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Physical Environment > White Dwarf Star |
This site tells the story of the history of the universe. Click Earlier and Later to follow the story. Note: Many facts have been simplified to make them easier to understand. |
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Some red giants die quietly. A white dwarf is created when a small red giant (with about as much mass as the Sun) runs out of fuel, cools and begin to contract under gravity. The contraction of the inner parts of the star releases heat which causes the outer parts to expand and gently get blown away. In this way the gas of old stars is released and can be formed into new stars.
The inner part of the star continues to contract until it reaches the size of the Earth. Then its atoms are crushed together so tightly that their electrons begin to overlap. Because two electrons cannot occupy the same space, they repel each other. This is called the exclusion principle. The electrons cannot be compressed further and so create a force called degeneracy pressure. This small squashed cinder of matter is called a white dwarf star, although it does not shine like a normal star. Next we see that some stars become white dwarves are formed in a more spectacular way. Note that if the red giant is more than 1.5 times the mass of the Sun it does not become a white dwarf. Instead it becomes a neutron star or a black hole. |
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Physical Environment > White Dwarf Star |
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Basic Information |
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