Title

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

Authors

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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