Theta Scorpii

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Theta Scorpii
Observational Data
Designation θ Scorpii
Sargas
Right ascension 17h 37m 19.1299s[1][2]
Declination -42° 59′ 52.1808″[1][2]
Constellation Scorpius
Type of object Giant star
Magnitude Apparent Mag: +1.86[3]
Absolute Mag: -2.96[3]
Astrometry
Distance from Earth 300.33 ly[3]
Radial velocity 1.4±2 km/s[1][4]
Proper motion RA: 5.54 mas/yr[1][2]
Dec.: -3.12 mas/yr[1][2]
Parallax 10.86±1.49 mas mas[1][2]

Theta Scorpii, also known as Sargas, is a giant star in the constellation of Scorpius, the scorpion.[3] Its traditional name of Sargas is of Sumerian origin but its meaning in Sumerian is not known.[5] It's also sometimes called "Girtab" which is also Sumerian and is known to mean "scorpion".[6] However this is normally used to refer to another star in Scorpius, namely Kappa Scorpii. The star is yellow belonging to the spectral class F0II. It also has a fainter companion star with a magnitude of +5.36, located 6.470 arc seconds from Theta Scropii.[5] Theta Scorpii's low declination of -43° means it is normally observed close to the horizon in the Northern hemisphere. This is useful for testing how the brightness of a star changes when it is seen close to the horizon, where its light must travel though a lot of atmosphere.

The star is thought to lie 300.33 light years from Earth, though other sources place it lower at 272 ly.[3][6] Sargas weighs 5.7 solar masses and has a radius of 26 solar radii.[5] Its surface is hotter than that of the Sun at an estimated 7,200 kelvin and it radiates 1,834 times as much energy than the Sun.[6] Its equatorial rotation speed is over 50 times that of the Sun, but the large size still gives it a fairly long rotation period of 10 days.[6]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Theta Scorpii. Simbad Astronomical Database. simbad.u-strasbg.fr. Retrieved on 2019-07-21.
  2. 2.0 2.1 2.2 2.3 2.4 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics 474 (2): 653-664. doi:10.1051/0004-6361:20078357. Bibcode2007A&A...474..653V.  arXiv:0708.1752
  3. 3.0 3.1 3.2 3.3 3.4 Sargas (Theta Scorpii). universeguide.com. Retrieved on 2019-07-21.
  4. Wilson, R. (1953). General catalogue of stellar radial velocities. Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W
  5. 5.0 5.1 5.2 Scorpius Constellation. constellation-guide.com. Retrieved on 2019-07-21.
  6. 6.0 6.1 6.2 6.3 Jim Kaler (2015-06-16). Girtab. Stars. stars.astro.illinois.edu. Retrieved on 2019-07-21.