Brown dwarf

Brown dwarfs are substellar objects not massive enough to sustain hydrogen-1 fusion reactions in their cores, unlike main-sequence stars. Brown dwarfs occupy the mass range between the heaviest gas giants and the lightest stars, with an upper limit around 75 to 80 Jupiter masses (M_J). Brown dwarfs heavier than about 13 M_J are thought to fuse deuterium and those above ~65 M_J, fuse lithium as well. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.