Greek Constellations

Greek constellations are the 48 ancient constellations listed by the Greek astronomer Claudius Ptolemy in his Almagest in the 2nd century CE. All but one of these constellations have survived to the present day and are officially recognized by the International Astronomical Union (IAU). Most of them are associated with stories from Greek mythology.

Ptolemy identified the 12 constellations of the zodiac, 21 constellations north of the zodiac, and 15 constellations to the south. The modern versions of the 48 Greek constellations are not identical to those catalogued by Ptolemy (listed below), as these constellations had changed considerably over time before the official constellation boundaries were set in the early 20th century. Additionally, the definition of the term constellation has changed since antiquity. Once, it referred to an asterism formed by a constellation’s brightest stars. Now, constellations are defined as areas of the sky – not as star patterns – with borders clearly defined by the IAU. Ptolemy, as well as many who came after him, saw constellations as asterisms and identified stars by their position within them.

Ptolemy wrote the Almagest around 150 CE. The original manuscript, written in Greek, is long lost, but Arabic and Latin translations made Ptolemy’s treatise the most influential ancient text in the field of astronomy for more than a millennium. The Almagest is the most comprehensive surviving ancient astronomical treatise, one that served as a basic guide for European and Arabic astronomers until the 17th century. Many of the traditional star names that are still in use were derived from Arabic translations of Ptolemy’s descriptions of the stars’ positions.

Ptolemy’s constellations were quite different from the modern ones. For instance, the Greek astronomer catalogued only two stars in Canis Minor, while Centaurus included the stars of Crux. The constellation Eridanus ended at Acamar because Ptolemy, who made his observations from Alexandria, Egypt, could not see Achernar. Several stars belonged to two constellations. The star we know as Elnath, Beta Tauri, marked the right ankle of Auriga, the Charioteer, as well as the northern horn of Taurus, the Bull. Fomalhaut, Alpha Piscis Austrini, marked both the mouth of the Southern Fish (Piscis Austrinus) and the end of the water flow from the urn of Aquarius, the Water Bearer. Nu Boötis marked both the top of the Herdsman’s staff and the right foot of Hercules.

Ptolemy listed a total of 1,022 individual stars in Books VII and VIII of Almagest. The stars were described by their positions in the constellations and the brightest ones were marked m = 1 (first magnitude). The stars that were not assigned to constellations were called ἀμόρφωτοι (amorphotoi), or “unformed stars.” These were stars that were not part of distinct patterns. They have since been assigned to existing constellations or used to create new ones.

The asterisms that dominate the 48 Greek constellations were known long before Ptolemy. He was merely the first (known) astronomer to catalogue them, drawing on earlier works by Greek, Egyptian, Babylonian, and Assyrian astronomers. The star patterns themselves had already been recorded by earlier observers and some of the known depictions date back to prehistoric times. For instance, a depiction of Orion constellation found in a cave in Germany is estimated to be 32,000 to 38,000 years old. Taurus has been associated with a bull since the Chalcolithic, possibly even the Upper Paleolithic. The figure we know as Auriga was mentioned in the MUL.APIN, a Babylonian compendium compiled around 1000 BCE, a full millennium before Ptolemy.

The only constellation that was given a separate status by Ptolemy is Libra. Known as Χηλαί (Chelae, meaning “the pincers”) in Ptolemy’s time, Libra was part of the neighbouring constellation Scorpius. It represented the Scorpion’s claws. The names of its bright stars Zubeneschamali, Zubenelgenubi and Zubenelhakrabi were derived from Arabic phrases meaning “the northern claw,” the southern claw,” and “the claws of the Scorpion” respectively. Even though the Romans started associating the stars of what is now Libra with scales in the first century BCE, Ptolemy continued calling the constellation Chelae. The constellation’s association with balance did not begin with the Romans. It goes back to the Babylonians, who knew the constellation as ZIB.BA.AN.NA or “the balance of heaven” about a millennium before Ptolemy.

