Sigma Aurigae

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σ Aurigae
Auriga constellation map.svg
Red circle.svg
Location of σ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension  05h 24m 39.14261s[1]
Declination +37° 23′ 07.2494″[1]
Apparent magnitude (V) 4.99[2]
Spectral type K4 III[3]
U−B color index +1.75[2]
B−V color index +1.42[2]
R−I color index 0.53
Radial velocity (Rv)–19.7[4] km/s
Proper motion (μ) RA: +0.71[1] mas/yr
Dec.: –11.51[1] mas/yr
Parallax (π)6.2101 ± 0.2221[5] mas
Distance530 ± 20 ly
(161 ± 6 pc)
Absolute magnitude (MV)−0.75[6]
Luminosity431[6] L
Surface gravity (log g)1.75[7] cgs
Temperature4,080[7] K
Metallicity [Fe/H]–0.03[7] dex
Rotational velocity (v sin i)10[8] km/s
Other designations
σ Aur, 21 Aurigae, BD+37°1175, HD 35186, HIP 25292, HR 1773, SAO 57981.[9]
Database references

Sigma Aurigae, Latinized from σ Aurigae, is a giant star in the northern constellation of Auriga. It is faintly visible to the naked eye with an apparent visual magnitude of 4.99.[2] With an annual parallax shift of 6.21 mas,[1] it is approximately 530 light-years (160 parsecs) distant from the Earth. This is an evolved giant star with a stellar classification of K4 III.[3]

Sigma Aurigae has a 12th magnitude companion at an angular separation of 8 arcseconds, as well as two fainter companions at 28 and 35" respectively.[10] All are background objects, stars much further away than Sigma itself.


  1. ^ a b c d e 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. Note: see VizieR catalogue I/311.
  2. ^ a b c d Argue, A. N. (1966), "UBV photometry of 550 F, G and K type stars", Monthly Notices of the Royal Astronomical Society, 133 (4): 475–493, Bibcode:1966MNRAS.133..475A, doi:10.1093/mnras/133.4.475.
  3. ^ a b Roman, Nancy G. (July 1952), "The Spectra of the Bright Stars of Types F5-K5", Astrophysical Journal, 116: 122, Bibcode:1952ApJ...116..122R, doi:10.1086/145598.
  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/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272.
  5. ^ 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.
  6. ^ a b 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.
  7. ^ a b c McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
  8. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B.
  9. ^ "sig Aur -- Star in double system", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-08-22.
  10. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I; the Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M.

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