Hipparchus first estimated the precession of the Earth's axis around 130 B.C. The period of precession is about 26,000 years.
While the Pole Star in the northern hemisphere is now Polaris, in 3000 B.C., the north celestial pole coincided with Thuban, a star in the constellation of Draco. In 14,000 A.D. Vega, in Lyra, will be the northern pole star.
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