The Pole Star (Polaris) is the brightest star in the constellation Ursa Minor. It is a visual double star. The companion with the apparent magnitude 9 mag at a distance of 18.4″ was discovered by Wilhelm Herschel in 1780.
The main star itself is a double star, which was not resolved optically until 2006 with the help of the Hubble Space Telescope. The two components are angularly separated by 0.17 arc seconds.
Due to its proximity to the poles (currently only about 0.7° from the north celestial pole), it has long been used as a free-eyed orientation and navigation aid. With its help one can roughly determine the direction to the geographic North Pole. To observers without a telescope, it seems to be in the same place all year round; its altitude in the sky corresponds approximately to the (northern) latitude at which the observer is located.
As a star with an apparent magnitude of 2, it does not catch the eye immediately, but can be easily found with the help of Ursa Major.
| Polaris | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 2h 31m 49s |
| Declination | +89° 15′ 51″ |
| Apparent magnitude | 1.97 mag |
| Distance | (431 ± 27) ly |
| Bayer designation | α Ursae Minoris |
| Bright Star Catalogue | HR 424 |
| Hipparcos Catalogue | HIP 11767 |
| SAO Catalogue | SAO 308 |
