72-505: Circinus is a small, faint constellation in the southern sky , first defined in 1756 by the French astronomer Nicolas-Louis de Lacaille . Its name is Latin for compass , referring to the drafting tool used for drawing circles (it should not be confused with Pyxis , a constellation that represents a mariner's compass which points north). Its brightest star is Alpha Circini , with an apparent magnitude of 3.19. Slightly variable , it
144-468: A Jupiter -like planet (1.6 M J ) discovered in 2010 via the radial velocity method, orbits this star at a distance of 2.9 AU, approximately every 1840 days. As this constellation intersects the plane of the Milky Way, there are many massive stars located in this constellation, including GKF2010 MN18 (or simply MN18), a blue supergiant located in a bipolar nebula, as well as 9 Wolf-Rayet stars ,
216-464: A long-period comet . In 2011, Peter Jenniskens proposed that the debris trail of comet C/1969 T1 could intersect with the Earth's orbit and generate a meteor outburst coming from a radiant close to Beta Circini. The ACI shower peaks on 4 June, the day it was first observed. Constellation Four views of the constellation Orion : A constellation is an area on the celestial sphere in which
288-405: A meteor shower also discovered in 1977, radiate from this constellation. In 1756, French astronomer Nicolas-Louis de Lacaille introduced the constellation of Circinus with the French name le Compas , representing a pair of dividing compasses , on a chart of the southern sky. On that chart, Lacaille portrayed the constellations of Norma , Circinus, and Triangulum Australe , respectively, as
360-433: A rapidly oscillating Ap (RoAp) star in the night sky. It has the unusual spectral type A7 Vp SrCrEu, showing increased emissions of strontium , chromium and europium . Stars of this type have oddly localised magnetic fields and are slightly variable . Alpha Circini forms a binary star system with an orange dwarf companion of spectral type K5 and magnitude 8.5, which with a separation of 5.7 arcseconds
432-440: A close binary system can accumulate material from its companion until it ignites and blows off in a thermonuclear explosion, known as a nova . These stars generally brighten by 7 to 16 magnitudes. Nova Circini 1926, also known as X Circini , was observed at magnitude 6.5 on 3 September 1926, before fading and fluctuating between magnitudes 11.7 and 12.5, during 1928, and magnitude 13, in 1929. Nova Circini 1995 ( BY Circini ) reached
504-656: A group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellations were likely defined in prehistory . People used them to relate stories of their beliefs, experiences, creation , and mythology . Different cultures and countries invented their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. The recognition of constellations has changed significantly over time. Many changed in size or shape. Some became popular, only to drop into obscurity. Some were limited to
576-563: A larger instrument and averted vision to be seen. Circinus also houses ESO 97-G13, commonly known as the Circinus Galaxy . Discovered in 1977, it is a relatively unobscured galaxy (magnitude 10.6), which is unusual for galaxies located in constellations near the Milky Way , since their dim light is obscured by gas and dust. This oblong spiral galaxy with 6.9 by 3.0 arcminutes and 26,000 light-years in diameter,
648-452: A list of 88 constellations with three-letter abbreviations for them. However, these constellations did not have clear borders between them. In 1928, the IAU formally accepted the 88 modern constellations, with contiguous boundaries along vertical and horizontal lines of right ascension and declination developed by Eugene Delporte that, together, cover the entire celestial sphere; this list
720-421: A long tradition of observing celestial phenomena. Nonspecific Chinese star names , later categorized in the twenty-eight mansions , have been found on oracle bones from Anyang , dating back to the middle Shang dynasty . 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
792-443: A magnitude of 9.8 around a central star of magnitude 14.2, located 5.2 degrees west-southwest of Alpha Circini. It is only visible as a disc at magnifications over 200-fold. Bernes 145 is a dark and reflection nebula first listed in the 1971 Bernes Catalog. The dark nebula component is easily visible in a large amateur telescope, and it measures 12 by 5 arcminutes. The smaller reflection nebula component requires
