Astronomy:Gliese 3470 b

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Short description: Mini-Neptune orbiting Gliese 3470
Gliese 3470 b
GJ3470b.jpg
Size comparison of Gliese 3470 b with Earth.
Discovery
Discovered byX. Bonfils et al.[1]
Discovery date2012
Radial velocity
Orbital characteristics
0.031±0.0028 AU
Eccentricity0.114±0.052[2]
Orbital period3.3366487+0.0000043
−0.0000033 d
Inclination88.88+0.62
−0.45
StarGliese 3470
Physical characteristics
Mean radius4.19±0.58 R⊕
Mass12.57±1.3[3] M⊕
Mean density1.18±0.33 g cm−3
Physics604±98


Gliese 3470 b, abbreviated as GJ 3470b, is an exoplanet orbiting the star Gliese 3470, located in the constellation Cancer. With a mass of just under 14 Earth-masses and a radius approximately 4.3 times that of Earth's, it is likely something akin to a mini-Neptune despite the initially strong belief that the planet was not covered in clouds like the gas giants in the Solar System.

The orbit of Gliese 3470 b is strongly inclined to the equatorial plane of the parent star, with misalignment equal to 97+16−11°.[4]

In August 2022, this planet and its host star were included among 20 systems to be named by the third NameExoWorlds project.[5]

Atmosphere

The atmosphere of Gliese 3470 b is one of the best spectroscopically characterized among all exoplanets.

The exoplanet's atmosphere was first observed by researchers Akihiko Fukui, Norio Narita and Kenji Kuroda at the University of Tokyo in 2013, and afterwards, Fukui commented, "Suppose the atmosphere consists of hydrogen and helium, the mass of the atmosphere would be 5–20% of the total mass of the planet. Comparing that to the fact that the mass of Earth's atmosphere is about one ten-thousandth of a percent (0.0001%) of the total mass of the Earth, this planet has a considerably thick atmosphere."[6] In 2013, by means of Large Binocular Telescope observations, with the LBC Blue and Red cameras, a team reported the detection of Rayleigh scattering in the atmosphere of this planet.[7] In 2015 a team using the Las Cumbres Observatory Global Telescope (LCOGT) network confirmed this finding. In the Las Cumbres researchers' paper published in The Astrophysical Journal, they conclude that the most plausible explanation for the scattering effect to be an atmosphere made predominantly of hydrogen and helium, causing the exoplanet to be veiled by dense clouds and hazes.[8] It is thought that the planet would appear blue to the human eye due to this scattering.

In 2017–2019, the primary hydrogen atmosphere with overall low metallicity, depleted methane and traces of water was characterized.[9][10] It is likely filling an entire Roche lobe of the planet.[11] In 2019 and 2020, a metastable helium outflow was detected in the atmosphere of Gliese 3470 b, indicating the atmosphere is currently escaping at rate 30,000-100,000 tons per second, or 0.16-0.53 Earth masses per billion years.[12][13]

Gallery

  • Structure of Exoplanet GJ 3470 b.[14]

  • Artist's impression of gas streaming from GJ 3470b.[15]

