Musca (Latin: fly) is a small constellation in the deep southern sky. It was one of twelve constellations created by Petrus Plancius. It was also known as Apis (Latin: bee) for two hundred years. Musca remains below the horizon for most Northern Hemisphere observers.
Musca is bordered by Crux to the north, Carina to the west, Chamaeleon to the south, Apus and Circinus to the east and Centaurus to the northeast. Covering 138 square degrees and 0.335% of the night sky, it ranks 77th of the 88 constellations in size. In the equatorial coordinate system, the right ascension coordinates of the constellation lie between 11h 19.3m and 13h 51.1m, while the declination coordinates are between −64.64° and −75.68°. The whole constellation is visible to observers south of latitude 14°N.
Musca Borealis crawls across Chart XI from the Uranographia of Johann Bode (1801)
[http://www.ianridpath.com/startales/muscaborealis.htm]
Musca was one of the twelve constellations established by the Dutch astronomer Petrus Plancius from the observations of the southern sky by the Dutch explorers Pieter Dirkszoon Keyser and Frederick de Houtman, who had sailed on the first Dutch trading expedition, known as the Eerste Schipvaart, to the East Indies. 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 (14 in) diameter celestial globe published in 1598 in Amsterdam by Plancius with Jodocus Hondius, though was unnamed. The first depiction of this constellation in a celestial atlas was in the German cartographer Johann Bayer’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 depicts it as providing nourishment for the nearby constellation Chamaeleon- its tongue trying to catch the insect.
The French explorer and astronomer Nicolas Louis de Lacaille called it la Mouche on the 1756 version of his planisphere of the southern skies. Jean Fortin retained the French name in 1776 for his Atlas Céleste, while Lacaille Latinized 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 composed of a few stars in 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 of Mato Grosso state in Brazil called Alpha and Beta Muscae (along with Beta and Kappa Crucis) ‘Kutsu anangagï,’ ‘Ornate Hawk-Eagle’s double flutes.’
The Wardaman people 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 Gamma and Delta represented two armbands. In Central Australia, the Arrernte and Luritja people living in on a mission in Hermannsburg 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, Alpha Pavonis, and Alpha and Beta Gruis were all claimed by the Arrernte.
[http://www.davidmalin.com/fujii/source/Mus.html]
[http://keywordsuggest.org/gallery/557491.html]
Many of the constellation’s brighter stars are members of the Scorpius- Centaurus Association, a loose group of hot blue-white stars that appear to share a common origin and motion across the Milky Way. The pattern of the brightest stars resembles that of Ursa Minor, in that the stars form a pattern reminiscent of a bowl with a handle.
Lying south-southeast of Acrux in neighboring Crux is Alpha Muscae. It is the brightest star in the constellation with an apparent magnitude of 2.7. Lying around 310 light-years away, it is a blue-white star of spectral type B2IV-V that is around 4520 times as luminous and 8 times as massive as the Sun. The star is a Beta Cephei variable 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 type of variable. It is around five times as massive as our Sun.
Beta Muscae is a binary star 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.
Eta Muscae 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.
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 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 is 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.
This image from the NASA/ESA Hubble Space Telescope shows a visible light view of the outer dust around the young star HD 100546. The position of the newly discovered protoplanet is marked with an orange spot. The inner part of this picture is dominated by artifacts from the brilliant central star, which has been digitally subtracted, and the black blobs are not real.
HD 100546, also known as KR Muscae, is a star 320 LY from Earth. It is orbited by an approximately 20 MJ 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 one planet. The star is surrounded by a circumstellar 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 of around 47 AU, and it is also the largest exoplanet discovered with a size around 6.9 RJ.
Estimated to be around 10 million years old, it is at the upper age limit of the class of stars it belongs to- Herbig Ae/Be stars, and also the nearest example to the Solar System.
Evidence for a planetary companion to HD 100546 was gathered using the UVES echelle spectrograph at the VLT in Chile. Coronagraphic optical observations with the Hubble Space Telescope show complex spiral patterns in the circumstellar disk of HD 100546. The causes of these structures remain uncertain. The disk colors are similar to those derived for Kuiper Belt objects, suggesting that the same weathering processes are at work in HD 100546. The disk is fairly flat, consistent with an advanced evolutionary state.
[https://en.wikipedia.org/wiki/HD_100546]
A bright +11.5 solitary white dwarf and one of the best for southern skywatchers. Located 15 light years distant in the constellation Musca. Well-placed during evening hours. Start with the easy naked-eye star Lambda (λ) Muscae (+3.7 magnitude) and wend your way north to LP 145-141.
[http://www.skyandtelescope.com/observing/hunting-the-smallest-stars-white-dwarfs/]
LP 145-141 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.)
LP 145-141 may be a member of the Wolf 219 moving group, which has seven possible members. These stars share a similar motion through space, which may indicate a common origin. This group has an estimated space velocity of 160 km/s and is following a highly eccentric orbit through the Milky Way galaxy.
