|Born||16 August 1744|
|Died||20 September 1804 60) (aged|
Castellón de la Plana, Spain
|Known for|| Deep-sky objects |
Pierre François André Méchain (French pronunciation: [pjɛʁ fʁɑ̃swa ɑ̃dʁe meʃɛ̃] ; 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.
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 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.
He participated in the Anglo-French Survey (1784–1790) to measure by trigonometry the precise distance between the Paris Observatory and the Royal Greenwich Observatory. This project was initiated by Dominique, comte de Cassini, and in 1787 Méchain visited Dover and London with Cassini and Adrien-Marie Legendre to facilitate its progress. The three men also visited the astronomer William Herschel at Slough.
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.
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 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.
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 Castellón de la Plana.
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
|Messier number||NGC/IC Number||Common name||Date of Discovery||Object type||Distance (kly)||Constellation||Apparent magnitude|
|M63||NGC 5055||Sunflower Galaxy||14 June 1779||Galaxy, spiral||37,000||Canes Venatici||8.5|
|M72||NGC 6981||30 August 1780||Cluster, globular||53||Aquarius||10.0|
|M74||NGC 628||Sep 1780||Galaxy, spiral||35,000||Pisces||10.5|
|M75||NGC 6864||27 August 1780||Cluster, globular||58||Sagittarius||9.5|
|M76||NGC 650, NGC 651||Little Dumbbell Nebula||5 September 1780||Nebula, planetary||3.4||Perseus||10.1|
|M77||NGC 1068||Cetus A||29 October 1780||Galaxy, spiral||60,000||Cetus||10.5|
|M78||NGC 2068||Begin 1780||Nebula, diffuse||1.6||Orion||8.0|
|M79||NGC 1904||26 October 1780||Cluster, globular||40||Lepus||8.5|
|M85||NGC 4382||4 March 1781||Galaxy, lenticular||60,000||Coma Berenices||10.5|
|M94||NGC 4736||22 March 1781||Galaxy, spiral||14,500||Canes Venatici||9.5|
|M95||NGC 3351||20 March 1781||Galaxy, barred spiral||38,000||Leo||11.0|
|M96||NGC 3368||20 March 1781||Galaxy, spiral||38,000||Leo||10.5|
|M97||NGC 3587||Owl Nebula||16 February 1781||Nebula, planetary||2.6||Ursa Major||9.9|
|M98||NGC 4192||15 March 1781||Galaxy, spiral||60,000||Coma Berenices||11.0|
|M99||NGC 4254||15 March 1781||Galaxy, spiral||60,000||Coma Berenices||10.5|
|M100||NGC 4321||15 March 1781||Galaxy, spiral||60,000||Coma Berenices||10.5|
|M101||NGC 5457||Pinwheel Galaxy||27 March 1781||Galaxy, spiral||27,000||Ursa Major||7.9|
|M102||(Not conclusively identified)|
|M103||NGC 581||Mar–Apr 1781||Cluster, open||8||Cassiopeia||7.0|
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:
|Messier number||NGC/IC Number||Common name||Date of Discovery||Object type||Distance (kly)||Constellation||Apparent magnitude|
|M104||NGC 4594||Sombrero Galaxy||11 May 1781||Galaxy, spiral||50,000||Virgo||9.5|
|M105||NGC 3379||24 March 1781||Galaxy, elliptical||38,000||Leo||11.0|
|M106||NGC 4258||Jul 1781||Galaxy, spiral||25,000||Canes Venatici||9.5|
|M107||NGC 6171||Cluster, globular||20||Ophiuchus||10.0|
|M108||NGC 3556||19 February 1781||Galaxy, barred spiral||45,000||Ursa Major||11.0|
|M109||NGC 3992||12 March 1781||Galaxy, barred spiral||55,000||Ursa Major||11.0|
He also discovered NGC 5195, the companion galaxy that makes M51 (the Whirlpool Galaxy) 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; 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:
Méchain's co-discoveries are:
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.
On 24 June 2002, Asteroid 21785 Méchain was named in his honour, discovered by Miloš Tichý at Kleť Observatory on 21 September 1999, and provisionally designated 1999 SS2.
Charles Messier was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and faint star clusters, which came to be known as the Messier objects. The purpose of the catalogue was to help astronomical observers distinguish between permanent and transient visually diffuse objects in the sky.
