Charles Messier (June 26, 1730 – April 12, 1817) was a French astronomer most notable for publishing an astronomical catalog 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 (like himself) and other astronomical observers to distinguish between permanent and transient objects in the sky.
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 catalog is not scientifically organized by object type or by location (as the later New General Catalogue would be). Nonetheless, the Messier catalog 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 4 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 visited deep sky objects.
Many of the objects in the Messier catalog were discovered by his assistant Pierre Mechain.
The Messier crater on the Moon and the asteroid 7359 Messier were named in his honor.