It's not accurate to say that planets have an "astronautical unit." The astronomical unit (AU) is a unit of distance used primarily in astronomy. It's defined as the average distance between the Earth and the Sun.

Here's how it works:

* 1 AU = 149.6 million kilometers (93 million miles)

* We use AU to express the distances of planets from the Sun. For example, Mars is about 1.52 AU from the Sun.

Key point: Planets themselves don't have their own unique "astronautical unit." The AU is a universal unit for measuring distances within our solar system.