Presolar Grains from Novae: Evidence from Neon and Helium Isotopes in Comet Dust Collections

TL;DR

This study provides isotopic evidence from comet dust that supports the existence of presolar grains originating from neon novae, confirming their contribution to early solar system material.

Contribution

It presents new isotopic measurements of neon and helium in comet dust particles that match theoretical predictions for neon nova ejecta, indicating presolar grains from novae.

Findings

Neon and helium isotope ratios match neon nova nucleosynthesis models.

Absence of 3He indicates recent space exposure, consistent with cometary origin.

Evidence supports presolar grains from novae in early solar system material.

Abstract

Presolar grains in meteorites and interplanetary dust particles (IDPs) carry non-solar isotopic signatures pointing to origins in supernovae, giant stars, and possibly other stellar sources. There have been suggestions that some of these grains condensed in the ejecta of classical nova outbursts, but the evidence is ambiguous. We report neon and helium compositions in particles captured on stratospheric collectors flown to sample materials from comets 26P/Grigg-Skjellerup and 55P/Tempel-Tuttle that point to condensation of their gas carriers in the ejecta of a neon (ONe) nova. The absence of detectable 3He in these particles indicates space exposure to solar wind (SW) irradiation of a few decades at most, consistent with origins in cometary dust streams. Measured 4He/20Ne, 20Ne/22Ne, 21Ne/22Ne and 20Ne/21Ne isotope ratios, and a low upper limit on 3He/4He, are in accord with calculations of nucleosynthesis in neon nova outbursts. Of these, the uniquely low 4He/20Ne and high 20Ne/22Ne ratios are the most diagnostic, reflecting the large predicted 20Ne abundances in the ejecta of such novae. The correspondence of measured Ne and He compositions in cometary matter with theoretical predictions is evidence for the presence of presolar grains from novae in the early solar system.