'Pierre François André Méchain' (
August 16,
1744 –
September 20,
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. He displayed 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, which produced 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 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. His sole discoveries are:
His co-discovery with Messier was
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.
Other sources say Méchain discovered eleven comets. This is likely because he was responsible for demonstrating mathematically that the
Comet of 1532 and the
Comet of 1661 were not the same object. He is not, however, generally considered to be the discoverer of these two comets.
Legacy
Asteroid 21785 Méchain is named after him.
External links
★
Pierre Méchain biography, SEDS Messier pages
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