English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We report the detection of thermal emission at 4.5 and 8  μ m from the planet WASP‐17b. We used  Spitzer  to measure the system brightness at each wavelength during two occultations of the planet by its host star. By combining the resulting light curves with existing transit light curves and radial‐velocity measurements in a simultaneous analysis, we find the radius of WASP‐17b to be 2.0 R  Jup , which is 0.2 R  Jup  larger than any other known planet and 0.7 R  Jup  larger than predicted by the standard cooling theory of irradiated gas giant planets. We find the retrograde orbit of WASP‐17b to be slightly eccentric, with 0.0012 &lt;  e  &lt; 0.070 (3σ). Such a low eccentricity suggests that, under current models, tidal heating alone could not have bloated the planet to its current size, so the radius of WASP‐17b is currently unexplained. From the measured planet–star flux‐density ratios we infer 4.5 and 8  μ m brightness temperatures of 1881 ± 50 and 1580 ± 150 K, respectively, consistent with a low‐albedo planet that efficiently redistributes heat from its day side to its night side.

Thermal emission at 4.5 and 8 μm of WASP‐17b, an extremely large planet in a slightly eccentric orbit