Ross seminar room (also via Zoom)
Title: An Extended Habitable Zone around Red Dwarfs
Abstract: As M-stars (or Red Dwarfs, RDs) are by far the most abundant stellar type and it is relatively easier to detect small planets with a potential for surface liquid water around them, RDs have been the target of several major surveys in the past decade, including the Kepler and TESS missions and the CARMENES and the MUSCLES projects. We apply the semi-analytical climate model for locked RD-planes (Wandel 2018) to suggest that the Habitable Zone of RDs is significantly wider than previously thought. This result has major implications on detecting bio-signatures, as the relatively small masses and radii of RDs render their transiting planets much easier to detect. Moreover, these properties make it feasible to spectroscopically characterize the atmospheres of RD-planets. It has been pointed out that atmospheric and water erosion by the RD energetic early evolutionary stages may render their planets inhabitable (Leconte et al., 2015; Lingam and Loeb, 2017). However, this may be compensated by thick early atmospheres or later regeneration of an atmosphere and surface water (e.g. Wandel and Gale, 2020, and references therein). The recent discovery of water vapor in the atmosphere of K2-18b (Tsiaras et al. 2019), a potentially habitable planet of a small RD, demonstrated that at least in some cases an atmosphere and even water can survive, supporting the extended RD/HZ-model.
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