Through high-fidelity spectroscopic analyses conducted with the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument aboard NASA/ESA/CSA’s James Webb Space Telescope, scientists have identified helium gas dissipating from WASP-107b, a gas giant exoplanet classified as a super-Neptune, situated approximately 212 light-years distant within the Virgo constellation.
An artist’s impression of the exoplanet WASP-107b. Image credit: University of Geneva / NCCR PlanetS / Thibaut Roger.
WASP-107 is characterized as a highly active K-type main sequence star, located roughly 212 light-years away in the Virgo constellation.
Initially identified in 2017, WASP-107b stands out as one of the least dense exoplanets discovered, a category that astrophysicists have playfully named ‘super-puff’ or ‘cotton-candy’ planets.
This celestial body traverses its orbit in close proximity to its host star—more than 16 times nearer than Earth is to the Sun—completing a revolution every 5.7 days.
It possesses one of the coolest exoplanetary atmospheres documented, though at approximately 500 degrees Celsius (932 degrees Fahrenheit), it remains considerably hotter than Earth.
The prevailing hypothesis attributes this elevated temperature to tidal heating, a consequence of the planet’s slightly elliptical orbit, which effectively accounts for WASP-107b’s inflated state without necessitating extreme formation scenarios.
“Atmospheric leakage into space is a phenomenon observed in planetary systems,” stated Yann Carteret, an astronomer from the University of Geneva, and his colleagues.
“This is the case for Earth, which experiences a continuous, irreversible loss of roughly 3 kg of matter, predominantly hydrogen, each second.”
“This process, known as atmospheric escape, holds particular significance for astronomers studying exoplanets situated in extreme proximity to their stars, as these are subjected to intense heating and consequently, this very phenomenon.”
Leveraging data acquired from Webb’s NIRISS instrument, the scientific team detected an extensive helium outflow within the exosphere of WASP-107b.
This substantial cloud exhibits the capacity to partially obscure the star’s light even prior to the planet transiting in front of it.
“Our sophisticated atmospheric escape models corroborate the existence of helium flows, both preceding and succeeding the planet, extending in the direction of its orbital trajectory to distances approaching ten times the planet’s radius,” Carteret elaborated.
In addition to helium, the research team successfully confirmed the presence of water vapor and a spectrum of chemical constituents (including carbon monoxide, carbon dioxide, and ammonia) within WASP-107b’s atmosphere.
These findings provide invaluable insights for reconstructing the planet’s formation history and its migratory path.
The researchers propose that the planet originally formed far from its present orbital position, subsequently migrating inward towards its star, which would elucidate its distended atmosphere and associated gas loss.
“On Earth, atmospheric escape is too negligible to profoundly alter our planet,” commented Vincent Bourrier, an astronomer at the University of Geneva.
“However, it is theorized to be the reason for the absence of water on our neighboring planet, Venus.”
“Consequently, a thorough comprehension of the underlying mechanisms governing this phenomenon, which has the potential to strip away the atmospheres of certain rocky exoplanets, is paramount.”
The culmination of this research has been published in the esteemed journal Nature Astronomy.
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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
