EARLY ASTRONOMYEarly cultures identified celestial objects with gods and spirits. They related these objects (and their movements) to phenomena such as rain, drought, seasons, tides, and food.

It is generally believed that the first "professional" astronomers were priests, and that their understanding of the "heavens" was seen as "divine". Ancient constructions with astronomical alienations (such as Stonehenge) probably fulfilled both astronomical and religious functions.

The study of celestial bodies also served as Navigational guides.

Astrologers studied the relative position of the Planets and stars to make predictions concerning a persons destiny.

Astronomy is not to be confused with astrology, a pseudoscience that attempts to predict a person's destiny by tracking the paths of astronomical objects. Although the two fields share a common origin, they are quite different; astronomers embrace the scientific method, while astrologers do not.

Astronomy, which etymologically means "law of the stars", (from Greek: αστρονομία = άστρον + νόμος) is a science involving the observation and explanation of events occurring outside Earth and its atmosphere. It studies the origins, evolution, physical and chemical properties of objects that can be observed in the sky (and are outside the earth), as well as the processes involving them.

Astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and monitoring of transient phenomena

In its earliest days, going back to ancient Greece and other ancient civilizations, astronomy consisted largely of astrometry, measuring positions of stars and planets in the sky

Later, the work of Kepler and Newton paved the way for celestial mechanics, mathematically predicting the motions of celestial bodies interacting under gravity, and solar system objects in particular. Much of the effort in these two areas, once done largely by hand, is highly automated nowadays, to the extent that they are rarely considered as independent disciplines anymore.

Ever since the twentieth century the field of professional astronomy has tended to split into observational astronomy and theoretical astrophysics. A. Observational astronomy is concerned mostly with getting data, which involves building and maintaining instruments and processing the resulting data; this branch is at times referred to as "astrometry" or simply as "astronomy."

B. Theoretical astrophysics is concerned mainly with figuring out the observational implications of different models, and involves working with computer or analytic models.

The fields of study are also categorized in another two ways: by "subject", usually according to the region of space (e.g. Galactic astronomy) or "problems addressed" (such as star formation or cosmology); or by the way used for obtaining information.

•Astrobiology: the study of the advent and evolution of biological systems in the universe.

•Astrometry: the study of the position of objects in the sky and their changes of position. Defines the system of coordinates used and the kinematics of objects in our galaxy.

•Cosmology: the study of the universe as a whole and its evolution.

Galactic astronomy: the study of the structure and components of our galaxy and of other galaxies

•Extragalactic astronomy: the study of objects (mainly galaxies) outside our galaxy.

Some topics include:Supernovae

Quasars Radio galaxies

Groups and clusters of galaxies

•Planetary Sciences: the study of the planets of the solar system.

Stellar astronomy: the study of the stars

Stellar evolution: the study of the evolution of stars from their formation to their end as a stellar remnant.

•Star formation: the study of the condition and processes that led to the formation of stars in the interior of gas clouds, and the process of formation itself.

Archaeoastronomy (also spelled Archeoastronomy) is, as the name implies, the combination of astronomical and archaeological studies.

Astrochemistry is the study of the chemicals found in outer space, usually in molecular gas clouds, and their formation, interaction and destruction. As such, it represents an overlap of the disciplines of astronomy and chemistry.