1-158-985 - Oxford Science Archive/Heritage Images

Pierre Janssen and Joseph Norman Lockyer, French and English astronomers, 1868. Pierre Jules Cesar Janssen (1824-1907), left, and Joseph Norman Lockyer (1836-1920). 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.