Astronomical Units or AU

The distance from Earth to Sun is 1 AU
Credit: NSO

The Astronomical Unit or AU is the average distance between the Earth and the Sun. It works out as 149,600,000 km.

Because of the huge distances involved in space, it is useful to use this as a unit for measuring distances in the Solar System. For example, it is much easier to say that Neptune is 30 AU from the Sun, rather than 4,504,300,000 km!

To give you a better idea of the scale of our galaxy, the nearest star to the Sun, Proxima Centauri, is roughly 268,000 AU from the Sun, whilst the centre of our galaxy, the Milky Way, is around 1,700,000,000 AU.