Image: Scientific American

An Astrophysical Journal Letters paper by Alan Boss and Sandy Keiser entitled, “Who Pulled the Trigger: A Supernova or an Asymptotic Giant Branch Star” was featured in the 25 June Editor’s Choice section of Science and is now the lead story in yesterday’s Scientific American. The inclusion of the products of now-extinct, short-lived radioisotopes, such as ⁶⁰Fe, in primitive meteorites shows that the parent isotopes were active at the time they were incorporated into the Solar System’s earliest solids. ⁶⁰Fe is attributed to either a core-collapse supernova or an intermediate-mass asymptotic giant (AGB) star. Sun-like stars end their lives as AGB stars or supernovae, expelling their outer envelopes and shining as planetary nebulae as their hot surfaces are exposed, ionizing material around them. The article by Boss and Keiser is dedicated to the memory of Elizabeth A. Myhill, who began the FLASH code effort at DTM.

The death of stars drives shock fronts into the interstellar medium, a process that is believed to have triggered the collapse of the cloud from which the Sun formed and led to thie injection into the cloud of synthesized radioisotopes. Using numerical simulations to test both supernova and AGB stars as candidate triggers for Solar System formation, Boss and Keiser show that only supernovae have thin enough shock waves to inject the material necessary to match the abundances of short-lived radioisotopes in primitive meteorites.