Astronomy:51 Eridani

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Short description: F-type main sequence star in the constellation Eridanus
51 Eridani
51 Eridani b orbit animated (2014-2018).gif
51 Eridani and its planet 51 Eridani b
Observation data
Equinox J2000.0]] (ICRS)
Constellation Eridanus
Right ascension  04h 37m 36.13234s[1]
Declination −02° 28′ 24.7749″[1]
Apparent magnitude (V) 5.22[2]
Characteristics
Spectral type F0 V[2]
Variable type γ Dor[3]
Astrometry
Radial velocity (Rv)12.60±0.3[4] km/s
Proper motion (μ) RA: 44.22 ± 0.34[1] mas/yr
Dec.: –64.39 ± 0.27[1] mas/yr
Parallax (π)33.98 ± 0.34[1] mas
Distance96.0 ± 1.0 ly
(29.4 ± 0.3 pc)
Absolute magnitude (MV)2.87[5]
Details[6]
51 Eri A
Mass1.75±0.05[2] M☉
Radius1.45±0.02 R☉
Luminosity6.7[7] L☉
Surface gravity (log g)3.95±0.04 cgs
Temperature7,331±30 K
Metallicity [Fe/H]−0.12±0.06 dex
Rotational velocity (v sin i)77.9[8] km/s
Other designations
Database references
SIMBADdata

51 Eridani is a star in the constellation Eridanus. It has an apparent magnitude of 5.22,[2] meaning it is just visible to the unaided eye in suburban and rural skies.[9] The primary star's absolute magnitude is 2.87.[5] There is also a binary star named GJ 3305 which shares the same proper motion through space with it,[10] making it overall a triple star system.

General information

Johann Bayer gave the star its Bayer designation of c Eridani,[11] using lowercase letters once he had exhausted all the letters of the Greek alphabet, in his 1603 star chart Uranometria.[12] It was catalogued as 51 Eridani by John Flamsteed in 1725.[13]

Located around 97 light-years distant, it shines with a luminosity approximately 5.38 times that of the Sun and has a surface temperature of 7,199 K.[14] A cold debris disk has been detected with a likely inner border of 82 astronomical units (AU).[15] A yellow-white main-sequence star of spectral type F0V, 51 Eridani is a member of the Beta Pictoris moving group and hence thought to be around 23 million years old.[5] Somewhat more luminous than it should be for its surface temperature, 51 Eridani has also been classified as spectral type F0IV—a type corresponding to ageing stars that have used up their core hydrogen fuel and become subgiants; however, in this case it is a phenomenon of very young stars 5 to 30 million years old that have yet to settle on the main sequence.[16]

Photometric measurements with the TESS space telescope show that this is a Gamma Doradus-like pulsating star. Nine pulsation frequencies have been detected.[3]

GJ 3305

51 Eridani has a companion, known as GJ 3305. The system has a common proper motion with 51 Eridani, and hence it is gravitationally bound, although it is separated by 66″ corresponding to 2,000 AU. It is a binary star system with two M-type red dwarfs. The primary has a mass of 0.67 ± 0.05 M☉ while the secondary has a mass of 0.44 ± 0.05 M☉. The two red dwarfs themselves are separated by a semimajor axis of 9.78 ± 0.14 AU and have an eccentricity of 0.19 ± 0.02.[10]

The star is significant as the host sun to one of the first planets to have been directly imaged in wide-orbit, and the first detected by the Gemini Planet Imager.[17]

Planetary system

51 Eridani b is a young Jupiter-like planet and was photographed, in near-infrared light, on 21 December 2014.[18] The study, led by Bruce Macintosh, a professor of physics at Stanford University and confirmed by Christian Marois found that methane and water were abundant in the atmosphere of the planet and its diameter was only slightly larger than Jupiter's.[17] It is the smallest exoplanet directly imaged to date.[19] The planetary orbit was found to be significantly eccentric by 2019.[20]

Gaia astrometry also suggests an additional planet on orbit smaller than 51 Eridani b.[20]

The planetary system[20]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(years) 		Eccentricity Inclination Radius
b 2.6±0.3 MJ 11.1+4.2−1.3 28.1+17.2−4.9 0.53+0.09−0.13 136+10−11° 1.11+0.16−0.13 RJ