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#1732782955247864-656: A maximum apparent magnitude of 7.2 in January 1995. BW Circini is a low mass X-ray binary system, comprising a black hole of around 8 solar masses and a yellow G0III-G5III subgiant star. X-ray outbursts were recorded in 1987 and 1997, and possibly 1971–72. Circinus is the radiant of an annual meteor shower , the Alpha Circinids (ACI). First observed in Queensland in 1977, the meteors have an average velocity of 27.1 km/s and are thought to be associated with
936-499: A period of 2 hours 33 minutes. Over 99% of its composition appears to be helium. Its origin is unclear, but thought to be the result of the merger of a helium and a carbon/oxygen white dwarf. Several stars with planetary systems lie within the borders of Circinus, although none of the host stars are particularly prominent. HD 134060 is a sun-like yellow dwarf star of spectral type G0VFe+0.4 and magnitude 6.29, around 79 light-years away. Its two planets were discovered in 2011 through
1008-479: A set square and ruler, a compass, and a surveyor's level in a set of draughtsman's instruments. Circinus was given its current name in 1763, when Lacaille published an updated sky map with Latin names for the constellations he introduced. Bordered by Centaurus , Musca , Apus , Triangulum Australe, Norma and Lupus , Circinus lies adjacent to the Alpha and Beta Centauri stars. As it is at declination −50° to −70°,
1080-582: A similar cluster, NGC 5822 , nearby in Lupus . Comparatively, open cluster NGC 5715 is fainter (integrated magnitude of 9.8)—its brightest star is only 11th magnitude—and smaller (7.0 arcminutes), comprising only 30 stars. The third open cluster, Pismis 20 , contains 12 stars in a diameter of 4.5 arcseconds but exhibits a magnitude similar to NGC 5823 (7.8). At 8270 light-years, it requires an amateur telescope with an aperture over 300 mm to be easily discerned. The planetary nebula NGC 5315 has
1152-661: A single culture or nation. Naming constellations also helped astronomers and navigators identify stars more easily. Twelve (or thirteen) ancient constellations belong to the zodiac (straddling the ecliptic , which the Sun , Moon , and planets all traverse). The origins of the zodiac remain historically uncertain; its astrological divisions became prominent c. 400 BC in Babylonian or Chaldean astronomy. Constellations appear in Western culture via Greece and are mentioned in
1224-440: A telescope of 150 mm to be seen, as they are only 0.8 arcseconds apart. The brighter component is a bluish Be star of spectral type B5IV+ and magnitude 4.51, while the dimmer component is a yellow star of magnitude 5.5. They orbit each other every 180 years. Delta Circini is also a multiple star whose components have magnitudes of 5.1 and 13.4 and orbit around a common centre of gravity every 3.9 days. The brighter component
1296-437: A very high number for such a small constellation. Three open clusters and a planetary nebulae are found within the borders of Circinus, all visible with amateur telescopes of varying sizes. NGC 5823 , also called Caldwell 88, is an 800-million-year-old open cluster, located 3500 light-years away and spanning a 12-light-year region along the constellation's northern border. Despite having an integrated magnitude of 7.9,
1368-478: A very small range or are quite dim. Three prominent examples are Theta Circini , T Circini , and AX Circini . Theta Circini is a B-class irregular variable, ranging in magnitude from 5.0 to 5.4. T Circini has a B-type spectrum, ranging in magnitude from 10.6 to 9.3 over a period of 3.298 days, although it is actually an eclipsing binary system rather than a pulsating star. AX is a Cepheid variable that varies between magnitudes 5.6 and 6.19 over 5.3 days. It
1440-524: Is a close eclipsing binary (specifically, a rotating ellipsoidal variable ), with a minor dip of magnitude (0.1). Both are hot blue stars of spectral types O7III-V and O9.5V, respectively, and are estimated to have around 22 and 12 times the Sun's mass. Over 3600 light-years away, this system would outshine Venus at magnitude −4.8 if it were 32 light-years (10 parsecs ) distant. The two main components are separated by 50 arcseconds, resolvable to
1512-417: Is a yellow-white supergiant of spectral type F8II+, 1600 light-years away. BP Circini is another Cepheid variable with an apparent magnitude ranging from 7.37 to 7.71 over 2.4 days. Both cepheids are spectroscopic binaries, with companions that are blue-white stars of spectral type B6 and 5 and 4.7 solar masses, respectively. BX Circini is a faint star that fluctuates between magnitudes 12.57 and 12.62 over
