Polaris
Star
Facts
- Distance
- about 520 light-years (NASA in 2006: about 430)
- Spectral class
- F7 Ib-II
- Diameter
- about 54 times the Sun
- Distance from the north celestial pole
- 0.74° (in 2000)
Polaris, the North Star, is a yellow supergiant of spectral class F7 Ib-II, less than a degree from the north celestial pole: according to NASA it shines more than 2000 times as brightly as the Sun. It is actually a system of three stars, and the main one is the Cepheid closest to us.
Cepheids change brightness in a regular way and are used to measure the distances of galaxies and the expansion of the universe. The Hubble telescope was the first to see directly its closest companion, about 3 billion km from the main star.