Journal article Open Access

Observation of 23 Supernovae That Exploded

Firestone, R. B.

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      <creatorName>Firestone, R. B.</creatorName>
      <givenName>R. B.</givenName>
    <title>Observation of 23 Supernovae That Exploded</title>
    <date dateType="Issued">2014-06-11</date>
  <resourceType resourceTypeGeneral="JournalArticle"/>
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    <relatedIdentifier relatedIdentifierType="DOI" relationType="IsIdenticalTo">10.1088/0004-637x/789/1/29</relatedIdentifier>
    <rights rightsURI="info:eu-repo/semantics/openAccess">Open Access</rights>
    <description descriptionType="Abstract">Four supernovae (SNe), exploding 300 pc from Earth, were recorded 44, 37, 32, and 22 kyr ago in the radiocarbon (14C) record during the past 50 kyr. Each SN left a nearly identical signature in the record, beginning with an initial sudden increase in atmospheric radiocarbon, when the SN exploded, followed by a hiatus of 1500 yr, andconcluding with a sustained 2000 yr increase in global radiocarbon due to γ -rays produced by diffusive shock in the SN remnant (SNR). For the past 18 kyr excess radiocarbon has decayed with the 14C half-life. SN22kyrBP,
is identified as the Vela SN that exploded 250 ± 30 pc from Earth. These SN are confirmed in the 10Be, 26Al, 36Cl, and NO−3 geologic records. The rate of near-Earth SNe is consistent with the observed rate of historical SNe giving a galactic rate of 14 ± 3 kyr−1 assuming the Chandra Galactic Catalog SNR distribution. The Earth has been used as a calorimeter to determine that ≈2 × 1049 erg were released as γ -rays at the time of each SN explosion and ≈1050 erg in γ -rays following each SN. The background rate of 14C production by cosmic rays has been
determined as 1.61 atoms cm−2 s−1. Approximately 1/3 of the cosmic ray energy produced by diffusive shock in the SNR was observed to be emitted as high-energy γ -rays. Analysis of the 10Be/9Be ratio in marine sediment identified 19 additional near-Earth SNe that exploded 50–300 kyr ago. Comparison of the radiocarbon record with global temperature variations indicated that each SN explosion is correlated with a concurrent global warming of ≈3◦C–4◦C..</description>
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