Home / Colloquium / When Stars Attack! Near-Earth Supernova Explosions Revealed by Deep-Ocean and Lunar Radioactivity (Remote Only)
September 22, 20224:00 pm – 5:00 pm (CDT)
When Stars Attack! Near-Earth Supernova Explosions Revealed by Deep-Ocean and Lunar Radioactivity (Remote Only)
Brian Fields (University of Illinois Urbana Champaign)
Supernova explosions are multimessenger particle engines, they create many of the elements essential for planets and life, and they play central roles in galaxy evolution.Yet these awesome events take a sinister shade when they occur close to home, because an explosion nearby can pose a grave threat to Earthlings. We will show how radionuclides produced by supernovae can reveal nearby events in the geologic past, and we will highlight isotopes of interest. In particular, geological evidence for live 60Fe has recently been confirmed globally in multiple sites of deep-ocean material, in cosmic rays, and in lunar samples. We will review astrophysical 60Fe production sites and show that the data demand that at least one core -collapse supernova exploded near the Earth over the past few Myr, and explain how debris from the explosion was transported to the Earth as a “radioactive rain.” New measurements now also reveal a second, earlier supernova, and the presence of 244Pu that offers a unique new probes the production of the heaviest elements in the cosmos. Deep-ocean and lunar radioactivities thus represent a laboratory for supernova astrophysics, but also with implications for geology, astrobiology, and possibly terrestrial evolutionary biology.