On Aug. 18, 1868, a French astronomer named Pierre Jules César Janssen discovered helium while observing a total solar eclipse in India.
During the eclipse, Janssen was using a spectroscope to look at the spectrum of light emitted by the sun. This tool allows scientists to determine what elements they're looking at. While observing solar prominences during the eclipse, Janssen noticed a bright yellow line that didn't correspond to any elements that was not yet discovered on Earth. Thirteen years later, the Italian physicist Luigi Palmieri found the first evidence of helium on Earth in the lava of Mount Vesuvius.
00:03In 1868, a French astronomer named Pierre-Jules César Janssen discovered helium while observing a total solar eclipse in India.
00:10During the eclipse, Janssen was using a spectroscope to look at the spectrum of light emitted by the sun.
00:15This tool allows scientists to determine what elements they're looking at.
00:18While observing solar prominences during the eclipse, Janssen noticed a bright yellow line that didn't correspond to any elements that had been discovered on Earth.
00:25Thirteen years later, the Italian physicist Luigi Palmieri found the first evidence of helium on Earth in the lava of Mount Vesuvius.
00:32And that's what happened on this day in space.
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