Speaker
Description
Recent nearby stellar explosions can deliver their ejecta to the Earth and Moon, leaving a telltale signature in the form of live (not decayed) radioisotopes in the geological record. Remarkably, there is now a wealth of evidence that this has occurred: live ${}^{60}{\rm Fe}$ is found globally and in lunar regolith samples, and recently ${}^{244}{\rm Pu}$ is also detected. These point to recent supernova activity but also to r-process activity. We will discuss the astrophysical implications of these detections, including (a) the mechanisms needed to deliver explosion debris to the Earth, (b) the progenitor scenarios that can account for the data, and (c) the tests that could distinguish among the possibilities while offering a new probe of the r-process. The larger lesson is that these recently-arrived radioisotopes represent a new kind of cosmic messenger, and that fully understanding their story requires that we weave together not only a wealth of astrophysics, but also nuclear physics, geology, and astrobiology.
| Career stage | Tenured mid-to-late-career researcher |
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