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How did a stellar occultation reveal the rings of Uranus?

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Images obtained by Voyager 2. — Uranus Two views of the southern hemisphere of Uranus, produced from images obtained by Voyager 2 on Jan. 17, 1986. In colours visible to the unaided human eye, Uranus is a bland, nearly featureless sphere (left). In a colour-enhanced view processed to bring out low-contrast details, Uranus shows the banded cloud structure common to the four giant planets (right). From the polar perspective of Voyager at the time, the bands appear concentric around the planet's rotational axis, which is pointing nearly toward the Sun. Small ring-shaped features in the right image are artifacts arising from dust in the spacecraft's camera.

The rings of Uranus were discovered unexpectedly on March 10, 1977, during a stellar occultation—an event where a planet passes between a star and Earth, temporarily blocking the star's light.12

Astronomer James L. Elliot and his colleagues were observing the event, hoping to derive an accurate estimate of the planet's diameter. However, they observed the star’s light dim briefly five times at a significant distance from the planet's atmosphere, both before and after the main occultation occurred. These repeated, brief obscurations indicated that the planet was encircled by a system of narrow, opaque rings. This discovery, which was also supported by observations from the Kuiper Airborne Observatory, marked the first time rings had been identified around a planet other than Saturn.234