Pierre Méchain
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Pierre François André Méchain (; 16 August 1744 – 20 September 1804) was a French
astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
and
surveyor Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is ...
who, with
Charles Messier Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects''. Messier's purpose ...
, was a major contributor to the early study of
deep-sky object A deep-sky object (DSO) is any astronomical object that is not an individual star or Solar System object (such as Sun, Moon, planet, comet, etc.). The classification is used for the most part by amateur astronomers to denote visually observed fa ...
s and
comets A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
.


Life

Pierre Méchain was born in
Laon Laon () is a city in the Aisne department in Hauts-de-France in northern France. History Early history The holy district of Laon, which rises a hundred metres above the otherwise flat Picardy plain, has always held strategic importance. ...
, the son of the ceiling designer and plasterer Pierre François Méchain and Marie–Marguerite Roze. He displayed mental gifts in
mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...
and
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
but had to give up his studies for lack of money. However, his talents in
astronomy Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, g ...
were noticed by 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 The Palace of Versailles ( ; french: Château de Versailles ) is a former royal residence built by King Louis XIV located in Versailles, about west of Paris, France. The palace is owned by the French Republic and since 1995 has been managed, ...
, 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 Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects''. Messier's purpose ...
, and apparently, they became friends. In the same year, he also produced his first astronomical work, a paper on an occultation of
Aldebaran Aldebaran (Arabic: “The Follower”, "الدبران") is the brightest star in the zodiac constellation of Taurus. It has the Bayer designation α Tauri, which is Latinized to Alpha Tauri and abbreviated Alpha Tau or α Tau. Alde ...
by the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
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 The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at th ...
in 1782, and was the editor of ''
Connaissance des Temps The ''Connaissance des temps'' (English: Knowledge of the Times) is an official yearly publication of astronomical ephemerides in France. Until just after the French Revolution, the title appeared as ''Connoissance des temps'', and for several ye ...
'' from 1785 to 1792; this was the journal which, among other things, first published the list of
Messier objects The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only in ...
. In 1789 he was elected a
Fellow of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural science, natural knowledge, incl ...
. He participated in the
Anglo-French Survey (1784–1790) The Anglo-French Survey (1784–1790) was the geodetic survey to measure the relative position of Greenwich Observatory and the Paris Observatory via triangulation. The English operations, executed by William Roy, consisted of the measureme ...
to measure by
trigonometry Trigonometry () is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. T ...
the precise distance between the
Paris Observatory The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its histor ...
and the Royal Greenwich Observatory. This project was initiated by
Dominique, comte de Cassini Jean-Dominique, comte de Cassini (30 June 174818 October 1845) was a French astronomer, son of César-François Cassini de Thury and great-grandson of Giovanni Domenico Cassini. Cassini was born at the Paris Observatory. He succeeded his fath ...
, and in 1787 Méchain visited Dover and London with Cassini and
Adrien-Marie Legendre Adrien-Marie Legendre (; ; 18 September 1752 – 9 January 1833) was a French mathematician who made numerous contributions to mathematics. Well-known and important concepts such as the Legendre polynomials and Legendre transformation are name ...
to facilitate its progress. The three men also visited the astronomer
William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline ...
at
Slough Slough () is a town and unparished area in the unitary authority of the same name in Berkshire, England, bordering west London. It lies in the Thames Valley, west of central London and north-east of Reading, at the intersection of the M4 ...
. With his surveying skills, he worked on maps of Northern Italy and Germany after this, but his most important mapping work was
geodetic Geodesy ( ) is the Earth science of accurately measuring and understanding Earth's figure (geometric shape and size), orientation in space, and gravity. The field also incorporates studies of how these properties change over time and equivale ...
: the determination of the southern part of the meridian arc of the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
's surface between
Dunkirk Dunkirk (french: Dunkerque ; vls, label=French Flemish, Duunkerke; nl, Duinkerke(n) ; , ;) is a commune in the department of Nord in northern France.Barcelona Barcelona ( , , ) is a city on the coast of northeastern Spain. It is the capital and largest city of the autonomous community of Catalonia, as well as the second most populous municipality of Spain. With a population of 1.6 million within ci ...
beginning in 1791. This measurement would become the basis of the
metric system The metric system is a system of measurement that succeeded the Decimal, decimalised system based on the metre that had been introduced in French Revolution, France in the 1790s. The historical development of these systems culminated in the d ...
's unit of length, the meter. He encountered numerous difficulties on this project, largely stemming from the effects of the
French Revolution The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in November 1799. Many of its ideas are considere ...
. 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 The Reign of Terror (french: link=no, la Terreur) was a period of the French Revolution when, following the creation of the First Republic, a series of massacres and numerous public executions took place in response to revolutionary fervour, ...
. He was released from Spain to live in Italy, then returned home in 1795. A particularly intriguing fact about this project was that Méchain was uncertain of the precision of his measurements owing to anomalous results in verifying his latitude by astronomical observation. Ultimately, the distance from the pole to the equator, which Méchain and his associate
Jean Baptiste Joseph Delambre Jean Baptiste Joseph, chevalier Delambre (19 September 1749 – 19 August 1822) was a French mathematician, astronomer, historian of astronomy, and geodesist. He was also director of the Paris Observatory, and author of well-known books on t ...
had intended to be exactly ten million meters (or ten thousand kilometres), was determined in the late 20th century by space satellites to be 10,002,290 meters. This small error of 2,290 meters equals 1.423 statute miles; the error in such a large measurement amounts to 14½ inches per statute mile. It represents in each meter an error of approximately 0.23 millimetres – slightly more than the width of a single strand of human hair. This discrepancy is sometimes mentioned as "Méchain's error", with the suggestion that the tiny variation in the length of the meridian (not detected for nearly two hundred years) can be attributed to Méchain's calculations. But analysis of Méchain's figures reveals that Méchain consistently kept the discrepancy very tiny, essentially forcing his individual reported measurements to appear more precise and consistent than would be reasonably expected of a survey involving more than a hundred measurements of mostly rough country using 18th century equipment; Méchain's putative error did not affect the final value of the length of the meter nor the measurement of the meridian. From 1799, he was the director of the
Paris Observatory The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its histor ...
. 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 Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. In ...
and died in
Castellón de la Plana Castellón de la Plana (officially in ca-valencia, Castelló de la Plana), or simply Castellón ( ca-valencia, Castelló, link=no) is the capital city of the province of Castellón, in the Valencian Community, Spain. It is located in the east ...
.


