Pole star

Star Trail above Beccles - geograph.org.uk - 1855505

A method to find Polaris at 5x the distance of Merak and Dubhe of Ursa Major

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Precession S

Earth precession

File:South Celestial Pole.ogv Pole star or polar star refers to a star, particularly a bright one, that is situated approximately in line with the Earth's axis of rotation. This means that as the Earth rotates, the pole star appears to remain stationary in the sky, while other stars seem to rotate around it. This characteristic makes the pole star an important navigational aid, especially before the advent of modern navigation technologies.

History

The concept of a pole star has been known since ancient times. Different stars have served as the pole star throughout history due to the phenomenon of precession of the equinoxes, which is the gradual shift in the orientation of the Earth's axis of rotation. The current northern pole star is Polaris, located in the constellation of Ursa Minor. Polaris is relatively close to the North Celestial Pole, making it an excellent fixed point for navigation in the Northern Hemisphere. In contrast, the Southern Hemisphere does not have a bright star located close to the South Celestial Pole, making southern celestial navigation more challenging.

Polaris

Polaris, also known as the North Star, has not always been the pole star and will not be forever. Due to the precession of the equinoxes, the role of the North Star passes from one star to another. Approximately 12,000 years ago, the star Vega in the constellation Lyra was the North Star. In about 13,000 years from now, Vega will return to this position again. Polaris has been a pivotal navigational star for mariners and explorers for centuries, owing to its almost fixed position in the northern sky.

Navigation

Before the widespread availability of the compass and later, sophisticated navigational instruments, sailors and travelers relied heavily on the stars for navigation. The pole star's unique position made it an invaluable tool for determining direction at night. By finding Polaris, navigators could easily determine true north, which is essential for accurate navigation. This method is still taught in basic navigation courses as a survival skill.

Cultural Significance

The pole star has held a place of significance in various cultures and mythologies. Many ancient civilizations, including the Greeks, Egyptians, and Polynesians, had myths and legends surrounding the pole star and its role in the heavens. It often symbolized constancy and reliability due to its unchanging position in the sky.

Future

As the Earth continues its precessional motion, the identity of the pole star will change. In the distant future, other stars will take on the role of the North Star. The Southern Hemisphere will also see changes in its near-polar stars, although none as prominent as Polaris in the northern celestial sphere.

See Also

• Celestial navigation
• Astronomy
• Constellation
• Precession of the equinoxes
• Ursa Minor