Musca () is a small

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

in the deep southern sky. It was one of 12 constellations created by

Petrus Plancius Petrus Plancius (; 1552 – 15 May 1622) was a Dutch-Flemish astronomer, cartographer and clergyman. He was born as Pieter Platevoet in Dranouter, now in Heuvelland, West Flanders. He studied theology in Germany and England. At the age of 24 he ...

from the observations of

Pieter Dirkszoon Keyser Pieter Dirkszoon Keyser (occasionally Petrus Theodorus; – 11 September 1596) was a Dutch navigator and celestial cartographer who mapped several constellations on the southern celestial hemisphere. Voyages and star observation Little is ...

and

Frederick de Houtman Frederick de Houtman ( – 21 October 1627) was a Dutch explorer, navigator, and colonial governor who sailed on the first Dutch expedition to the East Indies from 1595 until 1597, during which time he made observations of the southern cel ...

, and it first appeared on a

celestial globe Celestial globes show the apparent positions of the stars in the sky. They omit the Sun, Moon, and planets because the positions of these bodies vary relative to those of the stars, but the ecliptic, along which the Sun moves, is indicated. The ...

in diameter published in 1597 (or 1598) in Amsterdam by Plancius and

Jodocus Hondius Jodocus Hondius (Latinized version of his Dutch language, Dutch name: ''Joost de Hondt'') (17 October 1563 – 12 February 1612) was a Flemish people, Flemish and Dutch engraving, engraver and cartographer. He is sometimes called Jodocus Hon ...

. The first depiction of this constellation in a

celestial atlas Celestial cartography, uranography, astrography or star cartography is the aspect of astronomy and branch of cartography concerned with mapping stars, galaxies, and other astronomical objects on the celestial sphere. Measuring the position ...

was in

Johann Bayer Johann Bayer (1572 – 7 March 1625) was a German lawyer and uranographer (celestial cartographer). He was born in Rain, Lower Bavaria, in 1572. At twenty, in 1592 he began his study of philosophy and law at the University of Ingolstadt, a ...

's ''

Uranometria ''Uranometria'' is a star atlas produced by Johann Bayer. It was published in Augsburg in 1603 by Christoph Mangle (''Christophorus Mangus'') under the full title ''Uranometria: omnium asterismorum continens schemata, nova methodo delineata, ae ...

'' of 1603. It was also known as Apis () for 200 years. Musca remains below the horizon for most Northern Hemisphere observers. Many of the constellation's brighter stars are members of the

Scorpius–Centaurus association The Scorpius–Centaurus association (sometimes called Sco–Cen or Sco OB2) is the nearest OB association to the Sun. This stellar association is composed of three subgroups (Upper Scorpius, Upper Centaurus–Lupus, and Lower Centaurus–Crux) ...

, a loose group of hot blue-white stars that appears to share a common origin and motion across the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

. These include

Alpha Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', or ell, άλφα, álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , whic ...

Beta Beta (, ; uppercase , lowercase , or cursive ; grc, βῆτα, bē̂ta or ell, βήτα, víta) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Modern Greek, it represents the voiced labiod ...

Gamma Gamma (uppercase , lowercase ; ''gámma'') is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter re ...

, Zeta² and (probably)

Eta Muscae Eta Muscae is a multiple star system in the southern constellation of Musca. It is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude of 4.79. The system is located around 406 light ...

, as well as

HD 100546 HD 100546, is a star 316.4 light-years from Earth. It is orbited by an approximately exoplanet at 6.5 AU, although further examination of the disk profile indicate it might be a more massive object such as a brown dwarf or more than ...

, a blue-white

Herbig Ae/Be star A Herbig Ae/Be star (HAeBe) is a pre-main-sequence star – a young () star of spectral types A or B. These stars are still embedded in gas-dust envelopes and are sometimes accompanied by circumstellar disks. Hydrogen and calcium emission lines a ...

that is surrounded by a complex

debris disk A debris disk (American English), or debris disc (Commonwealth English), is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris dis ...

containing a large

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

brown dwarf Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...

and possible protoplanet. Two further star systems have been found to have planets. The constellation also contains two

cepheid variables A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid vari ...

visible to the naked eye.

