Presolar corundum and spinel in ordinary chondrites: origins from AGB stars and a supernova.
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.
Choi
B G
BG
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. bchoi@gps.caltech.edu
Huss
G R
GR
Wasserburg
G J
GJ
Gallino
R
R
D000535:Aluminum / Q000032:analysis; D055580:Astronomical Phenomena; D001256:Astronomy; D008274:Magnesium / Q000032:analysis; D019110:Meteoroids; D010087:Oxides / Q000032:analysis; D010100:Oxygen / Q000032:analysis*; D010103:Oxygen Isotopes / Q000032:analysis; D014025:Titanium / Q000032:analysis
D010087:Oxides; D010103:Oxygen Isotopes; D000535:Aluminum; D014025:Titanium; D008274:Magnesium; D010100:Oxygen