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Discovery City Learning Centre

Universe Exploring the

by Craig Keaney

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© Craig Keaney ©Craig 2011 Keaney 2011


Forward Our sun is one of 100 billion stars in our galaxy. Our galaxy is one of billions of galaxies populating the universe. There is so much that we do not know about the universe we live in; How big is the universe? How many stars are in the universe? Is there other life? These questions my be answered one day but, for now, all we have are telescopes, deep space satellites and the most effective tool to help use explore more of the universe is our imagination. Always remember that somewhere, something incredible is waiting to be known.

ŠCraig Keaney 2011

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Contents Forward................................2 Phases of the Moon.............4 The Sun...............................6 Mercury................................8 Venus...................................9 Earth....................................10 Mars.....................................11 Jupiter..................................12 Saturn..................................13 Uranus.................................14 Neptune...............................15 Pluto....................................16 Stars....................................17 Black Holes.........................20 Star Lab..............................22 Glossary..............................24

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Phases of the Moon As the Moon orbits Earth, the face of the Moon appears to change throughout the lunar month; these are called phases of the Moon.

What causes the Moon to 'shine'? The light from the sun is reflected by the Moon, therefore, the side of the Moon that is visible to earth is illuminated, the other side-the side that is not visibleremains in darkness.

What causes different phases of the Moon? The phases of the Moon depend on its position in relation to the Sun and Earth. As the Moon orbits the Earth, we see the bright parts of the Moon’s surface at different angles (shapes).

How long does it take the Moon to orbit the Earth? The moon travels on an elliptic orbit (squished circle) which takes 27 days to orbit the Earth; to be exact it takes 27 days, 7 hours, 43 minutes and 11.6 seconds.

What is a lunar month? A lunar month is the time it takes for the Moon to complete all of the phases, longer than than the time it takes for the Moon to orbit the Earth.

How did the Moon come to be? Many Moons ago, an object about the size of Mars impacted Earth. The impact of this object caused debris to break away from Earth, which then cooled, eventually becoming the Moon. This impact happened 4.5 billion years ago. The Moon is called Luna.

ŠCraig Keaney 2011

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Phase 1 - New Moon - The side of the Moon that is facing the Earth is not lit up by the sun. At this time the Moon is not visible. Phase 2 - Waxing Crescent - A small part (less than 1/2) of the Moon is lit up at this point. The part that is lit up is slowly getting bigger. Phase 3 - First Quarter - One half of the Moon is lit up by the sun at this point. The part that is lit up is slowly getting bigger. Phase 4 - Waxing Gibbous - At this time half of the Moon is lit up. The part that is lit is slowly getting bigger. Waxing means to slowly get bigger.

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Phase 5 - Full Moon - The side of the Moon that is lit up by the sun is facing the Earth. The entire Moon is lit up at this point. Phase 6 - Waning Gibbous - The Moon is not quite lit up all the way by sunlight. The part of the Moon this is lit is slowly getting smaller. Waning means to slowly get smaller. Phase 7 - Last Quarter - Half of the Moon is lit up but the sun. The part that we can see lit up is slowly getting smaller. Phase 8 - Waning Crescent - A small part of the Moon is lit up at this point. It is getting smaller by the minute.

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ŠCraig Keaney 2011


The Sun The Sun is the largest object in our Solar System, in fact, it takes in 99.8% of the total mass of the Solar System. The Sun is one of over 100 billion stars in the galaxy. In the core of the Sun a massive nuclear reaction is occurring, a reaction that changes hydrogen in to helium, which causes intense magnetic fields, sun spots, prominences and solar flares.

Life of the Sun The Sun is about 4.5 billion years old. In about 10 billion years the sun will slowly cool and eject its layers until the core is exposed, when this happens it will become a white dwarf.

What is the Sun made of? The Sun is made up of mostly hydrogen and 10% helium. The nuclear reaction in the Sun changes hydrogen in to helium.

