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Dragon, constellation of the northern sky, consists of a long row of the modest splendor of stars that lies between Ursa Major and the Minor.
The dragon is a northern constellation. It is one of the 88 modern constellations and was also one of the 48 constellations listed by Ptolemy. The Latin poet Virgil calls this Anguis constellation in his book of the Georgics: “Up here [on the north pole astronomical] slips the Serpent with its sinuous folds and like a river flows around and in between the two Bears …”. That the Dragon is one of the largest constellations of the sky; It looks completely up to the circumpolar boreal temperate latitudes, such as the regions of the Mediterranean basin. The head of the group is represented by four stars, the brightest of which are Eltanin and Rastaban calls: the first has a great historical importance, since it was by measuring the parallax of this star that James Bradley discovered in 1725 the phenomenon of aberration of light, which constitutes one of the first evidence of the rotation of the Earth around the sun.
The rest of the constellation winds around the north celestial pole, insinuating itself between Ursa Major and Ursa Minor, surrounding it on the east, south, and west; the stars of the Dragon outside of the quadrilateral of the head are mostly of third and fourth magnitude, organized in alignments. About 2700 years ago the north celestial pole was located in the direction of this constellation and in particular in the part of the tail, the height of the star Thuban, which was then considered to be the North Star.
Eltanin is an orange giant star of magnitude 2.23, that is 148 years light. η Draconis is a yellow star of magnitude 2.73, that is 88 years light. Rastaban is a yellow star of magnitude 2.79 is 361 years light. δ Draconis is a yellow star of magnitude 3.07 is 100 years light. Among the other stars, we note Thuban, which was the north polar star around 2700 BC Arrakis is a binary system whose components are two stars that orbit almost identical at close range.
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