Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1780494 | New Astronomy Reviews | 2006 | 5 Pages |
Abstract
We report the successful isolation and isotopic analysis of presolar graphite grains from the Orgueil CI chondrite. Isotopic measurements were made on seven density fractions, with grain sizes >1 μm: ORG1b (1.59-1.67 g cmâ3), 1c (1.67-1.75 g cmâ3), 1d (1.75-1.92 g cmâ3), 1f (2.02-2.04 g cmâ3), 1g (2.04-2.12 g cmâ3), 1h (2.12-2.16 g cmâ3) and 1i (2.16-2.30 g cmâ3). We measured C, N, O, and Si isotopes with the NanoSIMS. All the fractions, except ORG1b and ORG1h, contain presolar graphite as demonstrated by the large range of 12C/13C ratios (4-1746) measured in individual grains. The abundance of grains with isotopically light carbon increases with increasing density. Some of the low-density grains are enriched in 18O, 15N and 28Si. As the density increases, the grains mostly exhibit solar oxygen and nitrogen isotopic ratios. However, the high-density grains are enriched in 29Si and 30Si. The 18O and 28Si excesses indicate that the low-density grains originated from supernovae, while the high-density grains (with 30Si and 12C excesses) probably originated from AGB stars with low metallicities.
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Physical Sciences and Engineering
Physics and Astronomy
Astronomy and Astrophysics
Authors
Manavi Jadhav, Sachiko Amari, Ernst Zinner, Teruyuki Maruoka,