Astronomy is the study of the stars and other celestial bodies. It is an ancient science that dates back to the Babylonians, Egyptians, and Greeks. Astronomers use telescopes and other instruments to observe and measure the positions, motions, and properties of celestial objects. They also use mathematical models to explain and predict the behavior of these objects. Astronomy is a branch of physics and is closely related to astrophysics, which is the study of the physical and chemical properties of stars and other celestial bodies.