銀河のハローの中の非常に原始的な星です
Elisabetta Caffau1, Piercarlo Bonifacio, Patrick François
1Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117 Heidelberg, Germany. Elisabetta.Caffau@obspm.fr
Nature
|September 3, 2011
まとめ
この研究では,低質量恒星は,ごく初期の宇宙でも,金属度が非常に低い状態で形成される可能性があることがわかりました. これは以前の理論に異議を唱え,これらの恒星が高温を経験し,リチウムの枯渇につながったことを示唆しています.
科学分野:
- 天文学と天体物理学について
- 宇宙化学の進化について
- 星の形成 星の形成 星の形成
背景:
- 初期の宇宙の構成は主に水素とヘリウムで,より重い元素は後に星で合成されました.
- 金属性 (Z) は,ヘリウムよりも重い元素の質量分数であり,恒星の進化を理解するために重要である.
- 以前の理論は,低質量恒星形成のための重要な金属性の値を示唆していたが,議論されている.
研究 の 目的:
- 極めて金属度が低い環境で低質量恒星の形成を調査する.
- 初期の宇宙における恒星形成に関する既存の理論的制約に挑戦する.
- 非常に金属が少ない恒星の化学組成とリチウム枯渇を分析するために.
主な方法:
- 銀河のハローの恒星の化学組成の分析.
- 星の金属性 (Z) と特定の元素 (炭素,窒素,酸素) の豊富さを測定する.
- 熱の歴史を推論するためにリチウムの豊富さの評価.
主要な成果:
- 金属度が非常に低い星 (Z ≤6.9 × 10−7) が特定されました.
- 恒星は,炭素,窒素,酸素の濃縮が欠け,非常に金属が少ない恒星に典型的な化学パターンを表していた.
- リチウムは検出されず,高温でリチウムの枯渇と一致しています.
結論:
- 低質量恒星は,以前に示唆された臨界値以下の金属度で形成される可能性があります.
- この発見は,初期の恒星形成と化学的濃縮に関する既存のモデルに異議を唱えている.
- 観測されたリチウムの枯渇は,恒星の物質が200万ケルビンを超える温度を経験したことを示しています.
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