|occultation (ŏk'ŭl-tā'shən) Pronunciation Key
The passage of one celestial object in front of another, temporarily blocking the more distant object from view. Occultations can provide information about the existence and measurements of the obscuring object. For example, when an asteroid passes in front of a star, the star is temporarily obscured to an observer on Earth, thus revealing the presence and approximate size of the asteroid. In 1977, astronomers were able to identify the rings around the planet Uranus when the otherwise invisible rings were observed to occult a background star. Occultations have also led to the discovery of more distant objects in space, such as binary stars and extrasolar planets. Compare transit.
complete obscuration of the light of an astronomical body, most commonly a star, by another astronomical body, such as a planet or a satellite. Hence, a total solar eclipse is the occultation of the Sun by the Moon. By carefully measuring the decrease in the intensity of some stars as they disappear behind the Moon, astronomers can determine their angular diameters and ascertain whether they are binary systems (a pair of stars in orbit around their common centre of gravity). Astronomers are able to determine the precise sizes and shapes of planets, asteroids, and satellites, in addition to the temperatures of planetary atmospheres, from occultations of stars. During a stellar occultation on March 10, 1977, astronomers unexpectedly discovered the rings of Uranus. Compare eclipse.
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