Rho Aurigae

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ρ Aurigae
Auriga constellation map.svg
Red circle.svg
Location of ρ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension  05h 21m 48.41650s[1]
Declination +41° 48′ 16.4615″[1]
Apparent magnitude (V) +5.22[2]
Spectral type B5 V[3]
U−B color index –0.57[2]
B−V color index –0.14[2]
Radial velocity (Rv)+13.1[4] km/s
Proper motion (μ) RA: +14.42[1] mas/yr
Dec.: –37.32[1] mas/yr
Parallax (π)6.16 ± 0.36[1] mas
Distance530 ± 30 ly
(162 ± 9 pc)
Period (P)34.49321 ± 0.00057 d
Eccentricity (e)0.104 ± 0.019
Periastron epoch (T)47962.5 ± 2.0 JD
Argument of periastron (ω)
3.4 ± 12.0°
Semi-amplitude (K1)
39.8 ± 0.8 km/s
ρ Aur A
Mass5–7[5] M
Radius3.2–3.4[6] R
Rotational velocity (v sin i)55[7] km/s
ρ Aur B
Mass2–4[5] M
Other designations
20 Aurigae, BD+41 1162, FK5 2400, HD 34759, HIP 25048, HR 1749, SAO 40269[8]
Database references

Rho Aurigae (ρ Aur, ρ Aurigae) is the Bayer designation for a binary star system in the northern constellation of Auriga. It is faintly visible to the naked eye with an apparent visual magnitude of +5.22.[2] Judging by parallax measurements, this system is approximately 530 light-years (160 parsecs) distant from the Earth, give or take a 30 light-year margin of error.[1]


ρ Aurigae is a single-lined spectroscopic binary system; the presence of a companion object is revealed by shifts in the stellar spectrum. The pair orbit each other with a period of 34.49 days and an orbital eccentricity of 0.10.[5]

The primary component of this system is a B-type main sequence star defined as a standard star for the stellar classification of B5 V;[3] the deduced mass of the secondary and the lack of evidence for it in the spectrum suggest it may be a B- or A-type star somewhat less luminous than the primary.[5]


Rho Aurigae, along with λ Aur and μ Aur, were Kazwini's Al Ḣibāʽ (ألحباع), the Tent.[9] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Ḣibāʽ were the title for three stars : λ Aur as Al Ḣibāʽ I, μ Aur as Al Ḣibāʽ II and σ Aur as Al Ḣibāʽ III.[10]

In Chinese, 咸池 (Xián Chí), meaning Pool of Harmony, refers to an asterism consisting of ρ Aurigae, λ Aurigae and HD 36041.[11] Consequently, the Chinese name for ρ Aurigae itself is 咸池一 (Xián Chí yī, English: the First Star of Pool of Harmony.)[12]


  1. ^ a b c d e f van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. VizieR catalogue entry I/311.
  2. ^ a b c d Crawford, D. L.; Barnes, J. V.; Golson, J. C. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere", The Astronomical Journal, 76: 1058, Bibcode:1971AJ.....76.1058C, doi:10.1086/111220.
  3. ^ a b Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333.
  4. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E.
  5. ^ a b c d e Horn, J.; et al. (May 1994), "The orbit of the spectroscopic binary ρ Aurigae", Astronomy and Astrophysics Supplement, 105: 119–124, Bibcode:1994A&AS..105..119H.
  6. ^ Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  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. ^ "rho Aur". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-20.
  9. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 91. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  10. ^ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), California Institute of Technology: Jet Propulsion Laboratory, retrieved 2012-08-19.
  11. ^ 陳久金 (2005). 中國星座神話 (in Chinese). 五南圖書出版股份有限公司. ISBN 978-986-7332-25-7.
  12. ^ "天文教育資訊網" [AEEA (Activities of Exhibition and Education in Astronomy)] (in Chinese). 2006-07-13. Retrieved 2018-10-06.

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