astronomical unit

Also known as AU, astronomic unit, heliocentric distance, ua

mean distance between Earth and the Sun, common length reference in astronomy

AI overview

An astronomical unit (AU) is the average distance between Earth and the Sun, which astronomers use as a standard measurement for distances within our solar system. This reference point makes it easier to describe and compare how far planets, asteroids, and other objects are from the Sun without using extremely large numbers.

AI-generated from the Wikipedia summary — may contain errors.

Wikidata facts

Instance of: non-SI unit mentioned in and accepted with the SI
Image: Astronomical unit.svg

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short name: au
NCI Thesaurus ID: C71246
unit symbol: а.и.
different from: AE
on focus list of Wikimedia project: Wikipedia:Vital articles/Level/4
conversion to SI unit: 149597870700
measured physical quantity: length
opposite of: ECEF
Wikidata SPARQL query equivalent: wd:Q1811 p:P2370/psn:P2370 [wikibase:quantityAmount ?source; wikibase:quantityUnit ?base]. ?item p:P2370/psn:P2370 [wikibase:quantityAmount ?target; wikibase:quantityUnit ?base]. BIND(?source / ?target as ?value)

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Encyclopedic overview

The astronomical unit (symbol: au or AU) is a unit of length defined as 149597870700 m. 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.

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. One au is approximately equivalent to 499 light-seconds.

Excerpted from Wikipedia’s “astronomical unit” article, available under the CC BY-SA 4.0 licence.