Wiktionary
n. An imaginary point situated where a planet's axis intersects the celestial sphere.
WordNet
n. one of two points of intersection of the Earth's axis and the celestial sphere [syn: pole]
Wikipedia
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).
The celestial poles are also the poles of the celestial equatorial coordinate system, meaning they have declinations of +90 degrees and −90 degrees (for the north and south celestial poles, respectively).
The celestial poles do not remain permanently fixed against the background of the stars. Because of a phenomenon known as the precession of the equinoxes, the poles trace out circles on the celestial sphere, with a period of about 25,700 years. The Earth's axis is also subject to other complex motions which cause the celestial poles to shift slightly over cycles of varying lengths; see nutation, polar motion and axial tilt. Finally, over very long periods the positions of the stars themselves change, because of the stars' proper motions.
An analogous concept applies to other planets: a planet's celestial poles are the points in the sky where the projection of the planet's axis of rotation intersects the celestial sphere. These points vary because different planets' axes are oriented differently (the apparent positions of the stars also change slightly because of parallax effects).
Celestial bodies other than Earth also have similarly defined celestial poles.
Usage examples of "celestial pole".
The constellations of Virgo and Libra were also dropping lower in the sky and, much farther to the north, I could see the Great and Little Bears slowly pacing out their eternal cycle around the celestial pole.
Nutation, or nodding, is a small but irregular movement that swings the celestial pole 10 seconds away from the smooth precessional circle every 18.
He thought he remembered that the south celestial pole of Mars was somewhere just off the Milky Way toward the Large Magellanic Cloud, but he could never find it.
At present Earth's celestial pole points to Polaris, but 4000 years ago it pointed at Deneb in Cygnus (the Egyptians painted pictures inside the pyramids showing Deneb as the North Star.
The celestial pole kept reeling around, past Deneb and Vega and through barren patches of sky around Hercules and Draco.
It was illegal, but I wanted my data-so I headed out at a right angle to the ecliptic, in the direction of the South Celestial Pole, approximately, and left Sol a billion miles behind me.
It was illegal, but I wanted my data - so I headed out at a right angle to the ecliptic, in the direction of the South Celestial Pole, approximately, and left Sol a billion miles behind me.
We are substantially closer to the Magellanic Clouds, so we must be nearer the southern celestial pole.
We are substantially closer to the Ma-gellanic Clouds, so we must be nearer the southern celestial pole.
We are substantially closer to the magellanic clouds, so we must be nearer the southern celestial pole.
We had no navigational instruments, relying on the dim triangle of stars that marked the south celestial pole.