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Girtab, Kappa Scorpii, HD160578, HIP86670, HR6580

Girtab (Kappa Scorpii) is a blue pulsating giant star that can be located in the constellation of Scorpius. Girtab is the 83rd brightest star in the night sky and the 6th brightest star in Scorpius based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Kappa Scorpii is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR6580. HIP86670 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD160578.

Girtab has alternative name(s), kap Sco.

Girtab is a binary multiple star system. The main star is a Cepheid variable star which means in short that it pulsates, enlarging and shrinking due to internal stresses and forces. The primary star is about 7 times the raidus of the sun and has around about 17 times the mass of the Sun. The second star is about six times as big as the radius of the Sun and only about 12 times the mass. The beta star is still pretty big compared to the Sun. The smaller star orbits the larger one about every 196 days, just a bit over the same length of time Earth rotates round the Sun. The larger of the two stars has used by its hydrogren supply and is moving to the next stge of its evolutionary life cycle.1

Location of Girtab

The location of the star in the galaxy is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the star is compared to the celestial equator and is expressed in degrees. For Girtab, the location is 17h 42m 29.28 and -39d 01` 47.7 .

Proper Motion of Girtab

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving -25.54 ± 0.12 miliarcseconds/year towards the north and -6.05 ± 0.17 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Girtab

Girtab has a spectral type of B1.5III. This means the star is a blue giant star. The star is 7254.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23659.8889737600000000s. The star has a B-V Colour Index of -0.17 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 14,786 Kelvin.

Girtab Radius has been calculated as being 6.75 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,695,908.32.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 7.00. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Girtab Apparent and Absolute Magnitudes

Girtab has an apparent magnitude of 2.39 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, you would get an absolute magnitude of -3.38 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.46. Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

Distance to Girtab

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 7.03 which gave the calculated distance to Girtab as 463.96 light years away from Earth or 142.25 parsecs. It would take a spaceship travelling at the speed of light, 463.96 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

In 2007, Hipparcos data was revised with a new parallax of 6.75 which put Girtab at a distance of 483.20 light years or 148.15 parsecs. It should not be taken as though the star is moving closer or further away from us. It is purely that the distance was recalculated.

The star's Galacto-Centric Distance is 7,254.00 Parsecs or 23,659.89 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Girtab

The star is a pulsating Beta Cephei variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. Girtab brightness ranges from a magnitude of 2.319 to a magnitude of 2.312 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 days (variability).

Source of Information

The source of the information if it has a Hip I.D. is from Simbad, the Hipparcos data library based at the University at Strasbourg, France. Hipparcos was a E.S.A. satellite operation launched in 1989 for four years. The items in red are values that I've calculated so they could well be wrong. Information regarding Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Girtab Facts

Alternative Names

Traditional/Proper NameGirtab
Short Namekap Sco
Bayer DesignationKappa Scorpii
Hipparcos Library I.D.86670
Yale Bright Star Catalogue (HR) Id6580
Henry Draper Designation160578

Visual Facts

Star Typegiant star
Absolute Magnitude-3.38 / -3.46
Visual / Apparent Magnitude2.39
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)17h 42m 29.28
Declination (Dec.)-39d 01` 47.7
Galactic Latitude-4.72 degrees
Galactic Longitude351.04 degrees
1997 Distance from Earth7.03 Parallax (milliarcseconds)
 463.96 Light Years
 142.25 Parsecs
2007 Revised Distance from Earth6.75 Parallax (milliarcseconds)
 483.20 Light Years
 148.15 Parsecs
Galacto-Centric Distance23,659.89 Light Years / 7,254.00 Parsecs
Proper Motion Dec.-25.54 ± 0.12 milliarcseconds/year
Proper Motion RA.-6.05 ± 0.17 milliarcseconds/year
B-V Index-0.17
Radial Velocity-14.00 ± 2.80 km/s
Spectral TypeB1.5III
Brightest in Night Sky83rd
Colour(B) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeBeta Cephei
Mean Variability Period in Days0.202
Variable Magnitude Range (Brighter - Dimmer)2.312 - 2.319

Estimated Facts

Calculated Effective Temperature14,786 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Girtab in Scorpius

Girtab (Kappa Scorpii) Location in Scorpius

The map was generated using Night Vision, an awesome free application by Brian Simpson.

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