¹Iizuka, Tsuyoshi,^2,3Hibiya, Yuki,¹Yoshihara, Satoshi,⁴Hayakawa, Takehito
Astrophysical Journal Letters 979, L29 Open Access Link to Article [DOI 10.3847/2041-8213/ada554]
¹Department of Earth and Planetary Science, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo, 113-0033, Japan
²Research Center for Advanced Science and Technology, The University of Tokyo, Komaba 4-6-1, Meguro, Tokyo, 153-8904, Japan
³Submarine Resources Research Center, Japan Agency for Marine-Earth Science and Technology, Kanagawa, 237-0061, Japan
⁴Kansai Institute for Photon Science, National Institutes for Quantum Science and Technology, Umemidai 8-1-7, Kizugawa, Kyoto, 619-0215, Japan

The radioactive decay of short-lived 26Al-26Mg has been used to estimate the timescales over which 26Al was produced in a nearby star and the protosolar disk evolved. The chronology commonly assumes that 26Al was uniformly distributed in the protosolar disk; however, this assumption is challenged by the discordance between the timescales defined by the Al-Mg and assumption-free Pb-Pb chronometers. We find that the 26Al heterogeneity is correlated with the nucleosynthetic stable Ti isotope variation, which can be ascribed to the nonuniform distribution of ejecta from a core-collapse supernova in the disk. We use the Al-Ti isotope correlation to calibrate variable 26Al abundances in Al-Mg dating of early solar system processes. The calibrated Al-Mg chronometer indicates a ≥1 Myr gap between parent body accretion ages of carbonaceous and noncarbonaceous chondrites. We further use the Al-Ti isotope correlation to constrain the timing and location of the supernova explosion, indicating that the explosion occurred at 20-30 pc from the protosolar cloud, 0.94 +0.25/-0.21 Myr before the formation of the oldest solar system solids. Our results imply that the Sun was born in association with a ∼25 Mʘ star.

¹Takaaki Noguchi,^2,3Takahito Tominaga,^2,4Minako Takase,⁵Akira Yamaguchi,⁵Naoya Imae
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14324]
¹Division of Earth and Planetary Science, Kyoto University, Kyoto, Japan
²Department of Earth and Planetary Science, Kyushu University, Fukuoka, Japan
³Kai Industries Co. Ltd., Gifu, Japan
⁴Fukuoka City Science Museum, Fukuoka, Japan
⁵National Institute of Polar Research, Japan, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Over a period of 16 years, we collected Antarctic micrometeorites (AMMs) preserved in 1-t snow samples from the surface to a depth of ~10–15 cm near Dome Fuji Station, Antarctica. A total of 1025 AMMs were identified: 843 unmelted AMMs, 51 scoriaceous ones, and 131 cosmic spherules. Their average sizes were 40, 64, and 40 μm, respectively. The accretion rate of AMMs was inferred to be (3.3 ± 1.8) × 103 t year−1, based on the snow accumulation rate near Dome Fuji Station. We compared the Dome Fuji collection (DFC) with our previous Tottuki #5 collection (T5C) recovered from blue ice in 2000. Regardless of the collection methods, the full range size distributions of AMMs were well fitted by lognormal functions. In 2019 and 2020, we applied a freeze-drying (FD) system to collect AMMs. We identified 21 AMMs from 17 kg of surface snow. Both GEMS (glass with embedded metal and sulfide)-rich chondritic porous (CP) AMMs and hydrated fine-grained (H f-g) AMMs were identified. No detectable mineralogical differences were observed between a CP AMM from the DFC-FD and one from the DFC, suggesting that ~6 h of exposure to cold water (<8.7°C) did not affect the mineralogy of CP AMMs.