Astronomy: The natural science that deals with the study of celestial objects and phenomena originating outside the Earth's atmosphere. Celestial objects include stars, planets, dwarf planets, asteroids, comets, nebulae, star clusters, globular cluster and galaxies.
The basic activity of astronomy is observing celestial objects and measuring their properties such a mss, diameter, brightness and composition. Observations are usually made by way of some form of telescope. The types of telescopes used include visible light, radio, inferred, ultraviolet, X – ray, and gamma ray telescopes.
The invention of the telescope was a giant leap in astronomy allowing observations beyond the rage of the unaided eye. Further developments in telescope have opened up whole new ways of looking at the Universe. Professional astronomy has often come to be seen as equivalent to astrophysics
In the 20th century astronomy divided into two main fields. Observational Astronomy involves acquiring data from observations and analyzing that data using physics. Theoretical Astronomy is the development of computer models to describe astronomical objects and phenomena.
Today Observational and Theoretical Astronomy complement each other. The theoretical Seeks to explain observations and observations used to test the theoretical. Amateur astronomers have also contributed to many important astronomical discoveries making astronomy one of the few sciences that amateurs can still play an active role.