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 Earth, this type of precession is also known as the precession of the equinoxes or precession of the equator. Earth goes through one such complete precessional cycle in a period of approximately 26,000 years. Over this cycle, 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.  Thus, while today the star Polaris lies approximately at the north celestial pole, this will change over time, and other stars will become the “north star”. The south celestial pole currently lacks a bright star to mark its position, but over time precession will also cause bright stars to become south stars. As the celestial poles shift, there is a corresponding gradual shift in the apparent orientation of the whole star field, as viewed from a particular position on Earth.

The angle between Earth’s rotational axis and the normal to the plane of its orbit (obliquity) oscillates between 22.1 and 24.5 degrees on a 41,000-year cycle. It is currently 23.44 degrees and decreasing.