See the clouds streaming and vanishing around this planet - 690 light years away

WASP-94 A b shows a strong day–night cloud cycle. Thick clouds form on the cool night side and dissipate after winds carry them to the hot day side. The pattern was detected by measuring tiny differences in the star’s spectrum at different phases of the planet’s transit across its host star. During each transit, the leading portion of the atmosphere is covered with thick clouds, likely mineral droplets rather than water because the dayside temperature is at least 1,600 kelvin. By the end of the transit, the trailing portion appears clear, consistent with clouds breaking up as they move around the planet.

"The telescope revealed tiny differences in the starlight's spectrum between the start, middle and end of the planet's transit in front of its star. The measurements showed that during each transit, the part of the atmosphere that crosses first in front of the star is covered with thick clouds - probably made of droplets of minerals rather than water, given that the planet's dayside temperature is at least 1,600 kelvin. But by the end of the transit, the trailing part of the atmosphere that crosses last is clear."

"Researchers can usually detect the presence of an extrasolar planet only indirectly - for instance, when the planet passes in front of its star, as viewed from Earth. Starlight filtered through a planet's atmosphere can be analysed for clues about the planet's chemistry, its weather patterns and even its origins. But even large planets block only 1% or so of the star's light, and a much smaller amount of that light filters through the planet's atmosphere."

"On the night side of a distant planet, thick clouds continuously form. But as winds carry them from the cool night side to the lit day side, the clouds quickly dissipate. Astronomers have been able to detect this weather pattern on the planet WASP-94 A b just by studying the light of its star coming from 210 parsecs (690 light years) away."

Read at Nature