Stellar precession is one of the ways the stars slowly move across the sky when seen from the Earth. The best-known thing this causes is making the north star's place in the sky slowly change over thousands of years. It is caused by the Sun's gravity pulling the Earth's poles toward itself. Because the Earth's poles are tilted at an angle of 23.42 degrees from straight up in relation to its orbit, this causes the North Pole to seem to point at different places in the sky. While the orientation of the Earth with respect to the stars changes, the axial tilt remains constant. 