In 1774, Méchain 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 Hôtel de Clugny. Apparently, the two astronomers became friends around this time.

On the new post, Méchain 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.

In 1777, Pierre Méchain married Barbe-Thérèse Marjou whom he knew from his work in Versailles. They had two sons: Jérôme, born 1780, and Augustin, born 1784, and one daughter.

Like Messier, Pierre Méchain became much devoted to comet observing and hunting, resulting in the original discovery of 8 and independent co-discovery of 3 of these objects (see his discovery list). Also like Messier, he soon started to stumble over nebulous objects, the first being M63 on June 14, 1779. Between June 1779 and April 1782, he discovered the considerable number of 30 deep sky objects, 26 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. Méchain's last two contributions, M102 and M103, went into the publication unchecked and without positions.

Four additional findings of Méchain 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 Méchain (e.g. by John Herschel and J.L.E. Dreyer, the author of the NGC). In this same letter, Méchain 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.

In this letter, he also mentions the objects listed in Messier's catalog with M97 which Owen Gingerich had identified as M108 and M109 - these objects have been added to the modern Messier Catalog. M108 (NGC 3556) is generally accepted, while Gingerich's M109 (NGC 3992) has been found to lack coincidence with Méchain's discovery, which was found (by Henk Bril) to be NGC 3953 (M109B) - Gingerich's M109 may be an observation (and discovery) of Charles Messier. Moreover, Pierre Méchain states to have observed some more "nebulae" in the region of the Virgo Cluster which Messier had not included in his catalog, but unfortunately doesn't give any detail which could help to identify his presumable discoveries.

In that letter, he also mentions that he would soon move to a "more comfortable place for observing" in the month after, i.e., June 1783; the place was the former home of J.D. Maraldi who had retired and left to Italy 11 years earlier. However after that time, no further deep sky discoveries by Méchain seem to have occurred: There are no noted publications of any later deep sky object observations by Pierre Méchain. However, he served as co-editor of the 1795 edition of Jean Fortin's "Atlas Céleste de Flamstéed" (Fortin 1795); on the charts of this work, the positions of many nebulae are given, including those of Méchain's objects M104-M109B.

Méchain discovered his first two comets in 1781, and because of his mathematical skills, he was able to calculate their orbits. In particular, he investigated the orbits of the comets of 1532 and 1661, and disproved the then-common hypothesis that this were appearances of the same object. This work won the Grand Prix of 1782 of the Academy of Sciences, and this winning was the main reason that he was made a member of the Academy of Sciences in 1782. Méchain's third comet discovery 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.

During the 1780s, Méchain undertook several surveys to produce maps, e.g. of Germany and Northern Italy. In 1785, Pierre Méchain became editor of the Connoissance des Temps, the journal which had e.g. published the Messier Catalog - one source states that Charles Messier had been appointed as associate editor in the same year. Méchain was principle editor of the Connoissance des Temps for the years 1788 to 1794 (published 1785 to 1792).

In 1787, Méchain 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, England in the same year.

Méchain 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 Méchain 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, Méchain and Tranchot got arrested by revolutioneers in Essone, who first mistook their instruments as weapons, but later let them proceed.

When in Spain, Méchain 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 Méchain himself was away, all of his property got lost, and his family suffered greatly. Méchain 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 became 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, Méchain 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 Méchain caught yellow fever and died in Castillion de la Plana in Spain on September 20, 1804.

Pierre Méchain was honored by the astronomical community with the naming (on June 24, 2002) of asteroid (21785) Méchain, discovered by Milos Tichý at Kle on September 21, 1999, and provisionally designated 1999 SS2.

Pierre Méchain's Deep Sky Discoveries

Note that Kenneth Glyn Jones, apparently following Admiral Smyth, has erroneously assigned three more objects to Pierre Méchain: M65, M66, and M68, which actually are all original discoveries of Charles Messier.

