Pole-star, or POLARIS, the nearest conspicuous star to the north pole of the celestial equator. The star which at the present time goes under the name of the 'pole-star' is the star in the constellation of Ursa Minor. By examining attentively the general movement of the stars throughout a clear winter's night, we observe that they describe circles which are largest at the equator, and become smaller and smaller as we approach a certain point (the north pole of the celestial equator), close to which is the star above mentioned. This 'pole-star' is, however, a little less than 1½° from the pole, and has a small but sensible motion round it. Owing to the motion of the pole of the celestial equator round that of the ecliptic (see PRECESSION), this star will in course of time (about 2100 A.D.) approach to within 28' from the north pole, and will then recede from it. At the time of Hipparchus (156 B.C.) it was 12°, and in 1785 2° 2' from the north pole. Its place can easily be found in the heavens, for a line drawn between the stars and (called the two pointers, from this peculiarity) of the constellation Ursa Major, or the Great Bear, and produced northwards for about 4½ times its own length, will almost touch the pole-star. Two thousand years ago the star of Ursa Minor was the pole-star; and about 2300 years before the Christian era the star in the constellation of the Dragon was not more than 10' from the north pole; while 12,000 years after the present time the bright star Vega in Lyra will be within 5° of it. See star-map at URSA MAJOR.
The south pole of the celestial equator is not similarly marked by the near neighbourhood of a bright star, the only star deserving the name of the south pole-star being of the sixth or least visible magnitude.