Some aspects of triggered star formation

A summary is given of the extinct radioactivities found in primitive solar system material. The only astronomical source that seems capable of producing all five of the lightest (and shortest-lived) of these nuclides is a core collapse supernova situated a few parsecs away from the molecular cloud core that is to form the solar system. The collapse process is discussed, and it is shown that only a shock-triggered collapse can occur in a short enough time to allow Ca-41 to appear live in solar system material. Discussions are given of the thermodynamics of molecular hydrogen and its influence on compression and collapse in the cloud core. SPH simulations of shock induced core collapse are reported. It is shown how a plane shock wave can produce a binary system if the central core density is not too great. Finally, an HR diagram of young T Tauri stars is interpreted to indicate that shock induced star formation is probably common.