The tower of the Hôtel de Cluny

The Museum of the Middle Ages (Musée National du Moyen Âge) in Paris is one of the most beautiful medieval buildings in the center of the Seine capital. Inside you can see the famous tapestry *"The lady and the unicorn".* However, few visitors notice the octagonal tower located in the entrance courtyard. Here the Messier Catalog was born, possibly the list of objects most appreciated by astronomy enthusiasts.

The first astronomer who settled in the tower was Joseph-Nicolás Delisle, member of the French Academy of Sciences. Delisle, despite coming from a wealthy family, did not have a fortune that would allow her to finance her research. In 1725 his life took an unexpected turn when he was called to St. Petersburg by Tsar Peter the Great to take over the creation of the astronomy school of the Russian Academy of Sciences. On his return to Paris in 1747, already rich and famous, he was able to set up his own observatory in a tower of the Hôtel de Cluny. The Hôtel de Cluny (called Clugny in the mid-eighteenth century) stands on the ruins of Roman baths of the fourth century, had belonged to the Benedictine order and, later, passed into the hands of the French Navy. Delisle reached the agreement to cede the observatory to the Royal Navy in exchange for being named "Astronomer of the Navy".

The tower of the Hôtel de Cluny from which Messier made his observations

Delisle was not part of the academic astronomical world, so he could devote himself to his own interests without having to attend to scientific obligations. Charles Messier was welcomed by the marriage Delisle, who had no offspring, as if he were his own son. The first tasks entrusted to the young astronomer were to copy maps by hand and record observation records. Delisle had calculated the trajectory of the comet Halley that should reappear in 1758, the search of the comet was the first purely astronomical task that faced Messier, who then had 28 years. Although Messier detected the comet on January 21, 1759, far from the position predicted by his master, a German farmer, Johann Georg Palitzsch, had advanced almost a month. To make matters worse, Delisle did not allow him to publish this independent discovery, since he did not accept that his calculations were erroneous and when he had no choice but to accept the obvious, it had already been too long and the French astronomical community did not believe Messier, something that would weigh him for many years.

Charles Messier at the age of 40 years portrayed by Nicolas Ansiaume

The search for comets became an obsession for Messier, he was the first comet hunter in history. In 1758, when he was looking for a body discovered by Jean Baptiste François de la Nux on the island of Reunion, a nebula was found that looked like a comet. At this time the idea arose to make the famous catalog of deep sky objects that so many hours that the fans enjoy so much. The first object of the Messier catalog, M1 (Crab Nebula) had already been discovered in England by John Bevis in 1731, but Messier was unaware of this fact and took his observation for a genuine discovery. Of the 110 objects in the catalog, only 44 are Messier's own discoveries.

The Hôtel de Cluny in the time of Messier, note the dome of the observatory

The first version of the catalog was published in 1771, the year in which he moved to an apartment at the Hôtel de Cluny, next to the observatory, with his wife Marie-Madeleine Dordolot de Vermauchampt. In eighteenth-century absolutist France, it was not common for a bourgeois to marry a lady of the nobility, but his success as a discoverer of kites and his appointment as "Astronomer of the Navy" allowed him to climb the social ladder.

First page of the Messier Catalog

Messier worked in the tower from the fifties of the eighteenth century until shortly before his death in 1817. In the nineteenth century the structure of wood and glass that housed the telescopes was dismantled and today there is not even a sad plaque I remember the story.

Painting by Thomas Shotter Boys (1839)