Animation showing the relative sizes of the Earth and a white dwarf star. A white dwarf is the last stage of the life of a Sun_like star, indeed any star of less than around eight solar masses. Stars like the Sun produce energy by fusing hydrogen to helium, and later in their life, helium to carbon and oxygen. If the star has less than around eight solar masses, the internal pressures and temperatures do not reach a level at which carbon and oxygen can be fused, and the star collapses under its own gravity. This produces a white dwarf, with the mass of the Sun compacted into an object around the same size as the Earth some 109 times smaller than the Sun. White dwarfs produce no energy, and are only supported by electron degeneracy pressure. They are extremely hot when they form, however, so radiate heat energy in the visible part of the spectrum. They will cool oer billions of years, eventually forming invisible black dwarfs, but the universe is too young for that to have occurred yet.