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AstronomyAstronomy is a natural science that deals with the study of celestial objects (such as moons, planets, stars, nebulae, and galaxies); the physics, chemistry, and evolution of such objects; and phenomena that originate outside the atmosphere of Earth (such as supernovae, gamma ray bursts, and cosmic background radiation).


A related but distinct subject, cosmology, is concerned with studying the universe as a whole.

Astronomy is one of the oldest sciences. Prehistoric cultures left behind astronomical artifacts such as the Egyptian monuments and Nubian monuments, and early civilizations such as the Babylonians, Greeks, Chinese, Indians, Iranians and Maya performed methodical observations of the night sky. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars, but professional astronomy is nowadays often considered to be synonymous with astrophysics.

During the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of celestial objects, which is then analyzed using basic principles of physics. Theoretical astronomy is oriented towards the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the observational results, and observations being used to confirm theoretical results.

Amateur astronomers have contributed to 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.

Astronomy is not to be confused with astrology, the belief system which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin they are now entirely distinct.

The word astronomy (from the Greek words astron, "star" and -nomy from nomos, "law" or "culture") literally means "law of the stars" (or "culture of the stars" depending on the translation).

Generally, either the term "astronomy" or "astrophysics" may be used to refer to this subject. Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties" and "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, and dynamic processes of celestial objects and phenomena". In some cases, as in the introduction of the introductory textbook The Physical Universe by Frank Shu, "astronomy" may be used to describe the qualitative study of the subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject. However, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Few fields, such as astrometry, are purely astronomy rather than also astrophysics. Various departments in which scientists carry out research on this subject may use "astronomy" and "astrophysics," partly depending on whether the department is historically affiliated with a physics department, and many professional astronomers have physics rather than astronomy degrees. One of the leading scientific journals in the field is the European journal named Astronomy and Astrophysics. The leading American journals are The Astrophysical Journal and The Astronomical Journal.

Free Astronomy Screensaver
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Astronomy Screensaver
Planets Screensaver
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Nebulae Screensaver
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Supernovae Screensaver
Gamma Ray Burst Screensaver
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Free Astronomy Screen saver
Free Planets Screen saver
Free Stars Screen saver
Free Nebulae Screen saver
Free Galaxies Screen saver
Free Supernovae Screen saver
Free Gamma Ray Burst Screen saver
Free Cosmic Background Radiation Screen saver
Astronomy Screen saver
Planets Screen saver
Stars Screen saver
Nebulae Screen saver
Galaxies Screen saver
Supernovae Screen saver
Gamma Ray Burst Screen saver
Cosmic Background Radiation Screen saver


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