a unit of distance used in astronomy equal to the mean distance between the earth and the sun. 1 astronomical unit is equivalent to 1.495 × 1011 metres or about 9.3 × 107 miles
(AU or au) A unit of length that is used for distances, especially within the Solar System. It is effectively the mean distance between Earth and Sun. It is defined formally in terms of Kepler's third law and the Gaussian gravitational constant. One astronomical unit is equal to 149 597 870 kilometers or 499.005 light-seconds.
A measure for distance within the solar system equal to the mean distance between earth and sun, that is, about 92,956,000 miles (149,598,000 kilometers).
The semimajor axis of the elliptical orbit of earth.
"We would not yet have detected the Earth," says Jewitt, "if it were more than 600 astronomical units from the sun." And that's assuming researchers knew where to look.
The newly discovered object lies an estimated 43 astronomical units from the sun--43 times the Earth-sun distance--and appears to have the largest intrinsic brightness of any Kuiper belt resident, researchers report in a July 5 circular of the International Astronomical Union.
The camera revealed that the dust is confined to a region around the star no larger than 6.1 astronomical units (AU) in radius and could lie as close as 2.5 AU.
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