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JWST and Exoplanet Atmospheres
StargazeInWonder
post Jun 1 2023, 11:19 PM
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Further analysis of the TRAPPIST-1 b observations offer stronger constraints on any possible atmosphere, ruling out even a Mars-like atmosphere.

As far as surface conditions go, it appears that the closest solar system analogue to TRAPPIST-1 b, despite its larger-than-Earth size, is Mercury.

It will be interesting to see what Cycle 1 observations may have revealed about the other six planets in the system.

https://astrobiology.com/2023/05/constraini...bservation.html
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StargazeInWonder
post Jun 23 2023, 09:22 AM
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The scorecard for TRAPPIST-1 is now Vacuums 2, Atmospheres 0. (At least substantial atmospheres.)

JWST observations for TRAPPIST-1 c's dayside is consistent with being quite a bit like the Moon, though a thin atmosphere hasn't been ruled out.

https://www.nature.com/articles/s41586-023-06232-z

I'm not sure which planet in the system we'll learn about next – the observation programs and methodologies vary – but this is sure playing out in interesting fashion, like a serialized drama.
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StargazeInWonder
post Sep 1 2023, 10:15 AM
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This paper about LHS 475b almost certainly lends a clue as to why there have been JWST observations of several exoplanets that haven't yet led to publications summarizing those results: It's often going to be hard to reach specific conclusions, as the abstract explains, because of "the nature of the planet itself, rather than instrumental limits."

While the paper calls this planet "warm," it has an equilibrium temperature well above that of Mercury or Trappist-1b. This continues the streak that for terrestrial planets so hot, we have yet to confirm any atmosphere for any other them. In this case, however, no atmosphere has been ruled out.

https://www.nature.com/articles/s41550-023-02064-z
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Quetzalcoatl
post Sep 12 2023, 10:07 AM
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Bonjour,

Interesting detection of atmospheric gases of a sub-Neptune in habitable zone. With a potential presence of Dimethyl sulfide (DMS) to be confirmed...

https://www.nasa.gov/goddard/2023/webb-disc...phere-of-k2-18b
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Quetzalcoatl
post Oct 18 2023, 07:38 AM
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Bonjour,

Webb Detects Tiny Quartz Crystals in the Clouds of a Hot Gas Giant

https://www.nasa.gov/missions/webb/webb-det...-hot-gas-giant/

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StargazeInWonder
post Oct 18 2023, 09:42 PM
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There is the parable about someone looking for their lost keys under the light of streetlamps not because that is most likely where the keys were lost but because that's where light makes the search more feasible. In the current era of exoplanet characterization, planets that are large, hot, and/or close to their stars (and, of course, transiting) are not the only types of planet, and not the types we're most interested in, but they are the ones where JWST's capabilities make it possible to characterize them. It's fascinating, but also tantalizing as the candidate earthlike and habitable zone planets out there elude us for now.

I hope that, eg, Proxima b and the Tau Ceti planets lend themselves to characterization in the coming years, but it's clearly going to be a difficult challenge.
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Quetzalcoatl
post Nov 23 2023, 02:52 PM
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Bonjour,

NASA’s Webb Identifies Methane In an Exoplanet’s Atmosphere,

https://blogs.nasa.gov/webb/2023/11/22/nasa...ets-atmosphere/





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StargazeInWonder
post Nov 24 2023, 04:08 AM
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It's interesting that methane has been elusive in exoplanet atmospheres studied so far. I suppose that this is because most exoplanets with atmospheres studied so far have been hot ones, causing photodissociation to occur at a high rate. I think that we'll be seeing a lot more characterization of "warm" exoplanets soon.
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StargazeInWonder
post Jan 5 2024, 08:12 PM
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Another case of JWST finding that a hot terrestrial exoplanet shows no signs of a significant atmosphere. Probably not much of a surprise in this case, as the high density indicates not even a lot of silicates, much less volatiles.

https://astrobiology.com/2024/01/gj-367b-is...-sub-earth.html
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