In contemporary astronomy, the sky is divided into 88 regions called constellations, generally based on the asterisms (which are also called “constellations”) of Greek and Roman mythology. The number of 88, along with the contemporary scientific notion of “constellation”, was convention in 1922 by the International Astronomical Union in order to establish a universal pattern for professional astronomers, who defined constellations from then on as regions of the sky separated by arcs of right ascensions and declinations and grouped by asterisms of their historically most important stars, which cover the entire celestial sphere. The constellations along the ecliptic are called the zodiac.

The ancient Sumerians, and later the Greeks (as recorded by Ptolemy), established most of the northern constellations in international use today. When explorers mapped the stars of the southern skies, European and American astronomers proposed new constellations for that region, as well as ones to fill gaps between the traditional constellations. Not all of these proposals caught on, but in 1922, the International Astronomical Union (IAU) adopted the modern list of 88 constellations. After this, Eugène Joseph Delporte drew up precise boundaries for each constellation, so that every point in the sky belonged to exactly one constellation.

History

Constellation

Some constellations are no longer recognized by the International Astronomical Union but may appear in older star charts and other references. Most notable is Argo Navis, which was one of Ptolemy’s original 48 constellations.
a constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices. The 88 modern constellations are defined regions of the sky together covering the entire celestial sphere.

Origins for the earliest constellations likely goes back to prehistory, whose now unknown creators collectively used them to relate important stories of either their beliefs, experiences, creation or mythology. As such, different cultures and countries often adopted their own set of constellations outlines, some that persisted into the early 20th century. Adoption of numerous constellations has significantly changed throughout the centuries. Many have varied in size or shape, while some became popular then dropped into obscurity. Others were traditionally used only by various cultures or single nations.

The traditional Western constellations are the 48 Greek classical patterns, as stated in both Aratus’ work Phenomena or Ptolemy’s Almagest, though their existence probably predates these constellation names by several centuries. Newer constellations in the far Southern Sky were added much later since the 15th century until the mid-18th century when European explorers began traveling to the Southern Hemisphere. Twelve important constellations are assigned to the zodiac (where the Sun, Moon, and planets all lie), which straddles the ecliptic. The origins of the zodiac probably date back into prehistory, whose astrological divisions became prominent c. 400 BC within Babylonian or Chaldean astronomy.

In 1928, the International Astronomical Union (IAU) ratified and recognized 88 modern constellations, with contiguous boundaries defined by right ascension and declination. Therefore, any given point in a celestial coordinate system lies in one of the modern constellations. Some astronomical naming systems give the constellation where a given celestial object is found along with a designation in order to convey an approximate idea of its location in the sky. e.g. The Flamsteed designation for bright stars consists of a number and the genitive form of the constellation name.

Former constellations

Former constellations are old historical Western constellations that for various reasons are no longer recognized or adopted as official constellations by the International Astronomical Union (IAU). Prior to 1930, many of these defunct constellations were traditionally identified by one or more countries or cultures. Some only lasted several decades but others continued over many centuries. All are now only recognized for having classical or historical value. Many former constellations have had complex Latinised names assigned as objects, people, or as mythological or zoological creatures. Others with unwieldy names were foreshortened for the sake of practical convenience. e.g. Scutum Sobiescianum reduced to Scutum, Mons Mensae to Mensa or Apparatus Sculptoris to Sculptor.

Some of the northern sky’s former constellations were often placed in the less populated stellar regions between the traditional brighter constellations just to fill any unassigned gaps. In the southern skies, new constellations were often created from about the 15th Century by voyagers who began journeying south of the equator. European countries like England, France, the Netherlands, German or Italian states, etc., often supported and popularised their constellation outlines. In some cases, differing constellations occupied areas using the same shared stars. Most of these former constellations can often be found mentioned in older books, star charts or star catalogs.

Standardisation of all the modern eighty-eight constellations names and boundaries was finally made by Eugene Delporte for the IAU in 1930, under a ratified international agreement, successfully removing any possible astronomical ambiguities between the nations. Nearly all former or defunct constellations mostly differ in their designated boundaries inasmuch as they have outlines that do not follow the exacting defined lines of right ascension and declination.

