Astronomy is the science dedicated to the study of celestial bodies. It tries to determinate their origin, evolution, physical and chemical properties.
Astronomy is one of the rare sciences where amateurs can still play an active role in the evolution of the domain, mainly through their observations. It is a popular pass-time, and many asteroids and various transient events are still being discovered by amateurs nowadays.
Modern professional astronomy is split in two categories: observational astronomy and theoretical astrophysics. The former focuses on the acquisition of data via visual observations, building and maintaining appropriate instruments for the task and process the gathered data; the latter rather analyses theoretical computer or analytic models. Both domains complement each other. Theories are created by astrophysicians from the observations made, and further observations test the fundamental theories created.