Pi Andromedae

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Pi Andromedae
Diagram showing star positions and boundaries of the Andromeda constellation and its surroundings
Cercle rouge 100%.svg
Location of π Andromedae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 00h 36m 52.84926s[1]
Declination +33° 43′ 09.6384″[1]
Apparent magnitude (V) 4.36[2] (4.9/5.3)[3]
Spectral type B5 V[4] (B5 V + B5 V[3])
U−B color index –0.55[2]
B−V color index –0.16[2]
Radial velocity (Rv)+8.7[5] km/s
Proper motion (μ) RA: +14.75[1] mas/yr
Dec.: –3.51[1] mas/yr
Parallax (π)5.45 ± 0.31[1] mas
Distance600 ± 30 ly
(180 ± 10 pc)
Absolute magnitude (MV)−1.97[6]
Period (P)143.6 days
Eccentricity (e)0.56
Luminosity1,136[6] L
Surface gravity (log g)4.10[4] cgs
Temperature15,276[4] K
Metallicity [Fe/H]–0.20[4] dex
Rotational velocity (v sin i)25[7] km/s
Other designations
π Andromedae, 29 Andromedae, ADS 513, BD+32°101, FK5 18, HD 3369, HIP 2912, HR 154, SAO 54033.
Database references
π Andromedae in optical light

Pi Andromedae (Pi And, π Andromedae, π And) is the Bayer designation for a binary star[3] system in the northern constellation of Andromeda. With an apparent visual magnitude of 4.4,[2] it is visible to the naked eye. It is located approximately 600 light-years (180 parsecs) from Earth.

The pair is classified as a blue-white B-type main sequence dwarf, with an apparent magnitude of +4.34. It is a spectroscopic binary with an orbital period of 143.6 days and an eccentricity of 0.56. [3]

The spectroscopic binary forms a triple system with BD+32 102, a magnitude 8.6 star located 35.9 arcseconds away.[3] At 55 arcseconds separation is an 11th magnitude companion that is just located on the same line of sight, but at a much different distance from us.


In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of π Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, ε Andromedae, δ Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, π Andromedae itself is known as 奎宿六 (Kuí Sù liù, English: the Sixth Star of Legs.)[8]


  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:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. ^ a b c d e f Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x.
  4. ^ a b c d Cenarro, A. J.; et al. (January 2007), "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters", Monthly Notices of the Royal Astronomical Society, 374 (2): 664–690, arXiv:astro-ph/0611618, Bibcode:2007MNRAS.374..664C, doi:10.1111/j.1365-2966.2006.11196.x.
  5. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  6. ^ a b 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.
  7. ^ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  8. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日

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