日本地球惑星科学連合2019年大会

講演情報

[J] ポスター発表

セッション記号 P (宇宙惑星科学) » P-AE 天文学・太陽系外天体

[P-AE20] 系外惑星

2019年5月26日(日) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:生駒 大洋(東京大学 大学院理学系研究科 地球惑星科学専攻)、成田 憲保(東京大学)

[PAE20-P06] 恒星フレアによる太陽系外惑星ハビタビリティー評価

*山敷 庸亮1前原 裕之2アイラペディアン ウラジミール5野津 湧太3佐藤 達彦4野津 翔太3黒木 龍介1村嶋 慶哉8佐藤 啓明7行方 宏介3佐々木 貴教3スコット トーマス9坂東 日菜3梨元 昴8高木 風香6リング カサンドラ1野上 大作3柴田 一成10 (1.京都大学大学院総合生存学館、2.国立天文台、3.京都大学理学研究科宇宙物理学教室、4.日本原子力研究開発機構、5.NASAゴダード宇宙飛行センター、6.京都大学農学部、7.京都大学工学部、8.京都大学理学部、9.ブリストル大学、10.京都大学天文台)

キーワード:恒星フレア

Environmental factors of crucial importance for exoplanetary habitability include the presence of bodies of liquid surface water, a dense atmosphere, planetary global magnetic field, and internal planetary dynamics . In addition, high-energy radiation due to exoplanetary space weather introduced by magnetic activity of a planet-hosting star can also play a crucial role in the definition of habitability.

Here, we present the first quantitative impact evaluation system of stellar activity on the habitability factors with an emphasis on Stellar Proton Events for several documented exoplanets examining the impact of CO2, H2, N2+O2 –rich atmospheres by introducing starspots of their hoststars, estimated using their rotational periods and lightcurves.

Simulations suggest that the estimated ground level dose for each planet, assuming a terrestrial-level atmospheric thickness, does not exceed the critical dose for complex (multi- cellular) life to persist, even for the planetary surface of Proxima Centauri b, Ross-128b and TRAPPIST-1 e. However when we consider the possible maximum flare for those host stars, at the terrestrial lowest atmospheric depth, the estimated dose reaches fatal levels on TRAPPIST-1 e and Ross-128 b. Continuous XUV radiation higher than that experienced by the Earth induces rapid atmospheric escape for those planetary systems , meaning the atmospheric depth might be substantially less than the Earth. In a scenario where the modelled planetary systems have 1/10 the atmospheric thickness of Earth, the radiation dose at Proxima Centauri b and TRAPPIST-1 e reaches near fatal levels just from relatively minor annually occurring flares from their hoststars.