恒星間放射性 (60) Feの地球上の堆積によって探査された近年の地球近くの超新星
A Wallner1, J Feige2, N Kinoshita3
1Department of Nuclear Physics, Research School of Physics and Engineering, The Australian National University (ANU), Canberra, Australian Capital Territory 2601, Australia.
Nature
|April 15, 2016
まとめ
地球近くの超新星は稀で 2~4百万年ごとに発生します 深海のアーカイブを分析すると 過去の複数の超新星事件から 星間鉄-60 (60Fe) の証拠が明らかになる.
科学分野:
- 天文学と天体物理学
- 宇宙 線 と 粒子 物理
- 地化学
背景:
- 超新星と巨大な星の風は 鉄-60 (60Fe) のような放射性核を 星間空間に放出します
- 半減期が長いこれらの放射性物質は 星間塵の粒に保存できます
- 太陽系に入ると 過去の恒星活動の記録が得られます
研究 の 目的:
- 深海の地殻で発見された鉄-60 (60Fe) 信号の起源と範囲を調査する.
- 60Feシグナルがグローバルで 時間の延長で 星間起源のものであるか判断する
- 近くの巨大な恒星と超新星の歴史を再構築する
主な方法:
- すべての主要な海洋からの深海沈殿体核の分析60Feの堆積を検出する.
- 60Feの流入の時間軸を確立するために,堆積層の放射線年代測定.
- 60Feの堆積パターンを,既知の超新星発生率と距離と比較する.
主要な成果:
- 深海のアーカイブで確認された 60Fe 信号は地球規模で 星間起源です
- 1.5~320万年前と6.5~8.7百万年前の時間間隔に相当する60Feの大量流入が検出されました.
- この発見は 放出された60Feのわずか"パーセントが 塵に捕らえられ 地球に堆積したことを示唆しています
結論:
- 地球の100パーセック以内では 過去1000万年にわたって 複数の超新星と 巨大な恒星が発生しています
- 60Feの記録は近年のエネルギー的な恒星現象の直接的な証拠を提供します.
- この研究は太陽系周辺の 超新星の発生頻度と 衝撃の理解を深めています
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