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The stars that can be seen on a clear night are some figures we call "constellations", and used to help locate the position of the stars. In all there are 88 groupings of stars that appear on the celestial sphere and taking its name from religious or mythological figures, animals or objects. This term also refers to defined areas of the celestial sphere comprising groups named stars.
Drawings oldest known constellations indicate that the constellations had been established about 4000 BC The Sumerians gave the name to the constellation Aquarius, in honor of their god An, who pours the water of immortality on Earth. The Babylonians had divided the zodiac into 12 equal signs to 450 BC
The current constellations of the northern hemisphere who knew little of the Chaldeans and Egyptians differ. Homer and Hesiod mentioned the constellations and the Greek poet Aratus of Soli, gave a verse description of 44 constellations in his Phaenomena. Ptolemy, Greek astronomer and mathematician, in the Almagest, described 48 constellations, of which 47 are still know by the same name.
Many other cultures grouped stars into constellations, although not siempres correspond to those of the West. However, some Chinese constellations resemble Western, which suggests the possibility of a common origin.
In the late sixteenth century, the first European explorers of the South Seas drew maps of the southern hemisphere. The Dutch navigator Pieter Dirckz Keyser, who participated in the exploration of the East Indies in 1595 added new constellations. Later were added other southern constellations by German astronomer Johann Bayer, published the first comprehensive sky atlas hemisphere.
Many other proposed new constellations, but astronomers finally agreed on a list of 88. However, the boundaries of the constellations remained . subject of discussion until 1930, when the International Astronomical Union set these limits
to designate approximately 1,300 bright stars, the genitive of the constellation name, preceded by a Greek letter is used; This system was introduced by Johann Bayer. For example, the famous star Algol in the constellation Perseus, is called Beta Persei.
Among the best known constellations are those found in the plane of the orbit of the Earth on the background of fixed stars. Are constellations of the Zodiac. Besides these, some are well known Southern Cross, visible from the hemisferiosur, and Ursa Major, visible from the northern hemisphere. These and other constellations used to locate the position of important landmarks, such as, the celestial poles.
The largest constellation of the celestial sphere is the Hydra, which contains 68 stars visible to the naked eye. The Southern Cross, meanwhile, is the smallest constellation.
Translated from the website: http://www.astromia.com/