Pierre Jules César Janssen was a French astronomer who along with the English scientist Sir Joseph Norman Lockyer is credited with discovering the gas helium. In 1868 Janssen discovered how to observe solar prominences without an eclipse. On August 18 of that same year, while observing an eclipse of the Sun in India, he noticed a bright yellow line with a wavelength of 587.49 nm in the spectrum of the chromosphere of the Sun. Wikipedia
The definitive Wikipedia entry for Pierre Janssen. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Pierre_Janssen
