¹A Carbognani,^2,3M Fenucci
Monthly Notices of the Royal Astronomical Society 525, 1705–1725 Link to Article [https://doi.org/10.1093/mnras/stad2382]
¹INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, I-40129 Bologna, Italy
²ESA ESRIN/PDO/NEO Coordination Centre, Largo Galileo Galilei, 1, I-00044 Frascati (RM), Italy
³Elecnor Deimos, Via Giuseppe Verdi, 6, I-28060 San Pietro Mosezzo (NO), Italy

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¹Kurihara, Kanoko,^1,2Numa, Norika,¹Niki, Sota,¹Akamune, Mai,¹Nakazato, Masaki,^1,3Yamashita, Shuji,⁴Itoh, Shoichi,¹Hirata, Takafumi
Geochemical Journal 57, E9-E16 Open Access Link to Article [DOI https://doi.org/10.2343/geochemj.GJ23015]
¹Geochemical Research Center, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
²Section of Public Relations, Math Channel, 2-26-12 Yoyogi, Shibuya-ku, Tokyo, 151-0053, Japan
³National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Ibaraki, Tsukuba, 305-8563, Japan
⁴Graduate School of Science, Kyoto Univeristy, Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan

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^1,2,3Min Li,^2,4Zhaohuan Zhu,⁵Shichun Huang,⁶Ning Sui,⁷Michail I. Petaev,^2,4Jason H. Steffen
The Astrophysical Journal 958, 58 Open Access Link to Article [DOI 10.3847/1538-4357/acfb02]
¹College of Physics, Jilin Normal University, Siping, Jilin 136000, People’s Republic of China
²Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy., Las Vegas, NV 89154, USA
³Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Changchun, Jilin 130103, People’s Republic of China
⁴Nevada Center for Astrophysics, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy., Las Vegas, NV 89154, USA
⁵Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, 1621 Cumberland Ave., Knoxville, TN 37996, USA
⁶College of Physics, Jilin University, Changchun, Jilin 130012, People’s Republic of China
⁷Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St., Cambridge, MA 02138, USA

The temperatures of observed protoplanetary disks are not sufficiently high to produce the accretion rate needed to form stars, nor are they sufficient to explain the volatile depletion patterns in CM, CO, and CV chondrites and terrestrial planets. We revisit the role that stellar outbursts, caused by high-accretion episodes, play in resolving these two issues. These outbursts provide the necessary mass to form the star during the disk lifetime and provide enough heat to vaporize planet-forming materials. We show that these outbursts can reproduce the observed chondrite abundances at distances near 1 au. These outbursts would also affect the growth of calcium-aluminum-rich inclusions and the isotopic compositions of carbonaceous and noncarbonaceous chondrites.

¹Ihor Kyrylenko,^1,2Oleksiy Golubov,¹Ivan Slyusarev,³Jaakko Visuri,^3,4,5Maria Gritsevich,^1,2Yurij N. Krugly,^1,6Irina Belskaya,¹asilij G. Shevchenko
The Astrophysical Journal 953, 20 Open Access Link to Article [DOI 10.3847/1538-4357/acdc21]
¹Institute of Astronomy of V.N. Karazin Kharkiv National University, 35 Sumska Street, Kharkiv 61022, Ukraine
²Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, Poznan, Poland
³Finnish Fireball Network, Ursa Astronomical Association, Kopernikuksentie 1, Helsinki FI-00130, Finland
⁴Finnish Geospatial Research Institute, Vuorimiehentie 5, FI-02150 Espoo, Finland
⁵Department of Physics, University of Helsinki, Gustaf Hällsrömin katu 2a, Helsinki FI-00014, Finland
⁶LESIA, Observatoire de Paris, Université PSL, CNRS, Université Paris Cité, Sorbonne Université, Meudon, France

A bright fireball observed on 2020 November 7, over Scandinavia, produced the first iron meteorite with a well-determined pre-atmospheric trajectory. We calculated the orbit of this meteoroid and found that it demonstrates no close affinity with the orbit of any known asteroid. We found that the meteoroid (or its parent body) most probably entered the near-Earth orbit from the main asteroid belt via either ν₆ secular resonance with Saturn (89%) or 3:1 mean-motion resonance with Jupiter (11%). The long YORP timescale of the meteoroid suggests that it could have been produced in the main asteroid belt and survived the journey to the near-Earth orbit.