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#17327829552471584-484: Is located 13 million light-years away from Earth and lies 4 degrees off the galactic plane . It is the closest Seyfert galaxy to the Milky Way, and therefore hosts an active galactic nucleus . Circinus X-1 is an X-ray binary star system that includes a neutron star . Observations of Circinus X-1 in July 2007 revealed the presence of X-ray jets normally found in black hole systems. Located at 19,000 light-years,
1656-454: Is only discernible with a telescope. The distance between the two stars is 260 AU and they take 2600 years to rotate around a common centre of gravity. The second brightest star is Beta Circini , a white main sequence star of spectral type A3Va and a magnitude of 4.07, about 100 light-years away. It has around 1.8 times the diameter of the Sun. Gamma Circini is a binary star 450 light-years away, whose components need
1728-645: Is the Suzhou Astronomical Chart , which was prepared with carvings of stars on the planisphere of the Chinese sky on a stone plate; it is done accurately based on observations, and it shows the supernova of the year of 1054 in Taurus. Influenced by European astronomy during the late Ming dynasty , charts depicted more stars but retained the traditional constellations. Newly observed stars were incorporated as supplementary to old constellations in
1800-471: Is the brightest rapidly oscillating Ap star in the night sky. AX Circini is a Cepheid variable visible with the unaided eye, and BX Circini is a faint star thought to have been formed from the merger of two white dwarfs . Two sun-like stars have planetary systems: HD 134060 has two small planets, and HD 129445 has a Jupiter -like planet. Supernova SN 185 appeared in Circinus in 185 AD and
1872-575: The Inca civilization identified various dark areas or dark nebulae in the Milky Way as animals and associated their appearance with the seasonal rains. Australian Aboriginal astronomy also describes dark cloud constellations, the most famous being the "emu in the sky" whose head is formed by the Coalsack , a dark nebula, instead of the stars. Footnotes Citations Rapidly oscillating Ap star Too Many Requests If you report this error to
1944-616: The KJV , but ‘Ayish "the bier" actually corresponding to Ursa Major. The term Mazzaroth מַזָּרוֹת , translated as a garland of crowns , is a hapax legomenon in Job 38:32, and it might refer to the zodiacal constellations. There is only limited information on ancient Greek constellations, with some fragmentary evidence being found in the Works and Days of the Greek poet Hesiod , who mentioned
2016-675: The Zodiac of Dendera ; 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 . Ptolemy's Almagest remained the standard definition of constellations in the medieval period both in Europe and in Islamic astronomy . Ancient China had
2088-592: The horizon when viewed from a particular latitude on Earth is termed circumpolar . From the North Pole or South Pole , all constellations south or north of the celestial equator are circumpolar . Depending on the definition, equatorial constellations may include those that lie between declinations 45° north and 45° south, or those that pass through the declination range of the ecliptic (or zodiac ) ranging between 23.5° north and 23.5° south . Stars in constellations can appear near each other in
2160-444: The radial velocity method : the smaller, HD 134060 b , has a mass of 0.0351 M J (Jupiter masses) and orbits its star every 3.27 days, at 0.0444 AU; the larger, HD 134060 c (0.15 M J ), orbits farther out at 2.226 AU, with a period of approximately 1161 days. Even fainter, at magnitude 8.8, HD 129445 is 220 light-years away and has 99% of the Sun's mass and a similar spectral type of G8V. HD 129445 b ,
2232-458: The "heavenly bodies". 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
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2304-607: The 14th century. The Ancient Greek word for constellation is ἄστρον ( astron ). These terms historically referred to any recognisable pattern of stars whose appearance was associated with mythological characters or creatures, earthbound animals, or objects. Over time, among European astronomers, the constellations became clearly defined and widely recognised. In the 20th century, the International Astronomical Union (IAU) recognized 88 constellations . A constellation or star that never sets below
