence star?

A) The core begins fusing iron.

B) The star uses up all its supply of hydrogen.

C) The carbon detonation explodes it as a type I supernova.

D) Helium builds up in the core, while the hydrogen burning shell expands.

E) The core loses all its neutrinos, so all fusion ceases.

Answer: D Diff: 2 Section Ref: 10.4 36) Just as a low-mass main sequence star runs out of fuel in its core, it actually becomes brighter. How is this possible?

A) Helium fusion gives more energy than hydrogen fusion does, based on masses.

B) Its outer envelope is stripped away and we see the brilliant core.

C) The core contracts, raising the temperature and increasing the size of the region of hydrogen shell-burning.

D) It explodes.

E) It immediately starts to fuse helium.

Answer: C Diff: 2 Section Ref: 10.4 37) A solar mass star will evolve off the main sequence when A) it completely runs out of hydrogen.

B) it expels a planetary nebula to cool off and release radiation.

C) it explodes as a violent nova.

D) it builds up a core of inert helium.

E) it loses all its neutrinos, so fusion must cease.

Answer: D Diff: 3 Section Ref: 10.4

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38) What temperature is needed to fuse helium into carbon?

A) 5,800 K B) 100,000 K C) 15 million K D) 100 million K E) One billion K Answer: D Diff: 2 Section Ref: 10.5 39) The "helium flash" occurs at what stage in stellar evolution?

A) When the T Tauri bipolar jets shoot out B) In the middle of the main sequence stage C) Red giant D) Horizontal branch E) Planetary nebula Answer: C Diff: 2 Section Ref: 10.5 40) During the hydrogen shell burning phase A) the star grows more luminous.

B) the star becomes less luminous.

C) helium is burning in the core.

D) the core is expanding.

E) hydrogen is burning in the central core.

Answer: A Diff: 2 Section Ref: 10.5 41) What is a planetary nebula?

A) The bipolar jets ejected by a T Tauri variable B) A planet surrounded by a glowing shell of gas C) The disc of gas and dust surrounding a young star that will soon form a solar system D) The ejected envelope, often bipolar, of a red giant surrounding a stellar core remnant E) A type of young, medium mass star Answer: D Diff: 1 Section Ref: 10.5

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42) What are black dwarfs?

A) The lowest mass main sequence stars B) The end result of massive star evolution C) Objects that are not quite massive enough to be stars D) Pulsars that have slowed down and stopped spinning E) Cooled off white dwarfs that no longer glow visibly Answer: E Diff: 1 Section Ref: 10.5 43) The order of evolutionary stages of a star like the Sun would be Main Sequence, giant, planetary nebula, and finally A) hypernova.

B) neutron star.

C) white dwarf.

D) nova.

E) black hole.

Answer: C Diff: 2 Section Ref: 10.5 44) Compared to our Sun, a typical white dwarf has A) about the same mass and density.

B) about the same mass and a million times higher density.

C) a larger mass and a 100 times lower density.

D) a smaller mass and half the density.

E) a smaller mass and twice the density.

Answer: B Diff: 2 Section Ref: 10.5 45) Which of these will the Sun probably become in the very distant future?

A) Hypernova B) Supernova C) Pulsar D) Planetary nebula E) Nova Answer: D Diff: 2 Section Ref: 10.5

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46) Which of the following is TRUE regarding planetary nebulae?

A) Some are spherical, but most have bipolar structure.

B) They are the result of the mass loss during the main sequence stage of the most massive stars.

C) They are the rings of material surrounding newly formed stars that will eventually form the planetary systems.

D) They are the ejected envelopes of highly evolved brown dwarf stars.

E) They are the coronas surrounding most blue stragglers.

Answer: A Diff: 3 Section Ref: 10.5 47) A high-mass star dies more violently than a low-mass star because A) it must always end up as a black hole.

B) it generates more heat and its core eventually collapses very suddenly.

C) it cannot fuse elements heavier than carbon.

D) gravity is weakened by its high luminosity.

E) it is most often found as part of a binary system.

Answer: B Diff: 1 Section Ref: 10.6 48) Isolated main-sequence stars as massive as 10 to 12 times the mass of the Sun may still manage to avoid going supernova. Why? A) Because they can also have strong stellar winds B) Because about half that mass will be contained in the carbon core C) Because they would be classified as brown dwarfs D) Because these stars will eject at least 4 solar masses in the planetary nebula stage E) Because their masses will decrease as they fuse heavy elements into lighter elements in their cores Answer: A Diff: 2 Section Ref: 10.6 49) Which of the following best describes the evolutionary track followed on the H-R diagram for the most massive stars?

A) Vertically upward, along the left edge of the diagram B) Diagonally to lower right, then vertical, then horizontally left C) Horizontally right, diagonally to lower left, then horizontally right D) Horizontally right E) Horizontally right, then forms a clockwise loop Answer: D Diff: 3 Section Ref: 10.6

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50) Eta Carinae is an example of a A) black hole.

B) supermassive star.

C) red dwarf.

D) nebula.

E) stellar nursery.

Answer: B Diff: 1 Section Ref: 10.6 51) As a 4-10 solar mass star leaves the main sequence on its way to becoming a red supergiant, its luminosity A) decreases.

B) first decreases, then increases.

C) increases.

D) remains roughly constant.

E) first increases, then decreases.

Answer: D Diff: 3 Section Ref: 10.6 52) Which type of star has the strongest stellar winds?

A) Giant K- and M-type stars B) White dwarfs C) Dwarf K- and M-type stars D) Main sequence O- and B-type stars E) T Tauri stars Answer: D Diff: 2 Section Ref: 10.6 53) What is the source of the large dust shells seen around some red giants and red supergiants?

A) Leftover material from their formation B) Debris left behind by a supernova C) Material from winds from these same stars D) Debris left behind by passing comets E) Star-forming molecular clouds Answer: C Diff: 1 Section Ref: 10.6

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54) Most stars in the Milky Way probably formed A) alone.

B) in intergalactic space, then were swept up into the Galaxy.

C) in clusters in the Galaxy's spiral arms.

D) from planetary nebulae.

E) in the galactic Nucleus, then migrated outward later.

Answer: C Diff: 1 Section Ref: 10.7 55) Why are star clusters almost ideal "laboratories" for stellar studies?

A) All stars in the cluster are the same size and luminosity.

B) Their combined light makes them much easier to spot from a distance.

C) Stars in clusters have the same age, similar composition, and are at the same distance away.

D) Stars in clusters are all relatively young and therefore shine brightly.

E) Like our Sun, stars in clusters are always located in the plane of the Milky Way Galaxy.

Answer: C Diff: 1 Section Ref: 10.7 56) What are the characteristics of globular cluster stars?

A) No stars as hot as our Sun B) Old age and hundreds of thousands to millions of member stars C) No main sequence stars left, with billions of member stars D) A few hundred stars, most still on the main sequence E) Hundreds of light years across, with bright OB stars dominant Answer: B Diff: 2 Section Ref: 10.7 57) What are the characteristics of an open cluster of stars?

A) Mostly found above and below the galactic plane B) Old age and millions of members C) A few hundred, mainly main sequence stars D) All stars are much more massive than our Sun. E) All stars are about the same age and luminosity.

Answer: C Diff: 2 Section Ref: 10.7

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58) All globular clusters in our Milky Way are about how old?

A) Less than a million years B) Ten-fifty million years old C) One to three billion years old D) Around ten billion years old E) A variety of ages, from newly born to twenty billion years old Answer: D Diff: 2 Section Ref: 10.7 59) The most important fact about a cluster of stars that makes them useful for studying star formation is that A) all the stars formed from the same cloud.

B) all the stars formed at about the same time.

C) all the stars are at the same distance from Earth.

D) all the stars have the same chemical composition.

E) all the stars are the same spectral type.

Answer: B Diff: 3 Section Ref: 10.7 60) The birthplaces of stars correspond to the ________ clouds in the interstellar medium.

Answer: densest (and coldest) Diff: 2 Section Ref: 10.2 61) A protostar develops a bipolar flow of gas when it is still surrounded by an equatorial disk of ________.

Answer: dust Diff: 1 Section Ref: 10.2 62) The Trifid Nebula is an example of a(n) ________ nebula.

Answer: emission Diff: 2 Section Ref: 10.3 63) The Main Sequence is the first stellar stage in which energy produced by ________ balances the energy lost by radiation from the surface of the star.

Answer: fusion (of hydrogen into helium) or nuclear reactions Diff: 1 Section Ref: 10.4

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64) In an H-R Diagram, the path showing changes in a star's luminosity and surface temperature as a function of time is called its ________.

Answer: evolutionary track Diff: 2 Section Ref: 10.4 65) The order of evolutionary stages of a star like the Sun would be Main Sequence, giant, planetary nebula, and finally a ________.

Answer: white dwarf.

Diff: 1 Section Ref: 10.5 66) A ________ stage is a relatively gentle mass-loss event which allows a star to peacefully readjust its structure into a white dwarf configuration.

Answer: planetary nebula Diff: 2 Section Ref: 10.5 67) Contrast the chemical composition of interstellar gas with that of interstellar dust.

Answer: Gas is almost all hydrogen and helium, but the dust is clumps of heavier elements, condensed out as grains much like the material of the Earth.

Diff: 2 Section Ref: 10.1 68) Why can radio waves get through the dust clouds, but light is blocked?

Answer: The interstellar dust grains are about the size of the waves of light they absorb, but are much smaller than the long radio waves that move around them freely.

Diff: 2 Section Ref: 10.1 69) What event marks the birth of a new star?

Answer: The ignition of nuclear fusion of hydrogen into helium at ten million K. Diff: 1 Section Ref: 10.2 70) An interstellar gas cloud has the mass to form hundreds of stars. What generally happens to it?

Answer: The cloud fragments into smaller clouds and forms many stars.

Diff: 1 Section Ref: 10.2 71) Why does gravitational contraction halt in collapsing protostars?

Answer: Gravitational contraction heats up the protostar in stages 2-4, but once the star has heated up enough, its radiation pressure stabilizes it as nuclear fusion ignites.

Diff: 2 Section Ref: 10.2 14 ..

72) What is causing the Trifid Nebula to glow?

Answer: In this nebula, there is a single energetic star that is producing enough electromagnetic radiation to ionize much of the nebula. When electrons recombine with hydrogen atoms, the photon released is red, causing the characteristic red glow.

Diff: 2 Section Ref: 10.3 73) Why can we say a star spends its life trying to maintain equilibrium?

Answer: A star is only stable when the inward pull of gravity is balanced by the outward pressure of radiation from the core. When the star is balanced, it is in hydrostatic equilibrium.

Diff: 2 Section Ref: 10.4 74) When a low-mass star runs out of hydrogen in its core, it gets brighter. Why? Answer: Without radiation pressure to inflate it, the core contracts again and heats up, making the hydrogen burning shell expand as well.

Diff: 2 Section Ref: 10.4 75) What is a helium flash?

Answer: A helium flash is a runaway condition caused by a core that collapses to a degenerate state before helium fusion can begin. As a result, the core cannot respond to the radiation produced by helium fusion and the fusion rate goes unchecked.

Diff: 2 Section Ref: 10.5 76) What element are most white dwarfs primarily made of? Why? Answer: They consist largely of carbon, for it is the last element made in their low mass cores, where gravitational contraction will not be able to yield the 600 million K temperatures to go beyond carbon to oxygen and still heavier elements.

Diff: 3 Section Ref: 10.5 77) During various stages of evolution, low mass stars (like the Sun) differ significantly from high mass stars. How and why are the main sequence lifetimes different?

Answer: High mass stars burn out quickly and so have short lifetimes. Low mass stars have very long lifetimes.

Diff: 2 Section Ref: 10.6 78) During various stages of evolution, low mass stars (like the Sun) differ significantly from high mass stars. How do they differ in terms of observational properties while Main Sequence stars?

Answer: High mass stars are blue or white and very luminous. Low mass stars are yellow to red and not nearly as bright.

Diff: 3 Section Ref: 10.6 15 ..

79) Contrast the brightest stars of young open and old globular clusters.

Answer: Hot blue main sequence stars light up young open clusters, but the aging globular clusters have long since lost such short-lived massive stars; they have red giants as their brightest, most evolved survivors.

Diff: 2 Section Ref: 10.7 80) Discuss the relationship between young stars, the interstellar medium and nebulae.

Answer: Young stars give off ultraviolet radiation, heating the surrounding gas cloud and causing it to glow as an emission nebula. Solar wind from the young stars pushes on the nebula, which can sweep away the gas, but can also cause compression leading to more new star formation.

Diff: 3 Section Ref: 10.3 81) How is it possible that life cycles of stars are so well understood and tested, even though they can take billions of years to happen?

Answer: Astronomers have observed many, many stars at all different stages of their lives. This makes it possible to assemble a complete sequence of steps and to test theoretical models.

Diff: 1 Section Ref: 10.4 82) Describe the helium flash and why it occurs.

Answer: When the core of a red giant has reached a temperature of 100 million K, helium fusion can occur. With helium fusion the temperature rises but the pressure does not because it is the electron degenerate pressure which is holding up the core and it is independent of the temperature. Increased pressure would expand the core and cool it but this does not happen. The increase in temperature makes the fusion occur faster, which raises the temperature more and produces a runaway explosion of fusion known as the helium flash.

Diff: 3 Section Ref: 10.5 83) How has the chemical composition of the core of the Sun changed in the past 4.5 billion years? Are earthlings (if any) likely to freeze in another 4-5 billion years? Explain.

Answer: The core of the Sun had an initial composition of 90% hydrogen and 9% helium. As hydrogen fusion has continued over the past 4.5 billion years the amount of helium produced has steadily increased. The center of the core now has about 85% helium and very little hydrogen. As a main sequence star the Sun will continue to brighten slowly. In another 4-5 billion years the Sun will have a core dominated by helium. This will force it to change into a red giant.

Therefore, the Sun will only continue to brighten over time and the Earth will only get hotter, never colder.

Diff: 3 Section Ref: 10.5

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84) In general, as stars go through the last stage of post-main sequence evolution they will lose mass in the process of settling down into their final state. Explain the mass-loss process and the final state of the star for a low mass star.

Answer: For a low mass star, the hydrogen fuel is exhausted and the star begins to fuse helium.

When this happens the star expands into a red giant. Eventually the helium is exhausted and the outer layers of the star are ejected as a planetary nebula, leaving a tiny, hot white dwarf behind.

Diff: 3 Section Ref: 10.5 85) What is the significance of 8 solar masses in stellar evolution?

Answer: Above 8 solar masses, a high mass star must go through a violent type II supernova core collapse, producing a neutron star or even a black hole for the most massive stars. Below that limit, a low mass star will shed enough mass in its giant and planetary nebula stages to avoid the core collapse, and eventually settle down into a white dwarf.

Diff: 2 Section Ref: 10.6

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 11 Stellar Explosions 1) Novae always occur in a close binary star system.

Answer: TRUE Diff: 1 Section Ref: 11.1 2) Unlike supernovae, novae can explode more than once, increasing their luminosity by thousands of times.

Answer: TRUE Diff: 1 Section Ref: 11.1 3) It takes less and less time to fuse heavier and heavier elements inside a high mass star.

Answer: TRUE Diff: 1 Section Ref: 11.2 4) Iron is the most stably bonded atomic nucleus.

Answer: TRUE Diff: 1 Section Ref: 11.2 5) A Type I supernova involves the collapsing core of a high mass star.

Answer: FALSE Diff: 1 Section Ref: 11.2 6) Because they all involve formation of iron in cores of massive stars, all type II supernovae are equally luminous.

Answer: FALSE Diff: 2 Section Ref: 11.2 7) Because they all involve the detonation of a carbon-rich white dwarf at Chandrasekhar's limit, all type I supernovae are equally luminous.

Answer: TRUE Diff: 2 Section Ref: 11.2 8) Novae are more closely related to type II than to type I supernovae.

Answer: FALSE Diff: 2 Section Ref: 11.2

1 ..

9) A carbon-detonation supernova starts out as a white dwarf in a close binary system.

