ZHANSEN Pierre Zhbl Cesar (Janssen Pierre-Jules-Csar)

(1824-1907)
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 he established a small observatory and started his own observations of the Sun. In 1865 received the position of professor of physics at the Architectural School. In 1868 he participated in the expedition, went to India to observe a total solar eclipse. In 1878 he became director of the newly established Medonskoy Astrophysical Observatory, which was headed until the end of life. In 1893 founded the observatory on Mount Blanc to meet the challenges of astrophysics, physics of the earth, meteorology.
Zhansen one of the first to use photographic and spectroscopic techniques in astronomy, especially in the study of the Sun. During the observation of a solar eclipse on Aug. 18, 1868, regardless of Dzh.Lokera applied a new method of observing prominences without eclipses, concluded that their gaseous nature of. For the first time registered a yellow line in the emission spectrum of prominences assigned later Dzh.Lonerom new element - helium. Compiled an atlas of the solar surface. He opened the chromosphere - the gaseous envelope of the Sun. The method for determination of chemical composition of the atmospheres of various planets on the lines and absorption bands in the spectrum of reflected sunlight from the planet, thus tried to detect water vapor in the atmosphere of Mars.

Zhansen 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 of his name, and the French Astronomical Society - Award.

Zhansen died in Meudon, December 23, 1907.