This article is about the astronomical constellation. For the astrological sign, see Capricorn (astrology). For "Capricornis", the genus of goat/antelope-like mammals, see Serow.
Visible at latitudes between +60° and −90°. Best visible at 21:00 (9 p.m.) during the month of September.
Capricornus is one of the constellations of the zodiac. Its name is Latin for "horned goat" or "goat horn" or "having horns like a goat's", and it is commonly represented in the form of a sea goat: a mythical creature that is half goat, half fish.
Capricornus is one of the 88 modern constellations, and was also one of the 48constellations listed by the 2ndcentury astronomer Claudius Ptolemy. Its old astronomical symbol is (♑︎). Under its modern boundaries it is bordered by Aquila, Sagittarius, Microscopium, Piscis Austrinus, and Aquarius. The constellation is located in an area of sky called the Sea or the Water, consisting of many water-related constellations such as Aquarius, Pisces and Eridanus. It is the smallest constellation in the zodiac.
Notable features
The constellation Capricornus as it can be seen with the naked eye
Capricornus is a faint constellation, with only one star above magnitude3; its alpha star has a magnitude of only 3.6.
The brightest star in Capricornus is δCapricorni, also called Deneb Algedi, with a magnitude of 2.9, located 39light-years from Earth. Like several other stars such as Denebola and Deneb, it is named for the Arabic word for "tail" (deneb); its traditional name means "the tail of the goat". Deneb Algedi is a Beta Lyrae variable star (a type of eclipsing binary). It ranges by about 0.2magnitudes with a period of 24.5hours.[3]
The other bright stars in Capricornus range in magnitude from 3.1 to 5.1. αCapricorni is a multiple star. The primary (α2Cap), 109light-years from Earth, is a yellow-hued giant star of magnitude3.6; the secondary (α1Cap), 690light-years from Earth, is a yellow-hued supergiant star of magnitude4.3. The two stars are distinguishable by the naked eye, and both are themselves multiple stars. α1Capricorni is accompanied by a star of magnitude9.2; α2Capricorni is accompanied by a star of magnitude 11.0; this faint star is itself a binary star with two components of magnitude11. Also called Algedi or Giedi, the traditional names of αCapricorni come from the Arabic word for "the kid", which references the constellation's mythology.[3]
β Capricorni is a double star also known as Dabih. It is a yellow-hued giant star of magnitude3.1, 340light-years from Earth. The secondary is a blue-white hued star of magnitude 6.1. The two stars are distinguishable in binoculars. βCapricorni's traditional name comes from the Arabic phrase for "the lucky stars of the slaughterer," a reference to ritual sacrifices performed by ancient Arabs at the heliacal rising of Capricornus.[4] Another star visible to the naked eye is γCapricorni, sometimes called Nashira ("bringing good tidings"); it is a white-hued giant star of magnitude3.7, 139light-years from Earth. π Capricorni is a double star with a blue-white hued primary of magnitude5.1 and a white-hued secondary of magnitude8.3. It is 670light-years from Earth and the components are distinguishable in a small telescope.[3]
Several galaxies and star clusters are contained within Capricornus. Messier 30 is a globular cluster located 1degree south of the galaxy group that contains NGC 7103. The constellation also harbors the wide spiral galaxy NGC 6907.
Messier 30 (NGC 7099) is a centrally-condensed globular cluster of magnitude 7.5. At a distance of 30,000light-years, it has chains of stars extending to the north that are resolvable in small amateur telescopes.[3]
One galaxy group located in Capricornus is HCG 87, a group of at least three galaxies located 400million light-years from Earth (redshift 0.0296). It contains a large elliptical galaxy, a face-on spiral galaxy, and an edge-on spiral galaxy. The face-on spiral galaxy is experiencing abnormally high rates of star formation, indicating that it is interacting with one or both members of the group. Furthermore, the large elliptical galaxy and the edge-on spiral galaxy, both of which have active nuclei, are connected by a stream of stars and dust, indicating that they too are interacting. Astronomers predict that the three galaxies may merge millions of years in the future to form a giant elliptical galaxy.[5]
History
The constellation was first attested in depictions on a cylinder-seal from around the 21stcenturyBCE,[6] it was explicitly recorded in the Babylonian star catalogues before 1000BCE. In the Early Bronze Age the winter solstice occurred in the constellation, but due to the precession of the equinoxes, the December solstice now takes place in the constellation Sagittarius.[7] The Sun is now in the constellation Capricorn (as distinct from the astrological sign) from late January through mid-February.[3]
Although the solstice during the northern hemisphere's winter no longer takes place while the sun is in the constellation Capricornus, as it did until 130BCE, the astrological sign called Capricorn is still used to denote the position of the solstice, and the latitude of the sun's most southerly position continues to be called the Tropic of Capricorn, a term which also applies to the line on the Earth at which the sun is directly overhead at local noon on the day of the December solstice.[3]
The planet Neptune was discovered by German astronomer Johann Galle, near Deneb Algedi (δCapricorni) on 23September 1846, as Capricornus can be seen best from Europe at 4:00AM in September (although, by modern constellation boundaries established in the early 20thcenturyCE, Neptune lay within the confines of Aquarius at the time of its discovery).
