Triggering protostellar collapse, injection, and disk formation

Certain meteoritical inclusions contain evidence for the existence of short -lived radioactivities such as Al-26 and Ca-41 at the time of their formati on 4.566 billion years ago. Because the half-lives of these nuclides are so short, this evidence requires that no more than about a million years elap sed between their nucleosynthesis and their inclusion in cm-sized solids in the solar nebula. This abbreviated time span can be explained if these nuc lides were synthesized in a stellar source such as a supernova, and were th en transported across the interstellar medium by the resulting shock wave, which then triggered the gravitational collapse of the presolar molecular c loud core. Detailed 2D and 3D numerical hydrodynamical models are reviewed and show that such a scenario is consistent with the time scale constraint, and with the need to both trigger collapse and to inject shock-wave matter into the collapsing protostellar cloud and onto the protoplanetary disk fo rmed by the collapse.