Al Dhanab (Gamma Gruis) is a blue giant star that can be located in the constellation of Grus. It is the 62nd brightest star in the night sky. Gamma Gruis is the Bayer Classification for the star. HIP108085 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD207971.
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 Al Dhanab, the location is 21h 53m 55.65 and -37d21`53.4 .
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 -013.22 ± 000.37 towards the north and 098.07 ± 000.67 east if we saw them in the horizon.
Al Dhanab has a spectral type of B8III. This means the star is a blue giant star. The star has a B-V Colour Index of -0.08 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 11,099 Kelvin.
Al Dhanab has been calculated as 3.95 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,746,816.52.km.
Al Dhanab has an apparent magnitude of 3.00 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 -0.97 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.06. 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.
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 16.07 which gave the calculated distance to Al Dhanab as 202.96 light years away from Earth or 62.23 parsecs. It would take a spaceship travelling at the speed of light, 202.96 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 15.45 which put Al Dhanab at a distance of 211.11 light years or 64.72 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 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.
|Traditional Name||Al Dhanab|
|Bayer Designation||Gamma Gruis|
|Hipparcos Library I.D.||108085|
|Henry Draper Designation||207971|
|Star Type||giant star|
|Absolute Magnitude||-0.97 / -1.06|
|Right Ascension (R.A.)||21h 53m 55.65|
|1997 Distance from Earth||16.07 Parallax (milliarcseconds)|
|202.96 Light Years|
|2007 Revised Distance from Earth||15.45 Parallax (milliarcseconds)|
|211.11 Light Years|
|Proper Motion Dec.||-13.22 ± 0.37 milliarcseconds/year|
|Proper Motion RA.||98.07 ± 0.67 milliarcseconds/year|
|Brightest in Night Sky||62nd|
|Radius (x the Sun)||3.95|
|Calculated Effective Temperature||11,099 Kelvin|