Answer: TRUE Diff: 2 Section Ref: 11.2 10) The final core collapse of a massive star takes about 13 seconds.

Answer: FALSE Diff: 2 Section Ref: 11.2 11) Type II supernovae have little hydrogen in their spectra; it had been used up already.

Answer: FALSE Diff: 2 Section Ref: 11.2 12) A recurring nova could eventually explode as a Type I supernova.

Answer: TRUE Diff: 3 Section Ref: 11.2 13) The Crab Nebula and the Orion Nebula are regions where new stars are being formed.

Answer: FALSE Diff: 1 Section Ref: 11.3 14) A massive star can fuse only up to the element silicon in its core.

Answer: FALSE Diff: 1 Section Ref: 11.4 15) Except for hydrogen and most of the helium, all the elements have been formed through stellar nucleosynthesis.

Answer: TRUE Diff: 1 Section Ref: 11.4 16) Stellar nucleosynthesis is responsible for the existence of all elements except hydrogen.

Answer: FALSE Diff: 2 Section Ref: 11.4 17) Iron nuclei are the most tightly bound nuclei, which is why their production leads to type II supernovae.

Answer: TRUE Diff: 2 Section Ref: 11.4 2 ..

18) Once carbon is formed in massive star cores, the majority of nuclei formed form then on will belong to even numbered elements, due to addition to more helium nuclei as alpha particles.

Answer: TRUE Diff: 2 Section Ref: 11.4 19) Newly formed neutron stars have weak magnetic fields which strengthen over time, due to the conservation of angular momentum.

Answer: FALSE Diff: 1 Section Ref: 11.5 20) The density of a neutron star is comparable to the density of an atomic nucleus.

Answer: TRUE Diff: 2 Section Ref: 11.5 21) Like most pulsars, the Crab Nebula neutron star is known only by its radio pulses.

Answer: FALSE Diff: 2 Section Ref: 11.5 22) All neutron stars are pulsars, but not all pulsars are neutron stars.

Answer: FALSE Diff: 2 Section Ref: 11.5 23) Gamma-ray bursts seem to come primarily from neutron star binaries in the plane of our own Milky Way Galaxy.

Answer: FALSE Diff: 2 Section Ref: 11.6 24) Astronomers believe that gamma-ray bursters emit radiation equally in all directions.

Answer: FALSE Diff: 1 Section Ref: 11.6 25) Short duration gamma-ray bursts are explained as the merger of two neutron stars.

Answer: TRUE Diff: 2 Section Ref: 11.6

3 ..

26) Besides direct formation of a black hole in a hypernova, some think that mergers between neutron stars can create even longer-lived gamma ray bursts as well.

Answer: FALSE Diff: 3 Section Ref: 11.6 27) The spectra of the youngest stars show the most heavy elements present.

Answer: TRUE Diff: 2 Section Ref: 11.7 28) A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?

A) Hypernova B) Nova C) Gamma ray burstar D) Type I supernova E) Type II supernova Answer: B Diff: 1 Section Ref: 11.1 29) The Chandrasekhar mass limit is A) .08 solar masses.

B) .4 solar masses.

C) 1.4 solar masses.

D) 3 solar masses.

E) 8 solar masses.

Answer: C Diff: 2 Section Ref: 11.1 30) For a nova to occur, the system must have already been a A) astrometric binary.

B) detached binary.

C) spectroscopic binary.

D) mass-transfer binary.

E) eclipsing binary.

Answer: D Diff: 2 Section Ref: 11.1

4 ..

31) An iron core cannot support a star because A) iron is the heaviest element, and sinks upon differentiation.

B) iron has poor nuclear binding energy.

C) iron cannot fuse with other nuclei to produce energy.

D) iron supplies too much pressure.

E) iron is in the form of a gas, not a solid, in the center of a star.

Answer: C Diff: 1 Section Ref: 11.2 32) Beyond the formation of iron, nuclear energy can be produced only by A) fusion of still heavier elements.

B) ionization of the radioactive nuclei.

C) fission of heavy nuclei back toward lighter ones.

D) gravity.

E) the dark force.

Answer: C Diff: 1 Section Ref: 11.2 33) A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a A) day.

B) week.

C) month.

D) year.

E) century.

Answer: A Diff: 2 Section Ref: 11.2 34) The element with the most stable nucleus and smallest mass per particle is A) uranium.

B) argon.

C) helium.

D) hydrogen.

E) iron.

Answer: E Diff: 1 Section Ref: 11.2

5 ..

35) As a star's evolution approaches the Type II supernova, we find A) the heavier the element, the less time it takes to make it.

B) the heavier the element, the higher the temperature to fuse it.

C) helium to carbon fusion takes at least 100 million K to start.

D) photodisintegration of iron nuclei begins at 10 billion K to ignite the supernova.

E) All of the above are correct.

Answer: E Diff: 3 Section Ref: 11.2 36) The core of a highly evolved high mass star is a little larger than A) our solar system.

B) our Sun. C) Jupiter.

D) Earth.

E) a white dwarf.

Answer: D Diff: 3 Section Ref: 11.2 37) What would happen if mass is added to a 1.4 solar mass white dwarf?

A) The star would explode as a nova.

B) The star's radius would increase.

C) The star would immediately collapse into a black hole.

D) The star would erupt as a carbon detonation (type I) supernova.

E) The core would collapse as a type II supernova.

Answer: D Diff: 2 Section Ref: 11.2 38) A star can be a supernova A) in predictable cycles of decades.

B) a few times, at unpredictable intervals.

C) only if it can fuse iron in its core.

D) before it reaches the main sequence, if it is massive enough.

E) only once.

Answer: E Diff: 1 Section Ref: 11.2

6 ..

39) The supernova that formed M-1, the Crab Nebula, was observed in A) 1572 AD by Tycho Brahe.

B) 1604 AD by Johannes Kepler.

C) 1054 AD by Chinese and Middle Eastern astronomers.

D) 1006 by observers in the southern hemisphere.

E) about 9,000 BC by all our ancestors.

Answer: C Diff: 2 Section Ref: 11.3 40) The remains of type II supernovae (massive star, core collapse supernovae) are seen in the sky as A) nebulae that are shrinking as the central mass pulls them in.

B) nebulae that are expanding at thousands of kilometers per hour.

C) nebulae that are stellar nurseries.

D) white dwarfs.

E) white holes.

Answer: B Diff: 2 Section Ref: 11.3 41) Supernova remnants differ from star forming regions because, although there is ionized hydrogen in both, supernova remnants A) don't look like star forming regions.

B) are much bigger than star forming regions.

C) are located far from star forming regions.

D) are more diffuse than star forming regions.

E) contain no ionizing stars.

Answer: E Diff: 3 Section Ref: 11.3 42) Nearly all the elements found in nature were formed inside stars, EXCEPT for A) carbon and silicon.

B) hydrogen and helium.

C) helium and carbon.

D) silver and technetium.

E) uranium and radium.

Answer: B Diff: 1 Section Ref: 11.4

7 ..

43) What is stellar nucleosynthesis?

A) The formation of heavier elements inside stars B) The formation of planetary nebulae by red giants C) The formation of stars from a nucleus of contracting material D) The formation of white dwarfs, neutron stars, and black holes from stars E) The process by which stars form interstellar dust Answer: A Diff: 1 Section Ref: 11.4 44) The heaviest nuclei of all are formed A) by neutron capture during a type II supernova explosion.

B) during a nova explosion.

C) during a carbon detonation supernova.

D) during carbon burning in the giant stage.

E) during the triple alpha process.

Answer: A Diff: 2 Section Ref: 11.4 45) What direct evidence do astronomers have that supports the heavy element formation in stars?

A) The presence of technetium in giant star spectra B) Observed elemental abundances C) Gamma-ray emissions from decay of cobalt 56 in supernovae D) Light curves of type-I supernovae E) All of the above are evidence of this.

Answer: E Diff: 2 Section Ref: 11.4 46) Which type of heavy atomic nuclei are most common, and why?

A) Transuranium elements, for only very heavy elements are made in supernovae.

B) Odd numbered elements, because hydrogen is the building block for all heavier elements.

C) Even numbered elements, for helium is "giant food" for everything beyond itself.

D) Metals, for iron is the last abundant element formed before the type II supernova.

E) Noble gases, for they are the most stable elements.

Answer: C Diff: 2 Section Ref: 11.4

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47) The making of abundant iron nuclei is typical of A) planetary nebula ejection.

B) the helium flash.

C) all novae.

D) type I supernovae.

E) type II supernovae.

Answer: E Diff: 2 Section Ref: 11.4 48) The helium capture process tends to produce chiefly A) only carbon.

B) stable elements.

C) even numbered elements.

D) odd numbered elements.

E) only radioactive elements.

Answer: C Diff: 2 Section Ref: 11.4 49) What is the reason a type-I supernova slows its dimming after about 2 months?

A) The planetary nebula cooled enough to form a dust shell.

B) Energy is released from the decay of radioactive cobalt 56 to iron 56.

C) The supernova remnant suddenly becomes transparent.

D) The burst of energy carried by neutrinos is finally observed.

E) Energy from the supernova's shock wave is released as it hits interstellar matter.

Answer: B Diff: 2 Section Ref: 11.4 50) When helium capture occurs with a carbon 12 nucleus, what results?

A) Nitrogen 14 B) Oxygen 16 C) Neon 20 D) Silicon 28 E) Nickel 56 Answer: B Diff: 2 Section Ref: 11.4

9 ..

51) The iron we commonly find in our surroundings came from A) the iron core of a massive star which exploded as a type I supernova.

B) planetary nebulae.

C) jets ejected by a rapidly spinning pulsar.

D) material ejected by a nova explosion.

E) decay of nickel 56 and cobalt 56 in a supernova remnant.

Answer: E Diff: 2 Section Ref: 11.4 52) The heaviest nuclei of all are formed A) in the horizontal branch.

B) in dense white dwarfs.

C) during nova explosions.

D) in the ejection of matter in the planetary nebula.

E) in the core collapse that set the stage of Type II supernovae.

Answer: E Diff: 2 Section Ref: 11.4 53) Neutron stars and black holes are formed by A) the star formation process.

B) mass transfer in binary star systems.

C) novae.

D) type I supernovae.

E) type II supernovae.

Answer: E Diff: 1 Section Ref: 11.5 54) In a neutron star, the core is A) made of compressed neutrons in contact with each other.

B) electrons and protons packed so tightly they are in contact.

C) constantly expanding and contracting.

D) primarily iron and silicon.

E) no longer rotating.

Answer: A Diff: 1 Section Ref: 11.5

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55) Two important properties of young neutron stars are A) extremely slow rotation and a strong magnetic field.

B) extremely rapid rotation and a weak magnetic field.

C) extremely rapid rotation and a strong magnetic field.

D) no rotation and a weak magnetic field.

E) no rotation and no magnetic field.

Answer: C Diff: 1 Section Ref: 11.5 56) Neutron stars have A) very strong bi-polar magnetic fields.

B) weak or non-existent magnetic fields.

C) periods of days or weeks.

D) monopolar fields that switch polarity every rotation.

E) no relation to pulsars.

Answer: A Diff: 1 Section Ref: 11.5 57) An object more massive than the Sun, but roughly the size of a city, is a A) supernova remnant.

B) white dwarf.

C) brown dwarf.

D) neutron star.

E) red dwarf.

Answer: D Diff: 2 Section Ref: 11.5 58) The average density of neutron stars approaches A) a million times that of normal matter.

B) a million times that of even a white dwarf.

C) about 1017 kg/m3, similar to the density of atomic nuclei.

D) about 1018 times that of water.

E) infinity.

Answer: C Diff: 2 Section Ref: 11.5

11 ..

59) Pulsars A) spin very rapidly when they're young.

B) are the cause of gamma-ray bursts.

C) spin very slowly when they're young, and gradually spin faster as they age.

D) generally form from 25 solar mass stars.

E) emit radio in all directions.

Answer: A Diff: 2 Section Ref: 11.5 60) The vast majority of pulsars are known only from their pulses in A) X-rays.

B) gamma-rays.

C) visible light.

D) microwaves.

E) radio waves.

Answer: E Diff: 1 Section Ref: 11.5 61) What compelling evidence links pulsars to neutron stars?

A) Both pulsars and neutron stars can be found in globular star clusters.

B) Pulsars are known to evolve into neutron stars.

C) Only a small, very dense source could rotate that rapidly without flying apart.

D) Pulsars are always found in binary systems with neutron stars.

E) Both pulsars and neutron stars have been discovered near the Sun. Answer: C Diff: 1 Section Ref: 11.5 62) What makes the Crab pulsar somewhat unusual among pulsars in general?

A) It is the most intense source of X-rays in the sky.

B) It is the fastest pulsar known.

C) It is the oldest pulsar observed.

D) Its period is not regular like other pulsars.

E) It is rather bright at visible wavelengths.

Answer: E Diff: 2 Section Ref: 11.5

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63) What makes the Crab Nebula supernova remnant unusual as a supernova remnant?

A) It is the biggest supernova remnant visible.

B) It is the remnant of a supernova that was observed in the 20th century.

C) It is the nearest supernova remnant.

D) It is the oldest supernova remnant known.

E) It is the remnant of a supernova observed by humans.

Answer: E Diff: 2 Section Ref: 11.5 64) In the lighthouse model A) the star literally turns on and off like a lighthouse beacon.

B) all pulsars must have their poles pointed directly toward us.

C) if the beam sweeps across us, we will detect a pulse of radiation.

D) the period of pulsation must speed up as the neutron star continues collapsing.

E) the period of pulsation slows down due to the drag of the remnant on its field.

Answer: C Diff: 2 Section Ref: 11.5 65) In the lighthouse model A) pulsars are observable only if they lie in the galactic plane.

B) pulsars are navigational devices created by interstellar navigators as discovered by Jocelyn Bell in 1967.

C) all pulsars have their poles pointed directly at us or they would be not observable.

D) if the beams sweeps across us, we can observe the pulse.

E) the period of pulsation must speed up as the neutron star continues contracting.

Answer: D Diff: 2 Section Ref: 11.5 66) Whose work with SETI lead to the discovery of pulsars in 1967?

A) Jocelyn Bell B) Sir Bernard Lovell C) Anthony Hewish D) Martin Schwarzschild E) Stephen Hawking Answer: A Diff: 2 Section Ref: 11.5

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67) The supernova of 1054 AD produced A) a remnant still visible to the naked eye, the Crab Nebula, M-1.

B) a pulsar with a period of 33 milliseconds, visible optically.

C) the closest known neutron star to our Sun. D) the most famous black hole.

E) no remaining visible trace, as it was a type I supernova.

Answer: B Diff: 3 Section Ref: 11.5 68) Relatively long duration gamma-ray bursts are produced by A) novae.

B) supernovae.

C) hypernovae.

D) neutron star mergers.

E) black hole mergers.

Answer: C Diff: 2 Section Ref: 11.6 69) A hypernova creates A) a black hole.

B) a pulsar.

C) a neutron star.

D) short-duration gamma-ray bursts.

E) Both B and C are correct.

Answer: A Diff: 3 Section Ref: 11.6 70) Which statement about young stars is FALSE? A) They contain a larger fraction of heavy elements than previous generations.

B) They are born in a dustier environment than earlier generations.

C) They are more likely to have planets forming with them than earlier generations.

D) The high mass stars will be more likely to produce heavier elements as they evolve.

E) Being young, they will have more pure hydrogen than earlier generations.

Answer: E Diff: 3 Section Ref: 11.7

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71) Type II supernovae and star forming regions are related to one another because A) they both contain ionized hydrogen.

B) they both involve high mass ionizing stars.

C) the shock waves of a supernova can trigger star formation.

D) as a result of both processes, lighter elements are transformed into heavier elements.

E) all of the above.

Answer: E Diff: 3 Section Ref: 11.7 72) After reaching its peak luminosity in hours or days, a nova declines in brightness over a period of a few ________ before returning to its pre-explosion luminosity.

Answer: months Diff: 2 Section Ref: 11.1 73) In a nova, there is a white dwarf, an evolving companion star, and a(n) ________ surrounding the white dwarf's equator.

