Glossary of Astronomical Terms/brown dwarf

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A brown dwarf is an astronomical object that has insufficient mass to allow its internal gravity to compress and heat the hydrogen in its core to fusion point.

A brown dwarf has a mass between 13 and 75-80 Jovian masses. Anything more massive would be a star; anything less massive a Jovian-type planet.

Brown dwarfs are not really brown: they glow mostly in the infrared, with some newer-created brown dwarfs glowing red, from 1500 to 2000 Kelvins. The phrase came into being only as a way to distinguish brown dwarfs from red dwarfs and black dwarfs.

One feature that distinguishes a brown dwarf from a star is the presence of methane (CH4) in its composition. Stars make carbon as part of the fusion process, but the carbon in stars usually combines with oxygen to form carbon monoxide (CO).

Several brown dwarfs have been discovered, usually in orbit around main sequence stars.