Polaris is the north star. In the night sky, the other stars circle it during the course of the night. Only Polaris stays in one place through the evening.
If you are a religious person, you can easily find some divine beauty in the passing of the stars. To me it seemed like the most perfect and pristine motion, and yet also the most massive motion I could comprehend. The original idea of the poem was to compare that heavenly pattern with ever-lesser patterns, made by ever-lesser life forms, here on Earth.