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外惑星WASP-12bの大気には,高いC/O比率と弱い熱逆転がある
Nikku Madhusudhan1, Joseph Harrington, Kevin B Stevenson
1Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. nmadhu@mit.edu
Nature
|December 15, 2010
まとめ
ホットジュピターWASP-12bは,炭素と酸素の比率 (C/O) が1以上または1に等しいので,炭化水素に富んだ大気を示している. この系外惑星は,
科学分野:
- 惑星外科学と天体生物学
- 外惑星の大気化学
背景:
- 炭素と酸素の比率 (C/O) は,惑星の形成と大気組成の重要な指標である.
- 0.8を超えるC/O比は,炭化水素が優勢である内部と,太陽系惑星とは異なる,潜在的に異常な大気化学を示唆しています.
- 太陽のC/O比率は0.54である.
研究 の 目的:
- 熱ジュピターWASP-12b.b.を通過する大気の組成を分析するために.
- WASP-12bの大気中の炭素と酸素の比率 (C/O) を決定する.
- WASP-12bの高度に照射された大気の熱構造とエネルギー循環を調査する.
主な方法:
- 外惑星WASP-12bの昼間の多波長フォトメトリーデータの分析.
- 観測された大気組成の比較と太陽光豊富な化学均衡モデル.
主要な成果:
- WASP-12bの大気中のC/O比は,1以上または1に等しいと決定されています.
- WASP-12bの大気は,一酸化炭素 (CO) とメタンに富み,水蒸気で枯渇しており,太陽の豊富なモデルから大きく逸れている.
- 温度が2,500Kを超える大気は,有意な熱逆転 (平流層) を示せず,効率的な昼夜間のエネルギー輸送を示しています.
結論:
- WASP-12bは,高いC/O比率と一致する,炭素に富んだ大気を備えています.
- 大気組成と熱逆転の欠如は,高度に照射された熱木星の大気に対する既存の理論モデルに挑戦しています.
- 効率的な熱循環が観測された大気特性に寄与している可能性が高い.
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