Messier 3 (M3) – the NGC 5272 globular cluster

During the late 18th century, Charles Messier began to notice a series of "nebulous" objects in the night sky which he originally mistook for comets. With the hope of preventing other astronomers from making the same mistake, he began compiling a list of these in what would come to be known as the Messier Catalog. Consisting of 100 objects, the catalog became an important milestone in the discovery and research of Deep Sky objects.