彗星物質のエピソード的形成は,若い太陽のような星の爆発で起こります
P Abrahám1, A Juhász, C P Dullemond
1Konkoly Observatory of the Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary. abraham@konkoly.hu
Nature
|May 16, 2009
まとめ
若い恒星系における結晶塵は,恒星爆発中の熱解熱によって形成されるが,ショックによる加熱によって形成されない. この発見は,初期の太陽系を明確にします.
科学分野:
- 惑星科学は惑星科学である.
- 天体物理学 天体物理学
- 宇宙化学 (コスモケミストリー)
背景:
- 太陽系は星間ガスと塵から形成され,当初は無形なシリケートと炭酸粒子だった.
- 彗星の物質は,原太陽星雲の進化の間に,無形シリケートの結晶形への重要な変容を示しています.
- このシリケート変換のタイミングとメカニズム (太陽熱対衝撃熱) は,依然として議論されている.
研究 の 目的:
- 原惑星円盤における結晶シリケートの形成過程を調査する.
- 塵の処理における恒星の活動,特に爆発の役割を決定する.
- シリケート結晶化のメカニズムとして,太陽熱とショック熱を区別する.
主な方法:
- 若い太陽のような星EX Lupiの静止状態と爆発段階における中赤外線スペクトルの特徴の観測.
- 粉塵粒子の存在と組成を特定するためのスペクトルデータの分析.
- 観測された特徴を,異なる加熱シナリオの下での塵処理の理論モデルと比較.
主要な成果:
- 結晶型フォースタライトに起因する新型の中赤外線スペクトル特徴は,EX Lupiの爆発中に検出されたが,静止期には検出されなかった.
- 観測された結晶型フォースタライトは,熱冷却による形成を示しています.
- 観測されたスペクトルに冷たい結晶がないため,より大きな円盤半径での衝撃加熱は排除されます.
結論:
- 恒星爆発は,円盤の内側の表面層で無形シリケートを結晶形に熱くするために十分な熱エネルギーを供給します.
- アウトバースト中の熱冷却は,結晶の塵を生成するためのこれまで考慮されていないが重要なメカニズムです.
- 衝撃加熱は,太陽系初期に広範囲にシリケート結晶化の主要なメカニズムである可能性は低い.
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