Exoplanets & Exomoons

Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Transmission Spectroscopy

By Keith Cowing
Status Report
May 27, 2024
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Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Transmission Spectroscopy
5σ contrast limits at J (bottom left), H (top left), and K (bottom right) from Gemini/NIRI and at K ′ from Keck II/NIRC2 (top right). The combined images are shown in the insets of the panels, where Gliese 12 is at the star symbols. The maximum values of the image dynamic range were set to be 20 times higher than the noise levels at the edge areas. The locations corresponding to the identified possible source that was detected only in the J-band image are marked by arrow symbols and its contrast by a square symbol. Note that the source detection and contrast measurement were performed with the images after PSF subtractions. — astro-ph.EP

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 (Porb) of 12.76 days. The planet, Gliese 12b, was initially identified as a candidate with an ambiguous Porb from TESS data.

We confirmed the transit signal and Porb 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 logLX/Lbol≈−5.7.

Joint analysis of the light curves and RV measurements revealed that Gliese 12b has a radius of 0.96 ± 0.05 R, a 3σ 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 12b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12b to the small list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.

M. Kuzuhara, A. Fukui, J. H. Livingston, J. A. Caballero, J. P. de Leon, T. Hirano, Y. Kasagi, F. Murgas, N. Narita, M. Omiya, Jaume Orell-Miquel, E. Palle, Q. Changeat, E. Esparza-Borges, H. Harakawa, C. Hellier, Yasunori Hori, Kai Ikuta, H. T. Ishikawa, T. Kodama, T. Kotani, T. Kudo, J. C. Morales, M. Mori, E. Nagel, H. Parviainen, V. Perdelwitz, A. Reiners, I. Ribas, J. Sanz-Forcada, B. Sato, A. Schweitzer, H. M. Tabernero, T. Takarada, T. Uyama, N. Watanabe, M. Zechmeister, N. Abreu García, W. Aoki, C. Beichman, V. J. S. Béjar, T. D. Brandt, Y. Calatayud-Borras, I. Carleo, D. Charbonneau, K. A. Collins, T. Currie, J. P. Doty, S. Dreizler, G. Fernández-Rodríguez, I. Fukuda, D. Galán, S. Geraldía-González, J. González-Garcia, Y. Hayashi, C. Hedges, T. Henning, K. Hodapp, M. Ikoma, K. Isogai, S. Jacobson, M. Janson, J. M. Jenkins, T. Kagetani, E. Kambe, Y. Kawai, K. Kawauchi, E. Kokubo, M. Konishi, J. Korth, V. Krishnamurthy, T. Kurokawa, N. Kusakabe, J. Kwon, A. Laza-Ramos, F. Libotte, R. Luque, A. Madrigal-Aguado, Y. Matsumoto, D. Mawet, M. W. McElwain, P. P. Meni Gallardo, G. Morello, S. Munoz Torres, J. Nishikawa, S. K. Nugroho, M. Ogihara, A. Pel’aez-Torres, D. Rapetti, M. S’anchez-Benavente, M. Schlecker, S. Seager, E. Serabyn, T. Serizawa, M. Stangret, A. Takahashi, H. Teng, M. Tamura, Y. Terada, A. Ueda et al. (6 additional authors not shown)

Comments: 29 pages (20 pages in main body), 13 figures (10 figures in main body). Equal contributions from M. K. and A. F.. Accepted for Publication in ApJL at 2024 March 21
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2405.14708 [astro-ph.EP] (or arXiv:2405.14708v1 [astro-ph.EP] for this version)
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Journal reference: Published on 2024 May 23 by Astrophysical Journal Letters (ApJL) 967 L21
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Submission history
From: Masayuki Kuzuhara
[v1] Thu, 23 May 2024 15:42:09 UTC (4,916 KB)


Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