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υ Aurigae
	Location of υ Aurigae (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Auriga
Right ascension	05h 51m 02.43804s
Declination	+37° 18′ 20.0581″
Apparent magnitude (V)	4.74
Characteristics
Evolutionary stage	Asymptotic giant branch
Spectral type	M0 III
U−B color index	+1.93
B−V color index	+1.62
R−I color index	1.07
Variable type	Suspected
Astrometry
Radial velocity (Rv)	+37.68 km/s
Proper motion (μ)	RA: +35.914 mas/yr ; Dec.: −46.100 mas/yr
Parallax (π)	6.5040 ± 0.3305 mas
Distance	500 ± 30 ly ; (154 ± 8 pc)
Absolute magnitude (MV)	−1.28
Details
Mass	1.64±0.22 M☉
Radius	74.2+8.7; −7.0 R☉
Luminosity	1,165±250 L☉
Surface gravity (log g)	1.16+0.04; −0.08 cgs
Temperature	3,912±52 K
Age	1.98±0.68 Gyr
Other designations
	υ Aur, 31 Aurigae, NSV 2661, BD+37 1336, FK5 2440, HD 38944, HIP 27639, HR 2011, SAO 58496
Database references
SIMBAD	data

Upsilon Aurigae, Latinised from υ Aurigae, is the Bayer designation for a single^[11] 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, this star is approximately 500 light-years (150 parsecs) distant from the Earth. It is drifting further away with a radial velocity of +38 km/s.^[6]

This is an evolved red giant star with a stellar classification of M0 III.^[4] It is a suspected variable star^[5] and is currently on the asymptotic giant branch, which means it is generating energy through the fusion of helium along a shell surrounding a small, inert core of carbon and oxygen.^[3] The star is two billion years old with 1.64 times the mass of the Sun and has expanded to 61 times the Sun's radius. It is radiating 1,165 times the Sun's luminosity from its photosphere at an effective temperature of 3,912 K.^[8]

References

^ ^a ^b ^c ^d ^e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^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
^ ^a ^b 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.
^ ^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, S2CID 121902473.
^ ^a ^b Hamada, K.; et al. (January 1979), "On the Variability of upsilon Aurigae", Information Bulletin on Variable Stars, 1531: 1, Bibcode:1979IBVS.1531....1H.
^ ^a ^b 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/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
^ 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, S2CID 119257644.
^ ^a ^b Baines, E.; et al. (2017), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal, 155 (1): 30, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b, S2CID 119427037.
^ 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.
^ "* ups Aur". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-23.
^ 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, S2CID 14878976.