Chemical Enrichment of the Young Solar System

Dr. Heitsch and his team model how hot, diffuse supernovae ejecta are integrated into turbulent molecular clouds and collapsing dense, molecular cloud cores. They assess the mixing efficiencies and mixing timescales for the fraction of supernova ejecta that can enter into the densest parts of molecular clouds which then can collapse into cores and finally become stars. One of the issues being studied is whether ejecta have to be mixed with the diffuse gas which subsequently gets compressed into collapsing objects, or whether they can be injected directly into dense cores. One specific aspect is to determine the fate of the short-lived radioactive nuclides (those with half-lives around a few million years) that are produced in supernovae. This has direct implications for formation models of our solar system because such short-lived radioactive nuclides were present when the solar system formed.

The improvement over earlier model computations is that instead of assuming idealized, smooth molecular clouds, the clouds themselves will have been naturally assembled in large-scale flows, and thus will have inherited their turbulent density and velocity structure from first principles. The investigators test the hypothesis whether this pre-existing substructure can increase the injection efficiencies and whether this is consistent with the available constraints for the young solar system. The program will involve a series of simulations of increasing complexity, including heating and cooling, magnetic fields, self-gravity, and the Eulerian and Lagrangian tracking of supernova ejecta. Calculations are performed with fixed and adaptive resolution codes, evolving the magneto-hydrodynamical equations including the above-mentioned physics. The simulations produce predictions for the fraction and distribution of short-lived radioactive nuclides. This project provides training opportunities for a postdoc, and for undergraduate student research projects on numerical techniques and data analysis. Resulting visualizations will be made available on the web and be integrated into a public outreach program involving shows at the Morehead Planetarium and presentations on the formation of the Solar System.