¹Peter Hoppe,^1,2Jan Leitner,^3,4,5Marco Pignatari,^6,7Sachiko Amari
The Astrophysical Journal Letters 943, L22 Open Access Link to Article [DOI 10.3847/2041-8213/acb157]
¹Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, D-55128 Mainz, Germany; peter.hoppe@mpic.de
²Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234-236, D-69120 Heidelberg, Germany
³Konkoly Observatory, Konkoly Thege Miklos ut 15-17, 1121, Budapest, Hungary
⁴E. A. Milne Centre for Astrophysics, University of Hull, HU6 7RX, Hull, UK
⁵NuGrid Collaboration, USA 8
⁶McDonnell Center for the Space Sciences and Physics Department, Washington University, St. Louis, MO 63130, USA
⁷Geochemical Research Center, The University of Tokyo, Tokyo, 113-0033, Japan

We report C, N, Mg-Al, Si, and S isotope data of six 1–3 μm-sized SiC grains of Type X from the Murchison CM2 chondrite, believed to have formed in the ejecta of core-collapse supernova (CCSN) explosions. Their C, N, and Si isotopic compositions are fully compatible with previously studied X grains. Magnesium is essentially monoisotopic ²⁶Mg which gives clear evidence for the decay of radioactive ²⁶Al. Inferred initial ²⁶Al/²⁷Al ratios are between 0.6 and 0.78 which is at the upper end of previously observed ratios of X grains. Contamination with terrestrial or solar system Al apparently is low or absent, which makes the X grains from this study particularly interesting and useful for a quantitative comparison of Al isotope data with predictions from supernova models. The consistently high ²⁶Al/²⁷Al ratios observed here may suggest that the lower ²⁶Al/²⁷Al ratios of many X grains from the literature are the result of significant Al contamination and in part also of an improper quantification of ²⁶Al. The real dispersion of ²⁶Al/²⁷Al ratios in X grains needs to be explored by future studies. The high observed ²⁶Al/²⁷Al ratios in this work provide a crucial constraint for the production of ²⁶Al in CCSN models. We explored different CCSN models, including both “classical” and H ingestion CCSN models. It is found that the classical models cannot account for the high ²⁶Al/²⁷Al ratios observed here; in contrast, H ingestion models are able to reproduce the ²⁶Al/²⁷Al ratios along with C, N, and Si isotopic ratios reasonably well.

¹Yuki Hibiya,²Tsuyoshi Iizuka,²Hatsuki Enomoto,³Takehito Hayakawa
The Astrophysical Journal Letters 942, L15 Open Access Link to Article [DOI 10.3847/2041-8213/acab5d]
¹Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904
²Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹National Institutes for Quantum Science and Technology, 2-4 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan

The short-lived radionuclide, niobium-92 (⁹²Nb), has been used to estimate the site of nucleosynthesis for p-nuclei and the timing of planetary differentiation, assuming that it was uniformly distributed in the early solar system. Here, we present the internal niobium–zirconium (Nb–Zr) isochron dating of Northwest Africa (NWA) 6704, an achondrite thought to form in the outer protosolar disk due to nucleosynthetic isotope similarities with carbonaceous chondrites. The isochron defines an initial ⁹²Nb/⁹³Nb ratio of (2.72 ± 0.25) × 10⁻⁵ at the NWA 6704 formation, 4562.76 ± 0.30 million years ago. This corresponds to a ⁹²Nb/⁹³Nb ratio of (2.96 ± 0.27) × 10⁻⁵ at the time of solar system formation, which is ∼80% higher than the values obtained from meteorites formed in the inner disk. The results suggest that a significant proportion of the solar ⁹²Nb was produced by a nearby core-collapse supernova (CCSN) and that the outer disk was more enriched in CCSN ejecta, which could account for the heterogeneity of short-lived ²⁶Al and nucleosynthetic stable-isotope anomalies across the disk. We propose that NWA 6704 serves as the best anchor for mapping relative Nb–Zr ages of objects in the outer solar system onto the absolute timescale.

