Theta Arietis

Theta Arietis, is a binary star^[8] system in the northern constellation of Aries. Its name is a Bayer designation that is Latinised from θ Arietis, and abbreviated Theta Ari or θ Ari. This star is faintly visible to the naked eye with an apparent visual magnitude of 5.58.^[3] With an annual parallax shift of 7.22 mas,^[2] the distance to this star is an estimated 452 light-years (139 parsecs) with a 7-light-year margin of error. It is drifting further away from the Sun with a radial velocity of +12 km/s.^[2]

ConstellationAries^[1]

Right ascension02^h 18^m 07.531^s[2]

Declination+19° 54′ 04.17″^[2]

Apparentmagnitude(V)5.58^[3]

Quick facts Constellation, Right ascension ...

θ Arietis

Location of θ Arietis (circled)
Observation data Epoch J2000      Equinox ICRS
Constellation	Aries[1]
Right ascension	02h 18m 07.531s[2]
Declination	+19° 54′ 04.17″[2]
Apparent magnitude (V)	5.58[3]
Characteristics
Evolutionary stage	main sequence[4]
Spectral type	A1 Vn[5]
U−B color index	+0.02[6]
B−V color index	+0.01[6]
Variable type	Constant[7]
Astrometry
Radial velocity (Rv)	+11.95±0.78[2] km/s
Proper motion (μ)	RA: −7.832 mas/yr[2] Dec.: −3.654 mas/yr[2]
Parallax (π)	7.2220±0.1043 mas[2]
Distance	452 ± 7 ly (138 ± 2 pc)
Absolute magnitude (MV)	−0.10[1]
Details
A
Mass	2.10+0.37 −0.31 M☉[8] 2.94±0.06[4] M☉
Radius	1.9–2.5[9] R☉
Luminosity	106[1] L☉
Surface gravity (log g)	4.00±0.25[8] cgs
Temperature	9,500±1,000[8] K
Rotational velocity (v sin i)	186[10] km/s
Age	107+286 −93[8] Myr
B
Mass	1.0+0.02 −0.04[8] M☉
Temperature	5,578±109[8] K
Metallicity [Fe/H]	0.0[8] dex
Rotational velocity (v sin i)	5[8] km/s
Other designations
θ Ari, 22 Arietis, BD+19 340, FK5 81, HD 14191, HIP 10732, HR 669, SAO 92877[11]
Database references
SIMBAD	data

Close

The primary, component A, is a white-hued, A-type main-sequence star with a stellar classification of A1 Vn.^[5] It is spinning at a rapid pace as shown by the projected rotational velocity of 186 km/s.^[10] This is causing the "nebulous" appearance of the absorption lines indicated by the 'n' suffix in the classification. In 2005, C. Neiner and associates classified this as a Be star because is displays emission features in the hydrogen Balmer lines.^[7]

In 2016, a solar-mass companion was reported in close orbit around this star, based on observations using adaptive optics with the Gemini North Telescope.^[8]