Definition

astronomical unit (AU)

Part of the IT standards and organizations glossary:

An astronomical unit (AU) is the mean distance between the center of the Earth and the center of the sun. The actual distance varies depending on the time of year, because the Earth's orbit around the sun is not a perfect circle. The mean, or average, separation is approximately 1.4959787 x 10 11 meters, which is 1.4959787 x 10 8 kilometers or 9.2955807 x 10 7 miles.

Distances within the solar system are commonly measured in AU. Mercury, the innermost planet, orbits at a mean distance of about 0.4 AU from the sun, while Neptune, one of the most distant planets known, has an average orbital radius of about 30 AU. Interstellar and intergalactic distances are expressed in light-years or parsec s.

Interestingly, the Earth is closest to the Sun during the month of January, and farthest during July. The variation is about ±1 percent of the mean distance. Seasonal weather results from the tilt of the Earth's axis, and is not significantly affected by the distance of the planet from the sun.

Also see the Table of Physical Units and Constants.

This was last updated in January 2011
Posted by: Margaret Rouse

Related Terms

Definitions

  • Microsoft Most Valuable Professional (MVP)

    - A Microsoft Most Valuable Professional (MVP) is an individual recognized by Microsoft for exceptional technical expertise and a talent for sharing knowledge within their technical community. (SearchWindowsServer.com)

  • standard

    - A standard is a generally agreed-upon technology, method or format for a given application. Official standards are overseen by one of a number of governing bodies that exist to promote their develo... (WhatIs.com)

  • standards organization

    - A standards organization, sometimes referred to as a standards body, is an organization with authority to endorse official standards for given applications. (WhatIs.com)

Glossaries

  • IT standards and organizations

    - Terms related to information technology (IT) standards, including definitions about IT organizations and words and phrases about policies and compliance.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question About astronomical unit (AU)Powered by ITKnowledgeExchange.com

Get answers from your peers on your most technical challenges

Tech TalkComment

Share
Comments

    Results

    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.