Answer: accretion disk Diff: 2 Section Ref: 11.1 74) Of all elements, ________ has the most stable and tightly bound nucleus.

Answer: iron Diff: 1 Section Ref: 11.2 75) An iron core will collapse in approximately one ________ in a type II supernova event.

Answer: second Diff: 2 Section Ref: 11.2 76) The maximum mass of a white dwarf is about ________ times the mass of the Sun. Answer: 1.4 Diff: 1 Section Ref: 11.2 77) Type I supernovae result from ________ stars which have accreted sufficient additional mass via mass transfer from a close binary companion.

Answer: white dwarf Diff: 2 Section Ref: 11.2

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78) The Crab Nebula is a bright, long lasting supernova remnant that was made by a ________ supernova.

Answer: type II Diff: 3 Section Ref: 11.3 79) The central star of the Crab Nebula has now collapsed into a ________, whose energy keeps this famous nebula visible even in binoculars.

Answer: pulsar Diff: 3 Section Ref: 11.3 80) The radioactive decay of cobalt 56 into iron 56 affects the light curve of a type I supernova about ________ after the initial peak in luminosity.

Answer: two months Diff: 3 Section Ref: 11.4 81) A gamma-ray burster emits a quantity of energy similar to that emitted in a ________.

Answer: supernova or supernova explosion.

Diff: 2 Section Ref: 11.6 82) If successive generations of stars return material back to the interstellar medium which is enriched in heavier elements, then we expect that old stars are ________ compared to younger stars.

Answer: poorer in metals Diff: 2 Section Ref: 11.7 83) What would be most likely to disrupt the normal evolution of a star? Give examples of this.

Answer: If it has a close companion, mass transfer may change the masses of both stars and greatly change the evolutionary tracks of both stars. Nova and Type I supernovae are both created by mass transfer changes.

Diff: 2 Section Ref: 11.1 84) Compare the amount of time a 20 solar mass star will stay on the main sequence to the length of time its iron core can exist.

Answer: A 20 solar mass star will stay on the main sequence for 10 million years. Its iron core can exist for only a day.

Diff: 2 Section Ref: 11.2

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85) Contrast the progenitors of a Type I and a Type II supernova.

Answer: The progenitor of a Type II supernova is a single massive star. The progenitor of a Type I supernova is a binary star system.

Diff: 2 Section Ref: 11.2 86) What is the importance of 1.4 solar masses in stellar evolution?

Answer: 1.4 solar masses is the Chandrasekhar Limit. While dwarfs less massive than Chandrasekhar's Limit can remain stable by gravitational contraction for billions of years; above that limit, electron degeneracy will fail to stop the contraction, and the white dwarf will blow up as a Type I supernova, or collapse to a neutron star in a Type II supernova.

Diff: 2 Section Ref: 11.2 87) Will our Sun become a supernova? Why? Answer: No, it is not in a close binary system to produce Type I events, and it is not nearly massive enough to go past formation of carbon as a low mass star.

Diff: 2 Section Ref: 11.2 88) What is the importance of 1.4 solar masses in stellar evolution?

Answer: 1.4 solar masses is the Chandrasekhar Limit. While dwarfs less massive than Chandrasekhar's Limit can remain stable by gravitational contraction for billions of years; above that limit, electron degeneracy will fail to stop the contraction, and the white dwarf will blow up as a Type I supernova, or collapse to a neutron star in a Type II supernova.

Diff: 2 Section Ref: 11.2 89) What are two differences observed between Type I and Type II supernovae?

Answer: Type I supernovae have very little hydrogen and their light curve drops off gradually but steadily. A Type II supernova is hydrogen rich and its light curve has a distinctive plateau where the luminosity remains constant for a time.

Diff: 3 Section Ref: 11.2 90) How do astronomers know that the Crab Nebula is the remains of a supernova?

Answer: Both Chinese and Arab records show a guest star in the location that matches the position of the Crab Nebula. Rewinding the motion of the Crab Nebula brings it to the central object at the right time to match the observations of Chinese and Arab astronomers in 1054.

Diff: 2 Section Ref: 11.3

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91) What is the only element in your body that was formed during the Big Bang, and not in cores of stars? Explain how you know this.

Answer: Hydrogen was formed during the Big Bang and not in stellar cores. In stellar cores, hydrogen is fused into heavier elements, so the hydrogen used is that which was formed in the Big Bang.

Diff: 1 Section Ref: 11.4 92) How are elements heavier than iron made? Why are they rare?

Answer: The elements heavier than iron are formed when protons and neutrons are crammed into nuclei making up the outer layers of massive stars as those layers are hurled into the interstellar medium during a supernova event.. These conditions do not last long, so there is very little time for the creation of these elements.

Diff: 2 Section Ref: 11.4 93) Under what circumstances will a nova occur?

Answer: When a white dwarf pulls mass off its companion in a mass-transfer binary. When this hydrogen shell reaches 10 million K, sudden proton-proton fusion generates the bright flash and rapidly expanding envelope we observe from Earth.

Diff: 1 Section Ref: 11.1 94) Can our Sun ever become a nova? Why? Answer: No, ours is a single star, with no close companion to supply fresh hydrogen via mass transfer onto the surface of our collapsed white dwarf Sun billions of years from now.

Diff: 1 Section Ref: 11.1 95) Why is the post-Main Sequence structure of a high mass star sometimes described by an "onion-layer" model? Explain.

Answer: Late in the evolution of massive stars, fusion reactions create cores within cores within cores, etc. Hydrogen fusion occurs in a layer around a layer of helium fusion which occurs around of layer of carbon fusion... around oxygen fusion... around neon fusion... etc. The deeper you go, the heavier elements you find made, and the higher the temperature needed to sustain that particular fusion reaction.

Diff: 2 Section Ref: 11.2 96) Why does conversion of its core to iron have to mark the end of a star's life? Which stars can end up with iron cores?

Answer: Stars with a total mass of 8 solar masses may form iron cores. The formation of an iron core ends the normal life of a star because iron cannot be fused into heavier elements and produce energy, as previous fusion reactions have done. In order to fuse iron, energy must be provided. The star, at this point in its evolution, has finally run out of energy sources in its core.

Diff: 2 Section Ref: 11.2 18 ..

97) Why does iron formation cause a high mass star to "have a heart attack"?

Answer: Iron is the most tightly bonded of all nuclei. Fusion reactions leading to its production release radiation pressure to resist gravity, but all heavier nuclei beyond iron will absorb energy in their formation, so without the radiation to keep it inflated, the core collapses rapidly.

Diff: 2 Section Ref: 11.2 98) Why should the youngest stars be made of the heaviest elements?

Answer: With each generation of supernova, the interstellar medium is showered with a larger abundance of the heavy elements forged in the giant cores and blown back into space with their explosions.

Diff: 1 Section Ref: 11.7 99) What role does the main sequence mass of the star play in the formation of heavy elements in the giant stage?

Answer: Basically the greater the mass of the atomic nucleus, the higher the temperature will be needed to forge it. This means more massive stars, with greater gravity to provide contractive energy at the core, will reach higher final temperatures and thus create larger amounts of heavy elements than less massive stars.

Diff: 2 Section Ref: 11.7 100) How does the death of one very massive star give birth to perhaps hundreds of smaller ones soon thereafter?

Answer: The more massive the star, the faster it evolves, and less time it has to leave its stellar nursery and dense molecular cloud. When it explodes while still close to this dense region, its shock wave will trigger compression and collapse of many smaller protostars all at once.

Diff: 2 Section Ref: 11.7 101) Looking at the elements that make up our world, which are the products of low versus high mass stars?

Answer: Much of the lighter material in the Earth's crust and our bodies, such as carbon, oxygen, and nitrogen, is the product of low mass stars and given off in planetary nebula, type I supernovae, and stellar winds around giants. But the denser elements of the mantle and core, especially silicon and iron, are delivered to the interstellar medium from the cores of high mass stars by violent type II supernovae.

Diff: 3 Section Ref: 11.7

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 12 Black Holes 1) The escape speed for a black hole's event horizon is the speed of light.

Answer: TRUE Diff: 1 Section Ref: 12.1 2) Any main sequence star over 25 solar masses will probably retain enough matter in its core after its type II supernova to make a black hole.

Answer: TRUE Diff: 2 Section Ref: 12.1 3) The Schwarzschild radius of a black hole is about 3 km per solar mass; it is amazingly linear over a wide range of masses.

Answer: TRUE Diff: 2 Section Ref: 12.1 4) Special relativity says that c, the speed of light, is the maximum velocity for both matter and energy in our universe.

Answer: TRUE Diff: 1 Section Ref: 12.2 5) Only neutrinos can go faster than the speed of light.

Answer: FALSE Diff: 1 Section Ref: 12.2 6) An object increases in mass if it is moving rapidly compared to the observer.

Answer: TRUE Diff: 2 Section Ref: 12.2 7) An accelerating frame of reference cannot be distinguished from a gravitational field.

Answer: TRUE Diff: 2 Section Ref: 12.3 8) According to general relativity, objects moved on curved paths due to the force of gravity.

Answer: FALSE Diff: 2 Section Ref: 12.3

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9) Einstein received the Nobel Prize in physics for his work with general relativity.

Answer: FALSE Diff: 1 Section Ref: 12.3 10) Special relativity predicts that light bends near dense objects.

Answer: FALSE Diff: 2 Section Ref: 12.4 11) The curvature of spacetime around a black hole is so extreme that outward-going signals cannot escape.

Answer: TRUE Diff: 2 Section Ref: 12.4 12) Black holes suck up all matter in sight.

Answer: FALSE Diff: 1 Section Ref: 12.5 13) If something falls into a black hole, it remains intact until it reaches the event horizon.

Answer: FALSE Diff: 1 Section Ref: 12.5 14) Material that falls into a black hole can be seen by the electromagnetic radiation it emits before it reaches the event horizon.

Answer: TRUE Diff: 2 Section Ref: 12.5 15) The singularity of a black hole is where general relativity predicts the density to become infinite.

Answer: TRUE Diff: 1 Section Ref: 12.5 16) The energy from the accretion disk around a black hole would show gravitational red shift due to its immense gravity and tidal distortion of space there.

Answer: TRUE Diff: 2 Section Ref: 12.6

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17) Very rapid time variations help establish the tiny size of many X-ray sources, showing they must be collapsed objects of some kind.

Answer: TRUE Diff: 2 Section Ref: 12.6 18) Black holes with masses greater than a million solar masses explain the extremely rapidly moving stars and gas in the cores of galaxies.

Answer: TRUE Diff: 2 Section Ref: 12.6 19) Which of the following can actually escape from inside a black hole's event horizon?

A) Neutrinos B) Electrons C) Very high energy gamma-rays D) Protons E) None of the above Answer: E Diff: 2 Section Ref: 12.1 20) The mass range for neutron stars is A) .08 to .4 solar masses.

B) .4 to 3 solar masses.

C) 1.4 to 3 solar masses.

D) 3 to 8 solar masses.

E) 6 to 11 solar masses.

Answer: C Diff: 2 Section Ref: 12.1 21) The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is A) less than 1.0 solar masses.

B) greater than Schwartzschild's limit of 3 solar masses.

C) Chandrasekhar's limit of 1.4 solar masses.

D) between 1.4 and 2.0 solar masses.

E) greater than 25 solar masses.

Answer: B Diff: 3 Section Ref: 12.1

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22) The Schwartzschild radius for a 12 solar mass star is A) 4 km.

B) 15 km.

C) 36 km.

D) 100 km.

E) 3000 km.

Answer: C Diff: 3 Section Ref: 12.1 23) How are the event horizon and Schwarzschild radius related?

A) The Schwarzschild radius is smaller than the distance from the singularity of a black hole to the event horizon.

B) The Schwarzschild radius is equal to the distance from the singularity of a black hole to the event horizon.

C) The Schwarzschild radius is greater than the distance from the singularity of a black hole to the event horizon.

D) The size of the Schwarzschild radius is unrelated to the distance from the singularity of a black hole to the event horizon.

E) The size of the Schwarzschild radius is proportional to the distance from the singularity of a black hole to the event horizon.

Answer: B Diff: 1 Section Ref: 12.1 24) What explanation does general relativity provide for gravity?

A) Gravity is the result of curved spacetime.

B) Gravity is directly proportional to the mass of the attracting body.

C) Gravity is inversely proportion to the radius of the body.

D) Gravity is the opposite of the electromagnetic force.

E) Gravity can affect only massive particles, not massless photons.

Answer: A Diff: 2 Section Ref: 12.2 25) An observer on a planet sees a spaceship approaching at 0.5c. A beam of light projected by the ship would be measured by this observer to travel at A) 0.25c.

B) 0.5c.

C) c.

D) 1.5c.

E) 2.5c.

Answer: C Diff: 2 Section Ref: 12.2

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26) As a spaceship's velocity gets closer to the speed of light A) its length will increase and its clock will run more slowly.

B) its length will decrease and its clock will run faster.

C) its length will increase and its clock will run faster.

D) its length will decrease and its clock will run more slowly.

E) None of these will happen.

Answer: D Diff: 2 Section Ref: 12.2 27) In a vacuum, which form of electromagnetic radiation travels slowest?

A) Visible light B) Radio C) Gamma rays D) Ultraviolet light E) All forms of electromagnetic radiation travel at the same speed.

Answer: E Diff: 2 Section Ref: 12.2 28) When observing an object, such as a space ship that is moving very quickly relative to you, the length of objects on that object will appear to be A) longer than when they are at rest.

B) the same length as when they are at rest.

C) shorter than when they are at rest.

D) narrower than when they are at rest.

E) wider than when they are at rest.

Answer: C Diff: 2 Section Ref: 12.2 29) As a spaceship nears an event horizon, a clock on the spaceship will be observed A) to run faster.

B) to stop.

C) to run slowly.

D) to run backwards.

E) to run the same as one on Earth.

Answer: C Diff: 2 Section Ref: 12.2

5 ..

30) The equivalence principle says that a person in an elevator that is in freefall feels the same acceleration as A) a person in an elevator going up with an acceleration of g.

B) a person in space, far from any gravitational source accelerating at g.

C) a person in an elevator going down with an acceleration of g.

D) a person in space, far away from any gravitational source with no acceleration.

E) a person in orbit of Earth accelerating at g upward.

Answer: B Diff: 3 Section Ref: 12.3 31) What explanation does general relativity provide for gravity?

A) Gravity is the result of curved spacetime.

B) Gravity is directly proportional to the mass of the attracting body.

C) Gravity is inversely proportion to the radius of the body.

D) Gravity is the opposite of the electromagnetic force.

E) Gravity can affect only massive particles, not massless photons.

Answer: A Diff: 2 Section Ref: 12.3 32) The equivalence principle says that a person in an elevator that is in freefall feels the same acceleration as A) a person in an elevator going up with an acceleration of g.

B) a person in space, far from any gravitational source accelerating at g.

C) a person in an elevator going down with an acceleration of g.

D) a person in space, far away from any gravitational source with no acceleration.

E) a person in orbit of Earth accelerating at g upward.

Answer: B Diff: 3 Section Ref: 12.3 33) If light from a distant star passes close to a massive body, the light beam will A) bend towards the star due to gravity.

B) continue moving in a straight line.

C) change color to a shorter wavelength.

D) slow down.

E) accelerate due to gravity.

Answer: A Diff: 3 Section Ref: 12.3

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34) What can we detect from matter that has crossed an event horizon?

A) Gamma-ray bursts B) Radio waves if the matter was traveling fast enough C) Visible light D) X-rays if the matter was dense E) Nothing Answer: E Diff: 1 Section Ref: 12.3 35) Einstein earned the Nobel Prize for his A) special theory of relativity.

B) general theory of relativity.

C) development of the equivalence of energy and matter, E = mc2.

D) work on the particle nature of light.

E) contributions to the development of the fission bomb.

Answer: D Diff: 2 Section Ref: 12.3 36) Which of the following are attracted by gravity?

