Atmosphere lost by planet captured by James Webb

Fahad Redha

January 21, 2026
3 min read

Atmosphere lost by planet captured by James Webb

For the first time ever, the James Webb Space Telescope has captured a planet losing its atmosphere. Astronomers from University of Geneva (UNIGE), the National Centre of Competence in Research PlanetS, and the Trottier Institute for Research on Exoplanets (IREx) at the University of Montreal (UdeM) followed gas escaping from an exoplanet continuously during a full orbit around a star.

The observations showed the gas giant WASP-121b is surrounded by two large streams of helium stretching over half of its orbit. Combined with computer models, this shows the most detailed look at a planet’s atmosphere escaping. The team published the findings in Nature Communications.

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WASP-121b is classified as a hot Jupiter, a gas giant that orbits very close to a star. It completes a full orbit in just 30 hours. Because it is so close to the star, it is subject to intense radiation, heating its atmosphere to thousands of degrees, where lightweight elements including hydrogen and helium can break free and drift off into space. Over millions of years, the loss of its atmospheric material can fundamentally alter its size, composition, and planetary evolution.

Until this discovery, researchers could only study atmospheric loss in a planet during a short planetary transit, a brief moment when it passes in front of a star from our perspective. These last only a few hours and provide little information. Scientists need to continually monitor if they hope to determine how far the escaping gas travels and how the planet’s structure is affected over time.

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