Hundreds of dark lines hidden in sunlight opened up the chemistry of the stars

In 1814, optician Joseph von Fraunhofer split sunlight with a prism and noticed it wasn't a smooth rainbow: hundreds of thin dark lines interrupted it at fixed positions. He catalogued the major ones by letter, without knowing why they existed. Decades later, physicists matched those lines to the signatures of specific elements, turning starlight into a chemistry report from objects no one could ever touch.

— Joseph von Fraunhofer, Bestimmung des Brechungs- und Farbenzerstreuungsvermögens verschiedener Glasarten — 1814–1815