What state of balance marks the transition from a collapsing protostar to a main-sequence star?

Answer

Hydrostatic equilibrium

Hydrostatic equilibrium is the state reached when the internal pressure generated by extreme heat generated from collapse can finally counteract the inward pull of gravity.

What state of balance marks the transition from a collapsing protostar to a main-sequence star?
forcedensitygravitynebulaastrophysicsHeating