Modern Constellations

The 88 constellations depict 42 animals, 29 inanimate objects and 17 humans or mythological characters.

Abbreviations

Each of the IAU constellations has an official 3 letter abbreviation. They are actually abbreviations of the genitive form of the constellation names, so some letters appearing in the abbreviation may come from the genitive form without appearing in the base name (as in Sge for Sagitta/Sagittae, to avoid confusion with Sagittarius, abbreviated Sgr).

The majority of the abbreviations are just the first three letters of the constellation, with the first character capitalised: Ori for Orion, Ara for Ara/Arae, Com for Coma Berenices. In cases where this would not unambiguously identify the constellation, or where the name and its genitive differ in the first three letters, other letters beyond the initial three are used: Aps for Apus/Apodis, CrA for Corona Australis, CrB for Corona Borealis, Crv for Corvus. (Crater is abbreviated Crt to prevent confusion with CrA.)

When letters are taken from the second word of a two-word name, the first letter from the second word is capitalised: CMa for Canis Major, CMi for Canis Minor.

The abbreviations are unambiguous, with two exceptions. Leo for the constellation Leo could be mistaken for Leo Minor (abbreviated LMi), and Tri for Triangulum could be mistaken for Triangulum Australe (abbreviated TrA).

List

For help with the literary English pronunciations, see the pronunciation key. There is considerable diversity in how Latinate names are pronounced in English. For traditions closer to the original, see Latin spelling and pronunciation.

