The Messier Objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his Catalogue des Nébuleuses et des Amas d’Étoiles. Interestingly, Charles Messier was actually fascinated with finding comets, which meant that to avoid confusing these celestial discoveries with comets. he created a list of non-comet objects. This work was not done alone, as his assistance Pierre Méchain was there to assist with compilation and collaboration during this time.

When performing these observations and compilation of these objects, Messier worked at the Hôtel de Cluny, in Paris, France. If you’re interested in visiting the site where Messier did most of his work, please note that its is now called the Musée national du Moyen Âge. As Messier was working from Paris, France, the objects in the list contains things that could be found in the sky area observable from Paris. This equates to the area that spans from the north celestial pole to a celestial latitude of about −35.7°. This is important to note because Messier did not include and did not observe or list objects visible only from farther south than Paris.

It is worth noting that the Messier catalogue comprises nearly all the most spectacular examples of the five different deep-sky object types that are visible from latitudes in Europe. What is even more interesting is that these objects are amongst the closest to Earth for each category of deep sky object, which has allowed scientists to study these objects.

An early first appeared in the Memoirs of the French Academy of Sciences in 1771, which contained 45 objects. It is worth noting that 18 of these initial 45 objects were discovered by Messier, the rest being previously observed by other astronomers. By 1780 the number of objects in the catalogue had increased to 80, with the final version of the catalogue increasing to 103 when published.

Today, these objects are very popular with many amateur astronomers! This can be in part due to the objects being visible in the Northern Hemisphere and can be observed visually with the relatively small-aperture refracting telescope of 4 inches as a minimum size. As Messier himself used a small telescope of similar size when performing such calculations, these stellar objects are quite popular.

For many amateur astronomers, many of these objects are still referenced but their Messier numbers and are popular astrophotography targets. In early spring, astronomers sometimes gather for “Messier Marathons”, when astronomers see if they can view every star in the catalogue in 1 night.

Further Reading

https://www.nasa.gov/content/goddard/hubble-s-messier-catalog