p Eridani

p Eridani is a binary star system in the constellation of Eridanus (the River) whose distance from the Sun is approximately 26 light-years based upon parallax.[1] It was found to be a double star in December 1825 by James Dunlop in Australia at his home at Paramatta, now spelt Parramatta. It is visible to the naked eye as a dim, orange-hued star. The system is moving further from the Earth with a heliocentric radial velocity of +23 km/s.[4]

P Eridani
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]
Characteristics
Spectral type K2V + K2V[3]
U−B color index +0.59 / +0.53[2]
B−V color index +0.90 / +0.87[2]
Astrometry
Radial velocity (Rv)+23.48±0.17[4] 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
Distance25.5 ± 0.4 ly
(7.8 ± 0.1 pc)
Absolute magnitude (MV)6.25 / 6.27[5]
Orbit[6]
Period (P)475.2 yr
Semi-major axis (a)7.826″
Eccentricity (e)0.5344
Inclination (i)140.5°
Longitude of the node (Ω)13.7°
Periastron epoch (T)1811.90
Argument of periastron (ω)
(secondary)		18.6°
Details
p Eri A
Luminosity0.339[7] L☉
Surface gravity (log g)4.62[7] cgs
Temperature5,019[7] K
Metallicity [Fe/H]–0.23[8] dex
Rotation30 days[8]
Age4.8[9] Gyr
Other designations
DUN 5, p Eri, 6 Eri, CD−56°328, GJ 66, HIP 7751, SAO 232490, WDS 01398-5612
6 Eri A: HD 10360, HR 486, LTT 903
6 Eri B: HD 10361, HR 487, LTT 902
Database references
SIMBADdata

This system consists of a pair of K-type main-sequence stars with stellar classifications of K2V[3] Component A has visual magnitude 5.87, while component B is magnitude 5.76.[2] They orbit each other with a period of 475.2 years, an eccentricity of 0.53, and a semimajor axis of 7.8″.[6]

Naming

The name "p Eridani", according to Nature, p. 589 (19 April 1883)[10] 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

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. Hoffleit, D.; Jaschek, C. (1991), The Bright star catalogue, New Haven: Yale University Observatory, Bibcode:1991bsc..book.....H.
  3. Gray, R. O.; et al. (2006), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637.
  4. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  5. 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:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191.
  6. Hartkopf, W. I.; et al. (June 30, 2006), Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory, retrieved 2017-06-02.
  7. Hinkel, Natalie R.; et al. (October 2017), "A Catalog of Stellar Unified Properties (CATSUP) for 951 FGK-Stars within 30 pc", The Astrophysical Journal, 848 (1): 19, arXiv:1709.04465, Bibcode:2017ApJ...848...34H, doi:10.3847/1538-4357/aa8b0f, 34.
  8. 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:1007.1132, Bibcode:2010A&A...521A..12M, doi:10.1051/0004-6361/201014948.
  9. 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:0807.1686, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785.
  10. "Our Astronomical Column: The Binary Star p Eridani" (PDF), Nature: 589, 19 April 1883, retrieved 2019-05-27.
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