Theta Muscae Theta Muscae (θ Muscae) is a multiple star system in the southern constellation Musca ("the Fly") with an apparent magnitude of 5.5. It is the second-brightest Wolf–Rayet star in the sky, although much of the visual brightness co ...

is a triple star system, the brightest member of which is a

Wolf–Rayet star Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface ...

History

Musca was one of the 12 constellations established by the Dutch astronomer Petrus Plancius from the observations of the southern sky by the Dutch explorers

and

, who had sailed on the first Dutch trading expedition, known as the ''

Eerste Schipvaart The First Dutch Expedition to East Indies (Dutch: ''Eerste Schipvaart'') was an expedition that took place from 1595 to 1597. It was instrumental in opening up the Indonesian spice trade to the merchants that eventually formed the Dutch E ...

'', to the

East Indies The East Indies (or simply the Indies), is a term used in historical narratives of the Age of Discovery. The Indies refers to various lands in the East or the Eastern hemisphere, particularly the islands and mainlands found in and around t ...

. De Houtman included it in his southern star catalogue in 1598 under the Dutch name ''De Vlieghe'', "The Fly". They assigned four stars to the constellation, with a star that would be later designated as Beta Muscae marking the head, Gamma the body, and Alpha and Delta the left and right wings, respectively. It first appeared on a 35-cm-diameter (14-in)

published in 1598 in Amsterdam by Plancius with Jodocus Hondius, though was unnamed. The first depiction of this constellation in a

was in the German cartographer

's ''Uranometria'' of 1603, though Bayer termed it Apis— "the Bee", a name by which it was known for the next two centuries. A 1603 celestial globe by

Willem Blaeu Willem Janszoon Blaeu (; 157121 October 1638), also abbreviated to Willem Jansz. Blaeu, was a Dutch cartographer, atlas maker and publisher. Along with his son Johannes Blaeu, Willem is considered one of the notable figures of the Netherlandis ...

depicts it as providing nourishment for the nearby constellation

Chamaeleon Chamaeleon () is a small constellation in the deep southern sky. It is named after the chameleon, a kind of lizard. It was first defined in the 16th century. History Chamaeleon was one of twelve constellations created by Petrus Plancius fro ...

—its tongue trying to catch the insect. The French explorer and astronomer

Nicolas Louis de Lacaille Abbé Nicolas-Louis de Lacaille (; 15 March 171321 March 1762), formerly sometimes spelled de la Caille, was a French astronomer and geodesist who named 14 out of the 88 constellations. From 1750 to 1754, he studied the sky at the Cape of Good ...

called it ''la Mouche'' on the 1756 version of his

planisphere In astronomy, a planisphere () is a star chart analog computing instrument in the form of two adjustable disks that rotate on a common pivot. It can be adjusted to display the visible stars for any time and date. It is an instrument to assist ...

of the southern skies. Jean Fortin retained the French name in 1776 for his ''Atlas Céleste'', while Lacaille

latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

ised the name for his revised ''Coelum Australe Stelliferum'' in 1763. Lacaille renamed it to ''Musca Australis'', the Southern Fly—''Australis'', since it counterparted the now discarded constellation of

Musca Borealis Musca Borealis (Latin for ''northern fly'') was a constellation, now discarded, located between the constellations of Aries and Perseus. It was originally called Apes (plural of Apis, Latin for bee) by Petrus Plancius when he created it in 1612. ...

composed of a few stars in

Aries Aries may refer to: *Aries (astrology), an astrological sign *Aries (constellation), a constellation of stars in the zodiac Arts, entertainment and media * ''Aries'' (album), by Luis Miguel, 1993 * ''Aries'' (EP), by Alice Chater, 2020 * "Aries" ...

, and to avoid confusion with Apus. Today, the name is simply Musca. It is the only official constellation depicting an insect. The

Kalapalo people The Kalapalo are an indigenous people of Brazil. They are one of seventeen tribal groups who inhabit the Xingu National Park in the Upper Xingu River region of the state of Mato Grosso. They speak the Amonap language, a Cariban language, and ...

Mato Grosso Mato Grosso ( – lit. "Thick Bush") is one of the states of Brazil, the third largest by area, located in the Central-West region. The state has 1.66% of the Brazilian population and is responsible for 1.9% of the Brazilian GDP. Neighboring ...

state in Brazil called Alpha and Beta Muscae (along with

and Kappa Crucis) ''Kutsu anangagï'' "

Ornate Hawk-Eagle The ornate hawk-eagle (''Spizaetus ornatus'') is a fairly large bird of prey from the tropical Americas. Formerly, some authorities referred to this species as the crested hawk-eagle, a name that may cause some confusion as it is more commonly us ...

