Messier Objects and Numbers

So Who Was Charles Messier?

Charles Messier was a French astronomer who lived 1730-1817. He published an astronomical catalogue consisting of 110 galaxies, nebulae and faint star clusters, which came to be known as the Messier Objects. The purpose of the catalogue was to help astronomical observers distinguish between permanent and transient objects in the sky.

Messier's occupation as a comet hunter led him to continually come across fixed diffuse objects in the night sky which could be mistaken for comets. He compiled a list of them in collaboration with his friend and assistant Pierre Méchain (who may have found at least 20 of the objects), to avoid wasting time sorting them out from the comets they were looking for. The entries are now known to be 39 galaxies, 4 planetary nebulae, 7 other types of nebulae, and 55 star clusters.

Messier did his observing with a 100 mm (four-inch) refracting telescope from Hôtel de Cluny (now the Musée national du Moyen Âge), in Paris. The list he compiled only contains objects found in the area of the sky Messier could observe, from the north celestial pole to a declination of about −35.7° .

They are not organized scientifically by object type, or by location. The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, with only 17 of the 45 objects being Messier's. By 1780 the catalog had increased to 80 objects.

The final version of the catalogue was published in 1781, in the 1784 issue of Connaissance des Temps. The final list of Messier objects had grown to 103 objects. On several occasions between 1921 and 1966, astronomers and historians discovered evidence of another seven objects that were observed either by Messier or by Méchain, shortly after the final version was published. These seven objects, M104 through M110, are accepted by astronomers as being "official" Messier Objects.

The Messier designations from M1 to M110, are still used by professional and amateur astronomers today and their relative brightness makes them popular objects in the amateur astronomical community.

Here are some good Messier Objects to look out for:

• M42 - The Orion Nebula - can be seen with the naked eye, but even better with binoculars
• M31 - the Andromeda Galaxy- can only just be seen with the naked eye, but better with binoculars
• M45 - the Pleiades open star cluster - can be seen with the naked eye
• M13 - the Hercules Globular Cluster - needs a telescope
• M27 - the Dumbbell Nebula - needs a telescope