Constellations

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The constellations are the named star patterns into which the sky is divided. Eighty-eight are recognised in modern astronomy, with boundaries fixed by the International Astronomical Union in the 1920s; the classical set of forty-eight comes from Ptolemy's Almagest, inherited from Babylonian and Greek sources. They are not the same as the zodiac signs, which are equal thirty-degree divisions that no longer line up with the constellations they are named for.

Facts

Overview

Entries in the Atlas: 59
What Defines This Grouping: Star patterns and the sky regions that now carry their names. Distinct from the twelve zodiac signs, which borrowed constellation names but are equal thirty-degree arcs of the ecliptic and no longer coincide with them. 1
Size of the Traditional Set: 88 constellations 2

Origins

Place of Origin: Mesopotamian star lore, transmitted through Greek astronomy; the southern-sky figures were added by European observers from the late sixteenth century 3
Whose Classification This Is: The International Astronomical Union: 88 constellations agreed in 1922, with boundaries drawn by Eugène Delporte, adopted in 1928 and published in 1930. 2

Structure

Structure: Eighty-eight regions covering the whole celestial sphere without gap or overlap, bounded along lines of right ascension and declination for the epoch B1875.0. 2

Sources

A History of Western Astrology Nicholas Campion, 2009
Delimitation Scientifique des Constellations Eugene Delporte, 1930
The Heavenly Writing: Divination, Horoscopy, and Astronomy in Mesopotamian Culture Francesca Rochberg, 2004

Learn More

The Star Patterns of the Sky

The constellations are the named patterns into which the stars are grouped. Modern astronomy recognises eighty-eight, with boundaries fixed by the International Astronomical Union in the 1920s, dividing the whole sky between them; the classical set of forty-eight comes from Ptolemy's Almagest, and other cultures divided the sky in their own ways.

Each constellation carries a name and, usually, a myth explaining the figure it depicts, Orion the hunter, the Great Bear, the hero Perseus and the monster Cetus. The twelve zodiacal constellations are those the Sun's path crosses, and are the source of the names of the astrological signs, though signs and constellations no longer coincide.

Myth, sky and sign

The constellations belong to astronomy and to the mythologies that named them, and this category treats them as star patterns and as bearers of myth, distinct from the astrological signs that borrowed their names. Many cultures (Chinese, Indian, Mesopotamian, Polynesian and others), mapped the sky differently, and the Western forty-eight are one scheme among several.

The atlas gives each constellation its figure, its principal stars, and the myth or lore attached to it. The individual named stars within them are treated in the star category, and the zodiacal signs, which share their names, under the sign category.