The Ancient Chinese astronomers divided the sky, with the Polestar as the center, into three enclosures and 28 constellations. The former include the Purple Forbidden, Supreme Palace and Heavenly Market enclosures. The Purple Forbidden Enclosure covers the region around the Polestar. The ancient Chinese believed that it was fixed in the sky as a center around which all stars rotate. Therefore, the Polestar was called the Emperor Star, and the Purple Forbidden Enclosure was believed to be the place where the Heavenly Emperor lived.