Webb Telescope Detects Helium Escape from ‘Super-Puff’ Exoplanet WASP-107b
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A new study reveals a “super-puff” exoplanet, WASP-107b, is losing helium to space, offering crucial insights into planetary atmospheres and evolution.
Astronomers using teh James Webb Space Telescope have detected a meaningful outflow of helium gas from WASP-107b, a unique exoplanet located 212 light-years away in the constellation Virgo. The findings, published December 1, 2025, in Nature Astronomy, shed light on the processes of atmospheric escape and the potential fate of planets orbiting close to their stars.
Unveiling the ‘Cotton-Candy’ Planet
WASP-107b, first discovered in 2017, is classified as a super-neptune – a type of exoplanet larger than Neptune but smaller than Jupiter. What sets it apart is its exceptionally low density, earning it the nicknames “super-puff” or “cotton-candy” planet. This low density has puzzled scientists, but the new observations offer clues to its formation and current state.
The planet orbits its star, WASP-107 – a K-type main sequence star – at an incredibly close distance, completing one orbit every 5.7 days. Despite having one of the coolest atmospheres of any discovered exoplanet, it still reaches temperatures of 500 degrees Celsius (932 degrees Fahrenheit) due to tidal heating caused by its slightly elliptical orbit.
Helium’s Dramatic Escape
Using the near Infrared imager and Slitless Spectrograph (NIRISS) onboard the Webb telescope, the research team detected a vast flow of helium in the exosphere of WASP-107b. this escaping helium forms a cloud that partially obscures the star’s light even before the planet passes in front of it – a phenomenon rarely observed.
“Our atmospheric escape models confirm the presence of helium flows, both ahead and behind the planet, extending in the direction of its orbital motion to nearly ten times the planet’s radius,” explained a lead researcher.This continuous helium absorption provides a unique window into the dynamics of the planet’s atmosphere.
A History Written in the Atmosphere
Beyond helium, the astronomers also confirmed the presence of water and traces of other chemical compounds, including carbon monoxide, carbon dioxide, and ammonia, within WASP-107b’s atmosphere. These atmospheric components serve as valuable clues for reconstructing the planet’s history.
Researchers believe WASP-107b likely formed much farther from its star and subsequently migrated inward.This journey would explain its inflated atmosphere and the ongoing loss of gas. The planet’s current state offers a glimpse into the potential evolution of other exoplanets.
Implications for Planetary Habitability
The study of atmospheric escape is crucial for understanding the long-term habitability of exoplanets. While atmospheric escape on Earth is relatively weak, losing just over 3 kg of matter (primarily hydrogen) per second, it played a significant role in the evolution of planets in our solar system.
“On Earth, atmospheric escape is too weak to drastically influence our planet,” stated a University of geneva astronomer. “But it would be responsible for the absence of water on our close neighbor, Venus.” Understanding these mechanisms is essential for assessing the potential for life on rocky exoplanets, as atmospheric erosion could strip away the conditions necessary for liquid water to exist.
The findings from WASP-107b underscore the power of the James Webb Space Telescope in unraveling the mysteries of exoplanetary atmospheres and the complex processes that shape planetary evolution.
V. Krishnamurthy et al. Continuous helium absorption from both the leading and trailing tails of WASP-107b. Nat Astron, published online December 1, 2025; doi: 10.1038/s41550-025-02710-8
