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

    Authors

    N. Madhusudhan; J. Harrington; K. B. Stevenson; S. Nymeyer; C. J. Campo; P. J. Wheatley; D. Deming; J. Blecic; R. A. Hardy; N. B. Lust; D. R. Anderson; A. Collier-Cameron; C. B. T. Britt; W. C. Bowman; L. Hebb; C. Hellier; P. F. L. Maxted; D. Pollacco;R. G. West

    Comments

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    Abbreviated Journal Title

    Nature

    Keywords

    GIANT PLANETS; HOT JUPITERS; HD 189733B; TEMPERATURE; EMISSION; PHOTOCHEMISTRY; CHEMISTRY; SPECTRA; DWARFS; STARS; Multidisciplinary Sciences

    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(1); the atmosphere can also differ from those in the Solar System(1,2). The solar C/O is 0.54 (ref. 3). Here we report an analysis of dayside multi-wavelength photometry(4,5) 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(7-9).

    Journal Title

    Nature

    Volume

    469

    Issue/Number

    7328

    Publication Date

    1-1-2011

    Document Type

    Article

    Language

    English

    First Page

    64

    Last Page

    67

    WOS Identifier

    WOS:000285921600031

    ISSN

    0028-0836

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