White dwarfs are no longer generating energy at their cores through nuclear fusion, and instead are steadily radiating away their remaining heat. LP 145-141 has a DQ spectral classification, indicating that it is a rare type of white dwarf which displays evidence of atomic or molecular carbon in its spectrum.
LP 145-141 has only 75% of the Sun’s mass, but it is the remnant of a massive main-sequence star that had an estimated 4.4 solar masses. While it was on the main sequence, it probably was a spectral class B star (in the range B4-B9). Most of the star’s original mass was shed after it passed into the asymptotic giant branch stage, just prior to becoming a white dwarf.
Its proximity, mass and temperature have led to it being considered a good candidate to look for Jupiter-like planets. Its relatively large mass and high temperature mean that the system is relatively short-lived and hence of more recent origin. A survey with the Hubble Space Telescope revealed no visible orbiting companions, at least down to the limit of detection.
[https://en.wikipedia.org/wiki/LP_145-141]
The artist’s impression of HD 111232b
[http://www.robotplanet.dk/astro/exoplanets.php?p=HD_111232_b]
HD 111232 is a yellow main-sequence star in the constellation of Musca. It has magnitude 7.61 and has the distance of 95 light years away from Earth. It has mass 78% that of the Sun. Since 2003, it has been known to have a planet.
HD 111232 b is an extrasolar planet that orbits almost 2 AU with a mass of at least 6.8 times that of Jupiter. This planet was discovered in the La Silla Observatory by Michel Mayor using the CORALIE spectrograph on 30 June 2003, along with six other planets.
[https://en.wikipedia.org/wiki/HD_111232]
[https://en.wikipedia.org/wiki/HD_111232_b]
G299.2-2.9 is a supernova remnant in the constellation Musca:
G299.2-2.9: Exploded star blooms like a cosmic flower
Chandra observations of the supernova remnant G299.2-2.9 reveal important information about this object. The shape of the supernova remnant today gives clues about the explosion that created it about 4,500 years ago. G299.2-2.9 belongs to the class of supernovas known as Type Ias. Astronomers are trying to determine the exact mechanisms that produce these particular explosions.
Because the debris fields of exploded stars, known as supernova remnants, are very hot, energetic, and glow brightly in X-ray light, NASA’s Chandra X-ray Observatory has proven to be a valuable tool in studying them. The supernova remnant called G299.2-2.9 (or G299 for short) is located within our Milky Way galaxy, but Chandra’s new image of it is reminiscent of a beautiful flower here on Earth.
G299 was left over by a particular class of supernovas called Type Ia. Astronomers think that a Type Ia supernova is a thermonuclear explosion- involving the fusion of elements and release of vast amounts of energy- of a white dwarf star in a tight orbit with a companion star. If the white dwarf’s partner is a typical, Sun-like star, the white dwarf can become unstable and explode as it draws material from its companion. Alternatively, the white dwarf is in orbit with another white dwarf, the two may merge and can trigger an explosion.
Regardless of their triggering mechanism, Type Ia supernovas have long been known to be uniform in their extreme brightness, usually outshining the entire galaxy where they are found. This is important because scientists use these objects as cosmic mileposts, allowing them to accurately measure the distances of galaxies billions of light years away, and to determine the rate of expansion of the Universe.
Traditional theoretical models of Type Ia supernovas generally predict that these explosions would be symmetric, creating a near perfect sphere as they expand. These models have been supported by results showing that remnants of Type Ia supernovas are more symmetric than remnants of supernovas involving the collapse of massive stars.
However, astronomers are discovering that some Type Ia supernova explosions may not be as symmetric as previously thought. G299 could be an example of such an ‘unusual’ Type Ia supernova. Using a long observation from Chandra, researchers discovered the shell of debris from the exploded star is expanding differently in various directions.
In this new Chandra image, red, green, and blue represent low, medium, and high-energy X-rays, respectively, detected by the telescope. The medium energy X-rays include emission from iron and the high-energy X-rays include emission from silicon and sulfur. The X-ray data have been combined with infrared data from ground-based 2MASS survey that shows the stars in the field of view.
By performing a detailed analysis of the X-rays, researchers found several clear examples of asymmetry in G299. For example, the ratio between the amounts of iron and silicon in the part of the remnant just above the center is larger than in the part of the remnant just below the center. This difference can be seen in the greener color of the upper region compared to the bluer color of the lower region. Also, there is a strongly elongated portion of the remnant extending to the right. In this region, the relative amount of iron to silicon is similar to that found in the southern region of the remnant.
The patterns seen in the Chandra data suggest that a very lopsided explosion may have produced this Type Ia supernova. It might also be that the remnant has been expanding into an environment where the medium it encountered was uneven. Regardless of the ultimate explanation, observations of G299 and others like it are showing astronomers just how varied such beautiful cosmic flowers can be.
