Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with <i>TESS</i> and <i>CHEOPS</i>
Shishir Dholakia, Larissa Palethorpe, Alexander Venner, Annelies Mortier, T. G. Wilson, Chelsea X. Huang, Ken Rice, Vincent Van Eylen, Emma Nabbie, Ryan Cloutier, W. Boschin, David R. Ciardi, L. Delrez, Georgina Dransfield, Elsa Ducrot, Zahra Essack, Mark E. Everett, M. Gillon, M. J. Hooton, Michelle Kunimoto, David W. Latham, Mercedes López‐Morales, Bin Li, Fan Li, Scott McDermott, Simon J. Murphy, C. A. Murray, Sara Seager, Mathilde Timmermans, A. H. M. J. Triaud, Daisy A. Turner, Joseph D. Twicken, Andrew Vanderburg, Su Wang, Robert A. Wittenmyer, D. J. Wright
Abstract
ABSTRACT We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors 42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory, as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of 12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.