Constellations from Greek Myths

When you look up at the night sky, you are looking at a ceiling painted by ancient Greek storytellers. The majority of the 88 officially recognized constellations carry names and myths drawn from Greek mythology, and many of the most recognizable star patterns are the direct legacy of the ancient tradition of katasterismos: the transformation of mythological figures into stars as a form of divine commemoration or punishment.

For the ancient Greeks, the sky was a living mythological text. Constellations were not abstract geometric patterns but the literal forms of gods, heroes, monsters, and creatures who had earned their place among the stars. Navigators used them to cross the Mediterranean; farmers used them to time their planting and harvesting; poets wove them into epic narratives. The Greek astronomical tradition, codified by Eratosthenes and Ptolemy, was absorbed by the Romans and later by Arab astronomers, eventually becoming the foundation of the modern astronomical naming system still in use today.

Orion is one of the most recognizable constellations in the sky, his three-star belt visible from virtually every point on Earth, and one of the richest in mythological backstory. In Greek myth, Orion was a giant hunter of extraordinary skill, variously described as the son of Poseidon or born from a bull hide buried by the gods.

Several myths explain how Orion came to be placed in the sky. In the most poignant version, Orion was the companion and perhaps lover of Artemis, the goddess of the hunt. Her twin brother Apollo, disapproving of the relationship, tricked Artemis into shooting Orion herself, pointing out a distant figure swimming in the sea and challenging her famous accuracy. She loosed her arrow and killed the one person she had loved. In grief, she placed him among the stars.

In another tradition, Orion boasted that he would hunt every animal on Earth, which angered Gaia (the Earth). She sent a giant scorpion to kill him, and Zeus placed both Orion and the Scorpion (the constellation Scorpius) in the sky, but on opposite sides so they would never meet again. This is why Scorpius rises in the east just as Orion sets in the west; they eternally pursue and flee each other across the heavens.

The stars of Orion's constellation include the red supergiant Betelgeuse (his shoulder) and the blue supergiant Rigel (his foot), two of the brightest stars in the night sky, their contrasting colors a beautiful accident of stellar physics now framed by two and a half millennia of mythological meaning.

One of the most dramatic mythological narrative sequences is preserved in a connected family of constellations: Perseus, Andromeda, Cassiopeia, Cepheus, and Cetus (the sea monster) together tell the complete story of Perseus's rescue of Andromeda.

The story begins with Cassiopeia, the vain queen of Ethiopia who boasted that her daughter Andromeda was more beautiful than the Nereids, sea nymphs beloved by Poseidon. Enraged, Poseidon sent the sea monster Cetus to ravage the coast. The oracle declared that Andromeda must be sacrificed to the beast to appease the gods. Her father Cepheus, the king, had her chained to a rock at the water's edge.

Perseus, returning from his quest to slay Medusa with her severed head in his bag, spotted Andromeda chained to the cliff. He slew Cetus, freed Andromeda, and married her. The gods commemorated all the principals by placing them in the sky: the boastful Cassiopeia was set in a position that makes her constellation appear to tumble upside down across the pole, a perpetual reminder of her pride. Perseus is depicted holding Medusa's severed head, with the star Algol (from the Arabic for "the demon's head," itself derived from the Greek myth) marking the Gorgon's eye and blinking variably, once interpreted as the terrifying winking of Medusa's deadly gaze.

Ursa Major (the Great Bear) and Ursa Minor (the Little Bear) are among the most important constellations for navigation, the North Star, Polaris, sits at the tip of Ursa Minor's tail, and their mythological origin is one of Greek mythology's most affecting stories of divine jealousy.

Callisto was a beautiful nymph and companion of Artemis, sworn to chastity. Zeus, overcome with desire, disguised himself, in some versions as Artemis herself, and assaulted Callisto. When she became pregnant, Artemis discovered the violation of her companion's vow and expelled her from the hunt. Hera, furious with jealousy, transformed Callisto into a bear.

Years later, Callisto in her bear form encountered her grown son Arcas, who did not recognize her and was about to kill her. Zeus intervened, transforming Arcas into a bear as well, and placed both mother and son in the sky as Ursa Major and Ursa Minor. Hera, still bitter, persuaded the gods of the sea never to allow the bears to rest beneath the ocean's horizon, which is why in northern latitudes, Ursa Major and Ursa Minor are circumpolar constellations, circling the pole star without ever setting.

The seven brightest stars of Ursa Major form the famous Big Dipper (or Plough) asterism, one of the most universally recognized star patterns across cultures and the primary means by which navigators locate the North Star.

