What phenomenon causes the changes in the pole stars over time?

The phenomenon responsible for the changes in pole stars over time is axial precession. Axial precession is the gradual shift in the orientation of the Earth's rotational axis, caused primarily by gravitational forces exerted by the Sun and the Moon on Earth’s equatorial bulge.

As the Earth's axis wobbles, the position of the pole star changes over centuries. For instance, currently, Polaris is our North Star, but due to axial precession, in approximately 12,000 years, the star Vega will take its place as the North Star. This movement is a cyclic process that follows a path in the sky over a period of about 26,000 years, known as a complete precession cycle.

In contrast, axial tilt refers to the angle at which Earth's axis is tilted concerning its orbital plane, affecting seasons but not the identity of pole stars. The solar cycle is related to solar activity and does not influence the positioning of stars relative to Earth's axis. Galactic movement involves the motion of stars and solar systems within the Milky Way, but it does not account for the specific rotational motion of Earth that leads to the shifting of pole stars. Therefore, axial precession is the key mechanism driving the changes in pole stars over time.