The collapsed remnant core of a low-mass star that has ejected its outer layers and can no longer sustain nuclear fusion. White dwarf stars are extremely dense, having no empty space between atoms, but lack the mass to reach the even more extremely dense states of a neutron star or black hole.
A planet-sized, very dense, collapsed star, the fuel of which has been exhausted: initially very bright and hot, it gradually evolves into a black dwarf.
A small, extremely dense star characterized by high temperature and luminosity. A white dwarf is believed to be in its final stage of evolution, having either used up most of its nuclear fuel in its main-sequence stage, or else moved through a giant stage and shed any remaining fuel in its outer layer as a planetary nebula , leaving only a glowing core. Some 10 percent of all stars in the Milky Way are white dwarfs, but despite their intrinsic luminosity, they are so small that none are visible to the naked eye.