A) Antimatter B) Any object with mass C) Dlectromagnetic radiation D) Neutrinos E) All of the above Answer: E Diff: 2 Section Ref: 12.3 37) The observed slowing of a clock in the vicinity of a black hole is a prediction of A) the Roche Limit.

B) Special relativity.

C) General relativity.

D) Stellar nucleosynthesis.

E) the Cosmological Principle.

Answer: C Diff: 2 Section Ref: 12.3

7 ..

38) What explanation does general relativity provide for gravity?

A) Gravity is the result of curved spacetime.

B) Gravity is directly proportional to the mass of the attracting body.

C) Gravity is inversely proportion to the radius of the body.

D) Gravity is the opposite of the electromagnetic force.

E) Gravity can affect only massive particles, not massless photons.

Answer: A Diff: 2 Section Ref: 12.4 39) If light from a distant star passes close to a massive body, the light beam will A) bend towards the star due to gravity.

B) continue moving in a straight line.

C) change color to a shorter wavelength.

D) slow down.

E) accelerate due to gravity.

Answer: A Diff: 3 Section Ref: 12.4 40) If the Sun were replaced by a one solar mass black hole A) all terrestrial planets would fall in immediately.

B) we would still orbit it in a period of one year.

C) we would immediately escape into deep space, driven out by its radiation.

D) our clocks would all stop.

E) life here would be unchanged.

Answer: B Diff: 3 Section Ref: 12.4 41) On the surface of a sphere the shortest distance between two points is A) an arc on a great circle.

B) a straight line.

C) a circle.

D) a triangle.

E) a curvy line.

Answer: A Diff: 3 Section Ref: 12.4

8 ..

42) Why do scientists describe the theory of gravity as "incomplete"?

A) It does not incorporate a description of matter on a very small scale.

B) It does not explain why light bends near a dense object.

C) It does not agree with the expansion of the universe.

D) The gravity waves it predicts have not been observed.

E) It does not explain the effects on time from a massive object.

Answer: A Diff: 2 Section Ref: 12.4 43) If a specially designed space probe reaches the event horizon of a black hole, an observer watching the clock on this probe from a safe distance would see A) the clock slow down.

B) the clock speed up.

C) the clock keep time in sync with the observer's clock.

D) the time on the clock would appear to change randomly.

Answer: A Diff: 1 Section Ref: 12.5 44) As a spaceship approaches the event horizon of a black hole, its radio transmissions would A) be sucked into the black hole.

B) shifted to infrared or even visible light.

C) shifted to longer wavelength.

D) increase in amplitude.

E) be unchanged.

Answer: C Diff: 2 Section Ref: 12.5 45) If the Sun were to magically and instantaneously be replaced by a 1 solar mass black hole, what would happen to the Earth's orbit?

A) It would be unchanged.

B) It would be much smaller, but its shape would be unchanged.

C) It would be at the same distance from the Sun, but would be much more eccentric.

D) It would be much larger, but its shape would be unchanged.

E) The Earth would be pulled into the black hole and destroyed.

Answer: A Diff: 2 Section Ref: 12.5

9 ..

46) What happens to the light that is emitted from the accretion disk around a black hole?

A) It is redshifted.

B) It is blueshifted.

C) It is pulled in multiple directions by tides.

D) It cannot be seen from anywhere in our solar system.

E) It is absorbed by the black hole.

Answer: A Diff: 1 Section Ref: 12.5 47) The singularity of a black hole is A) where general relativity predicts the density to be zero.

B) where the current understanding of gravity is incomplete.

C) the point at which nothing, not even light, can escape.

D) the region between the Schwarzschild Radius and the event horizon.

Answer: B Diff: 2 Section Ref: 12.5 48) What is Cygnus X-1?

A) The brightest star in the constellation Cygnus B) The leading candidate for an observable black hole binary system C) The strongest X-ray eclipsing binary system in the sky D) A millisecond pulsar with three Earth-like planets around it E) The first gamma-ray burster to be spotted in other wavelengths as well Answer: B Diff: 1 Section Ref: 12.6 49) The key to identifying a black hole candidate in a binary system is that A) one of the two stars cannot be seen.

B) the unseen companion in the system must have a sufficiently high mass.

C) the unseen star is a contact binary.

D) the system must be a very strong source of radio emissions.

E) the visible companion must be an evolving main sequence or giant star.

Answer: B Diff: 2 Section Ref: 12.6

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50) A method for identifying a black hole is to A) look for voids in the star fields.

B) look for their effects on nearby companions.

C) locate a visible star that disappears when the black hole passes in front of it.

D) search for radio waves from the accretion disk.

E) search for their pulsar signal.

Answer: B Diff: 2 Section Ref: 12.6 51) The largest known black holes A) create the dark nebulae in the plane of the Milky Way. B) can be no more than 1.4 solar masses, according to Chandrasekhar.

C) lie in the cores of the most massive galaxies.

D) can be no bigger than a small city, just like neutron stars.

E) can be no bigger than the Earth, like white dwarfs.

Answer: C Diff: 2 Section Ref: 12.6 52) Which of the following is NOT an argument for Cygnus X-1's being a true black hole?

A) Spectroscopic data suggests hot gas is flowing from the companion B star onto Cygnus X-1.

B) The mass of the visible B star is even greater than Cygnus X-1, at around 25 solar masses.

C) Cygnus X-1's mass is estimated to be about 10 solar masses.

D) X-rays from Cygnus X-1 vary on time scales as short as a millisecond.

E) X-ray observations around the object support a temperature of several million K. Answer: B Diff: 3 Section Ref: 12.6 53) In M82, observations indicate that there are several bright sources close to the center of the galaxy. These might be A) supernovae.

B) accretion disks of supermassive black holes, millions of times as massive as our sun.

C) accretion disks of intermediate black holes, hundreds of times as massive as our sun.

D) accretion disks of stellar mass black holes.

E) red giants in the process of forming planetary nebulae.

Answer: C Diff: 2 Section Ref: 12.6 54) If a neutron star attains a mass over ________ solar masses it becomes a black hole.

Answer: three Diff: 1 Section Ref: 12.1

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55) If a spaceship travels near the speed of light away from the Earth, an observer on Earth would see the length of the spaceship ________.

Answer: shrink Diff: 1 Section Ref: 12.2 56) In 1921, the Nobel Prize in physics was awarded to ________ for his work on the particle nature of light.

Answer: Albert Einstein Diff: 1 Section Ref: 12.3 57) On a sphere, the interior angles of a triangle add up to ________ 180 degrees.

Answer: less than Diff: 2 Section Ref: 12.4 58) General relativity explains gravity as the ________ of spacetime.

Answer: curvature Diff: 1 Section Ref: 12.4 59) A ________ is a place where the current rules fall apart in science.

Answer: singularity Diff: 2 Section Ref: 12.5 60) Something falling into a black hole will be ________ by tides.

Answer: pulled apart Diff: 2 Section Ref: 12.5 61) The current theories of gravity are ________ because they do not incorporate a proper description of matter on the smallest scale.

Answer: incomplete Diff: 1 Section Ref: 12.5 62) A black hole may be visible because electromagnetic radiation is emitted from an ________ surrounding it, heated up enough to emit X-rays.

Answer: accretion disk Diff: 1 Section Ref: 12.6

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63) Relate escape velocity to the event horizon.

Answer: At the event horizon around a black hole, the escape velocity is equal to the speed of light, so that no matter or energy can escape from inside.

Diff: 2 Section Ref: 12.1 64) How is the Schwartzschild radius calculated?

Answer: The Schwartzschild radius is roughly 3 km times the mass of the star in solar masses.

Diff: 3 Section Ref: 12.1 65) What happens to the size and mass of an object as it moves faster?

Answer: A faster object's mass increases and length increases.

Diff: 2 Section Ref: 12.2 66) Special relativity says that time is a separate ________ in the workings of the universe.

Answer: dimension Diff: 2 Section Ref: 12.3 67) To explain gravity, general relativity says that matter tends to ________ space in its vicinity.

Answer: curve Diff: 2 Section Ref: 12.4 68) If you were to fall into a black hole, the ________ would kill you by tearing you apart.

Answer: tidal forces Diff: 2 Section Ref: 12.5 69) Light from an object near the event horizon received by a distant observer is ________.

Answer: redshifted Diff: 1 Section Ref: 12.5 70) How can a black hole of a few solar masses be detected?

Answer: Look for a binary system in which one body is not visible conventionally but is a strong X-ray source from mass transfer off the visible companion, and has mass over 3 solar masses, as revealed by the motion of the visible companion.

Diff: 2 Section Ref: 12.6

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71) Relate escape speed to event horizon for a black hole.

Answer: The escape speed allows an object moving fast enough to overcome the gravity of a body and escape into space. But for very massive black holes, if you are so close as to be within the event horizon, now this speed is greater even than c, the speed of light, so neither matter nor even energy can escape the gravity of the black hole.

Diff: 1 Section Ref: 12.1 72) What are the three possible outcomes of stellar evolution? Describe each possibility, differentiating their means of formation and their subsequent properties. Which stars on the Main Sequence are thought to end up in each of these forms?

Answer: If less than 1.4 solar masses the final stage of a star's life will be a white dwarf. This forms as a remnant of a red giant which has blown off a planetary nebula. At 1.4 to 3 solar masses, the remnant will be a neutron star. This is generally the result of a Type II supernova explosion. Above three solar masses, the collapse produces a black hole.

Diff: 2 Section Ref: 12.1 73) Explain how the essential features of special relativity imply that a beam of light from a fast moving spaceship will always be observed to moving at the speed of light.

Answer: The essential features are: The laws of physics are the same everywhere, there is no absolute motion, and time is a separate dimension. In order for the laws of physics to be the same everywhere, the speed of light is a constant of nature. That means that it will always be the same independent of the motion of the source or observer.

Diff: 3 Section Ref: 12.2 74) Describe the properties of space in the vicinity of a black hole.

Answer: The geometry of space is warped or curved near a black hole. The gravitational field is so overwhelmingly large that the curvature of space is extreme, so extreme that space folds over on itself at the event horizon. Further away from the black hole, gravity from it is weaker and the curvature of space is less.

Diff: 3 Section Ref: 12.4 75) Why is the light from near a black hole redshifted?

Answer: The gravity is great enough to decrease the energy of the escaping photons and thus increase their observed wavelength.

Diff: 2 Section Ref: 12.4 76) Why would the tidal forces around a black hole be of concern to a space explorer interested in investigating the area near a black hole?

Answer: The difference in gravity between the explorer's head and feet (if he or she is oriented vertically) would stretch the explorer, eventually tearing the explorer apart.

Diff: 2 Section Ref: 12.5 14 ..

77) What is some of the evidence that Cygnus X-1 is a black hole?

Answer: The mass of the invisible object, based on Kepler's Laws, is about 10 solar masses, well over the 3 solar mass limit on a neutron star. The electromagnetic radiation varies over milliseconds, indicating that the area emitting the radiation is comparable in size to a football field. The temperature indicated by the x-ray emission indicates millions of kelvins, consistent with an accretion disk around a black hole.

Diff: 2 Section Ref: 12.6

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 13 The Milky Way Galaxy 1) The Milky Way we see in the sky is simply our edge-on view of our home Galaxy.

Answer: TRUE Diff: 1 Section Ref: 13.1 2) The Earth lies close to the center of the Galaxy.

Answer: FALSE Diff: 2 Section Ref: 13.1 3) From Earth, the center of the Milky Way lies in the direction of the constellation Cygnus.

Answer: FALSE Diff: 1 Section Ref: 13.1 4) Our Milky Way Galaxy is now known to be quite similar to the nearby Andromeda Galaxy, M-31.

Answer: TRUE Diff: 2 Section Ref: 13.1 5) Shapley found that globular clusters are only found in the Galactic bulge.

Answer: FALSE Diff: 1 Section Ref: 13.2 6) A pulsating variable star with a period of 10 days would be a Cepheid.

Answer: TRUE Diff: 2 Section Ref: 13.2 7) Henrietta Leavitt first showed the relationship between the mass and luminosity of Cepheids and their period of pulsation; the brighter, the longer this period.

Answer: TRUE Diff: 2 Section Ref: 13.2 8) Shapley found the Sun is located about half way out the disc from the center of the disk of the Galaxy.

Answer: TRUE Diff: 2 Section Ref: 13.2

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9) Stars in the Galactic disk came billions of years before stars in the Galactic halo.

Answer: FALSE Diff: 1 Section Ref: 13.3 10) In our vicinity, the Galactic disk is about 100 times wider than it is thick.

Answer: TRUE Diff: 2 Section Ref: 13.3 11) Most astronomers believe that the stars in the Galactic halo formed in dwarf galaxies or during the merger of these dwarf galaxies.

Answer: TRUE Diff: 2 Section Ref: 13.4 12) The infall of material in the Galactic halo to the Galactic disk stopped shortly after the formation of globular clusters.

Answer: FALSE Diff: 2 Section Ref: 13.4 13) Spiral arms are regions of star formation, which accounts for their blue color.

Answer: TRUE Diff: 1 Section Ref: 13.5 14) It is harder to map the structure of the Milky Way as a whole in visible light than with any other form of electromagnetic radiation.

Answer: TRUE Diff: 2 Section Ref: 13.5 15) The rotation curve for our Galaxy shows stars beyond the Sun moving slower than expected.

Answer: FALSE Diff: 1 Section Ref: 13.6 16) The majority of the mass of the Milky Way lies farther out than the Sun's orbit.

Answer: TRUE Diff: 1 Section Ref: 13.6 17) The core of the Milky Way, Sagittarius A, is a strong radio source in the sky.

Answer: TRUE Diff: 1 Section Ref: 13.7 2 ..

18) Motions of objects near our Galaxy's core suggest the central black hole is about 3.7 billion solar masses.

Answer: FALSE Diff: 2 Section Ref: 13.7 19) In structure, our Milky Way is most similar to A) the Large Magellanic Cloud.

B) an upscale version of a globular cluster.

C) M-31, the Andromeda Galaxy.

D) the Orion nebula.

E) none of these.

Answer: C Diff: 1 Section Ref: 13.1 20) The part of the Milky Way we are most familiar with is the A) Corona.

B) Galactic Disk.

C) Galactic halo.

D) Galactic Bulge.

E) Galactic center.

Answer: B Diff: 2 Section Ref: 13.1 21) For what type of object is the period-luminosity relation used for determining distances?

A) RR Lyrae variables B) T Tauri variables C) Cepheids D) Cataclysmic variables E) Planetary nebulae Answer: C Diff: 1 Section Ref: 13.2 22) It was the distribution of ________ that showed Harlow Shapley we were nowhere near the center of the Milky Way early in the 20th century.

A) planetary nebulae B) emission nebulae C) open clusters D) globular clusters E) supernova remnants Answer: D Diff: 1 Section Ref: 13.2 3 ..

23) The location of the Galactic center was first found by Harlow Shapley with A) radio emissions from Sagittarius A. B) Cepheids of population I in the spiral arms.

C) RR Lyrae variables in the globular clusters.

D) planetary nebulae in the open clusters.

E) infrared observations of the heat from its accretion disk around the black hole.

Answer: C Diff: 2 Section Ref: 13.2 24) The period-luminosity relation is critical in finding distances with A) RR Lyrae stars.

B) trigonometric parallaxes.

C) spectroscopic parallaxes.

D) Cepheid variables.

E) pulsars.

Answer: D Diff: 2 Section Ref: 13.2 25) Which is the correct description of the Sun's location within the Milky Way? A) At the outer edge of the Galactic bulge but in the plane of the disc B) In the disc but at its outer edge C) As Herschel found, very close to the Galactic center D) Above the disc and about one-third of the Galactic radius from the center E) In the disc and about one-half a Galactic radius from the center Answer: E Diff: 2 Section Ref: 13.2 26) Harlow Shapley found the Milky Way was A) centered on the Earth.

B) much smaller than previously thought.

C) rapidly expanding.

D) much larger than previously thought.

E) uniformly spherical in shape.

Answer: D Diff: 2 Section Ref: 13.2

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27) Galactic disks appear blue because A) they contain no G, K, or M dwarfs.

