OCCULTATION

obscuring of the light of an astronomical body, most commonly a star, by another astronomical body, such as a planet or a satellite. Hence, a solar eclipse is the occultation of the Sun by the Moon. By carefully measuring the decrease in the intensity of large stars as they disappear behind the Moon, astronomers can determine their diameters (in angle) and ascertain whether they are binary systems (a pair of stars in orbit around their common centre of gravity). From occultations of stars by planets, asteroids, and satellites, astronomers are able to determine the precise sizes and shapes of the latter bodies in addition to the temperatures of planetary atmospheres. Astronomers unexpectedly discovered the rings of Uranus during a stellar occultation on March 10, 1977. Compare eclipse.