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Etamin, Zenith Star, Gamma Draconis, 33 Draconis

Proper NamesEltanin, Etamin, Zenith Star
Bayer DesignationGamma Draconis
Flamsteed Number33 Draconis
HR (BSC)6705
Right Ascension17h 56m 36s
Declination+51° 29' 20"
Distance154 light years
47 parsecs
MagnitudeApparent: +2.2
Absolute: -1.1
Spectral ClassK5III orange giant
Optimum VisibilityJuly (Usually visible from northern latitudes)

The constellation of Draco represents the long sinuous form of a Dragon twisting around the Northern Celestial Pole, and in its southeastern regions a quadrangle of stars combine to represent the Dragon's head, lunging southwards towards Hercules. The brightest of these four stars is orange Eltanin. The nearby constellation of Lyra forms a useful pointer to the head of the Dragon; a line from Lyra's star Sulafat through brilliant Vega points northwestward towards Eltanin in Draco.

The names Eltanin and its variant Etamin derive from the Arabic for 'great serpent', reflecting this star's prominence in the constellation of Draco. Despite its 'Gamma' designation, it is the in fact the brightest of the Dragon's stars, outshining both Alpha Draconis (or Thuban) and Beta Draconis (Rastaban, also called Alwaid, which lies close by Eltanin in the Dragon's head formation).

Physically Eltanin is an orange giant star, nearly fifty times the Sun's diameter but rather cooler, giving it a distinctive red-orange colour. There are strong indications that Eltanin has a companion star of the red dwarf classification. Designated Gamma Draconis B, this tiny companion appears to orbit the main giant at a distance just under 1,000 AU (or more than thirty times the distance of Neptune from the Sun).

Eltanin currently lies more than 150 light years from the Solar System, but the relative motions of this star and the Sun through the Galaxy are gradually bringing them closer together. The nearest approach will be in about 1.5 million years, when Eltanin will be less than thirty light years from the Sun, and will shine as one of the brightest stars in the skies of Earth.


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