astronomical unit


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astronomical unit

astronomical unit (AU), mean distance between the earth and sun; one AU is c.92,960,000 mi (149,604,970 km). The astronomical unit is the principal unit of measurement within the solar system, e.g., Mercury is just over 1-3 AU and Pluto is about 39 AU from the sun.
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astronomical unit

(AU or au) A unit of length that is used for distances, especially within the Solar System. It is effectively the mean distance between Earth and Sun. It is defined formally in terms of Kepler's third law and the Gaussian gravitational constant. One astronomical unit is equal to 149 597 870 kilometers or 499.005 light-seconds.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

astronomical unit

[‚as·trə′näm·ə·kəl ′yü·nət]
(astronomy)
Abbreviated AU.
A measure for distance within the solar system equal to the mean distance between earth and sun, that is, about 92,956,000 miles (149,598,000 kilometers).
The semimajor axis of the elliptical orbit of earth.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

astronomical unit

a unit of distance used in astronomy equal to the mean distance between the earth and the sun. 1 astronomical unit is equivalent to 1.495 × 1011 metres or about 9.3 × 107 miles
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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"We would not yet have detected the Earth," says Jewitt, "if it were more than 600 astronomical units from the sun." And that's assuming researchers knew where to look.
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This object lies 43.3 astronomical units (6.49 billion km) from the Sun and is incredibly dim, 25.6 in magnitude.
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The camera revealed that the dust is confined to a region around the star no larger than 6.1 astronomical units (AU) in radius and could lie as close as 2.5 AU.
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