Protostellar collapse: rotation and disk formation

TL;DR

This paper reviews recent calculations on rotating molecular cloud core collapse, highlighting the rapid formation of preplanetary disks, angular momentum redistribution, and the potential outward transport of CAIs in early stellar evolution.

Contribution

It provides new insights into the timescales of disk formation, angular momentum dynamics, and the origin of CAIs during protostellar collapse, based on recent computational models.

Findings

Preplanetary disks form within about one free-fall time.

Angular momentum redistribution influences core evolution significantly.

CAIs can be transported outward and preserved in the disk.

Abstract

We present some important conclusions from recent calculations pertaining to the collapse of rotating molecular cloud cores with axial symmetry, corresponding to evolution of young stellar objects through classes 0 and begin of class I. Three main issues have been addressed: (1) The typical timescale for building up a preplanetary disk - once more it turned out that it is of the order of one free-fall time which is decisively shorter than the widely assumed timescale related to the so-called 'inside-out collapse'; (2) Redistribution of angular momentum and the accompanying dissipation of kinetic (rotational) energy - together these processes govern the mechanical and thermal evolution of the protostellar core to a large extent; (3) The origin of calcium-aluminium-rich inclusions (CAIs) - due to the specific pattern of the accretion flow, material that has undergone substantial chemical and mineralogical modifications in the hot (exceeding 900 K) interior of the protostellar core may have a good chance to be advectively transported outward into the cooler remote parts (beyond 4 AU, say) of the growing disk and to survive there until it is incorporated into a meteoritic body.