Gliese 367 b / Tahay
Discovery[1]
Discovered byKristine Lam, et al.
Discovery siteTESS
Discovery dateDecember 2021
Transit
Designations
Tahay,[2] TOI-731.01
Orbital characteristics[3]
0.00709±0.00027 AU
Eccentricity0.06+0.07
−0.04
0.3219225±0.0000002 d
Inclination79.89°+0.87°
−0.85°
66°+41°
−108°
Semi-amplitude1.003±0.078 m/s
StarGliese 367
Physical characteristics[3]
Mean radius
0.699±0.024 R🜨
Mass0.633±0.050 M🜨
Mean density
10.2±1.3 g/cm3
Temperature1,728±90 K (1,455 °C; 2,651 °F, dayside)[4]
<847 K (574 °C; 1,065 °F, nightside)[4]

    Gliese 367 b, formally named Tahay,[2] is a sub-Earth exoplanet orbiting the red dwarf star Gliese 367 (GJ 367), 30.7 light-years (9.4 parsecs) from Earth in the constellation of Vela.[5] The exoplanet takes just 7.7 hours to orbit its star, one of the shortest orbits of any planet.[1]

    As of 2022, Gliese 367 b is the smallest known exoplanet within 10 parsecs of the Solar System,[6] and the second-least massive after Proxima Centauri d.

    Nomenclature

    In August 2022, this planet and its host star were included among 20 systems to be named by the third NameExoWorlds project.[7] The approved names, proposed by a team from Chile, were announced in June 2023. Gliese 367 b is named Tahay and its host star is named Añañuca, after names for the endemic Chilean wildflowers Calydorea xiphioides and Phycella cyrtanthoides. Calydorea xiphioides only blooms for between 7 and 8 hours each year, alluding to the planet's short orbital period of 7.7 hours.[2]

    Properties

    Due to its close orbit, the exoplanet gets bombarded with radiation over 500 times more than Earth receives from the Sun.[3] Dayside temperatures on GJ 367b are around 1,728 K (1,455 °C; 2,651 °F).[4]

    Gliese 367 b is presumably tidally locked, and any atmosphere would have boiled away due to the planet's extreme temperatures. Observations from JWST provide evidence that the planet indeed lacks an atmosphere, and that its albedo is low.[4]

    The core of GJ 367b is likely composed of iron and nickel, making it similar to Mercury's core. The core of GJ 367b is extremely dense, making up about 91% of the planet's mass; the entire planet has a total density of 10.2±1.3 g/cm3, about twice that of Earth.[3] The planet may have been stripped of the outer silicate layers, like Mercury and other iron planets, due to collisions or evaporation by the extreme stellar radiation.[8]

    References

    1. 1 2 Lam, Kristine W. F.; Csizmadia, Szilárd; Astudillo-Defru, Nicola; Bonfils, Xavier; Gandolfi, Davide; Padovan, Sebastiano; Esposito, Massimiliano; Hellier, Coel; Hirano, Teruyuki; Livingston, John; Murgas, Felipe (2021-12-03). "GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star". Science. 374 (6572): 1271–1275. arXiv:2112.01309. Bibcode:2021Sci...374.1271L. doi:10.1126/science.aay3253. PMID 34855492. S2CID 244799656.
    2. 1 2 3 "2022 Approved Names". nameexoworlds.iau.org. IAU. Retrieved 7 June 2023.
    3. 1 2 3 4 Goffo, Elisa; Gandolfi, Davide; et al. (September 2023). "Company for the ultra-high density, ultra-short period sub-Earth GJ 367 b: discovery of two additional low-mass planets at 11.5 and 34 days". The Astrophysical Journal Letters. 955 (1): L3. arXiv:2307.09181. Bibcode:2023ApJ...955L...3G. doi:10.3847/2041-8213/ace0c7.
    4. 1 2 3 4 Zhang, Michael; Hu, Renyu; et al. (January 2024). "GJ 367b is a dark, hot, airless sub-Earth". The Astrophysical Journal Letters. arXiv:2401.01400.
    5. ↑ Witze, Alexandra (2021-12-02). "This tiny iron-rich world is extraordinarily metal". Nature. doi:10.1038/d41586-021-03587-z. PMID 34857947. S2CID 244846974.
    6. ↑ "Planetary Systems Composite Data". NASA Exoplanet Archive. Retrieved 7 December 2021.
    7. ↑ "List of ExoWorlds 2022". nameexoworlds.iau.org. IAU. 8 August 2022. Retrieved 27 August 2022.
    8. ↑ Hellier, Coel. "A new exoplanet: meet GJ 367b, an iron planet smaller and denser than Earth". The Conversation. Retrieved 2021-12-05.
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