Introduction to the Origins of the Constellation Names

From before recorded time, ancient people have attributed designs and objects in the stars and named them after various animals, objects, and heroes and villains of mythology.  Ancient cuneiform texts and artifacts dating back roughly 6000 years demonstrate that civilizations even then attempted to catalog the stars for religious and practical reasons.  The oldest known drawings of modern constellations are found on artifacts, vases, and games from the Sumerians, indicating that patterns in stars were a part of everyday culture as early as 4000 BC.  For example, the Fall/Winter constellation Aquarius was named by the Sumerians after their god of heaven An, who pours the waters of immortality upon the earth.  The Egyptian hieroglyph for water is the same as the symbol for Aquarius. 

By far the most thorough star catalog from ancient times belongs to Ptolemy of Alexandria, who cataloged 48 constellations during the 2nd century A.D. into a compendium translated as the Almagest.  The division of the zodiac into 12 signs was known by the Babylonians around 450 BC (and, perhaps, even as far back as a millennium before the Christian era).  Many of the northern constellations known today are little different from those known by the ancient Egyptians, Greeks, and Romans.  Homer mentioned several constellations in his writings and the Greek poet Aratus of Soli (315?-245? BC) gave a description in prose of 44 constellations in the Phaenomena.  The Greek astronomer and mathematician Claudius Ptolemy described and named 48 constellations in the Almagest (A.D. 140) of which 47 are known today by the same name with virtually the same star patterns.   Other cultures have assigned names to groups of stars, although their arrangements usually did not correspond to those of the ancients, and for a variety of reasons most of these assignments have not been internationally recognized.  

Usually, the star patterns bear little resemblance to the actual object for which they're named.  The ancient designers undoubtedly meant for them to be only symbolic representations of their favorite legend, myth, or story.  This makes identifying many of the constellations both challenging and fun.  The best way to discover the constellations is to start with a dark moonless sky and a star chart (with stars printed to only magnitude 5 or 6 -- the limit of naked-eye in a totally dark sky -- and lines identifying the constellation shape), or a planisphere.  Fortunately, the constellation patterns are usually defined by the brighter stars in the constellation.

Today, 88 constellations are officially recognized which cover the entire sky in the northern and southern hemispheres. Currently, the constellations represent 19 land animals, 14 men or women, 10 water creatures, 9 birds, two insects, two centaurs, one head of hair, a serpent, a dragon, a flying horse, a river, and 29 inanimate objects.  Don't be alarmed that the total comes to more than 88; some constellations include more than one creature.  The constellations are not actually defined by the shape they represent but, rather, a grouping of stars in delimited regions of the sky.  Of the 88 constellations only about 60 are completely visible, at one time of the year or another, from 34°N lat (where this page was written).

Since exploration of the Earth south of the equator was not undertaken systematically until the end of the 16th century, the southern sky, which was largely unknown to the ancients, was not mapped until then. New constellations were described by the Dutch navigator, Pieter Dirckz Keyser in 1595 and later added by the German astronomer Johann Bayer, who published the Uranometria (the first comprehensive star atlas published in the Western world). Others were added by Johannes Hevelius and by French astronomer Nicolas Louis de Lacaille. Despite other proposed named star groupings, astronomers settled on the current list of 88 by the end of the 1800's. The definitive boundaries of constellations were fixed by the International Astronomical Union (IAU) in 1930.