Discoveries

Méchain discovered either 25 or 26 deep-sky objects, depending on how one counts M102. Méchain disavowed the M102 observation in 1783, claiming it was 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. He independently discovered four others, originally discovered by someone else but unknown to him at the time and included in the Messier catalogue: M71, discovered by Jean-Philippe de Chéseaux 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 NGC 5195 (also known as Messier 51b or M51b) is a dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC 5194). Both galaxies are located approximately 25 million light-years away in the constellation Canes Venat ...
, the companion galaxy that makes M51 (the
Whirlpool Galaxy The Whirlpool Galaxy, also known as Messier 51a, M51a, and NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus. It lies in the constellation Canes Venatici, and was the first galaxy to be classifie ...
) so distinctive. Méchain never set out to observe deep-sky objects. Like Messier, he was solely interested in cataloguing objects that might be mistaken for
comets A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...
; having done so, he was the second-most successful discoverer of comets of his time, after Messier himself. All together, he originally discovered eight comets, and co-discovered three. His sole discoveries are: * C/1781 M1 (Méchain), ''1781 I'' * C/1781 T1 (Méchain), ''1781 II'' * C/1785 E1 (Méchain), ''1785 II'' * 2P/Encke, discovered in 1786 * C/1787 G1 (Méchain), ''1787 I'' *
8P/Tuttle 8P/Tuttle (also known as Tuttle's Comet or Comet Tuttle) is a periodic comet with a 13.6-year orbit. It fits the classical definition of a Jupiter-family comet with an orbital period of less than 20 years, but does not fit the modern definitio ...
, discovered in 1790 * C/1799 P1 (Méchain), ''1799 II'' * C/1799 Y1 (Méchain), ''1799 III'' Méchain's co-discoveries are: * C/1785 A1 (Messier-Méchain), ''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 An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...
21785 Méchain was named in his honour, discovered by
Miloš Tichý Miloš Tichý (born 1966 in Počátky) is a Czech astronomer. He is a prolific discoverer of asteroids. He also discovered the periodic comet 196P/Tichý. He works together with his ex-wife at Kleť Observatory Kleť Observatory ( cz, Hvěz ...
at
Kleť Observatory Kleť Observatory ( cz, Hvězdárna Kleť; obs. code: 046) is an astronomical observatory in the Czech Republic. It is situated in South Bohemia, south of the summit of Mount Kleť, near the town of České Budějovice. Constructed in 1957, t ...
on 21 September 1999, and provisionally designated 1999 SS2.


See also

*
History of the metre The history of the metre starts with the Scientific Revolution that is considered to have begun with Nicolaus Copernicus's publication of '' De revolutionibus orbium coelestium'' in 1543. Increasingly accurate measurements were required, and ...
*
Messier object The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only int ...
*
List of Messier objects The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only int ...
*
Messier marathon A Messier marathon is an attempt, usually organized by amateur astronomers, to find as many Messier objects as possible during one night. The Messier catalogue was compiled by French astronomer Charles Messier during the late 18th century and co ...
*
Seconds pendulum A seconds pendulum is a pendulum whose period is precisely two seconds; one second for a swing in one direction and one second for the return swing, a frequency of 0.5 Hz. Pendulum A pendulum is a weight suspended from a pivot so that ...
* Meridian arc of Delambre and Méchain


Footnotes


External links


Pierre Méchain biography, SEDS Messier pages
* {{DEFAULTSORT:Mechain, Pierre Francois Andre 1744 births 1804 deaths People from Laon Deaths from yellow fever 18th-century French astronomers Discoverers of comets Members of the French Academy of Sciences Infectious disease deaths in Spain Fellows of the Royal Society Metrologists French surveyors French geodesists 19th-century French astronomers