# astronomical unit

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## 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 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.

## astronomical unit

[‚as·trə′näm·ə·kəl ′yü·nət]
(astronomy)
Abbreviated AU.
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.

## astronomical unit

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
References in periodicals archive ?
Observations on space-time are affected by where you measure them from, so the result you get from the previous definition of an astronomical unit differs by about 1,000 meters if you calculate it from the surface of Jupiter instead of Earth, German astronomer Sergei Klioner (http://www.
We would not yet have detected the Earth," says Jewitt, "if it were more than 600 astronomical units from the sun.
Plus, says Jones, LSST could detect an Earth-sized planet out to between 300 and 500 astronomical units, depending on how reflective its surface is.
5 astronomical units from Earth and the one-way radio signal time was approximately 45 minutes.
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 team also found that, at any given time, about 1% of bodies within 34 astronomical units of the Sun should linger around Uranus as temporary Trojans, and another 2% around Neptune.
Since Betelgeuse's radius is about five astronomical units, or five times the radius of Earth's orbit, which means the star's radius has shrunk by a distance equal to the orbit of Venus.
1 astronomical units (AU) in radius and could lie as close as 2.
The object orbits a whopping 44 astronomical units from its Sun-like host star GJ 504, better known as 59 Virginis.
2 astronomical units (AU) from the sun and an inner belt of silicate-rich asteroids centered at 2.
4 astronomical units (130 million miles) to the Sun.
Observations over the past year by Brett Gladman of the Observatoire de la Cote d'Azur in Nice, France, and his colleagues show that the comet's orbit takes it further than 200 astronomical units (AU) from the sun and as close as 44 AU.

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