Title

The hottest planet

Authors

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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