- (astronomy) The mean distance from the Earth to the Sun (semi-major axis of Earth's orbit). Approximately 149,600,000 kilometres (symbol AU), used to measure distances in the solar system. By definition, when used to describe the motion of bodies within solar system, solar systems, the heliocentric gravitational constant is equal to (0.017 202 098 95)Â² AUÂ³/dÂ² (IERS Conventions (1996), D. D. McCarthy? ed., IERS Technical Note 21, Observatoire de Paris, July 1996); hence 1 AU = 149,597,870,691Â±30 km.
- French: unité astronomique
- German: Astronomische Einheit
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