“Messier” refers to the Messier Catalogue, a list of 110 deep sky objects (such as galaxies, nebulae, and star clusters) compiled by French astronomer Charles Messier in the 18th century. The purpose of the catalogue was to help astronomers differentiate between permanent and transient objects in the sky that could be mistaken for comets. Today, the Messier Catalogue is still widely used by amateur astronomers as a guide to observing deep sky objects.