Polaris, commonly known as the North Star, is a celestial beacon that has served as a guide for finding the direction of true north and establishing orientation in the night sky. Despite its fame, Polaris is not intensely bright; it ranks only about 48th in brightness among the stars visible from Earth, but its location makes it uniquely important.
Why Polaris is Unique
The significance of Polaris stems from its location almost directly above the North Celestial Pole (NCP), the imaginary point where Earth’s axis of rotation extends outward. Because of this alignment, Polaris appears almost stationary in the night sky, while all other northern stars seem to rotate around it in long, circular paths.
Polaris is currently less than one degree away from the true pole, meaning it traces only a very small circle as the Earth turns. This fixed position provides a reliable anchor point that always indicates the direction of true north, allowing a person to easily determine all other cardinal directions.
The Primary Method: Using the Big Dipper
The most dependable and widely taught technique for locating Polaris involves using the easily recognizable asterism known as the Big Dipper, which is part of the constellation Ursa Major. The Big Dipper consists of seven bright stars forming a large bowl and a handle. This grouping is circumpolar in most of the Northern Hemisphere, meaning it never sets below the horizon.
Once the Big Dipper is found, focus on the two stars that form the outer edge of its bowl, opposite the handle. These two stars, named Dubhe and Merak, are called the “Pointer Stars” because they align to point directly toward Polaris.
Draw an imaginary straight line starting from Merak, passing through Dubhe, and continuing outward from the bowl. Following this line will lead the eye to a moderately bright star that is Polaris. The distance to Polaris along this imaginary line is about five times the angular distance between the two Pointer Stars.
Polaris is the first star of moderate brightness encountered when extending this line. It is also the last star in the handle of the Little Dipper (Ursa Minor). If the Little Dipper is visible, seeing Polaris at the end of its handle confirms the correct star has been found.
Alternative Finding Methods
When the Big Dipper is too low in the sky or obscured by obstructions, the constellation Cassiopeia offers a reliable alternative. Cassiopeia is found on the opposite side of Polaris from the Big Dipper and is characterized by a distinctive pattern of five stars that form a prominent “W” or “M” shape. Like the Big Dipper, Cassiopeia is circumpolar and is always visible in the northern sky.
To use this constellation, focus on the three stars forming the middle segment of the “W” or “M.” These stars act like an arrow, as the central star points toward Polaris. Drawing a line that bisects the angle of the central star’s peak and extending it will lead the eye directly to the North Star.
Once a candidate star is identified using either method, its identity as Polaris can be confirmed by observing its lack of movement. While all other stars appear to drift due to the Earth’s rotation, Polaris will remain in essentially the same spot.