Polaris, the current northern pole star

Polaris is a yellow supergiant in the northern circumpolar constellation of Ursa Minor. It is designated alpha Ursae Minoris and is commonly called the North Star. Its apparent magnitude fluctuates around 1.98, making it the brightest star in its constellation and readily visible to the naked eye on a clear night. The position of Polaris lies less than one degree from the north celestial pole, which makes it the current northern pole star and the basis for traditional northern-hemisphere field navigation.

Although it appears as a single point of light, Polaris is a triple star system. The primary, a yellow supergiant designated Polaris Aa, orbits a smaller companion called Polaris Ab; that pair is in a wider orbit with Polaris B. The outer companion B was discovered in August 1779 by William Herschel; the inner Aa/Ab pair was only confirmed in the early twentieth century. As the closest Cepheid variable to Earth, Polaris has been a foundational rung on the cosmic distance ladder. The revised Hipparcos parallax gives a distance of about 432 light-years (133 parsecs) to Polaris A, while the successor Gaia mission gives 446.5 light-years (136.9 parsecs) for Polaris B.

Polaris will not always be the pole star. Earth's axis precesses slowly, so the celestial pole drifts among the stars over a roughly 26,000-year cycle. Vega held the role around 12,000 BCE and is expected to resume it near the year 13,724. For the working lifetime of any current observer, Polaris remains within a degree of true north and is more than accurate enough for camp orientation, terrain navigation, and azimuth checks against a compass.