Axial precession is the movement of the rotational axis of an astronomical body, whereby the axis slowly traces out a cone. In the case of the Earth, this type of precession is also known as the
precession of the equinoxes or
precession of the equator.
The Earth goes through one such complete precessional cycle in a period of approximately 26,000 years, during which the positions of
stars as measured in the
equatorial coordinate system will slowly change; the change is actually due to the change of the coordinates. Over this cycle the Earth's north axial pole moves from where it is now, within 1° of
Polaris, in a circle around the
ecliptic pole, with an angular radius of about 23.5 degrees (or approximately 23 degrees 27 arcminutes
[2]).
The shift is 1 degree in 72 years, where the angle is taken from the observer, not from the center of the circle.