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σ Arietis
	Location of σ Arietis (circled)
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Aries
Right ascension	02h 51m 29.58618s
Declination	+15° 04′ 55.4438″
Apparent magnitude (V)	+5.52
Characteristics
Spectral type	B7 V
U−B color index	–0.43
B−V color index	–0.09
Astrometry
Radial velocity (Rv)	+17.0 km/s
Proper motion (μ)	RA: +29.843 mas/yr ; Dec.: –24.661 mas/yr
Parallax (π)	6.8952 ± 0.2164 mas
Distance	470 ± 10 ly ; (145 ± 5 pc)
Absolute magnitude (MV)	−0.38
Details
A
Mass	3.84±0.08 M☉
Radius	3 R☉
Luminosity	301 L☉
Surface gravity (log g)	4.0±0.25 cgs
Temperature	13,121 K
Rotational velocity (v sin i)	165 km/s
Age	36+57; −27 Myr
B
Mass	1.0–1.2 M☉
Temperature	5,524±150 K
Metallicity [Fe/H]	−0.5 dex
Rotational velocity (v sin i)	5 km/s
Other designations
	σ Ari, 43 Arietis, BD+14 480, FK5 1079, HD 17769, HIP 13327, HR 847, SAO 93144
Database references
SIMBAD	data

Sigma Arietis, Latinized from σ Arietis, is the Bayer designation for a star in the northern constellation of Aries. It has an apparent visual magnitude of +5.52,^[2] which is bright enough for the star to be seen with the naked eye from dark suburban skies. The star is located at a distance of approximately 470 light-years (140 parsecs) from the Sun based on parallax, and is drifting further away with a radial velocity of +17 km/s.^[4] On November 20, 1952, it was observed being occulted by the planet Jupiter.^[10]

Sigma Arietis is a B-type main sequence star with a stellar classification of B7 V.^[3] This is a large star with three^[7] times the radius of the Sun and 3.8^[6] times the Sun's mass. It shines around 301^[6] times as brightly as the helium and oxeygen, with this energy being radiated into space from its outer atmosphere at a scorching hot effective temperature of 13,121 K.^[6] It is this heat that gives the star the blue-white hue of a B-type star. Sigma Arietis is spinning at a rapid clip, with a projected rotational velocity of 165 km/s.^[6] It is a probable member of the Cas-Tau OB association of stars that share a common motion through space.^[11]

In 2016, a stellar companion was reported based on observations using adaptive optics with the Gemini North Telescope.^[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 Crawford, D. L.; Barnes, J. V.; Golson, J. C. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere", The Astronomical Journal, 76: 1058, Bibcode:1971AJ.....76.1058C, doi:10.1086/111220.
^ ^a ^b Lesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?", Astrophysical Journal Supplement, 17: 371, Bibcode:1968ApJS...17..371L, doi:10.1086/190179.
^ ^a ^b Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W.
^ 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 ^c ^d ^e ^f ^g ^h Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
^ ^a ^b Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 5211–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754
^ ^a ^b ^c ^d ^e ^f Gullikson, Kevin; et al. (August 2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal, 152 (2): 13, arXiv:1604.06456, Bibcode:2016AJ....152...40G, doi:10.3847/0004-6256/152/2/40, S2CID 119179065, 40.
^ "sig Ari". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-18.{{cite web}}: CS1 maint: postscript (link)
^ Salanave, Leon E. (February 1953), "Occultation of Sigma ARIETIS by Jupiter", Publications of the Astronomical Society of the Pacific, 65 (382): 48, Bibcode:1953PASP...65...48S, doi:10.1086/126529, S2CID 121458925.
^ de Zeeuw, P. T.; et al. (January 1999), "A HIPPARCOS Census of the Nearby OB Associations", The Astronomical Journal, 117 (1): 354–399, arXiv:astro-ph/9809227, Bibcode:1999AJ....117..354D, doi:10.1086/300682, S2CID 16098861.