Detection of the Atmosphere of the 1.6 M{sub ⊕} Exoplanet GJ 1132 b
- Astrophysics Group, Keele University, Staffordshire, ST5 5BG (United Kingdom)
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)
- Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
- Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden)
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{sub ⊕} 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{sub ⊕} for the planet, averaged over all the passbands, and a radius of 0.255 ± 0.023 R{sub ⊙} 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{sub ⊕} 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 H{sub 2}O and/or CH{sub 4} or a hitherto-unconsidered opacity. A surface radius of 1.375 ± 0.16 R{sub ⊕} 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 H{sub 2}O-rich water world.
- OSTI ID:
- 22863099
- Journal Information:
- The Astronomical Journal (Online), Vol. 153, Issue 4; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
Similar Records
ARES. V. No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b
THE LEECH EXOPLANET IMAGING SURVEY: CHARACTERIZATION OF THE COLDEST DIRECTLY IMAGED EXOPLANET, GJ 504 b, AND EVIDENCE FOR SUPERSTELLAR METALLICITY