Date of Birth: 02/22/1824
Place of Birth: Paris
Janssen, Pierre Jules Cesar
Janssen, Pierre Jules Cesar (Janssen, Pierre-Jules-Cesar) (1824-1907), French astronomer. Born February 22, 1824 in Paris. In 1852 he graduated from the University of Paris. He taught mathematics and physics in high school, worked as a tutor. In 1862, with a small private observatory and started observing the sun. In 1865 he obtained a position of professor of physics in the School of Architecture. In 1868 he participated in the expedition, otpravivsheysyav India to observe the total solar eclipse. In 1878 he became director of the newly created Meudon Astrophysical Observatory, headed until his death. In 1893 he founded the observatory on Mount Blanc to address the problems of astrophysics, earth physics, meteorology.
Janssen was among the first to apply photographic and spectroscopic techniques in astronomy, especially when the sun study. During nablyudeniyasolnechnogo eclipse of August 18, 1868, regardless of Dzh.Lokera used a new method of observing prominences is the eclipse, concluded that their gaseous nature. For the first time I registered the yellow line in the emission spectrum of the prominences, later ascribed Dzh.Lonerom new element - helium. Compiled atlas of the solar surface. Opened chromosphere - the gaseous envelope of the sun. A method of determining the chemical composition of the atmospheres of different planets on the lines and absorption bands in the spectrum of reflected sunlight from the planet; I tried thus detect water vapor in the Martian atmosphere.
Janssen was a foreign member of the St. Petersburg Academy of Sciences, a member of the Royal Society of London. The Paris Academy of Sciences established a medal in his name, and the French Astronomical Society - Prize.
Janssen in Meudon Died December 23, 1907.