Astronomy is the science that studies the laws of the stars. It is a natural science that studies celestial objects which include planets, moons, stars, nebulae, galaxies, and comets. It also studies other phenomena which includes supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. Simply stated, astronomy studies everything that originates beyond Earth’s atmosphere. (Cosmology is a branch of astronomy that studies the universe as a whole.)
Astronomy is one of the few sciences in which amateurs play an active role. This is especially true for the discovery and observation of transient events. Amateur astronomers have helped with many important discoveries, such as finding new comets.