A type of star that has collapsed after exhausting its nuclear fuel: A white dwarf is a dense, small low-luminosity star of mass less than the Chandrasekhar limit (1.4 solar masses) left as the remnant of a supernova explosion.

Leftover heat causes a white dwarf to shine faintly.

A star may remain a giant or supergiant for several million years before all nuclear reactions cease.

Gravitational collapse then occurs with no outward pressure to stop it, and the final result may be a white dwarf.

Such a white dwarf is small, about the same size as the Earth, but has about one million times the density of water and the temperature at the surface is a hundred thousand degrees, yet the luminosity is quite low; about one-thousandth of the sun.