Theta Arae
Star in the constellation Ara
From Wikipedia, the free encyclopedia
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.
 | |
| 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]