Monday, November 21, 2016

What is a Constellation?

Modern astronomers divide the sky into eighty-eight constellations with defined boundaries.

A constellation is a cluster of stars that resemble a recognizable creature such as a crab (Cancer) or a lion (Leo). Some are named for mythological figures such as Andromeda, the daughter of Cassiopeia and Cepheus in Greek mythology.

Some constellations are named for mythological creatures such as Phoenix, the mythical firebird (shown above). It is a southern constellation. Draco, the Dragon constellation, is a northern constellation. Draco was the North Pole Star 5000 years ago. The Orontes River in Turkey was called "Draco" because it is one of the few rivers on Earth with a current that flows north.

Here are images of the constellations Aries and Taurus.

Aries is the Ram constellation

Taurus is the Bull constellation

The names and number of the constellations have changed throughout history. In the ancient world, sages (wise men) spoke of 50 constellations. This was the perspective of Ptolemy whose book Almagest was published in 150 AD. Since then astronomers have added 38 constellations, mostly visible in the southern skies.

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