Helium Emerges from the Sun: 1868 Eclipse Unveils a New Element

On Aug. 18, 1868, during a total solar eclipse in India, French astronomer Pierre Janssen used a spectroscope to observe a bright yellow line not matching any known element, signaling the discovery of helium; English astronomer Norman Lockyer independently identified the same line as a new element, later named helium after Helios. This was the first time spectroscopy revealed an element in an astronomical object before it was found on Earth, and helium would later prove essential for spaceflight and stellar physics.