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Pierre Jules César Janssen.

Pierre Jules César Janssen.

1868: A French astronomer spots an unknown element, now known as helium, in the spectrum of the sun during a much-anticipated total eclipse. The event marks the first discovery of an “extraterrestrial” element, as helium had not yet been found on Earth.
Astronomers 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. 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. But until 1868, they thought the sun’s spectrum could only be observed during an eclipse.
French astronomer Pierre Jules César Janssen camped out in Guntoor, India, to watch as the moon passed in front of the sun and revealed the solar prominences