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VERA Seminar

Discovery of Supernova-produced 60Fe in the Earth's Fossil Record

Shawn Bishop, Physik Department der Technischen Universität München

Approximately 1.8 to 2.8 Myr before the present our planet was subjected to the debris of a supernova explosion. The terrestrial proxy for this event was the discovery of live atoms of 60Fe in a deep-sea ferromanganese crust [1]. The signature of this supernova event should also reside in magnetite (Fe3O4) magnetofossils produced by magnetotactic bacteria [2], which live in the ocean sediments, extant at the time of the Earth-supernova interaction. We have conducted accelerator mass spectrometry (AMS) measurements, searching for live 60Fe atoms in the magnetofossil component of Pacific Ocean sediment cores (ODP cores 848 and 851). We find a time-resolved 60Fe signal in both sediment cores, above background, centered at approximately 2 Myr ago and spanning approximately 700 kyr duration (full width half maximum), which will require eventual astrophysical interpretation to understand.
This talk is designed to be accessible to a broad audience.

[1] Knie et al., 60Fe anomaly in a deep-sea manganese crust and implications for a nearby supernova source, Phys. Rev. Lett. 93 (2004) 171103.       
[2] S. Bishop and R. Egli, Discovery prospects for a supernova signature of biogenic origin, Icarus 212 (2011) 960.

 

Donnerstag, 03.12.2015    16:30 Uhr

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