¹J. N. Connelly,¹J. Bollard,¹E. Amsellem,¹M. Schiller,¹K. K. Larsen,¹M. Bizzarro
The Astrophysical Journal Letters 952, L33 Open Access Link to Article [DOI 10.3847/2041-8213/ace42e]
¹Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5–7, DK-1350, Copenhagen, Denmark; connelly@sund.ku.dk

We present a U-corrected Pb–Pb age of 4566.19 ± 0.20 Ma (1.11 ± 0.26 Myr after t₀) for the moderately volatile element rich, andesitic meteorite Erg Chech 002 (EC002). Our Al–Mg isochron defines a ²⁶Al/²⁷Al initial ratio of (8.65 ± 0.09) × 10⁻⁶ that corresponds to a ²⁶Al/²⁷Al ratio of 2.48−0.56+0.67 × 10⁻⁵ for the parent body precursor at the time of solar system formation. Whereas the published bulk chemistry and our high-precision Ca isotope measurement correspond to those for inner solar system materials, the ²⁶Al/²⁷Al ratio overlaps that for outer solar system CI chondrites. This indicates that the carriers and/or processes responsible for the nucleosynthetic isotope compositions for inner and outer disk materials are different than those controlling the heterogeneous distribution of ²⁶Al. A low μ²⁶Mg* initial value of −6.1 ± 1.7 ppm infers a source region with a subchondritic Al/Mg ratio until 1.1 Myr after t₀ such that melt generation must have immediately preceded its crystallization. With ²⁶Al as the main heating source, a modeled temperature–time path for a 100 km radius parent body with our inferred ²⁶Al abundance suggests that accretion must have occurred before 0.5 Myr after t₀ to reach melting temperatures at appropriate depths within 1.1 Myr. This requires that the parent body formed very early within the protoplanetary disk, consistent with predictions of rapid formation of planetesimals by streaming instabilities within high-density dust filaments during the earliest phase of the protoplanetary disk. Finally, an absence of initial Pb in this otherwise moderately volatile-rich achondrite implies Pb was effectively sequestered to the Fe–Ni core.

¹C. Koike, ¹H. Chihara
The Astrophysical Journal 951, 24 Open Access Link to Article [DOI 10.3847/1538-4357/acd002]
¹Department of Environmental Science and Technology, Faculty of Design Technology, Osaka Sangyo University, 3-1-1 Nakagaito, Daito, Osaka 574-8530, Japan koike-c@mua.biglobe.ne.jp

The presence of amorphous silicate particles in interstellar and circumstellar space has been suggested based on the observation of 9.7 and 18 μm emission bands. We have successfully synthesized amorphous silicate samples of an enstatite and forsterite composition by the mechanical milling of mixed powder consisting of SiO2–MgO and SiO2–Mg(OH)2 reagent-grade particles under different rotation frequencies and milling times. These two types of starting materials are prepared to study the effect of the OH bond on synthesis and crystallization. The amorphous samples were characterized by X-ray diffraction and infrared spectroscopy. Amorphous samples with enstatite composition are synthesized from both SiO2–MgO and SiO2–Mg(OH)2 at 300 rpm and for 300 hr. Amorphous samples with forsterite composition are synthesized from both SiO2–MgO and SiO2–Mg(OH)2. The samples from SiO2–Mg(OH)2 require 400 rpm and a long milling time of 1600 hr. After crystallization, amorphous samples with an enstatite composition synthesized from SiO2–Mg(OH)2 mainly transform into forsterite with small amounts of amorphous silica SiO2 and enstatite depending on the rotation frequencies and milling time, while those from SiO2–MgO become enstatite. The amorphous samples with a forsterite composition are crystallized to forsterite from both starting materials. The presence of H2O or OH bonds significantly affects the final products after the crystallization of amorphous silicates of enstatite composition.

¹Zhang, Guozhuo,¹Wang, Xu,¹Wang, Yun,¹Cui, Han,¹Zhao, Weiqian,¹Qiu, Lirong
Measurement: Journal of the International Measurement Confederation 224, 113807 Link to Article [DOI 10.1016/j.measurement.2023.113807]
¹MIIT Key Laboratory of Complex-field Intelligent Exploration, School of Optics and Photonics, Beijing Institute of Technology, Beijing, 100081, China

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¹Kuwahara, Hideharu
Physics of the Earth and Planetary Interiors 346, 107123, Link to Article [DOI10.1016/j.pepi.2023.107123]
¹Geodynamics Research Center, Ehime University, Ehime, Japan

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