Presolar Graphite from the Murchison Meteorite: Imprint of Nucleosynthesis and Grain Formation
- Laboratory for Space Sciences, Washington University, St. Louis, MO 63130-4899 (United States)
- Dipartimento di Fisica Generale, Universita' di Torino, I-10125 Turin (Italy)
- INAF Osservatorio Astronomico di Roma, I-00040 Rome (Italy)
- Instituto di Astrofisica Spaziale e Fisica Cosmica (CNR), I-00133, RomE (Italy)
Presolar graphite is the carrier of Ne-E(L) and most 22Ne in Ne-E(L) had long been attributed to radiogenic decay of 22Na from novae. Of presolar graphite grains with a range of density (1.6-2.2g/cm3), low-density graphite grains extracted from the Murchison meteorite are characterized by 18O excesses and Si isotopic anomalies and are believed to have formed in supenova ejecta. From noble gas analyses of low-density graphite grains, we conclude that 22Ne in the grains is from the in situ decay of 22Na (T1/2=2.6a) produced in the C-burning zone in presupernova stars. The grains also contain Kr that was produced by neutron capture, either in the He-burning zone or the C-burning zone during hydrostatic burning. The 22Ne of a 22Na origin indicates that the grains formed shortly after the explosion. The presence of 22Ne of a 22Na origin and Kr, and the absence of 22Ne of a non-radiogenic origin might give us a further clue for graphite formation in supernova ejecta.
- OSTI ID:
- 20877441
- Journal Information:
- AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 847; ISSN APCPCS; ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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