The Mass Of The Exo-Venus Gliese 12 b, As Revealed By HARPS-N, ESPRESSO, And CARMENES

Small temperate planets are prime targets for exoplanet studies due to their possible similarities with the rocky planets in the Solar System.

M dwarfs are promising hosts since the planetary signals are within our current detection capabilities. Gliese 12 b is a Venus-sized temperate planet orbiting a quiet M dwarf. We present here the first precise mass measurement of this small exoplanet.

We performed a detailed analysis using HARPS-N, ESPRESSO, and CARMENES radial velocities, along with new and archival TESS, CHEOPS, and MuSCAT2/3 photometry data. From fitting the available data, we find that the planet has a radius of Rp=0.904+0.037−0.034R_⊕ and a mass of M_p=0.95+0.26−0.27M_⊕ (a 3.6σ measurement of the semi-amplitude K=0.70+0.19−0.20ms⁻¹), and is on an orbit with a period of 12.761421±0.000047d.

A variety of techniques were utilised to attenuate stellar activity signals. Gliese 12 b has an equilibrium temperature of T_eq=315±7K, assuming an albedo of zero, and a density consistent with that of Earth and Venus (ρp=7.0+2.3−2.1gcm⁻³). We find that Gliese 12 b has a predominantly rocky interior and simulations indicate that it is unlikely to have retained any of its primordial gaseous envelope.

The bulk properties of Gliese 12 b place it in an extremely sparsely-populated region of both mass–radius and density–Teq parameter space, making it a prime target for follow-up observations, including Lyman-α studies.

Daisy A. Turner, Yoshi Nike Emilia Eschen, Felipe Murgas, Annelies Mortier, Thomas G Wilson, Jorge Fernández Fernández, Giuseppe Morello, Shreyas Vissapragada, José A. Caballero, Stefan Dreizler, Jo Ann Egger, Alix Violet Freckelton, Nicole Gromek, Artie P. Hatzes, Ben Scott Lakeland, Evangelos Nagel, Luca Naponiello, Hugo M. Tabernero, Siegfried Vanaverbeke, Alexander Venner, María Rosa Zapatero Osorio, Pedro J. Amado, Víctor J. S. Béjar, Aldo Stefano Bonomo, Lars A. Buchhave, Andrew Collier Cameron, Ilaria Carleo, Priyanka Chaturvedi, Ryan Cloutier, Mario Damasso, Mangesh Daspute, Shishir Dholakia, Sjoerd Dufoer, Xavier Dumusque, Aldo Fabricio Martinez Fiorenzano, Adriano Ghedina, Avet Harutyunyan, Enrique Herrero, Ancy Anna John, Jorge Lillo-Box, Nicolas Lodieu, Mercedes López-Morales, Luca Malavolta, Luigi Mancini, Giacomo Mantovan, David Montes, Juan Carlos Morales, Belinda Nicholson, Jaume Orell-Miquel, Larissa Palethorpe, Enric Palle, Andreas Quirrenbach, Sabine Reffert, Ansgar Reiners, Ignasi Ribas, Ken Rice, André M. Silva, Alessandro Sozzetti, Manu Stalport, Lev Tal-Or, Trifon Trifonov, Stéphane Udry, Mathias Zechmeister

Comments: 20 pages, 13 figures; submitted to MNRAS; submission to arXiv coordinated with the MAROON-X team (first author: Madison Brady)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2506.20564 [astro-ph.EP] (or arXiv:2506.20564v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2506.20564
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Submission history
From: Daisy Amber Turner
[v1] Wed, 25 Jun 2025 16:00:56 UTC (3,422 KB)
https://arxiv.org/abs/2506.20564
Astrobiology,