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The two celestial poles are the imaginary points where the Earth's spin axis intersects the imaginary rotating sphere of "gigantic radius", called the celestial sphere. Earth is the current Good Article Collaboration of the week! Please help to improve this article to the highest of standards. ...
The axis of rotation of a rotating body is a line such that the distance between any point on the line and any point of the body remains constant under the rotation. ...
In astronomy and navigation, the celestial sphere is an imaginary rotating sphere of gigantic radius, concentric with the Earth. ...
At night ,the sky appears to drift overhead from east to west, completing a full circuit around the sky in 24 (sidereal) hours. This phenomenon is due to the spinning of the Earth on its axis. The Earth's spin axis intersects the celestial sphere at two points. These points are the celestial poles. As the Earth spins, they remain fixed in the sky, and all other points seem to rotate around them. 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). Sidereal time is time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical with, the motion of stars. ...
The equatorial coordinate system is probably the most widely used celestial coordinate system, whose equatorial coordinates are: declination () right ascension () or hour angle () It is the most closely related to the geographic coordinate system, because they use the same fundamental plane, and the same poles. ...
In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ...
The north celestial pole currently has nearly the same coordinates as the bright star Polaris (which is Latin for "Pole Star"). This makes Polaris useful for navigation: 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 (however, Polaris can only be seen from locations in the Northern hemisphere). Polaris (α UMi / α Ursae Minoris / Alpha Ursae Minoris) is the brightest star in the constellation Ursa Minor. ...
It has been suggested that History of the Latin language be merged into this article or section. ...
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Latitude, usually denoted symbolically by the Greek letter φ, gives the location of a place on Earth north or south of the Equator. ...
The fact that the star Polaris is near the pole is purely a coincidence. It will remain a good approximation case for say 1000 years, but, because of precession of the equinoxes, considering larger time scales, Polaris is only near the pole for a small fraction of the time(the time needed for human to name it so). Actually, Polaris will remain our north star for the next 1,000 years, at which time the pole will be closer to Alrai (Delta 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. Precession refers to a change in the direction of the axis of a rotating object. ...
Delta Cephei (δ Cep / δ Cephei) is a star in the constellation Cepheus. ...
Alderamin is the proper name of the star α Cephei in the constellation of Cepheus. ...
Vega (also known as Alpha Lyrae or 3 Lyrae) is a star approximately 25. ...
Finding the South Celestial Pole
Method one: The Southern Cross The Southern Cross, together with the two pointers Alpha and Beta Centauri will help to find South if you draw an imaginary line from Gamma Crux through to Alpha Crux, and follow this line through the sky. Of course, you have to know when to stop. You 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. Gacrux (γ Cru / γ Crucis / Gamma Crucis) is the third brightest star in constellation Crux (the Southern Cross) and one of the brightest stars in the nighttime sky. ...
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. Make an equilateral triangle, the third point of which is the South Celestial Pole.
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