GJ 3929 b
Discovery[1]
Discovered byKemmer et al.[2]
Discovery date2022
Transit
Designations
Gliese 3929 b, TOI 2013 b, G 180-18 b[3]
Orbital characteristics[4]
0.0252±0.0005 AU
Eccentricity0 (fixed)
2.616 d
Inclination88.442°±0.008°
StarGJ 3929
Physical characteristics[4]
Mean radius
1.09±0.04 R🜨
Mass1.75+0.44
−0.45 M🜨
Mean density
7.3±2.0 g/cm3
Temperature568±6 K (295 °C)

    GJ 3929 b (Gliese 3929 b, TOI-2013 b) is an Earth-sized exoplanet orbiting the red dwarf GJ 3929.[3] It is located 51.6 light-years from Earth, in the constellation Corona Borealis,[3][5] and orbits its host star at a distance of 0.0252 astronomical units (3,770,000 km), completing one orbit every 2 days and 15 hours.[4] Because it orbits very close to its star, it is classified as a Venus-like planet.[4]

    Characteristics

    GJ 3929 b is classified as a Venus-like exoplanet, receiving a planetary insolation 17 times greater than what Earth receives from the Sun.[4] Its equilibrium temperature is calculated at 568 K (295 °C).[4]

    Orbit

    GJ 3929 b orbits its star at a distance of 0.0252 astronomical units (3,770,000 km), which makes it located in its host star's Venus zone, a region where rocky planets would have runaway greenhouse conditions like Venus.[4] GJ 3929 b completes an orbit around its star every 2 days, 14 hours and 47 minutes (2.616 days).[4]

    Size, mass and density

    Initially, the radius of GJ 3929 b was calculated at 1.15±0.04 R🜨, and its mass at 1.21±0.42 M🜨, giving a density of 4.4±1.6 g/cm3.[6] Later, observations using the NEID spectrometer on the WIYN 3.5 m Telescope measured the planet's mass to be 1.75±0.45 M🜨; and observations using the ARCTIC imager, plus photometry from TESS and LCOGT, constrained the planet's radius to 1.09±0.04 R🜨, this time giving a higher density of 7.3±2 g/cm3 (about 33% larger than Earth's[lower-alpha 1]).[4] The characteristics of this planet make it similar to Earth in terms of mass and radius.

    Atmosphere

    The high density of GJ 3929 b does not suggest a dense atmosphere.[4] Scenarios such as a thin atmosphere of volatiles, a thin atmosphere of silicate enriched in refractory elements, or even no atmosphere at all are plausible.[4] Due to its proximity to its star, GJ 3929 b has probably already lost much of its atmosphere.[4]

    GJ 3929 b is an excellent planet for atmospheric study with the James Webb Space Telescope.[4][6] The study of this planet's atmosphere can help reveal the evolutionary history of its planetary system, and provide more information about planetary formation models.[4]

    Discovery

    GJ 3929 b was discovered by a team of astronomers led by Jonas Kermer, from the Heidelberg University in Germany.[2] They reported a transit signal identified in the host star (GJ 3929)'s light curve detected by NASA's Transiting Exoplanet Survey Satellite (TESS).[2] Afterwards, the planetary nature of this transit signal was confirmed using radial velocity observations with the CARMENES spectrograph, in addition to transit observations made with SAINT-EX and LCOGT.[6][2] The discovery was announced in 2022.[1]

    The radial velocity observation with CARMENES also helped discover another planet in the planetary system, GJ 3929 c, a sub-Neptune detected by radial velocity.[6]

    Host star

    GJ 3929 b orbits GJ 3929, a red dwarf about 30% the radius of the Sun and 32% of its mass.[6]

    The star also hosts another planet, called GJ 3929 c, a sub-Neptune orbits 3 times further than the innermost planet, at a distance of 0.081 astronomical units (12,100,000 km),[6] but still below the habitable zone.[8]

    See also

    Notes and references

    1. 1 2 "GJ 3929 b". NASA Exoplanet Exploration. Retrieved January 4, 2023.
    2. 1 2 3 4 "Hot Earth-sized exoplanet detected with TESS". phys.org. Retrieved 2024-01-04.
    3. 1 2 3 "★ Gliese 3929". Stellar Catalog. Retrieved 2024-01-01.
    4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Beard, Corey; Robertson, Paul; Kanodia, Shubham; Lubin, Jack; Cañas, Caleb I.; Gupta, Arvind F.; Holcomb, Rae; Jones, Sinclaire; Libby-Roberts, Jessica E.; Lin, Andrea S. J.; Mahadevan, Suvrath; Stefánsson, Guðmundur; Bender, Chad F.; Blake, Cullen H.; Cochran, William D. (2022-09-01). "GJ 3929: High Precision Photometric and Doppler Characterization of an Exo-Venus and its Hot, Mini-Neptune-mass Companion". The Astrophysical Journal. 936 (1): 55. arXiv:2207.10672. Bibcode:2022ApJ...936...55B. doi:10.3847/1538-4357/ac8480. ISSN 0004-637X.
    5. ↑ "Find the constellation which contains given sky coordinates". djm.cc. Retrieved 2024-01-01.
    6. 1 2 3 4 5 6 Kemmer, J.; Dreizler, S.; Kossakowski, D.; Stock, S.; Quirrenbach, A.; Caballero, J. A.; Amado, P. J.; Collins, K. A.; Espinoza, N.; Herrero, E.; Jenkins, J. M.; Latham, D. W.; Lillo-Box, J.; Narita, N.; Pallé, E. (2022-03-01). "Discovery and mass measurement of the hot, transiting, Earth-sized planet, GJ 3929 b". Astronomy & Astrophysics. 659: A17. arXiv:2202.00970. Bibcode:2022A&A...659A..17K. doi:10.1051/0004-6361/202142653. ISSN 0004-6361.
    7. ↑ "Facts About Earth - NASA Science". science.nasa.gov. Retrieved 2023-12-04.
    8. ↑ "Open Exoplanet Catalogue - GJ 3929 b". www.openexoplanetcatalogue.com. Retrieved 2024-01-03.
      1. ↑ The density of Earth is 5.513 g/cm³.[7]
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