2026-06-30T16:26:56Zivo://CDS.VizieR/J/MNRAS/545/F17032026-03-02T06:25:50ZJ.MNRASIVOARV data for Gliese 12Small 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=0.93+/-0.06R_Earth_ and a mass of Mp=0.95^+0.29^_-0.30_M_Earth_ (a 3.2-sigma measurement of the semi-amplitude K=0.67+/-0.21m/s), and is on an orbit with a period of 12.761418^+0.000060^_-0.000055_d. A variety of techniques were utilised 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 {rho}=6.4+/-2.4g/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-Teq parameter space, making it a prime target for follow-up observations, including Lyman-alpha studies.m-starssolar-system-planetsmultiple-starsexoplanetsradial-velocityvisible-astronomystellar-astronomyobservational-astronomyexoplanet-astronomysolar-system-astronomyhttps://dc.g-vo.org/rr/q/lp/custom/CDS.VizieR/J/MNRAS/545/F1703https://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/545/F17032026MNRAS.545f1703Thttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/545/F1703Turner D.A.Eschen Y.N.E.Murgas F.Mortier A.Wilson T.G.,Fernandez Fernandez J.Gromek N.Morello G.Tabernero H.M.Egger J.A.,Vissapragada S.Caballero J.A.Dreizler S.Freckelton A.V.Hatzes A.P.,Lakeland B.S.Nagel E.Naponiello L.Vanaverbeke S.Venner A.,Zapatero Osorio M.R.Amado P.J.Bejar V.J.S.Bonomo A.S.Buchhave L.A.,Collier Cameron A.Carleo I.Chaturvedi P.Cloutier R.Damasso M.,Daspute M.Dholakia S.Dufoer S.Dumusque X.Martinez Fiorenzano A.F.,Ghedina A.Harutyunyan A.Herrero E.John A.A.Lillo-Box J.Lodieu N.,Lopez-Morales M.Malavolta L.Mancini L.Mantovan G.Montes D.,Morales J.C.Nicholson B.Orell-Miquel J.Palethorpe L.Palle E.,Quirrenbach A.Reffert S.Reiners A.Ribas I.Rice K.Silva A.M.,CDS2026https://cds.unistra.fr/vizier-org/licences_vizier.htmlCDS support team <cds-question@unistra.fr>DatasetAstroObjectsastronomy