James Elliot, an astronomer who used light from distant stars to study planetary objects throughout the solar system, leading to his discovery of the rings of Uranus, died on March 3 at his home in Wellesley, Mass. He was 67.

His daughter Lyn said the cause was complications of cancer treatment.

Dr. Elliot spent his career, mostly at the Massachusetts Institute of Technology, scrutinizing planets by observing how much starlight they blocked. Using phenomena known as stellar occultations, he could observe changes in the brightness of a star when it was hidden by a planet, thus determining the planet’s size and the temperature and pressure of any atmosphere it had.

Occultations are rare, and to observe them one must predict when the planet will pass in front of a star, and where on the Earth its shadow will be cast. A high degree of coordination is necessary to ensure that multiple telescopes around the world are trained on a star at the precise moments that it is obscured by a planet.