Astronomy is the natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin, evolution, and physical and chemical properties. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets, while phenomena include supernova explosions, gamma-ray bursts, and cosmic microwave background radiation.
Astrophysics is a branch of astronomy that applies the principles of physics and chemistry to understand the nature of celestial bodies and cosmic phenomena. It encompasses the study of the Sun, stars, galaxies, exoplanets, the interstellar medium, and the cosmic microwave background, analyzing their luminosity, density, temperature, and chemical composition.