Artist conception of a T-type brown dwarf.
A brown dwarf is a substellar object that occupies the mass range between the heaviest gas giant planets and the lightest stars, of approximately 13 to 75-80 Jupiter masses. Below this range are the sub-brown dwarfs, and above it are the lightest red dwarfs (M9 V). Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.