Astronomers use astronomical units (AU) instead of kilometers (km) because AU provides a more convenient and appropriate scale for measuring distances within our solar system. The distances between celestial objects in our solar system can be extremely large, with kilometers becoming impractical to use due to their vast numbers. AU, on the other hand, is based on the average distance between the Earth and the Sun, which is a more manageable unit for measuring distances within our solar system. Additionally, AU allows for easier comparison and understanding of distances between celestial bodies. Overall, AU provides a more suitable and comprehensible scale for astronomers to work with when studying objects within our solar system.
