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

Ertel, Adrienne F.

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

Description

Title

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

Author(s)

Ertel, Adrienne F.

Issue Date

2022-10-20

Director of Research (if dissertation) or Advisor (if thesis)

Fields, Brian

Doctoral Committee Chair(s)

Fields, Brian

Committee Member(s)

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

Department of Study

Astronomy

Discipline

Astronomy

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• supernova
• nucleosynthesis
• astrophysical dust processes
• nuclear abundances

Abstract

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.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Adrienne F. Ertel

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