The Astronomical Unit

The astronomical unit (AU) is a measurement used by astronomers to describe distances within our solar system. It’s roughly equal to the average distance between Earth and the Sun, about 93 million miles (150 million kilometers). The AU provides a convenient way to compare how far planets and other objects are from the Sun without using large numbers. For example, Mars is about 1.5 AU from the Sun. Since the AU is based on Earth's orbit, it helps scientists communicate and calculate planetary positions and distances more easily.