p Eridani

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p Eridani AB
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Eridanus
Right ascension 01h 39m 47.53953s[1]
Declination −56° 11′ 47.0997″[1]
Apparent magnitude (V) 5.87 + 5.76[2]
Spectral type K2V + K2V[3]
U−B color index +0.59 / +0.53[2]
B−V color index +0.90 / +0.87[2]
Radial velocity (Rv) +19.5 km/s
Proper motion (μ) RA: 282.16[1] mas/yr
Dec.: 10.56[1] mas/yr
Parallax (π) 127.84 ± 2.19[1] mas
Distance 25.5 ± 0.4 ly
(7.8 ± 0.1 pc)
Absolute magnitude (MV) 6.25 / 6.27[4]
Companion p Eridani B
Period (P) 483.66 yr
Semi-major axis (a) 7.817″
Eccentricity (e) 0.5344
Inclination (i) 142.824°
Longitude of the node (Ω) 13.116°
Periastron epoch (T) 1813.494
Metallicity [Fe/H] –0.23[5] dex
Rotation 30 days[5]
Age 4.8[6] Gyr
Other designations
Gliese 66, CD−56°328, GCTP 352.00, SAO 232490, WDS 01398-5612, DUN 5, HIP 7751
6 Eri A: HR 486, HD 10360, LTT 903
6 Eri B: HR 487, HD 10361, LTT 902
Database references

p Eridani (6 Eri, DUN 5) is a binary star system in the constellation of Eridanus (the River) whose distance is approximately 26 light-years. It was found to be a double star in December 1825 by James Dunlop in Australia at his home at Paramatta, now spelt Parramatta.


The name "p Eridani", according to Nature, p. 589 (19 April 1883)[7] has been:

"... occasionally miscalled 6 Eridani, which would imply that it was one of Flamsteed's stars. Flamsteed, it is true has a star which he calls 6 Eridani. The designated letter 'p' was attached to a star by Lacaille in the catalogue at the end of his Coelum Australe Stelliferum. The number '6' is merely borrowed from Bode."

The use of Bode numbers was commonly used in the early 19th century, but this antiquated system has now fallen into disuse for more than a century.

See also[edit]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c Hoffleit, D.; Jaschek, C. (1991). The Bright star catalogue. New Haven: Yale University Observatory. Bibcode:1991bsc..book.....H. 
  3. ^ Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132: 161. arXiv:astro-ph/0603770Freely accessible. Bibcode:2006AJ....132..161G. doi:10.1086/504637. 
  4. ^ Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982Freely accessible, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191. 
  5. ^ a b Maldonado, J.; et al. (October 2010), "A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups", Astronomy and Astrophysics, 521: A12, arXiv:1007.1132Freely accessible, Bibcode:2010A&A...521A..12M, doi:10.1051/0004-6361/201014948 
  6. ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal, 687 (2): 1264–1293, arXiv:0807.1686Freely accessible, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785 
  7. ^ Our Astronomical Column, Nature, p.589, 19 April 1883
  • William I. Hartkopf & Brian D. Mason, "Sixth Catalog of Orbits of Visual Binary Stars", U.S. Naval Observatory, 2001.
  • J. Dunlop; "Approximate Places of Double Stars in the Southern Hemisphere, observed at Paramatta in New South Wales." Mem.Ast.Soc.. London, 3, 257; (1828)

External links[edit]