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Article Dans Une Revue Nature Astronomy Année : 2018

Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1

Laetitia Delrez
Brice-Olivier Demory
Simon Grimm
Susan Lederer
James Owen
  • Fonction : Auteur

Résumé

Seven temperate Earth-sized exoplanets readily amenable for atmospheric studies transit the nearby ultracool dwarf star TRAPPIST-1. Their atmospheric regime is unknown and could range from extended primordial hydrogen-dominated to depleted atmospheres. Hydrogen in particular is a powerful greenhouse gas that may prevent the habitability of inner planets while enabling the habitability of outer ones. An atmosphere largely dominated by hydrogen, if cloud-free, should yield prominent spectroscopic signatures in the near-infrared detectable during transits. Observations of the innermost planets have ruled out such signatures. However, the outermost planets are more likely to have sustained such a Neptune-like atmosphere. Here, we report observations for the four planets within or near the system’s habitable zone, the circumstellar region where liquid water could exist on a planetary surface. These planets do not exhibit prominent spectroscopic signatures at near-infrared wavelengths either, which rules out cloud-free hydrogen-dominated atmospheres for TRAPPIST-1 d, e and f, with significance of 8σ, 6σ and 4σ, respectively. Such an atmosphere is instead not excluded for planet g. As high-altitude clouds and hazes are not expected in hydrogen-dominated atmospheres around planets with such insolation, these observations further support their terrestrial and potentially habitable nature.

Dates et versions

hal-01729026 , version 1 (12-03-2018)

Identifiants

Citer

Julien de Wit, Hannah Wakeford, Nikole Lewis, Laetitia Delrez, Michael Gillon, et al.. Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1. Nature Astronomy, 2018, 2 (3), pp.214 - 219. ⟨10.1038/s41550-017-0374-z⟩. ⟨hal-01729026⟩
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