Title

The Hottest Planet

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. Previous reports of planetary thermal emission give fluxes that are roughly consistent with predictions based on thermal equilibrium with the planets' received radiation, assuming a Bond albedo of ∼0.3. Here we report direct detection of thermal emission from the smallest known transiting planet, HD 149026b, that indicates a brightness temperature (an expression of flux) of 2,300 ± 200 K at 8 μm. 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 μm 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 to be enriched in heavy elements, which may give rise to novel atmospheric properties yet to be investigated. ©2007 Nature Publishing Group.

Publication Date

6-7-2007

Publication Title

Nature

Volume

447

Issue

7145

Number of Pages

691-693

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1038/nature05863

Socpus ID

34249978458 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/34249978458

This document is currently not available here.

Share

COinS