2025/09/27 by Mehta, Nishil, Parmentier, Vivien, Tan, Xianyu +14
#Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2509.23406
Close-in warm Jupiters orbiting M-dwarf stars are expected to exhibit diverse atmospheric chemistry, with clouds playing a key role in shaping their albedo, heat distribution, and spectral properties. We study WASP-80b, a warm Jupiter orbiting an M-dwarf star, using the latest JWST panchromatic emission and transmission spectra to comprehensively characterise its atmosphere, including cloud coverage, chemical composition, and particle sizes, and compare the observations with predictions from the General Circulation Models (GCM). We use a GCM, ADAM (ADvanced Atmospheric MITgcm, formerly known as SPARC/MITgcm), combined with the latest JWST data to study the atmosphere of WASP-80b. A cloud module with radiatively active, tracer-based clouds is integrated with the GCM to study the effects on the atmosphere and the spectrum. Our results indicate that both emission and transmission spectra of WASP-80b are best reproduced by cloudless GCMs or by atmospheres containing large cloud particles (≥ 10~μm for Na2S, ≥ 1~μm for KCl, and ≥ 5~μm for MgSiO3), with smaller particles ruled out due to their strong radiative feedback. These findings emphasize the importance of particle size and composition in interpreting exoplanet atmospheric spectra and showcase the power of global modelling in constraining cloud properties. Among the expected clouds to form in WASP-80b, we show that only Na2S clouds forming particles larger than 10 μm, KCl clouds larger than 1 μm, or MgSiO3 clouds with particles larger than 5 μm can be compatible with the apparently cloudless emission and transmission spectra. Observations at shorter wavelengths in both emission and transmission could further distinguish between these cloudy scenarios and a truly cloudless atmosphere.