Left panel: IFU transmission map into the 7 fibers for single orientation, with the trajectory of Proxima b overlaid on top. Right panel: IFU transmission combining 2 exposures with a 30◦ offset. For both plots, we assumed median seeing (0.76″) and elevation (43◦ ) conditions, and λ = 840 nm. — astro-ph.EP
The characterization of exoplanet atmospheres is one of the key topics in modern astrophysics. To date, transmission spectroscopy has been the primary method used, but upcoming instruments will lay the foundation for advancing reflected-light spectroscopy.
The main challenge in this area of research is the high contrast ratio between the planet and its star. RISTRETTO, a high-resolution integral-field spectrograph designed for ESO’s VLT, aims to address these limitations through a combination of extreme AO, coronagraphy, and high-resolution spectroscopy. The goal of this paper is to demonstrate the detectability of the temperate rocky planet Proxima b with RISTRETTO, using realistic end-to-end simulations and a specifically developed data analysis methodology.
We created high-resolution star and planet spectra, selecting realistic observational epochs and incorporating the predicted performance of the AO and coronagraphic systems. We implemented noise and spectrograph effects through the Pyechelle spectrograph simulator. We then applied a new methodology to isolate the signal of the planet from the stellar one and proceeded to fit several planetary models in order of increasing complexity.
We also introduced a method to determine the sky orientation of the stellar spin axis, which constrains the orientation of the planetary orbit for aligned systems. Assuming an Earth-like atmosphere, our results show that RISTRETTO can detect Proxima b in reflected light in about 55 hours of observing time, offering the ability to characterize the planet orbital inclination, true mass, and broadband albedo.
In addition, molecular absorption by O2 and H2O can be detected in about 85 hours of observations. These findings highlight the potential of RISTRETTO to significantly advance the field of exoplanetary science by enabling reflected-light spectroscopy of a sample of nearby exoplanets.
Maddalena Bugatti, Christophe Lovis, Nicolas Billot, Nicolas Blind, Baptiste Lavie, Martin Turbet, Bruno Chazelas, Francesco Pepe
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2509.07644 [astro-ph.EP] (or arXiv:2509.07644v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2509.07644
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Related DOI:
https://doi.org/10.1051/0004-6361/202556398
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Submission history
From: Maddalena Bugatti
[v1] Tue, 9 Sep 2025 12:12:04 UTC (3,653 KB)
https://arxiv.org/abs/2509.07644
Astrobiology