constellation
What are constellations?
How many constellations are officially recognized?
Why are constellations important in astronomy?
Do constellations have any cultural significance?
constellation, in astronomy, originally any of certain groupings of stars that were imagined—at least by those who named them—to form conspicuous configurations of objects or creatures in the sky. The sky is divided into 88 constellations, and they are used by astronomers and navigators to designate the location of certain stars.
Constellations are not intrinsic features of the sky but are cultural constructs. Different cultures have seen the same groupings of stars as different objects. The Greeks identified Orion as a giant hunter from Greek myth. Among the Māori of New Zealand, Orion is the back of a large canoe called Te Waka o Rangi. The Lakota people of the American Great Plains see this constellation as a large creature called a Tayamni. This article concentrates on the 88 constellations used by astronomers.
Mesopotamia and ancient Greece
From the earliest times the star groups known as constellations and asterisms (patterns of stars that are not constellations, such as the Big Dipper, Orion’s Belt, or the Summer Triangle), as well as individual stars have received names connoting some natural phenomena or symbolizing religious or mythological beliefs.
It was once held that the constellation names and myths were of Greek origin. This view has now been disproved. Examination of the Greek myths associated with the stars and star groups, in the light of earlier Mesopotamian cuneiform texts, shows that in many, if not all, cases the Greeks borrowed the constellations from the Mesopotamians.
The earliest Greek work that purported to treat the constellations systematically, of which there is certain knowledge, is the Phainomena of Eudoxus of Cnidus (4th century bce). The original is lost, but a versification by the poet Aratus (3rd century bce) is extant, as is a commentary by Hipparchus (mid-2nd century bce). Analysis of the stellar positions and the rising and setting times given by Aratus and Hipparchus are consistent with those of the year 1130 bce and a latitude of 36° N (a latitude south of Greece), which supports a Mesopotamian origin for the Greek constellations.
Three hundred years after Hipparchus, the Alexandrian astronomer Ptolemy (100–170 ce) adopted a very similar scheme in his Uranometria, which appears in the seventh and eighth books of his Almagest, the catalog being styled the “accepted version.” The names and orientation of the 48 constellations therein adopted are, with a few exceptions, identical with those used at the present time.
The southern sky and constellations redefined
The majority of the remaining 40 constellations that are now accepted were added by European astronomers in the 16th through 18th centuries. The first addition was Coma Berenices, which Ptolemy regarded as part of Leo but German mathematician Caspar Vopel drew it as a separate constellation on a celestial globe he made in 1536.
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With the age of European exploration, new constellations were named in the southern sky. Dutch cartographer Petrus Plancius asked navigator Pieter Keyser to observe stars that had not been mapped on a voyage to the East Indies (now Indonesia) in 1595. Keyser recorded the positions of about 130 stars during several months in Madagascar. Keyser died in Java in 1596, but his observations came back to Plancius in 1597. For a celestial globe Plancius made in 1598, he devised 12 new southern constellations, many of which were based on animals such as Tucana (the toucan) and Volans (the flying fish). He also invented three new northern constellations: Columba, Monoceros, and Camelopardalis.
On the same voyage as Keyser was Frederick de Houtman, who also observed southern stars. Houtman was imprisoned for two years in Sumatra during a second voyage to the East Indies. When he returned to Holland in 1603, he had observed more stars than Keyser. He published a catalog of the stars in the 12 new southern constellations. Houtman also separated the Southern Cross into its own constellation, Crux. Credit for the 12 constellations is given to the trio of Plancius, Keyser, and Houtman.
In 1687 Polish astronomer Johannes Hevelius added seven constellations to the northern sky. These constellations contain faint stars and filled in gaps between more prominent constellations.
The last gaps in the southern sky were filled by French astronomer Nicolas Louis de Lacaille, who observed 10,000 stars from Table Mountain in South Africa from 1751 to 1752. Lacaille published his observations in 1754, with 14 new southern constellations. Most of them were named after scientific instruments (e.g., Microscopium, the microscope) or artistic tools (e.g., Caelum, the chisel). The sole exception was Mensa, named for Table Mountain. He also divided the large constellation Argo Navis, the ship of the Greek hero Jason, into three constellations: Carina, the keel; Puppis, the poop deck; and Vela, the sails.
- Related Topics:
- zodiac
- asterism
- lunar mansion
- Cassiopeia–Taurus Group
- decan
- On the Web:
- Live Science - Why are some constellations visible for only part of the year? (June 08, 2026)
During the 19th century there was no agreed-upon list of constellations. In 1922, the International Astronomical Union (IAU) decided on a list of 88 constellations at its first General Assembly. At the second IAU General Assembly in 1925, Belgian astronomer Eugène Delporte proposed boundaries for the constellations that would follow lines of right ascension and declination, the celestial equivalents of latitude and longitude. The final boundaries were approved in 1928 and published in 1930. The constellations were no longer regarded as patterns of stars but areas in the sky.
