2016/05/31 by P. J. Wheatley, Peter J. Wheatley, Tom Louden +6 · 6 citations
Physics and Astronomy · #Astrobiology #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Circumstellar habitable zone #Exoplanet #Galaxy #Luminosity #Physics #Planet #Planetary habitability #Planetary system #Stellar, planetary, and galactic studies #Terrestrial planet #astro-ph.EP
paper · pdf · doi:10.1093/mnrasl/slw192
5 pages, published as a letter in MNRAS (accepted 16 September 2016)
openalex publication_date 2016/10/08 · arxiv created 2016/12/14 · arxiv updated 2016/12/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract We present an XMM–Newton X-ray observation of TRAPPIST-1, which is an ultracool dwarf star recently discovered to host three transiting and temperate Earth-sized planets. We find the star is a relatively strong and variable coronal X-ray source with an X-ray luminosity similar to that of the quiet Sun, despite its much lower bolometric luminosity. We find LX/Lbol = 2–4 × 10−4, with the total XUV emission in the range LXUV/Lbol = 6–9 × 10−4, and XUV irradiation of the planets that is many times stronger than experienced by the present-day Earth. Using a simple energy-limited model, we show that the relatively close-in Earth-sized planets, which span the classical habitable zone of the star, are subjected to sufficient X-ray and EUV irradiation to significantly alter their primary and any secondary atmospheres. Understanding whether this high-energy irradiation makes the planets more or less habitable is a complex question, but our measured fluxes will be an important input to the necessary models of atmospheric evolution.