Zeta Aurigae

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Zeta Aurigae
Diagram showing star positions and boundaries of the Auriga constellation and its surroundings
Cercle rouge 100%.svg

The location of ζ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension 05h 02m 28.68739s[1]
Declination +41° 04′ 33.0200″[1]
Apparent magnitude (V) 3.751[2]
Spectral type K5 Ib-II + B5–7 V[3][4]
U−B color index +0.374[2]
B−V color index +1.293[2]
R−I color index 0.87
Variable type Algol variable
Radial velocity (Rv) +12.8[5] km/s
Proper motion (μ) RA: +9.45[1] mas/yr
Dec.: -20.71[1] mas/yr
Parallax (π) 4.15 ± 0.29[1] mas
Distance 790 ± 50 ly
(240 ± 20 pc)
Period (P) 972.162 d
Semi-major axis (a) 905 R
Eccentricity (e) 0.3973 ± 0.0007
Inclination (i) 87.0°
Periastron epoch (T) Reduced JD 53039.9 ± 0.10
Argument of periastron (ω)
328.9° ± 0.13°
Semi-amplitude (K1)
23.17 ± 0.02 km/s
ζ Aur A
Mass 4.94 ± 0.79[6] M
Luminosity 3,254[6] L
Surface gravity (log g) 1.33[7] cgs
Temperature 3,920[7] K
Metallicity [Fe/H] –0.26[7] dex
Rotational velocity (v sin i) 68[8] km/s
ζ Aur B
Mass 4.8[3] M
Other designations
Hoedus I, Haedi Haedus, Sadatoni, Saclateni, 8 Aurigae, BD+40°1142, FK5 1137, HD 32068, HIP 23453, HR 1612, SAO 39966.[9]

Zeta Aurigae (ζ Aur, ζ Aurigae) is the Bayer designation for a binary star system in the northern constellation of Auriga. It has the traditional names Haedus and Sadatoni. Based upon parallax measurements made during the Hipparcos mission, this system is approximately 790 light-years (240 parsecs) distant from the Earth. It has a combined apparent visual magnitude of 3.75,[2] which is bright enough to be seen with the naked eye.

This is an eclipsing binary system with the orbital plane being oriented close to the line of sight from the Earth; the inclination of this system is estimated as 87.0°.[3] As a result, an eclipse of one star by the other occurs during each orbit, causing the magnitude to decrease to +3.99. The pair have an orbital period of 972 days (2.66 years) and an eccentricity of 0.4.[3] The primary component has been categorized as a K-type bright giant or supergiant star. Its companion is a B-type main sequence star of stellar classification B5 V or B7 V.[3][4]


It has the traditional names Haedus (also Hoedus) and Sadatoni (rarely Saclateni). It is one of the two hædi (kids) of the she-goat Capella, the other being Hoedus II, Eta Aurigae. The name Sadatoni is from the Arabic الساعد الثاني as-sācid aθ-θānī "the second arm (of the charioteer)". The rare traditional name Azaleh is shared (in the form Hassaleh) with Iota Aurigae.[citation needed]

In Chinese, (Zhù), meaning Pillars, refers to an asterism consisting of ζ Aurigae, ε Aurigae, η Aurigae, υ Aurigae, ν Aurigae, τ Aurigae, χ Aurigae and 26 Aurigae.[10] Consequently, ζ Aurigae itself is known as 柱二 (Zhù èr, English: the Second Star of Pillars.)[11]


  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 Kiyokawa, M. (1967), "Photoelectric Observation of Zeta Aurigae during the 1963-64 Eclipse", Publications of the Astronomical Society of Japan 19: 209, Bibcode:1967PASJ...19..209K. 
  3. ^ a b c d e f Eaton, Joel A.; Henry, Gregory W.; Odell, Andrew P. (June 2008), "Orbits and Pulsations of the Classical ζ Aurigae Binaries", The Astrophysical Journal 679 (2): 1490–1498, arXiv:0802.2238, Bibcode:2008ApJ...679.1490E, doi:10.1086/587452. 
  4. ^ a b Shenavrin, V. I.; Taranova, O. G.; Nadzhip, A. E. (January 2011), "Search for and study of hot circumstellar dust envelopes", Astronomy Reports 55 (1): 31–81, Bibcode:2011ARep...55...31S, doi:10.1134/S1063772911010070. 
  5. ^ Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W. 
  6. ^ a b Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355. 
  7. ^ a b c McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants" (PDF), Astrophysical Journal Supplement Series 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.  origin: STI
  8. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago 239 (1), Bibcode:1970CoAsi.239....1B. 
  9. ^ "zet Aur -- Eclipsing binary of Algol type (detached)", SIMBAD Astronomical Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-08-19. 
  10. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  11. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.

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