The metre or meter is the base unit of length in the International System of Units (SI). The SI unit symbol is m.
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 interested in finding comets, he created a list of those non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as the Messier catalogue. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier number. The catalogue includes most of the astronomical deep-sky objects that can easily be observed from Earth's Northern Hemisphere; many Messier objects are extremely popular targets for amateur astronomers.
Abbé Nicolas-Louis de Lacaille, formerly sometimes spelled de la Caille, was a French astronomer and geodesist who named 14 out of the 88 constellations. From 1750 to 1754 he studied the sky at the Cape of Good Hope in present-day South Africa. Lacaille observed over 10,000 stars using just a half-inch refractor.
Jean Baptiste Joseph, chevalier Delambre 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 the history of astronomy from ancient times to the 18th century.
Joseph Jérôme Lefrançois de Lalande was a French astronomer, freemason and writer.
Geodesy (/dʒiːˈɒdɪsi/), also named geodetics, is the scientific discipline that deals with the measurement and representation of the Earth. The history of geodesy began in pre-scientific antiquity and blossomed during the Age of Enlightenment.
The year 1781 in science and technology involved some significant events.
Edward Emerson Barnard was an American astronomer. He was commonly known as E. E. Barnard, and was recognized as a gifted observational astronomer. He is best known for his discovery of the high proper motion of Barnard's Star in 1916, which is named in his honor.
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Messier 102 is a galaxy listed in the Messier Catalogue that cannot be unambiguously identified. Its original discoverer Pierre Méchain said that it was a duplicate observation of Messier 101, but more historical evidence favors that it is NGC 5866, although other galaxies have been suggested as possible identities. The National Aeronautics and Space Administration (NASA) considers it to be the same as NGC 5866.
Messier 65 is an intermediate spiral galaxy about 35 million light-years away in the constellation Leo, within its highly equatorial southern half. It was discovered by Charles Messier in 1780. With M66 and NGC 3628, it forms the Leo Triplet, a small close group of galaxies.
Messier 99 or M99, also known as NGC 4254, is a grand design spiral galaxy in the northern constellation Coma Berenices approximately 15,000,000 parsecs from the Milky Way. It was discovered by Pierre Méchain on 17 March 1781. The discovery was then reported to Charles Messier, who included the object in the Messier Catalogue of comet-like objects. It was one of the first galaxies in which a spiral pattern was seen. This pattern was first identified by Lord Rosse in the spring of 1846.
Messier 105 or M105, also known as NGC 3379, is an elliptical galaxy 36.6 million light-years away in the equatorial constellation of Leo. It was discovered by Pierre Méchain in 1781, just a few days after he discovered the nearby galaxies Messier 95 and Messier 96. This galaxy is one of a few not object-verified by Messier so omitted in the editions of his Catalogue of his era. It was appended when Helen S. Hogg found a letter by Méchain locating and describing this object which matched those aspects under its first-published name, NGC 3379.
The Paris meridian is a meridian line running through the Paris Observatory in Paris, France – now longitude 2°20′14.03″ East. It was a long-standing rival to the Greenwich meridian as the prime meridian of the world. The "Paris meridian arc" or "French meridian arc" is the name of the meridian arc measured along the Paris meridian.
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.
Developed from the reflecting circle, the repeating circle is an instrument for geodetic surveying, invented by Etienne Lenoir in 1784, while an assistant of Jean-Charles de Borda, who later improved the instrument. It was notable as being the equal of the great theodolite created by the renowned instrument maker, Jesse Ramsden. It was used to measure the meridian arc from Dunkirk to Barcelona by Jean Baptiste Delambre and Pierre Méchain.
The history of the metre starts with the scientific revolution that began with Nicolaus Copernicus's work in 1543. Increasingly accurate measurements were required, and scientists looked for measures that were universal and could be based on natural phenomena rather than royal decree or physical prototypes. Rather than the various complex systems of subdivision in use, they also preferred a decimal system to ease their calculations.
C/1769 P1 (Messier) is a long-period comet that was visible to the naked eye at its last apparition in 1769. Because of its outstanding brightness it is called a great comet.
The meridian arc of Delambre and Méchain was a geodetic survey carried out by Jean-Baptiste Delambre and Pierre Méchain in 1792–1798 to measure an arc section of the Paris meridian between Dunkirk and Barcelona; it served as the basis for the original definition of the metre.