JWST data resolve a puffy hot Jupiter's atmosphere into a ring with raised 'gems'
Astronomers used JWST data and a technique called transmission strings to map WASP-17b's atmosphere as a ring with raised 'gems'. The temperature contrast they found matches theory, so the result is a test of the method.
The Scientist · Science desk
Key figures for WASP-17b: mean density roughly 0.1 times Jupiter's; mass around 0.8 times Jupiter's; volume about 8 times Jupiter's.
| Figure | Value | Note | Claim |
|---|---|---|---|
| Mean density, roughly, against Jupiter's | 0.1 × Jupiter | 15 | |
| Mass, around | 0.8 Jupiter masses | 11 | |
| Volume, about | 8 × Jupiter | 15 |
What happened
- The modelling put one gem where hot winds reach the equator and nightside, and the atmosphere of the cooler side inflates.
- WASP-17b has about 0.8 Jupiter masses but is around twice as wide. That gives it a super-puff consistency.
- The team's paper appeared on Wednesday, Oct. 14, in Nature Astronomy.
Why it matters
- What's now possible capability Researchers can place features at positions around a transiting planet's limb. A single averaged value cannot do that.
- What doesn't add up contradiction The result is described as structured and complex, yet the team says the morning-evening temperature contrast matched theory. The result replaces the assumption that the limb has one radius.
- What it limits constraint The evidence comes from one planet, so using the ring-and-gems shape as a template for other hot Jupiters is untested.
Whether this shows atmospheres to be more complex than models assume depends on which model. The one the technique replaces is narrow. Traditional modelling maps light only as an average across the entire limb [8]. Lili Alderson of Cornell University said: "Rather than assuming your atmosphere is a circle with the same radius all the way around, our technique allows you to pull out different distances from the center to the edge of the planet." [9] Applied to JWST data on WASP-17b, the technique returned an atmosphere shaped like a ring with prominent gems rising from it [5][6].
On the physics, the result lands close to expectation. Space reports that the planet's chemical composition and temperature shift between dayside and nightside according to theory and modelling [1]. Alderson said: "Theory predicts that the morning and the evening sides should have a strong temperature difference" [2]. WASP-17b, she said, was "pretty much bang-on what we thought it would be" [3]. Hannah Wakeford of the University of Bristol said the numbers "showed us this very structured, dynamical picture of this giant world" [14]. The map adds spatial detail to a picture that theory already had.
The planet is an extreme case. It has about 0.8 times Jupiter's mass and is around twice as wide [11]. That puts its mean density near a tenth of Jupiter's [15]. The figure is rough, because the source gives the width only as "around twice".
Space's report is built on a team statement. It does not include the number of transits observed, the JWST instruments used, or an uncertainty on the height of the gems. Those details would be in the Nature Astronomy paper [12].
The result cannot show whether any existing model misses real structure. That would take a planet where the map and the prediction disagree. In our view the result validates the method on a planet where theory had a prediction to check against. Alderson called it "proof of concept that planets are, in fact, 3D objects" [4], and Space describes it as a step forward for modelling the more than 6,000 worlds in NASA's exoplanet catalog [13].
What to watch
- Transmission strings applied to other transiting planets, especially denser hot Jupiters, to see whether a ring with gems recurs.
- A mapped planet whose temperatures depart from the predicted morning-evening contrast, which would be the first sign that existing models miss structure.
- The Nature Astronomy paper's own numbers: transits observed, instruments used and the uncertainty on the gems.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence55
- Adoption
- Not scored
- Hype gap+15
- Incentives
- Not scored
- Confidence60
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Researchers found that WASP-17b's atmosphere has a chemical composition and temperature that shift between dayside and nightside according to theory and modelling.
- [2]
Alderson said: "Theory predicts that the morning and the evening sides should have a strong temperature difference".
- [3]
Alderson said WASP-17b was "pretty much bang-on what we thought it would be".
- [4]
Alderson said: "This is proof of concept that planets are, in fact, 3D objects".
- [5]
Using JWST data and a new technique called transmission strings, a team of scientists mapped the contours of the atmosphere of the exoplanet WASP-17b.
- [6]
The team found that WASP-17b's atmosphere is shaped like a ring with prominent 'gems' rising from it.
- [7]
The transmission strings technique tracked WASP-17b as it transited in front of its star, capturing the composition of light around the edge of the planet's atmosphere (the limb) from different angles.
- [8]
Traditional modelling only maps light as an average across the entire limb.
- [9]
Lili Alderson of Cornell University said: "Rather than assuming your atmosphere is a circle with the same radius all the way around, our technique allows you to pull out different distances from the center to the edge of the planet."
- [10]
The modelling showed a 'gem' where hot winds from the planet reach the equator and the nightside of WASP-17b, and the atmosphere of the cooler side inflates.
- [11]
WASP-17b has a mass around 0.8 times that of Jupiter but is around twice as wide as Jupiter, giving it a 'super-puff' consistency.
- [12]
The team's research was published on Wednesday (Oct. 14) in the journal Nature Astronomy.
- [13]
Space describes the successful application of transmission strings as an exciting step forward in the modelling of the atmospheres of the over 6,000 worlds in NASA's exoplanet catalog.
- [14]
Hannah Wakeford of the University of Bristol said all of the numbers "came together and showed us this very structured, dynamical picture of this giant world over 1,000 light-years away".
- [15]
WASP-17b's mean density is roughly 0.1 times Jupiter's, since its mass is about 0.8 Jupiter masses and its width about twice Jupiter's, so its volume is about 8 times larger.
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Sources
1 independent publisher whose own reporting we read for this story.
- space.comScientists find 'gemstones' in atmosphere of bizarre, scorching-hot 'marshmallow' exoplanet
1 article · October 16, 2026
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Topics
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Entities
- Nature AstronomyFollow
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- James Webb Space TelescopeFollow
- Transmission stringsFollow
- Hannah WakefordFollow
- WASP-17bFollow