A
white dwarf, also called a
degenerate dwarf, is a
stellar remnant composed mostly of
electron-degenerate matter. A white dwarf is very
dense: its mass is comparable to that of the
Sun, and its volume is comparable to that of
Earth. A white dwarf's faint
luminosity comes from the
emission of stored
thermal energy. The nearest known white dwarf is
Sirius B, at 8.6 light years, the smaller component of the Sirius
binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name
white dwarf was coined by
Willem Luyten in 1922.