The twelve constellations of the zodiac, through which the Sun appears to pass over the course of a year, are predominantly drawn from Greek mythology. Their origins as a coherent system are largely Babylonian, but the Greeks added mythological narratives that the later Western tradition has perpetuated.

Gemini (the Twins) represents the divine twins Castor and Pollux (Polydeuces), the Dioscuri, one mortal, one immortal, who were so devoted to each other that when Castor died, Pollux asked Zeus to share his immortality with his brother. They now alternate between Olympus and Hades, spending alternate days in each realm. Taurus (the Bull) commemorates Zeus's transformation into a white bull to abduct Europa, or sometimes the Cretan Bull of Heracles' labors. Scorpius is the scorpion sent by Gaia to kill Orion.

Leo (the Lion) represents the Nemean Lion, whose impenetrable hide made it invulnerable to weapons until Heracles strangled it bare-handed as his First Labor. Aquarius (the Water-Bearer) is associated with Ganymede, the beautiful Trojan youth whom Zeus carried to Olympus in the form of an eagle to serve as cupbearer to the gods. Virgo is most often associated with Demeter or her daughter Persephone, whose annual descent into the underworld explains the seasons.

The hero Heracles lends his name directly to a constellation, though it is not one of the most prominent. But his most famous indirect astronomical legacy is the Milky Way itself. According to myth, Zeus laid the infant Heracles against the sleeping Hera's breast so that he might drink divine milk and gain immortality. When Hera woke and pulled away, milk sprayed across the sky, creating the band of stars the Greeks called the galaxias kuklos (milky circle), from which we derive both the words "galaxy" and "Milky Way."

Pegasus, the winged horse born from Medusa's blood, rides through the northern sky. The Great Square of Pegasus is one of autumn's most recognizable star patterns. The constellation Aquila (the Eagle) represents the eagle of Zeus, either the bird that carried Ganymede to Olympus or the one that daily devoured the liver of Prometheus as punishment for stealing fire.

Cygnus (the Swan) has several mythological associations: it may represent Zeus in his swan form when he appeared to Leda (a union that produced Helen of Troy and the divine twins Castor and Pollux), or it may represent Orpheus, transformed into a swan after his death and placed near his lyre (the constellation Lyra) in the sky. The brightest star of Cygnus, Deneb, is one of the most luminous stars visible to the naked eye.

Not all mythological astronomical figures became formal constellations, some are star clusters whose stories are no less rich. The Pleiades, the famous open cluster in Taurus visible to the naked eye as a tight grouping of six or seven stars (ancient eyes could often make out all seven), are the seven daughters of Atlas and the oceanid Pleione.

Their placement in the sky has several mythological explanations. In one version, Zeus transformed them into stars to save them from the eternal pursuit of Orion, who had fallen in love with their mother. In another, they were placed there after Atlas was condemned to bear the sky on his shoulders, so they might accompany their father in his endless labor. One of the seven Pleiades, Merope, is said to shine less brightly than her sisters because she alone married a mortal (Sisyphus) rather than a god, and hides her face in shame.

The rising of the Pleiades in spring marked the beginning of the Mediterranean sailing season for ancient Greeks; their setting in autumn marked its end. They were equally important as agricultural markers, Hesiod instructed farmers in his Works and Days to time plowing, harvesting, and pruning by the Pleiades' position in the sky. Their mythological story and their practical astronomical function were inseparable in ancient Greek life.

The International Astronomical Union (IAU) officially recognizes 88 constellations, of which the great majority carry names derived from the Greco-Roman tradition. When the IAU formalized the constellation boundaries in 1930, it codified a naming system that stretched back to the star catalogues of Hipparchus (2nd century BCE) and Ptolemy's Almagest (2nd century CE), which listed 48 constellations, nearly all with Greek mythological origins.

The Arabic astronomical tradition, which preserved and extended Greek astronomy during Europe's medieval period, contributed the names of many individual stars within those constellations: Betelgeuse, Rigel, Aldebaran, Altair, Deneb, Fomalhaut. These Arabic names are typically translations or adaptations of Greek descriptions of the stars' positions within their mythological figure, "Betelgeuse" deriving from an Arabic phrase meaning roughly "the armpit of the giant."

Today, spacecraft and space missions carry mythological names that continue the tradition: the Apollo lunar program, the Mercury and Gemini missions, the Artemis program returning humans to the Moon, the Cassini probe to Saturn, the Juno probe to Jupiter. In naming our greatest exploratory achievements after Greek and Roman gods, modern civilization acknowledges that the imagination that first populated the night sky with stories is the same imagination driving us toward the stars themselves.