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The exoplanet, WASP-94A b, is nearly 700 light-years away in the Microscopium constellation. The clouds were made of magnesium silicate, which is a mineral that is found in rocks on Earth.

WASP-94A b belongs to a class of planets called Hot Jupiters, which are massive gas giants that orbit very close to their stars – closer than Mercury orbits the Sun. Their extreme heat and radiation make them natural laboratories for studying atmospheric chemistry and cloud behaviour under severe conditions.

Scientists studied the planet as it transited across its parent star. JWST allowed a look into the planet’s leading morning-side, where cooler air of the night-side flows towards the hot dayside, and the trailing evening side, where air moves back into darkness

What they found was this: the morning side was filled with magnesium silicate clouds, while there were nearly no clouds in the evening side.

“JWST lets us localise our observations, which helped us see the cloud cycle,” said the study’s lead author, Sagnick Mukherjee. The earlier Hubble telescope gave such data “squished together and indistinguishable.”

The findings of the study were published in the Science journal. It was led by postdoctoral fellow Sagnick Mukherjee, Arizona State University,

The researchers believe this is what happens – intense winds were dragging the morning clouds to the day-side atmosphere, where at temperatures above 1000 degrees Celsius, they vaporised

For a long time, astronomers have suspected these Hot Jupiters have complex weather. From the evening-side, researchers could measure the amount of oxygen and carbon on the planet, which showed it had a composition close to Jupiter

After studying WASP-94A b, the team examined eight more hot gas giants and found parallel cloud cycles on two more – WASP-39 b and WASP-17 b. The researchers are now planning a larger JWST cloud cycles tracking survey across many exoplanets.