White dwarf!

1. White dwarf! The stage before it becomes black

2. White Dwarf stars are created when a planetary nebula’s center star collapses. It is all that is left • The white dwarf is compressed to one millionth the size of the original star. For example, if a star is the size of a car, than when it reaches the white dwarf stage it will be the size of an olive

4. The degenerate electrons in a white dwarf move extremely fast, but since they are degenerate the laws of physics prevent them from losing energy. • But the atomic nuclei (protons and neutrons) are not degenerate, thus they can lose energy • No other energy is generated • White Dwarfs are retired stars spending whatever they have left

5. Eventually, (after about 10 billion years) the nuclei cool down. • Luminosity drops • And we’re left with a black dwarf (a cool white dwarf which no longer shines)

6. White Dwarfs are pretty much the last stage in a stars life • White Dwarfs are made up of primarily carbon and oxygen • They are usually about the size of earth • They are held together by electron degeneracy pressure • It shines because the nuclei in the star are losing energy, radiating light away into space

8. Electron Degeneracy : Quantum mechanics restricts the number of electrons that can have low energy. Basically, each electron must occupy its own energy state. When White Dwarfs compress and begin to exist, it packs electrons together very tightly and therefore the number of low energy electrons that are allowed to exist is too low, so some electrons are forced to be at a high energy state. When this happens the electrons are said to be degenerate. These high energy electrons make a significant contribution to the pressure. Because the pressure arises from this quantum mechanical effect, it is insensitive to temperature, i.e., the pressure doesn't go down as the star cools. This pressure is known as electron degeneracy pressure and it is the force that supports white dwarf stars against their own gravity.