The north and south
celestial poles are the two imaginary points in the sky where the
Earth's axis of rotation, indefinitely extended, intersects the
celestial sphere. The north and south celestial poles appear permanently directly overhead to an observer at the Earth's
North Pole and
South Pole respectively. As the Earth spins on its axis, the two celestial poles remain fixed in the sky, and all other points appear to rotate around them, completing one circuit per day (strictly per
sidereal day).