Astronomical Unit Measure Redefined

Sizing up a new measuring ruler for the solar system 

Improved accuracy (Image: Stocktrek Images/Getty)

• 16:18 17 September 2012 by Jacob AronFor similar stories, visit the Solar System Topic Guide

The sun still shines as bright, but according to the International Astronomical Union (IAU), its precise distance from us has just changed.

At a recent meeting of the IAU in Beijing, China, members unanimously voted to redefine the astronomical unit, or AU, which has long served as the fundamental unit of distance between objects in the solar system. According to the voters, the official definition of the AU is now exactly 149,597,870,700 metres, and the unit should be written "au".

Historically, calculating the astronomical unit was based on the average distance between Earth and the sun, or 149,597,870,691 metres. An amendment in 1976 complicated things by also tying the unit to the sun's mass.

Although the recent decision doesn't alter the value by much, it simplifies things and should improve the accuracy of distance measurements over time.

More: http://www.newscientist.com/article/dn22276-sizing-up-a-new-measuring-ruler-for-the-solar-system.html

Source: New Scientist Magazine.

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