Exoplanetology: Exoplanets & Exomoons

A Moderate Albedo From Reflecting Aerosols On The Dayside Of WASP-80 b Revealed By JWST/NIRISS Eclipse Spectroscopy

By Keith Cowing
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astro-ph.EP
March 26, 2025
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A Moderate Albedo From Reflecting Aerosols On The Dayside Of WASP-80 b Revealed By JWST/NIRISS Eclipse Spectroscopy
Haze (tholin and soot) models from Jacobs et al. (2023) for two metallicities: [M/H] = 0 (solid) and [M/H] = 1 (dashed). The various formation rates are shown in cool colors for the tholins and in warm colors for the soots. The haze models are compared to the NIRISS/SOSS eclipse spectrum of WASP-80 b. If the aerosols are hazes, they could consist of soots or tholins, with formation rates for tholins most likely lower than 10−11.5g cm−2 s−1. — astro-ph.EP

Secondary eclipse observations of exoplanets at near-infrared wavelengths enable the detection of thermal emission and reflected stellar light, providing insights into the thermal structure and aerosol composition of their atmospheres.

These properties are intertwined, as aerosols influence the energy budget of the planet. WASP-80 b is a warm gas giant with an equilibrium temperature of 825 K orbiting a bright late-K/early-M dwarf, and for which the presence of aerosols in its atmosphere have been suggested from previous HST and Spitzer observations.

We present an eclipse spectrum of WASP-80 b obtained with JWST NIRISS/SOSS, spanning 0.68 to 2.83 μm, which includes the first eclipse measurements below 1.1 μm for this exoplanet, extending our ability to probe light reflected by its atmosphere. When a reflected light geometric albedo is included in the atmospheric retrieval, our eclipse spectrum is best explained by a reflected light contribution of ∼30 ppm at short wavelengths, although further observations are needed to statistically confirm this preference.

We measure a dayside brightness temperature of TB=811+69−70 K and constrain the reflected light geometric albedo across the SOSS wavelength range to Ag=0.204+0.051−0.056, allowing us to estimate a 1-σ range for the Bond albedo of 0.148≲AB≲0.383.

By comparing our spectrum with aerosol models, we find that manganese sulfide and silicate clouds are disfavored, while cloud species with weak-to-moderate near-infrared reflectance, along with soots or low formation-rate tholin hazes, are consistent with our eclipse spectrum.

Kim Morel, Louis-Philippe Coulombe, Jason F. Rowe, David Lafrenière, Loïc Albert, Étienne Artigau, Nicolas B. Cowan, Lisa Dang, Michael Radica, Jake Taylor, Caroline Piaulet-Ghorayeb, Pierre-Alexis Roy, Björn Benneke, Antoine Darveau-Bernier, Stefan Pelletier, René Doyon, Doug Johnstone, Adam B. Langeveld, Romain Allart, Laura Flagg, Jake D. Turner

Comments: Accepted for publication in the Astronomical Journal; 28 pages, 16 figures, 4 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2503.15665 [astro-ph.EP] (or arXiv:2503.15665v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2503.15665
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Submission history
From: Kim Morel
[v1] Wed, 19 Mar 2025 19:30:42 UTC (4,681 KB)
https://arxiv.org/abs/2503.15665
Astrobiology,

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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