Combined Analysis of the 12.8 and 15 μm JWST/MIRI Eclipse Observations of TRAPPIST-1 b
The first JWST/MIRI photometric observations of TRAPPIST-1 b allowed for the detection of the thermal emission of the planet at 15 μm, suggesting that the planet could be a bare rock with a zero albedo and no redistribution of heat. These observations at 15 μm were acquired as part of GTO time that included a twin program at 12.8 μm in order to have a measurement in and outside the CO2 absorption band.
Here we present five new occultations of TRAPPIST-1 b observed with MIRI in an additional photometric band at 12.8 μm. We perform a global fit of the 10 eclipses and derive a planet-to-star flux ratio and 1-σ error of 452 ± 86 ppm and 775 ± 90 ppm at 12.8 μm and 15 μm, respectively.
We find that two main scenarios emerge. An airless planet model with an unweathered (fresh) ultramafic surface, that could be indicative of relatively recent geological processes fits well the data. Alternatively, a thick, pure-CO2 atmosphere with photochemical hazes that create a temperature inversion and result in the CO2 feature being seen in emission also works, although with some caveats.
Our results highlight the challenges in accurately determining a planet’s atmospheric or surface nature solely from broadband filter measurements of its emission, but also point towards two very interesting scenarios that will be further investigated with the forthcoming phase curve of TRAPPIST-1 b.
Elsa Ducrot, Pierre-Olivier Lagage, Michiel Min, Michael Gillon, Taylor J. Bell, Pascal Tremblin, Thomas Greene, Achrene Dyrek, Jeroen Bouwman, Rens Waters, Manuel Gudel, Thomas Henning, Bart Vandenbussche, Olivier Absil, David Barrado, Anthony Boccaletti, Alain Coulais, Leen Decin, Billy Edwards, Rene Gastaud, Alistair Glasse, Sarah Kendrew, Goran Olofsson, Polychronis Patapis, John Pye, Daniel Rouan, Niall Whiteford, Ioannis Argyriou, Christophe Cossou, Adrian M. Glauser, Oliver Krause, Fred Lahuis, Pierre Royer, Silvia Scheithauer, Luis Colina, Ewine F. van Dishoeck, Goran Ostlin, Tom P. Ray, Gillian Wright
Comments: 49 pages, 3 main text figure, 2 extended figures, 10 supplementary figures, accepted for publication in Nature Astronomy on October 29, 2024
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2412.11627 [astro-ph.EP] (or arXiv:2412.11627v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2412.11627
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Related DOI:
https://doi.org/10.1038/s41550-024-02428-z
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Submission history
From: Elsa Ducrot
[v1] Mon, 16 Dec 2024 10:11:40 UTC (10,288 KB)
https://arxiv.org/abs/2412.11627
Astrobiology,
