polaris

Polaris is a star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris (Latinized to Alpha Ursae Minoris) and is commonly called the North Star or Pole Star. With an apparent visual magnitude that fluctuates around 1.98, it is the brightest star in the constellation and is readily visible to the naked eye at night. The position of the star lies less than a degree away from the north celestial pole, making it the current northern pole star. Historically, the stable position of the star in the northern sky has made it useful for navigation.
The revised Hipparcos parallax gives a distance to Polaris of about 433 light-years (133 parsecs), while calculations by some other methods derive distances up to 35% closer.
Although appearing to the naked eye as a single point of light, Polaris is a triple star system, composed of the primary, a yellow supergiant designated Polaris Aa, in orbit with a smaller companion, Polaris Ab; the pair is in a wider orbit with Polaris B. The outer pair AB were discovered in August 1779 by William Herschel.

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