On Oct. 13, 1773, Charles Messier spotted the Whirlpool Galaxy (M51) for the first time. Writing of it a few months later, he described the object as a “very faint nebula without any stars”; it would become the 51st entry in his famous catalog of non-comets. In 1781, Messier’s friend and fellow astronomer Pierre Mechain Continue reading "Oct. 13, 1773: The discovery of the Whirlpool Galaxy" The post Oct. 13, 1773: The discovery of the Whirlpool Galaxy appeared first on Astronomy Magazine .