- The North Star, also known as Polaris or the Pole Star, is a bright star located in the constellation Ursa Minor.
- Polaris is approximately 323 light years away from Earth and appears to sit still in the northern sky due to its proximity to the north celestial pole.
Uses in Navigation
- The North Star has been used for navigation since ancient times, as the height of the star
- above the horizon can determine the observer’s latitude in the northern hemisphere.
- Columbus used Polaris to correct his ship’s bearings during his first trans-Atlantic voyage in 1492, making it an indispensable tool for European colonizers exploring new lands.
- However, Polaris is not visible in the southern hemisphere and is therefore not useful for navigation there.
Polaris and Earth’s Rotation
- Polaris is located close to the north celestial pole and is the imaginary line that extends through the planet and out of the north and south poles.
- Earth rotates around this line, like a spinning top, and Polaris is located quite close to the point in the sky where the north rotational axis points.
- As Earth rotates through the night, the stars around the pole appear to rotate around the sky, but Polaris traces out a very small circle over 24 hours and always stays in roughly the same place in the sky.
Finding the North Star
- Locating Polaris is easy on any clear night. Just find the Big Dipper and the two stars on the end of the Dipper’s “cup” point the way to Polaris, which is the tip of the handle of the Little Dipper or the tail of the little bear in the constellation Ursa Minor.
- Once you’re facing toward Polaris, you know you’re facing north, which can help you orient yourself any evening you’re out stargazing.
No North Star in the Southern Hemisphere
- The Southern Hemisphere doesn’t have a bright star that marks the south celestial pole, but observers there can use other clever ways to find due south, including using the stars of the Southern Cross constellation to point the way.
Wandering North Star
- One other note about the North Star is that it’s a title that passes to different stars over time.
- Earth’s axis of rotation wobbles over the course of about 26,000 years, causing the celestial pole to wander in a slow circle over the eons, sweeping past different stars.
- About 14,000 years ago, the celestial pole pointed toward the bright star Vega, and as it sweeps out its slow circle, it will again point to Vega in about 12,000 years.
In summation,
- The North Star, Polaris, is a bright star located in the constellation Ursa Minor and has been used for navigation since ancient times due to its close proximity to the north celestial pole.
- Polaris traces out a very small circle over 24 hours and always stays in roughly the same place in the sky, making it a reliable way to find the direction of north.
- Observers in the Southern Hemisphere can use other methods to find due south, and the North Star title passes to different stars over time due to Earth’s wobbling axis of rotation.
