A white dwarf which has stopped radiating energy: A black dwarf is a hypothesized dying star that has little mass, more solid and dense, but less bright than the the Sun. A black dwarf has cooled down and no longer emits visible light.

An object less massive than a star, but heavier than a planet: A brown dwarf star is a theoretical "star" and does not have enough mass to ignite nuclear reactions at their centers, but shine by heat released during their contraction from a gas cloud.

Some astronomers believe that vast numbers of brown dwarf stars exist throughout the galaxy, but because of the difficulty in detecting them, none of them were discovered until 1995, when U.S. astronomers discovered a brown dwarf star in the constellation Lepus (Hare).

A celestial body that orbits the sun and has a spherical shape but is not large enough to disturb other objects from its orbit.

A small, relatively cool star with low luminosity: A red dwarf is an old and cool star that is rather small compared to other stars, but it is still bigger than Jupiter, for example.

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.