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Simon, M.; Schaefer, G. H. (2011). "MEASURED DIAMETERS OF TWO F STARS IN THE β PIC MOVING GROUP". The Astrophysical Journal 743 (2): 158. doi:10.1088/0004-637X/743/2/158. Bibcode: 2011ApJ...743..158S. 
  3. ↑ 3.0 3.1 Sepulveda, Aldo G. et al. (October 2022), "The Directly Imaged Exoplanet Host Star 51 Eridani is a Gamma Doradus Pulsator", The Astrophysical Journal 938 (1): 49, doi:10.3847/1538-4357/ac9229, 49, Bibcode: 2022ApJ...938...49S. 
  4. ↑ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759–771. doi:10.1134/S1063773706110065. Bibcode: 2006AstL...32..759G. 
  5. ↑ 5.0 5.1 5.2 Mamajek, Eric E.; Bell, Cameron P. M. (2014). "On the age of the β Pictoris moving group". Monthly Notices of the Royal Astronomical Society 445 (3): 2169–80. doi:10.1093/mnras/stu1894. Bibcode: 2014MNRAS.445.2169M. 
  6. ↑ Rajan, Abhijith et al. (May 2017), "Characterizing 51 Eri b from 1 to 5μm: a partly-cloudy exoplanet", The Astronomical Journal 154 (1): 10, doi:10.3847/1538-3881/aa74db, Bibcode: 2017AJ....154...10R. 
  7. ↑ McCarthy, Kyle; White, Russel J. (June 2012), "The Sizes of the Nearest Young Stars", The Astronomical Journal 143 (6): 14, doi:10.1088/0004-6256/143/6/134, 134, Bibcode: 2012AJ....143..134M. 
  8. ↑ Paunzen, E. et al. (July 2014), "Investigating the possible connection between λ Bootis stars and intermediate Population II type stars", Astronomy & Astrophysics 567: 8, doi:10.1051/0004-6361/201423817, A67, Bibcode: 2014A&A...567A..67P. 
  9. ↑ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope (Sky Publishing Corporation). https://skyandtelescope.org/astronomy-resources/light-pollution-and-astronomy-the-bortle-dark-sky-scale. 
  10. ↑ 10.0 10.1 Montet, Benjamin T.; Bowler, Brendan P.; Shkolnik, Evgenya L.; Deck, Katherine M.; Wang, Ji; Horch, Elliott P.; Liu, Michael C.; Hillenbrand, Lynne A. et al. (2015). "Dynamical Masses of Young M Dwarfs: Masses and Orbital Parameters of Gj 3305 Ab, the Wide Binary Companion to the Imaged Exoplanet Host 51 Eri". The Astrophysical Journal 813 (1): L11. doi:10.1088/2041-8205/813/1/L11. Bibcode: 2015ApJ...813L..11M. 
  11. ↑ Wagman 2003, p. 144.
  12. ↑ Wagman 2003, pp. 6–7.
  13. ↑ Wagman 2003, p. 403.
  14. ↑ McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental Parameters and Infrared Excesses of Hipparcos Stars". Monthly Notices of the Royal Astronomical Society 427 (1): 343–57. doi:10.1111/j.1365-2966.2012.21873.x. Bibcode: 2012MNRAS.427..343M. 
  15. ↑ Riviere-Marichalar, P.; Barrado, D.; Montesinos, B.; Duchêne, G.; Bouy, H.; Pinte, C. et al. (2014). "Gas and dust in the beta Pictoris moving group as seen by the Herschel Space Observatory". Astronomy & Astrophysics 565: 11. doi:10.1051/0004-6361/201322901. A68. Bibcode: 2014A&A...565A..68R. 
  16. ↑ Pecaut, Mark J.; Mamajek, Eric E. (2013). "Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-main-sequence Stars". The Astrophysical Journal Supplement 208 (1): 22. doi:10.1088/0067-0049/208/1/9. Bibcode: 2013ApJS..208....9P. 
  17. ↑ 17.0 17.1 "Hot Jupiter-esque Discovery Hints at Planet Formation". W. M. Keck Observatory. Kamuela, Hawaii. 13 August 2015. http://www.keckobservatory.org/recent/entry/hot_jupiter_esque_discovery_hints_at_planet_formation. 
  18. ↑ Feltman, Rachel (August 13, 2015). "Newly discovered, Jupiter-like planet may sit in a solar system much like our own". The Washington Post. https://www.washingtonpost.com/news/speaking-of-science/wp/2015/08/13/newly-discovered-jupiter-like-planet-may-sit-in-a-solar-system-much-like-our-own/. 
  19. ↑ Gary, Stuart (14 August 2015). "Small alien world most Jupiter-like planet ever seen". ABC Science. ABC. https://www.abc.net.au/science/articles/2015/08/14/4292819.htm. 
  20. ↑ 20.0 20.1 20.2 Rosa, Robert J. De et al. (2019), "An Updated Visual Orbit of the Directly Imaged Exoplanet 51 Eridani b and Prospects for a Dynamical Mass Measurement with Gaia", The Astronomical Journal 159: 1, doi:10.3847/1538-3881/ab4da4 
Cited text
  • Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, Virginia: The McDonald & Woodward Publishing Company. ISBN 978-0-939923-78-6. 



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