The night sky is one of the great treasures of Greek mythology. The Greeks, like many ancient peoples, named the constellations after the figures of their myths, and they passed on the stories of how these figures came to be placed among the stars. The 48 constellations catalogued by the Alexandrian astronomer Ptolemy in the 2nd century CE formed the basis of the modern 88 constellations recognized by the International Astronomical Union, and the stories behind them continue to shape how we think about the night sky. The twelve signs of the zodiac, the great mythical figures like Orion, Andromeda, and Perseus, and the lesser-known figures like Corvus the Crow and Ara the Altar all carry the Greek mythic imagination across the millennia.
Greek mythology is the source of the modern names of the constellations and the planets, and the standard scholarly treatment of the topic is the Star Tales of Ian Ridpath (1988). The Greek tradition, beginning with Eudoxus of Cnidus in the fourth century BCE and continuing through Aratus’ Phaenomena, codified 48 constellations that became the basis of the modern IAU list of 88; the Romans translated the Greek names into Latin (the Catasterismi of pseudo-Eratosthenes is the standard Greek source), and the Renaissance kept the Latin names as the standard astronomical terminology.
The Origins of the Greek Constellations
The constellations that we know today are largely the product of the ancient Greek imagination, but they were not invented by the Greeks alone. The Babylonians, the Egyptians, the Sumerians, and other ancient peoples also identified patterns in the night sky and named them after their gods and heroes. The Greek constellation system, however, is the one that has come down to us, and it is the one that forms the basis of the modern astronomical system.
The earliest Greek source for the constellations is Hesiod’s Works and Days (c. 700 BCE), which mentions several constellations, including the Pleiades, the Hyades, Orion, Sirius, and Arcturus. The earliest complete list of the constellations is found in the poem Phaenomena by Aratus of Soli (c. 275 BCE), a poetic adaptation of a prose work by Eudoxus of Cnidos. The Phaenomena describes 47 constellations and their mythology, and it was astronomical poems of antiquity.
The complete canonical list of 48 constellations was established by the Alexandrian astronomer Ptolemy in his Almagest (c. 150 CE). Ptolemy’s list included 12 zodiacal constellations, 21 northern constellations, and 15 southern constellations. The modern list of 88 constellations, established by the International Astronomical Union in 1922, includes the 48 Ptolemaic constellations plus 40 modern ones, mostly in the southern sky.
The Twelve Signs of the Zodiac
The twelve signs of the zodiac are the most familiar constellations of the Greek sky. They are the constellations through which the sun, moon, and planets move in their annual journeys, and they have been used for astrological purposes for thousands of years.
- Aries (the Ram): The ram with the golden fleece, sent by Hera to save Phrixus and Helle, and whose fleece was later sought by Jason and the Argonauts.
- Taurus (the Bull): The bull that carried Europa across the sea, and which was also seen as a representation of Zeus in his many bull-shaped seductions.
- Gemini (the Twins): The Dioscuri, Castor and Pollux, the twin sons of Zeus and Leda, who were famous for their skill in fighting and their devotion to each other.
- Cancer (the Crab): The crab that Hera sent to help the Hydra in its fight against Heracles, and which was placed among the stars by Hera in gratitude.
- Leo (the Lion): The Nemean Lion, the invulnerable lion that was the first of the Twelve Labors of Heracles.
- Virgo (the Maiden): Often identified with Persephone, the daughter of Demeter, or with Astraea, the goddess of justice.
- Libra (the Scales): The scales of justice, sometimes held by Astraea, and associated with the autumnal equinox, when the day and night are balanced.
- Scorpio (the Scorpion): The scorpion sent by Artemis (or by Gaia) to kill the hunter Orion.
- Sagittarius (the Archer): Often identified as Chiron, the centaur, although some traditions identify him as Crotus, the son of the god Pan and the nymph Eupheme.
- Capricornus (the Sea-Goat): The goat-fish, sometimes identified with Pan, who transformed himself into a fish to escape the monster Typhon.
- Aquarius (the Water-Bearer): Ganymede, the beautiful Trojan youth, who was abducted by Zeus to be the cupbearer of the gods.
- Pisces (the Fish): The fish into which Aphrodite and her son Eros transformed themselves to escape the monster Typhon.
The Major Mythological Constellations
Beyond the zodiac, several major constellations carry the great myths of the Greek sky.
Orion
Orion was the giant hunter of Greek myth, son of Poseidon. He was said to be the tallest and most beautiful of mortals, and he was a famous hunter. He was killed by Artemis (or, in some versions, by a scorpion sent by Gaia), and he was placed among the stars as the constellation Orion. The constellation is one of the most recognizable in the night sky, with its distinctive belt of three bright stars.