[http://chandra.harvard.edu/photo/2015/g299/]
NGC 4833 is one of the over 150 globular clusters known to reside within the Milky Way
NGC 4833 (also known as Caldwell 105) is a globular cluster discovered by Abbe Lacaille during his 1751-1752 journey to South Africa, and catalogued in 1755. It was subsequently observed and catalogued by James Dunlop and Sir John Herschel whose instruments could resolve it into individual stars.
The globular cluster is situated in the very southerly constellation Musca at a distance of 21,200 light years from Earth. It is partially obscured by a dusty region of the galactic plane. After corrections for the reddening by dust, evidence was obtained that it is in the order of 2 billion years older than globular clusters M5 or M92.
[https://en.wikipedia.org/wiki/NGC_4833]
Located 2.4° east of Eta Muscae is the magnitude-12.9 Engraved Hourglass Nebula (MyCn 18), which lies about 8,000 light-years distant from Earth:
The Hourglass Nebula
This is an image of MyCn18, a young planetary nebula located about 8,000 light-years away, taken with the Wide Field and Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope (HST).
This Hubble image reveals the true shape of MyCn18 to be an hourglass with an intricate pattern of ‘etchings’ in its walls. This picture has been composed from three separate images taken in the light of ionized nitrogen (represented by red), hydrogen (green), and doubly-ionized oxygen (blue).
The results are of great interest because they shed new light on the poorly understood ejection of stellar matter which accompanies the slow death of Sun-like stars. In previous ground-based images, MyCn18 appears to be a pair of large outer rings with a smaller central one, but the fine details cannot be seen.
[https://www.spacetelescope.org/images/opo9607a/]
Located on the border with Circinus is the unusual planetary nebula NGC 5189, 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:
NGC 5189: An Unusually Complex Planetary Nebula
Why is this nebula so complex? When a star like our Sun is dying, it will cast off its outer layers, usually into a simple overall shape. Sometimes this shape is a sphere, sometimes a double lobe, and sometimes a ring or a helix. In the case of planetary nebula NGC 5189, however, no such simple structure has emerged. To help find out why, the Earth-orbiting Hubble Space Telescope recently observed NGC 5189 in great detail. Previous findings indicated the existence of multiple epochs of material outflow, including a recent one that created a bright but distorted torus running horizontally across image center. Results appear consistent with a hypothesis that the dying star is part of a binary star system with a precessing symmetry axis. Given this new data, though, research is sure to continue. NGC 5189 spans about three light years and lies about 3,000 light years away toward the southern constellation of the Fly (Musca).
[http://apod.nasa.gov/apod/ap121219.html]
The globular cluster NGC 4372 near Gamma Muscae is fainter than NGC 4833 and likewise partially obscured by dust, but spans more arc minutes. It is 18,900 light-years away from Earth and 23,000 light-years distant from the center of the Milky Way. Its extremely low metallicity indicates it is very old- one of the oldest clusters in the Milky Way. Extending south from it is the Dark Doodad Nebula, resembling a dark L-shaped river through a bright field of stars:
NGC 4372 and the Dark Doodad
The delightful Dark Doodad Nebula drifts through southern skies, a tantalizing target for binoculars in the constellation Musca, The Fly. The dusty cosmic cloud is seen against rich starfields just south of the prominent Coalsack Nebula and the Southern Cross. Stretching for about 3 degrees across this scene the Dark Doodad is punctuated at its southern tip (lower left) by globular star cluster NGC 4372. Of course NGC 4372 roams the halo of our Milky Way Galaxy, a background object some 20,000 light-years away and only by chance along our line-of-sight to the Dark Doodad. The Dark Doodad’s well defined silhouette belongs to the Musca molecular cloud, but its better known alliterative moniker was first coined by astro-imager and writer Dennis di Cicco in 1986 while observing Comet Halley from the Australian outback. The Dark Doodad is around 700 light-years distant and over 30 light-years long.
[http://apod.nasa.gov/apod/ap150910.html]
Another dark nebula in the constellation is BHR 71:
BHR 71: Stars, Clouds, and Jets
What is happening to molecular cloud BHR 71? Quite possible, a binary star system is forming inside. Most stars in our Galaxy are part of binary star systems, but few have ever been seen in formation. Recent observations of dust-darkened Bok Globule BHR 71, however, show evidence for two young stars forming deep in the cloud, likely close enough to form a binary. Isolated BHR 71 spans about one light year and lies only about 600 light years away in the southern sky. The brighter embedded star- not visible here- is about 10 times as bright as the Sun and drives the jet that swept out the empty lane. The above four-color image was taken with a Very Large Telescope in Chile.
[https://apod.nasa.gov/apod/ap030127.html]
[https://en.wikipedia.org/wiki/Musca]
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