Research Article

Presolar Corundum and Spinel in Ordinary Chondrites: Origins from AGB Stars and a Supernova

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Science  13 Nov 1998:
Vol. 282, Issue 5392, pp. 1284-1289
DOI: 10.1126/science.282.5392.1284

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On the basis of anomalous isotopic compositions of oxygen and magnesium, 14 oxide grains from two primitive meteorites (Bishunpur and Semarkona) have been identified as circumstellar condensates. One corundum grain has a high 18O/16O ratio and isotopic compositions of magnesium, calcium, and titanium that are compatible with a formation in ejecta of a type II supernova that was about 15 times the mass of the sun. The other grains have oxygen, magnesium, and titanium compositions that are consistent with a formation around asymptotic giant branch (AGB) stars with a range of mass and initial composition. The large range of aluminum/magnesium in circumstellar corundum and spinel is considered to reflect various stages of back-reaction between condensed corundum and gaseous magnesium in cooling stellar ejecta.

  • * To whom correspondence should be addressed: E-mail: bchoi{at}

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