Theta Arae

Theta Arae is a star in the southern constellation Ara. Its name is a Bayer designation that is Latinized from θ Arae, and abbreviated Theta Ara or θ Ara. This star has an apparent visual magnitude of +3.67,^[3] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 4.01 mas,^[2] Theta Arae is 810 light-years (250 parsecs) distant from the Earth.

Theta Arae

The location of θ Arae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Ara[1]
Right ascension	18h 06m 37.871s[2]
Declination	−50° 05′ 29.31″[2]
Apparent magnitude (V)	+3.67[3]
Characteristics
Spectral type	B2 Ib[4]
U−B color index	−0.870[3]
B−V color index	−0.109[3]
Astrometry
Radial velocity (Rv)	+3.4[5] km/s
Proper motion (μ)	RA: −8.27 mas/yr[2] Dec.: −8.70 mas/yr[2]
Parallax (π)	4.01±0.15 mas[2]
Distance	810 ± 30 ly (249 ± 9 pc)
Absolute magnitude (MV)	−3.33[1]
Details
Mass	8.9±0.1[6] M☉
Radius	20.1[7] R☉
Luminosity	3,450[1] L☉
Surface gravity (log g)	2.70[8] cgs
Temperature	17,231±231[7] K
Rotational velocity (v sin i)	95[9] km/s
Age	28.2±4.7[6] Myr
Other designations
θ Ara, CD−50°11720, FK5 1471, GC 24635, HD 165024, HIP 88714, HR 6743, SAO 245242, PPM 346577[10]
Database references
SIMBAD	data

This is a supergiant star with a stellar classification of B2 Ib.^[4] At an age of 28 million years,^[6] it has a high rate of spin with a projected rotational velocity of 95 km/s.^[9] This star has nearly nine^[6] times the mass of the Sun and over 20^[7] times the Sun's radius. The outer atmosphere of this star has an effective temperature of 17,231 K;^[7] much hotter than the surface of the Sun. At this heat, the star shines with the characteristic blue-white hue of a B-type star.^[11]