Pierre Jules César Janssen(redirected from Pierre Jules Cesar Janssen)
Janssen, Pierre Jules César
Born Feb. 22, 1824, in Paris; died Dec. 23, 1907, in Meudon. French astronomer. Member of the Paris Academy of Sciences (1873) and of the Royal Society of London (1875). One of the founders of the spectral analysis of celestial bodies.
In 1868 and independently of J. N. Lockyer, Janssen invented the spectral method of observing solar prominences on the limb of the sun’s disk during periods when the sun was not in eclpse.