Constellation Origin Meaning Brightest star
Andromeda ancient (Ptolemy) Andromeda (The chained maiden or princess) Alpheratz
Antlia 1763, Lacaille air pump α Antliae
Apus  1603, Uranometria, created by Keyser and de Houtman Bird-of-paradise/Exotic Bird/Extraordinary Bird α Apodis
Aquarius  ancient (Ptolemy) water-bearer Sadalsuud
Aquila  ancient (Ptolemy) eagle Altair
Ara ancient (Ptolemy) altar β Arae
Aries ancient (Ptolemy) ram Hamal
Auriga  ancient (Ptolemy) charioteer Capella
Boötes  ancient (Ptolemy) herdsman Arcturus
Caelum 1763, Lacaille chisel or graving tool α Caeli
Camelopardalis  1613, Plancius[7] giraffe β Camelopardalis
Cancer  ancient (Ptolemy) crab Tarf[8]
Canes Venatici  1690, Firmamentum Sobiescianum, Hevelius hunting dogs Cor Caroli
Canis Major  ancient (Ptolemy) greater dog Sirius
Canis Minor  ancient (Ptolemy) lesser dog Procyon
Capricornus  ancient (Ptolemy) sea goat Deneb Algedi
Carina  1763, Lacaille, split from Argo Navis keel Canopus
Cassiopeia  ancient (Ptolemy) Cassiopeia (mythological character) Schedar[8]
Centaurus  ancient (Ptolemy) centaur Rigil Kentaurus[8]
Cepheus  ancient (Ptolemy) Cepheus (mythological character) Alderamin
Cetus ancient (Ptolemy) sea monster (later interpreted as a whale) Diphda[8]
Chamaeleon  1603, Uranometria, created by Keyser and de Houtman chameleon α Chamaeleontis
Circinus  1763, Lacaille compasses α Circini
Columba 1592, Plancius, split from Canis Major dove Phact
Coma Berenices  1603, Uranometria, split from Leo Berenice’s hair β Comae Berenices
Corona Australis[9] ancient (Ptolemy) southern crown Meridiana[8]
Corona Borealis  ancient (Ptolemy) northern crown Alphecca
Corvus  ancient (Ptolemy) crow Gienah
Crater  ancient (Ptolemy) cup δ Crateris
Crux  1603, Uranometria, split from Centaurus southern cross Acrux
Cygnus  ancient (Ptolemy) swan or Northern Cross Deneb
Delphinus  ancient (Ptolemy) dolphin Rotanev
Dorado  1603, Uranometria, created by Keyser and de Houtman dolphinfish α Doradus
Draco  ancient (Ptolemy) dragon Eltanin[8]
Equuleus  ancient (Ptolemy) pony Kitalpha
Eridanus ancient (Ptolemy) river Eridanus (mythology) Achernar
Fornax 1763, Lacaille chemical furnace Dalim[8]
Gemini  ancient (Ptolemy) twins Pollux
Grus  1603, Uranometria, created by Keyser and de Houtman Crane Alnair
Hercules  ancient (Ptolemy) Hercules (mythological character) Kornephoros
Horologium 1763, Lacaille pendulum clock α Horologii
Hydra  ancient (Ptolemy) Hydra (mythological creature) Alphard
Hydrus 1603, Uranometria, created by Keyser and de Houtman lesser water snake β Hydri
Indus  1603, Uranometria, created by Keyser and de Houtman Indian (of unspecified type) α Indi
Lacerta 1690, Firmamentum Sobiescianum, Hevelius lizard α Lacertae
Leo ancient (Ptolemy) lion Regulus
Leo Minor 1690, Firmamentum Sobiescianum, Hevelius lesser lion Praecipua
Lepus  ancient (Ptolemy) hare Arneb
Libra  ancient (Ptolemy) balance Zubeneschamali[8]
Lupus  ancient (Ptolemy) wolf α Lupi
Lynx  1690, Firmamentum Sobiescianum, Hevelius lynx α Lyncis
Lyra  ancient (Ptolemy) lyre / harp Vega
Mensa 1763, Lacaille Table Mountain (South Africa) α Mensae
Microscopium 1763, Lacaille microscope γ Microscopii
Monoceros 1613, Plancius unicorn β Monocerotis
Musca 1603, Uranometria, created by Keyser and de Houtman fly α Muscae
Norma  1763, Lacaille carpenter’s level γ2 Normae
Octans 1763, Lacaille octant (instrument) ν Octantis
Ophiuchus  ancient (Ptolemy) serpent-bearer Rasalhague
Orion  ancient (Ptolemy) Orion (mythological character) Rigel
Pavo  1603, Uranometria, created by Keyser and de Houtman peacock Peacock
Pegasus ancient (Ptolemy) Pegasus (mythological winged horse) Enif
Perseus  ancient (Ptolemy) Perseus (mythological character) Mirfak
Phoenix 1603, Uranometria, created by Keyser and de Houtman phoenix Ankaa
Pictor  1763, Lacaille easel α Pictoris
Pisces ancient (Ptolemy) fishes Alpherg
Piscis Austrinus  ancient (Ptolemy) southern fish Fomalhaut
Puppis 1763, Lacaille, split from Argo Navis poop deck Naos
Pyxis  1763, Lacaille mariner’s compass α Pyxidis
Reticulum  1763, Lacaille eyepiece graticule α Reticuli
Sagitta ancient (Ptolemy) arrow γ Sagittae
Sagittarius ancient (Ptolemy) archer Kaus Australis
Scorpius ancient (Ptolemy) scorpion Antares
Sculptor 1763, Lacaille sculptor α Sculptoris
Scutum 1690, Firmamentum Sobiescianum, Hevelius shield (of Sobieski) α Scuti
Serpens[11] ancient (Ptolemy) snake Unukalhai
Sextans  1690, Firmamentum Sobiescianum, Hevelius sextant α Sextantis
Taurus  ancient (Ptolemy) bull Aldebaran
Telescopium  1763, Lacaille telescope α Telescopii
Triangulum ancient (Ptolemy) triangle β Trianguli
Triangulum Australe 1603 Uranometria, created by Keyser and de Houtman southern triangle Atria
Tucana  1603 Uranometria, created by Keyser and de Houtman toucan α Tucanae
Ursa Major  ancient (Ptolemy) great bear Alioth
Ursa Minor  ancient (Ptolemy) lesser bear Polaris
Vela  1763, Lacaille, split from Argo Navis sails γ2 Velorum
Virgo  ancient (Ptolemy) virgin or maiden Spica
Volans 1603, Uranometria, created by Keyser and de Houtman flying fish β Volantis
Vulpecula 1690, Firmamentum Sobiescianum, Hevelius fox Anser

Asterisms

Various other unofficial patterns exist alongside the constellations. These are known as “asterisms”. Examples include the Big Dipper/Plough and the Northern Cross. Some ancient asterisms, for example, Coma Berenices, Serpens, and portions of Argo Navis are now officially constellations.

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