On this day in 1868 - August 18th - during a total solar eclipse French astronomer Pierre Janssen observed an unknown line in the spectrum of the Sun, which turned out to be a new element, helium.

The same result was found independently by British astronomer Norman Lockyer, and both Janssen's and Lockyer's communications were presented to the French Academy of Sciences on October 26, 1868.

Mona Evans
For news, activities, pictures and more, sign up to the Astronomy Newsletter!