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A high C/O ratio and weak thermal inversion in the atmosphere of exoplanet WASP-12b

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Madhusudhan, Nikku, Harrington, Joseph, Stevenson, Kevin B., Nymeyer, Sarah, Campo, Christopher J., Wheatley, P. 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 and West, Richard G.. (2011) A high C/O ratio and weak thermal inversion in the atmosphere of exoplanet WASP-12b. Nature, Vol.469 (No.7328). pp. 64-67. ISSN 0028-0836

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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. Here we report an analysis of dayside multi-wavelength photometry of the transiting hot Jupiter WASP-12b 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.

Item Type: Journal Article
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Faculty of Science > Physics
Library of Congress Subject Headings (LCSH): Planets -- Atmospheres , Extrasolar planets, Atmospheric thermodynamics
Journal or Publication Title: Nature
Publisher: Nature Publishing Group
ISSN: 0028-0836
Official Date: 6 January 2011
Volume: Vol.469
Number: No.7328
Number of Pages: 4
Page Range: pp. 64-67
Identification Number: 10.1038/nature09602
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Restricted or Subscription Access
Funder: United States. National Aeronautics and Space Administration (NASA), Jet Propulsion Laboratory (U.S.) (JPL)
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URI: http://wrap.warwick.ac.uk/id/eprint/4578

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