Richard B. Larson investigated the collapse of a protostar using numerical fluid dynamics. His 1969 calculations followed a spherically symmetric gas cloud and found a strongly nonuniform collapse: a small central core reached stellar mass density before most of the surrounding envelope had fallen very far.
This result separates formation of the first dense core from assembly of the final star. Subsequent accretion from the envelope can continue after the center has stopped collapsing. The imposed spherical symmetry makes the calculation tractable while excluding rotationally supported disks and other nonspherical structures.[ref]
Numerical Calculations of the Dynamics of a Collapsing Proto-Star by Richard B. Larson. Abstract: spherical collapse, small initial core and subsequent infall
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