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astronomical unit

   Also found in: Dictionary/thesaurus, Medical, Financial, Acronyms, Wikipedia, Hutchinson 0.04 sec.
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.

astronomical unit (AU)

Length of the semimajor axis of Earth's orbit around the Sun, 92,955,808 mi (149,597,870 km), often defined simply as the average distance from Earth to the Sun. Direct measurement through the parallax method cannot be used for accurate determinations, because the Sun's glare blots out the light of the background stars necessary to make the measurement. The most precise values have been obtained by measuring the distance from Earth to other objects orbiting the Sun. This indirect method requires an accurate proportional mathematical model of the solar system; once the distance to one planet or other object is determined, then the distance to the Sun can be calculated.
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The Kuiper belt extends outward from the orbit of Pluto to about 70 times the Earth-sun distance, which defines an astronomical unit (AU).
Outer limits: solar system at the fringe by Cowen, Ron / Science News
To make the millions of kilometers between the planets easier to visualize, scientists use a scale called astronomical unit (AU), where 1 AU equals the distance from Earth and Sun (about 149,600,000 kilometers).
Are we there yet? (Math Skills) by Science World
An order for 56 circuit card assemblies will be followed six months later-- too late to be added to the first production run-- by an order for one or two or three of the same item at a relatively astronomical unit price.
The case for the $435 hammer by Fairhall, James / Washington Monthly
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