's double flutes". The

Wardaman people The Wardaman people are a small group of Aboriginal Australians living about South-West of Katherine, on Menngen Aboriginal Land Trust in the Northern Territory of Australia. Language Wardaman is a non Pama-Nyungan language. Though close to ...

of the Northern Territory in Australia perceived the main stars of Musca as a ceremonial boomerang, part of the Central Arena—a sacred area surrounding the constellation Crux that depicts the lightning creation beings and where they teach Wardaman customs; Alpha and Beta also signified a ceremonial headband, while

and

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), a letter of the Greek alphabet * River delta, at a river mouth * D (NATO phonetic alphabet: "Delta") * Delta Air Lines, US * Delta variant of SARS-CoV-2 that causes COVID-19 Delta may also re ...

represented two armbands. In central Australia, the

Arrernte Arrernte (also spelt Aranda, etc.) is a descriptor related to a group of Aboriginal Australian peoples from Central Australia. It may refer to: * Arrernte (area), land controlled by the Arrernte Council (?) * Arrernte people, Aboriginal Australi ...

and

Luritja The Luritja or Loritja people, also known as Kukatja or Kukatja-Luritja, are an Aboriginal Australian people of the Northern Territory. Their traditional lands are immediately west of the Derwent River, that forms a frontier with the Arrernte p ...

peoples living in on a mission in

Hermannsburg Hermannsburg is a village and a former municipality in the Celle district, in Lower Saxony, Germany. Since 1 January 2015 it is part of the municipality Südheide. It has been a state-recognised resort town since 1971. It is situated on the river ...

viewed the sky as divided between them, east of the Milky Way representing Arrernte camps and west denoting Luritja camps. The stars of Musca, along with

Fomalhaut Fomalhaut is the brightest star in the southern constellation of Piscis Austrinus, the "Southern Fish", and one of the brightest stars in the night sky. It has the Bayer designation Alpha Piscis Austrini, which is Latinized from � ...

Alpha Pavonis Alpha Pavonis (α Pavonis, abbreviated Alpha Pav, α Pav), formally named Peacock , is a binary star in the southern constellation of Pavo, near the border with the constellation Telescopium. Nomenclature ''α Pavonis'' ( Latinised t ...

, and

and

Beta Gruis Beta Gruis (β Gruis, abbreviated Beta Gru, β Gru), formally named Tiaki , is the second brightest star in the southern constellation of Grus. It was once considered the rear star in the tail of the constellation of the (Southern) Fi ...

, were all claimed by the Arrernte.

Characteristics

Musca is bordered by

Crux Crux () is a constellation of the southern sky that is centred on four bright stars in a cross-shaped asterism commonly known as the Southern Cross. It lies on the southern end of the Milky Way's visible band. The name ''Crux'' is Latin for c ...

to the north,

Carina Carina may refer to: Places Australia * Carina, Queensland, a suburb in Brisbane * Carina Heights, Queensland, a suburb in Brisbane * Carina, Victoria, a locality in Mildura Serbia * Carina, Osečina, a village in the Kolubara District Pe ...

to the west,

to the south,

Apus Apus is a small constellation in the Southern Celestial Hemisphere, southern sky. It represents a bird-of-paradise, and its name means "without feet" in Greek language, Greek because the bird-of-paradise was once wrongly believed to lack feet. ...

and

Circinus 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 (drawing tool), compass, referring to the Technical drawing, drafting tool used ...

to the east, and

Centaurus Centaurus is a bright constellation in the southern sky. One of the 88 modern constellations by area, largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one o ...

to the northeast. Covering 138 square degrees and 0.335% of the night sky, it ranks 77th of the 88 constellations in size. The three-letter abbreviation for the constellation, as adopted by the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

in 1922, is "Mus". The official constellation boundaries, as set by Belgian astronomer

Eugène Delporte Eugene is a common male given name that comes from the Greek εὐγενής (''eugenēs''), "noble", literally "well-born", from εὖ (''eu''), "well" and γένος (''genos''), "race, stock, kin".equatorial coordinate system The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects. It may be implemented in spherical or rectangular coordinates, both defined by an origin at the centre of Earth, a fund ...

