Working feverishly over the next few weeks, Janssen built the first spectrohelioscope, a device specifically designed to examine the spectrum of the sun. The Spectrohelioscopeįrom 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. This was the first observation of this particular spectral line, and one possible source for it was an element not yet discovered on the earth. Present, though not immediately noticed or commented upon, was a bright yellow line later measured to have a wavelength of 587.49 nm in the spectrum of the Sun. 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. In 1868 Janssen discovered how to observe solar prominences without an eclipse. The 1868 Eclipse and a strange Spectral Line But until 1868, they thought the sun’s spectrum could only be observed during an eclipse. Scientists wanted to study the bright red flames that appeared to shoot out from the sun, now known to be dense clouds of gas called solar prominences. To see the eclipse of 1870 he escaped from besieged Paris in a balloon (that eclipse was obscured by cloud cover, however).Īstronomers had been eagerly awaiting a total solar eclipse since 1859, when German physicist Gustav Kirchhoff figured out how to use the analysis of light to deduce the chemical composition of the sun and the stars. In 1861 – 18, 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. Thus in 1857 Janssen went to Peru in order to determine the magnetic equator. His energies were mainly devoted to various scientific missions entrusted to him. Despite his handicap, Janssen was an avid traveller always in pursuit of scientific knowledge. He taught at the Lycée Charlemagne in 1853, and in 1865 he became professor of physics at the École Speciale d’Architecture in Paris. Janssen continued studying mathematics in his spare time and he eventually entered the faculty of sciences of the University of Paris to study mathematics and physics, where he graduated in 1852 and obtained his doctorate in 1860. He studied at home and, at the age of 16, when he started to work as a bank clerk. An accident when he was young left him extremely lame and it is for this reason that he was unable to go to school. Janssen also is credited with discovering the gaseous nature of the solar chromosphere. When watching the total eclipse on Augin Madras, British India, French astronomer Pierre Janssen discovered the new chemical element Helium.
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