Astronomers using the James Webb Space Telescope have captured an extraordinary sight: a massive helium cloud streaming away from the super-puff exoplanet WASP-107b, offering the most direct evidence yet of a planet actively losing its atmosphere. The discovery marks the first time Webb has observed atmospheric escape in real time, revealing a process that could transform how scientists understand the evolution of planets around other stars.
The helium stream, detected through Webb’s NIRISS infrared spectrograph, extends to nearly ten times the radius of WASP-107b. Researchers observed a subtle dimming in the host star’s light almost 90 minutes before the planet began its transit, indicating that the exosphere — the outermost layer of the drifting atmosphere — stretches far ahead of the planet in its orbit. Scientists say the helium signal captured by Webb confirms the first direct observation of an exoplanet shedding its gases into space.
WASP-107b is known as a “super-puff” planet because of its remarkably low density. Though nearly the size of Jupiter at 94 percent of its diameter, the planet has only about 12 percent of Jupiter’s mass. Its structure is extremely diffuse, making it vulnerable to heat and radiation from its nearby star. Orbiting roughly seven times closer to its star than Mercury orbits the Sun, WASP-107b is blasted by extreme stellar energy that strips gases from its upper atmosphere.
The newly detected helium cloud suggests that WASP-107b may be losing material at a much faster rate than previously thought. Researchers believe the planet’s light, puffy envelope of gas is expanding outward and being blown away by stellar radiation and winds, creating an extended tail-like structure that both trails and precedes the planet.
The findings open a new chapter in exoplanet research, showcasing Webb’s unmatched sensitivity to atmospheric signatures and offering a rare look at a world in the process of transformation.
