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Description
Presolar grains are microscopic meteoritic dust particles that condensed in the outflows of ancient stars and supernova ejecta before the formation of the Solar System, preserving a direct isotopic record of stellar nucleosynthesis and astrophysical processes. Most presolar grains originate from asymptotic giant branch (AGB) stars and core-collapse supernovae (CCSNe) [1]. Due to the long evolutionary timescales of AGB stars, only relatively long-lived radionuclides such as 26Al (t1/2 = 0.72 Ma) and 41Ca (t1/2 = 0.1 Ma) have been detected in AGB-derived grains, e.g., [2]. In contrast, the rapid explosive nucleosynthesis in CCSNe produces a wide range of short-lived radioactive isotopes, which could be incorporated into dust condensing shortly after the explosion. Previous studies have identified 26Al, 41Ca, 32Si (t1/2 = 172 a), 44Ti (t1/2 = 60 a), and 49V (t1/2 = 330 d) in presolar supernova grains [3–7].
In this study, we systematically investigated isotopes from C to Cu in presolar supernova SiC grains isolated from the Murchison meteorite. High-resolution NanoSIMS ion imaging was employed to minimize contamination, ensuring accurate determination of intrinsic stellar signatures. We report the first detection of 63Ni (t1/2 = 100 a) in presolar supernova grains, along with spatial correlations of 26Mg with 27Al and 44Ca with 48Ti, confirming the initial presence of 26Al and 44Ti – the parent isotopes of 26Mg and 44Ca, respectively. Our new inferred initial abundances of 32Si, 41Ca, and 63Ni – produced by neutron-burst nucleosynthesis in He-rich layers during the explosion [8] – allow us to assess uncertainties in (n,γ) cross sections and to constrain neutron exposure conditions, providing insights into the explosion energies of their parent CCSNe.
Furthermore, our new Ti isotope data support an earlier finding that supernova SiC grains condensed after the decay of 49V (t1/2 = 330 d) [7]. This aligns with the incorporation of a substantial amount of 137Ba, the decay product of 137Cs (t1/2 = 30 a) [9], indicating late-stage SiC grain formation following the explosions of their supernovae.
Radioactive isotopes in presolar supernova grains serve as powerful tracers of explosion dynamics, nucleosynthesis pathways, and grain formation timing, offering unique insights into the physical conditions and processes governing CCSNe.
References: [1] Liu N. (2025) Treatise on Geochemistry (Third Edition) 7: 113–145. [2] Nittler L. R. et al. (2008) The Astrophysical Journal 682: 1450–1478. [3] Amari S. et al. (1996) The Astrophysical Journal 470: L101–L104. [4] Nittler L. R. et al. (1996) The Astrophysical Journal 462: L31–L34. [5] Hoppe P. et al. (2002) The Astrophysical Journal 576: L69–L72. [6] Pignatari M. et al. (2013) The Astrophysical Journal Letters 767: L22. [7] Liu N. et al. (2018) Science Advances 4: eaao1054. [8] Meyer B. S. et al. (2000) The Astrophysical Journal 540: L49–L52. [9] Ott U. et al. (2019) The Astrophysical Journal 885: 128.
| Career stage | Tenured mid-to-late-career researcher |
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