In 1774, Mechain obtained the more permanent post as a calculator with the Depot of the Navy. At that time, he has met Charles Messier, who worked for the same department, but at the small observatory at Hotel de Cluny. Apparently, the two astronomers became friends around this time.

On the new post, Mechain was first involved in surveys of the French coastline. In addition, he had occasion to make some observations at Versailles. In 1774, he observed an occultation of Aldebaran by the Moon, which he later presented as a memoir to the Academy of Sciences.

Like Messier, Pierre Mechain became much devoted to comet observing and hunting. Also like Messier, he soon started to stumble over nebulous objects, and between 1779 and 1782, discovered the considerable number of 30 deep sky objects, 29 of which were original firsts. As apparently he had got in close cooperation with Charles Messier at that time, he almost instantly communicated his observations to Charles Messier, who usually checked their positions and added them to his catalog. Both astronomers undertook a vigorous effort to find more nebulae between late August 1780 and March 1781, when the manuscript for the final version of the Messier catalog was sent out to print. Mechain's last two contributions, M102 and M103, went into the publication unchecked and without positions.

Four additional findings of Mechain missed the publication; these are now known as M104, M105, M106, and M107. He communicated them to Bernoulli, the editor of the Berliner Astronomisches Jahrbuch, in a letter dated May 6, 1783. As these four objects were not contained in the original Messier catalog, they were longly attributed separately to Pierre Mechain (e.g. by John Herschel and J.L.E. Dreyer, the author of the NGC). In this same letter, Mechain disclaimed - possibly in error - his discovery of M102 as an erroneous re-observation of M101, thereby initiating a still open discussion on the identity of this object.

Mechain discovered his first two comets in 1781, and because of his mathematical skills, he was able to calculate their orbits. He was made a member of the Academy of Sciences in 1782. A third comet followed in 1785, and in 1786, he discovered another one which later became famous as "Comet Encke" (after the calculater of its orbit, the German astronomer J.F. Encke). Comet Encke was later independently rediscovered by Caroline Herschel in 1792 and by Pons in 1805, and is the shortest-periodic comet ever discovered, with a period of 3.5 years.

In 1786, Pierre Mechain became an associate editor of the Connaissance des Temps, the journal which had e.g. published the Messier Catalog - one year after Charles Messier had been appointed for the same job.

In 1787, Mechain collaborated with J.D. Cassini and Legendre on measuring the acurate longitude difference between Paris and Greenwich. All three visited William Herschel at his observatory in Slough in the same year.

Mechain discovered his fifth comet in the same year, 1787. His next, 6th discovery occurred in 1790; this finding was periodic comet Tuttle with a period of 13.75 years, as recognized by Tuttle in 1858.

In 1791, a project was initiated of a new survey of the meridian from Dunkirk to Barcelona, and Mechain undertook the southern part, together with an assistant, Tranchot. The operation started June 25, 1792, suffering from various difficulties caused by the French revolution: At one time, Mechain and Tranchot got arrested by revolutioneers in Essone, who first mistook their instruments as weapons, but later let them proceed.

When in Spain, Mechain got hurt in an accident, and when he had recovered, war had broken out between France and Spain, and he got interned. Nevertheless, he discovered another comet, his 7th, from Barcelona on January 10, 1793. During the terror regime in Paris, while Mechain himself was away, all of his property got lost, and his family suffered greatly. Mechain was eventually allowed to leave Spain for Italy, where he stayed at Genoa for some time, and returned to Paris finally in 1795.

On his return, he bacame member of the new Academy of Sciences, and the Bureau of Longitudes. Moreover, he was made director of the Paris Observatory, where he discovered his 8th and last comet on December 26, 1799; Messier took part in observing this one in order to obtain its orbit.

Apparently, Mechain was concerned about the quality of the results of his survey, and refused to publish them for a long time. Eventually, he got permission from Napoleon to extend the survey, and left Paris in 1803.

After completing part of this work, Pierre Mechain caught yellow fever and died in Castillion de la Plana in Spain on September 20, 1804.

Pierre Mechain's Deep Sky Discoveries

 M63      1779 Jun 14
 M78      1780 Begin
 M65      1780 Mar  1
 M66      1780 Mar  1
 M68      1780 Apr  9
[M71]     1780 Jun 28  orig: De Chéseaux 1745-6
[M81]     1780 Aug     orig: Bode 1774 Dec 31
[M82]     1780 Aug     orig: Bode 1774 Dec 31
 M75      1780 Aug 27
 M72      1780 Aug 30
 M76      1780 Sep  5
 M74      1780 Sep End
 M79      1780 Oct 26
 M77      1780 Oct 29
[M80]     1781 Jan 27  orig: Messier 1781 Jan 4
 M97      1781 Feb 16
M108      1781 Feb 16
M109      1781 Feb 16
 M85      1781 Mar  4
 M98      1781 Mar 15
 M99      1781 Mar 15
M100      1781 Mar 15
 M95      1781 Mar 20
 M96      1781 Mar 20
NGC 5195  1781 Mar 20  companion of M51
 M94      1781 Mar 22
M105      1781 Mar 24
M101      1781 Mar 27
M102?     1781 Mar End (NGC 5866)  disclaimed by Mechain; still controverse
M103      1781 Mar End
M104      1781 May 11
M106      1781 Jul
M107      1782 Apr

Pierre Mechain's Comet Discoveries

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Hartmut Frommert (spider@seds.org)
Christine Kronberg (smil@lrz.uni-muenchen.de)

Last Modification: 22 Jan 2000, 12:00 MET