Sigma Arietis

Sigma Arietis is a star in the northern constellation of Aries. Its name is a Bayer designation that is Latinized from σ Arietis, and abbreviated Sigma Ari or σ Ari. This star has an apparent visual magnitude of +5.52,^[3] 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 463 light-years (142 parsecs) from the Sun based on parallax measurements, and is drifting further away with a radial velocity of +17 km/s.^[5] On November 20, 1952, it was observed being occulted by the planet Jupiter.^[10]

σ Arietis

Location of σ Arietis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Aries[1]
Right ascension	02h 51m 29.586s[2]
Declination	+15° 04′ 55.44″[2]
Apparent magnitude (V)	+5.52[3]
Characteristics
Spectral type	B7 V[4]
U−B color index	−0.43[3]
B−V color index	−0.09[3]
Astrometry
Radial velocity (Rv)	+17±2[5] km/s
Proper motion (μ)	RA: +29.636 mas/yr[2] Dec.: −24.650 mas/yr[2]
Parallax (π)	7.0519±0.134 mas[2]
Distance	463 ± 9 ly (142 ± 3 pc)
Absolute magnitude (MV)	−0.38[1]
Details
A
Mass	3.84±0.08[6] M☉
Radius	3[7] R☉
Luminosity	301[6] L☉
Surface gravity (log g)	4.0±0.25[8] cgs
Temperature	13,121[6] K
Rotational velocity (v sin i)	165[6] km/s
Age	36+57 −27[8] Myr
B
Mass	1.0–1.2[8] M☉
Temperature	5,524±150[8] K
Metallicity [Fe/H]	−0.5[8] dex
Rotational velocity (v sin i)	5 km/s
Other designations
σ Ari, 43 Arietis, BD+14 480, FK5 1079, GC 3427, HD 17769, HIP 13327, HR 847, SAO 93144, PPM 118608[9]
Database references
SIMBAD	data

Sigma Arietis is a B-type main sequence star with a stellar classification of B7 V.^[4] 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 Sun, with this energy being radiated into space from its outer atmosphere at an 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 about 36^[8] million years old and 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. This object has a mass equal to or slightly greater than the Sun. It has an effective temperature of 5,524 K.^[8]