, the

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the earth. When paired w ...

coordinates of these borders lie between and , while the

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the ...

coordinates are between −64.64° and −75.68°. The whole constellation is visible to observers south of latitude 14°N.

Features

Stars

Lacaille charted and designated 10 stars with the

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. ...

s Alpha to Kappa in 1756. He catalogued stars that became

Lambda Lambda (}, ''lám(b)da'') is the 11th letter of the Greek alphabet, representing the voiced alveolar lateral approximant . In the system of Greek numerals, lambda has a value of 30. Lambda is derived from the Phoenician Lamed . Lambda gave rise ...

and Mu, but did not designate them as he considered them ''informes'' as they lay outside the asterism proper. Baily considered them part of Musca, and Gould gave them their Bayer designations.

Francis Baily Francis Baily (28 April 177430 August 1844) was an English astronomer. He is most famous for his observations of "Baily's beads" during a total eclipse of the Sun. Baily was also a major figure in the early history of the Royal Astronomical S ...

also dropped Kappa, which he felt was too faint to warrant a name, and designated two adjacent stars as Zeta¹ and Zeta². These last two stars are 1° apart, quite far to be sharing a Bayer designation. Lacaille had originally labelled the fainter one as Zeta, while Baily presupposed he had meant to label the brighter one. Reluctant to remove Lacaille's designation, he gave them both the Zeta designation. Altogether there are 62 stars brighter than magnitude 6.5 in the constellation. The pattern of the brightest stars resembles that of

Ursa Minor Ursa Minor (Latin: 'Lesser Bear', contrasting with Ursa Major), also known as the Little Bear, is a constellation located in the far northern sky. As with the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, h ...

, in that the stars form a pattern reminiscent of a bowl with a handle. Lying south-southeast of

Acrux Acrux is the brightest star in the southern constellation of Crux. It has the Bayer designation α Crucis, which is Latinised to Alpha Crucis and abbreviated Alpha Cru or α Cru. With a combined visual magnitude of +0.76, it is the ...

in neighbouring Crux is

Alpha Muscae Alpha Muscae, Latinized from α Muscae, is a star in the southern circumpolar constellation of Musca. With an apparent visual magnitude of +2.7, it is the brightest star in the constellation. The distance to this star has been determine ...

. It is the brightest star in the constellation with an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

of 2.7. Lying around 310

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away, it is a blue-white star of

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

B2IV-V that is around 4520 times as luminous and 8 times as massive as the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. The star is a

Beta Cephei variable Beta Cephei variables, also known as Beta Canis Majoris stars, are variable stars that exhibit small rapid variations in their brightness due to pulsations of the stars' surfaces, thought due to the unusual properties of iron at temperatures of 200, ...

with about 4.7 times the Sun's diameter, and pulsates every 2.2 hours, varying by 1% in brightness. A nearby star of magnitude 13 may or may not be a companion star. Marking the fly's tail is Gamma Muscae, a blue-white star of spectral type B5V that varies between magnitudes 3.84 and 3.86 over a period of 2.7 days. It is a variable of a different type, classed as a

slowly pulsating B star A slowly pulsating B-type star (SPB), formerly known as a 53 Persei variable, is a type of pulsating variable star. They may also be termed a long-period pulsating B star (LPB). As the name implies, they are main-sequence stars of spectral type B2 ...

, a type of variable. It is around five times as massive as the Sun. Beta Muscae is a

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

system around 341 light-years distant that is composed of two blue-white main-sequence stars of spectral types B2V and B3V that orbit each other every 194 years. They are eight and six times as massive as the Sun, respectively, and have about 3.5 times its diameter. Zeta² Muscae is a white main sequence star of spectral type A5V around 330 light-years distant from Earth. It is part of a triple star system with faint companions at 0.5 and 32.4 arc seconds distance.

is a multiple star system, the two main components forming an eclipsing binary that has a combined spectral type of B8V and magnitude of 4.77 that dips by 0.05 magnitude every 2.39 days. Alpha, Beta, Gamma,

HD 103079 HD 103079 is a class B4V (blue main-sequence) star in the constellation Musca (constellation), Musca. Its apparent magnitude is 4.89 and it is approximately 362 light years away from Earth based on parallax. It is a member of the Lower Ce ...

