White Dwarfs

Where a star ends up at the end of its life depends on the mass it was born with. Stars that have a lot of mass may end their lives as black holes or neutron stars. A low or medium mass star (with mass less than about 8 times the mass of our Sun) will become a white dwarf. A typical white dwarf is about as massive as the Sun, yet only slightly bigger than the Earth. This makes white dwarfs one of the densest forms of matter, surpassed only by neutron stars and black holes.

Medium mass stars, like our Sun, live by fusing the hydrogen within their cores into helium. This is what our Sun is doing now. The heat the Sun generates by its nuclear fusion of hydrogen into helium creates an outward pressure. In another 5 billion years, the Sun will have used up all the hydrogen in its core.
 
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