Polaris, also known as the North Star, was first noticed in the Middle Ages—a seemingly stationary star in an ever-changing night sky. In Norse tales, Polaris was believed to be the end of a spike that the sky rotates around. In Mongolian mythology, it was seen as a peg that holds the world together. Though not extraordinarily bright, Polaris’s unique unchanging position has made it the most useful star in the sky, helping explorers navigate on both land and sea for centuries.