Pierre Méchain

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Posthumous portrait of Pierre Méchain, painted in 1824 by Narcisse Garnier after copperplate engravings

Pierre-François-André Méchain (born August 16, 1744 in Laon , France , † September 20, 1804 in Castellón de la Plana , Spain ) was a French astronomer and geographer . He discovered eight comets and 26 objects outside the solar system and took part in an expedition, the result of which served as the definition of the meter .

life and work

Pierre Méchain was born in northern France to the architect Pierre-François Méchain and Marie-Marguerite Roze. Originally, he also wanted to be an architect and studied mathematics and physics . However, due to financial difficulties, he had to leave the university . At times he worked as a tutor for two boys, about 50 km from Paris. He made friends with Jérôme de Lalande , who gave him preliminary excerpts from his work "L'Astronomie". In 1772 Lalande got him a job as a hydrograph at the naval chart office in Versailles . The position was initially temporary, and Méchain supplemented his income by teaching math.

In 1774 Méchain got a permanent job as a computer in the navy and was initially occupied with the precise determination of the French coastline. During this time he met Charles Messier , who was also employed by the Navy, but worked in a small observatory at the Hôtel de Cluny .

In 1777 he married Barbe-Thérèse Marjou. The two had two sons, Jérôme and Augustin, and a daughter.

In addition to his work, Méchain carried out astronomical observations in Versailles. In 1774 he recorded an occlusion of the star Aldebaran by the moon . Like his friend Messier, he became a “comet hunter”. He passed on the position of unknown foggy objects, which could be comets, to Messier, who checked this and entered it in his catalog . In this way, Méchain discovered 26 deep sky objects, including the globular cluster M80 and the galaxies M102 and M103 .

Méchain discovered his first comet in 1781. Based on his mathematical knowledge, he was able to determine its orbit . He studied the records of the comets from 1532 and 1661 and disproved the then prevailing theory that they were one and the same object. In 1782 he received the award of the Academy of Sciences and became its member. In 1786 he discovered a comet that is now called Encke . Encke was rediscovered independently by Caroline Herschel in 1792 and by Jean-Louis Pons in 1805 . The astronomer Johann Franz Encke was finally able to determine its orbit, which showed that Encke is the comet with the shortest period with an orbital period of only 3.5 years. In 1790 Méchain discovered a periodic comet that is now called 8P / Tuttle .

After 1780 Méchain made several trips, including a. to Germany and Northern Italy to make maps. In 1785 he became editor of the magazine "Connaissance des Temps", which had published the Messier catalog at the time.

In 1787, Méchain worked with Jean Dominique Comte de Cassini and Adrien-Marie Legendre to determine the exact difference in longitude between Paris and Greenwich . In the same year, the three visited the German-born astronomer William Herschel in his observatory in Slough, England .

In 1792 the distance between Dunkirk and Barcelona was to be determined exactly. Jean-Baptiste Joseph Delambre also took part in the so-called Meridian Expedition . Méchain and his assistant Jean Joseph Tranchot took over the southern sector. The expedition proved difficult as a result of the aftermath of the French Revolution . Méchain and Tranchot were even temporarily arrested in Essone by revolutionaries who thought their scientific instruments were weapons. Méchain was injured in an accident in Spain. When he finally recovered, the Franco-Spanish War broke out and he was interned. During this time he discovered his seventh comet from Barcelona on January 10, 1793. Here he believed to have discovered an error in his calculations of the latitude of Barcelona, ​​which had an impact on the meridian project. The mistake never let go of him, led to self-doubt and depression, which later delayed his work, and was also a reason why he later returned to Spain. In 1794 he was able to travel to Genoa, where he stayed for a year before returning to Paris in 1795. During his stay abroad, Méchain lost all of his fortune in France and his family was subjected to severe reprisals. When he returned in 1795, he received great honors. He became a member of the new Academy of Sciences, the Bureau des Longitudes and director of the Paris Observatory . Here he discovered his last comet on December 26, 1799.

In 1802 he was elected a foreign member of the Göttingen Academy of Sciences .

Méchain was known for the accuracy of his work, his works were published over a long time. Napoléon Bonaparte gave him permission to extend his investigations and Méchain left Paris in 1803. In Spain he fell ill with yellow fever in 1804 and died.

In his memory the asteroid (21785) was named Méchain .

See also


Web links

Individual evidence

  1. ^ List of members since 1666: Letter M. Académie des sciences, accessed on January 21, 2020 (French).
  2. e.g. Edwin Danson Weighing the World. The Quest to measure the earth , Oxford University Press, pp. 239ff
  3. Holger Krahnke: The members of the Academy of Sciences in Göttingen 1751-2001 (= Treatises of the Academy of Sciences in Göttingen, Philological-Historical Class. Volume 3, Vol. 246 = Treatises of the Academy of Sciences in Göttingen, Mathematical-Physical Class. Episode 3, vol. 50). Vandenhoeck & Ruprecht, Göttingen 2001, ISBN 3-525-82516-1 , p. 163.