What is an astronomical unit?

Answer 1

The AU is a unit of measurement.
Astronomers use the astronomical unit (AU) to measure distances across the Solar System. One AU equals the mean distance from the Sun to Earth. That is approximately 93 million miles or 150 million kilometers.

Navigating spacecraft around the Solar System requires on accurate measurement of an AU. NASA's Jet Propulsion Lab (JPL) Deep Space Network bounced radar echoes off Venus in the 1960s to refine the value of an AU.

Light time. An alternative way to measure distances across the Solar System is in light time — lightseconds, lightminutes, lightdays, lightyears — the distance light travels in a unit of time.

Distances across the Solar System are vast when compared with travel across the surface of Earth. On the other hand, distances across the Solar System when compared with the breadth of the galaxy. For instance, the star nearest us — Proxima Centauri — is four lightyears away. That is about 253,000 AU from the Sun.

Answer 2

Its the distance from the Earth to the Sun--about 93 million miles(150 km). However, the planets don't travel in a perfect circle so the AU is technically defined differently. The AU is good for measuring ralatively short distances in our solar system, like the distance between the Earth and Jupiter. The lightyear is used to measure larger distances, like the distance to the nearest star from our solar system.

Answer 3

A unit of measurement. It's calculated by the distance between the sun and the Earth.

Answer 4

It's a distance measurement equal to the mean distance between the Earth and the Sun. About 93,000,000 miles.

HTH

Doug

Answer 5

1 AU is equal to the avergae distance of the earth to the Sun or 93,000,000 miles.

Answer 6

the mean dist. between sun and earth

Answer 7

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