The Messier Catalog, sometimes known as the Messier Album or list of Messier objects, is one of the most useful tools in the astronomy hobby. In the middle of the 18th century, the return of Halley's comet helped to prove the Newtonian theory, and helped to spark a new interest in astronomy. During this time, a French astronomer named Charles Messier began a life-long search for comets. He would eventually discover 15 of them. On August 28, 1758, while searching for comets, Messier found a small cloudy object in the constellation Taurus. He began keeping a journal of these nebulous (cloudy) objects so that they would not be confused with comets. This journal is known today as the Messier Catalog, or Messier Album. The deep sky objects in this catalog are commonly referred to as Messier objects.