Ursa Major and Ursa Minor
The two Bears of the northern sky are associated with the myth of Callisto, a follower of Artemis who was seduced by Zeus and was transformed into a bear by Artemis or Hera. Her son Arcas, not recognizing her, was about to kill her, but Zeus intervened, transforming Arcas into a small bear and placing both of them among the stars as Ursa Major (the Great Bear) and Ursa Minor (the Little Bear). The constellations are circumpolar, never setting below the horizon in the northern hemisphere.
Perseus and Andromeda
The constellation Perseus, the hero who killed Medusa and rescued Andromeda, is in the northern sky. The constellation is named for the hero, and it contains several famous stars, including Algol, the “demon star,” which is said to represent the eye of Medusa. Adjacent to Perseus is Andromeda, the princess he rescued, who was chained to a rock as a sacrifice to a sea-monster. The constellation Andromeda is named for the princess, and the Andromeda Galaxy, the nearest large galaxy to the Milky Way, is named for the constellation.
Pegasus
Pegasus, the winged horse born from the blood of Medusa, is one of the most recognizable constellations in the northern sky. The constellation is famous for the “Square of Pegasus,” four bright stars that form a distinctive square shape. The constellation is often shown in reverse, with the horse appearing to be flying upside down.
Hercules
The constellation Hercules, the great hero, is one of the largest constellations in the northern sky, although it contains no very bright stars. The constellation is named for the hero, and it is often shown in a kneeling position, with his foot on the head of the dragon Draco, who guarded the golden apples of the Hesperides.
The Pleiades
The Pleiades, the seven daughters of Atlas and Pleione, are among the most beautiful objects in the night sky. The cluster is visible to the naked eye, and it has been a major object of myth and observation since ancient times. According to one myth, the Pleiades were the companions of Artemis, and they were placed among the stars to protect them from the hunter Orion, who pursued them across the sky.
The Planets
The planets of our solar system all bear Roman versions of Greek gods. Mercury, the swiftest planet, is named for the Roman version of Hermes, the messenger of the gods. Venus, the brightest, is named for Aphrodite. Mars, the red planet, is named for Ares, the god of war. Jupiter, the largest, is named for Zeus. Saturn is named for the Roman version of Cronus. Uranus, Neptune, and Pluto, discovered in modern times, continue the pattern.
The word “planet” itself comes from the Greek planetes, meaning “wanderer,” because the planets, unlike the fixed stars, move against the background of the constellations. The Greeks were fascinated by the planets, and they associated each with a particular god or goddess. The motion of the planets, particularly their retrograde motion, was one of the great mysteries that astronomy tried to solve.
The Milky Way
The Milky Way, the band of light that arches across the night sky, was the subject of several Greek myths. According to one tradition, the Milky Way was the milk of Hera, which spurted across the sky when she was nursing the infant Heracles. According to another, it was the road of the gods, the path they took to and from the palace of Zeus. The Greek word for the Milky Way was Galaxias, meaning “milky,” which gives us the name of our galaxy, the Galaxy, and the name of the Andromeda Galaxy.
The Cultural Legacy of the Greek Sky
The Greek constellations and the Greek sky have had an enormous impact on Western culture. The names of the constellations, the planets, and the zodiac signs are used in astronomy, astrology, navigation, and popular culture. The phrase “his stars are crossed” comes from the Greek belief that the stars influence human fate. The phrase “the writing is on the wall” comes from the Greek belief that the future could be read in the stars. The phrase “the heavens declare the glory of God” comes from a Christian reading of the same sky.
The Greek constellations have inspired countless works of literature, art, and music. The poems of Hesiod, the Phaenomena of Aratus, the Astronomica of Manilius, and many other ancient and modern works have used the constellations as a framework for thinking about human destiny. The modern science of astronomy, founded by the Greeks, has been one of the great achievements of Western civilization.
A Note on Reading This Profile
A note on reading this profile. The Greek constellations are the modern constellations, and the standard scholarly treatment is the Star Tales of Ian Ridpath (1988). The reader who wants the primary Greek sources should consult Aratus’ Phaenomena (third century BCE, the standard Greek poem on the constellations, translated by Douglas Kidd, 1997) and the Catasterismi of pseudo-Eratosthenes (probably first century BCE). The reader who wants the modern astronomical context should consult Ridpath (1988) and the IAU’s Star Names (a 2016 update of the standard work).
For more on the cultural legacy, see our guide to Greek mythology in modern culture, and our profiles of Pegasus, Orion, and Aphrodite.