Pierre Méchain

Pierre Méchain
Pierre Méchain
Born	(1744-08-16)16 August 1744 Laon
Died	20 September 1804(1804-09-20) (aged 60) Castellon de la Plana, Spain
Nationality	French
Fields	astronomy
Institutions	Paris Observatory
Known for	deep sky objects comets metre

Pierre François André Méchain (16 August 1744 – 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.

Life

Pierre Méchain was born in Laon, the son of the ceiling designer and plasterer Pierre François Méchain and Marie-Marguerite Roze. 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 of the second edition of his book "L'Astronomie". Lalande then secured a position for him as assistant hydrographer with the Naval Depot of Maps and Charts 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, and apparently, they became friends. In the same year, he also produced his first astronomical work, a paper on an occultation of Aldebaran by the Moon and presented it as a memoir to the Academy of Sciences.

In 1777, he 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. 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. In 1789 he was elected a Fellow of the Royal Society.^[1]

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 the meridian 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 25 or 26 deep-sky objects, depending on how one counts 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.

      Open cluster       Globular cluster       Nebula       Planetary nebula       Supernova remnant       Galaxy       Other

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:

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

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 originally discovered eight comets, and co-discovered three .^[2]

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

Méchain's co-discoveries are:

• C/1785 A1 (Messier-Mechain), 1785 I
• C/1792 II Gregory-Méchain, 1792 II
• C/1801 Pons (Pons-Messier-Méchain-Bouvard), 1801 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

On 24 June 2002, Asteroid 21785 Méchain was named in his honor, discovered by Milos Tichý at Kleť Observatory on 21 September 1999, and provisionally designated 1999 SS2.

See also

• Messier object
• List of Messier objects
• Messier marathon

Footnotes

External links

• Pierre Méchain biography, SEDS Messier pages
• O'Connor, John J.; Robertson, Edmund F., "Pierre Méchain", MacTutor History of Mathematics archive, University of St Andrews .