Measuring space

 

Calls made to change the astronomical unit of measurement.

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An astronomer, speaking in New Scientist magazine, has called for changing the astronomical unit (AU) as the standard unit measure of distance in the solar system.
 
An AU, approximately the distance between the Sun and the Earth (149,597,870.691 kilometres), has become the standard unit of measurement in astronomy. One expert, however, suggests that due to changes in mass of the Sun, and therefore its orbit, this should change.
 
A more formal definition of the AU outlines it as, ‘the radius of an unperturbed circular orbit that a massless body would revolve about the Sun in 2π/k days (one year) where k is a constant derived from a fixed estimate of the Sun's mass.’

The Sun’s mass

And there lies the problem…the Sun’s mass. Due to a phenomenon known as ‘solar shedding,’ the sun has been losing mass
 
Speaking to New Scientist Peter Noerdlinger, an astronomer at St Mary's University in Canada, said: "Because the radiation carries away energy, and given that Einstein showed the equivalence of mass and energy, the mass has to go down."
 
Therefore, he argues, that the AU is not a constant and therefore only suitable for casual and not scientific use. He suggests adopting metres instead.
 

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