Beta Arae

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Beta Arae
Diagram showing star positions and boundaries of the Ara constellation and its surroundings
Cercle rouge 100%.svg

Location of β Arae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ara
Right ascension 17h 25m 17.98835s[1]
Declination −55° 31′ 47.5868″[1]
Apparent magnitude (V) 2.84[2]
Spectral type K3 Ib-II[3]
U−B color index +1.56[4]
B−V color index +1.46[4]
Radial velocity (Rv) -0.30 ± 0.20[3] km/s
Proper motion (μ) RA: −8.51[1] mas/yr
Dec.: −25.24[1] mas/yr
Parallax (π) 5.05 ± 0.64[1] mas
Distance approx. 650 ly
(approx. 200 pc)
Absolute magnitude (MV) −3.494[5]
Mass 8.21[6] M
Luminosity 5,636[6] L
Surface gravity (log g) 1.20[6] cgs
Temperature 4,197[6] K
Metallicity [Fe/H] −0.05[6] dex
Rotational velocity (v sin i) 5.4 ± 1.0[3] km/s
Age 50.1 ± 4.4[7] Myr
Other designations
CPD −55° 8100, FK5 645, HD 157244, HIP 85258, HR 6461, SAO 244725.[8]
Database references

Beta Arae (β Ara, β Arae) is the brightest star in the constellation Ara, with an apparent visual magnitude of 2.8.[2] Parallax measurements place it at a distance of roughly 650 light-years (200 parsecs) from Earth.[1]

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). This represents two of the evolutionary stages that a massive star passes through after it has exhausted the hydrogen at its core. Beta Arae is radiating energy from its outer envelope at an effective temperature of 4,200 K, which causes it to take on the orange hue of a K-type star.[9] 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, what astronomer term the star's metallicity, is more than three times the abundance in the Sun.[3][10]

Rarely, this star is called by the name Vasat-ül-cemre in Turkish spelling, derived from Arabic word ﻭﺳﻂ (wasath) and ﺟﻤﻩﺮ (khamra), meaning "middle of fire".[11][unreliable source?] In Chinese, (Chǔ), meaning Pestle, refers to an asterism consisting of β Arae, σ Arae and α Arae.[12] Consequently, β Arae itself is known as 杵三 (Chǔ sān, English: the Third Star of Pestle.)[13]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, Astronomisches Rechen-Institut Heidelberg, 35 (35), Bibcode:1999VeARI..35....1W 
  3. ^ a b c d e f De Medeiros, J. R.; et al. (November 2002), "A catalog of rotational and radial velocities for evolved stars. II. Ib supergiant stars", Astronomy and Astrophysics, 395: 97–98, Bibcode:2002A&A...395...97D, doi:10.1051/0004-6361:20021214 
  4. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J 
  5. ^ Cassatella, A.; Altamore, A.; Badiali, M.; Cardini, D. (2001). "On the Wilson-Bappu relationship in the Mg II k line". Astronomy and Astrophysics. 374 (3): 1085. Bibcode:2001A&A...374.1085C. doi:10.1051/0004-6361:20010816. 
  6. ^ a b c d e Heiter, U.; Jofré, P.; Gustafsson, B.; Korn, A. J.; Soubiran, C.; Thévenin, F. (2015). "Gaia FGK benchmark stars: Effective temperatures and surface gravities". Astronomy & Astrophysics. 582: A49. arXiv:1506.06095Freely accessible. Bibcode:2015A&A...582A..49H. doi:10.1051/0004-6361/201526319. 
  7. ^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883Freely accessible, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x 
  8. ^ "bet Ara -- Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2012-01-15. 
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-01-16 
  10. ^ The abundance is estimated by taking [Fe/H] to the power of ten, thus:
    10[Fe/H] = 10+0.5 = 3.1
  11. ^ (Turkish) YILDIZ ADLARI SÖZLÜĞÜ - Mustafa Pultar (Vasat-ül-cemre)
  12. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  13. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 1 日

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