Janssen and Lockyer, 1868. Pierre Jules Cesar Janssen (1824-1907), French astronomer, left, and Joseph Norman Lockyer (1836-1920), English astronomer. In 1868 while making spectroscopic studies of solar prominences, working independently, both men observed a yellow line in the solar spectrum. Lockyer named it Helium from helios, sun. Obverse of a commemorative medal.

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