Aug. 18, 1868: Helium is discovered

An vintage, wide black-and-white map depicts coastal regions from East Africa and the Arabian Peninsula across India and Southeast Asia on light beige paper. A light blue, curved band sweeps horizontally across the center, marking a path across the landmasses and bodies of water. The map is overlaid with French labels, grid lines, and black line drawings of geographical features, lit evenly across the page.

This 1868 map plots the path of the Aug. 18 eclipse. Credit: Internet Archive Book Images, via Wikimedia Commons

During the total solar eclipse of Aug. 18, 1868, two astronomers, Pierre Jules César Janssen of France and J. Norman Lockyer of England, each independently discovered a new line in the Sun’s spectrum. Lockyer thought it showed an undiscovered element, which he named helium. (In Greek mythology, Helios was the Sun god.) Although scientists would later show that helium is the second most abundant in the cosmos, it wasn’t found on Earth for another 27 years.

Michael E. Bakich is a contributing editor for Astronomy magazine. With degrees in astronomy and planetarium education, he has led many eclipse tours, published several books on observing, and logged thousands of hours at the eyepiece.

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