The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy 21 million light-years (6.4 megaparsecs) away from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781[a] and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one of its final entries.