2376-529: The 17,000-year-old cave paintings in Lascaux , southern France, depict star constellations such as Taurus, Orion's Belt, and the Pleiades. However, this view is not generally accepted among scientists. Inscribed stones and clay writing tablets from Mesopotamia (in modern Iraq) dating to 3000 BC provide the earliest generally accepted evidence for humankind's identification of constellations. It seems that
2448-503: The 88 IAU-recognized constellations in this region first appeared on celestial globes developed in the late 16th century by Petrus Plancius , based mainly on observations of the Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman . These became widely known through Johann Bayer 's star atlas Uranometria of 1603. Fourteen more were created in 1763 by the French astronomer Nicolas Louis de Lacaille , who also split
2520-742: The Hellenistic writer termed pseudo-Eratosthenes and an early Roman writer styled pseudo- Hyginus . The basis of Western astronomy as taught during Late Antiquity and until the Early Modern period is the Almagest by Ptolemy , written in the 2nd century. In the Ptolemaic Kingdom , native Egyptian tradition of anthropomorphic figures represented the planets, stars, and various constellations. Some of these were combined with Greek and Babylonian astronomical systems culminating in
2592-504: The IAU as well as those by cultures throughout history are imagined figures and shapes derived from the patterns of stars in the observable sky. Many officially recognized constellations are based on the imaginations of ancient, Near Eastern and Mediterranean mythologies. Some of these stories seem to relate to the appearance of the constellations, e.g. the assassination of Orion by Scorpius, their constellations appearing at opposite times of year. Constellation positions change throughout
2664-585: The Latin poet Ovid . 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 . Due to Roman and European transmission, each constellation has a Latin name. In 1922, the International Astronomical Union (IAU) formally accepted the modern list of 88 constellations , and in 1928 adopted official constellation boundaries that together cover
2736-572: The Navigator in c. 500 BC. The history of southern constellations is not straightforward. Different groupings and different names were proposed by various observers, some reflecting national traditions or designed to promote various sponsors. Southern constellations were important from the 14th to 16th centuries, when sailors used the stars for celestial navigation . Italian explorers who recorded new southern constellations include Andrea Corsali , Antonio Pigafetta , and Amerigo Vespucci . Many of
2808-647: The ancient Chinese system did not arise independently. Three schools of classical Chinese astronomy in the Han period are attributed to astronomers of the earlier Warring States period . The constellations of the three schools were conflated into a single system by Chen Zhuo , an astronomer of the 3rd century ( Three Kingdoms period ). Chen Zhuo's work has been lost, but information on his system of constellations survives in Tang period records, notably by Qutan Xida . The oldest extant Chinese star chart dates to that period and
2880-409: The ancient constellation Argo Navis into three; these new figures appeared in his star catalogue, published in 1756. Several modern proposals have not survived. The French astronomers Pierre Lemonnier and Joseph Lalande , for example, proposed constellations that were once popular but have since been dropped. The northern constellation Quadrans Muralis survived into the 19th century (when its name
2952-733: The bulk of the Mesopotamian constellations were created within a relatively short interval from around 1300 to 1000 BC. Mesopotamian constellations appeared later in many of the classical Greek constellations. The oldest Babylonian catalogues of stars and constellations date back to the beginning of the Middle Bronze Age , most notably the Three Stars Each texts and the MUL.APIN , an expanded and revised version based on more accurate observation from around 1000 BC. However,
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3024-600: The celestial equator), and southern constellations Puppis , Vela , Carina , Crux , Centaurus , Triangulum Australe , and Ara . Polaris , being the North Star, is the approximate center of the northern celestial hemisphere. It is part of Ursa Minor , constituting the end of the Little Dipper's handle. From latitudes of around 35° north, in January, Ursa Major (containing the Big Dipper ) appears to
