Protostellar collapse: rotation and disk formation

We present some important conclusions from models of the collapse of rotating molecular cloud cores with axial symmetry, corresponding to the evolution of young stellar objects from class 0 to the beginning of class I. There are three main findings of the calculations: (1) the typical timescale for building up a preplanetary disk, which was found to be of the order of one free-fall time 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 causing the growing disk to become more stable and strengthening the intrinsic meridional circulation pattern of the accretion flow; and (3) the origin of calcium-aluminium-rich inclusions (CAIs). Because of the persistent equatorial outflow, material that has undergone substantial chemical and mineralogical modifications in the hot (greater than or similar to 900 K) interior of the protostellar core may have a good chance of being advectively transported outward into the cooler remote parts (greater than or similar to 4 AU, say) of the growing disk and surviving there until it is incorporated into a meteoritic parent body.