B) they contain only blue reflection nebulae.

C) dust obscures the longer, red, wavelengths.

D) O and B blue giants are much brighter than G, K, or M dwarfs.

E) dark matter gravitationally shifts all wavelengths towards the blue.

Answer: D Diff: 2 Section Ref: 13.2 28) The period-luminosity relation for Cepheid variables was discovered in 1908 by A) William Herschel.

B) Henrietta Leavitt.

C) Harlow Shapley.

D) Heber Curtiss.

E) Edwin Hubble.

Answer: B Diff: 3 Section Ref: 13.2 29) Most of the new star formation in the Galaxy is found in the A) halo.

B) spiral arms.

C) bulge.

D) Galactic center.

E) globular clusters.

Answer: B Diff: 1 Section Ref: 13.3 30) Matter belonging to the Galaxy can be traced out to ________ from the center.

A) 5 kpc B) 8 kpc C) 15 kpc D) 50 kpc E) 200 kpc Answer: D Diff: 2 Section Ref: 13.3

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31) The orbits of halo and bulge stars have been compared to A) planets around the Sun. B) satellites around planets.

C) comets around the Sun. D) binary stars.

E) the accretion disc around a black hole.

Answer: C Diff: 2 Section Ref: 13.3 32) From the Sun, the distance to the Galactic center is about A) 8 pc.

B) 8,000 pc.

C) 100,000 pc.

D) 225 million pc.

E) 100 billion pc.

Answer: B Diff: 2 Section Ref: 13.1 33) The Galactic Year is the time for our solar system to orbit the Galaxy; it is about A) 15 million years.

B) 225 million years.

C) 4.5 billion years.

D) 9.6 billion years.

E) 13.5 billion years.

Answer: B Diff: 2 Section Ref: 13.3 34) Detailed measurements of the disk and central bulge region of our Galaxy suggest our Milky Way is a A) dwarf galaxy.

B) spiral galaxy.

C) very flat elliptical galaxy.

D) very dusty irregular galaxy.

E) quasar.

Answer: B Diff: 2 Section Ref: 13.3

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35) Which is the correct description for the Sun's location in the Galaxy?

A) At the outer edge of the bulge, but along the Galactic equator B) About 30,000 ly out in the halo C) At the very outer edge of the disk, but in the Galactic plane D) In the disk near the Galactic center E) In the disk, and about half way out from the center Answer: E Diff: 2 Section Ref: 13.3 36) Which of these is NOT typical of the Galaxy's spiral arms?

A) Hot, young blue stars B) Emission nebulae like M42 C) O and B stars D) Open clusters E) Old giant stars like orange Arcturus Answer: E Diff: 2 Section Ref: 13.3 37) From Earth, the view of the Milky Way is a thin band of stars across the night sky. The part of the Milky Way galaxy that is described here is the A) bulge.

B) spiral arm.

C) disk.

D) halo.

E) globular cluster.

Answer: C Diff: 2 Section Ref: 13.3 38) In the halo, we do NOT find A) tidal streams.

B) globular clusters.

C) small satellite galaxies.

D) spiral arms.

E) old white dwarfs.

Answer: D Diff: 2 Section Ref: 13.3

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39) The "aspect ratio" of thickness to width of the Galactic disk is about A) 1:2.

B) 1:5.

C) 1:10.

D) 1:100.

E) 1:1,000.

Answer: D Diff: 3 Section Ref: 13.3 40) Star formation ceased first in the A) nucleus.

B) spiral arms.

C) bulge.

D) halo.

E) Galactic disk.

Answer: D Diff: 1 Section Ref: 13.4 41) In the formation of our Galaxy, the ________ formed first.

A) Galactic disk B) Galactic center C) globular clusters D) planetary nebulae E) spiral arms Answer: C Diff: 2 Section Ref: 13.4 42) Which sequence of formation by age is correct, oldest to youngest?

A) Dark nebulae, planetary nebulae, emission nebulae B) Spiral arms, bulge, halo C) Halo, spiral arms, globular clusters D) Globular clusters, emission nebulae, open clusters Answer: D Diff: 3 Section Ref: 13.4

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43) What use are 21 cm radio waves to Galactic astronomers?

A) They cut through the dusty cocoons to let us watch star birth.

B) We can reflect them off the core of the Galaxy.

C) Their Doppler shifts let us map the motions and locations of gas in the spiral arms.

D) They bounce off stars like our Sun to let us precisely measure their distances.

E) They pick up the cool, dark matter much better than can optical telescopes.

Answer: C Diff: 2 Section Ref: 13.5 44) Density waves may explain A) the lack of blue stars in the halo.

B) the random orbits of halo stars.

C) the density of red stars in the bulge.

D) the spiral arm structure of the Galaxy.

E) the large number of open clusters in the halo.

Answer: D Diff: 2 Section Ref: 13.5 45) The leading explanation for the existence of spiral arms is A) shock waves from cyclic supernovae explosions.

B) shock wave from the quasar-like eruption of the Galactic core.

C) passages of spiral density waves through the interstellar medium.

D) passages of massive globular clusters through the Galactic plane.

E) tidal streams of small galaxies being torn up by our monster Galaxy.

Answer: C Diff: 2 Section Ref: 13.5 46) Which of the following is most like the rotation of stars in the disk of the Milky Way? A) A DVD in a player B) The planets in our solar system C) Cars moving at a constant speed on a circular race track D) The hands of an analog clock E) The tire of a car moving Answer: C Diff: 2 Section Ref: 13.6

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47) What two observations allow us to calculate the Galaxy's mass?

A) The Sun's mass and velocity in orbit of the Galactic center B) The Sun's age and period of the Galactic Year C) The Sun's orbital velocity and its distance from the Galactic center D) The Sun's mass and its age E) The Sun's composition and luminosity Answer: C Diff: 2 Section Ref: 13.6 48) What observations suggest the mass of the Galaxy goes much farther out than its visible disc?

A) 21 cm maps of the spiral arms B) The rotation curve of the outermost portions of the disc C) The orbits of the open clusters in the disc D) Infrared observations of distant brown dwarfs E) X-ray images of other galaxies' discs from Chandra Answer: B Diff: 2 Section Ref: 13.6 49) Between us and the Galactic center, the Milky Way has a mass of A) several hundred thousand suns.

B) one to two million suns.

C) 250 million suns.

D) 100 billion suns.

E) over a trillion suns.

Answer: D Diff: 2 Section Ref: 13.6 50) Which method relies on the mass of a dark object revealing its presence?

A) Asteroidal occultations B) Ring occultations C) Stellar eclipses D) Temporary brightening of a distant star by a gravity lens E) Pulsars slowing down irregularly Answer: D Diff: 2 Section Ref: 13.6

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51) Most of the mass of the Milky Way seems to exist in the form of A) young stars in the disk.

B) old stars in the Galactic halo.

C) hydrogen gas in the disk and spiral arms.

D) dark matter out in the Galactic halo.

E) the black hole in the Galactic center.

Answer: D Diff: 2 Section Ref: 13.6 52) Using an orbit size of 8 kpc, and a period of 225 million years, the mass of our Galaxy is found to be closest to A) 106 solar masses.

B) 108 solar masses.

C) 1010 solar masses.

D) 1011 solar masses.

E) 1012 solar masses.

Answer: D Diff: 3 Section Ref: 13.6 53) The radio source ________ is located in a place consistent with the center of our Galaxy.

A) Cygnus X-1 B) 3C 273 C) 47 Tucanae D) M-8, the Lagoon Nebula E) Sgr A* Answer: E Diff: 2 Section Ref: 13.7 54) Our solar system is in the Galactic ________ of the Milky Way Galaxy.

Answer: disk Diff: 2 Section Ref: 13.1 55) Henrietta Leavitt's period-luminosity relation for ________ indicates that longer periods mean more luminosity.

Answer: Cepheid variables Diff: 1 Section Ref: 13.2 56) In age, Galactic disk stars are typically much ________ than those of the Galactic halo.

Answer: younger Diff: 1 Section Ref: 13.3 11 ..

57) In the solar neighborhood we can map the position of spiral arms by observation of objects that are determined to be relatively ________ in age.

Answer: young Diff: 1 Section Ref: 13.5 58) The major problem faced by optical astronomers in trying to deduce the structure of the Milky Way Galaxy is that we can see only a small part of it because of the ________.

Answer: interstellar dust Diff: 1 Section Ref: 13.5 59) Spiral arms are thought to be sites of ________, based on the observations newly formed stars and interstellar dust lanes in and around these features.

Answer: star formation Diff: 1 Section Ref: 13.5 60) The spiral structure of the Milky Way is best revealed by ________ cm radio observations of hydrogen atoms.

Answer: 21 Diff: 2 Section Ref: 13.5 61) Although astronomers refer to the Galaxy's disk as rotating, the motion is really due to the ________ motion of each of the objects in the disk.

Answer: orbital Diff: 1 Section Ref: 13.6 62) We can estimate the mass of the Galaxy from observations of its ________ curve.

Answer: rotation Diff: 2 Section Ref: 13.6 63) The Galactic center in ________ is best studied using radio and infrared observations.

Answer: Sagittarius Diff: 1 Section Ref: 13.7 64) Describe our location in the Milky Way. Answer: We lie in a spiral arm about 25,000 ly (8 kpc) out from the Galactic center, and in the disk of the galaxy.

Diff: 1 Section Ref: 13.1

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65) Who discovered the period-luminosity relationship, and why was it so critical?

Answer: Henrietta Leavitt discovered the period-luminosity relationship for Cepheid variables in 1908, which later allowed astronomers to use them as a cosmic yardstick and recognize our Sun's true position in our Galaxy, as well as our Galaxy's true place in the universe.

Diff: 2 Section Ref: 13.2 66) Why were globular clusters so vital to Harlow Shapley's success?

Answer: Globular clusters lie in the halo, above and below much of the dust that had thrown off earlier attempts to map the Galaxy.

Diff: 2 Section Ref: 13.2 67) Compare the speed of spiral density waves with the orbital speeds of stars in the visible part of the Galactic disk.

Answer: Spiral density waves move slower than the orbital speeds at the same distance from the center of a galaxy.

Diff: 2 Section Ref: 13.5 68) How can Kepler's Third Law be used to estimate the mass of the galaxy?

Answer: We can find the total mass interior to a star's orbit if we know its orbital period and distance from the Galactic center. Using the numbers for the Sun, in the appropriate units, the mass can be shown to be around 1011 times the mass of the Sun. Diff: 2 Section Ref: 13.6 69) Of what is the Galactic halo presumed to be composed? What evidence supports this conclusion?

Answer: The globular clusters are most obvious, but it also has many loose stars of other old stars, escaped from their clusters, and a great deal of dark matter, whose true nature is still uncertain; brown dwarfs, black holes, and white dwarfs are all possible candidates.

Diff: 2 Section Ref: 13.6 70) How does content of elements heavier than helium vary between young and old stars? Why? Answer: Older stars are made of almost nothing but the hydrogen and helium made in the Big Bang, but younger stars are much richer (1-4%) in the heavier elements produced by later generations of supernovae.

Diff: 2 Section Ref: 13.3

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71) Arcturus shows a large proper motion, almost perpendicular to the Galactic plane. What Population does it belong to, and why?

Answer: Arcturus is the brightest halo star in the sky, revealed by its lack of metals and its comet-like motion cutting across the Galactic disk.

Diff: 3 Section Ref: 13.3 72) What do the orbits of halo and disk stars tell us about the formation of the Milky Way? Answer: Older halo stars move in comet-like orbits, well above the plane of the Galaxy in a spherical distribution. The disk stars formed later, after most of the remaining gas and dust had settled down into a disk, flattened by the rotation of the condensing Galaxy. Their orbits are much more like those of planets, fairly circular and in the Galactic plane.

Diff: 2 Section Ref: 13.4 73) Why is visible light a bad choice for studying the core of the Galaxy? What is better?

Answer: Dust in the Galactic plane blocks our view of most of our Galaxy, particularly toward Sagittarius. Radio was the first region where the Galactic center showed up well, but infrared and X-rays have also given good results recently.

Diff: 2 Section Ref: 13.7 74) What is the evidence to support the existence of a black hole at the center of the Milky Way? Answer: A large amount of activity is present. There is evidence of strong magnetic fields, Xray sources, extremely high stellar densities, an extremely energetic accretion disk, the strongest source of radio waves in the sky, and the stars and gas speed up as you get close to the core.

Diff: 2 Section Ref: 13.7 75) What features of the telescopic view of the Andromeda Galaxy, M-31, are also visible to the naked eye for our similar Galaxy?

Answer: In Andromeda, we see a tilted disk of stars, which in our home Galaxy is seen as the band of light stretching across the sky as the Milky Way. We lie inside this disk, so the band appears fairly narrow. Dust clouds and spiral arms are visible in the disk of M-31, and we also can make out portions of three arms with the naked eye, and nearby dust clouds visually create gaps in the band of distant star light.

Diff: 2 Section Ref: 13.1

14 ..

76) List at least one naked-eye observation that is consistent with the ancient idea that Earth is at the center of the Milky Way. List at least one naked-eye observation that is inconsistent with the notion that Earth is at the center of the Milky Way. Answer: The actual center of the galaxy is hidden by nearby dust clouds, although in fact the southern summer Milky Way is much brighter than the northern winter portions. We see portions of only three spiral arms visually, with the brightest one lying toward Sagittarius in the summer southern sky.

Diff: 2 Section Ref: 13.1 77) Why is a variable star so convenient for measuring distances to very remote objects?

Answer: Certain types of variable stars, such as Cepheids and RR Lyrae stars, pulsate with a precise period that is easily determined by observing variations in the star's apparent magnitude.

The period of a Cepheid is directly related to the absolute magnitude of the Cepheid and RR Lyrae stars have generally all the same absolute magnitude. When the apparent and absolute magnitudes of a star are known, its distance can be immediately calculated. Because Cepheids, in particular, are among the brightest stars known, they can be seen over large distances. Thus Cepheids are excellent for determining distances to remote objects.

Diff: 2 Section Ref: 13.2 78) Who was Henrietta Leavitt, and what did she do to help map the universe?

Answer: This Harvard astronomer found the period-luminosity relationship for the Cepheid variables from her work on the Large Magellanic Cloud. The discovery of these "cosmic yardsticks" allowed Shapley to map the home Galaxy, and other astronomers to use these stars in finding distances to many galaxies beyond us.

Diff: 3 Section Ref: 13.2 79) What are the observational pieces of evidence that confirm the existence of a three-part structure (bulge, disk, halo) to the Milky Way Galaxy?

Answer: The Galactic halo is observed by mapping globular clusters. The central bulge is seen in radio mapping. The disk is seen optically for nearby areas, and by radio mapping for far-flung regions hidden by dust and gas optically.

Diff: 2 Section Ref: 13.3 80) How old is the Galaxy? How do we know this?

Answer: The H-R diagrams of the globular clusters in the halo suggest they are 10-12 billion years old; their spherical distribution suggests they formed very early, before rotation had flattened the rest of the Galaxy out into a disk.

Diff: 2 Section Ref: 13.3

15 ..

81) Why do we believe there is dark matter?

Answer: When we use the Keplerian equation to determine the mass of the Galaxy we find a value of 100 billion Suns inside the Sun's orbital radius, or about 200 billion Suns all the way out to the end of the visible part of the spiral arms and halo stars. However, when we look the rotation curve we find objects distant from the center rotating much faster than expected. To account for this, there must be significantly more mass outside the visible portion of our Galaxy that we cannot see.

Diff: 3 Section Ref: 13.6 82) Why do astronomers believe that there is a large black hole, around 4 million times the mass of our Sun, in the Galactic center?

Answer: Observations of the Galactic center show a large amount of energy being produced.

Radio observations show a ring of gas with a high rotation speed around the center, showing a very large mass. The structure seen in higher resolution radio observations is peculiar. These observations are consistent with an accretion disk around a supermassive black hole.

Diff: 2 Section Ref: 13.7

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 14 Galaxies 1) There is very little interstellar gas or dust in most elliptical galaxies.

