Mass Main sequence stars range in mass from 0.08 M☉. The lower limit on mass in due to degeneracy. As a protostar contracts, its core grows both denser and hotter. Its increasing temperature brings it steadily nearer the development of fusion in its core. Its increasing density brings it steadily nearer degeneracy. For a star more massive than 0.08 M☉, fusion begins before degeneracy is reached, so the star begins its main sequence career. For a less massive star, degeneracy develops before hydrogen fusion begins. After the star becomes degenerate, the pressure supplied by its degenerate electrons doesn’t’ depend on temperature. The star stops contracting and begins to grow cooler and dimmer. Perhaps such and object shouldn’t be called a star at all, because it never generates a significant amount of nuclear energy. The term brown dwarf is often used to refer to objects that narrowly miss becoming nuclear stars.