Detection of the Atmosphere of the 1.6 M<inf>⊕</inf> Exoplanet GJ 1132 b
Publication Date
2017-04-01Journal Title
Astronomical Journal
ISSN
0004-6256
Publisher
American Astronomical Society
Volume
153
Issue
4
Type
Article
Metadata
Show full item recordCitation
Southworth, J., Mancini, L., Nikku, M., Mollière, P., Ciceri, S., & Henning, T. (2017). Detection of the Atmosphere of the 1.6 M<inf>⊕</inf> Exoplanet GJ 1132 b. Astronomical Journal, 153 (4) https://doi.org/10.3847/1538-3881/aa6477
Abstract
© 2017. The American Astronomical Society. All rights reserved. Detecting the atmospheres of low-mass, low-temperature exoplanets is a high-priority goal on the path to ultimately detecting biosignatures in the atmospheres of habitable exoplanets. High-precision HST observations of several super-Earths with equilibrium temperatures below 1000 K have to date all resulted in featureless transmission spectra, which have been suggested to be due to high-altitude clouds. We report the detection of an atmospheric feature in the atmosphere of a 1.6 M⊕ transiting exoplanet, GJ 1132 b, with an equilibrium temperature of ∼600 K and orbiting a nearby M dwarf. We present observations of nine transits of the planet obtained simultaneously in the griz and JHK passbands. We find an average radius of 1.43 ±0.16 R⊕ for the planet, averaged over all the passbands, and a radius of 0.255 ±0.023 R⊙for the star, both of which are significantly greater than previously found. The planet radius can be decomposed into a "surface radius" at ∼1.375 R⊕ overlaid by atmospheric features that increase the observed radius in the z and K bands. The z-band radius is 4σ higher than the continuum, suggesting a strong detection of an atmosphere. We deploy a suite of tests to verify the reliability of the transmission spectrum, which are greatly helped by the existence of repeat observations. The large z-band transit depth indicates strong opacity from H2O and/or CH4 or a hitherto-unconsidered opacity. A surface radius of 1.375 ±0.16 R⊕ allows for a wide range of interior compositions ranging from a nearly Earth-like rocky interior, with ∼70% silicate and ∼30% Fe, to a substantially H2O-rich water world.
Sponsorship
Science and Technology Facilities Council (ST/N000927/1)
Embargo Lift Date
2100-01-01
Identifiers
External DOI: https://doi.org/10.3847/1538-3881/aa6477
This record's URL: https://www.repository.cam.ac.uk/handle/1810/279564
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