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- Title
A high C/O ratio and weak thermal inversion in the atmosphere of exoplanet WASP-12b.
- Authors
Madhusudhan, Nikku; Harrington, Joseph; Stevenson, Kevin B.; Nymeyer, Sarah; Campo, Christopher J.; Wheatley, Peter J.; Deming, Drake; Blecic, Jasmina; Hardy, Ryan A.; Lust, Nate B.; Anderson, David R.; Collier-Cameron, Andrew; Britt, Christopher B. T.; Bowman, William C.; Hebb, Leslie; Hellier, Coel; Maxted, Pierre F. L.; Pollacco, Don; West, Richard G.
- Abstract
The carbon-to-oxygen ratio (C/O) in a planet provides critical information about its primordial origins and subsequent evolution. A primordial C/O greater than 0.8 causes a carbide-dominated interior, as opposed to the silicate-dominated composition found on Earth; the atmosphere can also differ from those in the Solar System. The solar C/O is 0.54 (ref. 3). Here we report an analysis of dayside multi-wavelength photometry of the transiting hot-Jupiter WASP-12b (ref. 6) that reveals C/O???1 in its atmosphere. The atmosphere is abundant in CO. It is depleted in water vapour and enhanced in methane, each by more than two orders of magnitude compared to a solar-abundance chemical-equilibrium model at the expected temperatures. We also find that the extremely irradiated atmosphere (T?>?2,500?K) of WASP-12b lacks a prominent thermal inversion (or stratosphere) and has very efficient day-night energy circulation. The absence of a strong thermal inversion is in stark contrast to theoretical predictions for the most highly irradiated hot-Jupiter atmospheres.
- Subjects
CARBON; OXYGEN; ATMOSPHERE; PLANETARY systems; METHANE; PHOTOMETRY; INVERSION (Geophysics)
- Publication
Nature, 2011, Vol 469, Issue 7328, p64
- ISSN
0028-0836
- Publication type
Article
- DOI
10.1038/nature09602