Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

P (Space and Planetary Sciences ) » P-AE Astronomy & Extrasolar Bodies

[P-AE20] Exoplanet

Sun. May 26, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Masahiro Ikoma(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Norio Narita(University of Tokyo)

[PAE20-P06] Impact of Stellar Superflares on Planetary Habitability

*Yosuke Alexandre Yamashiki1, Hiroyuki Maehara2, Vladimir Airapetian5, Yuta Notsu3, Tatsuhiko Sato4, Shota Notsu3, Ryusuke Kuroki1, keiya murashima8, Hiroaki Sato7, Kosuke Namekata3, Takanori Sasaki3, Thomas Scott9, Hina Bando3, Subaru Nashimoto8, Fuka Takagi6, Cassandra Ling1, Daisaku Nogami3, Kazunari Shibata10 (1.Earth & Planetary Water Resources Assessment Laboratory Graduate School of Advanced Integrated Studies in Human Survivability Kyoto University, 2.National Astronomical Observatory of Japan, 3.Department of Astronomy, Kyoto University, 4.Japan Atomic Energy Agency, 5.NASA / GSFC, 6.Faculty of Agriculture, Kyoto University, 7.Faculty of Engineering, Kyoto University, 8.Faculty of Science, Kyoto University, 9.Interface Analysis Centre, University of Bristol, 10.Astronomical Observatory, Kyoto University)

Keywords:Stellar flare

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.