Mythology
Despite its faintness, the constellation Capricornus has one of the oldest mythological associations, having been consistently represented as a hybrid of a goat and a fish since the Middle Bronze Age, when the Babylonians used MULSUḪUR.MAŠ "The Goat-Fish" as a symbol of their god Ea.[7][6]
In Greek mythology, the constellation is sometimes identified as Amalthea, the goat that suckled the infant Zeus after his mother, Rhea, saved him from being devoured by his father, Cronos. Amalthea's broken horn was transformed into the cornucopia or "horn of plenty".[8]
Capricornus is also sometimes identified as Pan, the god with a goat's horns and legs, who saved himself from the monster Typhon by giving himself a fish's tail and diving into a river.[3]
Capricornus's brighter stars are found on a triangle whose vertices are α2 Capricorni (Giedi), δ Capricorni (Deneb Algiedi), and ω Capricorni. Ptolemy's method of connecting the stars of Capricornus has been influential.[9] Capricornus is usually drawn as a goat with the tail of a fish.[3]
Diagram of H.A. Rey's alternative way to connect the stars of the Capricornus constellation
H. A. Rey has suggested an alternative visualization, which graphically shows a goat.[10] The goat's head is formed by the triangle of stars ι Cap, θ Cap, and ζ Cap. The goat's horn sticks out with stars γ Cap and δ Cap. Star δ Cap, at the tip of the horn, is of the third magnitude. The goat's tail consists of stars β Cap and α2 Cap: star β Cap being of the third magnitude. The goat's hind foot consists of stars ψ Cap and ω Cap. Both of these stars are of the fourth magnitude.
1 2 Espak, Peeter (2006). Master's Thesis(PDF) (Masters). p.104. Archived(PDF) from the original on 2022-10-09.
1 2 Rogers, John H. (1998). "Origins of the ancient constellations: I.The Mesopotamian traditions". Journal of the British Astronomical Association. 108: 9–28. Bibcode:1998JBAA..108....9R.
Aries is one of the constellations of the zodiac. It is located in the Northern celestial hemisphere between Pisces to the west and Taurus to the east. The name Aries is Latin for ram. Its old astronomical symbol is (♈︎). It is one of the 48 constellations described by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations. It is a mid-sized constellation ranking 39th in overall size, with an area of 441 square degrees.
Aquarius is an equatorial constellation of the zodiac, between Capricornus and Pisces. Its name is Latin for "water-carrier" or "cup-carrier", and its old astronomical symbol is (♒︎), a representation of water. Aquarius is one of the oldest of the recognized constellations along the zodiac. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It is found in a region often called the Sea due to its profusion of constellations with watery associations such as Cetus the whale, Pisces the fish, and Eridanus the river.
Cetus is a constellation, sometimes called 'the whale' in English. The Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the sky that contains other water-related constellations: Aquarius, Pisces and Eridanus.
Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. In Greek mythology, Centaurus represents a centaur; a creature that is half human, half horse. Notable stars include Alpha Centauri, the nearest star system to the Solar System, its neighbour in the sky Beta Centauri, and HR 5171, one of the largest stars yet discovered. The constellation also contains Omega Centauri, the brightest globular cluster as visible from Earth and the largest identified in the Milky Way, possibly a remnant of a dwarf galaxy.
Cygnus is a northern constellation on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. Cygnus is one of the most recognizable constellations of the northern summer and autumn, and it features a prominent asterism known as the Northern Cross. Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.
Canes Venatici is one of the 88 constellations designated by the International Astronomical Union (IAU). It is a small northern constellation that was created by Johannes Hevelius in the 17th century. Its name is Latin for 'hunting dogs', and the constellation is often depicted in illustrations as representing the dogs of Boötes the Herdsman, a neighboring constellation.
Leo is one of the constellations of the zodiac, between Cancer the crab to the west and Virgo the maiden to the east. It is located in the Northern celestial hemisphere. Its name is Latin for lion, and to the ancient Greeks represented the Nemean Lion killed by the mythical Greek hero Heracles as one of his twelve labors. Its old astronomical symbol is (♌︎). One of the 48 constellations described by the 2nd-century astronomer Ptolemy, Leo remains one of the 88 modern constellations today, and one of the most easily recognizable due to its many bright stars and a distinctive shape that is reminiscent of the crouching lion it depicts.
Sagittarius is one of the constellations of the zodiac and is located in the Southern celestial hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Its old astronomical symbol is (♐︎). Its name is Latin for "archer". Sagittarius is commonly represented as a centaur drawing a bow. It lies between Scorpius and Ophiuchus to the west and Capricornus and Microscopium to the east.
