Spotting the Messier Catalog and Other Sky Objects

By Stephen P. Maran

Naming stars was easy enough for astronomers. But what about all those other objects in the sky — galaxies, nebulae, star clusters, and the like? Charles Messier (1730–1817), a French astronomer, created a numbered list of about 100 fuzzy sky objects. His list is known as the Messier Catalog, and now when you hear the Andromeda Galaxy called by its scientific name, M31, you know that it stands for number 31 in the Catalog. Today 110 objects make up the standard Messier Catalog.

You can find pictures and a complete list of the Messier objects at The Messier Catalog website of Students for the Exploration and Development of Space. And you can find out how to earn a certificate for viewing Messier objects from the Astronomical League Messier Program website.

Experienced amateur astronomers often engage in Messier marathons, in which each person tries to observe every object in the Messier Catalog during a single long night. But in a marathon, you don’t have time to enjoy an individual nebula, star cluster, or galaxy. Take it slow and savor their individual visual delights. A wonderful book on the Messier objects, which includes hints on how to observe each object, is Stephen James O’Meara’s Deep-Sky Companions: The Messier Objects, 2nd Edition (Cambridge University Press).

Since Messier’s time, astronomers have confirmed the existence of thousands of other deep sky objects, the term amateurs use for star clusters, nebulae, and galaxies to distinguish them from stars and planets. Because Messier didn’t list them, astronomers refer to these objects by their numbers as given in other catalogues. You can find many of these objects listed in viewing guides and sky maps by their NGC (New General Catalogue) and IC (Index Catalogue) numbers. For example, the bright double cluster in Perseus, the Hero, consists of NGC 869 and NGC 884.