What is a solar eclipse? A solar eclipse is when the Moon moves between the Earth and the Sun. When this happens, part of the Sun’s light is blocked. The sky slowly gets dark as the moon moves in front of the Sun. When the moon and Sun are in a perfect line, it is called a total eclipse. These are very rare. Most people only see one in their lifetime.

ŠCraig Keaney 2011

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What is a sunspot? A sunspot is a small, relatively cool region of the Suns bright service (photosphere) that appears as a dark spot on the visible service of the Sun.

What is a prominence? A spurt of hot solar material extending outwards from the edge of the Sun.

What is a Solar Flare? A flare is a highly energetic form of solar activity, that can last from seconds to hours. The solar flare is caused by a sudden release of magnetic energy from the Suns upper atmosphere. (corona)

Other facts • The official classification of the Sun is: Yellow G2 Dwarf • If the Sun was any brighter, it would have burnt through all of its fuel and life on Earth would not exist. • In the same way that the planets orbit around the Sun, the Sun orbits around the centre of the Milky Way galaxy, taking 225,000,000 years to complete a full orbit. • Named after the Roman god, Sol.

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©Craig Keaney 2011


Mercury Mercury, name after the Greek god Hermes. In the times of Ancient Greece, people believed that Mercury was in fact two planets, which they named, Hermes and Apollo.They believed Mercury was two planets due to when the planet could be seen, early morning or evening twilight. Mercury is the closest planet to the Sun, but bizarrely, not the hottest. Temperatures on Mercury differ greatly, when Mercury is in shadow (facing away from the Sun) temperatures are as low as -300 degrees Fahrenheit and when facing the Sun the temperature can reach 800 degrees Fahrenheit. This extreme temperature is due to the fact that Mercury has no atmosphere, so when Mercury faces the Sun, it heats up the planet and when in shadow the heat quickly dissipates lowering the temperature drastically. Mercury is one of four terrestrial planets, a planet that is made up mostly of rock and metals. One day on Mercury is equal to 58.5 Earth days. Two satellites have managed to reach Mercury, Mariner 10 and MESSENGER, the satellites have only managed to map approximately 45% of the planet surface. Images show that the surface is scarred with craters, this is due to impacts from astroids over ions. All celestial bodies within the Solar System are subject to these bombardments. However, many of the planets have the ability to heal themselves through natural geological processes

Diameter: 5000km Distance from Sun: 58million km Average temperature: -300F – 800F Moons: 0

ŠCraig Keaney 2011

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Venus Venus, named after the Roman goddess of beauty, Venus was given this name, probably due to the brightness of the planet in the night sky ancient in times. Venus is another of the four terrestrial planets, again it made mostly of rocks and metals. Venus is the hottest planet out of the 8 planets, this is due the atmosphere. Venus has a very dense atmosphere, which acts like a blanket and stops the heat escaping from the planet, this is very much like the Greenhouse effect. Venus is thought to have had oceans but, as the Venus is so hot the oceans have boiled away. Venus, is sometimes called Earth's sister planet because they have some similarities. Firstly, Venus once had oceans like Earth, Venus is only slightly smaller than earth, both have very few craters, which indicates a young surface and finally, the composition and density of Venus is similar to Earth. Though Venus is referred to as Earth's sister planet, life could not be sustained due to the temperature and the clouds, unlike Earth are poisonous.

Diameter: 12 000km Distance from Sun: 108million km Average temperature: 850F Moons: 1

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ŠCraig Keaney 2011


Earth Earth, home sweet home, names after Gaea, who was the mother of the mountains, valleys, streams and all other land formations in the Ancient Greek times. Earth is the biggest of all four terrestrial planets. Earth is a somewhat oasis with vast beautiful oceans, mountains and deserts; temperatures, that are exotic and sub-zero. A beautiful planet in a desolate universe? 71 % of the Earth's surface is covered with water. Earth is the only planet on which water can exist in liquid form on the surface. Water is essential for life as we know it. The Earth's vast oceans keep temperatures stable - important for life on our planet. Water is also responsible for most of the erosion and weathering of the Earth's continents, a process unique in our solar system. Even though Earth is over 4 billion years old, the oldest known rocks are less than 4 billions years old; rocks older than 3 billion years are old are rare. The oldest known fossils of living organisms are less than 3.9 billion years old. Some scientist believe that there are 3 Moons, this is a misconception, in fact there is only one. 3753 Cruithne thought to be a Moon is an astroid that orbits the Sun and the other thought to be Moon, AA29 is again another astroid that follows as horseshoe orbit around the Sun, AA29 can be seen on Earth approximately every 95 years.

