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How were Uranus's rings discovered in 1977?

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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 in 1977 by American astronomer James L. Elliot and his colleagues during a stellar occultation.1

An occultation occurs when a celestial body, such as a planet, passes between a star and Earth, temporarily blocking the star's light. During this event, researchers unexpectedly observed the star dim briefly five times both before and after the planet itself occulted the star. These repeated dips in brightness indicated that the planet was encircled by five narrow rings.21

The discovery was made using the Kuiper Airborne Observatory, a specially instrumented jet transport aircraft that allowed astronomers to conduct observations from high altitudes to avoid interference from Earth's lower atmosphere. This finding marked the first time a ring system had been identified around a planet other than Saturn.31