The total solar eclipse of August 18, 1868
On August 18, 1868 the Moon's shadow swept across parts of India and Southeast Asia, giving astronomers a rare chance to study the solar corona in darkness.
Observations by Janssen and Lockyer
The French astronomer Jules Janssen used a spectroscope and noticed a bright yellow line in the Sun's atmospheric spectrum that did not match any known substance.
At almost the same time the English scientist Norman Lockyer analyzed sunlight from his London observatory and reached the same conclusion.
Naming and later confirmation
Lockyer proposed naming the new element after the Greek sun god Helios, calling it helium.
It was not until 1895 that the Scottish chemist Sir William Ramsay isolated helium from a uranium mineral on Earth, confirming its extraterrestrial origin.
Scientific and everyday significance
Today helium is the second most abundant element in the universe and is used in cryogenics, as a carrier gas in gas chromatography, and to fill balloons and airships.
The discovery first demonstrated that chemical elements exist beyond Earth and laid the foundation for modern astronomical spectroscopy.