James Webb Space Telescope Spots an Exoplanet Losing Its Atmosphere in a Huge Helium Stream

Astronomers have observed a giant helium cloud streaming outward from a distant "super-puff" exoplanet, marking the first time NASA's James Webb Space Telescope has captured such atmospheric escape. WASP-107b, a low-density gas giant about 210 light-years away, appears to be losing its outer layers under intense stellar radiation. The escaping helium forms a vast exosphere nearly ten times the planet's radius, trailing and even leading the planet in its orbit.

Helium Cloud Streams from WASP-107b

According to a recent paper, using​‍​‌‍​‍‌​‍​‌‍​‍‌ JWST, a team led by McGill has found a massive helium cloud that is leaking from WASP-107b. The cloud of gas is an exosphere that extends to almost ten times the radius of the planet and is going ahead of the planet in its orbit.

Webb's NIRISS infrared spectrograph found the helium signature, which is a slight dimming of the star's light that happened about 1.5 hours before the transit of WASP-107b. The researchers say that this is the very first time that the atmospheric escape of an exoplanet has been witnessed in the most direct ​‍​‌‍​‍‌​‍​‌‍​‍‌way.

The Super-Puff Planet WASP-107b

WASP-107b is Jupiter-sized (94% of Jupiter's diameter) but only about 12 percent as massive, giving it an extremely low density. This “super-puff” world orbits very close to its star — about seven times closer than Mercury is to the Sun — exposing it to intense heating.

Webb also detected water vapour high in the atmosphere (but no methane), supporting models that WASP-107b formed farther out and then migrated inward, where stellar heat is stripping away its gases.