| |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ara |
| Right ascension | 17h25m 17.989s[1] |
| Declination | −55° 31′ 47.574″[1] |
| Apparent magnitude (V) | 2.84[2] |
| Characteristics | |
| Spectral type | K3 Ib-II[3] |
| U−B color index | +1.56[4] |
| B−V color index | +1.46[4] |
| Astrometry | |
| Radial velocity (Rv) | −0.30±0.20[3] km/s |
| Proper motion (μ) | RA: −8.51[5] mas/yr Dec.: −25.24[5] mas/yr |
| Parallax (π) | 4.5601 ± 0.2077 mas[1] |
| Distance | 713+39 −34 ly (218.8+12 −10.4 pc)[6] |
| Absolute magnitude (MV) | −3.494[7] |
| Details[8] | |
| Mass | 5.89±0.07or7.89±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[3] km/s |
| Age | 50.1±4.4[9] Myr |
| Other designations | |
CPD−55°8100, FK5 645, HD 157244, HIP 85258, HR 6461, SAO 244725[10] | |
| Database references | |
| SIMBAD | data |
Beta Arae (β Ara, β Arae), is the brightest star in the constellationofAra. It is a very luminous, relatively young, giant or supergiant star with an apparent magnitude of 2.84 and an absolute magnitude of -3.494.[2][7] It is located about 713 light-years from Earth.[6] At this distance, its apparent magnitude is diminished by 0.193 magnitudes due to interstellar extinction between Earth and the star.[8]
The spectrum of this star matches a stellar classification of K3 Ib-IIa,[3] with the luminosity class notation 'Ib-IIa' indicating that the star lies part way between a higher luminosity bright giant (IIa) and a lower luminosity supergiant (Ib). It has an age estimated at 50 million years, having spent much of its life as a B-type star.[11] Currently, it has expanded to 141 times the Sun's size and is 5,800 times more energetic.[8] Beta Arae is radiating energy from its outer envelope at an effective temperatureof4,200 K, which causes it to take on the orange hue of a K-type star.[12] This enlarged star appears to be rotating slowly with a projected rotational velocity of about 5 km/s.[3] The abundance of elements other than hydrogen and helium, its metallicity, is more than three times that of the Sun.[3][a]
Beta Arae is the star's Bayer designation. Other designations include HD 157244 (from the Henry Draper Catalogue), HIP 85258 (from the Hipparcos catalogue) and HR 6461 (from the Bright Star Catalogue).[10]
Rarely, this star is called Vasat-ül-cemreaTurkisationofArabic وسط الجمر (wasaṭ al-jamar), meaning "middle of the embers."[13] The constellation is named in Arabic المجمرة (al-mijmarah), meaning brazier/incense-burner.[14]InChinese, 杵 (Chǔ), meaning Pestle, refers to an asterism of β, σ and α Arae.[15] The Chinese name for β Arae is 杵三 (Chǔ sān, English: the Third Star of Pestle.)[16]
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