Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Transmission Spectroscopy
Creators: name: Kuzuhara, Masayuki
name: Fukui, Akihiko
name: Livingston, John H.
name: Caballero, José A.
name: Leon, Jerome P. De
name: Hirano, Teruyuki
name: Kasagi, Yui
name: Murgas, Felipe
name: Narita, Norio
name: Omiya, Masashi
name: Orell-Miquel, Jaume
name: Palle, Enric
name: Changeat, Quentin
name: Esparza-Borges, Emma
name: Harakawa, Hiroki
name: Hellier, Coel
name: Hori, Yasunori
name: Ikuta, Kai
name: Ishikawa, Hiroyuki Tako
name: Kodama, Takanori
name: Kotani, Takayuki
name: Kudo, Tomoyuki
name: Morales, Juan C.
name: Mori, Mayuko
name: Nagel, Evangelos
name: Parviainen, Hannu
name: Perdelwitz, Volker
name: Reiners, Ansgar
name: Ribas, Ignasi
name: Sanz-Forcada, Jorge
name: Sato, Bun’ei
name: Schweitzer, Andreas
name: Tabernero, Hugo M.
name: Takarada, Takuya
name: Uyama, Taichi
name: Watanabe, Noriharu
name: Zechmeister, Mathias
name: García, Néstor Abreu
name: Aoki, Wako
name: Beichman, Charles
name: Béjar, Víctor J. S.
name: Brandt, Timothy D.
name: Calatayud-Borras, Yéssica
name: Carleo, Ilaria
name: Charbonneau, David
name: Collins, Karen A.
name: Currie, Thayne
name: Doty, John P.
name: Dreizler, Stefan
name: Fernández-Rodríguez, Gareb
name: Fukuda, Izuru
name: Galán, Daniel
name: Geraldía-González, Samuel
name: González-Rodríguez, Josafat
name: Hayashi, Yuya
name: Hedges, Christina
name: Henning, Thomas
name: Hodapp, Klaus
name: Ikoma, Masahiro
name: Isogai, Keisuke
name: Jacobson, Shane
name: Janson, Markus
name: Jenkins, Jon M.
name: Kagetani, Taiki
name: Kambe, Eiji
name: Kawai, Yugo
name: Kawauchi, Kiyoe
name: Kokubo, Eiichiro
name: Konishi, Mihoko
name: Korth, Judith
name: Krishnamurthy, Vigneshwaran
name: Kurokawa, Takashi
name: Kusakabe, Nobuhiko
name: Kwon, Jungmi
name: Laza-Ramos, Andrés
name: Libotte, Florence
name: Luque, Rafael
name: Madrigal-Aguado, Alberto
name: Matsumoto, Yuji
name: Mawet, Dimitri
name: McElwain, Michael W.
name: Gallardo, Pedro Pablo Meni
name: Morello, Giuseppe
name: Torres, Sara Muñoz
name: Nishikawa, Jun
name: Nugroho, Stevanus K.
name: Ogihara, Masahiro
name: Peláez-Torres, Alberto
name: Rapetti, David
name: Sánchez-Benavente, Manuel
name: Schlecker, Martin
name: Seager, Sara
name: Serabyn, Eugene
name: Serizawa, Takuma
name: Stangret, Monika
name: Takahashi, Aoi
name: Teng, Huan-Yu
name: Tamura, Motohide
name: Terada, Yuka
name: Ueda, Akitoshi
name: Usuda, Tomonori
name: Vanderspek, Roland
name: Vievard, Sébastien
name: Watanabe, David
name: Winn, Joshua N.
name: Osorio, Maria Rosa Zapatero
Publisher: name: AAS
Year: 2024

description: Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (P orb) of 12.76 days. The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous P orb from TESS data. We confirmed the transit signal and P orb using ground-based photometry with MuSCAT2 and MuSCAT3, and validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host star is inactive, with an X-ray-to-bolometric luminosity ratio of . Joint analysis of the light curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R ?, a 3? mass upper limit of 3.9 M ?, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric (TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.