Celestial Poles

The celestial poles are the two fixed points in the sky, one north and one south, that mark where an extension of Earth's own rotational axis meets the celestial sphere, and they are the points around which the entire sky appears to rotate over the course of a night due to Earth's own spin. The north celestial pole currently sits very close to the moderately bright star Polaris, which is why Polaris appears to barely move throughout the night while every other star seems to circle around it — a fact sailors and travelers have relied on for centuries to find true north. There is no equivalent bright star conveniently marking the south celestial pole, making it considerably harder for observers in the Southern Hemisphere to pinpoint by eye alone. Because Earth's axis very slowly wobbles over a roughly 26,000-year cycle called precession, the celestial poles are not perfectly fixed over long timescales; thousands of years ago the north celestial pole pointed toward a different star entirely, and thousands of years from now it will point near yet another one. An observer's own latitude on Earth determines how high the celestial pole appears above their horizon — at the North Pole it sits directly at the zenith, while at the equator it sits right on the horizon.