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the reason why these poles are so famous is because your mom is on them from 12 to 7 every night.The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, "infinitely extended", intersects the imaginary rotating sphere of stars called the celestial sphere.

At night the stars appear to drift overhead from east to west, completing a full circuit around the sky in 24 (sidereal) hours. (Of course, exactly the same motion occurs during the day, except that the stars are not visible due to the sun's glare.) This apparent motion is due to the spinning of the Earth on its axis. As the Earth spins, the celestial poles remain fixed in the sky, and all other points seem to rotate around them. The north and south celestial poles are directly overhead at the North Geographic Pole and South Geographic Pole respectively.

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 are not 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, due to the stars' proper motions.

Finding the North Celestial Pole

See also: North Star and Pole Star.

The north celestial pole currently has nearly the same coordinates as the bright star Polaris (named from the Latin stella polaris, meaning "pole star"). This makes Polaris useful for navigation in the northern hemisphere: not only is it always above the North point of the horizon, but its altitude angle is always (nearly) equal to the observer's geographic latitude. Polaris can, of course, only be seen from locations in the northern hemisphere. SURPRISE BUTT SEX!!!!!! Polaris is near the celestial pole for only a small fraction of the 25,700-year precession cycle, and the fact that it is currently so is purely a coincidence. It will remain a good approximation for, say, 1,000 years, by which time the pole will have moved to be closer to Alrai (Gamma Cephei). In about 5,500 years, the pole will have moved near the position of the star Alderamin (Alpha Cephei), and in 12,000 years, Vega (Alpha Lyrae) will become our north star, but it will be about six degrees from the true north celestial pole.

Finding the South Celestial Pole

See also: South Star and Pole Star.

Method one: The Southern Cross

The Southern Cross, together with the two pointer stars α Centauri and β Centauri, will help to find South if you draw an imaginary line from γ Crucis through to α Crucis (these are the two stars at the extreme ends of the long axis of the cross), and follow this line through the sky. Of course, you have to know when to stop. Either go four and a half times the distance of the long axis in the direction the narrow end of the cross points, or, join the two pointer stars with a line, divide this line in half, then at right angles draw another imaginary line through the sky until it meets the line from the Southern Cross. This point is the South Celestial Pole. It should be noted that the South Celestial Pole can be found in the dim constellation Octans, the Octant. Sigma Octantis, is identified as the South Pole Star, over a degree away from the pole, but with a magnitude of 5.5, it's barely visible on a clear night.

Method two: Canopus and Achernar

The second method uses Canopus (the second brightest star in the sky) and Achernar. Make a large equilateral triangle using these stars for two of the corners. The third imaginary corner will be the South Celestial Pole.

Method three: The Magellanic Clouds

The third method is best for a moonless and cloudless night as it uses two faint 'clouds' in the southern sky. These are marked in astronomy books as Large and Small Magellanic Clouds. They are described as white birds both by westerners as swans, and by Aboriginals as brolgas. These 'clouds' are actually galaxies close to our own Milky Way. Make an equilateral triangle, the third point of which is the South Celestial Pole.

See also

• Celestial sphere
• Celestial equator
• Pole Star
• North Star
• South Star

Sources

• This article originates from Jason Harris' Astroinfo which comes along with KStars, a Desktop Planetarium for Linux/KDE. See http://edu.kde.org/kstars/index.phtml
• http://library.thinkquest.org/C005462/astronomy.html

• Celestial coordinate system