Constellation

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For other uses, see a collection of Stars.

A constellation is any one of the 88 areas into which the sky - or the celestial sphere - is divided. The term is also often used less formally to denote a group of stars visibly related to each other in a particular configuration or pattern.

Some well-known constellations contain striking and familiar patterns of bright stars. Examples are Ursa Major (containing the Big Dipper), Orion (containing a figure of a hunter), Leo (containing bright stars outlining the form of a lion) and Scorpius (a scorpion). Other constellations do not encompass any discernible star patterns, and contain only faint stars.

Explanation

The International Astronomical Union (IAU) divides the sky into 88 official constellations with precise boundaries, so that every direction or place in the sky belongs within one constellation. In the northern celestial hemisphere, these are mostly based upon the constellations of the ancient Greek tradition, passed down through the Middle Ages, and contains the signs of the zodiac.

The constellation boundaries were drawn up by Eugène Delporte in 1930, and he drew them along vertical and horizontal lines of right ascension and declination. However, he did so for the epoch B1875.0, which means that due to precession of the equinoxes, the borders on a modern star map (eg, for epoch J2000) are already somewhat skewed and no longer perfectly vertical or horizontal. This skew will increase over the years and centuries to come.

In three-dimensional space, most of the stars we see have little or no relation to one another, but can appear to be grouped on the celestial sphere of the night sky. Humans excel at finding patterns and throughout history have grouped together stars that appear close to one another.

A star pattern may be widely known but may not be recognized by the International Astronomical Union; such a pattern of stars is called an asterism. An example is the grouping called the Big Dipper (North America) or the Plough (UK).

The stars in a constellation or asterism rarely have any astrophysical relationship to each other; they just happen to appear close together in the sky as viewed from Earth and typically lie many light years apart in space. However, one exception to this is the Ursa Major moving group.

The grouping of stars into constellations is essentially arbitrary, and different cultures have had different constellations, although a few of the more obvious ones tend to recur frequently, e.g., Orion and Scorpius.

History of the constellationsMain article: Former constellations

Our current list is based on those listed by the Roman astronomer, Claudius Ptolemy, who lived in Alexandria, Egypt.

In more recent times this list has been added to in order to fill gaps between Ptolemy's patterns. The Greeks considered the sky as including both constellations and dim spaces between. But Renaissance star catalogs by Johann Bayer and John Flamsteed required every star to be in a constellation, and the number of visible stars in a constellation to be manageably small.

Twelve of the constellations in the southern celestial hemisphere were not observable by the Greeks, and were created by Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman in the sixteenth century and first cataloged by Johann Bayer.

Other proposed constellations didn't make the cut, most notably Quadrans Muralis (now part of Boötes) for which the Quadrantid meteors are named. Also the ancient constellation Argo Navis was so big that it was broken up into several different constellations, for the convenience of stellar cartographers.

Constellations in variant culturesMain article: Chinese constellation

Chinese constellations are different from the western constellations, due to the independent development of ancient Chinese astronomy. Ancient Chinese skywatchers divided their night sky in a different way, but there are also similarities. The Chinese counterpart of the 12 western zodiac constellations are the 28 "Xiu" (宿) or "mansions" (a literal translation).

Star names

All modern constellation names are Latin proper names or words, and some stars are named using the genitive of the constellation in which they are found. The genitive is formed using the usual rules of Latin grammar, and for those unfamiliar with that language the form of the genitive is sometimes unpredictable and must be memorized. Some examples include: Aries → Arietis; Taurus → Tauri; Gemini → Geminorum; Virgo → Virginis; Libra → Librae; Pisces → Piscium; Lepus → Leporis.

These names include Bayer designations such as Alpha Centauri, Flamsteed designations such as 61 Cygni, and variable star designations such as RR Lyrae. However, many fainter stars will just be given a catalog number designation (in each of various star catalogs) that does not incorporate the constellation name.

For more information about star names, see Star designations and the list of stars by constellation.

See also List of constellations List of constellations by area Former constellations Chinese constellation Nakshatra

Astronomy | Constellations of the Zodiac | Astrology

Aries ( ) | Taurus ( ) | Gemini ( ) | Cancer ( ) | Leo ( ) | Virgo ( ) | Libra ( ) |

Scorpius/Scorpio ( ) | Ophiuchus | Sagittarius ( ) | Capricornus/Capricorn ( ) | Aquarius ( ) |

Pisces ( )

The 48 Constellations listed by Ptolemy

Andromeda • Aquarius • Aquila • Ara • Argo Navis • Aries • Auriga • Boötes • Cancer • Canis   Major  • Canis   Minor  • Capricornus • Cassiopeia • Centaurus • Cepheus • Cetus • Corona   Australis  • Corona   Borealis  • Corvus • Crater • Cygnus • Delphinus • Draco •

