Theta Scorpii

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Theta Scorpii
Scorpius constellation map.svg
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The position of θ Scorpii in the Scorpius constellation.
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 17h 37m 19.12985s[1]
Declination –42° 59′ 52.1808″[1]
Apparent magnitude (V) +1.87[2]
Spectral type F0 II[3]
U−B color index +0.21[2]
B−V color index +0.40[2]
Radial velocity (Rv) +1.4[4] km/s
Proper motion (μ) RA: +5.54[1] mas/yr
Dec.: –3.12[1] mas/yr
Parallax (π) 10.86 ± 1.49[1] mas
Distance approx. 300 ly
(approx. 90 pc)
Mass 5.66 ± 0.65[5] M
Radius 26[6] R
Luminosity 1,834[5] L
Surface gravity (log g) 2.4 ± 0.2[7] cgs
Temperature 7,268[5] K
Rotational velocity (v sin i) 125[8] km/s
Other designations
Sargas, Girtab, 160 G. Scorpii, CCDM 17373-4300, FK5 654, HD 159532, HIP 86228, HR 6553, SAO 228201.[9]

Theta Scorpii (θ Sco, θ Scorpii) is a star in the southern zodiac constellation of Scorpius. It has the traditional name Sargas, of Sumerian origin.[10] In Chinese, it is referred to as 尾宿五 (Mandarin: wěi xiù wǔ), the Fifth Star of the Tail.[citation needed] The apparent visual magnitude of this star is +1.87,[2] making it readily visible to the naked eye and one of the brightest stars in the night sky. It is sufficiently near that the distance can be measured directly using the parallax technique, which yields an estimate of roughly 300 light years (90 parsecs).[1]

This is an evolved bright giant star with a stellar classification of F0 II.[3] With a mass 5.7 times that of the Sun, it has expanded to about 26[6] times the Sun's radius. It is radiating 1,834[5] times as much luminosity as the Sun from its outer envelope at an effective temperature of 7,268,[5] giving it the yellow-white hued glow of an F-type star. This star is rotating rapidly, giving it an oblate shape with an equatorial radius 19% larger than the polar radius.[8]

It has a magnitude 5.36 companion at an angular separation of 6.470 arcseconds.[11]

Modern legacy[edit]

Sargas appears on the flag of Brazil, symbolising the state of Alagoas.[12]


  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. 
  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), Bibcode:1966CoLPL...4...99J 
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars 2, Ann Arbor: Dept. of Astronomy, University of Michigan, 
  4. ^ Wilson, R. E. (1953). General Catalogue of Stellar Radial Velocities. Carnegie Institute of Washington D.C. Bibcode:1953GCRV..C......0W. 
  5. ^ a b c d e Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355 
  6. ^ a b Pasinetti-Fracassini, L. E. et al. (February 2001), "Catalogue of Stellar Diameters (CADARS)", Astronomy and Astrophysics 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451 
  7. ^ Samedov, Z. A., "Investigation of the atmospheres of the stars ι1 Sco (F2 Ia) and θ Sco (F1 II)", Astrophysics 28 (3): 335–341, Bibcode:1988Ap.....28..335S, doi:10.1007/BF01112969 
  8. ^ a b van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2. 
  9. ^ "tet Sco -- Variable Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-02-18 
  10. ^ Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the solar system, Dover books explaining science 3 (2 ed.), Courier Dover Publications, p. 1676, ISBN 0-486-23673-0 
  11. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. 
  12. ^ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website. 

External links[edit]