Answer: TRUE Diff: 1 Section Ref: 14.1 2) Galaxies are classified into types solely on the basis of their color.

Answer: FALSE Diff: 1 Section Ref: 14.1 3) The Milky Way's companion galaxies, the Magellanic Clouds, are irregular galaxies.

Answer: TRUE Diff: 1 Section Ref: 14.1 4) The Milky Way Galaxy's galaxy type is SBb. Answer: TRUE Diff: 1 Section Ref: 14.1 5) The smallest dwarf irregular galaxies are no richer in stars than the largest known globular clusters.

Answer: TRUE Diff: 2 Section Ref: 14.1 6) Most galaxies are members of some sort of cluster of galaxies.

Answer: TRUE Diff: 1 Section Ref: 14.2 7) Type I supernovae can be used to determine distances to galaxies much better than type II supernovae.

Answer: TRUE Diff: 2 Section Ref: 14.2 8) Collisions between galaxies have little effect on the individual stars.

Answer: TRUE Diff: 1 Section Ref: 14.3

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9) The expansion of the universe means that stars in our Milky Way Galaxy are getting increasingly farther apart.

Answer: FALSE Diff: 1 Section Ref: 14.4 10) Quasars can emit as much as thousands of times as much energy as normal galaxies.

Answer: TRUE Diff: 1 Section Ref: 14.5 11) Some lobes of radio galaxies are in fact moving faster than the speed of light.

Answer: FALSE Diff: 2 Section Ref: 14.6 12) Active galactic nuclei are usually powered by supermassive black holes.

Answer: TRUE Diff: 1 Section Ref: 14.6 13) Astronomers observe unobscured X-rays generated in active galactic nuclei.

Answer: FALSE Diff: 2 Section Ref: 14.6 14) It is now believed the majority of mass for most galaxies lies in their dark halos.

Answer: TRUE Diff: 1 Section Ref: 14.7 15) For nearby spirals, their rotation curves help measure both light and dark matter.

Answer: TRUE Diff: 2 Section Ref: 14.7 16) Gravity lensing lets us map the distribution of both visible and dark matter.

Answer: TRUE Diff: 2 Section Ref: 14.7

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17) A spherical galaxy, like M87, which looks like a monster globular cluster, is type A) S0.

B) ES. C) E0.

D) ES1.

E) 0V. Answer: C Diff: 1 Section Ref: 14.1 18) The flattest of the elliptical galaxies are class A) E0.

B) SBO. C) E7.

D) E9.

E) SBF. Answer: C Diff: 1 Section Ref: 14.1 19) In this diagram, the galaxy at the left side is a(n)

A) Seyfert.

B) Spiral.

C) Barred spiral.

D) Elliptical.

E) Irregular.

Answer: D Diff: 1 Section Ref: 14.1

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20) You observe a spiral galaxy with a large central bulge and tightly wrapped arms. It would be classified a A) Sc. B) Sb. C) Sa. D) SO. E) E7.

Answer: C Diff: 2 Section Ref: 14.1 21) An intermediately wound barred spiral galaxy would be A) BS2.

B) BSE.5.

C) SBb. D) S2B. E) SIrr. Answer: C Diff: 2 Section Ref: 14.1 22) Which type of galaxy has a small bulge and loose, widely spread, poorly defined spiral pattern?

A) SO B) S9 C) Sa D) Sc E) SBw Answer: A Diff: 2 Section Ref: 14.1 23) In Hubble's classification, which type of galaxy has no stellar disk and no gas or dust?

A) E0 B) S0 C) Sa D) SBc E) E9 Answer: A Diff: 2 Section Ref: 14.1

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24) The Large and Small Magellanic Clouds fall into class A) SBc. B) Pec. C) E6.

D) Irr I. E) E3.

Answer: D Diff: 2 Section Ref: 14.1 25) The Milky Way is often considered to be an intermediately wound, barred spiral, which would be type A) E4.

B) Sa. C) SBb. D) SBV. E) B2S. Answer: C Diff: 2 Section Ref: 14.1 26) The greatest variation in size, mass, and luminosity occurs in A) globular clusters.

B) elliptical galaxies.

C) spiral and barred spiral galaxies.

D) type I vs type II irregulars.

E) Seyfert galaxies.

Answer: B Diff: 2 Section Ref: 14.1 27) Which of the following is NOT one of the normal types of galaxies?

A) Normal spirals B) Barrel spirals C) Seyfert spirals D) Irregular type II E) Dwarf ellipticals Answer: C Diff: 2 Section Ref: 14.1

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28) Which statement about the Local Group is FALSE? A) It contains about 45 member galaxies.

B) Its notable spirals include the Milky Way, M31, and M33.

C) Most of its members are dwarf elliptical and irregular galaxies.

D) It contains the large radio galaxy Centaurus A. E) It is about three million light-years across.

Answer: D Diff: 2 Section Ref: 14.2 29) Most galaxies in the Local Group are A) dwarf spirals.

B) small irregulars similar to the Magellanic Clouds.

C) larger spirals than either the Milky Way or M-31 in Andromeda.

D) dwarf ellipticals, similar to the companions of M-31.

E) brown dwarfs, with even more dust than our own Galaxy.

Answer: D Diff: 2 Section Ref: 14.2 30) Why does the Cepheid "standard candle" have limited usefulness beyond 100 Mpc? A) Distant galaxies are seen in the past, when Cepheid variables behaved differently than they do today.

B) Distant galaxies are so young they do not contain Cepheids.

C) Cepheids are too faint to be seen beyond that distance, even with HST. D) The light variability of Cepheids diminishes with distance so they do not appear to vary there.

E) Older distant Cepheids are of population II, where the period-luminosity relation no longer works.

Answer: C Diff: 2 Section Ref: 14.2 31) Collisions between galaxies A) are much rarer than collisions between stars.

B) can turn elliptical galaxies into spirals.

C) cause large numbers of stars to collide and explode.

D) cause the gas and dust clouds to collide, leading to rapid star formation.

E) are the best explanation for gamma-ray burst events.

Answer: D Diff: 3 Section Ref: 14.3

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32) What is TRUE of spiral galaxies?

A) They are much less common at larger redshifts.

B) They are relatively rare in regions of high galaxy density.

C) They are only found in the center of rich galaxy clusters.

D) They have never been seen to have large redshifts.

E) They evolve from giant ellipticals.

Answer: B Diff: 2 Section Ref: 14.3 33) Which of the following paraphrases Hubble's Law? A) The faster the galaxy spins, the more massive and luminous it is.

B) The greater the distance to a galaxy, the greater its redshift.

C) The greater the distance to a galaxy, the fainter it is.

D) The more distant a galaxy is, the younger it appears.

E) The older the galaxy appears to us, the more luminous it is.

Answer: B Diff: 1 Section Ref: 14.4 34) What is TRUE of spiral galaxies?

A) They are much less common at larger redshifts.

B) They are relatively rare in regions of high galaxy density.

C) They are only found in the center of rich galaxy clusters.

D) They have never been seen to have large redshifts.

E) They evolve from giant ellipticals.

Answer: B Diff: 2 Section Ref: 14.4

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35) According to Hubble's Law, a galaxy with a velocity of 25,000 km/s will be

A) 100 million pcs away.

B) 400 million pcs away.

C) 700 million pcs away.

D) 1000 million pcs away.

E) less than 1 million pcs away.

Answer: B Diff: 2 Section Ref: 14.4 36) According to Hubble's Law, the greater a galaxy's redshift, the A) closer it is to us.

B) younger it is.

C) faster it's approaching us.

D) farther it is from us.

E) greater its mass.

Answer: D Diff: 2 Section Ref: 14.4 37) While examining the spectrum of a galaxy you find all the hydrogen lines are shifted to longer wavelengths. This galaxy is A) moving away from us.

B) moving towards us.

C) expanding explosively.

D) blue shifted.

E) not forming new stars.

Answer: A Diff: 2 Section Ref: 14.4

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38) Quasars usually have their distances measured by what technique?

A) Type II supernovae B) Cepheids C) Parallax D) Hubble's Law E) Tully-Fisher relation Answer: D Diff: 1 Section Ref: 14.5 39) That quasars were at cosmological distances yet appeared like ordinary faint stars meant A) they were the brightest stars ever observed.

B) they must be very large.

C) they must contain many O and B type stars.

D) they must be producing such large quantities of energy than even fusion could not explain their output.

E) they must be very small, but bright due to gravitational lensing.

Answer: D Diff: 2 Section Ref: 14.5 40) Quasar's spectral lines are A) emission lines with large red shifts.

B) a continuum from the synchrotron radiation.

C) fuzzy absorption lines from the merged light of the billions of stars.

D) too complex for any interpretation.

E) nonexistent, the gas so hot as to be totally ionized, so no lines are seen.

Answer: A Diff: 2 Section Ref: 14.5 41) In active galaxies, their central engines may be temporarily fed by A) a sudden surge of star formation.

B) a series of supernovae around the core.

C) the sudden collapse of the core into a supermassive black hole.

D) a close encounter with a neighbor galaxy.

E) the fusion of helium into carbon in their cores.

Answer: D Diff: 2 Section Ref: 14.5

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42) The lobes of a radio galaxy can be as much as A) dozens of light-years from the galaxy's nucleus.

B) hundreds of light-years from the galaxy's nucleus.

C) thousands of light-years from the galaxy's nucleus.

D) millions of light-years from the galaxy's nucleus.

E) billions of light-years from the galaxy's nucleus.

Answer: D Diff: 2 Section Ref: 14.5 43) In what sense are the quasars "quasi-stellar"?

A) Their energy production is hydrogen-helium fusion, like main sequence stars.

B) They are upscale versions of O stars, yet hundreds of times more massive.

C) Their luminosity comes from the millions of supergiants that compose them.

D) Their spectra is like that of ordinary stars.

E) In short time exposures, their images looked stellar.

Answer: E Diff: 2 Section Ref: 14.5 44) Most active galactic nuclei are powered by A) supermassive black holes.

B) a large number of supernovae.

C) mergers of compact objects.

D) black hole mergers.

E) extra-terrestrial civilizations.

Answer: A Diff: 1 Section Ref: 14.6 45) The energy radiated by a typical quasar requires that its black hole accrete about A) one solar mass a century.

B) one solar mass a decade.

C) one solar mass a year.

D) ten solar masses a year.

E) one solar mass a day.

Answer: D Diff: 2 Section Ref: 14.6

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46) Not only does the central engine of active galaxies and quasars require a black hole, but also ________ to provide the radiate energy.

A) globular clusters for food B) a very strong magnetic field from neutron stars C) a source of high-energy electrons for synchrotron radiation D) an accretion disk of infalling matter E) a high rate of rotation for the black hole Answer: D Diff: 2 Section Ref: 14.6 47) The magnetic fields carried by jets coming from active galactic nuclei are generated by A) the combined magnetic fields of the many stars near the galaxy's center.

B) the central black hole.

C) the movement of the interstellar matter of the galaxy.

D) the movement of the stars in the galaxy.

E) charged matter in the accretion disk of the central black hole.

Answer: E Diff: 2 Section Ref: 14.6 48) Although theory says a massive black hole with an accretion disk should be emitting X-rays, many black holes emit A) mostly in the infrared.

B) only in the visible.

C) mainly in the gamma.

D) virtually no radiation at all.

E) equally across the entire electromagnetic spectrum.

Answer: A Diff: 2 Section Ref: 14.6 49) A galaxy that was once a quasar is likely to A) have burned all its fuel by now and be dark.

B) now be a dwarf irregular.

C) have a black hole at its nucleus.

D) still be a quasar.

E) be less than 5 billion years old.

Answer: C Diff: 3 Section Ref: 14.6

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50) Rotation curves for spiral galaxies show A) they are slowing down.

B) rotation speed drops off further from the nucleus.

C) most have dark halos.

D) most of the mass lies in the nucleus.

E) no relation to mass.

Answer: C Diff: 2 Section Ref: 14.7 51) As we look at larger and larger scales in the universe, we find A) smaller and smaller masses.

B) almost exclusively visible matter.

C) a larger and larger percentage of the matter is visible.

D) a larger and larger percentage of the matter is dark.

E) an equal amount of visible and dark matter.

Answer: D Diff: 2 Section Ref: 14.7 52) Based on galactic rotation curves and cluster dynamics, we think dark matter A) is a minor component of the entire mass of the universe.

B) is best detected from the X-rays it produces in the intergalactic medium.

C) will have no effect on the fate of the universe.

D) comprises over 90% of the entire mass of the universe.

E) will doom the universe to collapse, overcoming the red shifts we now observe.

Answer: D Diff: 2 Section Ref: 14.7 53) According to their rotation curves, most spiral galaxies A) rotate as a solid body.

B) rotate counterclockwise.

C) have decreasing rotational speeds with increasing distance.

D) contain dark matter.

E) contain dark energy.

Answer: D Diff: 3 Section Ref: 14.7

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54) Collisions between galaxies is thought to A) have stopped about 5 billion years ago.

B) be commonplace.

C) have never occurred.

D) be extremely rare.

E) have only occurred between 10 and 15 billion years ago.

Answer: B Diff: 1 Section Ref: 14.8 55) Astronomers believe that a spiral galaxy may form A) from a collision between a small and large galaxy.

B) due to a quasar shutting down.

C) from the sudden contraction of an elliptical galaxy.

D) from the collision of two giant elliptical galaxies.

E) from the explosion of a dwarf irregular galaxy.

Answer: A Diff: 2 Section Ref: 14.8 56) The pregalactic blobs had masses similar to A) the earth.

B) the Sun. C) globular clusters.

D) the Large Magellanic Cloud.

E) the Milky Way. Answer: C Diff: 2 Section Ref: 14.8 57) In color photos, spirals typically have ________ arms with pink H II regions.

Answer: blue Diff: 1 Section Ref: 14.1 58) The Magellanic Clouds are good examples of the ________ type of galaxy.

Answer: irregular Diff: 1 Section Ref: 14.1 59) ________ galaxies are essentially featureless; their light reveals evidence for the presence of only old red Main Sequence and red giant stars.

Answer: Elliptical Diff: 1 Section Ref: 14.1

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60) Our galaxy, the Andromeda Galaxy, and about 40 smaller galaxies are members of ________.

Answer: the Local Group.

Diff: 1 Section Ref: 14.2 61) Most galaxies are in ________, which contain hundreds or thousands of galaxies.

Answer: galaxy clusters Diff: 2 Section Ref: 14.2 62) When two galaxies move very closely to each other, their ________ may dramatically rearrange their visible structures.

Answer: gravitational interaction Diff: 1 Section Ref: 14.3 63) Giant elliptical galaxies may be the result of ________ in the centers of rich clusters.

Answer: galaxy mergers (or cannibalism) Diff: 2 Section Ref: 14.3 64) Hubble's Law starts as a plot of recessional ________ versus distance to the galaxies.

Answer: velocity or speed Diff: 1 Section Ref: 14.4 65) Almost all active galactic nuclei seem to be involved in ________ with neighbors.

Answer: interactions Diff: 1 Section Ref: 14.5 66) Whether or NOT we see radio lobes from radio galaxies depends on their ________ relative to our line of sight.

Answer: orientation Diff: 2 Section Ref: 14.5 67) The ________ phenomenon is an extremely energetic event which apparently occurs in the nuclei of massive galaxies during an early stage of their evolution.

Answer: quasar Diff: 1 Section Ref: 14.5

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68) The energy source for active galactic nuclei is probably a(n) ________ around a supermassive black hole.

Answer: accretion disk Diff: 2 Section Ref: 14.6 69) From studies of the masses of individual galaxies and the masses of clusters of galaxies, it is now apparent that up to ________ of the universe is composed of dark matter.

Answer: 90% Diff: 2 Section Ref: 14.7 70) Giant elliptical galaxies may be the result of ________ in the centers of rich clusters.

Answer: galaxy mergers (or cannibalism) Diff: 2 Section Ref: 14.8 71) Distinguish an Sa from an Sc galaxy.

Answer: Sa spirals have more tightly wound spiral arms, and a wider nuclear bulge; Sc are flatter, dustier, and have looser arms.