, Zeta² and (likely) Eta are all members of the Lower Centaurus Crux subgroup of the

, a group of predominantly hot blue-white stars that share a common origin and

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

across the galaxy. Delta and Epsilon mark the fly's left wing and right wing, respectively. With an apparent magnitude of 3.62, Delta is an orange giant of spectral type K2III located around 91 light-years away. Epsilon Muscae is a

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

of spectral type M5III and semiregular variable that ranges between magnitudes 3.99 and 4.31 over approximately 40 days. It has expanded to 130 times the Sun's diameter and 1800 to 2300 its luminosity. It was a star originally 1.5 to 2 times as massive as our Sun. Although of a similar distance—around 302 light-years—to the stars of the Lower Centaurus Crux subgroup, it is moving much faster at around 100 km/s and does not share a common origin. To the northwest lies Mu Muscae, an orange giant of spectral type K4III that varies between apparent magnitude 4.71 and 4.76, and has been classified as a slow, irregular variable. Near Mu is Lambda Muscae, the third-brightest star in the constellation and a white main-sequence star of spectral type A7V around 128 light-years distant from Earth. Located near Alpha is

R Muscae R Muscae is a yellow-white hued variable star in the southern constellation of Musca. It has a nominal apparent visual magnitude of 6.31, which is near the lower limit of visibility to the naked eye. The distance to this star, as determi ...

, a

classical Cepheid variable Classical Cepheids (also known as Population I Cepheids, Type I Cepheids, or Delta Cepheid variables) are a type of Cepheid variable star. They are population I variable stars that exhibit regular radial pulsations with periods of a few days to a ...

ranging from apparent magnitude 5.93 to 6.73 over 7.5 days. It is a yellow-white supergiant ranging between spectral types F7Ib and G2Ib, located around 2037 light-years away. S Muscae is likewise a classical Cepheid, a yellow-white supergiant ranging between spectral types F6Ib and G0Ib and magnitudes 5.89 to 6.49 over a period of 9.66 days. A luminous star around 5.9 times as massive as the Sun, it is a binary star with a blue-white main-sequence star companion likely to be of spectral type B3V to B5V with a mass of just over 5 solar masses, one of the hottest and brightest companions of a cepheid known. The two stars orbit each other every 505 days.

is a triple star system thought to be around 7,500 light-years distant. It consists of a

spectroscopic binary A binary star is a system of two star, stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separa ...

system composed of the

(spectral type: WC5 or 6) and an

O-type main-sequence star An O-type main-sequence star (O V) is a main-sequence (core hydrogen-burning) star of spectral type O and luminosity class V. These stars have between 15 and 90 times the mass of the Sun and surface temperatures between 30,000 and 50,000 K. The ...

(spectral type: O6 or O7) that orbit each other every 19 days and a

blue supergiant A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They have luminosity class I and spectral class B9 or earlier. Blue supergiants are found towards the top left of the Hertzsprung–Russell diagram, above an ...

(spectral type: O9.5/B0Iab) set about 46

milliarcseconds A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

apart from them. If the system's estimated distance from Earth is accurate, the binary stars are about 0.5

astronomical unit The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits t ...

s (AU) apart and the supergiant about 100 AU apart from them. All three are highly luminous; combined, they are likely to be over a million times as luminous as the Sun.

TU Muscae TU Muscae, also known as HD100213, is an eclipsing binary star in the constellation Musca. Its apparent magnitude ranges from 8.17 to 8.75 over around 1.4 days. Physical description TU Muscae is a remote binary star system made up of ...

is a binary star system located around 15,500 light-years away made up of two hot, luminous, blue main-sequence stars of spectral types O7.5V and O9.5V, with masses 23 and 15 times that of the Sun. The stars are so close that they are in contact with each other ( overcontact binary) and are classed as a

Beta Lyrae variable Beta Lyrae variables are a class of close binary stars. Their total brightness is variable because the two component stars orbit each other, and in this orbit one component periodically passes in front of the other one, thereby blocking its light. ...

as their light varies from Earth as they eclipse each other. The system ranges from apparent magnitude 8.17 to 8.75 over around 1.4 days. Also known as Nova Muscae 1983,

GQ Muscae GQ Muscae, also known as Nova Muscae 1983 is a nova in the constellation Musca, which was discovered by William Liller William Liller (April 1, 1927, Philadelphia – February 28, 2021) was an American astronomer, known for his resear ...

is a binary system consisting of a white dwarf and small star that is about 10% as massive as the Sun. The two orbit each other every 1.4 hours. The white dwarf accumulates material from its companion star via its

accretion disc An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is typically a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other f ...