Not all modern constellation names are exact translations of the names given by Ptolemy. Pegasus, for instance, was simply known as “the horse,” while Equuleus was “the front part of the horse.” Hercules was “the kneeling man.” Cygnus was an unspecified “bird,” while Lupus was a “wild beast.” Canis Major was simply “the dog” and Canis Minor was known as Prokyon (“before the dog”). The name is now used for its brightest star, Procyon.

Even though the constellation now known as Coma Berenices was suggested by the Greek astronomer Hipparchus in the 2nd century BCE, it was not included on Ptolemy’s list.

The only Greek constellation that is not included among the 88 modern constellations is Argo Navis (the Ship Argo). In Ptolemy’s day and for many centuries that followed, Argo Navis was the largest constellation in the sky. It occupied much of the southern sky and represented Argo, the ship on which Jason and the Argonauts sailed on their quest to find the Golden Fleece. Argo Navis was used until 1930, when the IAU defined the borders of the modern constellations and formally divided Argo into three smaller constellations: Carina, representing the ship’s keel, Puppis, marking the stern, and Vela, outlining the sails. The division is attributed to the French astronomer Nicolas Louis de Lacaille, who designated the three portions of the constellation as “Argûs in carina”, “Argûs in puppi”, and “Argûs in velis” in his star atlas of 1763.

Pyxis, a small constellation representing a mariner’s compass, introduced by Lacaille, is often taken to represent the compass of the ship, but it was not part of Argo Navis and is not a Greek constellation.

GREEK CONSTELLATIONS LIST

Below is the list the 48 Greek constellations, along with their original Greek names and numbers of stars and “unformed” stars, found outside the main constellation patterns.

Andromeda	Ἀνδρομέδα	23
Aquarius	Ὑδροχόος	42 + 3
Aquila	Ἀετός	9 + 6
Ara	Θυμιατήριον	7
Argo Navis	Ἀργώ	45
Aries	Κριός	13 + 5
Auriga	Ἡνίοχος	14
Boötes	Βοώτης	22 + 1
Cancer	Καρκίνος	9 + 4
Canis Major	Κύων	18 + 11
Canis Minor	Προκύων	2
Capricornus	Αἰγόκερως	28
Cassiopeia	Κασσιέπεια	13
Centaurus	Κένταυρος	37
Cepheus	Κηφεύς	11 + 2
Cetus	Κῆτος	22
Corona Australis	Στέφανος νότιος	13
Corona Borealis	Στέφανος	8
Corvus	Κόραξ	7
Crater	Κρατήρ	7
Cygnus	Ὄρνις	17 + 2
Delphinus	Δελφίν	10
Draco	Δράκων	31
Equuleus	Ἵππου προτομή	4
Eridanus	Ποταμός	34
Gemini	Δίδυμοι	18 + 17
Hercules	Ἐνγόνασι	28 + 1
Hydra	Ὕδρος	25 + 2
Leo	Λέων	27 + 8
Lepus	Λαγωός	12
Libra	Χηλαί	8 + 9
Lupus	Θηρίον	19
Lyra	Λύρα	10
Ophiuchus	Ὀφιοῦχοςv	24 + 5
Orion	Ὠρίων	38
Pegasus	Ἵππος	20
Perseus	Περσεύς	26 + 3
Pisces	Ἰχθύες	34 + 4
Piscis Austrinus	Ἰχθύς νότιος	11 + 6
Sagitta	Ὀιστός	5
Sagittarius	Τοξότης	31
Scorpius	Σκορπίος	21 + 3
Serpens	Ὄφιςv	18
Taurus	Ταῦρος	32 + 11
Triangulum	Τρίγωνον	4
Ursa Major	Ἄρκτος μεγάλη	27 + 8
Ursa Minor	Ἄρκτος μικρά	7 + 1
Virgo	Παρθένος	26 + 6

The data is from Ptolemy’s Almagest, via ianridpath.com.