Alpha Arae

Alpha Arae

α Arae (Choo) in the constellation Ara.
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ara
Right ascension 17h 31m 50.49153s[1]
Declination −49° 52′ 34.1220″[1]
Apparent magnitude (V) 2.93[2] (2.76 to 2.90)[3]
Characteristics
Spectral type B2 Vne[4]
U−B color index −0.72[2]
B−V color index −0.16[2]
R−I color index −0.24[3]
Variable type BE[5]
Astrometry
Radial velocity (Rv)0[6] km/s
Proper motion (μ) RA: −33.27[1] mas/yr
Dec.: −67.22[1] mas/yr
Parallax (π)12.20 ± 0.85 mas[1]
Distance270 ± 20 ly
(82 ± 6 pc)
Absolute magnitude (MV)−1.72[7]
Details
Mass9.6[8] M☉
Radius4.5[9] R☉
Luminosity (bolometric)5,800[8] L☉
Surface gravity (log g)3.99[9] cgs
Temperature18,044[9] K
Rotational velocity (v sin i)375[10] km/s
Other designations
Choo, α Ara, CD−49°11511, FK5 651, HD 158427, HIP 85792, HR 6510, NSV 8999, SAO 228069[11][12][13]
Database references
SIMBADdata

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,[2] 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.[9]

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