The North Star (Polaris): how to find it and why it never moves
How to find Polaris in two steps from the Big Dipper, why the whole sky turns around it, how sailors used it, and why it will not be the pole star forever.
Polaris is not the brightest star in the sky. It is only about the 48th brightest. What makes it special is its position: it sits less than a degree from the north celestial pole, the point in the sky directly above Earth’s North Pole. As Earth turns, every other star circles around it while Polaris stays put.
How to find it in two steps
- Find the Big Dipper (the Plough), the seven bright stars of Ursa Major. From Europe and most of North America it never sets, but it stands highest in spring evenings and lowest in autumn evenings.
- Follow the pointers. The two stars at the end of the Dipper’s bowl, Dubhe and Merak, point to Polaris. Go about five times the distance between them and you reach a moderately bright, lonely star. That is Polaris, at the tip of the Little Dipper’s handle.
If the Dipper is hidden, use Cassiopeia, the W-shaped constellation on the opposite side of Polaris. Polaris lies roughly between the two.
Why it never moves
Earth’s axis points almost exactly at Polaris. Stand at the North Pole and Polaris is overhead; at the equator it sits on the horizon. Its height above your horizon equals your latitude: about 60° in Oslo or Helsinki, 52° in Berlin, 45° in Minneapolis. Navigators used this for centuries to find their latitude with nothing but a sextant.
Long-exposure photos pointed at Polaris turn every other star into a circular trail around it. (Type polaris on this site to see a small version.)
It will not be the pole star forever
Earth’s axis slowly wobbles like a spinning top, tracing a circle in the sky every 26,000 years. This is called precession. Around 2100 Polaris will be at its closest to the pole, about 0.45°. Five thousand years ago, when the pyramids were built, the pole star was Thuban in Draco. In about 12,000 years it will be Vega, far brighter than Polaris.
The Southern Hemisphere has no bright pole star
The south celestial pole has only the faint Sigma Octantis, barely visible to the naked eye. Southern observers find the pole using the Southern Cross: extend its long axis about four and a half times towards the horizon.
What Polaris really is
Polaris is a yellow-white supergiant about 433 light years away, roughly 2,000 times brighter than the Sun. It is also a triple star system and a Cepheid variable whose brightness pulses slightly every four days. The light you see tonight left it around the year 1590.