Size comparison
Earth GJ 3470b
Small Earth.jpg Exoplanet

See also

References

  1. ↑ Bonfils, Xavier; Gillon, Michaël; Udry, Stéphane; Armstrong, David; Bouchy, François; Delfosse, Xavier; Forveille, Thierry; Fumel, Aurélie et al. (2012). "A hot Uranus transiting the nearby M dwarf GJ3470. Detected with HARPS velocimetry. Captured in transit with TRAPPIST photometry". Astronomy & Astrophysics 546: A27. doi:10.1051/0004-6361/201219623. Bibcode: 2012A&A...546A..27B. http://orbi.ulg.ac.be/jspui/handle/2268/135085. [yes|permanent dead link|dead link}}]
  2. ↑ exoplanet.eu Planet GJ 3470 b
  3. ↑ "GJ 3470 B". http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=GJ+3470+b&type=PLANET+HOST. 
  4. ↑ Stefànsson, Guđmundur et al. (2022). "The Warm Neptune GJ 3470b Has a Polar Orbit". The Astrophysical Journal Letters 931 (2): L15. doi:10.3847/2041-8213/ac6e3c. Bibcode: 2022ApJ...931L..15S. 
  5. ↑ "List of ExoWorlds 2022". IAU. 8 August 2022. https://www.nameexoworlds.iau.org/2022exoworlds. 
  6. ↑ Fukui, Akihiko et al. (2013). "Optical-to-Near-Infrared Simultaneous Observations for the Hot Uranus GJ3470b: A Hint for Cloud-free Atmosphere". The Astrophysical Journal 770 (2): 95. doi:10.1088/0004-637X/770/2/95. Bibcode: 2013ApJ...770...95F. 
  7. ↑ Nascimbeni, Valerio; Piotto, Giampaolo; Pagano, Isabella; Scandariato, Gaetano; Sani, Eleonora; Fumana, M. (2013). "The blue sky of GJ3470b: the atmosphere of a low-mass planet unveiled by ground-based photometry". Astronomy and Astrophysics 559: A32. doi:10.1051/0004-6361/201321971. Bibcode: 2013A&A...559A..32N. 
  8. ↑ Dragomir, Diana et al. (2015). "Rayleigh Scattering in the Atmosphere of the Warm Exo-Neptune GJ 3470b". The Astrophysical Journal 814 (2): 9. doi:10.1088/0004-637X/814/2/102. Bibcode: 2015ApJ...814..102D. 
  9. ↑ Chen, G.; Guenther, E. W.; Pallé, E.; Nortmann, L.; Nowak, G.; Kunz, S.; Parviainen, H.; Murgas, F. (2017). "The GTC exoplanet transit spectroscopy survey". Astronomy & Astrophysics 600: A138. doi:10.1051/0004-6361/201630228. 
  10. ↑ Benneke, Björn; Knutson, Heather A.; Lothringer, Joshua; Crossfield, Ian J.M.; Moses, Julianne I.; Morley, Caroline; Kreidberg, Laura; Fulton, Benjamin J. et al. (2019). "A sub-Neptune exoplanet with a low-metallicity methane-depleted atmosphere and Mie-scattering clouds". Nature Astronomy 3 (9): 813–821. doi:10.1038/s41550-019-0800-5. Bibcode: 2019NatAs...3..813B. 
  11. ↑ Bourrier, V.; Lecavelier Des Etangs, A.; Ehrenreich, D.; Sanz-Forcada, J.; Allart, R.; Ballester, G. E.; Buchhave, L. A.; Cohen, O. et al. (2018). "Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470b". Astronomy & Astrophysics 620: A147. doi:10.1051/0004-6361/201833675. Bibcode: 2018A&A...620A.147B. 
  12. ↑ Pallé, E.; Nortmann, L.; Casasayas-Barris, N.; Lampón, M.; López-Puertas, M.; Caballero, J. A.; Sanz-Forcada, J.; Lara, L. M. et al. (2020). "A He I upper atmosphere around the warm Neptune GJ 3470 B". Astronomy & Astrophysics 638: A61. doi:10.1051/0004-6361/202037719. 
  13. ↑ Ninan, Joe P.; Stefansson, Gudmundur; Mahadevan, Suvrath; Bender, Chad; Robertson, Paul; Ramsey, Lawrence; Terrien, Ryan; Wright, Jason et al. (2019). "Evidence for He i 10830 Å Absorption during the Transit of a Warm Neptune around the M-dwarf GJ 3470 with the Habitable-zone Planet Finder". The Astrophysical Journal 894 (2): 97. doi:10.3847/1538-4357/ab8559. 
  14. ↑ "Structure of Exoplanet GJ 3470 b" (in en). https://www.spacetelescope.org/images/opo1938a/. Retrieved 5 July 2019. 
  15. ↑ "Artist's impression of gas streaming from GJ 3470b" (in en). https://spacetelescope.org/images/opo1852a/. Retrieved 17 December 2018. 




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