 M63      1779 Jun 14
[M81]     1779 Aug     orig: Bode 1774 Dec 31
[M82]     1779 Aug     orig: Bode 1774 Dec 31
 M78      1780 Begin
[M71]     1780 Jun 28  orig: De Chéseaux 1745-6
 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 19
 M85      1781 Mar  4
M109B     1781 Mar 12  NGC 3953
 M98      1781 Mar 15
 M99      1781 Mar 15
M100      1781 Mar 15
 M95      1781 Mar 20
 M96      1781 Mar 20
 M51B     1781 Mar 20  NGC 5195; companion of M51
 M94      1781 Mar 22
M105      1781 Mar 24
M101      1781 Mar 27
M102 (?)  1781 Mar-Apr (NGC 5866)  disclaimed by Méchain; still controverse
M103      1781 Mar-Apr
M104      1781 May 11
M106      1781 Jul
M107      1782 Apr

Pierre Méchain's letter of May 6, 1783

Links

• Asteroid 21785 Méchain (1999 SS2) (NEO/JPL)

References

• Pierre Méchain, 1783. 9. [Lettre] De M. Méchain, de l'Acad. R. des Sciences. De Paris, le 6 Mai 1783 [[Letter] To Jean (Johann III) Bernoulli, by M. Méchain, of the Royal Academy of Sciences. Paris, May 6, 1783]. Nouveaux Mémoires de l'Académie Royale des Sciences et Belles-Lettres, Année MDCCLXXXII (1782), Berlin, pp. 46-51 [Bibcode: 1784NMARB1782...46M]. From: Jean Bernoulli, 1784. Histoire de l'Académie Royale. Astronomie -- Extraits de la Correspondence de M. Bernoulli. Nouveaux Mémoires de l'Académie Royale des Sciences et Belles-Lettres, Année MDCCLXXXII (1782), Berlin, pp. 38-57 [Bibcode: 1784NMARB1782...38B].
• Johann Elert Bode and Pierre Méchain, 1783. 16. Ueber die Bahn des zweyten Kometen von 1781. Entdeckung einiger Nebelsterne; die Elemente der Bahn des neuen Planeten und astronomische Beobachtungen. Astronomisches Jahrbuch für das Jahr 1786, pp. 231-237 [Bibcode: 1783AJBer1786..231B]
• Jean Fortin, 1795. Atlas Céleste de Flamstéed. Troisième Édition, Revue, corrigée & augmentée par les Citoyens Lalande & Méchain. Belin Lamarche, Paris. Images of the maps of this atlas are available online on Henk Bril's site. Henk Bril has identified 95 nebulae, including 85 Messier objects (2 at wrong positions, and another 4 duplicated at wrong positions) and 10 others, including 3 asterisms and a duplicate wrong position of the LMC.

• Kenneth Glyn Jones, 1991. Messier's Nebulae and Star Clusters. 2nd ed, Cambridge University Press, p. 335-6.
• Jean Baptiste Joseph Delambre, 1827. Histoire de l'Astronomie au dix-huitièmme siècle [History of Astronomy in the Eighteenth Century]. Bachelier (Successor of Mme. Ve. Courcier), Paris. P. xxxix, 755-767.

• On the Meridian Expedition, metric system, & c.:
  • Jean-Baptiste Delambre (ed.), 1806, 1807, 1810. Base du système métrique décimal, ou mesure de l'arc du méridien compris entre les parallèles de Dunkerque et Barcelone, exécutée en 1792 et années suivantes, par MM. Méchain et Delambre, Rédigée par M. Delambre etc. Three volumes plus an incomplete Fourth volume. Baudouin, Paris.
  • Ken Alder, 2002. The Measure of All Things. The Seven-Year Odyssey that Transformed the World. Little, Brown, London.
  • Guillaume Bigourdan, 1901. Le système métrique des poids et mesure. Gauthier-Villars, Paris.
  • Denis Guedj, 1987. La Méridienne (1792-1797). Series "Etonnants Voyageurs," Edition Seghers, Paris. German translation: Die Geburt des Meters, 1991, translated by Klaus Jölen, Campus Verlag, Frankfurt.

---

Hartmut Frommert
Christine Kronberg
[contact]

Last Modification: September 17, 2017