= Star formation
{wiki}
<Star formation> is the conversion of interstellar gas into self-gravitating <protostars> and eventually <stars>. A region can contract when <gravity> overcomes support from gas <pressure> and other motions or fields. Cooling matters because it removes compression energy: during approximately <isothermal fragmentation>, rising <mass density> lowers the <Jeans mass>, permitting smaller regions to collapse independently.
When the gas becomes opaque and cannot cool efficiently, <adiabatic suppression of fragmentation> changes that behaviour. A <first hydrostatic core> and <second protostellar collapse> describe successive physical stages rather than two arbitrary labels for the same contraction. <Accretion>, rotation and <magnetic fields> affect the resulting objects, while stellar feedback limits how much gas becomes stellar <mass>. The <initial mass function> summarizes the resulting birth-mass distribution.
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