Andromeda is one of the 48 constellations listed by the 2nd-century Greco-Roman astronomer Ptolemy, and one of the 88 modern constellations. Located in the northern celestial hemisphere, it is named for Andromeda, daughter of Cassiopeia, in the Greek myth, who was chained to a rock to be eaten by the sea monster Cetus. Andromeda is most prominent during autumn evenings in the Northern Hemisphere, along with several other constellations named for characters in the Perseus myth. Because of its northern declination, Andromeda is visible only north of 40° south latitude; for observers farther south, it lies below the horizon. It is one of the largest constellations, with an area of 722 square degrees. This is over 1,400 times the size of the full moon, 55% of the size of the largest constellation, Hydra, and over 10 times the size of the smallest constellation, Crux.
Draco is a constellation in the far northern sky. Its name is Latin for dragon. It was one of the 48 constellations listed by the 2nd century Greek astronomer Ptolemy, and remains one of the 88 modern constellations today. The north pole of the ecliptic is in Draco. Draco is circumpolar from northern latitudes, meaning that it never sets and can be seen at any time of year.
Eridanus is a constellation which stretches along the southern celestial hemisphere. It is represented as a river. One of the 48 constellations listed by the 2nd century astronomer Ptolemy, it remains one of the 88 modern constellations. It is the sixth largest of the modern constellations. The same name was later taken as a Latin name for the real Po River and also for the name of a minor river in Athens.
An asterism is an observed pattern or group of stars in the sky. Asterisms can be any identified pattern or group of stars, and therefore are a more general concept than the 88 formally defined constellations. Constellations are based on asterisms, but unlike asterisms, constellations outline and today completely divide the sky and all its celestial objects into regions around their central asterisms. For example, the asterism known as the Big Dipper comprises the seven brightest stars in the constellation Ursa Major. Another is the asterism of the Southern Cross, within the constellation of Crux.
Alpha Capricorni is an optical double star in the constellation of Capricornus. The two physically unrelated components are designated:
Delta Capricorni, or δ Capricorni, is a binary star located 38.7 light-years from the Sun in the constellation of Capricornus. The system consists of an eclipsing binary, Delta Capricorni A, and two visual companions that are over 10 magnitudes fainter, labeled B and C. Delta Capricorni A's two components are designated Delta Capricorni Aa and Ab. The primary star, Aa, is a white giant and the combined light of Aa and Ab makes it the brightest star in the constellation.
Gamma Serpentis is a star in the equatorial constellation Serpens, in the part of the constellation that represents the serpent's head. It has an apparent visual magnitude +3.85, which means it is visible to the naked eye. Based upon parallax measurements by the Hipparcos spacecraft, this star is approximately 36.7 light years from Earth.
Theta Capricorni, Latinized from θ Capricorni, is a white-hued star in the southern constellation of Capricornus, positioned 0.58° south of the ecliptic. Sometimes, this star is called by the name Dorsum, meaning the back in Latin. It can be seen with the naked eye, having an apparent visual magnitude of +4.07. Based upon an annual parallax shift of 20.11 mas as seen from the Earth, the star is about 162 light years from the Sun. It is drifting closer with a radial velocity of −11 km/s.
Iota Capricorni is a solitary, yellow-hued star in the southern constellation of Capricornus. It can be seen with the naked eye, having an apparent visual magnitude of +4.3. Based upon an annual parallax shift of 16.2 mas as seen from the Earth, the star is located about 201 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.08 due to interstellar dust.
Alpha2 Capricorni, or Algedi, is a triple star system in the southern constellation of Capricornus. It is visible to the naked eye with an apparent visual magnitude of +3.57. It is separated from the fainter α¹ Capricorni by 0.11° of the sky, a gap just resolvable with the naked eye, similar to Mizar and Alcor. Based on parallax shift as refined from orbits around the Sun of the Gaia spacecraft at Earth's Lagrange point 2, the star is 101 to 103 light years from the Solar System.
Rho Capricorni is a binary star in the constellation Capricornus. Sometimes, this star is called by the name Bos, meaning the cow in Latin. In Chinese, 牛宿, meaning Ox (asterism), refers to an asterism consisting of β Capricorni, α2 Capricorni, ξ2 Capricorni, π Capricorni, ο Capricorni and ρ Capricorni. Consequently, the Chinese name for ρ Capricorni itself is 牛宿六
Gemini is one of the constellations of the zodiac and is located in the northern celestial hemisphere. It was one of the 48 constellations described by the 2nd century AD astronomer Ptolemy, and it remains one of the 88 modern constellations today. Its name is Latin for twins, and it is associated with the twins Castor and Pollux in Greek mythology. Its old astronomical symbol is (♊︎).
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(♑︎). Under its modern boundaries it is bordered by Aquila, Sagittarius, Microscopium, Piscis Austrinus, and Aquarius. The constellation is located in an area of sky called the Sea or the Water, consisting of many water-related constellations such as Aquarius, Pisces and Eridanus. It is the smallest constellation in the zodiac.
