Collapse of the presolar nebula

The hydrodynamical axially symmetric collapse of a 3 solar mass-cloud with an initial density of 10-20 g cm-3 has been investigated. In order to first arrive at an equilibrium configuration a temperature of 15 K has been assumed. During about 9 free-fall times the cloud has artificially been cooled down to the (Jeans-) critical temperature of 8 K. Thus, the dynamical collapse studied in this paper starts from an equilibrium configuration following a slow quasi-hydrostatic contraction. Two sequences corresponding to a different choice of the initial angular velocity Ωsub(i) = 10-14 s-1 (Case A) and Ωsub(i) = 10-15s-1 (Case B) have been computed. In both cases a fast spinning, optically thick disk-like core of low mass and temperature forms for which fission into two or even more pieces is very likely to occur. (Auth.)