3096-536: The cluster can be seen by star hopping from Beta Circini or from Alpha Centauri. It contains 80–100 stars of 10th magnitude and fainter, which are spread out over a diameter of 10 arcseconds. The brighter stars, however, are not true members of the cluster, as they are closer to the Earth than the dimmer ones. NGC 5823 appears distinct to the observer, sometimes seen as a reversed "S", as described by John Herschel , although it has also been described as "tulip-shaped" and "boxy". That cluster can be easily mistaken with
3168-412: The constellation, as adopted by the International Astronomical Union in 1922, is "Cir". Circinus is a faint constellation, with only one star brighter than fourth magnitude. Alpha Circini , a white main sequence star with an apparent magnitude of 3.19, is 54 light-years away and 4° south of Alpha Centauri . Not only the brightest star in the constellation, it is also the brightest example of
3240-661: The daytime and lower at night, while in winter the reverse is true, for both hemispheres. Due to the Solar System 's 60° tilt, the galactic plane of the Milky Way is inclined 60° from the ecliptic, between Taurus and Gemini (north) and Scorpius and Sagittarius (south and near which the Galactic Center can be found). The galaxy appears to pass through Aquila (near the celestial equator) and northern constellations Cygnus , Cassiopeia , Perseus , Auriga , and Orion (near Betelgeuse ), as well as Monoceros (near
3312-524: The development of today's accepted modern constellations. The southern sky, below about −65° declination , was only partially catalogued by ancient Babylonians, Egyptians, Greeks, Chinese, and Persian astronomers of the north. The knowledge that northern and southern star patterns differed goes back to Classical writers, who describe, for example, the African circumnavigation expedition commissioned by Egyptian Pharaoh Necho II in c. 600 BC and those of Hanno
3384-399: The early constellations were never universally adopted. Stars were often grouped into constellations differently by different observers, and the arbitrary constellation boundaries often led to confusion as to which constellation a celestial object belonged. Before astronomers delineated precise boundaries (starting in the 19th century), constellations generally appeared as ill-defined regions of
3456-425: The ecliptic), approximating a great circle . Zodiacal constellations of the northern sky are Pisces , Aries , Taurus , Gemini , Cancer , and Leo . In the southern sky are Virgo , Libra , Scorpius , Sagittarius , Capricornus , and Aquarius . The zodiac appears directly overhead from latitudes of 23.5° north to 23.5° south, depending on the time of year. In summer, the ecliptic appears higher up in
3528-475: The entire celestial sphere. Any given point in a celestial coordinate system lies in one of the modern constellations. Some astronomical naming systems include the constellation where a given celestial object is found to convey its approximate location in the sky. The Flamsteed designation of a star, for example, consists of a number and the genitive form of the constellation's name. Other star patterns or groups called asterisms are not constellations under
3600-507: The form of star charts , whose oldest representation appears on the statue known as the Farnese Atlas , based perhaps on the star catalogue of the Greek astronomer Hipparchus . Southern constellations are more modern inventions, sometimes as substitutes for ancient constellations (e.g. Argo Navis ). Some southern constellations had long names that were shortened to more usable forms; e.g. Musca Australis became simply Musca. Some of
3672-621: The formal definition, but are also used by observers to navigate the night sky. Asterisms may be several stars within a constellation, or they may share stars with more than one constellation. Examples of asterisms include the teapot within the constellation Sagittarius , or the big dipper in the constellation of Ursa Major . The word constellation comes from the Late Latin term cōnstellātiō , which can be translated as "set of stars"; it came into use in Middle English during
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#17327829552473744-414: The naked eye for individuals with good vision and easily discernible with a telescope. Eta Circini is a yellow giant of spectral type G8III and magnitude 5.17, located around 276 light-years distant, and Zeta Circini is a blue-white main sequence star of spectral type B3V and magnitude 6.09, located around 1273 light-years away. 493 variable stars have been recorded in Circinus, but most have
