Astronomy is the study of the universe, namely the objects we observe, like the Moon, Sun, and planets in our Solar System; stars; our Milky Way Galaxy, and other galaxies; and, a host of other celestial objects and phenomena, like nebulae, and black holes.

Astronomy is a multidisciplinary science. It is intertwined with the study of physics, chemistry, mathematics, computer science, geology and biology.

Unlike most other fields of science, astronomers are unable to observe a system entirely from birth to death; the lifetime of worlds, stars, and galaxies span millions to billions of years. Instead, astronomers must rely on snapshots of bodies in various stages of evolution to determine how they formed, evolved and died. Thus, theoretical and observational astronomy tend to blend together, as theoretical scientists use the information actually collected to create simulations, while the observations serve to confirm the models — or to indicate the need for tweaking them.

Astronomy is broken down into a number of sub fields, allowing scientists to specialize in particular objects and phenomena.