How is an astronomical unit defined?

1 Answer
Phillip E.
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.

Explanation:

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.

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