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

Article

关键词: GIANT PLANETS;    HOT JUPITERS;    HD 189733B;    TEMPERATURE;    EMISSION;    PHOTOCHEMISTRY;    CHEMISTRY;    SPECTRA;    DWARFS;    STARS;   

DOI  :  10.1038/nature09602

来源: SCIE

【 摘 要 】

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).

【 授权许可】

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