Beta Aurigae

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

The location of β Aurigae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Auriga
Right ascension 05h 59m 31.72293s[1]
Declination +44° 56′ 50.7573″[1]
Apparent magnitude (V) +1.90[2]
Spectral type A1m IV + A1m IV[3]
U−B color index +0.05[2]
B−V color index +0.03[2]
R−I color index –0.01
Variable type Algol variable
Radial velocity (Rv) –18.2[4] km/s
Proper motion (μ) RA: –56.44[1] mas/yr
Dec.: –0.95[1] mas/yr
Parallax (π) 40.21 ± 0.23[1] mas
Distance 81.1 ± 0.5 ly
(24.9 ± 0.1 pc)
Absolute magnitude (MV) 0.55/0.76[5]
Period (P) 3.96004 days
Eccentricity (e) 0.0
Inclination (i) 76.0 ± 0.4°
Periastron epoch (T) 54539.0162 ± 0.0003 reduced HJD
Semi-amplitude (K1)
108.053 ± 0.072 km/s
Semi-amplitude (K2)
110.911 ± 0.071 km/s
β Aur A
Mass 2.389 ± 0.013[6] M
Radius 2.77[7] R
Luminosity 48[8] L
Surface gravity (log g) 3.93[5] cgs
Temperature 9,350[7] K
Rotational velocity (v sin i) 33[7] km/s
Age 570[7] Myr
β Aur B
Mass 2.327 ± 0.013[6] M
Radius 2.63[7] R
Luminosity 48[8] L
Temperature 9,200[7] K
Rotational velocity (v sin i) 34[7] km/s
Other designations
Menkalinan, 34 Aurigae, ADS 4556, BD+44 1328, FK5 227, HD 40183, HIP 28360, HR 2088, SAO 40750.[9]

Beta Aurigae (β Aur, β Aurigae) is the Bayer designation for a binary star[10] system in the northern constellation of Auriga. It has the traditional name Menkalinan, which is shortened from the Arabic منكب ذي العنان mankib ðī-l-‘inān "shoulder of the rein-holder". It is known as 五車三 (the Third Star of the Five Chariots) in traditional Chinese astronomy. The combined apparent visual magnitude of the system is 1.9,[2] making it the second brightest member of the constellation after Capella. Using the parallax measurements made during the Hipparcos mission, the distance to this star system can be estimated as 81.1 light-years (24.9 parsecs), give or take a half light year margin of error.[1]


Beta Aurigae is a binary star system, although the light that the star system releases forges the appearance of a single star in the night sky. The two brightest components are metallic-lined subgiant stars belonging to the A-type stellar classification;[3] they have roughly the same mass and radius. A-type entities are hot stars that release a blue-white hued light; these two stars burn brighter and with more heat than the Sun, which is a G2-type main sequence star. The pair constitute an eclipsing spectroscopic binary; the combined apparent magnitude varies over a period of 3.96 days between +1.89 and +1.94, as every 47.5 hours one of the stars partially eclipses the other from Earth's perspective.[11]

At an angular separation of 13.9 ± 0.3 arcseconds along a position angle of 155° is a companion star that is 8.5 magnitudes fainter than the binary pair. This is a candidate member of Beta Aurigae, which would make it a triple (trinary) star system. It may be the source of the X-ray emission from the vicinity.[12] The Beta Aurigae system is believed to be a stream member of the Ursa Major Moving Group.[13]

See also[edit]


  1. ^ a b c d e f 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 Southworth, J.; Bruntt, H.; Buzasi, D. L. (June 2007), "Eclipsing binaries observed with the WIRE satellite. II. β Aurigae and non-linear limb darkening in light curves", Astronomy and Astrophysics 467 (3): 1215–1226, arXiv:astro-ph/0703634, Bibcode:2007A&A...467.1215S, doi:10.1051/0004-6361:20077184. 
  4. ^ Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington D.C., Bibcode:1953GCRV..C......0W 
  5. ^ a b Torres, G.; Andersen, J.; Giménez, A. (February 2010), "Accurate masses and radii of normal stars: modern results and applications", The Astronomy and Astrophysics Review 18 (1-2): 67–126, arXiv:0908.2624, Bibcode:2010A&ARv..18...67T, doi:10.1007/s00159-009-0025-1 
  6. ^ a b c Behr, Bradford B. et al. (July 2011), "Stellar Astrophysics with a Dispersed Fourier Transform Spectrograph. II. Orbits of Double-lined Spectroscopic Binaries", The Astronomical Journal 142 (1): 6, arXiv:1104.1447, Bibcode:2011AJ....142....6B, doi:10.1088/0004-6256/142/1/6 
  7. ^ a b c d e f g Nordstrom, B.; Johansen, K. T. (1994), "Radii and masses for beta Aurigae", Astronomy and Astrophysics 291 (3): 777–785, Bibcode:1994A&A...291..777N 
  8. ^ a b Kaler, James B., "MENKALINAN (Beta Aurigae)", Stars (University of Illinois), retrieved 2010-01-23 
  9. ^ "NLTT 8982 -- High proper-motion Star", SIMBAD Astronomical Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-07-18. 
  10. ^ 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. 
  11. ^ Malkov, O. Yu.; Oblak, E.; Snegireva, E. A.; Torra, J. (February 2006), "A catalogue of eclipsing variables", Astronomy and Astrophysics 446 (2): 785–789, Bibcode:2006A&A...446..785M, doi:10.1051/0004-6361:20053137. 
  12. ^ De Rosa, R. J. et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society 415 (1): 854–866, arXiv:1103.4363, Bibcode:2011MNRAS.415..854D, doi:10.1111/j.1365-2966.2011.18765.x 
  13. ^ Giannuzzi, M. A. (August 1979), "On the eclipsing binaries of the Ursa Major stream", Astronomy and Astrophysics 77 (1-2): 214–222, Bibcode:1979A&A....77..214G. 

External links[edit]