Exactly 152 years ago, on August 18, 1868, a French astronomer discovered helium.
Pierre Jansen used
spectroscope for observing plasmaformations at the edge of the Sun's disk during an eclipse. He also invented a method for daily exploration of the solar edge on ordinary days. In the solar spectrum that day, in addition to the known spectral lines of hydrogen, a new bright yellow line was visible. Initially, the scientist mistook it for the sodium D line.