...of the Earth's
The Earth's rotation
axis is not fixed in space.
Like a rotating toy top, the
direction of the rotation axis executes a slow precession with a
period of 26,000 years (right figure).
Pole Stars are Transient
Thus, Polaris will not always be the Pole Star or
The Earth's rotation axis happens to be pointing almost exactly
at Polaris now, but in 13,000 years the precession of the
rotation axis will mean that the bright star Vega in the
constellation Lyra will be approximately at the North Celestial
Pole, while in 26,000 more years Polaris will once again be the
Precession of the Equinoxes
Since the rotation
axis is precessing in space, the orientation of the Celestial
Equator also precesses with the same period.
This means that the
position of the equinoxes is changing slowly with respect to the