Diff: 2 Section Ref: 14.1 72) Distinguish an E0 from an E7 galaxy.

Answer: Elliptical galaxies of type E0 show spherical symmetry, like a huge globular cluster; they spin very slowly. E7 spin faster, and are more flattened into a lens shape, but they don't show the disks found in spirals.

Diff: 2 Section Ref: 14.1 73) What type of galaxy are the two Magellanic Clouds? How do we know this visually?

Answer: Both are irregular galaxies, without the structure of either spirals or ellipticals, but with much visible gas and dust and new star formation typical of spiral arms.

Diff: 2 Section Ref: 14.1 74) To which portion of the Milky Way are the Magellanic Clouds most similar? Why? Answer: Like our spiral arms, our two irregular companions are rich in gas, dust, and newly formed stars.

Diff: 2 Section Ref: 14.1 75) The elliptical galaxies are most like what part of our Milky Way? Explain.

Answer: They are "all halo", with only Population II stars and poor in gas and dust. Also, their structure is somewhat spherical, like our halo, as well.

Diff: 2 Section Ref: 14.1 15 ..

76) What is a standard candle?

Answer: A standard candle is an astronomical object whose luminosity is known and is easily recognizable. These are used to help determine distances.

Diff: 1 Section Ref: 14.2 77) Why would galaxies colliding in a small cluster tend to stick together, while galaxies in a large cluster tend to pass through each other?

Answer: In a small cluster the lower mass means there is a smaller gravitational force pulling the galaxies together, which results in a lower collision speed. The greater mass in a large cluster results in a higher collision speed, high enough that the individual galaxies don't slow down enough to merge.

Diff: 3 Section Ref: 14.3 78) Why is Hubble's Law called the top of the distance ladder?

Answer: Hubble's Law builds on the other distance measurement techniques, which are rungs on the distance ladder. Hubble's Law works at the very largest distances, making it the top of the ladder.

Diff: 2 Section Ref: 14.4 79) Why do some radio galaxies appear to have lobes while some do not.

Answer: It's believed that all radio galaxies have lobes. If the lobe happens to be pointing at us, it appears minimized and we see mostly the core.

Diff: 2 Section Ref: 14.5 80) Why is it that the quasars we see represent a time when the universe was younger?

Answer: Quasars have very large redshifts, corresponding to large cosmological distances. Since the light they emitted travels at a finite velocity, it must have left the quasar many billions of years ago.

Diff: 2 Section Ref: 14.5 81) Quasar is short for what? Is this true of all of them?

Answer: Quasi-stellar radio source; no, many are radio quiet.

Diff: 2 Section Ref: 14.6 82) Relate black holes in the early galaxies to quasars.

Answer: Star-produced black holes in young galaxies could migrate to their centers. As the black holes merged and formed supermassive black holes, the accretion of matter around them created the quasar outpouring of energy.

Diff: 2 Section Ref: 14.6 16 ..

83) Why do we believe galaxy clusters are rich in dark matter?

Answer: Studies of the gravitational interaction of clusters reveal they have 10-100 times more mass than is visible.

Diff: 2 Section Ref: 14.7 84) Why would spiral galaxies be less common now than in the early universe?

Answer: As galaxies collide they change. As large spiral galaxies collide, they merge into ellipticals. Over time, more and more collisions between large spirals reduces their overall number.

Diff: 3 Section Ref: 14.8 85) How can some mergers activate spirals, and others destroy them?

Answer: A merger between equally massive galaxies may create a giant elliptical, without arms, while a small galaxy sideswiping a large spiral may draw out even more striking spiral structure, such as in M-51, the Whirlpool Galaxy.

Diff: 3 Section Ref: 14.8 86) In the Local Group, how might even the Milky Way become a victim?

Answer: In the binary system of us and Andromeda, eventually the two may collide, and the larger Andromeda Galaxy assimilate us, or both condense into a new, larger elliptical galaxy, looking much like Centaurus A. Diff: 3 Section Ref: 14.8 87) Briefly describe how Hubble classified the galaxies visually.

Answer: Ellipticals were divided into eight categories. He classified the most spherical as E0, and most flattened as E7. The spirals were divided into normal (smoothly unfolding arms) and barred (yellowish bar through the nucleus, then arms breaking off from it at right angles), and divided these into a, b, and c categories based on how tightly wound up the arms appeared, with Sa very tight, and Sc much looser.

Diff: 2 Section Ref: 14.1 88) What are the Magellanic Clouds? What happened in the LMC in 1987?

Answer: The Magellanic Clouds are our companion galaxies in the deep southern sky, around 200,000 ly distant. They are much smaller, irregular galaxies, rich in gas, dust, and new star formation. One of the massive blue giants exploded as supernova 1987A. Diff: 2 Section Ref: 14.1

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89) What lines of evidence show that the Milky Way Galaxy is indeed a spiral galaxy?

Answer: The plane of the disk is obscured by dust, but it can be mapped using 21 cm. radiation.

The central bulge can be observed at radio wavelengths, and it is clear that there is little significant structure above or below the disk, except the halo.

Diff: 2 Section Ref: 14.1 90) Discuss the population, size, and types of galaxies we find in our Local Group.

Answer: With 45 members, the Local Group is about 1 Mpc across. All types are found, with most being dwarf ellipticals and irregulars. The two main members are M31 in Andromeda, and our own Milky Way, both big spirals around which most of the smaller galaxies cluster.

Diff: 2 Section Ref: 14.2 91) Explain what a standard candle is and how it could be used to determine a galaxy's distance.

Answer: A standard candle is an object with a well known luminosity, such as a Type I supernova. If we see a standard candle in a distance galaxy, we can measure its apparent brightness and use the inverse square law to determine its distance.

Diff: 3 Section Ref: 14.2 92) Contrast the results of a collision between two spiral galaxies on their stars and their gas and dust clouds.

Answer: The stars are so spread out that collisions between them would be unlikely, but the shock wave set up when nebulae collide would create conditions for a starburst galaxy, which forms stars much faster than normal. Soon the gas and dust would be turned into stars, or heated so much as to be driven out into space.

Diff: 2 Section Ref: 14.3 93) How did Hubble use the cosmological redshift to determine distance?

Answer: The redshift is caused by the Doppler effect as a result of the galaxy's velocity. Hubble found that when known galactic distances (determined with a standard candle) were plotted with the recessional velocity, all the data fell on a straight line. The slope of this line is Hubble's constant. This allowed him to use a measured redshift (or calculated velocity) to read the distance off the plot, or to use the equation to calculate the distance.

Diff: 3 Section Ref: 14.4 94) Why is light variability a critical issue with the sizes of active nuclei?

Answer: The source of the light cannot be any larger than the time it takes light to cross it and change in brightness, so if the quasar varies in a matter of months, then its light emitting region cannot be more than a few light months wide.

Diff: 2 Section Ref: 14.5

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95) Explain as exactly as possible the way in which the central engine of active galaxies and quasars actually works. Why is the orientation so important?

Answer: Matter from an accretion disk falls into a supermassive black hole. As it does so, it accelerates and emits energy. About 20% of the energy from the mass falling in (from massenergy conversion, E=mc2) is radiated off. This energy may escape, or be absorbed by outer layers and re-radiated, or sent off as high-energy jets which give rise to radio lobes. What we see from Earth depends greatly on whether we see it from the side as radio lobes, or from the top as a blazar.

Diff: 3 Section Ref: 14.6 96) What are the common properties shared by most active galaxies and quasars? How do these properties lead to an understanding of the central engine?

Answer: All active galaxies and quasars emit massive quantities of radio and infrared wavelength energy in a non-blackbody spectrum from a very small (solar system-sized) source.

This can be understood if they are powered by matter falling into a supermassive black hole.

Diff: 3 Section Ref: 14.6 97) What is a galaxy's rotation curve? To which galaxies is it best applied, and what does it tell us about the distribution of dark matter?

Answer: The speed of rotation at various distances from the galaxies center is plotted for spiral galaxies whose rotation is more easily observed. The flat curve going out toward the edge shows us that there must be a dark halo, extending well beyond the visible one, and that dark matter may account for 90% of the total mass.

Diff: 3 Section Ref: 14.7 98) Describe how gravitational lensing works. What can it tell us about the galaxy that is doing the lensing? How is lensing valuable to the study of dark matter?

Answer: Gravitational lensing occurs when a nearby object (normally a galaxy) bends the light of a distant object (often a quasar), causing two or more images of the distant object to be seen.

The lensing galaxy can have its mass calculated based on the amount by which it bends light.

This lets us study dark matter by comparing the lensing galaxy's luminous mass with its gravitational mass.

Diff: 3 Section Ref: 14.7

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Astronomy: The Universe at a Glance (Chaisson/McMillan) Chapter 15 Cosmology and the Universe 1) An infinite universe is one of the assumptions of the cosmological principle.

Answer: FALSE Diff: 1 Section Ref: 15.1 2) The cosmological redshift is a direct measure of the expansion of the universe, thus independent of direction.

Answer: TRUE Diff: 1 Section Ref: 15.2 3) The Hubble constant divided into the number one gives a rough estimate for the age of the universe, or the "Hubble Time."

Answer: TRUE Diff: 1 Section Ref: 15.2 4) The cosmological redshift is actually not a velocity at all, but a measure of the expansion of space-time.

Answer: TRUE Diff: 2 Section Ref: 15.2 5) The Big Bang was an expansion of matter into empty space.

Answer: FALSE Diff: 2 Section Ref: 15.2 6) The low density universe is an open one, with expansion continuing forever.

Answer: TRUE Diff: 1 Section Ref: 15.2 7) The universe has been expanding at the same rate since its formation.

Answer: FALSE Diff: 1 Section Ref: 15.3 8) The fate or future of the universe depends only on the total number of galaxies and quasars.

Answer: FALSE Diff: 1 Section Ref: 15.3

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9) The cosmic microwave background is the total of all the radio emissions from all the galaxies and quasars in the universe.

Answer: FALSE Diff: 1 Section Ref: 15.4 10) Not taking dark energy into account, we seem to live now in a matter dominated universe, since the observed matter density exceeds the observed energy density.

Answer: TRUE Diff: 1 Section Ref: 15.4 11) Deuterium was made only in primordial nucleosynthesis, since stars destroy it.

Answer: TRUE Diff: 2 Section Ref: 15.5 12) Primordial nucleosynthesis refers to the Big Bang making all elements up to iron.

Answer: FALSE Diff: 2 Section Ref: 15.5 13) At decoupling, the electrons and protons were made from neutron decay.

Answer: FALSE Diff: 2 Section Ref: 15.5 14) Decoupling refers to interactions between matter and antimatter at the end of the Radiation Era. Answer: FALSE Diff: 3 Section Ref: 15.5 15) The flatness problem is the fact that the observed density of matter is unexpectedly different from the critical density predicted by the inflationary epoch.

Answer: FALSE Diff: 3 Section Ref: 15.6 16) The universe expanded by a factor of 1050 during inflation, when the strong force separated from the electromagnetic and weak nuclear forces.

Answer: TRUE Diff: 3 Section Ref: 15.6

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17) Dark matter had no effect on the distribution of matter in the early universe.

Answer: FALSE Diff: 2 Section Ref: 15.7 18) Observed mall fluctuations in the temperature of the cosmic microwave background are predicted by dark energy models.

Answer: FALSE Diff: 2 Section Ref: 15.7 19) What is the Great Wall?

A) It is a ridge on the Moon near the crater Birt.

B) It is the distance beyond which astronomers cannot view any more galaxies or even quasars.

C) It is a large sheet of galaxies.

D) It is the time before the universe started expanding, about which we can never know anything.

E) It is an enormous intergalactic cloud of dust and gas that hides more distant galaxies.

Answer: C Diff: 2 Section Ref: 15.1 20) Homogeneity and isotropy, taken as assumptions regarding the structure and evolution of the universe, are known as A) Obler's Paradox.

B) Hubble's Law. C) Wien's Law. D) the Cosmological Principle.

E) the Grand Unified Theory.

Answer: D Diff: 1 Section Ref: 15.1 21) The concept that the direction of observation does not matter overall is A) relativity.

B) homogeneity.

C) universality.

D) isotropy.

E) geometry.

Answer: D Diff: 1 Section Ref: 15.1

3 ..

22) The concept that on the grandest of scales, the universe is similar in appearance everywhere is A) special relativity.

B) general relativity.

C) homogeneity.

D) isotropy.

E) universality.

Answer: C Diff: 1 Section Ref: 15.1 23) The Hubble time is expressed as A) H × D. B) D/v.

C) 1/H. D) H × T. E) the critical density/H. Answer: C Diff: 1 Section Ref: 15.2 24) While a variety of factors can produce red shifts in the spectrum, the one associated with the expansion of the universe is called A) universal.

B) cosmological.

C) olberian.

D) relativistic.

E) the Zeeman Effect.

Answer: B Diff: 1 Section Ref: 15.2 25) The redshift of the galaxies is correctly interpreted as A) a Doppler shift due to the random motions of galaxies in space.

B) an aging of light as gravity weakens with time.

C) space itself is expanding with time, so the photons are stretched while they travel through space.

D) placing our Galaxy near the center of the Local Group.

E) the differences in temperatures and star formation in old and young galaxies.

Answer: C Diff: 2 Section Ref: 15.2

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26) What does Hubble's law imply about the history of the universe?

A) The universe must be infinitely old and huge.

B) The universe had a beginning and has expanded since, giving it a finite age.

C) The Milky Way lies exactly at the center of this expansion.

D) The red shifts will lengthen with time due to dark energy.

E) The red shifts will turn to blue shifts as universe contraction follows the expansion.

Answer: B Diff: 2 Section Ref: 15.2 27) The presently accepted value of the Hubble constant gives an age of A) 4.5 billion years.

B) 8-9 billion years.

C) 14 billion years.

D) 18 billion years.

E) 22 billion years.

Answer: C Diff: 2 Section Ref: 15.2 28) From the 1970s to the present, the accepted value of H has almost doubled, so A) the age of the universe is twice as old as we originally believed.

B) the age of the Universe is half what we believed.

C) the Copernican principle is not valid beyond our solar system.

D) the ages of the oldest globular clusters are invalid.

E) the critical density must also be halved.

Answer: B Diff: 3 Section Ref: 15.2 29) The center of the universe A) is the Milky Way. B) is the Sun. C) is Earth.

D) is where the Big Bang happened.

E) does not exist anywhere in space.

Answer: E Diff: 3 Section Ref: 15.2

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30) What was there just after the Big Bang?

A) Nothing B) The primeval fireball C) A singularity D) A black hole E) Everything was inside Earth.

Answer: B Diff: 3 Section Ref: 15.2 31) What is the Big Bang?

A) An enormous explosion that organized all matter in the universe B) The creation of matter and the universe C) The creation of the primeval fireball D) An explosion that spewed matter all over the universe E) The event that started the expansion of the universe Answer: E Diff: 3 Section Ref: 15.2 32) Astronomers know the universe is expanding because A) everything is moving away from us.

B) all stars are moving away from us.

C) most galaxies are moving away from us.

D) galaxies farther away are moving away from us faster.

E) there is a cosmic microwave background.

Answer: D Diff: 3 Section Ref: 15.2 33) In which of the following models will the universe stop expanding?

A) High Density Universe B) Low Density Universe C) Steady State Universe D) Critical Density Universe E) Euclidean Universe Answer: A Diff: 1 Section Ref: 15.2

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34) The critical evidence for cosmic acceleration in 1998 came from two teams of astronomers, both observing A) hypernovae.

B) gamma ray bursts.

C) type I supernovae.

D) type II supernovae.

E) ages of globular clusters.

Answer: C Diff: 2 Section Ref: 15.3 35) The expansion rate of the Universe is A) increasing.

B) decreasing.

C) constant.

D) different in different directions.

E) independent of time.

Answer: A Diff: 2 Section Ref: 15.3 36) The universal accelerating force could NOT be considered A) antigravity.

B) Einstein's cosmological constant.

C) dark energy.

D) vacuum pressure.

E) dark matter.

