Astronomy

http://www.sciencedaily.com/articles/a/astronomy.htm

Astronomy is one of the oldest sciences. Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation). Astronomers from early life have been performing an observation of the night sky and astronomical artifacts have been found from much earlier periods. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Since the 20th century astronomy has been split into observational and theoretical branches. Observational astronomy is focused on analyzing and collecting data and using basic principles of physics. Theoretical astronomy is oriented towards the developing of computers or models that would help describe the astronomical objects and phenomena. Amateur astronomers have contributed too many important astronomical discoveries, and astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena. The most frequently studied star is the Sun, a typical main-sequence dwarf star of stellar class G2 V, and about 4.6 Gyr in age. A sun is not considered a star but it certainly undergoes periodic changes in activity known as the sunspot cycle. The study of stars and stellar evolution is fundamental to our understanding of the universe.