Thuban, Alpha Draconis, North Pole Star

Thuban, Alpha Draconis, North Pole Star

The North Star has historically been used for navigation since Late Antiquity, both to find the direction of north and to determine latitude. Due to the precession of the equinoxes, the role of North Star passes from one star to another. In 3000 BC the faint star Thuban in the constellation Draco was the North Star. Thuban is an Arabic word for snake. It was the naked eye star closest to the north pole from 3942 BC until 1793 BC. It was closest to the pole in 2787 BC, when it was less than two and a half arc-minutes away from the pole. It remained within one degree of true north for nearly 200 years afterwards, and even 900 years after its closest approach, was just five degrees off the pole. Thuban was considered the pole star until about 1900 BC, when the much brighter Kochab began to approach the pole as well.

Album / Science Source / New York Public Library

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3900 x 4482 px | 50.0 MB

33.0 x 37.9 cm | 13.0 x 14.9 in (300 dpi)