熱いネプチューンの砂漠の残った惑星の核
David J Armstrong1,2, Théo A Lopez3, Vardan Adibekyan4
1Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK. d.j.armstrong@warwick.ac.uk.
Nature
|July 3, 2020
まとめ
TOI-849bは,海王星より小さい密度の高い系外惑星で,ガスの巨星の残った核である可能性が高い. 惑星の進化の洞察を提示する 大気の大量の損失を示唆しています
科学分野:
- 惑星科学
- エクソプラネット研究
- 天体物理学
背景:
- 巨大な惑星の内部と核は,観測の不確実性があるため,十分に理解されていません.
- 熱いネプチューンの砂漠のような 稀な進化過程を 経験している系外惑星は 惑星の内部を研究するのに役立ちます
- HD149026b,LTT9779b,NGTS-4bのような惑星は 大気の損失と巨大なコアを強調しています
研究 の 目的:
- 半径が小さくて質量が大きい TOI-849b系外惑星の性質を調査する
- 内部構造モデルを使用してTOI-849bの構成と進化史を決定する.
- 巨大惑星の質量減少の原因を 理解する
主な方法:
- 外惑星TOI-849bの観測
- TOI-849bの質量,半径,密度の分析
- 内部構造モデルの適用により,ガス層の質量を制限する.
主要な成果:
- TOI-849bの半径は海王星より小さいが,質量は地球質量7.7倍で,密度は地球に似ている.
- 内部構造モデルは,惑星全体の15%以上を含まない水素とヘリウム包膜を示しています.
- この惑星の特徴は かつてガス巨星だったことを示唆しています
結論:
- TOI-849bは 巨大な惑星の核の残骸です
- 熱的自己破壊,巨大惑星の衝突,または大量ガス蓄積を回避することによって,質量損失が発生した可能性があります.
- 光蒸発は数十億年にわたって小さな水素/ヘリウム封筒を取り除くことができ,TOI-849bの残りの大気は揮発性物質に富んでいる可能性があることを示唆しています.
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