STAR VIDEO

1. WHAT IS A STAR??1. A star is a huge sphere of very hot glowing gas. Stars are classified according to their temperature and brightness. Hot stars are blue or white. Cool stars are red or orange. A young star is called a dwarf star. They can be red yellow or white. Our Sun is a yellow dwarf. Older stars are called Supergiants. They are red or blue.

2. STAR VIDEO • http://www.learn360.com/ShowVideo.aspx?ID=139620

3. 2. Star Birth:A. Like people, stars are born. They grow old, and they die. They are born in huge, cold clouds of gas and dust, known as 'nebulas'. The most famous of these is the Orion nebula..

4. B. These gas and dust clouds start to shrink under their own gravity. As the cloud gets smaller, it breaks into clumps. Each clump eventually becomes so hot and dense (thick) that nuclear reactions begin. When the temperature reaches 10 million degrees Celsius, the “clump” becomes a new star.

5. C. Most young stars lie at the center of a flat disc of gas and dust. Most of this material is eventually blown away by the star’s radiation. Before this happens, planets may form around the central star.

6. 3. Dwarfs and SupergiantsA. The Sun is a star. Like most stars, the Sun is a ball of very hot gas that gives off huge amounts of light, heat and other radiation. It is like millions of hydrogen bombs exploding every second.B. There are many different types of stars. Red stars are the coolest, with surface temperatures of around 2,500 degrees Celsius. Blue-white stars are the hottest, reaching a sizzling 40,000 degrees. Yellow stars, like the Sun, are in-between, with surface temperatures of about 5,500 degrees.

7. C. Stars come in many sizes. The Sun is medium-sized. It burns its hydrogen fuel fairly slowly, so it can keep shining for 10 billion years.D. Some stars are much bigger and hotter than the Sun. The red supergiant Antares is 800 times wider than the Sun. If it was at the center of our Solar System, it would swallow up all of the inner planets, including Earth. Like gas guzzler cars, these supergiants use all of their hydrogen and helium fuel very quickly. After perhaps 500 million years, they die in a supernova explosion.

8. E. The coolest, slowest burning stars are red dwarfs. These can survive for more than 10 trillion years. F. Even cooler and smaller are brown dwarfs. These are called 'failed stars'.

9. Star Life • http://www.learn360.com/ShowVideo.aspx?SearchText=star+colors&lid=6818736&ID=927524&player=12

10. 4. SupernovasA. Every now and again our Milky Way galaxy is lit up by a huge explosion. Known as a supernova, this violent event marks the death of a supergiant – a heavyweight star which is many times bigger than the Sun. One of the last supernovas in the Milky Way took place about 340 years ago in the constellation of Cassiopeia, so it is known as Cassiopeia A (Cas A).B. Supernovas occur when massive stars run out of nuclear fuel in their cores. Unable to give out any more energy, the core collapses, destroying the star. Supernovas are important because they spread star material across the galaxy.

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12. 5. Star Death:A. Most stars take millions of years to die. When a star like the Sun has burned all of its hydrogen fuel, it expands to become a red giant. This may be millions of kilometers across - big enough to swallow the planets Mercury and Venus.B. The star will collapse to form a very dense (thick) white dwarf. One teaspoon of material from a white dwarf would weigh up to 100 tons. Over billions of years, the white dwarf cools and becomes invisible.

13. C. Stars heavier than eight times the mass of the Sun end their lives very suddenly. When they run out of fuel, they swell into red supergiants. They try to keep alive by burning different fuels, but this only works for a few million years. Then they blow themselves apart in a huge supernova explosion. D. For a week or so, the supernova outshines all of the other stars in its galaxy. Then it quickly fades. All that is left is a tiny, dense object – a neutron star or a black hole – surrounded by an expanding cloud of very hot gas. E. The elements made inside the supergiant (such as oxygen, carbon and iron) are scattered through space. This stardust eventually makes other stars and planets.

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15. CONSTELLATIONSWHAT IS A CONSTELATION?List of constellations: http://www.astro.wisc.edu/~dolan/constellations/constellation_list.html6. A constellation is a group of stars that make an imaginary shape in the night sky. They are usually named after mythological characters, people, animals and objects. In different parts of the world, people have made up different shapes out of the same groups of bright stars. It is like a game of connecting the dots. In the past creating imaginary images out of stars became useful for navigating at night and for keeping track of the seasons. Because all the stars are at different distances, the constellations would look totally different to inhabitants of another planet orbiting another star.

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17. GALAXY • A GALAXY IS A GROUP OF STARS, GAS, AND DUST HELD TOGETHER BY GRAVITY.

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19. TYPES OF GALAXIES • A. Elliptical Galaxy: Nearly spherical to oval in shape, and they consist of a tightly packed group of relatively old stars.

20. B. Spiral Galaxy: Consist of a large, flat disk of interstellar gas and dust with star clusters extending from the disk in a spiral pattern. Our galaxy, the Milky Way, is a spiral galaxy.

21. C. Barred Spiral Galaxy: Sometimes the flat disk that forms the center of a spiral galaxy is elongated into a bar shape. Two arms containing clusters of stars swirl out from either end of the bar, forming what is known as a Barred Spiral Galaxy.

22. D. Irregular Galaxy: A few galaxies are neither spiral nor elliptical. Their shape seems to follow no set pattern, so astronomers have given them the general classification of irregular.