Spectral line observed during solar eclipse leading to the discovery of helium

When the Sun Revealed a New Element

At the observation site where French astronomer Pierre Janssen was preparing for the solar eclipse, there was a sense of tension. It was August 1868, and Janssen held in his hands a spectroscope, a device capable of breaking down light into individual spectral lines. This method had already enabled the discovery of several elements on Earth, and Janssen hoped to similarly unveil the secrets of the Sun. The eclipse was to be an ideal opportunity when the solar corona would become visible.

During the eclipse, Janssen observed an unusual yellow spectral line that did not correspond to any known element. This discovery was so surprising that he realized its significance only later. Independently, British astronomer Norman Lockyer observed the same line and, together with chemist Edward Frankland, identified it as evidence of a previously unknown element. Helium, named after the Greek word for the Sun, was the first element discovered outside Earth.

The discovery of helium had far-reaching consequences. It opened new possibilities for studying the chemical composition of stars, leading to the development of astrophysics. The realization that elements could be discovered beyond our planet changed our view of the universe. Helium became a key element not only in science but also in industry, and its discovery on the Sun was the first step towards understanding the composition of the universe.