Diameter: 13 000km Distance from Sun: 150million km Average temperature: 45F Moons: 0 (Luna)

ŠCraig Keaney 2011

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Mars Mars, the red planet, named after the Roman god of war and agriculture. Mars is the last of the terrestrial planets. Mars is referred to as the 'red planet' as the sand/dust is mostly made up of iron, the metal and is red because it has rusted; so, really should be called the 'rusty planet.' Mars excites scientists because its mild temperament is more like the Earth's than any of the other planets. Evidence suggests that Mars once had rivers, streams, lakes, and even an ocean. As Mars' atmosphere slowly depleted into outer space, the surface water began to permanently evaporate. Today the only water on Mars is either frozen in the polar caps or underground. Twenty five years ago something funny happened around Mars. NASA's Viking 1 spacecraft was circling the planet, snapping photos of possible landing sites for its sister ship Viking 2, when it spotted the shadowy likeness of a human face. An enormous head nearly two miles from end to end seemed to be staring back at the cameras from a region of the Red Planet called Cydonia. Unfortunately, this Pharaoh-like head was caused by a shadow creating an optical illusion were we could see a face. Mars has two Moons, Deimos and Phobos. The Moons have an odd shape, this is because these moons are smaller than most town and their gravity is not strong enough to pull them in to a spherical shape. Phobos, is referred to as the 'Doomed moon' as for those humans who are alive in 50 million years will not get to see Phobos as approximately every 100 years the Moon moves 2 meters closer to the surface of Mars so, Phobos will either crash to the surface or be ripped apart. Diameter: 7000km Distance from Sun: 228million km Average temperature: between -190F and 98F Moons: 2 (Deimos and Phobos)

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Jupiter Jupiter, known as Zeus in Greek mythology, over threw his father Saturn to become king of the gods. He then split the universe with his brothers Neptune and Pluto. Jupiter is one of two gas giants, Jupiter is considered a gas giant because it does not have a solid surface. Under its atmosphere is a large liquid ocean of hydrogen and water. What lies in between that ocean and the atmosphere? Actually, there is no in between. The atmosphere slowly gets thicker and thicker until it becomes part of the ocean. In other words, Jupiter’s ocean has no surface on which you could float a boat. The sky becomes the ocean. Jupiter is the largest planet in the Solar System, it is so big it can fit 1000 Earth sized planets within it. One of the most interesting features of Jupiter is the 'the eye of Jupiter'. it is believed that this eye is in fact a massive storm that has been raging for over 300 years, there are other spots like this on Jupiter, though smaller. Jupiter has 3, very faint rings. The rings can only been see when Jupiter passes the Sun which makes them visible to us on Earth. The rings have been named Gossamer, Main and Halo. Jupiter has over 50 Moons. The four largest Moons, discovered by Galileo in 1610 are the more well-known; Io, Europa, Ganymede and Callisto.

