An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A star that lies on the → rotation axis of the Earth in the north hemisphere. The → Pole Star is not, in the long term, permanently fixed to the → celestial pole. This is because of the Earth's → axial precession which gradually moves the celestial poles in the sky. It takes about 26,000 years for the precession to turn the pole a full circuit. Currently the North Pole Star is → Polaris, which will continue to mark the north celestial pole for several more centuries. But, around 4,000 B.C. → Gamma Cephei will become the North Pole Star. Around 7,500 B.C., → Alderamin will take up the role. And it will be the brilliant → Vega's (Alpha Lyrae) turn in about 12,000 years. In the past, about 3,000 B.C., → Thuban (Alpha Draconis) was the North Pole Star. Then → Kokab (Beta Ursae Majoris) became the Pole Star from 1500 B.C. to 500 A.D. before leaving the task to Polaris.

→ north; → pole; → star.