Main-sequence star
= Main-sequence star
A <main-sequence star> is a <star> powered predominantly by sustained <hydrogen burning> in its core. <Hydrostatic equilibrium> balances <gravity> with a <pressure gradient>, while <thermal equilibrium> approximately balances the nuclear energy supply with losses. The <Sun> is an example; a <red dwarf> is a cooler, lower-mass example.
Membership in the <main sequence> describes an evolutionary state, rather than simply small size or low <luminosity>. A <white dwarf> can be hotter and smaller while lacking sustained core <hydrogen burning>. Within the <main sequence>, a steep <mass-luminosity relation> makes massive <stars> consume their accessible fuel faster, so a larger fuel supply does not necessarily give a longer <main-sequence lifetime>.