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SPIRAL GALAXIES |
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Spiral galaxies are the most beautiful of all galaxies. They can be 10,000 miles across and contain 1-100 billion stars. |
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These galaxies look like flat disks with a bright centers and arms that extend from its center. Our galaxy, the Milky Way, is a spiral galaxy. |
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ELLIPTICAL GALAXIES |
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Elliptical galaxies are the most common galaxies of the three. They may contain 10 trillion stars and can be 100,000 parsecs in diameter. |
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These galaxies have little or no gas, and most of the stars are close in the center. That is why they look like a big, bright, spherical ball. |
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IRREGULAR GALAXIES |
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| Irregular galaxies are just that, irregular. They do not fit into the other categories. |  |
They make up about 25% of all galaxies. They look like a random group of stars. |
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BIRTH OF A STAR |
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When there are clouds of nebulae it is likely that a star would be formed. When gravity pulls the densest of nebula into a ball of gas. |
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As this ball grows, it gets hotter and hotter and nuclear reactions start and give out light and heat. This is how our sun was formed 4.6 billion years ago. |
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DEATH OF A STAR |
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When the energy-giving reactions inside a star start turning hydrogen into helium, the destruction process stars to begin. |
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When the hydrogen fuels runs out, the star swells, the surface cools, and the surface turns red. This is called a red giant. Then it starts to collapse and they form a black hole. |
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<<<Our sun, which is a star. |
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Possibly what our sun will look like if it becomes a red giant. >>> |
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