Polaris, designated Alpha Ursae Minoris commonly the North Star or Pole Star, is the brightest star in the constellation of Ursa Minor. Polaris is a three star system comprising of the supergiant Polaris A and two smaller companions. The two companion stars, Polaris Ab and Polaris B, are both yellow-white dwarfs with similar surface temperatures to their giant neighbor. Polaris is the only star in the night sky that appears to remain stationary, this is because it is currently positioned above the northern axis of Earth's rotation.
As the star always points north it has been an aid to navigators for centuries, although it is only visible in the northern hemisphere. Polaris has been aligned above the North Pole for around 2,000 years but after 2100 Earth's northern axis will begin to move away from the star.