3816-449: The northeast, while Cassiopeia is the northwest. To the west are Pisces (above the horizon) and Aries. To the southwest Cetus is near the horizon. Up high and to the south are Orion and Taurus. To the southeast above the horizon is Canis Major . Appearing above and to the east of Orion is Gemini : also in the east (and progressively closer to the horizon) are Cancer and Leo. In addition to Taurus, Perseus and Auriga appear overhead. From
3888-602: The numerous Sumerian names in these catalogues suggest that they built on older, but otherwise unattested, Sumerian traditions of the Early Bronze Age . The classical Zodiac is a revision of Neo-Babylonian constellations from the 6th century BC. The Greeks adopted the Babylonian constellations in the 4th century BC. Twenty Ptolemaic constellations are from the Ancient Near East. Another ten have
3960-538: 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 introduced fourteen new constellations. Lacaille studied the stars of the southern hemisphere from 1751 until 1752 from the Cape of Good Hope , when he was said to have observed more than 10,000 stars using a refracting telescope with an aperture of 0.5 inches (13 mm). In 1922, Henry Norris Russell produced
4032-455: The pole star include Chamaeleon , Apus and Triangulum Australe (near Centaurus), Pavo , Hydrus , and Mensa . Sigma Octantis is the closest star approximating a southern pole star, but is faint in the night sky. Thus, the pole can be triangulated using the constellation Crux as well as the stars Alpha and Beta Centauri (about 30° counterclockwise from Crux) of the constellation Centaurus (arching over Crux). It has been suggested that
4104-557: The pulsar PSR B1509-58 , also called the Circinus Pulsar, has expelled a 20-light-year-long jet of material from its southern pole, clearly visible in the X-ray spectrum. Another supernova remnant in Circinus is that of SN 185 . Recorded by Chinese observers in 185 AD, SN 185 was visible in the night sky for around eight months; its remnants, known as RCW 86, cover an area larger than the typical full moon. A white dwarf star in
4176-644: The same latitude, in July, Cassiopeia (low in the sky) and Cepheus appear to the northeast. Ursa Major is now in the northwest. Boötes is high up in the west. Virgo is to the west, with Libra southwest and Scorpius south. Sagittarius and Capricorn are southeast. Cygnus (containing the Northern Cross ) is to the east. Hercules is high in the sky along with Corona Borealis . January constellations include Pictor and Reticulum (near Hydrus and Mensa, respectively). In July, Ara (adjacent to Triangulum Australe) and Scorpius can be seen. Constellations near
4248-836: The same stars but different names. Biblical scholar E. W. Bullinger interpreted some of the creatures mentioned in the books of Ezekiel and Revelation as the middle signs of the four-quarters of the Zodiac, with the Lion as Leo , the Bull as Taurus , the Man representing Aquarius , and the Eagle standing in for Scorpio . The biblical Book of Job also makes reference to a number of constellations, including עיש ‘Ayish "bier", כסיל chesil "fool" and כימה chimah "heap" (Job 9:9, 38:31–32), rendered as "Arcturus, Orion and Pleiades" by
4320-518: The sky, but they usually lie at a variety of distances away from the Earth. Since each star has its own independent motion, all constellations will change slowly over time. After tens to hundreds of thousands of years, familiar outlines will become unrecognizable. Astronomers can predict the past or future constellation outlines by measuring common proper motions of individual stars by accurate astrometry and their radial velocities by astronomical spectroscopy . The 88 constellations recognized by
4392-564: The sky. Today they now follow officially accepted designated lines of right ascension and declination based on those defined by Benjamin Gould in epoch 1875.0 in his star catalogue Uranometria Argentina . The 1603 star atlas " Uranometria " of Johann Bayer assigned stars to individual constellations and formalized the division by assigning a series of Greek and Latin letters to the stars within each constellation. These are known today as Bayer designations . Subsequent star atlases led to
