TRAPPIST-1

JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e

By Keith Cowing
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astro-ph.EP
September 9, 2025
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JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e
White-light TRAPPIST-1 e JWST/NIRSpec PRISM transit light curves. (Top) Datapoints of the transit event (grey; binned at a cadence of 14-seconds) along with the best-fit transit plus systematics model (black; which includes a visit-long slope and a GP; see text for details). The date at which each observation was obtained is indicated at the top of each panel. (Middle) Residuals of the data minus the best-fit light curve model in parts-per-million (ppm); the root-mean-square of the data at this 14-second cadence is indicated for each observation. (Bottom) Light curves at the Hα line (0.656±0.02 µm, in parts per thousand; ppt) at the same cadence as the white-light curves (pale blue points), and binned at 5-minutes (solid blue points); note how a flare is revealed at about −0.25 hr in this light curve as the most likely explanation for the bump in the July 23, 2023 transit event. — astro-ph.EP

TRAPPIST-1 e is one of the very few rocky exoplanets that is both amenable to atmospheric characterization and that resides in the habitable zone of its star — located at a distance from its star such that it might, with the right atmosphere, sustain liquid water on its surface.

Here, we present a set of 4 JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e obtained from mid to late 2023. Our transmission spectra exhibit similar levels of stellar contamination as observed in prior works for other planets in the TRAPPIST-1 system (Lim et al, 2023; Radica et al., 2024), but over a wider wavelength range, showcasing the challenge of characterizing the TRAPPIST-1 planets even at relatively long wavelengths (3-5 um).

While we show that current stellar modeling frameworks are unable to explain the stellar contamination features in our spectra, we demonstrate that we can marginalize over those features instead using Gaussian Processes, which enables us to perform novel exoplanet atmospheric inferences with our transmission spectra.

In particular, we are able to rule out cloudy, primary H2-dominated (≳ 80% by volume) atmospheres at better than a 3σ level. Constraints on possible secondary atmospheres on TRAPPIST-1 e are presented in a companion paper (Glidden et al., 2025). Our work showcases how JWST is breaking ground into the precisions needed to constrain the atmospheric composition of habitable-zone rocky exoplanets.

Néstor Espinoza, Natalie H. Allen, Ana Glidden, Nikole K. Lewis, Sara Seager, Caleb I. Cañas, David Grant, Amélie Gressier, Shelby Courreges, Kevin B. Stevenson, Sukrit Ranjan, Knicole Colón, Brett M. Morris, Ryan J. MacDonald, Douglas Long, Hannah R. Wakeford, Jeff A. Valenti, Lili Alderson, Natasha E. Batalha, Ryan C. Challener, Jingcheng Huang, Zifan Lin, Dana R. Louie, Elijah Mullens, Daniel Valentine, C. Matt Mountain, Laurent Pueyo, Marshall D. Perrin, Andrea Bellini, Jens Kammerer, Mattia Libralato, Isabel Rebollido, Emily Rickman, Sangmo Tony Sohn, Roeland P. van der Marel

Comments: Published in ApJ Letters, 16 pages, 4 figures (not including appendix). Check the companion paper (Glidden+2025) for secondary atmospheric interpretation. Data and scripts to reproduce all figures: this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2509.05414 [astro-ph.EP] (or arXiv:2509.05414v1 [astro-ph.EP] for this version)

https://doi.org/10.48550/arXiv.2509.05414
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Related DOI:
https://doi.org/10.3847/2041-8213/adf42e
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Submission history
From: Néstor Espinoza
[v1] Fri, 5 Sep 2025 18:00:06 UTC (2,270 KB)
https://arxiv.org/abs/2509.05414
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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