演題概要

3C-O1-1009

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コンドルールに記録された初生¹⁰Be/⁹Be比から探る原始太陽活動度

(¹阪大・ ²東大・ ³茨城大・ ⁴東大大海研・ ⁵東大地殻化学)
^o福田航平^1,2・ 大西亮¹・ 篠崎裕夢¹・ 比屋根肇²・ 藤谷渉³・ 高畑直人⁴・ 槇納好岐⁵・ 寺田健太郎¹・ 平田岳史⁵

Secondary ion mass spectrometry (SIMS) is a powerful tool for revealing the elemental and isotopic compositions recorded in small (µm to tens of µm) extraterrestrial samples. In the early stage of our Solar System evolution, the presence of the short-lived radionuclide beryllium-10 (¹⁰Be), which decays to ¹⁰B with a half-life of 1.4 million years (Myr), has been inferred from SIMS analyses of the Solar System oldest solids (Ca-Al-rich Inclusions: CAIs). Although the origin of ¹⁰Be in the early Solar System remains controversial, large variations in initial ¹⁰Be/⁹Be ratios in CAIs seem to support its production by the interaction of the Solar System materials and Solar energetic particles (SEPs) originated from the proto-Sun. In this case, the variations in initial ¹⁰Be/⁹Be ratios of the early Solar System solids should correspond to the variations in activities of the proto-Sun, which could influence the evolution of the Solar protoplanetary disk. Here, we improved the accuracy of SIMS Be-B analysis for anorthite (CaAl₂Si₂O₈) and applied it to meteoritic chondrules that formed about 1–4 Myr after CAIs. On the basis of the determined initial ¹⁰Be/⁹Be ratios, we discuss the activity of the proto-Sun at the time of chondrule formation.