Paleo-astronomy: investigations of terrestrial 60Fe forged in near-Earth supernovae

A plethora of evidence now demonstrates that radioactive 60Fe from two near-Earth supernovae was deposited on Earth in the recent geologic past, beginning at 3 and 7 Myr ago. This work synthesizes all of the detected 60Fe relating to the two supernovae and performs statistical analysis to determine the raindown (fallout) timescale for the 60Fe dust falling on Earth. We find that this timescale is ≳ 1 million years — an order of magnitude larger than the conventional Sedov-profile for the supernova blast wave sweeping over the solar system. We examine the pinball model of charged dust inside a magnetic supernova remnant as a possible mechanism to extend the raindown time to match the observed data, concluding that with this model we are able to reproduce the 60Fe signal seen in deep-sea sediments with a single supernova blast. We then use the fluence (time-integrated flux) from the 60Fe samples to recalculate the distance to the 3 Myr ago supernova. We examine the effects that the full range of the astronomical parameters have on the distance, finding that the ejected mass of 60Fe from the supernova and the fraction of 60Fe that arrives at Earth in dust form play the largest role in the resulting distance estimation. We then calculate the possible distance range to the 3 Myr ago supernova as D ∼ 20 − 140 pc, with a most likely range of D ∼ 50 − 60 pc. Finally, we consider the case of whether atmospheric damage from a 20 pc supernova could have contributed to the End-Devonian extinction and examine possible radioisotope signatures that could be used to show the presence of a supernova.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Astronomy

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Ertel, Adrienne F.

Contributors dc:contributor

• Fields, Brian
• Ricker, Paul
• Liu, Xin
• Looney, Leslie

• Supernova
• Nucleosynthesis
• Astrophysical Dust Processes
• Nuclear Abundances

Statement dc:rights

• Copyright 2022 Adrienne F. Ertel

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/117722

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F117722