A brown dwarf is a type of substellar object occupying the mass range between the heaviest gas giant planets and the lightest stars, having a mass between approximately 13 and 75–80 times that of Jupiter (MJ), or approximately 2. 5×1028 kg to about 1. 5×1029 kg. Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the lightest red dwarfs. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.