Diameter: 140 000km Distance from Sun: 778million km Average temperature: -244F Moons: over 50 (most know - Io, Europa, Ganymede and Callisto)

ŠCraig Keaney 2011

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Saturn Saturn was the Roman god of agriculture. He was called Cronus by the Greeks.In many ways, Saturn is similar to Jupiter, but it is much smaller. It is the second largest planet in our Solar System and it is a gas giant like Jupiter. Under the clouds of methane, hydrogen and helium, the sky gradually turns into liquid until it becomes a giant ocean of liquid chemicals.Saturn is the least dense planet in our Solar System. It is made up of mostly hydrogen and helium, which are the two lightest elements in the universe and thus make Saturn the lightest planet that we know of. This is why you wouldn't weigh as much on Saturn as you think you would because of its size. And because Saturn is so light, it does not have as much gravity. Interestingly, it is believed Saturn would actually be able to float in water because the hydrogen and helium that make up the planet are so lightweight. Because Saturn is such a lightweight planet and it spins so fast, Saturn is not perfectly round like most of the other planets. Like Jupiter, Saturn is wider in the middle and more narrow near its top and bottom. Saturn is well-know for its rings, the rings the are over 169,800 miles wide, though the rings are massive they are no more than 10 metres thick. The rings are made up of particles of ice, dust and rocks. The rings are held in place around Saturn by the moons that also orbit this large planet. The gravity of these Moons also cause the gaps that are seen in between the rings. Saturn has 53 official Moons, the most well-known Moon orbiting Saturn is Titan, which is the second largest Moon in the Solar System, the first being Ganymede, orbiting Jupiter; Titan is bigger than the planet Mercury.

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Diameter: 120 000km Distance from Sun: 1430million km Average temperature: -300F Moons: 53 official (most know - Titan) ŠCraig Keaney 2011


Uranus In astronomy mythology, Uranus was the lord of the skies and husband of Earth. He was also the king of the gods until he was overthrown by his son Saturn. Like Jupiter and Saturn, Uranus is a gas giant. But Uranus is a little different. Unlike all the other planets and most of the moons in our Solar System, Uranus spins on its side. It is believed that long ago a very large object smashed into this planet. The crash was so powerful that it completely changed the direction of Uranus' planetary rotation. However, a more recent theory is that the extreme tilt of Uranus’ axis may have been caused by a large moon that was slowly pulled away from the planet by another large planet long ago when our Solar System was still new. It is thought that the gravitational pull of this moon moving away from Uranus may have caused it to tilt on its side.Like Saturn, the thick atmosphere of Uranus is made up of methane, hydrogen and helium. But Uranus is an extremely cold planet. It has been called the "ice giant." It is believed that Uranus is made up of rock and ice and has a large rocky core. Because of the tremendous planetary pressure of Uranus, there could possibly be trillions of large diamonds in or on the surface of this planet. Scientists also believe that on the surface of Uranus there may be a huge ocean. And, interestingly, it is thought that the temperature of this ocean may be extremely hot, maybe even as hot as 5000 degrees Fahrenheit (2760 Celsius). Uranus is almost identical to the planet Neptune. Uranus has rings though the rings do not stretch out as far as the rings of Saturn. The rings Uranus are made up of black dust particles. Uranus has 27 Moons, five of the moons are large and the rest are smaller, the largest of Uranus' Moons is Titania.

Diameter: 51 000km Distance from Sun: 2870million km Average temperature: -300F Moons: 27 (most know - Titania) ŠCraig Keaney 2011

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Neptune Neptune named after the god of water which, later extended to the seas and oceans. For many, centuries people did not know that this planet even existed. It was discovered by Johann Galle and Heinrich D'Arrest in 1846. Neptune is the smallest of the four gas giants in our Solar System. Much like Saturn and Uranus, Neptune's atmosphere contains hydrogen, helium and methane. Not much was known about Neptune until it was visited by the spacecraft Voyager 2 on August 25, 1989. Voyager 2 took many pictures of the planet, and much of what we know today about Neptune came from this single visit. These pictures show a brilliant blue planet with a few thin white clouds laced around its surface. In Neptune's atmosphere, there is a large white cloud that moves around rather quickly. The "scooting" of this cloud around the atmosphere has led it to be named "Scooter." When Voyager 2 visited Neptune, its pictures showed a giant storm much like the storm on Jupiter. This storm is called the "Great Dark Spot" because it appears as a dark oval shape on the surface of the planet. We do not know how long this storm has been active or if it is still present. More recently, the Hubble Space Telescope sent pictures back to Earth and there was no sign of the Great Dark Spot. Neptune has six rings, the rings are though to be a new feature of the planet. The rings are more irregular than the other planets rings, Neptune's rings vary in size and thickness. Neptune has 13 known moons, as Neptune is a newly discovered planet and that it is so far away, we cannot see if there is any other moons orbiting the planet. The first moon discovered is called Triton which, was discovered by an Englishman, just 17 days after the planet was discovered.

