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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 orbitin...

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Main Authors: Turner, Daisy (Author) , Eschen, Yoshi Nike Emilia (Author) , Murgas, Felipe (Author) , Mortier, Annelies (Author) , Wilson, Thomas G (Author) , Fernández Fernández, Jorge (Author) , Gromek, Nicole (Author) , Morello, Giuseppe (Author) , Tabernero, Hugo M (Author) , Egger, Jo Ann (Author) , Vissapragada, Shreyas (Author) , Caballero, José A (Author) , Dreizler, Stefan (Author) , Freckelton, Alix Violet (Author) , Hatzes, Artie P (Author) , Lakeland, Ben Scott (Author) , Nagel, Evangelos (Author) , Naponiello, Luca (Author) , Vanaverbeke, Siegfried (Author) , Venner, Alexander (Author) , Zapatero Osorio, María Rosa (Author) , Amado, Pedro J (Author) , Béjar, Víctor J S (Author) , Bonomo, Aldo Stefano (Author) , Buchhave, Lars A (Author) , Collier Cameron, Andrew (Author) , Carleo, Ilaria (Author) , Chaturvedi, Priyanka (Author) , Cloutier, Ryan (Author) , Damasso, Mario (Author) , Daspute, Mangesh (Author) , Dholakia, Shishir (Author) , Dufoer, Sjoerd (Author) , Dumusque, Xavier (Author) , Martinez Fiorenzano, Aldo Fabricio (Author) , Ghedina, Adriano (Author) , Harutyunyan, Avet (Author) , Herrero, Enrique (Author) , John, Ancy Anna (Author) , Lillo-Box, Jorge (Author) , Lodieu, Nicolas (Author) , López-Morales, Mercedes (Author) , Malavolta, Luca (Author) , Mancini, Luigi (Author) , Mantovan, Giacomo (Author) , Montes, David (Author) , Morales, Juan Carlos (Author) , Nicholson, Belinda (Author) , Orell-Miquel, Jaume (Author) , Palethorpe, Larissa (Author) , Palle, Enric (Author) , Quirrenbach, Andreas (Author) , Reffert, Sabine (Author) , Reiners, Ansgar (Author) , Ribas, Ignasi (Author) , Rice, Ken (Author) , Silva, André M (Author) , Sozzetti, Alessandro (Author) , Stalport, Manu (Author) , Tal-Or, Lev (Author) , Trifonov, Trifon (Author) , Udry, Stéphane (Author) , Zechmeister, Mathias (Author)
Format: Article (Journal)
Language:English
Published: January 2026
In: Monthly notices of the Royal Astronomical Society
Year: 2026, Volume: 545, Issue: 1, Pages: 1-25
ISSN:1365-2966
DOI:10.1093/mnras/staf1703
Online Access:Verlag, kostenfrei, Volltext: https://doi.org/10.1093/mnras/staf1703
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Author Notes:Daisy A. Turner, Yoshi Nike Emilia Eschen, Felipe Murgas, Annelies Mortier, Thomas G. Wilson, Jorge Fernández Fernández, Nicole Gromek, Giuseppe Morello, Hugo M. Tabernero, Jo Ann Egger, Shreyas Vissapragada, José A. Caballero, Stefan Dreizler, Alix Violet Freckelton, Artie P. Hatzes, Ben Scott Lakeland, Evangelos Nagel, Luca Naponiello, 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 and Mathias Zechmeister
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Summary: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 (High Accuracy Radial velocity Planet Searcher for the Northern Hemisphere), ESPRESSO (Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations), and CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs) radial velocities, along with new and archival TESS (Transiting Exoplanet Survey Satellite), CHEOPS (CHaracterising ExOPlanet Satellite), and MuSCAT2/3 (Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets) photometry data. From fitting the available data, we find that the planet has a radius of $R_\mathrm{p} = 0.93\pm 0.06 \, \mathrm{R_{\rm{\oplus }}}$ and a mass of $M_\mathrm{p} = 0.95^{+0.29}_{-0.30} \, \mathrm{M_{\rm{\oplus }}}$ (a $3.2\sigma$ measurement of the semi-amplitude $K=0.67\pm 0.21\, \mathrm{m\, s^{-1}}$), and is on an orbit with a period of $12.761418^{+0.000060}_{-0.000055}\, \mathrm{d}$. A variety of techniques were utilized to attenuate stellar activity signals. Gliese 12 b has an equilibrium temperature of $T_\mathrm{eq}=317 \pm 8\, \mathrm{K}$, assuming an albedo of zero, and a density consistent with that of Earth and Venus ($\rho _\mathrm{p}=6.4\pm 2.4\, \mathrm{g\, cm^{-3}}$). 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-$T_\mathrm{eq}$ parameter space, making it a prime target for follow-up observations, including Lyman-$\alpha$ studies.
Item Description:Vorab veröffentlicht: 07. Oktober 2025
Gesehen am 20.02.2026
Physical Description:Online Resource
ISSN:1365-2966
DOI:10.1093/mnras/staf1703

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