Beta Lupi

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

Location of β Lupus (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Lupus
Right ascension 14h 58m 31.92536s[1]
Declination −43° 08′ 02.2699″[1]
Apparent magnitude (V) 2.68[2]
Spectral type B2 III[3]
U−B color index −0.902[4]
B−V color index −0.226[4]
Variable type β Cep[5]
Radial velocity (Rv) +0.1 ± 1.0[3] km/s
Proper motion (μ) RA: −35.78[1] mas/yr
Dec.: −39.83[1] mas/yr
Parallax (π) 8.52 ± 0.18[1] mas
Distance 383 ± 8 ly
(117 ± 2 pc)
Absolute magnitude (MV) −3.3[6]
Mass 8.8 ± 0.2[7] M
Radius 6.6[8] R
Luminosity 10,000[6] L
Surface gravity (log g) 3.76[6] cgs
Temperature 24,090[9] K
Metallicity [Fe/H] −0.35 ± 0.11[5] dex
Rotational velocity (v sin i) 92[3] km/s
Age 24.6 ± 2.7[7] Myr
Other designations
CD−42° 9853, FK5 552, HD 132058, HIP 73273 , HR 5571, SAO 225335.[10]
Database references

Beta Lupi (β Lupi, β Lup), or Kekouan, is a star in the southern constellation of Lupus. It has an apparent visual magnitude of 2.7,[2] making it readily visible to the naked eye. Based upon parallax measurements, this star is located at a distance of about 383 light-years (117 parsecs) from Earth.[2]


The stellar classification of B2 III indicates this is a giant star.[3] The effective temperature of the star's outer envelope is 24,090 K,[9] giving it the blue-white hue of a B-type star.[11] With an age of around 25 million years,[7] it is near the end of its hydrogen phase, where hydrogen is fused into the element helium, and transferring into a red supergiant star. At about 8.8[7] solar masses, it may have enough mass to end its life as a Type II supernova, but there is the possibility of Beta Lupi becoming a white dwarf.[12]

This is a multi-period Beta Cephei variable with a dominant oscillation period of 0.232 days.[5] It is a proper motion member of the Upper-Centaurus Lupus sub-group in the Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[6] Beta Lupi has a high proper motion of more than 50 mas per year, suggesting a significant transverse velocity.[13]

It lies close to the supernova remnant SN 1006.[citation needed]


In Chinese, 騎官 (Qí Guān), meaning Imperial Guards, refers to an asterism consisting of β Lupi, γ Lupi, δ Lupi, κ Centauri, λ Lupi, ε Lupi, μ Lup, π Lupi, ο Lupi and α Lupi.[14] Consequently, β Lupi itself is known as 騎官四 (Qí Guān sì, English: the Fourth Star of Imperial Guards.).[15] From the French rendering of this Chinese name derives the traditional European name Kekouan (Ke Kwan).[16]

See also[edit]


  1. ^ a b c d e 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 c Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W 
  3. ^ a b c d Jilinski, E.; et al. (March 2006), "Radial velocity measurements of B stars in the Scorpius-Centaurus association", Astronomy and Astrophysics, 448 (3): 1001–1006, arXiv:astro-ph/0601643Freely accessible, Bibcode:2006A&A...448.1001J, doi:10.1051/0004-6361:20041614 
  4. ^ a b Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168 
  5. ^ a b c Daszyńska-Daszkiewicz, J.; Niemczura, E. (April 2005), "Metallicity of mono- and multiperiodic β Cephei stars", Astronomy and Astrophysics, 433 (3): 1031–1035, arXiv:astro-ph/0410442Freely accessible, Bibcode:2005A&A...433.1031D, doi:10.1051/0004-6361:20040397 
  6. ^ a b c d de Geus, E. J.; de Zeeuw, P. T.; Lub, J. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1-2): 44–61, Bibcode:1989A&A...216...44D 
  7. ^ a b c d 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. ^ Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601 
  9. ^ a b Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134Freely accessible, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147 
  10. ^ "bet Lup -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-16 
  11. ^ "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 
  12. ^ Kaler, James B. (2007), "Beta Lupi", Stars, University of Illinois, retrieved 2009-07-03 
  13. ^ Jiménez-Esteban, F. M.; Caballero, J. A.; Solano, E. (January 2011), "Identification of blue high proper motion objects in the Tycho-2 and 2MASS catalogues using Virtual Observatory tools", Astronomy and Astrophysics, 525: A29, arXiv:1009.3466Freely accessible, Bibcode:2011A&A...525A..29J, doi:10.1051/0004-6361/201015223 
  14. ^ (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.
  15. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.]
  16. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Lupus

External links[edit]