Upsilon Aurigae

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

The location of υ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension 05h 51m 02.43724s[1]
Declination +37° 18′ 20.0565″[1]
Apparent magnitude (V) 4.74[2]
Spectral type M0 III[3]
U−B color index +1.93[2]
B−V color index +1.62[2]
R−I color index 1.07
Radial velocity (Rv) +37.68[4] km/s
Proper motion (μ) RA: +36.85[1] mas/yr
Dec.: -45.52[1] mas/yr
Parallax (π) 6.24 ± 0.65[1] mas
Distance approx. 520 ly
(approx. 160 pc)
Radius 73[5] R
Luminosity 937[6] L
Surface gravity (log g) 1.16+0.04
[7] cgs
Temperature 3,800[7] K
Other designations
31 Aurigae, BD+37 1336, FK5 2440, HD 38944, HIP 27639, HR 2011, SAO 58496.[8]
Database references

Upsilon Aurigae (υ Aur, υ Aurigae) is the Bayer designation for a star in the northern constellation of Auriga. It has an apparent visual magnitude of 4.74,[2] which means it is bright enough to be seen with the naked eye. Based upon parallax measurements made during the Hipparcos mission, this star is approximately 520 light-years (160 parsecs) distant from the Earth.

This is an evolved red giant star with a stellar classification of M0 III.[3] It is a suspected variable star[9] and is currently on the asymptotic giant branch, which means it is generating energy at its core through the fusion of helium.[10] The measured angular diameter of this star, after correction for limb darkening, is 4.24 ± 0.05 mas.[11] At the estimated distance of Upsilon Aurigae,[1] this yields a physical size of about 73 times the radius of the Sun.[5]


  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:0708.1752v1Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.  Note: see VizieR catalogue I/311.
  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): 99, Bibcode:1966CoLPL...4...99J 
  3. ^ a b Keenan, Philip C.; Barnbaum, Cecilia (June 1999), "Revision and Calibration of MK Luminosity Classes for Cool Giants by HIPPARCOS Parallaxes", The Astrophysical Journal, 518 (2): 859–865, Bibcode:1999ApJ...518..859K, doi:10.1086/307311. 
  4. ^ Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579Freely accessible, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272. 
  5. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1 . The radius (R*) is given by:
  6. ^ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037Freely accessible, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x. 
  7. ^ a b Takagi, Yuhei; et al. (June 2011), "Age Determinations of Early-M Type Pre-Main Sequence Stars Using a High-Resolution Near-Infrared Spectroscopic Method", Publications of the Astronomical Society of Japan, 63 (3): 677−684, Bibcode:2011PASJ...63..677T, doi:10.1093/pasj/63.3.677. 
  8. ^ "ups Aur -- Variable Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-08-23. 
  9. ^ Hamada, K.; et al. (January 1979), "On the Variability of upsilon Aurigae", Information Bulletin on Variable Stars, 1531: 1, Bibcode:1979IBVS.1531....1H. 
  10. ^ Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun", Astronomical Journal, 104 (1): 275–313, Bibcode:1992AJ....104..275E, doi:10.1086/116239. 
  11. ^ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039. 

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