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light-year

light-year, in astronomy, unit of length equal to the distance light travels in one sidereal year. It is 9.461 × 10¹² km (about 6 million million mi). Alpha Centauri and Proxima Centauri, the stars nearest our solar system, are about 4.3 light-years distant. See also parsec.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2007, Columbia University Press. All rights reserved.

More on light-year from Infoplease:

light-year: meaning and definitions - light-year: Definition and Pronunciation
Astronomical Constants - Astronomical Constants Light-year (distance traveled by light in one year) 5,880,000,000,000 mi ...
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