Lifetimes of interstellar dust from cosmic-ray exposure ages of presolar silicon carbide


Dating of interstellar dust directly with astronomical methods is not possible. Neither is dating based on the decay of long-lived radioactive nuclides, due to current analytical limitations and unknown initial isotopic compositions. Here we present interstellar ages of individual presolar SiC grains from a meteorite. The ages are based on Ne isotopes produced by galactic cosmic rays. Lifetimes of ∼60% of our grains are <3 × 108 y, while at least 8% are >109 y, in line with what is expected for large grains. The former could be the end products of stars originating in an enhanced star formation episode. Presolar grains are the oldest datable solid samples available and provide invaluable insight into the presolar chronology of our galaxy.

Proceedings of the National Academy of Science