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Pierre Méchain

Pierre Méchain
Born 16 August 1744(1744-08-16)
Laon
Died 20 September 1804 (aged 60)
Castellon de la Plana, Spain
Nationality French
Fields astronomy
Institutions Paris Observatory
Known for deep sky objects
comets

Pierre François André Méchain (16 August 1744, Laon, Aisne – 20 September 1804) was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep sky objects and comets.

Contents

Life

Pierre Méchain was born in Laon, the son of the ceiling designer and plasterer Pierre François Méchain. He displayed mental gifts in mathematics and physics but had to give up his studies for lack of money. However, his talents in astronomy were noticed by Joseph Jérôme Lalande, for whom he became a friend and proof-reader. Lalande then secured a position for him with the Naval Depot of Maps at Versailles, where he worked through the 1770s engaged in hydrographic work and coastline surveying. It was during this time -- approximately 1774 -- that he met Charles Messier, with whom he also became friends. In this year he also produced his first astronomical work, a paper on an occultation of Aldebaran by the Moon.

In 1777 he married Barbe-Thérèse Marjou, who bore him two sons and a daughter. He was admitted to the French Académie des sciences in 1782, and was the editor of Connaissance des Temps from 1785 to 1792; this was the journal which, among other things, first published the list of Messier objects.

With his surveying skills, he worked on maps of Northern Italy and Germany after this, but his most important mapping work was geodetic: the determination of the southern part of an arc of the Earth's surface between Dunkirk and Barcelona beginning in 1791. This measurement would become the basis of the metric system's unit of length, the meter. He encountered numerous difficulties on this project, largely stemming from the effects of the French Revolution. He was arrested after it was suspected his instruments were weapons, he was interned in Barcelona after war broke out between France and Spain, and his property in Paris was confiscated during The Terror. He was released from Spain to live in Italy, then returned home in 1795.

From 1799, he was the director of the Paris Observatory.

Continuing doubts about his measurements of the Dunkirk-Barcelona arc led him to return to that work. This took him back to Spain in 1804, where he caught yellow fever and died in Castellon de la Plana.

Discoveries

Méchain discovered either 26 or 27 deep-sky objects, depending on how one counts M102. Eighteen of these were included in the Messier catalog:

He independently discovered four others, originally discovered by someone else but unknown to him at the time and included in the Messier catalog: M71, discovered by Philippe de Cheseaux in the 1740s; M80, discovered by Messier about two weeks earlier than Méchain's observation; and M81 and M82, discovered originally by Johann Bode.

Six other discoveries are "honorary Messier objects" added to the list in the 20th century: M104, M105, M106, M107, M108, M109.

He also discovered NGC 5195, the companion galaxy that makes M51 (AKA the Whirlpool Galaxy) so distinctive.

One other Messier object can be attributed to him, M102. However, Méchain specifically disavowed the observation from 1783 onwards as a mistaken re-observation of M101. Since that time, others have proposed that he did in fact observe another object, and suggested what they might be. See the discussion The M102 Controversy for more details.

Interestingly, Méchain never set out to observe deep-sky objects. Like Messier, he was solely interested in cataloging objects that might be mistaken for comets; having done so, he was the second-most successful discoverer of comets of his time, after Messier himself.

Altogether, he discovered nine comets either alone or in combination with Messier [1]. His sole discoveries are:

  • C/1781 M1 (Mechain), 1781 I
  • C/1781 T1 (Mechain), 1781 II
  • C/1785 E1 (Mechain), 1785 II
  • 2P/Encke, discovered in 1786
  • C/1787 G1 (Mechain), 1787 I
  • 8P/Tuttle, discovered in 1790
  • C/1799 P1 (Mechain), 1799 II
  • C/1799 Y1 (Mechain), 1799 III

His co-discovery with Messier was C/1785 A1 (Messier-Mechain), former designation 1785 I. Note that only the two named comets have been connected to periodic comets that have computed orbits and in neither case was he an observer when they were computed, so by that technical definition (commonly used for comets since the 19th century) Méchain did not discover any of these nine.

Legacy

Asteroid 21785 Méchain is named after him.

Footnotes

External links








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