Alpha Arae
Alpha Arae, Latinized from α Arae, is the second brightest star in the southern constellation of Ara. With an average apparent visual magnitude 2.93, it is readily visible to the naked eye from the southern hemisphere. This star is close enough to the Earth that its distance can be estimated using parallax data collected during the Hipparcos mission. It is around 270 light-years (83 parsecs) away, with a 7% margin of error. The visual magnitude of the star is diminished by 0.10 magnitudes as a result of extinction from intervening gas and dust.
α Arae (Choo) in the constellation Ara. | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Ara |
| Right ascension | 17h 31m 50.49153s |
| Declination | −49° 52′ 34.1220″ |
| Apparent magnitude (V) | 2.93 (2.76 to 2.90) |
| Characteristics | |
| Spectral type | B2 Vne |
| U−B color index | −0.72 |
| B−V color index | −0.16 |
| R−I color index | −0.24 |
| Variable type | BE |
| Astrometry | |
| Radial velocity (Rv) | 0 km/s |
| Proper motion (μ) | RA: −33.27 mas/yr Dec.: −67.22 mas/yr |
| Parallax (π) | 12.20 ± 0.85 mas |
| Distance | 270 ± 20 ly (82 ± 6 pc) |
| Absolute magnitude (MV) | −1.72 |
| Details | |
| Mass | 9.6 M☉ |
| Radius | 4.5 R☉ |
| Luminosity (bolometric) | 5,800 L☉ |
| Surface gravity (log g) | 3.99 cgs |
| Temperature | 18,044 K |
| Rotational velocity (v sin i) | 375 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
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