冷たい茶色矮星からのメタン排出量
Jacqueline K Faherty1,2, Ben Burningham3, Jonathan Gagné4,5
1Department of Astrophysics, American Museum of Natural History, New York, NY, USA. jfaherty@amnh.org.
Nature
|April 17, 2024
まとめ
天文学者は,孤立した茶色矮星CWISEP J193518.59-154620.3 (W1935) から強いメタン放射を検出しました. これは,オーロラのプロセスがそのようなオブジェクトで大気温の逆転を引き起こす可能性があることを示唆しています.
科学分野:
- 外惑星科学
- 大気物理学
- ブラウン・ダワーフの研究
背景:
- 紫外線は太陽系の大惑星で観測され H3+やメタンのような 赤外線信号があります
- ラジオオーロラシグネチャーを持つ 孤立したブラウン・ダワーズの 赤外線オーロラを先行した探査は ゼロの結果でした
- CWISEP J193518.59-154620.3 (W1935) は,温度約482Kの孤立した茶色矮星である.
研究 の 目的:
- 孤立した茶色矮星W1935の赤外線放射特性を調査する.
- W1935で観測された現象を駆動する 大気条件と潜在的エネルギー源を決定する
主な方法:
- W1935の赤外線観測のためにジェームズ・ウェブ宇宙望遠鏡 (JWST) を利用した.
- 観測されたスペクトルの特徴,特にメタンの排出を解釈するために大気モデリングを実施しました.
- 観測データとモデルを比較して,大気温プロファイルと組成を理解する.
主要な成果:
- W1935からJWSTを用いて3,326μmで強いメタン放射を検出した.
- 大気モデリングは,1-10 mbarを中心に約300 Kの有意な温度逆転を明らかにした.
- このモデルでは太陽系の大気惑星とは異なり,H3+の排出を排除した.
結論:
- W1935の大気中の観測された温度逆転は,孤立した茶色矮星にとって異常であり,非標準的な加熱メカニズムを示唆しています.
- オーロラ現象は 大気温暖化と温度逆転の 合理的な説明です
- H3+の放出がないことは,W1935の観測された放出層に関連するより高い圧力での急速な破壊と一致しています.
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