Jules Jansen

See also: Jansen

Pierre Jules César Jansen , more known under the name of Jules Jansen , born the February 22nd 1824 with Paris and dead the December 23rd 1907 with Meudon, is a French astronomer.

An accident which has occurred in its youth obstructs it enormously to go, which delays its studies. It obtains its Doctorat science physics with a thesis on the Absorption of obscure radiant heat in the mediums of the eye in 1860 and becomes professor of physics at the School of architecture in 1865. Attracted by work of Gustav Robert Kirchhoff and Robert Wilhelm Bunsen on the Spectroscopy, it is one of the first to associate the prism spectroscope with the Astronomie.

In 1863, it confirms that the the Moon does not have atmosphere, then in 1867 that of Mars contains steam. He studies the solar radiation and his disturbance by the Terrestrial atmosphere. Sent by the Office of longitudes in India for the observation of the eclipse of the sun in 1868, he discovers a method of observation of the solar protuberances in any time. It is during this observation that he notices an unknown line in the solar atmosphere. It is that of the Hélium, thus named by J. Norman Lockyer. It is distinguished knight from the Légion of honor in 1868. He escapes from Paris besieged by the Prussians in balloon in order to observe a solar eclipse with Oran.

He becomes member of the Academy of Science on February 10th 1873, then on May 26th 1874 is elected with the Bureau of longitudes. In 1874, it invents the “photographic revolver”, to be able to photograph the passage of the planet Venus in front of the Sun and goes until the Japan to obtain the best point of aiming. He is prize winner of the Médaille Rumford in 1876.

Jules Jansen pushes with the creation of the physical Observatoire of astronomy in Paris, decided in 1875. He presents a project of restoration of the castle of Meudon, starts to install various instruments of observation as of 1876, then obtains the required funds (more than one million frank of the time) to rebuild the buildings. Following the promulgation of the law found it on April 15th 1879, work start; a large cupola is created which always shelters instruments of observation. The Observatoire of Meudon remains one of the reference laboratories for the study of the Sun.

Starting from 1888, in spite of its age and its infirmity, it makes three times the rise of the Mont Blanc to establish an observatory there. It succeeds in after many risks making install glasses of 30  cm closest to the top, 4  800  m of altitude, to minimize the atmospheric disturbances. This observatory remained in place during fifteen years.

Jansen was honorary president of the French company of photography of 1891 with 1893, succeeding Eugene Péligot, and chair National union of the photographic companies of France in 1892.

Its memory

Jules Jansen shares the discovery of helium with sir Joseph Norman Lockyer. He published in 1904 the solar Atlas of photographs , with close to 6  000 catches of sight mainly obtained at the observatory of Meudon.

The Astronomical Company of France decrees each year since 1960 a Price Jules Jansen.

The town of Meudon named a place in its honor. A lunar crater bears its name (45,4°S, 40,3°E).

External bonds

  1. the epopee of Jules Jansen to the Mont Blanc on the site of the Observatory of Paris.
  2. the Creation of the observatory of Meudon by Francoise Launay of the Observatory of Paris.
  3. Venus transits per Gilbert Lavaux.
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