Caption: An animation illustrating the axial precession of the Earth's axis.

The axial precession causes a westward or clockwise circular rotation of the north celestial pole (NCP) on the celestial sphere as seen from outside the celestial sphere looking down on the NCP.

Features:

1. The axial precession is caused by the Earth's axial rotation in combination with the tidal force (in order decreasing importance) the Moon, the Sun, and, to a much lesser degree, the other Solar-System bodies on the Earth's equatorial bulge (see Wikipedia: Axial precession: Cause) which are in turn caused by the Earth's axial rotation.

2. The period of the axial precession is ∼ 26,000 years.

3. The rate of axial precession is actually varying with time due various astronomical perturbations (see Wikipedia: Axial precession: Values). The astronomical perturbations are mainly gravitational perturbations including those due to the slow chaotic evolution of the Solar System and due to the somewhat chaotic internal motions of the Earth caused by plate tectonics and other processes driven by primordial-radiogenic heat geology.

   The astronomical perturbations make it impossible to predict the rate beyond a few thousand years to the past or the future.

   If the current rate is taken as constant, the period would be almost exactly 25,771.5 Julian years (Jyr) (see Wikipedia: Axial precession: Values). A Julian year is exactly 365.25 days.

   Since the current rate is NOT constant and the variation NOT fully predictable, ∼ 26,000 years is about the most accurate one can be.

   Also due to the astronomical perturbations, the period of axial precession will NEVER be exactly the same twice.

4. As you can see from the animation, Polaris (apparent V magnitude 1.98) is only the pole star of the north for awhile.

5. In Greco-Roman antiquity, the tail end of Ursa Minor was recognized as useful in approximating the NCP region, but the NCP was NOT strikingly close Polaris. Stobaeus (fl. 5th century CE) noted Polaris as a skymark of the NCP region, but the NCP was then still 8° away from Polaris. In Middle Ages, the NCP was noticeably closer to Polaris and Polaris was becoming more useful in navigation as the pole star. However, even in 1547, the NCP was still 3.8° from Polaris and Polaris was still only rather approximately the pole star of the north (see Wikipedia: Pole Star: History).

6. As of 2012 October, the NCP was ∼ 40 arcminutes from Polaris.

7. On 2100 Mar24, the NCP will make its closest apparent approach of ∼ 27 arcminutes to Polaris (see Wikipedia: Pole star: Precession of the equinoxes).

8. Circa year 4000 CE, NCP will make its closest approach of ∼ 2° to γ Cephei (apparent V magnitude 3.22) which will then lay a claim to being the pole star of the north.

9. Circa year 10,000 CE, NCP will make its closest approach of ∼ 5° to the bright star Deneb (apparent V magnitude 1.25) which will then lay a claim to being the pole star of the north.

   One wonders who will notice.