Kappa Scorpii

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κ Scorpii
Scorpius constellation map.svg
Red circle.svg

Location of κ Sco (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 17h 42m 29.27520s[1]
Declination –39° 01′ 47.9391″[1]
Apparent magnitude (V) 2.39[2]
Spectral type B1.5 III[3]
U−B color index -0.914[4]
B−V color index -0.228[4]
Variable type β Cephei
Radial velocity (Rv) –14.0[2] km/s
Proper motion (μ) RA: -6.05[1] mas/yr
Dec.: -25.54[1] mas/yr
Parallax (π) 6.75 ± 0.17[1] mas
Distance 480 ± 10 ly
(148 ± 4 pc)
Period (P) 195.65 days
Eccentricity (e) 0.488 ± 0.005
Periastron epoch (T) 92.7 ± 0.5
Semi-amplitude (K1)
48.0 ± 0.3 km/s
κ Sco A
Mass 17[5] M
Radius 6.8[5] R
Surface gravity (log g) 4.01[5] cgs
Temperature 23,400[5] K
Rotation 1.90 days[5]
Rotational velocity (v sin i) 105[6] km/s
Age 25.1 ± 1.3[7] Myr
κ Sco B
Mass 12[5] M
Radius 5.8[5] R
Surface gravity (log g) 4.00[5] cgs
Temperature 18,800[5] K
Other designations
Girtab, HR 6580, CD-38° 12137, HD 160578, SAO 209163, FK5 660, CPD°-38 6992, HIP 86670.
Database references

Kappa Scorpii (κ Sco, κ Scorpii) is a binary star system in the southern constellation of Scorpius. With an apparent visual magnitude of 2.4,[2] this star system is readily visible to the naked eye. Parallax measurements place it at an estimated distance of roughly 480 light-years (150 parsecs) from the Earth.[1]


This is a spectroscopic binary, which is a type of binary star system in which the two stars are so close together that they have not been individually resolved with a telescope. The pair orbit each other with a period of about 196 days and an eccentricity of nearly 0.5.[5] The combined spectrum of this pair matches a star with a stellar classification of B1.5 III.[3] The 'III' luminosity class indicates the presence of a giant star that has exhausted the supply of hydrogen at its core and is in a late evolutionary stage.

The primary component of the pair, κ Sco A, is a variable star of Beta Cephei type. It is undergoing radial pulsations with a dominant frequency of 4.99922 cycles per day, or 4.8 hours per cycle. There are overlapping secondary pulsation frequencies of about 4.85 and 5.69 cycles per day.[8] This star has about 17 times the mass of the Sun and is nearly 7 times the Sun's radius.[5] The effective temperature of the outer envelope is 23,400 K,[5] giving it a blue-white hue. It is rotating rapidly, with an estimated period of only 1.9 days and an axis of rotation that is inclined by about 40° to the line of sight from the Earth.[5]

The secondary component, κ Sco B, is smaller than the primary, but still much larger than the Sun. It has about 12 times the mass of the Sun and nearly six times the Sun's radius.[5] The effective temperature of 18,800 K[5] is also higher than the Sun's, which is at 5,778 K.

Traditional name[edit]

κ Scorpii has been called Girtab,[9] which is the Sumerian word for 'scorpion'. The name has survived through the Babylonian star catalogues,[10] and was originally applied to an asterism comprising this star, Lambda Scorpii, Upsilon Scorpii, and Iota Scorpii.[9]

Modern legacy[edit]

κ Scorpii appears on the flag of Brazil, symbolising the state of Paraíba.[11]


  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, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, 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", Veröff. Astron. Rechen-Inst. Heidelb, Astronomisches Rechen-Institut Heidelberg, 35 (35): 1, Bibcode:1999VeARI..35....1W 
  3. ^ a b Houk, Nancy (1978), "Michigan catalogue of two-dimensional spectral types for the HD star", Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0, Ann Arbor: Dept. of Astronomy, University of Michigan: distributed by University Microfilms International, 3, Bibcode:1982mcts.book.....H 
  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 d e f g h i j k l m n o p Uytterhoeven, K.; et al. (June 2001), "Line-profile variations of the double-lined spectroscopic binary kappa Scorpii", Astronomy and Astrophysics, 371 (3): 1035–1047, Bibcode:2001A&A...371.1035U, doi:10.1051/0004-6361:20010456 
  6. ^ Bernacca, P. L.; Perinotto, M. (1970), "A Catalogue of Stellar Rotational Velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B 
  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, Bibcode:2011MNRAS.410..190T, arXiv:1007.4883Freely accessible, doi:10.1111/j.1365-2966.2010.17434.x 
  8. ^ Uytterhoeven, K.; et al. (March 2005), "Disentangling component spectra of κ Scorpii, a spectroscopic binary with a pulsating primary. II. Interpretation of the line-profile variability", Astronomy and Astrophysics, 432 (3): 955–967, Bibcode:2005A&A...432..955U, doi:10.1051/0004-6361:20041444 
  9. ^ a b Falkner, David E. (2011), The Mythology of the Night Sky: An Amateur Astronomer's Guide to the Ancient Greek and Roman Legends, Patrick Moore's Practical Astronomy, Springer, p. 106, ISBN 1-4614-0136-4 
  10. ^ Ridpath, Ian (1989), Star tales, James Clarke & Co., p. 114, ISBN 0-7188-2695-7 
  11. ^ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website. 

External links[edit]

  • Kaler, James B., "Kappa Sco", Stars, University of Illinois, retrieved 2014-02-18