James Webb Telescope discovers strange ‘superpuff’ planet chasing its own atmosphere through space

A “super-inflated” exoplanet is leaking massive amounts of helium into space and may be losing much of its atmosphere, new observations show.

A large plume of helium gas has been discovered evaporating from a giant planet known as WASP-107b, according to a study based on observations from the James Webb Space Telescope (JWST).

The results, published Monday (December 1) in the journal Nature Astronomy, show that the gas is spread over an area nearly five times the planet’s diameter, and can be seen hurtling far ahead of the planet along WASP-107b’s orbit.

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The study represents the first time that JWST has “captured the escape of helium from Earth,” lead author Vigneshwaran Krishnamurthy, a postdoctoral researcher at McGill University’s Trottier Space Institute in Montreal, said in a statement.

The discovery could help researchers better understand the behavior of exoplanet atmospheres, especially in extreme star systems like WASP-107, where WASP-107b resides, the team said.

planet puffball

WASP-107b was discovered in 2017 near a star about 210 light-years from Earth. (For comparison, our closest planet is about 4 light-years away.) WASP-107b is about the same size as Jupiter, 94% of the gas giant’s diameter, but its mass is only 12% of Jupiter’s. This extremely low density and large size place WASP-107b in the “superpuff” category of exoplanets.

Aside from its unusual density, WASP-107b is in an interesting location. Mercury is seven times closer to a star than the Sun. In contrast, in Earth’s neighborhood, rocky planets are closer to the Sun and gas giants like Jupiter are further away. That means scientists need to come up with a model to explain the difference.

They believe that WASP-107b, like Jupiter and Saturn, formed far away from its star, but something in the system (possibly another planet) forced WASP-107b closer to its star over time.

“WASP-107c, which is much more distant than WASP-107b, may have played a role in this migration,” said study co-author Caroline Piolet Golayeb, an exoplanet researcher and Ph.D. student at the University of Chicago. at the University of Montreal in 2024, it said in a statement.

Once the planet got close enough to its star, the extreme heat of its new orbit began to destroy the exoplanet’s gas atmosphere, the researchers explained. New JWST observations confirmed the extent of the damage. The powerful telescope spotted a helium cloud in the exoplanet’s atmosphere passing in front of the system’s parent star about an hour and a half before WASP-107b itself.

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Researchers have discovered several elements in WASP-107b’s atmosphere that reveal further clues about the planet’s complex history. For example, there is more oxygen in the planet’s atmosphere than would be expected if the planet formed near its star, providing more evidence that the planet’s migration is relatively recent.

JWST also discovered water in the planet’s atmosphere, along with traces of carbon monoxide, carbon dioxide, and ammonia, confirming earlier observations by the Hubble Space Telescope. However, methane, which was predicted to be part of the Earth’s atmosphere due to its chemical properties, was mysteriously absent.

Since JWST’s instruments are sensitive enough to detect methane from a distance, the researchers added, they suggest that other methane-poor gases must have been pumped up from deep in the planet’s atmosphere instead, due to “intense vertical mixing” caused by the star’s heat.

Planets like Earth also experience some atmospheric loss, but it’s not as extreme as this. Studying worlds like WASP-107b could help understand how atmospheric escape works on planets like Venus, which have lost water for many years, the research team said in a statement from the University of Geneva.