A protostar is said to have formed when a collapsing core has become dense enough that it blocks, or is opaque to, infrared radiation. It is largely the dust in the core that provides the opacity. This is important because it means that the protostar is now opaque to its own infrared radiation, which cannot escape so easily, so the protostar can begin to heat up. 3.5 Gravity is the dominant force that drives the collapse of gas clouds to form stars. Angular momentum, to some extent, inhibits gravitational collapse and thereby slows down the process of star formation.
Angular momentum plays a critical role in defining the shape of the nebular disk around a protostar.
Without gravity, stars could not form. Stars would form at a much greater rate in the absence of angular momentum and would be likely to grow more massive too.