On March 10, 1977, astronomers discovered rings around Uranus!

Astronomers had long suspected that Uranus has rings, but the actual discovery happened by accident. A team of three astronomers was using NASA's Kuiper Airborne Observatory to observe the atmosphere of Uranus. They did this during a stellar occultation, which means that a background star was passing behind the planet. Seeing how the light from that star changes when it passed through the atmosphere could yield clues about the composition of Uranus. To their surprise, the star began to flicker before it was even eclipsed by Uranus. The star disappeared and reappeared five times as it passed behind the rings. At first they believed that Uranus had five rings, but more observations have revealed that it actually has 13 rings.