June 26: Charles Messier

Charles Messier

June 26, 1730 – April 12, 1817

Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 103 "Messier objects". The purpose of the catalogue was to help comet hunters, as he was, and to help other astronomical observers to distinguish between permanent and transient objects in the sky.

Charles' interest in astronomy was stimulated by the appearance of the spectacular, great six-tailed comet in 1744 and by an annular solar eclipse visible from his hometown on July 25, 1748.

In 1751 he entered the employ of Joseph Nicolas Delisle, the astronomer of the French Navy, who instructed him to keep careful records of his observations. Messier's first documented observation was that of the Mercury transit of May 6, 1753.

In 1764, he was made a fellow of the Royal Society, and on June 30, 1770, he was elected to the French Academy of Sciences. Messier discovered thirteen comets

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. The final version of the catalogue was published in 1781, in Connoissance des Temps for 1784. The final list of Messier objects had grown to 103.

On several different occasions between 1921 and 1966, astronomers and historians discovered evidence of another seven deep-sky objects that were observed either by Messier or his friend and assistant, Pierre Mechain, shortly after the final version was published. These seven objects, M104 through M110, are accepted by astronomers as "official" Messier objects.

The objects' Messier designations, from M1 to M110, still are in use by professional and amateur astronomers today.

The catalogue is not organized scientifically by object type or by location, as the later New General Catalogue would be. Nonetheless, the Messier catalogue comprises examples of every known deep sky object, including galaxies, planetary nebulae, open clusters, and globular clusters. Because these objects were accessible to the relatively small-aperture telescope (approximately 102 mm, or four inches) used by Messier to study the sky, they are among the most spectacular deep sky objects available to modern amateur astronomers using much better equipment. Furthermore, almost all of the Messier objects are among the closest to our planet in their respective classes, which makes them heavily studied with professional class instruments that today, can resolve very small and visually spectacular details in them. Professional astronomers still refer to objects by their Messier designation, and in amateur astronomy they are among the most frequently observed deep sky objects.

Many of the objects in the Messier catalogue were discovered by his assistant, Pierre Mechain.

The crater Messier on the Moon and the asteroid 7359 Messier were named in his honor.