Home > Pierre Jules César Janssen

Janssen was born in Paris and studied mathematics and physics at the faculty of sciences. He taught at the lycée Charlemagne in 1853, and in the school of architecture 18651865 is a common year starting on Sunday. Events January 31 American Civil War: Confederate General Robert E. Lee becomes general-in-chief. February 17 American Civil War: Columbia, South Carolina burns as Confederate forces flee from advancing Union forc – 1871Events January January 18 The member-states of the North German Confederation unite into a single nation-state known as the German Empire. The King of Prussia is declared the first German Emperor as Wilhelm I of Germany. January 28 France surrenders to en, but his energies were mainly devoted to various scientific missions entrusted to him. Thus in 1857Events January 9 Earthquake at Fort Tejon, California with an estimated magnitude of 7. 9 February 16 The National Deaf Mute College (later renamed Gallaudet University) is established in Washington, DC becoming the first school for the advanced education he went to PeruFor other uses, see Peru (disambiguation The Republic of Per ( Spanish: Per Quechua, Aymara: Piruw is a country in western South America, bordering with Ecuador and Colombia to the north, Brazil to the east, Bolivia to the east, south-east and south, Chil in order to determine the magnetic equatorIn geography, the equator is an imaginary line drawn around a planet, halfway between the poles, where the surface of the roughly spherical planet is parallel to the axis of rotation. The equator divides the surface into the Northern Hemisphere and the So; in 18611861 is a common year starting on Tuesday. Events January January 1 Benito Juarez captures Mexico City January 2 Friedrich Wilhelm IV of Prussia dies and is succeeded by Wilhelm I January 3 American Civil War: Delaware votes not to secede from the United – 1862Events January-March January 10 End of term for John Gately Downey, 7th Governor of California. He is succeeded by Amasa Leland Stanford. January 30 The first American ironclad warship, the USS Monitor is launched. February 1 Julia Ward Howe's " Battle Hy and 1864Events January March January 21 Maori Wars: The Tauranga Campaign starts. February 27 American Civil War: The first Northern prisoners arrive at the Confederate prison at Andersonville, Georgia. March 1- Alejandro Mon Menendez takes office as Prime Minist, he studied telluric absorption in the solar spectrum in Italy and Switzerland; in 1867 he carried out optical and magnetic experiments at the Azores; he successfully observed both transits of Venus, that of 1874 in Japan, that of 1882 at Oran in Algeria; and he took part in a long series of solar eclipse-expeditions, e.g. to Trani (1867), Guntur ( 1868), Algiers ( 1870), Siam ( 1875), the Caroline Islands ( 1883), and to Alcosebre in Spain ( 1905). To see the eclipse of 1870 he escaped from besieged Paris in a balloon (that eclipse was obscured by cloud cover, however).

At the great Indian eclipse of 1868 he demonstrated the gaseous nature of the red prominences, and devised a method of observing them under ordinary daylight conditions. One main purpose of his spectroscopic inquiries was to answer the question whether the Sun contains oxygen or not. An indispensable preliminary was the virtual elimination of oxygen-absorption in the Earth's atmosphere, and his bold project of establishing an observatory on the top of Mont Blanc was prompted by a perception of the advantages to be gained by reducing the thickness of air through which observations have to be made. This observatory, the foundations of which were fixed in the snow that appears to cover the summit to a depth of ten metres, was built in September 1893, and Janssen, in spite of his sixty-nine years, made the ascent and spent four days taking observations. In 1875 he was appointed director of the new astrophysical observatory established by the French government at Meudon, and set on foot there in 1876 the remarkable series of solar photographs collected in his great Atlas de photographies solaires ( 1904). The first volume of the Annales de l'observatoire de Meudon was published by him in 1896. He died at Meudon.

A crater on Mars was named in his honor.

This article incorporates text from the public domain 1911 Encyclopædia Britannica. 1911 Britannica