Constellation

European constellationModern constellationMCAconstellationsdark cloud constellationsnight skyInca constellationconstellation nameDark-cloud constellationsdark area or clouds
A constellation is a group of stars that forms an imaginary outline or pattern on the celestial sphere, typically representing an animal, mythological person or creature, a god, or an inanimate object.wikipedia
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Aratus

AratosPhaenomenaAratus of Soli
They are given in Aratus' work Phenomena and Ptolemy's Almagest, though their origin probably predates these works by several centuries. It is roughly based on the traditional Greek constellations listed by Ptolemy in his Almagest in the 2nd century and Aratus' work Phenomena, with early modern modifications and additions (most importantly introducing constellations covering the parts of the southern sky unknown to Ptolemy) by Petrus Plancius (1592, 1597/98 and 1613), Johannes Hevelius (1690) and Nicolas Louis de Lacaille (1763), who named fourteen constellations and renamed a fifteenth one. Greek astronomy essentially adopted the older Babylonian system in the Hellenistic era, first introduced to Greece by Eudoxus of Cnidus in the 4th century BC. The original work of Eudoxus is lost, but it survives as a versification by Aratus, dating to the 3rd century BC. The most complete existing works dealing with the mythical origins of the constellations are by the Hellenistic writer termed pseudo-Eratosthenes and an early Roman writer styled pseudo-Hyginus.
It describes the constellations and other celestial phenomena.

Taurus (constellation)

TaurusTauriTaurus constellation
Examples include the Pleiades and Hyades within the constellation Taurus and the False Cross split between the southern constellations Carina and Vela, or Venus' Mirror in the constellation of Orion.
Taurus (Latin for "the Bull") is one of the constellations of the zodiac, which means it is crossed by the plane of the ecliptic.

Carina (constellation)

Carinaconstellation CarinaCarinae
Examples include the Pleiades and Hyades within the constellation Taurus and the False Cross split between the southern constellations Carina and Vela, or Venus' Mirror in the constellation of Orion.
Carina is a constellation in the southern sky.

Orion (constellation)

OrionOrion constellationconstellation of Orion
Where possible, these modern constellations usually share the names of their Graeco-Roman predecessors, such as Orion, Leo or Scorpius.
Orion is a prominent constellation located on the celestial equator and visible throughout the world.

Vela (constellation)

VelaFalse CrossVel
Examples include the Pleiades and Hyades within the constellation Taurus and the False Cross split between the southern constellations Carina and Vela, or Venus' Mirror in the constellation of Orion.
Vela is a constellation in the southern sky.

Asterism (astronomy)

asterismasterismsconstellation
Examples include the Pleiades and Hyades within the constellation Taurus and the False Cross split between the southern constellations Carina and Vela, or Venus' Mirror in the constellation of Orion. Other star patterns or groups called asterisms are not constellations per se but are used by observers to navigate the night sky.
This colloquial definition makes it appear quite similar to a constellation, but they differ mostly in that a constellation is an officially recognized area of the sky, while an asterism is a visually obvious collection of stars and the lines used to mentally connect them; as such, asterisms do not have officially determined boundaries and are therefore a more general concept which may refer to any identified pattern of stars.

Ursa Major

Great BearOrsa MaggioreUMa
Another example is the popular northern asterism known as the Big Dipper (US) or the Plough (UK), composed of the seven brightest stars within the area of the IAU-defined constellation of Ursa Major.
Ursa Major (also known as the Great Bear) is a constellation in the northern sky, whose associated mythology likely dates back into prehistory.

Big Dipper

PloughNorthern DipperBeidou
Another example is the popular northern asterism known as the Big Dipper (US) or the Plough (UK), composed of the seven brightest stars within the area of the IAU-defined constellation of Ursa Major.
The Big Dipper (US) or the Plough (UK, Ireland) is a large asterism consisting of seven bright stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez, of third magnitude.

Johannes Hevelius

HeveliusJan HeveliusHevelius, Johannes
It is roughly based on the traditional Greek constellations listed by Ptolemy in his Almagest in the 2nd century and Aratus' work Phenomena, with early modern modifications and additions (most importantly introducing constellations covering the parts of the southern sky unknown to Ptolemy) by Petrus Plancius (1592, 1597/98 and 1613), Johannes Hevelius (1690) and Nicolas Louis de Lacaille (1763), who named fourteen constellations and renamed a fifteenth one.
As an astronomer, he gained a reputation as "the founder of lunar topography", and described ten new constellations, seven of which are still used by astronomers.

Hyades (star cluster)

HyadesHyades clusterHyades star cluster
Examples include the Pleiades and Hyades within the constellation Taurus and the False Cross split between the southern constellations Carina and Vela, or Venus' Mirror in the constellation of Orion.
From the perspective of observers on Earth, the Hyades Cluster appears in the constellation Taurus, where its brightest stars form a "V" shape along with the still brighter Aldebaran.

Southern celestial hemisphere

southern skysouthern hemispheresouthern skies
Constellations in the far southern sky were added from the 15th century until the mid-18th century when European explorers began traveling to the Southern Hemisphere.
This arbitrary sphere, on which seemingly fixed stars form constellations, appears to rotate westward around a polar axis due to Earth's rotation.

Circumpolar constellation

circumpolarcircumpolar starsever-visible
From the North Pole or South Pole, all constellations south or north of the celestial equator are circumpolar.
In astronomy, a circumpolar constellation is a constellation (group of stars) that never sets below the horizon, as viewed from a location on Earth.