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Diameter: 48 000km Distance from Sun: 4500million km Average temperature: -370F Moons: 13 (most know - Triton) ŠCraig Keaney 2011


Pluto Pluto was thought to be the god to whom all men must eventually go. Romans believed him to be the god of the underworld. In Greek mythology, he is known as Hades. Pluto was the only planet to be named by a child. After the planet was discovered in 1930, an 11-year-old girl who lived in Oxford, England, by the name of Venetia Burney, suggested that this new planet needed to be named after the Roman god of the underworld. Venetia's grandfather sent this suggestion to the Lowell Observatory and the name was accepted. Pluto is smaller than 7 of the moons in the Solar System. It is about two-thirds smaller than Earth's moon. Because it is so small, many scientists don't consider it a planet at all. In 1999, a group of scientists attempted to reclassify Pluto as a comet. On August 24, 2006, Pluto's status was officially changed from planet to dwarf planet. For decades, children have been taught in school that there are nine planets in our Solar System. However, with this change, there are now only eight planets. Also because of this change, there is a new category of small planets known as plutoids. Pluto has 3 Moons, the largest of the Moons is Charon which, is slightly smaller the Pluto, due to this Pluto and Charon are called the double system. Pluto's other Moons are called Hydra and Nix

Diameter: 2400km Distance from Sun: 5900million km Average temperature: -390F Moons: 3 (Charon, Hydra and Nix)

ŠCraig Keaney 2011

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Galaxaies What is a Galaxy? A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas, dust, and dark matter.

What types of Galaxy are there? Historically, galaxies have been categorized according to their apparent shape. A common form is the elliptical galaxy, which has an ellipse-shaped light profile. Spiral galaxies are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as irregular galaxies, and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a starburst galaxy. Small galaxies that lack a coherent structure could also be referred to as irregular galaxies

The Milky Way The Milky Way is the galaxy that contains our Solar System.Its name derives from how it appears in the night sky; as a dim unresolved “milky” glowing band arching across the sky.

Other Facts The Milkyway is a barred spiral galaxy there are 200-400 billion stars in the Milky Way The oldest star in the Milky Way is about 13.2 billion years old

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Stars What is a star? The scientific definition of a star is a large, near-spherical object that emits electromagnetic radiation through self-sustaining nuclear reactions in its interior. But, from Earth we see them as beautiful spots of light in the night sky.

Where do stars come from? Stars are formed when a Protostar, a fragment of a molecular cloud, emits infra-red radiation. As the contraction continues and the gas falls a distance of light years it becomes super heated, the gas can reach temperatures of 100million degrees celsius. When the gas is super heated it squashes together and starts a nuclear reaction at the core, and so it becomes a star.

What happens when a star dies? When a star is born it will be powered by its nuclear core for millions or even billions of years. But, when a stars does reach the end of its life, it burns its fuel more rapidly and becomes hotter and what happens next depends on the type of star. Stars do not just die or cease to be, they can be rather dramatic and beautiful;

Red Giants and White Dwarfs After an existing star has exhausted its hydrogen fuel supply, the star goes through some more stages of nuclear reactions that involve other substances. The star will then swell to hundreds of times of their original size and go through mass cooling, from about 6000 Celsius to 3000 Celsius. After these various processes the star will appear red or orange, this is a Red Giant. At the end of its life as a Red Giant, the star will shed much of it material to become a White Dwarf

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Supergiant and Supernova If the star is eleven times the mass of our Sun, it will swell and cool and increase in brightness to become a supergiant. When the hydrogen fuel supply is used up, its end is ever more dramatic. The star rapidly goes through more stages of nuclear reactions, and suddenly the star will explode, this is called a supernovae. This explosion stage lasts for a matter of minutes, then the star is ripped apart.

