Tau2 Arietis

Tau² Arietis is a binary star^[9] system in the northern constellation on Aries. Its name is a Bayer designation that is Latinized from τ² Arietis, and abbreviated Tau² Ari or τ² Ari. The combined apparent visual magnitude of this system is +5.09,^[3] which is bright enough to be seen with the naked eye. With an annual parallax shift of 9.76 mas,^[10] it is located at a distance of approximately 334 light-years (102 parsecs) from Earth, give or take an 8 light-year margin of error. At this distance the brightness of the star is diminished by 0.18 in magnitude because of extinction from interstellar gas and dust.^[11] The system is receding from the Sun with a radial velocity of +2.5 km/s.^[6]

For other stars with this Bayer designation, see τ Arietis.

τ²

Location of τ2 Arietis (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Aries[1]
Right ascension	03h 22m 45.241s[2]
Declination	+20° 44′ 31.44″[2]
Apparent magnitude (V)	+5.09[3]
Characteristics
Spectral type	K3 III[4][5]
U−B color index	+1.27[3]
B−V color index	1.238[6]
Astrometry
Radial velocity (Rv)	+2.45±0.24[6] km/s
Proper motion (μ)	RA: −53.633 mas/yr[2] Dec.: −14.447 mas/yr[2]
Parallax (π)	9.7639±0.2442 mas[2]
Distance	334 ± 8 ly (102 ± 3 pc)
Absolute magnitude (MV)	+0.17[1]
Details
Mass	2.04±0.60[7] M☉
Radius	19[6] R☉
Luminosity	120[6] L☉
Surface gravity (log g)	2.23±0.11[7] cgs
Temperature	4,479±92[7] K
Metallicity [Fe/H]	+0.02[6] dex
Rotational velocity (v sin i)	3.4[6] km/s
Age	1.6+0.6 −0.4[7] Gyr
Other designations
τ2 Ari, 63 Arietis, BD+20 551, GC 4026, HD 20893, HIP 15737, HR 1015, SAO 75899, PPM 92448, WDS J03228+2045A[8]
Database references
SIMBAD	data

The primary component is an evolved giant star with a stellar classification of K3 III.^[4] It is an estimated 1.6 billion years old and is spinning with a projected rotational velocity of 3.4 km/s.^[6] With double the mass of the Sun,^[7] it has expanded to 19 times the radius of the Sun.^[6] The star is radiating 120 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,406 K,^[6] giving it the cool orange glow of a K-type star. At an angular separation of 0.53 arcseconds is a magnitude 8.50 companion.^[9]