Theta Arae

Theta Arae
Diagram showing star positions and boundaries of the Ara constellation and its surroundings
The location of θ Arae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ara
Right ascension 18h 06m 37.87129s[1]
Declination –50° 05′ 29.3125″[1]
Apparent magnitude (V) +3.67[2]
Characteristics
Spectral type B2 Ib[3]
U−B color index –0.870[2]
B−V color index –0.109[2]
Astrometry
Radial velocity (Rv)+3.4[4] km/s
Proper motion (μ) RA: –8.27[1] mas/yr
Dec.: –8.70[1] mas/yr
Parallax (π)4.01 ± 0.15 mas[1]
Distance810 ± 30 ly
(249 ± 9 pc)
Absolute magnitude (MV)−3.33[5]
Details
Mass8.9 ± 0.1[6] M☉
Radius20.1[7] R☉
Luminosity3,450[5] L☉
Surface gravity (log g)2.70[8] cgs
Temperature17,231 ± 231[7] K
Rotational velocity (v sin i)95[9] km/s
Age28.2 ± 4.7[6] Myr
Other designations
θ Ara, CD−50° 11720, FK5 1471, HD 165024, HIP 88714, HR 6743, SAO 245242.[10]
Database references
SIMBADdata

Theta Arae, Latinized from θ Arae, is the Bayer designation for a star in the constellation Ara. It has an apparent visual magnitude of +3.67,[2] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 4.01 mas,[1] Theta Arae is 810 light-years (250 parsecs) distant from the Earth.

This is a supergiant star with a stellar classification of B2 Ib.[3] It has nearly nine[6] times the mass of the Sun and is 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]

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