Astronomical unit
Mean distance between Earth and the Sun / From Wikipedia, the free encyclopedia
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This article is about the unit of length. For constants, see astronomical constant. For units in astronomy, see astronomical system of units. For other uses of "AU", see Au.
The astronomical unit (symbol: au,[1][2][3][4] or AU) is a unit of length defined to be exactly equal to 149,597,870,700 m.[5] Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its modern redefinition in 2012.
Quick Facts General information, Unit system ...
Astronomical unit | |
---|---|
General information | |
Unit system | Astronomical system of units (Accepted for use with the SI) |
Unit of | length |
Symbol | au or AU or AU |
Conversions | |
1 au or AU or AU in ... | ... is equal to ... |
metric (SI) units | 1.495978707×1011 m |
imperial & US units | 9.2956×107 mi |
astronomical units | 4.8481×10−6 pc 1.5813×10−5 ly 215.03 R☉ |
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The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec.[6] One au is equivalent to 499 light-seconds to within 10 parts per million.