Presolar graphite from the Murchison meteorite: Neon revisited

Presolar graphite carries an anomalous 22Ne-rich component called Ne-E(L) and has a range of density (1.6-2.2 g/cm3). Low-density graphite grains, characterized by 18O excesses and Si isotopic anomalies, are believed to have formed in Type II supernovae. More than 40% of the low-density grains are enriched in 22Ne. The 22Ne is from the decay of 22Na, but not from 22Ne that was directly implanted onto the grains. This implies that grains formed in a few years after the explosion.