Why does the night sky look a bit different after 100 years?

Question

I am using Heavens Above interactive Skychart and noticed that if you move the year by 100 year increments, the night sky changes, but not so much. What causes this?

In: Planetary Science

Answer 1

One main cause [axial precession](https://en.wikipedia.org/wiki/Axial_precession), i.e. the Earth’s axis wobbles a bit and so from year to year a point on the earth’s surface is not oriented the same way in relation to the sky.

One big effect of his is the movement of the celestial poles. In about 3000 years Polaris will no no longer be the star closest to the northern celestial pole and will have to give up the title of pole star to Gamma Cephei.