Supernovae are major engines of nucleosynthesis, and create many of the elements essential for life. Yet these awesome events take a sinister shade when they occur close to home, because an explosion very nearby would 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 multiple core-collapse supernovae exploded near the Earth over the past ~7 Myr, and explain how debris from the explosion was transported to the Earth as a “radioactive rain.” Deep-ocean and lunar 60Fe measurements thus represent a new tool for astronomy and astrophysics, but also with implications for geology, astrobiology, and possibly terrestrial evolutionary biology.

About the Speaker:

Brian Fields is a professor of Astronomy and of Physics at the University of Illinois. His PhD is from the University of Chicago, and he has been at Illinois since 1998. Prof. Fields is fascinated by the "inner space/outer space" connections that link the science at the smallest and largest scales. His research focuses on the highest-energy sites in nature--the big bang, exploding stars (supernovae), and high-energy particles in space (cosmic rays).
                   
Return to Schedule