  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ara |
| Right ascension | 17h 25m 17.989s[1] |
| Declination | −55° 31′ 47.57″[1] |
| Apparent magnitude (V) | 2.84[2] |
| Characteristics | |
| Evolutionary stage | Red supergiant |
| Spectral type | K0/1Ib[3] |
| U−Bcolor index | +1.56[4] |
| B−Vcolor index | +1.46[4] |
| Astrometry | |
| Radial velocity (Rv) | −0.3±0.2[5] km/s |
| Proper motion (μ) | RA: −8.51mas/yr[6] Dec.: −25.24mas/yr[6] |
| Parallax (π) | 4.5601±0.2077 mas[1] |
| Distance | 714+39 −34 ly (218.8+12.0 −10.4 pc)[7] |
| Absolute magnitude (MV) | −3.494[8] |
| Details[9] | |
| Mass | 5.89±0.07 or 7.89±0.4 M☉ |
| Radius | 141.4±6.6 R☉ |
| Luminosity | 5,774±535 L☉ |
| Surface gravity (log g) | 0.97±0.06 cgs |
| Temperature | 4,232±17 K |
| Metallicity[Fe/H] | 0.5±0.1 dex |
| Rotational velocity (v sin i) | 5.4±1.0[5] km/s |
| Age | 50.1±4.4[10] Myr |
| Other designations | |
| CPD−55°8100,FK5 645,GC 23515,HD 157244,HIP 85258,HR 6461,SAO 244725,PPM 345989[11] | |
| Database references | |
| SIMBAD | data |
Beta Arae is thebrightest star in theconstellation ofAra. This is a very luminous, relatively youngred supergiant with anapparent visual magnitude of 2.84 and anabsolute magnitude of −3.494.[2][8] Its name is aBayer designation that isLatinized from β Arae, and abbreviated Beta Ara or β Ara. Based on a photogeometric estimation method, it is 710light-years away,[7] a distance of whichinterstellar extinction in the line of sight reduces its apparent magnitude by 0.193magnitudes.[9]
Thespectrum of this star matches astellar classification of K0/1 Ib,[3] with theluminosity class notation 'Ib' indicating that the star is asupergiant. It has an age estimated at 50 million years,[10] having spent much of its life as aB-type star.[12] Currently, it has expanded to 141 times the Sun's size and is 5,800 times more luminous.[9] Beta Arae is radiating energy from its outer envelope at aneffective temperature of4,200 K, which causes it to take on the orange hue of aK-type star.[13] This enlarged star appears to be rotating slowly with aprojected rotational velocity of about5 km/s.[5] The abundance of elements other than hydrogen and helium, itsmetallicity, is more than three times that of the Sun.[5][a]
Beta Arae is the star'sBayer designation. Other designations include HD 157244 (from theHenry Draper Catalogue), HIP 85258 (from theHipparcos catalogue) and HR 6461 (from theBright Star Catalogue).[11]
Rarely, this star is calledVasat-ül-cemre aTurkisation ofArabic وسط الجمر (wasaṭ al-jamar), meaning "middle of the embers."[14] The constellation is named in Arabic المجمرة (al-mijmarah), meaningbrazier/incense-burner.[15] InChinese,杵 (Chǔ), meaningPestle, refers to an asterism of β,σ andα Arae.[16] TheChinese name for β Arae is杵三 (Chǔ sān, English:the Third Star of Pestle.)[17]
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