Polaris (pōlâr`ĭs) or North Star, star nearest the north celestial pole (see equatorial coordinate system equatorial coordinate system, the most commonly used astronomical coordinate system for indicating the positions of stars or other celestial objects on the celestial sphere . The celestial sphere is an imaginary sphere with the observer at its center.
..... Click the link for more information. ). It is in the constellation Ursa Minor (see Ursa Major and Ursa Minor Ursa Major (ûr`sə) and Ursa Minor [Lat.
..... Click the link for more information. ; Bayer designation Alpha Ursae Minoris) and marks the end of the handle of the Little Dipper. Polaris's location less than 1° from the pole (1992 position R.A. 2^h23.3^m, Dec. +89°14') makes it a very important navigational star even though it is only of second magnitude; it always marks due north from an observer. Polaris can be located by following the line upward from the two stars (the Pointers) at the right end of the bowl of the Big Dipper or, if the Big Dipper is not visible, by following the line through the left side of the square in Pegasus through the end star in Cassiopeia. The star is a Cepheid variable Cepheid variables (sē`fēĭd), class of variable stars that brighten and dim in an extremely regular fashion.
..... Click the link for more information. and oscillates in brightness roughly every four days. Because of the precession of the equinoxes precession of the equinoxes, westward motion of the equinoxes along the ecliptic . This motion was first noted by Hipparchus c.120 B.C. The precession is due to the gravitational attraction of the moon and sun on the equatorial bulge of the earth, which causes the
..... Click the link for more information. , Polaris will not remain the polestar indefinitely; in 2300 B.C. the polestar was in the constellation Draco Draco [Lat.,=the dragon], northern constellation lying SE of Ursa Minor and N of Lyra and Hercules. It is traditionally depicted as a dragon. Draco contains the bright star Eltanin (Gamma Draconis). Thuban (Alpha Draconis) was the polestar 5,000 years ago, i.e.
..... Click the link for more information. , and by A.D. 12,000 the star Vega Vega (vā`gə), brightest star in the constellation Lyra ; Bayer designation Alpha Lyrae; 1992 position R.A. 18^h36.
..... Click the link for more information. in the constellation Lyra will be the polestar.

Polaris

or North Star

Earth's present northern polestar (the star visible from the Northern Hemisphere toward which Earth's axis points), at the end of the “handle” of the Little Dipper in the constellation Ursa Minor. Polaris is actually a triple star, composed of a binary star and a Cepheid variable. Precession of Earth's axis made the star Thuban, in the constellation Draco, the North Star in ancient Egyptian times; it will cause the North Pole to point toward Vega, in the constellation Lyra, 12,000 years from now.

Polaris [pə′lar·əs]

(astronomy)

A creamy supergiant star of stellar magnitude 2.0, spectral classification F8, in the constellation Ursa Minor; marks the north celestial pole, being about 1° from this point; the star Ursae Minoris. Also known as North Star; Pole Star.

Polaris (redirected from Polaris Borealis)

Polaris

Polaris
(redirected from Polaris Borealis)