Messier objects


M83 (Southern Pinwheel Galaxy)

M83 (Southern Pinwheel Galaxy), a barred-spiral galaxy 15.2 million light years away and the toughest Messier object, in my opinion     [Source]

The Messier Catalog is named after Charles Messier (1730 – 1817), a French astronomer with an interest in discovering comets. Collaborating with his assistant, Pierre Méchain (1744 – 1804), Messier made the decision to compile a catalog of “not comet” objects, as to not be confused during his comet searches. Ultimately, this list is what he became best known for, rather than his comet hunting. The Messier Catalog contains some of the sky’s finest showpieces and observing all of them is often considered a “rite of passage” for any beginning observer.

Charles Messier, ca. 1770

Charles Messier, ca. 1770

The final published version by Messier (in 1781) contained objects up to only M103. It wasn’t until after his death that astronomers decided to add an extra 7 entries, bringing the total to 110 objects, as it is today. These additional objects are ones that were found in his notes. Messier even listed M104 in his personal copy of the catalog, likely intending to include it in a later revision.

Messier's personal insignia

Messier’s personal insignia

The Messier Catalog is not without its peculiarities. Not all entries are even true deep sky objects! Such is especially the case with M40, a double star that Messier himself admitted to not seeing any associated nebulosity (erroneously reported to him by another observer, Johannes Hevelius). Others include M24, a large star cloud in the Milky Way, and M73, an insignificant asterism comprised of just four stars. Additionally, the inclusion of obvious naked eye objects—specifically the Orion Nebula, the Beehive Cluster, and the Pleiades, otherwise each known as M42, M44, and M45 respectively. It is thought these were added with the direct personal desire to “outdo” French astronomer Nicolas Lacaille’s (1713 – 1762) catalog of 42 southern hemisphere objects shortly before the Messier Catalog’s first publication in 1774 (then featuring 45 objects). Still yet, there also exists the curious exclusion of the Double Cluster—NGC 869 and 884—in the sword handle of Perseus.

M104 (Sombrero Galaxy)

M104 (Sombrero Galaxy), one of the finest galaxies in the Messier Catalog; from our vantage point, it appears nearly edge-on (only 6 degrees off its equatorial plane); it’s dust lane and large central bulge give it the appearance of a sombrero     [Source]

Out of all the 110 objects, there is only one to this day with an identity that is still considerably disputed: M102. It is thought by some (based on a letter by Messier’s assistant) that is merely a duplicate observation of M101. However, others contend that NGC 5866 is in fact M102. If nothing else, historical evidence suggests it quite possible that Messier himself did in fact observe NGC 5866 when searching for Méchain’s reported discovery of “M102”.


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