| celestial pole Either of the two points at which a northward or southward projection of the Earth's axis intersects the celestial sphere. The north and south celestial poles are analogous to Earth's geographic poles and are used in determining right ascension in the equatorial coordinate system. Depending on which hemisphere an observer is in, the stars and other celestial objects appear to revolve once around the north or south celestial pole every 24 hours, an effect produced by the rotation of the Earth on its axis. Because of the precession of Earth's axis, the celestial poles gradually shift position in the sky over a nearly 26,000-year cycle. |