circumpolar star

A star which never sets when viewed from a particular location. In Europe and North America the stars of Ursa Minor and Ursa Major are always visible. In Australia, Crux is a circumpolar constellation.

Circumpolar stars are those stars which are located near the celestial poles of the celestial sphere, i.e. Some of the circumpolar stars nearest the poles do not seem to engage in diurnal motion at all.

Such a definition implies that different stars can be defined as circumpolar at different Earth latitudes. For example, to an observer placed right at the Earth's North or South Pole, virtually all the stars are circumpolars. For an observer exactly on the equator, no star can be defined circumpolar, as the pole itself is on the horizon.

On the northern hemisphere all circumpolar stars rotate around the North Star Polaris, which itself is almost stationary, always at the north (i.e., the azimuth is 0°), and always at the same altitude (angle from the horizon), equal to the latitude of the point of observation on Earth.