JWST detects methane in atmosphere of TOI-199b, a temperate Saturn-sized exoplanet 330 light-years away - first atmospheric read of any non-hot-Jupiter giant
For the first time, astronomers have read the atmosphere of a temperate giant planet. JWST detected methane around TOI-199b, a Saturn-sized world 330 light-years away. Surface near 175F, far cooler than the hot Jupiters that dominate the catalog. Penn State and JPL, in The Astron
For the first time, astronomers have studied the atmosphere of a temperate giant planet beyond our solar system. NASA's James Webb Space Telescope has detected methane around TOI-199b, a Saturn-sized world orbiting a star about 330 light-years from Earth. Most giant exoplanets discovered so far are "hot Jupiters" that hug their stars and reach blistering temperatures of thousands of degrees. TOI-199b is different. With a 100-day orbit, its surface sits near 175F, close to the upper range of Earth's hottest deserts but radically cooler than its hot-Jupiter cousins. That makes it one of only a small number of known temperate giants, and the first whose atmosphere has been characterized in this kind of detail. JWST's measurements identified methane and pointed to possible traces of ammonia and carbon dioxide. The chemistry will help researchers test models of how planetary atmospheres form and evolve far from the extreme heat that dominates most exoplanet observations. The study, led by scientists from Penn State and NASA's Jet Propulsion Laboratory at Caltech, was published May 20 in The Astronomical Journal. It opens a path to studying a planetary class that has been largely beyond reach until now, and sharpens the comparison between giant planets in other systems and the cold gas giants in our own backyard, Jupiter and Saturn.