How is an astronomical unit defined?

1 Answer
Dec 16, 2015

The Astronomical Unit is based upon the average distance of the Earth from the Sun. It is now an international standard unit.


The Astronomical Unit or AU was originally the average of the Earth's perihelion and aphelion distances from the Sun.

Due to irregularities in the Earth's orbit there needs to be a better definition.

Now the Astronomical Unit is defined to be an international standard unit. It is exactly 149,597,870,700 metres.