Ursa Minor, the Little Bear and the Pole Star

Ursa Minor, the Little Bear, is a northern constellation, one of Ptolemy's forty-eight, of lasting importance because it contains Polaris, the North Star, at the tip of its tail. Polaris lies very near the north celestial pole, so that the whole sky appears to wheel around it while it stays nearly fixed, making it a guide for navigation and direction for millennia. The seven main stars form a shape often called the Little Dipper. In Greek myth the two bears were linked to the nymph Callisto and her son, set in the sky by Zeus. In astronomical tradition the constellation is a star pattern rather than an astrological sign. These are the features of Ursa Minor as the classical and modern traditions describe it, distinct from the zodiac; its pole star has served travellers as a fixed point of reference through history.

Because Polaris was not always the pole star and will not remain so indefinitely, Ursa Minor's importance is really a passing accident of the twenty-six-thousand-year precessional cycle: some five thousand years ago the pole lay instead near Thuban in the neighbouring constellation Draco, and roughly twelve thousand years from now it will lie near Vega in Lyra, so the Little Bear's guiding role belongs to this particular era of that very long cycle rather than to any permanent property of the constellation itself.