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Pierre Janssen was a French astronomer who in 1868 discovered the chemical element helium and how to observe solar prominences without an eclipse. His work was independent of that of the Englishman Sir Joseph Norman Lockyer, who made the same discoveries at about the same time.
- The Editors of Encyclopaedia Britannica
Pierre Jules César Janssen (22 February 1824 – 23 December 1907), usually known as Jules Janssen, was a French astronomer who, along with English scientist Joseph Norman Lockyer, is credited with discovering the gaseous nature of the solar chromosphere, but there is no justification for the conclusion that he deserves credit for the co ...
French astrophysicist Pierre Jules Janssen traveled across the world in an attempt to understand the cosmos, and was the first to sight the wavelength pattern of helium in his spectroscope.
- Youth and Education
- An Avid Observer of Solar Eclipses
- The 1868 Eclipse and A Strange Spectral Line
- The Spectrohelioscope
- The Discovery of Helium
- A Pioneer in Astrophotography
Janssen was born in Paris in 1824. An accident when he was young left him extremely lame and it is for this reason that he was unable to go to school. He studied at home and, at the age of 16, when he started to work as a bank clerk. Janssen continued studying mathematics in his spare time and he eventually entered the faculty of sciences of the Un...
Thus in 1857 Janssen went to Peru in order to determine the magnetic equator. In 1861 – 1862 and 1864, 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 A...
In 1868 Janssen discovered how to observe solar prominences without an eclipse. While observing the solar eclipse of August 18, 1868, at Guntur, Madras State (now in Andhra Pradesh), British India, he noticed bright lines in the spectrum of the chromosphere, showing that the chromosphere is gaseous. Present, though not immediately noticed or commen...
From the brightness of the spectral lines, Janssen realized that the chromospheric spectrum could be observed even without an eclipse, if only he could just figure out how to block other wavelengths of visible light. Working feverishly over the next few weeks, Janssen built the first spectrohelioscope, a device specifically designed to examine the ...
Independently of Jenssen, Joseph Norman Lockyer in England was working on the same problem and set up a new, relatively powerful spectroscope on October 20, 1868, and observed the emission spectrum of the chromosphere during broad daylight, including same yellow line. In stunning synchronicity, the two scientists’ papers arrived at the French Acade...
However, it was his ‘L’Atlas de Photographies Solaires’, published in 1904, which made Janssen one of the great pioneers of astrophotography and one of the founders of modern solar physics. This remarkable work contains some 6,000 photographs of the Sun taken in the years 1876 to 1903 from the newly established Meudon Observatory, near Paris, which...
The French astronomer Pierre Janssen had already made his name in the field of the solar spectrum. He had invented a much-improved astronomical spectroscope with the instrument maker Ignazio Hofmann, although the two men quickly fell out bitterly about whose contribution was greatest.
Aug 18, 2014 · Born in Paris, Pierre Janssen suffered an accident as a child that left him permanently lame. He studied mathematics and physics at the University of Paris, eventually becoming a professor of architecture there in 1865.
May 21, 2018 · Janssen, Pierre Jules César (b. Paris, France, 22 February 1824; d. Meudon, France, 23 December 1907) physical astronomy, spectroscopy, photography. Janssen was born into a cultivated family. His father was a musician of Belgian descent, and his maternal grandfather was the architect Paul-Guillaume Le Moyne.