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#17327829552474464-536: The southern hemisphere of the sky based on the knowledge of Western star charts; with this improvement, the Chinese Sky was integrated with the World astronomy. Historically, the origins of the constellations of the northern and southern skies are distinctly different. Most northern constellations date to antiquity, with names based mostly on Classical Greek legends. Evidence of these constellations has survived in
4536-595: The southern sky, which did not depict the traditional stars recorded by ancient Chinese astronomers. Further improvements were made during the later part of the Ming dynasty by Xu Guangqi and Johann Adam Schall von Bell , the German Jesuit and was recorded in Chongzhen Lishu (Calendrical Treatise of Chongzhen period , 1628). Traditional Chinese star maps incorporated 23 new constellations with 125 stars of
4608-515: The whole constellation is only visible south of latitude 30° N . The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 14 segments. In the equatorial coordinate system , the right ascension coordinates of these borders lie between 13 38.4 and 15 30.2 , and the declination coordinates are between −55.43° and −70.62°. Circinus culminates each year at 9 p.m. on 30 July. The recommended three-letter abbreviation for
4680-466: The works of Hesiod , Eudoxus and Aratus . The traditional 48 constellations, consisting of the zodiac and 36 more (now 38, following the division of Argo Navis into three constellations) are listed by Ptolemy , a Greco-Roman astronomer from Alexandria , Egypt, in his Almagest . The formation of constellations was the subject of extensive mythology , most notably in the Metamorphoses of
4752-409: The year due to night on Earth occurring at gradually different portions of its orbit around the Sun. As Earth rotates toward the east, the celestial sphere appears to rotate west, with stars circling counterclockwise around the northern pole star and clockwise around the southern pole star. Because of Earth's 23.5° axial tilt , the zodiac is distributed equally across hemispheres (along
4824-451: The years and centuries to come. The constellations have no official symbols, though those of the ecliptic may take the signs of the zodiac. Symbols for the other modern constellations, as well as older ones that still occur in modern nomenclature, have occasionally been published. The Great Rift, a series of dark patches in the Milky Way, is most visible in the southern sky. Some cultures have discerned shapes in these patches. Members of
4896-467: Was attached to the Quadrantid meteor shower), but is now divided between Boötes and Draco . A list of 88 constellations was produced for the IAU in 1922. 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
4968-498: Was finally published in 1930. Where possible, these modern constellations usually share the names of their Graeco-Roman predecessors, such as Orion, Leo, or Scorpius. The aim of this system is area-mapping, i.e. the division of the celestial sphere into contiguous fields. Out of the 88 modern constellations, 36 lie predominantly in the northern sky, and the other 52 predominantly in the southern. The boundaries developed by Delporte used data that originated back to epoch B1875.0 , which
5040-688: Was preserved as part of the Dunhuang Manuscripts . Native Chinese astronomy flourished during the Song dynasty , and during the Yuan dynasty became increasingly influenced by medieval Islamic astronomy (see Treatise on Astrology of the Kaiyuan Era ). As maps were prepared during this period on more scientific lines, they were considered as more reliable. A well-known map from the Song period
5112-423: Was recorded by Chinese observers. Two novae have been observed more recently, in the 20th century. The Milky Way runs through the constellation, featuring prominent objects such as the open cluster NGC 5823 and the planetary nebula NGC 5315 . Circinus hosts a notable spiral galaxy , the Circinus Galaxy , discovered in 1977; it is the closest Seyfert galaxy to the Milky Way. The Alpha Circinids (ACI),
5184-406: Was when Benjamin A. Gould first made his proposal to designate boundaries for the celestial sphere, a suggestion on which Delporte based his work. The consequence of this early date is that because of the precession of the equinoxes , the borders on a modern star map, such as epoch J2000 , are already somewhat skewed and no longer perfectly vertical or horizontal. This effect will increase over
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