By utilizing highly precise spectroscopic observations from the Near Infrared Imager and Slitless Spectrometer (NIRISS) on board the NASA/ESA/CSA James Webb Space Telescope, astronomers have identified helium gas escaping from WASP-107b, a super-Neptunian exoplanet located in the Virgo constellation, approximately 212 light-years away.
Artist’s impression of exoplanet WASP-107b. Image credit: University of Geneva / NCCR PlanetS / Thibaut Roger.
WASP-107 is an active K-type main-sequence star situated roughly 212 light-years away in the Virgo constellation.
Discovered in 2017, WASP-107b is among the least dense known exoplanets, categorized by astrophysicists as a “superpuff” or “cotton candy” planet.
This exoplanet has an orbit significantly closer to its star than Earth is to the Sun, completing its orbit every 5.7 days.
While this planet features the coldest atmosphere recorded for an exoplanet, at 500 degrees Celsius (932 degrees Fahrenheit), it remains much hotter than Earth.
This elevated temperature results from tidal heating linked to its slightly elliptical orbit, which may help explain how WASP-107b can expand without invoking extreme formation theories.
“A planet’s atmosphere can sometimes dissipate into space,” explained Yann Carteret, an astronomer at the University of Geneva, alongside colleagues.
“On Earth, we lose just over 3 kg of matter (primarily hydrogen) every second.”
“This phenomenon, known as atmospheric escape, is especially significant for astronomers studying exoplanets in close proximity to their stars. Such planets experience intense heating, making them particularly vulnerable to this effect.”
With data from Webb’s NIRISS instrument, astronomers observed a substantial flow of helium within WASP-107b’s exosphere.
This helium cloud partially obscures the star’s light even before the planet transits in front of the star.
“Our atmospheric escape model indicates a helium flow both in front of and behind the planet, extending nearly 10 times the planet’s radius in the direction of its orbit,” Carteret stated.
Alongside helium, astronomers confirmed the existence of water and various trace chemicals (including carbon monoxide, carbon dioxide, and ammonia) in WASP-107b’s atmosphere.
These findings provide essential insights for piecing together the history of their formation and migration.
The research suggests that the planet initially formed at a greater distance from its current orbit before drifting closer to its star, which may account for the thickening of its atmosphere and gas loss.
“Atmospheric escape on Earth is too weak to have a significant impact on our planet,” noted Vincent Boullier, an astronomer at the University of Geneva.
“However, it could explain the absence of water on Venus, which is nearby.”
“Thus, understanding the mechanisms involved in this process is crucial, as it could erode the atmospheres of certain rocky exoplanets.”
Details of these findings were published in the journal Nature Astronomy.
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V. Krishnamurthy et al. Continuum helium absorption from both the leading and trailing atmospheric tails of WASP-107b. Nat Astron, published online on December 1, 2025. doi: 10.1038/s41550-025-02710-8
Source: www.sci.news
