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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.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

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