The hottest planet

    Authors

    J. Harrington; S. Luszcz; S. Seager; D. Deming;L. J. Richardson

    Comments

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    Abbreviated Journal Title

    Nature

    Keywords

    SPITZER-SPACE-TELESCOPE; EXTRASOLAR PLANET; HD 189733B; THERMAL; EMISSION; HOT JUPITERS; ATMOSPHERES; 149026B; SPECTRUM; CORE; Multidisciplinary Sciences

    Abstract

    Of the over 200 known extrasolar planets, just 14 pass in front of and behind their parent stars as seen from Earth. This fortuitous geometry allows direct determination of many planetary properties(1). Previous reports of planetary thermal emission(2-5) give fluxes that are roughly consistent with predictions based on thermal equilibrium with the planets' received radiation, assuming a Bond albedo of similar to 0.3. Here we report direct detection of thermal emission from the smallest known transiting planet, HD149026b, that indicates a brightness temperature ( an expression of flux) of 2,300 +/- 6200K at 8 mm. The planet's predicted temperature for uniform, spherical, blackbody emission and zero albedo ( unprecedented for planets) is 1,741 K. As models with non-zero albedo are cooler, this essentially eliminates uniform blackbody models, and may also require an albedo lower than any measured for a planet, very strong 8 mm emission, strong temporal variability, or a heat source other than stellar radiation. On the other hand, an instantaneous re-emission blackbody model, in which each patch of surface area instantly re-emits all received light, matches the data. This planet is known(6-9) to be enriched in heavy elements, which may give rise to novel atmospheric properties yet to be investigated.

    Journal Title

    Nature

    Volume

    447

    Issue/Number

    7145

    Publication Date

    1-1-2007

    Document Type

    Article

    Language

    English

    First Page

    691

    Last Page

    693

    WOS Identifier

    WOS:000247030700038

    ISSN

    0028-0836

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