D. A. Turner, Y. Eschen, F. Murgas, A. Mortier, T. G. Wilson, J. Fernández Fernández, N. Gromek, G. Morello, H. M. Tabernero, J. A. Egger, S. Vissapragada, J. A. Caballero, S. Dreizler, A. V. Freckelton, A. P. Hatzes, B. S. Lakeland, E. Nagel, L. Naponiello, S. Vanaverbeke, A. Venner, M. R. Zapatero Osorio, P. J. Amado, V. J. S. Béjar, A. S. Bonomo, L. A. Buchhave, A. Collier Cameron, I. Carleo, P. Chaturvedi, R. Cloutier, M. Damasso, M. Daspute, S. Dholakia, S. Dufoer, X. Dumusque, A. F. Martinez Fiorenzano, A. Ghedina, A. Harutyunyan, E. Herrero, A. A. John, J. Lillo-Box, N. Lodieu, M. López-Morales, L. Malavolta, L. Mancini, G. Mantovan, D. Montes, J. C. Morales, B. Nicholson, J. Orell-Miquel, L. Palethorpe, E. Palle, A. Quirrenbach, S. Reffert, A. Reiners, I. Ribas, K. Rice, A. M. Silva, A. Sozzetti, M. Stalport, L. Tal-Or, T. Trifonov, S. Udry, M. Zechmeister
Abstract
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 Rp=0.93±0.06R⊕ and a mass of Mp=0.95+0.29−0.30M⊕ (a 3.2σ measurement of the semi-amplitude K=0.67±0.21ms−1), and is on an orbit with a period of 12.761418+0.000060−0.000055d. A variety of techniques were utilized to attenuate stellar activity signals. Gliese 12 b has an equilibrium temperature of Teq=317±8K, assuming an albedo of zero, and a density consistent with that of Earth and Venus (ρp=6.4±2.4gcm−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.
Keywords
techniques: radial velocities / planets and satellites: detection / planets and satellites: individual: Gliese 12 b / planets and satellites: interiors / planets and satellites: terrestrial planets / stars: individual: Gliese 12
Monthly Notices of the Royal Astronomical Society
Volume 545, Issue staf1703, Page 25
2026 January
