The presence of methane in the atmosphere of an extrasolar planet
Top Cited Papers
- 1 March 2008
- journal article
- letter
- Published by Springer Science and Business Media LLC in Nature
- Vol. 452 (7185), 329-331
- https://doi.org/10.1038/nature06823
Abstract
Molecules present in the atmospheres of extrasolar planets are expected to influence strongly the balance of atmospheric radiation, to trace dynamical and chemical processes, and to indicate the presence of disequilibrium effects. As molecules have the potential to reveal atmospheric conditions and chemistry, searching for them is a high priority. The rotational–vibrational transition bands of water, carbon monoxide and methane are anticipated to be the primary sources of non-continuum opacity in hot-Jupiter planets1,2,3. As these bands can overlap in wavelength, and the corresponding signatures from them are weak, decisive identification requires precision infrared spectroscopy. Here we report a near-infrared transmission spectrum of the planet HD 189733b that shows the presence of methane. Additionally, a resolved water vapour band at 1.9 μm confirms the recent claim4 of water in this object. On thermochemical grounds, carbon monoxide is expected to be abundant in the upper atmosphere of hot-Jupiter planets, but is not identifiable here; therefore the detection of methane rather than carbon monoxide in such a hot planet5,6 could signal the presence of a horizontal chemical gradient away from the permanent dayside, or it may imply an ill-understood photochemical mechanism that leads to an enhancement of methane.Keywords
This publication has 22 references indexed in Scilit:
- The Mid‐Infrared Spectrum of the Transiting Exoplanet HD 209458bThe Astrophysical Journal, 2008
- Analysis of Spitzer Spectra of Irradiated Planets: Evidence for Water Vapor?The Astrophysical Journal, 2007
- Water vapour in the atmosphere of a transiting extrasolar planetNature, 2007
- A map of the day–night contrast of the extrasolar planet HD 189733bNature, 2007
- A Spitzer Spectrum of the Exoplanet HD 189733bThe Astrophysical Journal, 2007
- A spectrum of an extrasolar planetNature, 2007
- The Influence of Atmospheric Dynamics on the Infrared Spectra and Light Curves of Hot JupitersThe Astrophysical Journal, 2006
- Dynamics and Disequilibrium Carbon Chemistry in Hot Jupiter Atmospheres, with Application to HD 209458bThe Astrophysical Journal, 2006
- A theoretical look at the direct detection of giant planets outside the Solar SystemNature, 2005
- Theoretical Transmission Spectra during Extrasolar Giant Planet TransitsThe Astrophysical Journal, 2000