POLE-STAB, or POLA RIS, the nearest conspicuous star to the north pole of the celes tial equator. The star which at the present time goes under the name of the " pole-star" is the star a 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-ster" is, however, a little less than le from the pole, and has a small but sensible motion round it. See Ponns. Owing to the motion of the pole of the celestial equator round that of the ecliptic (see PRECESSION OF THE EguncoxEs), 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 Ilipparehus n.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 a mid /3 (called the two pointers, from this peculiarity) of the constella tion Ursa Major, or the Great Bear, and produced northwards for about 4* times its Own length, will almost touch the pole-star. Two thousand years ago, the star fi of Ursa Major was the pole-star; and about 2,300 years before the Christian era, the star a 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.
The south pole of the celestial equator is not similarly marked by the near neighbor hood of a bright star, the only star deserving the name of the south pole-star being of the sixth or least visible magnitude.