Equuleus • Eridanus • Gemini • Hercules • Hydra • Leo • Lepus • Libra • Lupus • Lyra • Ophiuchus • Orion • Pegasus • Perseus • Pisces • Piscis   Austrinus  • Sagitta • Sagittarius •

Scorpius • Serpens • Taurus • Triangulum • Ursa   Major  • Ursa   Minor  • Virgo

The 12 Constellations created by Pieter Dirkszoon Keyser and Frederick de Houtman between 1595 and 1597 and introduced by Johann Bayer in the 1603 text Uranometria

Apus | Chamaeleon | Dorado | Grus | Hydrus | Indus | Musca | Pavo | Phoenix | Triangulum Australe | Tucana | Volans

Constellations changed by Johann Bayer in the 1603 text Uranometria

Centaurus | split into | Centaurus | Crux

Leo | split into | Leo | Coma   Berenices

Piscis   Austrinus | split into | Piscis   Austrinus | Grus

Sagittarius | split into | Sagittarius | Corona   Australis

Constellations introduced by Jakob Bartsch in his 1624 text Usus Astronomicus Planisphaerii Stellati

Camelopardalis | Monoceros

Constellations changed by Augustin Royer in 1679

Canis Major | split into | Columba | Canis Major

Constellations introduced by Johannes Hevelius in the 1690 text Firmamentum Sobiescianum

Canes   Venatici | Lacerta | Leo   Minor | Lynx | Scutum | Sextans | Vulpecula

Obsolete Constellations introduced by Johannes Hevelius in the 1690 text Firmamentum Sobiescianum

Cerberus | Mons Maenalus | Triangulum Minor

Constellations changed by Lacaille in 1763

Argo Navis split into Carina | Puppis | Vela

Eridanus split into Eridanus | Fornax

Sagittarius | Corona   Australis altered to create Telescopium

Centaurus | Lupus altered to create Circinus

The 14 Constellations introduced by Lacaille in 1763

Antlia | Caelum | Circinus | Fornax | Horologium | Mensa | Microscopium | Norma | Octans | Pictor | Pyxis | Reticulum | Sculptor | Telescopium

Former Constellations

Antinous | Apis | Argo Navis | CerberusCustos Messium | Felis | Frederici Honores | Gallus

Globus Aerostaticus | Jordanus | Lochium FunisMachina Electrica | Malus | Mons Maenalus | Musca Borealis

Noctua | Officina Typographica | PhoenicopterusPolophylax | Psalterium Georgii | Quadrans Muralis

Ramus Pomifer | Robur Carolinum | Sceptrum BrandenburgicumSceptrum et Manus Iustitiae | Solarium | Tarandus vel Rangifer

Taurus Poniatovii | Telescopium Herschelii | TestudoTigris | Triangulum Minor | Turdus Solitarius | Vespa

The 88 modern Constellations

Andromeda • Antlia • Apus • Aquarius • Aquila • Ara • Aries • Auriga • Boötes • Caelum • Camelopardalis • Cancer • Canes   Venatici  • Canis   Major  • Canis   Minor  • Capricornus • Carina • Cassiopeia • Centaurus • Cepheus • Cetus • Chamaeleon • Circinus • Columba •

Coma   Berenices  • Corona   Australis  • Corona   Borealis  • Corvus • Crater • Crux • Cygnus • Delphinus • Dorado • Draco • Equuleus • Eridanus • Fornax • Gemini • Grus • Hercules •

Horologium • Hydra • Hydrus • Indus • Lacerta • Leo • Leo   Minor  • Lepus • Libra • Lupus • Lynx • Lyra • Mensa • Microscopium • Monoceros • Musca • Norma • Octans • Ophiuchus •

Orion • Pavo • Pegasus • Perseus • Phoenix • Pictor • Pisces • Piscis   Austrinus  • Puppis • Pyxis • Reticulum • Sagitta • Sagittarius • Scorpius • Sculptor • Scutum • Serpens •

Sextans • Taurus • Telescopium • Triangulum • Triangulum   Australe  • Tucana • Ursa   Major  • Ursa   Minor  • Vela • Virgo • Volans • Vulpecula

External links

Star Tales The Constellations Photographic Atlas of the Constellations Celestia free 3D realtime space-simulation (OpenGL) Stellarium realtime sky rendering program (OpenGL) Strasbourg Astronomical Data Center Files on official IAU constellation boundaries (the older

NASA ADC service does not function anymore) Interactive Sky Charts (Allows navigation through the entire sky with variable star detail,

optional constellation lines) http://www.astronomical.org/constellations/obs.html http://www.seds.org/Maps/Stars_en/Fig/const.html Constellations Articles Full constellation diagrams resembling their names Images of constellations The Constellations presented by Utah Skies

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