Sigma Arietis
Star in the constellation Aries
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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.[6] On November 20, 1952, it was observed being occulted by the planet Jupiter.[10]
 | |
| 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 | |
| Evolutionary stage | main sequence[4] |
| Spectral type | B7 V[5] |
| U−B color index | −0.43[3] |
| B−V color index | −0.09[3] |
| Astrometry | |
| Radial velocity (Rv) | +17±2[6] 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[4] M☉ |
| Radius | 3[7] R☉ |
| Luminosity | 301[4] L☉ |
| Surface gravity (log g) | 4.0±0.25[8] cgs |
| Temperature | 13,121[4] K |
| Rotational velocity (v sin i) | 165[4] 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.[5] This is a large star with three[7] times the radius of the Sun and 3.8[4] times the Sun's mass. It shines around 301[4] 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.[4] 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.[4] 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]