Why do astronomers have to uses au to measure distance in space?

Astronomers use astronomical units (AU) to measure distances in space because it provides a convenient scale for the vast distances involved. One AU is defined as the average distance from the Earth to the Sun, approximately 93 million miles or 150 million kilometers. This unit simplifies calculations and comparisons of distances within our solar system, making it easier to understand the relative positions of planets and other celestial bodies. Using AU helps to avoid the impracticality of using larger units like kilometers or miles, which can lead to unwieldy numbers.