Astronomical Unit - MSN Encarta

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Glossary: Astronomical Unit (AU)
ASTRONOMICAL UNIT (AU) 1 AU = 149,597,870.691 kilometers . Definition: An Astronomical Unit is approximately the mean distance between the Earth and the Sun.
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astronomical unit • noun a unit of measurement equal to the mean distance from the earth to the sun, 149.6 million kilometres. Perform another search of the Compact Oxford ...
Cambridge Astronomical Survey Unit
Contains information on the PDS and APM microdensitometer facilities, Carlsberg Meridian telescope, data archives, and processing center.

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Astronomical Unit (AU), unit of distance used in the measurement of orbits and trajectories within the solar system. One AU is the average distance between the Earth and the Sun. Its value has been established as, roughly, 149,600,000 km (92,956,000 mi) by means of radar-ranging studies of nearby celestial objects such as Venus or passing asteroids; these studies have enabled astronomers to determine the scale of the solar system with great accuracy.