Exoplanets, -moons, -comets

A Cloudy Fit To The Atmosphere of WASP-107 b

By Keith Cowing
Status Report
astro-ph.EP
March 13, 2026
Filed under , , , , ,
A Cloudy Fit To The Atmosphere of WASP-107 b
JWST observations of WASP-107 b (colored vertical bars) along with the best fit model (black line; Kzz = 109 cm2 s −1 ), resulting in a χ˜ 2 red = 3.4. The NIRISS observations are shifted vertically by 130 ppm to match the NIRCam data at the wavelengths where they overlap. The runs with higher and lower Kzz are shown with blue and brown lines, respectively, to illustrate the spectroscopic effects of varying the turbulent diffusivity. The simulated spectrum of a cloudless atmosphere is plotted in gray — astro-ph.EP

Context. WASP-107 b has been observed comprehensively by JWST in the near- and mid-IR bands, making it an ideal planet to probe the composition and internal dynamics. Recent analysis reveals a 8-10 um silicate feature, but it still remains uncertain how silicate clouds form on this planet.

Aims. We aim at fitting the complete JWST spectrum of WASP-107 b, from 0.9 um to 12 um with a physically motivated cloud model and self-consistent temperature profile. Methods. Two-stream radiative transfer is coupled to a cloud formation model until convergence between cloud and temperature profiles is reached. We search a model grid spanning metallicity, turbulent diffusivity, internal heat flux and nucleation parameters to find the best fit model.

Results. The silicate cloud feature at 10 um and the near-IR molecular band strength can be simultaneously and naturally explained without assuming a parametrized temperature profile. A moderate vertical diffusivity of Kzz = 10^9 cm^2 s^-1 is needed to bring the cloud particles to the upper atmosphere of WASP-107 b. This Kzz is favored by the joint fitting of the near-IR water feature and mid-IR silicate feature — both sensitive to clouds. From the strength of H2O and CO2 bands, our model suggests a metallicity 17 times solar.

Conclusions. Even in warm planets such as WASP-107 b, silicate clouds can form in the relatively cool upper atmosphere because turbulence uplifts vapor and cloud particles. Despite having considerably fewer degrees of freedom, the self-consistent modeling approach successfully fits WASP-107 b’s multi-wavelength data, instilling confidence in the derived physical parameters.

Helong Huang, Michiel Min, Chris W. Ormel, Achrène Dyrek, Nicolas Crouzet

Comments: 6 pages, 4 figures, 2 tables, accepted for publication in Astronomy & Astrophysics
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2603.12047 [astro-ph.EP] (or arXiv:2603.12047v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2603.12047
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Submission history
From: Helong Huang
[v1] Thu, 12 Mar 2026 15:22:29 UTC (988 KB)
https://arxiv.org/abs/2603.12047
Astrobiology, exoplanet,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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