. After a certain amount has accumulated, the star erupts, as it did in 1983, reaching a magnitude of 7.2. Discovered with a magnitude of 7.1 on 18 January 1983, it was the first nova from which X-rays were detected. The

soft X-ray transient Soft X-ray transients (SXTs), also known as X-ray novae and black hole X-ray transients, are composed of a compact object (most commonly a black hole but sometimes a neutron star) and some type of "normal", low-mass star (i.e. a star with a mass ...

GRS 1124-683 (also known as Nova Muscae 1991) is a binary object consisting of an orange main-sequence star (GU Muscae) of spectral type K3V–K4V and a

black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...

of around six solar masses. During the 1991 outburst which led to its discovery,

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

was produced through a process of

positron The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. It has an electric charge of +1 '' e'', a spin of 1/2 (the same as the electron), and the same mass as an electron. When a positron collides ...

annihilation In particle physics, annihilation is the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles, such as an electron colliding with a positron to produce two photons. The total energy a ...

GR Muscae GR Muscae, also known as 2S 1254-690 is a binary star system in the constellation Musca composed of a neutron star of between 1.2 and 1.8 times the mass of the Sun The Sun is the star at the center of the Solar System. It is a nearly ...

is an X-ray source composed of a

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...

of between 1.2 and 1.8 times the mass of our Sun and a low-mass star likely to be around the mass of the Sun in close orbit. Finally,

SY Muscae SY Muscae is a binary star system in the constellation Musca (constellation), Musca composed of a red giant and a white dwarf. Its apparent magnitude varies from 10.2 to 12.7 over a period of 624.5 days. Although the binary is a symbio ...

is a

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

star system composed of a red giant and white dwarf, where although the larger star is transferring mass to the smaller, no periodic eruption occurs nor does an accretion disc form. The star system varies in magnitude from 10.2 to 12.7 over a period of 624.5 days. V415 Muscae is a nova that had an outburst in 8 June 2022 with an apparent magnitude of +8.7. Coalsack and Dark Doodad Dark Nebulae

Three star systems have been discovered to have

exoplanets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

HD 111232 HD 111232 is a star in the southern constellation of Musca. It is too faint to be visible with the naked eye, having an apparent visual magnitude of 7.59. The distance to this star is 94.5 light years based on parallax. It is drif ...

is a yellow main-sequence star around 78% as massive as the Sun around 95 light-years distant. It has a planet ( HD 111232 b) around 6.8 times the mass of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

that has an orbital period around 1143 days.

HD 112410 HD 112410 is a star in the southern constellation of Musca (constellation), Musca. It has a yellow hue and is too dim to be readily visible to the average sight, having an apparent visual magnitude of 6.86. The distance to this star is 513 ...

is a yellow giant of spectral type G8III located around 439 light-years distant. With around 1.54 times the mass of our Sun, it is cooling and expanding along the

red-giant branch The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows the main sequence for low- to intermediate-mass sta ...

, having left the

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

after exhausting its core supply of hydrogen fuel. It has a substellar companion calculated to have a mass 9.2 times that of Jupiter and an orbital period of 124.6 days at a distance around 0.57 AU. Yet another member of the Lower Centaurus Crux subgroup,

is a young, blue-white

of spectral type B9V that has yet to settle on the main sequence—the closest of these stars to Earth around 320 light-years distant. It is surrounded by a circumstellar debris disk from a distance of 0.2 to 4 AU, and again from 13 AU out to a few hundred AU, with evidence for a protoplanet forming at a distance around 47 AU. A gap exists between 4 and 13 AU, which appears to contain a large planet around 20 times the mass of Jupiter, although further examination of the disk profile indicates it might be a more massive object such as a

or more than one planet.

