During a total solar eclipse visible from India and Southeast Asia, astronomers Georges Rayet and Norman Pogson independently recorded an unfamiliar yellow emission line in the Sun's spectrum. English astronomer Norman Lockyer identified it days later as a new element, which he named helium after the Greek sun god Helios, marking the first element discovered in space before being found on Earth.
Total solar eclipses in the 19th century were prized scientific opportunities, since the Moon's disc blocking the Sun's overwhelming glare allowed astronomers to study the faint, wispy corona and chromosphere that were otherwise invisible. Teams fanned out across the eclipse's path through Asia, some funded by colonial scientific institutions eager to make a mark in the young field of spectroscopy.
When observers pointed their spectroscopes at the solar prominences visible during the eclipse's brief totality, they caught a bright yellow line close to, but distinctly different from, the well-known sodium D lines. French astronomer Georges Rayet and British astronomer Norman Pogson both noted the anomaly on August 18. It fell to Norman Lockyer and chemist Edward Frankland, working independently of the eclipse expeditions using new techniques to observe the Sun's spectrum without an eclipse, to argue convincingly that the line represented an undiscovered element. They named it helium. It would be another 27 years before William Ramsay isolated helium on Earth, from a uranium mineral, confirming that the mysterious solar gas existed in the ground beneath everyone's feet all along.
Key people: Norman Lockyer, Georges Rayet, Edward Frankland