Astronomers using data from two space telescopes have created the first cloud map of a hot gas giant called Kepler-7b.

Discovered in 2009, Kepler-7b is about half the mass of Jupiter, but is nearly 1.5 times its size.

It orbits its host star, Kepler-7, every 5 days at a distance of approximately 0.06 AU.

Kepler-7b is marked by high clouds in the west and clear skies in the east.

Previous studies have resulted in temperature maps of planets orbiting other stars, but this is the first look at cloud structures on a distant world.

“By observing this planet with Spitzer and Kepler for more than three years, we were able to produce a very low-resolution ‘map’ of this giant, gaseous planet,” explained Dr Brice-Olivier Demory of Massachusetts Institute of Technology, who is a first author of the paper accepted for publication in the Astrophysical Journal Letters (arXiv.org version, full paper in .pdf).

“We wouldn’t expect to see oceans or continents on this type of world, but we detected a clear, reflective signature that we interpreted as clouds.”

Visible-light observations of planet’s moon-like phases led to a rough map that showed a bright spot on its western hemisphere. But these data were not enough on their own to decipher whether the bright spot was coming from clouds or heat.

“Kepler-7b reflects much more light than most giant planets we’ve found, which we attribute to clouds in the upper atmosphere,” said co-author Dr Thomas Barclay of NASA’s Ames Research Center in Moffett Field.

“Unlike those on Earth, the cloud patterns on this planet do not seem to change much over time — it has a remarkably stable climate.”

The study is an early step toward using similar techniques to learn about the atmospheres of exoplanets more like Earth in composition and size.

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Bibliographic information: Brice-Olivier Demory et al. Inference of Inhomogeneous Clouds in an Exoplanet Atmosphere. ApJL, accepted for publication August 20, 2013; arXiv: 1309.7894