An Eccentric Sub-Neptune Moving Into the Evaporation Desert<sup>*</sup>

Abstract Though missions such as Kepler, K2, and TESS have discovered &gt;2000 sub-Neptune and Neptunian planets, there is a dearth of such planets at close-in ( P ≲ 3 days) orbits. This feature, called the Neptune desert or the evaporation desert, is believed to be primarily shaped by planetary migration and photoevaporation. However, this region is not completely devoid of planets—a small number of very hot Neptunes reside within the desert. These planets provide an opportunity to directly probe the effects of migration and photoevaporation. We present confirmation of TOI-5800 b, an eccentric sub-Neptune on an ≈2.6 day period that is likely actively undergoing tidal migration. We use radial velocity measurements from the Carnegie Planet Finder Spectrograph to constrain TOI-5800 b’s mass and eccentricity. We find that it has an unusually high eccentricity (0.39 ± 0.07) for its short orbit. TOI-5800 b is therefore currently experiencing high levels of tidal heating as it moves into the desert. Ranked as a top candidate for transmission and emission spectroscopy within its temperature and radius regime, TOI-5800 b is a prime target for atmospheric characterization with the James Webb Space Telescope. TOI-5800 b presents a unique opportunity to study the atmosphere of a planet undergoing tidal heating and to probe the composition of sub-Neptune planets.

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Publication Details

Journal
The Astrophysical Journal Letters
Published
2025-08-11
DOI
https://doi.org/10.3847/2041-8213/adea46
Citations
2
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
2.31

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article

An Eccentric Sub-Neptune Moving Into the Evaporation Desert*

Tansu Daylan, Sydney Jenkins, Julien de Wit, Andrew W. Mayo et al.
2 citations
The Astrophysical Journal Letters
Astro and Planetary Science
2.31
article

An Eccentric Sub-Neptune Moving Into the Evaporation Desert*

Tansu Daylan, Sydney Jenkins, Julien de Wit, Andrew W. Mayo, H. P. Osborn, M. Lendl, Juliette Becker, David W. Latham, Aaron Householder, R. Paul Butler, M. Calkins, Stephen A. Shectman, Jeffrey D. Crane, Johanna Teske, Andrew Vanderburg, Michael Fausnaugh, Alexander Venner, C. Broeg, Gilbert A. Esquerdo, G. Scandariato, Carl Ziegler, A. Krenn, Jason D. Eastman, Sarah Millholland, Stephanie Striegel, Joseph E. Rodriguez, L. Fossati, D. Ehrenreich, T. G. Wilson, Allyson Bieryla, Yadira Gaibor, Emily Pass, Ritika Sethi, P. Berlind
article en
2 citations

Abstract

Abstract Though missions such as Kepler, K2, and TESS have discovered &gt;2000 sub-Neptune and Neptunian planets, there is a dearth of such planets at close-in ( P ≲ 3 days) orbits. This feature, called the Neptune desert or the evaporation desert, is believed to be primarily shaped by planetary migration and photoevaporation. However, this region is not completely devoid of planets—a small number of very hot Neptunes reside within the desert. These planets provide an opportunity to directly probe the effects of migration and photoevaporation. We present confirmation of TOI-5800 b, an eccentric sub-Neptune on an ≈2.6 day period that is likely actively undergoing tidal migration. We use radial velocity measurements from the Carnegie Planet Finder Spectrograph to constrain TOI-5800 b’s mass and eccentricity. We find that it has an unusually high eccentricity (0.39 ± 0.07) for its short orbit. TOI-5800 b is therefore currently experiencing high levels of tidal heating as it moves into the desert. Ranked as a top candidate for transmission and emission spectroscopy within its temperature and radius regime, TOI-5800 b is a prime target for atmospheric characterization with the James Webb Space Telescope. TOI-5800 b presents a unique opportunity to study the atmosphere of a planet undergoing tidal heating and to probe the composition of sub-Neptune planets.

The Astrophysical Journal LettersVol. 989(2)
University of Geneva (CH), University of Bern (CH), Texas Tech University (US), Ames Research Center (US), University of Wisconsin–Madison (US), Austrian Academy of Sciences (AT), University of Southern Queensland (AU), Carnegie Institution for Science (US), Stephen F. Austin State University (US), ETH Zurich (CH), University of Warwick (GB), Space Research Institute (AT), Osservatorio Astrofisico di Catania (IT), Center for Astrophysics Harvard & Smithsonian (US), Carnegie Observatories (US), Massachusetts Institute of Technology (US), San Francisco State University (US), International Space Science Institute (CH), Michigan State University (US), Search for Extraterrestrial Intelligence (US)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Washington University in St. Louis, UK Space Agency, University of Warwick, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Ames Research Center, Science Mission Directorate
Openalex Percentile: Top 11%
Astro and Planetary Science
2.31
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