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Scientists have used the James Webb Space Telescope to discover daily cloud cycles on a distant “Hot Jupiter” planet
The study was led by researchers from Johns Hopkins University, focused on the exoplanet WASP-94A b, a massive gas giant orbiting extremely close to its parent star.
The findings reveal that clouds made of sand-like minerals form during the planet’s mornings and disappear by evening, creating a constantly changing weather system unlike anything seen before.
A planet with extreme weather
Hot Jupiters are giant gas planets that orbit very close to their stars, exposing them to blistering temperatures and intense radiation. On WASP-94A b, temperatures reach beyond 1,000 degrees Celsius, creating a harsh environment where atmospheric conditions can change rapidly.
Researchers found that WASP-94A b’s mornings are covered in thick clouds made of magnesium silicate, a mineral commonly found in rocks on Earth. But by evening, those clouds have vanished, leaving the skies extremely clear.
Scientists believe this cloud cycle may happen in one of two ways. Powerful winds could be dragging the clouds deep into the planet’s atmosphere, where they become hidden from view, or the intense daytime heat may simply vaporize them as they move across the hotter side of the planet.
The discovery was made possible through the James Webb Space Telescope. As WASP-94A b passed in front of its star, researchers measured different parts of the planet separately rather than averaging the entire atmosphere together.
This technique allowed scientists to examine the planet’s leading edge, which experiences morning conditions, and its trailing edge, which represents evening conditions. By separating the two sides, researchers identified major differences in cloud coverage for the first time.
Previous observations with the Hubble Space Telescope blended the atmosphere and cloud data together, making it difficult to determine the planet’s true composition.
The clearer evening skies also helped researchers better understand the chemical makeup of WASP-94A b. Earlier studies suggested that the planet contained hundreds of times more oxygen and carbon than Jupiter, a puzzling result that did not fit existing theories of planet formation.
Scientists now estimate that the planet contains only about five times as much oxygen and carbon as Jupiter, bringing the findings more in line with current models of planetary evolution.
More of the world’s showing similar patterns
After studying WASP-94A b, researchers examined several other Hot Jupiter planets and found similar cloud cycles on WASP-39 b and WASP-17 b.
The discovery suggests that changing cloud patterns may be common on these extreme worlds. Scientists now plan to use future James Webb observations to study cloud behavior across a wider range of exoplanets, including those in potentially habitable regions.
The findings mark a major step forward in understanding alien atmospheres and could help astronomers better interpret the chemistry, climate, and evolution of planets far beyond Earth.