Brown Dwarf

An artist's impression of a Brown Dwarf
Credit: NASA/JPL-Caltech

Brown dwarfs are very dim, glowing objects that never gained enough mass to become fully fledged stars. In other words, the temperatures and pressures at their centres never got high enough for nuclear fusion to start.

Brown dwarfs occupy the mass range between that of large gas giant planets and the lowest mass stars, i.e. somewhere between 12 and 75 times the mass of the planet Jupiter. Whilst most have been found orbiting stars, some have been found roaming alone in the cosmos.

These sub-stellar objects will have formed in the same way as stars, but glow a cool brownish colour due to thermal energy (or heat) created by the collisions of material within them.