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What are constellations?


About Constellations

What are constellations?

Constellations are recognised patterns of stars forming conspicuous configurations of objects or creatures in the night sky. The word, constellation, is from the Latin word 'constellacio', meaning a set of stars and it only came into use in Middle English during the 14th century. There are 88 official constellations. These 88 patterns are essentially imagined figures or shapes with only a certain basis in the observable sky.  

Constellations are useful in tracking artificial satellites and in assisting astronomers and navigators to locate certain stars.

Origin of constellations

The earliest Greek work that set out to treat the constellations as constellations, of which there is certain knowledge, is the Phainomena of Eudoxus of Cnidus (c. 395–337 BCE). Evidence of these constellations has survived in the form of star charts, whose oldest representation appears on the statue known as the Farnese Atlas, based perhaps on the star catalogue of the Greek astronomer Hipparchus.
Before astronomers delineated precise boundaries (starting in the 19th century), constellations generally appeared as ill-defined regions of the sky. In 1603, Johann Bayer introduced the now standard nomenclature for brighter stars, the 'Uranometria'. The Uranometria was literally used by astronomers throughout the 17th and the 18th century as a standard reference tool.
'Uranometria' contained 51 star charts, engraved on copper plates by Alexander Mair (ca 1562-1617). The first 48 charts illustrate each of the 48 Ptolemaic constellations. The 49th chart introduces 12 new constellations in the deep southern sky which were unknown to Ptolemy. The final two charts are planispheres labeled "Overview of the northern hemisphere" and "Overview of the southern hemisphere." The majority of the remaining 40 constellations that are now accepted were added by European astronomers in the 17th and 18th centuries. In the 20th century the delineation of precise boundaries for all the 88 constellations was undertaken by a committee of the International Astronomical Union or IUA. By 1930 it was possible to assign any star to a constellation.

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