Alpha Lupi

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Alpha Lupi
Lupus constellation map.svg
Red circle.svg
Location of α Lupi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Lupus
Right ascension 14h 41m 55.75579s[1]
Declination –47° 23′ 17.5155″[1]
Apparent magnitude (V) 2.30[2] (2.29 - 2.34[3])
Spectral type B1.5 III[4]
U−B color index –0.88[2]
B−V color index –0.20[2]
Variable type β Cep[3]
Radial velocity (Rv)+5.4 ± 0.6[5] km/s
Proper motion (μ) RA: −20.94[1] mas/yr
Dec.: −23.67[1] mas/yr
Parallax (π)7.02 ± 0.17 mas[1]
Distance460 ± 10 ly
(142 ± 3 pc)
Absolute magnitude (MV)−4.3[6]
Mass10.1 ± 1.0[7] M
Luminosity25,000[6] L
Surface gravity (log g)3.46[6] cgs
Temperature21,820 ± 2,160[8] K
Metallicity [Fe/H]0.04[9] dex
Rotational velocity (v sin i)16[5] km/s
Age16–20[5] Myr
Other designations
CD-46°9501, FK5 541, HD 129056, HIP 71860, HR 5469, SAO 225128[10]
Database references

Alpha Lupi (α Lupi, α Lup) is a blue giant star, and the brightest star in the southern constellation of Lupus. According to the Bortle Dark-Sky Scale, its apparent visual magnitude of 2.3[2] makes it readily visible to the naked eye even from highly light-polluted locales. Based upon parallax measurements made during the Hipparcos mission,[11] the star is around 460 light-years (140 parsecs) from the solar system.[1] It is one of the nearest supernova candidates.[12]


A light curve for Alpha Lupi, plotted from Hipparcos data[13]

Alpha Lupi is a giant star with a stellar classification of B1.5 III.[4] It has about ten times the mass of the sun (~10 M)[7] yet is radiating 25,000 times the Sun's luminosity.[6] The outer atmosphere has an effective temperature of 21,820 K,[8] which gives it the blue-white glow of a B-type star. In 1956 it was identified as a Beta Cephei variable by Bernard Pagel and colleagues,[14] which means it undergoes periodic changes in luminosity because of pulsations in the atmosphere. The variability period is 0.29585 days,[9] or just over 7 hours, 6 minutes. The magnitude varies by about 0.05 magnitudes, or about 5% of its brightness. A 14th magnitude star situated 26" from Alpha Lupi is listed as a companion in double star catalogues.[15]

This star 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] This is a gravitationally unbound stellar association with an estimated age of 16–20 million years. The association is also the source of a bubble of hot gas that contains the Sun, known as the Local Bubble.[5]


Visible from the Southern Hemisphere for much of the year, it can also be viewed for a shorter season from the northern tropics and from parts of the northern subtropical latitudes.


In Chinese, Kekouan 騎官 (Qí Guān), meaning Imperial Guards, refers to an asterism consisting of α Lupi, γ Lupi, δ Lupi, κ Centauri, β Lupi, λ Lupi, ε Lupi, μ Lup, π Lupi, and ο Lupi.[16] Consequently, the Chinese name for α Lupi itself is 騎官十 (Qí Guān shí, English: the Tenth Star of Imperial Guards.).[17]

R. H. Allen described this star as having the Chinese name Yang Mun or Men(南門), meaning "the South Gate", in his work Star-Names and their Meanings.[18] In Chinese astronomy, 南門 is located in Horn mansion and consisted of α and ε Centauri. It was referred to as Yang Mun, meaning "the south Gate". Allen also suggested that the Babylonian name for the star was "Kakkab Su-gub Gud-Elim" (Star Left Hand of the Horned Bull).[18]


  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:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600
  2. ^ a b c d 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
  3. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)", VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S, 1: 02025, Bibcode:2009yCat....102025S
  4. ^ a b Hiltner, W. A.; Garrison, R. F.; Schild, R. E. (July 1969), "MK Spectral Types for Bright Southern OB Stars", Astrophysical Journal, 157: 313–326, Bibcode:1969ApJ...157..313H, doi:10.1086/150069
  5. ^ 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/0601643, Bibcode:2006A&A...448.1001J, doi:10.1051/0004-6361:20041614, S2CID 17818058
  6. ^ a b c d e 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 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:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873
  8. ^ a b Sokolov, N. A. (May 1995), "The determination of T_eff_ of B, A and F main sequence stars from the continuum between 3200 A and 3600 A", Astronomy and Astrophysics Supplement, 110: 553–564, Bibcode:1995A&AS..110..553S
  9. ^ a b 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/0410442, Bibcode:2005A&A...433.1031D, doi:10.1051/0004-6361:20040397, S2CID 119340011
  10. ^ "V* alf Lup -- Variable Star of beta Cep type", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2009-10-26
  11. ^ Perryman, M. A. C.; et al. (April 1997), "The HIPPARCOS Catalogue", Astronomy & Astrophysics, 323: L49–L52, Bibcode:1997A&A...323L..49P
  12. ^ Firestone, R. B. (July 2014), "Observation of 23 Supernovae That Exploded <300 pc from Earth during the past 300 kyr", The Astrophysical Journal, 789 (1): 11, Bibcode:2014ApJ...789...29F, doi:10.1088/0004-637X/789/1/29, S2CID 122871106, 29
  13. ^ "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
  14. ^ Pagel, B. E. J. (1956), "Results of a search for bright β Cephei variables in the southern sky", Monthly Notices of the Royal Astronomical Society, 116: 10–24, Bibcode:1956MNRAS.116...10P, doi:10.1093/mnras/116.1.10
  15. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
  16. ^ (in 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
  17. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-30 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010]
  18. ^ a b Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc., p. 279, ISBN 0-486-21079-0