アレンデ隕石のバリウムイソトープ:絶滅した超重元素に対する証拠
まとめ
アレンデ隕石には,異例の同位体比を持つクセノンが含まれており,炭素性コンドライト分裂 (CCF) のクセノンとして知られています. このクセノンとその炭素媒体は,超重元素の分裂によるものではなく,恒星の核合成による古代の遺物である可能性が高い.
科学分野:
- 宇宙化学 (コスモケミストリー)
- 核天体物理学 核天体物理学とは
- 隕石学は,隕石についてです.
背景:
- 炭酸性コンドライトであるアレンデ隕石には,プレソラー粒子が含まれています.
- 同位体異常のクセノンは,炭酸性コンドライト分裂 (CCF) クセノンと呼ばれ,隕石のサンプルで検出されています.
- CCFクセノンの起源は議論されており,絶滅した超重元素のin situ分裂やプレソラー起源を含む仮説があります.
研究 の 目的:
- アレンデ隕石で発見された異位体異常のクセノン-131からクセノン-136 (CCFクセノン) の起源を調査する.
- CCFクセノンが,絶滅した超重元素の in situ 核分裂から生じたという仮説を検証するために.
- CCFのクセノンとそのキャリアがプレソラー遺物であるかどうかを判断する.
主な方法:
- アレンデ隕石からの炭素とクロミット分子の分析.
- クセノン (Xe-131からXe-136) の同位体の濃度の測定.
- 同じ分数でバリウム (Ba-130からBa-138) の同位体濃度の測定.
主要な成果:
- CCFクセノン (最大5×10^11原子/g) を含んだ分子は,バリウム-130からバリウム-138で検出可能な同位体異常を示さなかった.
- バリウム異常の欠如は,CCFクセノンの源として超重元素のin situ分裂を排除する.
結論:
- CCFのクセノンとその炭酸性のキャリアは,おそらく恒星の核合成から生じた,プレソラー遺物である.
- この発見は,CCFのクセノンの解釈を,太陽系の形成前に起こったプロセスの証拠として支持しています.
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