DE WIT, Julien; WAKEFORD, Hannah; LEWIS, Nikole; DELREZ, Laetitia; GILLON, Michael; SELSIS, Franck; LECONTE, J.; DEMORY, Brice-Olivier; BOLMONT, Emeline; BOURRIER, Vincent; BURGASSER, Adam; GRIMM, Simon; JEHIN, Emmanuel; LEDERER, Susan; OWEN, James; STAMENKOVIĆ, Vlada; TRIAUD, Amaury

doi:10.1038/s41550-017-0374-z

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DE WIT, Julien
Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] [EAPS]

WAKEFORD, Hannah
University of Exeter
Space Telescope Science Institute [STSci]

LEWIS, Nikole
Space Telescope Science Institute [STSci]

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Ce document a été publié dans

Nature Astronomy. 2018-03, vol. 2, n° 3, p. 214 - 219

Nature Publishing Group

Résumé en anglais

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.< Réduire

DOI

http://dx.doi.org/10.1038/s41550-017-0374-z

Projet Européen

Classifying the Range of Exoplanetary Atmospheres using Transmission and Emission Spectroscopy
SPECULOOS: searching for habitable planets amenable for biosignatures detection around the nearest ultra-cool stars

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Unités de recherche

Laboratoire d'Astrophysique de Bordeaux (LAB) - UMR 5804