English: This artist’s concept shows what the hot gas-giant exoplanet WASP-43 b could look like. WASP-43 b is a Jupiter-sized planet circling a star roughly 280 light-years away, in the constellation Sextans. The planet orbits at a distance of about 1.3 million miles (0.014 astronomical units, or AU), completing one circuit in about 19.5 hours. Because it is so close to its star, WASP-43 b is probably tidally locked: its rotation rate and orbital period are the same, such that one side faces the star at all times.

Temperature measurements based on the amount of 5- to 12-micron mid-infrared light emitted by the planet show that the nightside is probably covered in thick, high clouds. Spectroscopy measurements indicate the presence of water vapor on both the dayside and nightside. But because it is too hot for liquid water to exist, the clouds are probably made of tiny mineral grains instead of water droplets. A surprising lack of methane on the nightside suggests that strong eastward winds are mixing atmospheric gases around the planet. This illustration is based on new data gathered by Webb’s Mid-Infrared Instrument (MIRI) as well as previous observations from other ground- and space-based telescopes, including Hubble and Spitzer. Webb has not captured any images of the planet.

NASA, ESA, CSA, Ralf Crawford (STScI)