外惑星GJ 436bの大気中の熱化学的不均衡の可能性
Kevin B Stevenson1, Joseph Harrington, Sarah Nymeyer
1Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, Florida 32816, USA. kevin218@knights.ucf.edu
Nature
|April 24, 2010
まとめ
研究者らは,熱い海王星系外惑星GJ 436bからの熱放射を検出しました. その大気には,驚くほどメタン (CH4) が少なく,一酸化炭素 (CO) が高く,異常な大気化学を示唆しています.
科学分野:
- 外惑星科学とは,外惑星科学のこと.
- 大気物理学 大気物理学
- 赤外線天文学とは,赤外線天文学のことです.
背景:
- GJ436bは"熱い海王星"のような系外惑星です.
- 伝送スペクトロスコピーを用いた以前の研究では,水蒸気を検出できませんでした.
- GJ 436bの大気組成は,弱々しく制限されていた.
研究 の 目的:
- GJ 436bの昼側から惑星の熱放射を検出するために.
- GJ 436b.の大気組成を制限するために.
- GJ 436bの大気中の化学的不均衡を調査するために.
主な方法:
- GJ 436b.の二次日食観測について
- 熱放射を測定するための赤外線光譜法.
- 構成データを解釈するための大気モデリング.
主要な成果:
- GJ 436bの昼側から複数の赤外線波長にわたる熱放射の検出.
- ベストフィットモデルは,高炭素一酸化物 (CO) の豊富さを示しています.
- 大量のメタン (CH4) 欠乏 (予想より少なくとも10^5倍低い) と水蒸気 (H2) O) と二酸化炭素 (CO2) の存在).
結論:
- GJ 436bの大気は化学的不均衡を示しており,水素が多く存在する大気では予測に反してメタンの欠乏がある.
- 垂直混合やメタンのポリメリゼーションのようなプロセスは,観測された低いCH4~CO比率を説明する可能性がある.
- この発見は,熱い海王星の大気に対する標準的な熱化学均衡モデルに異議を唱えている.
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