Decan

decansDecanic astrologydecan stars
Some of these were combined with Greek and Babylonian astronomical systems culminating in the Zodiac of Dendera, but it remains unclear when this occurred, but most were placed during the Roman period between 2nd to 4th centuries AD. The oldest known depiction of the zodiac showing all the now familiar constellations, along with some original Egyptian constellations, decans, and planets.
The decans (Egyptian bakiu) are 36 groups of stars (small constellations) used in the Ancient Egyptian astronomy.

Flamsteed designation

designationFlamsteedFlamsteed numbers
The Flamsteed designation of a star, for example, consists of a number and the genitive form of the constellation name.
Each star is assigned a number and the Latin genitive of the constellation it lies in (see 88 modern constellations for a list of constellations and the genitive forms of their names).

Chinese constellations

Southern AsterismsExotic BirdThe Southern Asterisms
These constellations are some of the most important observations of Chinese sky, attested from the 5th century BC. Parallels to the earliest Babylonian (Sumerian) star catalogues suggest that the ancient Chinese system did not arise independently.
Traditional Chinese astronomy has a system of dividing the celestial sphere into asterisms or constellations, known as "officials" (Chinese xīng guān).

Ptolemy

Claudius PtolemyPtolemaicPtol.
They are given in Aratus' work Phenomena and Ptolemy's Almagest, though their origin probably predates these works by several centuries.
Its list of forty-eight constellations is ancestral to the modern system of constellations, but unlike the modern system they did not cover the whole sky (only the sky Hipparchus could see).

Catasterismi

catasterismpseudo-Eratosthenesset among the stars
Greek astronomy essentially adopted the older Babylonian system in the Hellenistic era, first introduced to Greece by Eudoxus of Cnidus in the 4th century BC. The original work of Eudoxus is lost, but it survives as a versification by Aratus, dating to the 3rd century BC. The most complete existing works dealing with the mythical origins of the constellations are by the Hellenistic writer termed pseudo-Eratosthenes and an early Roman writer styled pseudo-Hyginus.
Catasterismi (Greek Καταστερισμοί Katasterismoi, "placings among the stars") is an Alexandrian prose retelling of the mythic origins of stars and constellations, as they were interpreted in Hellenistic culture.

Pleiades

Pleiades star clusterM45the Pleiades
Examples include the Pleiades and Hyades within the constellation Taurus and the False Cross split between the southern constellations Carina and Vela, or Venus' Mirror in the constellation of Orion.
Some Greek astronomers considered them to be a distinct constellation, and they are mentioned by Hesiod's Works and Days, Homer's Iliad and Odyssey, and the Geoponica.

Almagest

star catalog of PtolemyPtolemy's ''Almagestcatalog
They are given in Aratus' work Phenomena and Ptolemy's Almagest, though their origin probably predates these works by several centuries.
Books VII and VIII cover the motions of the fixed stars, including precession of the equinoxes. They also contain a star catalogue of 1022 stars, described by their positions in the constellations, together with ecliptic longitude and latitude. Ptolemy states that the longitudes (which increase due to precession) are for the beginning of the reign of Antoninus Pius (138 AD), whereas the latitudes do not change with time. (But see below, under The star catalog.) The constellations north of the zodiac and the northern zodiac constellations (Aries through Virgo) are in the table at the end of Book VII, while the rest are in the table at the beginning of Book VIII. The brightest stars were marked first magnitude (m = 1), while the faintest visible to the naked eye were sixth magnitude (m = 6). Each numerical magnitude was considered twice the brightness of the following one, which is a logarithmic scale. (The ratio was subjective as no photodetectors existed.) This system is believed to have originated with Hipparchus. The stellar positions too are of Hipparchan origin, despite Ptolemy's claim to the contrary.

Argo Navis

ArgoArgosSouth Pole Star
Southern constellations are more modern inventions, sometimes as substitutes for ancient constellations (e.g. Argo Navis).
Argo Navis (the Ship Argo), or simply Argo, was a large constellation in the southern sky that has since been divided into the three constellations of Carina, Puppis and Vela.

Proper motion

proper motionsproper-motionhigh proper motion star
Astronomers can predict the past or future constellation outlines by measuring individual stars' common proper motions or cpm by accurate astrometry and their radial velocities by astronomical spectroscopy.
Over the course of centuries, stars appear to maintain nearly fixed positions with respect to each other, so that they form the same constellations over historical time.

Boötes

BootesBooBoötis
The northern constellation Quadrans Muralis survived into the 19th century (when its name was attached to the Quadrantid meteor shower), but is now divided between Boötes and Draco.
Boötes is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere.

Draco (constellation)

DracoDraco constellationDragone
The northern constellation Quadrans Muralis survived into the 19th century (when its name was attached to the Quadrantid meteor shower), but is now divided between Boötes and Draco.
Draco is a constellation in the far northern sky.

Leo (constellation)

Leoconstellation of Leoconstellation Leo
Where possible, these modern constellations usually share the names of their Graeco-Roman predecessors, such as Orion, Leo or Scorpius.
Leo is one of the constellations of the zodiac, lying between Cancer the crab to the west and Virgo the maiden to the east.

Scorpius

ScorpioScorpionScorpione
Where possible, these modern constellations usually share the names of their Graeco-Roman predecessors, such as Orion, Leo or Scorpius.
Scorpius is one of the constellations of the zodiac.