Neutron Stars and Pulsars After a supernovae, a small part of the original star may survive at the centre, this small fragment will have no fuel left to burn but will carry on shrinking under its own gravity, this is a neutron star- a tiny object 20 km in diameter but has a mass greater than the Sun. It may also become a pulsar which is short for pulsating radio source. As the star shrinks, it spins more rapidly and pluses, rather like a lighthouse.

What is the north star? The north star, Polaris, is the brightest star in the Ursa Minor Constellation and is close to the celestial north pole. Polaris is about 434 light-years way from Earth.

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Black holes What is a Black Hole? A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying. Because no light can get out, people can't see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.

How Big Are Black Holes? Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain. The largest black holes are called “supermassive.” These black holes have the mass of more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths.

How Do Black Holes Form? Scientists think the smallest black holes formed when the universe began. Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.

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Cosmic Learning with...

Discovery City Learning Centre

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ŠCraig Keaney 2011


Star lab The Star Lab takes learning beyond the classroom. It is hard to teach and learn about space and beyond, especially when we teach during the day. The Star Lab lets us observe a vast amount of the known universe from the closest object, Luna, the Moon to distant galaxies such as, Baby Boom.

How does the Star Lab work? The Star Lab come in two parts, an inflatable dome and a high definition projector. The Star Lab is very portable and pack up in to smaller cases. The Star Lab is very much like a Planetarium.

What can the Star Lab be used for? Phases of the Moon: With the Star Lab you can zoom in to take a closer look at Luna, the Moon. As you travel through the months in a matter of minutes you can see the phases of the Moon, from the New Moon all the way to a Full Moon. You can also zoom in further to look at the craters on the face on the Moon. The Sun: No human has ever travelled to the Sun, but now the whole class can visit. In a matter of seconds the class will arrive and begin to orbit the Sun. With the Star Lab it is easy to see the size of the Sun in relation to other planets. The class will get to see the centre of the Milky Way. The Planets: Worlds that can only been seen through telescopes, as colourful dots in the sky. With the Star Lab this is not the case. We can look at the planets in the sky but also travel to them and enter their orbit. We can look at the surface, their atmosphere and their satellites (Moons) and unearth their mysteries. Constellations: Much more than pretty picture in the sky, constellations have been intermingled in stories and each constellation has it part in mythology. The Star Lab will display the constellations in a ‘dot to do’ style, with a colourful picture overlay and with a text label. As times moves forward in the Star Lab, it is easy to see what constellation can be seen at a particular time of the year. Galaxies: From Earth, we sometimes make the assumption that the shining dots in the sky are star, in fact, they can be a number of celestial objects, stars, planets, comets or satellites. Sometimes they may be a distant galaxy. The Star Lab will take you light years and show you distant galaxies such as the Andromada galaxy, the Baby Bang galaxy or Centaurus A galaxy. ©Craig Keaney 2011

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What subjects can the Star Lab be used in? Science: explore the beyond, travel to distant planets, explore distant galaxies or stay close to home watch as Luna changes over the month. Religious Education: How did the three wise men find Jesus? Did they follow a star, or was it a planet brightly shining or even an alignment of all the planets? Use the Star Lab to explore the possibilities. History: Most, if not all of the constellations are derived from myths and Legends; Hero’s and Heroines. What was the story of Orion the hunter? Who was Hercules and Pegasus. The legends come from all area of the world, the most known constellations come from Ancient Egypt and Ancient Greece. Creative Writing: The Star Lab could have crashed landed on Venus, who lives there? Is it a deserted world? Use your imagination to write a story. Drama/role play: You have travelled through time and space but the Star Lab has malfunctioned, the light engines have broke, your orbit deteriorating and you crash land on a distant moon. You gather the courage and open the air lock...