Answer: E Diff: 3 Section Ref: 15.3 37) The luminous matter in the universe accounts for what percent of the total mass of the universe?

A) About 5% B) About 23% C) About 27% D) About 73% E) 100% Answer: A Diff: 3 Section Ref: 15.3

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38) Recent work with type I supernovae at great distances suggests the universe may in fact be accelerating its expansion, a discovery attributed to a newly found A) repulsive charge on dark matter.

B) polarization and a universal spinning magnetic field.

C) dark energy.

D) magnetic field associated with antimatter.

E) mass determined for the neutrinos.

Answer: C Diff: 3 Section Ref: 15.3 39) What temperature has the Big Bang has cooled to by now?

A) About 3,000 K B) 5,800 K C) About 300 K D) Just over 2.7K E) 1.4 K Answer: D Diff: 2 Section Ref: 15.4 40) The discovery of the cosmic microwave background was important because A) it established a firm center of the Universe.

B) it was experimental verification of a prediction from the Big Bang theory.

C) it proved that astronomy at radio wavelengths was possible.

D) its detection was a major advance in microwave testing.

E) it showed the universe must be closed, with more than the critical density here.

Answer: B Diff: 2 Section Ref: 15.4 41) Currently, most of the mass of the matter of the universe is believed to consist of A) baryonic matter, made up of protons and neutrons.

B) tachyonic matter, travelling only faster than the speed of light.

C) dark matter not made of protons and neutrons.

D) dark energy.

E) tiny but very numerous black holes.

Answer: C Diff: 2 Section Ref: 15.4

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42) How does the energy of the cosmic microwave background compare to the energy radiated by all the stars and galaxies that ever existed?

A) They are very close to being equal.

B) 73% cosmic background, 27% starlight C) About ten times more from the Big Bang than from stars and galaxies D) The starlight now dominates the background, as your eyes show clearly.

E) We have no way of comparing matter and energy this way.

Answer: C Diff: 3 Section Ref: 15.4 43) The crossover point from radiation to matter domination occurred A) when the strong force separated from the other two forces.

B) with the emission of the cosmic background radiation.

C) about 50,000 years after the Big Bang, at a temperature of about 16,000 K. D) with the creation of neutrons and protons, at about 1013 K. E) with the creation of electrons and positrons at about 6 × 109 K. Answer: C Diff: 3 Section Ref: 15.4 44) At this time, the universe is A) radiation dominated.

B) quark dominated.

C) lepton dominated.

D) matter dominated.

E) dark energy dominated.

Answer: E Diff: 3 Section Ref: 15.4 45) Before about 4 billion years ago the universe was A) radiation dominated.

B) quark dominated.

C) lepton dominated.

D) matter dominated.

E) dark energy dominated.

Answer: D Diff: 3 Section Ref: 15.4

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46) Before about 50,000 years after the Big Bang the universe was A) radiation dominated.

B) quark dominated.

C) lepton dominated.

D) matter dominated.

E) dark energy dominated.

Answer: A Diff: 3 Section Ref: 15.4 47) Of the normal elements around us, the Big Bang produced A) none, only energy.

B) only hydrogen.

C) hydrogen and helium.

D) all elements up to iron.

E) all elements in much their present proportions.

Answer: C Diff: 2 Section Ref: 15.5 48) At the end of the first fifteen minutes, the mass ratio of H/He created was about A) 50/50.

B) 75/25.

C) 27/73.

D) 90/10.

E) 1/4.

Answer: B Diff: 2 Section Ref: 15.5 49) Which of these substances must be primordial?

A) Helium B) Lithium C) Deuterium D) Beryllium E) Tritium Answer: C Diff: 2 Section Ref: 15.5

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50) About how hot was the Big Bang when matter and energy "decoupled"?

A) 900 million K B) 15 million K C) 3,000 K D) 300 K E) 2.73 K Answer: C Diff: 2 Section Ref: 15.5 51) What key event happened during the decoupling epoch?

A) Pairs of neutrons and protons were created.

B) Electrons and positrons were created.

C) Expansion cooled the universe enough that protons could capture electrons in orbit.

D) Dark energy accelerated the cosmos on to infinity.

E) The universe underwent a brief period of very rapid expansion.

Answer: C Diff: 2 Section Ref: 15.5 52) The Big Bang formed A) only hydrogen.

B) only helium.

C) hydrogen and helium, but nothing else.

D) all elements up to iron.

E) all elements found in nature now.

Answer: C Diff: 2 Section Ref: 15.5 53) Before the decoupling A) the Universe was transparent to radiation.

B) the Universe was opaque to radiation.

C) protons and electrons combined to form atoms.

D) there was more helium than hydrogen.

E) deuterium produced electrons and positrons.

Answer: B Diff: 2 Section Ref: 15.5

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54) Most of the deuterium that formed right after the Big Bang A) is still around today.

B) broke down into electrons and neutrons.

C) turned into dark matter.

D) quickly burned into helium nuclei.

E) was found in the globular clusters.

Answer: D Diff: 2 Section Ref: 15.5 55) Which of these did NOT occur at decoupling?

A) The cosmic microwave radiation was released from matter.

B) Neutral atoms were formed.

C) Matter dominated radiation.

D) Electrons began to orbit protons.

E) The universe became transparent.

Answer: C Diff: 3 Section Ref: 15.5 56) Why didn't elements heavier than helium form in the first minutes of creation?

A) The first generation of stars used them up too quickly to observe them.

B) There was not enough matter in the universe at that time.

C) When He-4 was formed, the expansion cooled the cosmos below 100 million K. D) The electrons slowed down enough to be captured into orbits by protons.

E) Only Type I supernovae can produce iron and heavier elements.

Answer: C Diff: 3 Section Ref: 15.5 57) The best answer to both the flatness and horizon problems is A) the Steady State Theory.

B) the GUT theory.

C) the inflationary epoch.

D) dark energy.

E) decoupling.

Answer: C Diff: 2 Section Ref: 15.6

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58) The "flatness" problem arises because the curvature of space seems remarkably close to A) zero curvature, favoring a spherical cosmos.

B) exactly one.

C) .5, suggesting we are split between open and closed universes.

D) 2.73 K, in spite of the eddies and turbulence that led to galaxy formation.

E) infinity, suggesting an open universe is the only possible cosmology.

Answer: B Diff: 2 Section Ref: 15.6 59) Which of these seems the best present answer to the flatness problem?

A) The superforce rules creation.

B) Dark Energy speeds the universe on out to infinity.

C) Symmetry in creation of particles and antiparticles D) The inflationary epoch E) The GUT theory Answer: D Diff: 2 Section Ref: 15.6 60) The one theory of the early universe before the Recombination Epoch and after the Planck Epoch that was developed to resolve a conflict between observation and theory is A) the Grand Unified Theory.

B) the theory of inflation.

C) the theory of nucleosynthesis.

D) the theory of recombination.

E) the quantum quark theory.

Answer: B Diff: 3 Section Ref: 15.6 61) Observed temperature fluctuations in the Cosmic Microwave Background Radiation are A) millions of kelvins.

B) hundreds of kelvins.

C) a few kelvins.

D) tens of millionths of a kelvin.

E) immeasurably small.

Answer: D Diff: 2 Section Ref: 15.7

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62) Ripples in the Cosmic Microwave Background correspond to A) matter density fluctuations.

B) temperature fluctuations.

C) energy fluctuations.

D) fluctuations in both matter and radiation.

E) imperfections in measurement techniques or equipment.

Answer: D Diff: 2 Section Ref: 15.7 63) The first structures in the universe appear to have formed within A) the newly formed helium.

B) the normal matter.

C) the electromagnetic radiation.

D) the dark matter.

E) the dark energy.

Answer: D Diff: 2 Section Ref: 15.7 64) The huge, dark, almost spherical regions between the superclusters of galaxies are called ________.

Answer: voids Diff: 1 Section Ref: 15.1 65) The extended sheet of galaxies that spans 70 Mpc × 200 Mpc and includes about 24,000 galaxies is called the ________.

Answer: Great Wall Diff: 2 Section Ref: 15.1 66) ________ is the concept that all large samples of the universe are alike in appearance anywhere in the universe.

Answer: Homogeneity Diff: 1 Section Ref: 15.1 67) ________ is the concept that the universe looks the same in all directions.

Answer: Isotropy Diff: 1 Section Ref: 15.1

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68) The cosmological principle is the ultimate extension of the ________ principle; we are note at the center of the solar system, the galaxy, or the universe.

Answer: Copernican Diff: 2 Section Ref: 15.1 69) With the exception of a few nearby objects, every galaxy in the universe is rapidly moving away from ours; therefore, ________.

Answer: expanding Diff: 1 Section Ref: 15.2 70) Most astronomers agree to interpret ________ Law to mean that the present day universe is expanding.

Answer: Hubble's Diff: 1 Section Ref: 15.2 71) Is the Hubble Constant really constant?

Answer: No, with the influence of dark energy, it will gradually increase, speeding up the cosmic expansion to a final flat cosmos.

Diff: 2 Section Ref: 15.3 72) When dark matter first became popular, many astronomers thought that was greater than one from the extra gravity, favoring what type of Universe?

Answer: This would have favored a closed or spherical Universe that would eventually collapse back on itself.

Diff: 2 Section Ref: 15.3 73) How does dark energy affect the expansion of the Universe?

Answer: Dark energy is accelerating the expansion of the Universe, making it likely that it will expand forever.

Diff: 2 Section Ref: 15.3 74) Contrast dark matter and dark energy with respect to their roles in the future of the universe.

Answer: Dark matter exerts a gravitational influence that should slow down the universe's expansion, but dark energy seems to be accelerating the expansion instead.

Diff: 2 Section Ref: 15.3

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75) The ________ is the observational evidence that the whole universe was once extremely hot and dense, as called for in the Big Bang, but has now expanded and redshifted this energy to much longer wavelengths.

Answer: microwave background radiation Diff: 1 Section Ref: 15.4 76) Discounting the newly discovered role of dark energy, the universe we live in now is said to be ________ dominated.

Answer: matter Diff: 1 Section Ref: 15.4 77) The ________ background radiation in fact far exceeds all the energy radiated by all the stars and galaxies that formed since then.

Answer: microwave Diff: 1 Section Ref: 15.4 78) The universe was two minutes old when ________ started to form from deuterium fusion.

Answer: helium Diff: 2 Section Ref: 15.5 79) All of the ________ now observed must be primordial.

Answer: deuterium Diff: 3 Section Ref: 15.5 80) Computer simulations and the huge structures observed in the universe support the ________ model of the universe.

Answer: dark-matter-dominated Diff: 2 Section Ref: 15.7 81) State the cosmological principle.

Answer: The universe is both homogeneous and isotropic on the grand scale.

Diff: 1 Section Ref: 15.1 82) Does the universe have an edge or a center?

Answer: Not according to the cosmological principle, things look the same everywhere.

Diff: 2 Section Ref: 15.1

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83) Is the cosmological red shift really a velocity of a given galaxy?

Answer: No, it is a measure of how fast the entire universe is expanding in spacetime, with the galaxy just taken along for the ride.

Diff: 2 Section Ref: 15.2 84) Where did the Big Bang occur?

Answer: It involved the entire universe, which was very small at the time. It caused the universe to expand, so in effect the Big Bang occurred everywhere. It created both space and time, so there was not a "place" for it to occur before it did.

Diff: 2 Section Ref: 15.2 85) Why were elements heavier than helium not produced during the Big Bang?

Answer: Once helium was formed from deuterium, the temperature and pressure dropped too low for fusion to produce the heavier elements.

Diff: 2 Section Ref: 15.5 86) Regular atoms did not show up in the universe until when?

Answer: A few hundred thousand years after the Big Bang, when decoupling allowed the energy to escape, and cooled off the matter until electrons could orbit protons at temperatures of less than 3000 K. Diff: 2 Section Ref: 15.5 87) Why do the oldest stars we observe contain almost nothing but hydrogen and helium?

Answer: This first generation of stars must be made of the elements produced in primordial nucleosynthesis, which had time only to turn 25% of the hydrogen into helium.

Diff: 3 Section Ref: 15.5 88) Why was the separation of the superforce into three forces so important?

Answer: The pressure release created the inflationary epoch, when the universe expanded by 50 orders of magnitude, solving the flatness problem.

Diff: 3 Section Ref: 15.6 89) Why are the temperature fluctuations observed in the cosmic microwave background are important?

Answer: The angular scale of the fluctuations indicates that the density of the universe is very close to the critical density. The variations in temperature are consistent with dark matter models.

Diff: 2 Section Ref: 15.7

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90) The cosmological principle calls for the distribution of galaxies to be homogeneous. On the large scale, is this true?

Answer: No; the superclusters of galaxies seem to form sheets and walls, with a frothy appearance on the grandest of scales. There are also huge, apparently empty voids between the superclusters of galaxies; the explanation of this inconsistency is still unknown.

Diff: 3 Section Ref: 15.1 91) Galaxies in all directions are observed to be streaming away from us as if we were in the center of the universe. Contrast this impression with the Cosmological Principle and explain why a simple-minded interpretation of the Hubble expansion is incorrect.

Answer: If we are at the center of the universe that contradicts the cosmological principle which says that no point is in any way different from any other point. It is not that everything is moving away from us per sec, it is that everything is moving away from everything else. No matter where we might be, we would observe that everything moved away from us.

Diff: 2 Section Ref: 15.1 92) Why can one not use quasars to check the Hubble relation relating distances of objects to their velocity of recession?

Answer: The Hubble relation requires that the velocity of recession (or better, the redshift) and the distance to objects at cosmological distances be known. But astronomers do not know the distances to quasars except through using the Hubble relation. Quasars do not appear to be a standard candle, and most are variable in their luminosity over time as well.

Diff: 3 Section Ref: 15.2 93) At present the universe is expanding, but we are not certain if this expansion will continue forever, come to a stop, or if the universe will ultimately collapse back into itself. What observational tests are possible to test among these three possibilities?

Answer: The possibilities can be tested by measuring the density of the universe. If the density is too low the universe expands forever; if too high the universe stops and collapses. Also, measuring the amount by which the rate of past expansion differed from the current rate (by studying redshifts) can reveal the rate at which expansion is slowing and so what will happen.

Diff: 3 Section Ref: 15.3 94) Is there enough luminous matter to stop the universe's expansion? Is there enough dark matter? What else is there?

Answer: There seems to be only about 1-3% of the amount of luminous matter needed to stop the expansion of the universe. With dark matter included, the number comes up to perhaps 2030% of the amount needed, but still not enough. But the dark energy may in fact add in enough to give us a critical universe, with 73% of it in that new form.

Diff: 3 Section Ref: 15.3

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95) What is the cosmic microwave background, and why is it significant?

Answer: It is a 2.7 K universal blackbody background radiation, the same in all directions. It is the redshifted remnant of the intense radiation emitted in the Big Bang, now shifted all the way into the microwave region of the spectrum.

Diff: 2 Section Ref: 15.4 96) What factors would determine that we live in a matter-dominated universe?

Answer: The density of matter can be approximately determined through observation; it's about 10-27 kg/m3. The microwave background (which is more abundant than starlight) can be converted into an equivalent amount of matter using E = mc2. The result is a density of 10-31 kg/m3. Since this is much lower than the matter density, we conclude we live in a matter dominated universe.

Diff: 4 Section Ref: 15.4 97) Describe what occurred during the period of decoupling.

Answer: During decoupling, about 400,000 years after the Big Bang, the temperature was finally low enough (about 3,000 K) for neutral atoms to form. Before then, the universe was largely opaque to radiation since photons regularly scattered off of free electrons. When atoms formed, only photons of specific wavelengths would interact with matter, making the universe transparent to the cosmic background radiation.

Diff: 3 Section Ref: 15.5 98) Describe the separation of the superforce and the effect it had on the Universe.

Answer: The superforce separated into the electromagnetic, weak, and strong forces. At this time a tremendous pressure built up that caused the Universe to expand rapidly, causing parts of space that had been right next to each other to become widely separated. This is called the period of inflation.

Diff: 3 Section Ref: 15.6

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