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IT Home reported on October 18 that astronomers have used data from the James Webb Space Telescope (JWST) to uncover some of the atmospheric mysteries of a strange, scorching planet with a texture like cotton candy.
The exoplanet, which has been continuously observed by the Webb infrared telescope, is called WASP-17b and lies about 1,300 light-years from Earth. Its mass is about 0.8 times Jupiter’s, but its diameter is roughly twice Jupiter’s, making it a “super-puffy planet” with a texture comparable to cotton candy. WASP-17b is extremely close to its host star, completing an orbit in less than 4 Earth days; that proximity also sends the temperature of this “hot Jupiter” soaring.
Given this exoplanet’s extreme environment, it is hardly surprising that its atmosphere has an unusual structure. The research team used a new technique called transmission strings to map the outline of WASP-17b’s atmosphere. The study found that the planet’s atmosphere forms a ring with several protruding “gem-like” structures.
Team member Hannah Wakeford of the University of Bristol said in a statement: “Planets are temperamental, and atmospheres are complex and chaotic. It is tremendously exciting that all the observations corroborate one another, giving us a picture of the structured, dynamic nature of this giant planet thousands of light-years away.”
WASP-17b is extremely close to its host star and is tidally locked: one side of the planet permanently faces the star, with its dayside continually bombarded by stellar radiation; the other side is a cooler nightside that always faces deep space.
The researchers constructed an exceptionally complete 3D view of the exoplanet’s atmosphere and found, in line with theoretical and model predictions, marked differences in the chemical composition and temperature of WASP-17b’s atmosphere between its dayside and nightside.
This observation was made possible by the transmission strings technique, which captures the composition of light passing through the edge, or limb, of WASP-17b’s atmosphere from multiple angles as the planet transits in front of its star. The method improves on conventional approaches, whose models can analyze only the average light from the entire atmospheric limb.
Lili Alderson of Cornell University said: “We no longer assume the atmosphere is a ring with the same radius everywhere. This new technique can extract information at different distances from the center of the planet to the edge of its atmosphere, analyzing the atmospheric limb ring by ring.”
“Put simply, we no longer see just a ring; we can also pinpoint where the ‘gems’ are on it.”
The model shows that these “gem” structures form where the planet’s hot airflows reach the equator and the nightside, and where the atmosphere on the cooler side expands.
Alderson said: “Theory predicts a huge temperature difference between the planet’s morning and evening sides. The observations of WASP-17b closely match that trend and are almost exactly what we expected.”
The successful use of the transmission strings technique marks an exciting step toward modeling the atmospheres of the more than 6,000 objects in NASA’s exoplanet catalog.
Alderson concluded: “This study confirms that planets really are 3D objects, and that phenomena predicted by theory really do occur as they orbit their stars. Moving from simulations alone to seeing them happen with our own eyes is something else entirely.”
IT Home noted that the team’s research was published on Wednesday, October 14, in the journal *Nature Astronomy*.
References:
https://www.nature.com/articles/s41550-026-02986-4
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