Contact Details If you are interested in hiring the Star Lab, wish to attend a Space workshop or would like further information please use the contact details below. Alternatively, watch iwisch for information on forthcoming workshops.

Tel: 0151 641 8480 Fax: 0151 641 8483 email: craigkeaney@discoveryclc.co.uk

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Glossary Asteroid: A small rocky body found mainly between Mars and Jupiter. Astronomy:The study of celestial bodies and the regions of space between them. Atom: The smallest building block in a molecule. Big Bang: The event that marks the beginning of cosmic expansion. Black Hole: A highly condensed remains of a star, whose gravity is so strong that light can not even escape. Celestial Sphere: An imaginary sphere surrounding the Earth of which the Stars appear to be fixed. Comet: A small icy body left over from the formation of the Solar System that partially evaporates if it approaches the Sun, generating long tails. Constellation: Any of the 88 designated regions that jointly cover the whole celestial sphere. Core (of a star): The central, very hot region of a star, where nuclear reactions can happen. Corona: The upper part of the Sun’s atmosphere. It is very hot, very tenuous and very extensive. Dark Matter: A currently mysterious form of matter that neither absorbs nor emits any detectable radiation, but can be detected and studied through its influence on diectly observable (‘bright’) matter. Flare: A highly energetic form of solar activity, typically lasting a few hours, caused by a sudden release of magnetic energy in the Corona. Galaxy: A vast assembly of dark matter and luminous matter, typically tens of thousands of light-years in diameter and containing billions of stars, held together by the mutual gravitational attractions of its constituents.

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Glossary Giant Planet: A planet considerably larger than the Earth, composed largely of hydrogen and helium. Light-year: The distance that electromagnetic radiation travels through space in one year. Lunar Month: The average time between two successive new Moons. Moon Phases: A particular shape of the illuminated surface of the Moon, as seen by the observer. Meteor: A small rocky object originating outside the Earth that enters the Earth’s atmosphere and can be seen travelling through it. Meteorite: Any surviving meteor that enters Earth’s atmosphere, which partially burns up before landing. Milky Way: The large, barred spiral galaxy in which the Sun is located. Nebula: A loose term, literally meaning ‘cloud’, applied to any interstellar object that appears extended or ‘fuzzy’. Neutron Star: A stellar remnant of mass rather more than the Sun, with a diameter of only about 20km. Formed from the collapse of a Supergiant star after a supernova. Photosphere: The bright visible surface of the Sun or any similar star. Planet: One of the eight major bodies orbiting the Sun, or a similar body orbiting another star. Planisphere: A device for displaying which stars are above the horizon at any particular time on any particular date. Prominence: A spurt of hot solar material seen extending outwards from the edge of the Sun.

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Glossary Pulsar: The rapidly spinning, dense central part of a star that remains after a supernova; detected by its regular radio pulses. Red Giant: A large, cool star that is going through subsidiary stages of nuclear reactions, having exhausted the hydrogen fuel supply in its core. Satellite: An object in orbit around a larger one, e.g. a moon orbiting a planet. Solar Eclipse: The partial or complete blocking of the Sun’s photosphere by the Moon. Solar System: Our Sun and all the bodies associated with it; planets, their satellites, comets and asteroids. Star: A large, near-spherical object that emits electromagnetic radiation through self-sustaining nuclear reaction in its interior. Sun: The star at the centre of the Solar System. Sunspot: A small, relatively cool region of the Sun’s photosphere that appears as a dark spot on the Sun. Supergiant: A star, several times more massive than the Sun, after it has exhausted the hydrogen nuclear fuel supply in its core. Supernova: A dramatic stellar explosion, produced when a star several times the mass of the Sun has exhausted its nuclear fuel. Terrestrial Planet: A planet similar in size to the Earth, composed of rocky material. White Dwarf: A small hot star, left behind when a red giant throws off its outer layers.

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Exploring The Universe  

Looking at the solar system and beyond

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