LP 145-141 LP 145-141 (also LAWD 37) is a white dwarf located 15 light years from the Solar System. According to a 2009 paper, it is the fourth closest known white dwarf to the Sun (after Sirius B, Procyon B, and van Maanen's star.) History of o ...

is a white dwarf located 15 light-years distant—the fourth-closest to the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. It is considered a good candidate to look for Jupiter-like planets, on account if its proximity and mass.

Deep-sky objects

Located on the border with Circinus is the unusual

planetary nebula A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to ...

NGC 5189 NGC 5189 (Gum 47, IC 4274, nicknamed Spiral Planetary Nebula) is a planetary nebula in the constellation Musca. It was discovered by James Dunlop on 1 July 1826, who catalogued it as Δ252. For many years, well into the 1960s, it was thought to ...

, estimated to be around 1750 light-years away from Earth. Its complex structure is due to multiple ejections of material from the ageing central star, which are distorted by the presence of a likely binary companion. Located 2.4° east of Eta Muscae is the magnitude-12.9

Engraved Hourglass Nebula The Engraved Hourglass Nebula (also known as MyCn 18) is a young planetary nebula in the southern constellation Musca. It was discovered by Annie Jump Cannon and Margaret W. Mayall during their work on an extended Henry Draper Catalogue (the ...

(MyCn 18), which lies about 8000 light-years distant from Earth. To Eta's west lies IC 4191, a compact bluish planetary nebula of magnitude 10.6, thought to lie around 10,750 light-years away from Earth. West of Epsilon Muscae is

NGC 4071 NGC commonly refers to: * New General Catalogue of Nebulae and Clusters of Stars, a catalogue of deep sky objects in astronomy NGC may also refer to: Companies * NGC Corporation, name of US electric company Dynegy, Inc. from 1995 to 1998 * Nat ...

, a large, diffuse planetary nebula of magnitude 12.7 with a magnitude 12 central star, thought to lie around 4000 light-years away from Earth. The

Coalsack Nebula The Coalsack Nebula (Southern Coalsack, or simply the Coalsack) is a prominent dark nebula in the skies, being easily visible to the naked eye as a dark patch obscuring a brief section of Milky Way stars as they cross their southernmost region of ...

is a

dark nebula A dark nebula or absorption nebula is a type of interstellar cloud, particularly molecular clouds, that is so dense that it obscures the visible wavelengths of light from objects behind it, such as background stars and emission or reflection nebu ...

located mainly in neighbouring Crux that intrudes into Musca. NGC 4463 is an

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

located on its southwestern border. Around five light-years across, it is located around 3400 light-years away. The comparatively old

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

NGC 4833 __NOTOC__ NGC 4833 (also known as Caldwell 105) is a globular cluster discovered by Nicolas Louis de Lacaille, Abbe Lacaille during his 1751-1752 journey to South Africa, and catalogued in 1755. It was subsequently observed and catalogued by Jam ...

near Delta Muscae was catalogued by Lacaille in 1755. It is 21,200 light-years distant and somewhat obscured by dust clouds near the

galactic plane The galactic plane is the plane on which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms ''galactic plane'' and ''galactic poles'' usuall ...

. The globular cluster

NGC 4372 NGC 4372 (also known as Caldwell 108) is a globular cluster in the southern constellation of Musca. It is southwest of γ Muscae (Gamma Muscae) and west of the southern end of the Dark Doodad Nebula (Sandqvist 149), a 3° thin streak of black acr ...

near Gamma Muscae is fainter and likewise partially obscured by dust, but spans more

arc minute A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The n ...

s. It is 18,900 light-years away from Earth and 23,000 light-years distant from the centre of the Milky Way. Its extremely low

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

indicates it is very old—one of the oldest clusters in the Milky Way. Extending south from it is the

Dark Doodad Nebula The Dark Doodad Nebula is a dark nebula near the globular cluster NGC 4372, much closer than the centre of the galaxy and in the galactic plane, having a length of nearly three degrees of arc. Although officially unnamed, this long molecular clou ...

, resembling a dark L-shaped river through a bright field of stars. Another

in the constellation is

BHR 71 BHR 71 is a small dark nebula in the constellation of Musca which is 600 light years from the Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomica ...

Notes

References

External links

The Deep Photographic Guide to the Constellations: Musca

{{DEFAULTSORT:Musca Southern constellations Constellations listed by Petrus Plancius Dutch celestial cartography in the Age of Discovery Astronomy in the Dutch Republic 1590s in the Dutch Republic