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The Magellanic Clouds (''Magellanic system'' or ''Nubeculae Magellani'') are two irregular
dwarf Dwarf or dwarves may refer to: Common uses *Dwarf (folklore), a being from Germanic mythology and folklore * Dwarf, a person or animal with dwarfism Arts, entertainment, and media Fictional entities * Dwarf (''Dungeons & Dragons''), a humanoid ...
galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System ...
in the
southern celestial hemisphere The southern celestial hemisphere, also called the Southern Sky, is the southern half of the celestial sphere; that is, it lies south of the celestial equator. This arbitrary sphere, on which seemingly fixed stars form constellations, appear ...
.
Orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...
ing 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. ...
galaxy A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System ...
, these satellite galaxies are members of the Local Group. Because both show signs of a bar structure, they are often reclassified as
Magellanic spiral Magellanic spiral galaxies are (usually) dwarf galaxies which are classified as the type Sm (and SAm, SBm, SABm). They are galaxies with one single spiral arm, and are named after their prototype, the Large Magellanic Cloud, an SBm galaxy. They ca ...
galaxies. The two galaxies are: *
Large Magellanic Cloud The Large Magellanic Cloud (LMC), or Nubecula Major, is a satellite galaxy of the Milky Way. At a distance of around 50  kiloparsecs (≈160,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the ...
(LMC), approximately 163,000
light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distance, astronomical distances and is equivalent to about 9.46 Orders of magnitude (numbers)#1012, trillion kilometers (), or 5.88  ...
s away *
Small Magellanic Cloud The Small Magellanic Cloud (SMC), or Nubecula Minor, is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophotal diameter of about , and contains several hundred million stars. It has a total mass of ...
(SMC), approximately 206,000 light years away Magellanic clouds are visible to the unaided eye in the Southern Hemisphere but they cannot be observed from the most northern latitudes.


History

The Magellanic Clouds have been known since ancient times to indigenous peoples across South America and Africa, and from the first millennium in
Western Asia Western Asia, West Asia, or Southwest Asia, is the westernmost subregion of the larger geographical region of Asia, as defined by some academics, UN bodies and other institutions. It is almost entirely a part of the Middle East, and includes A ...
. The first preserved mention of the Large Magellanic Cloud is believed to be in
petroglyph A petroglyph is an image created by removing part of a rock surface by incising, picking, carving, or abrading, as a form of rock art. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions ...
s and rock drawings found in
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...
. They may be the objects mentioned by the
polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a substantial number of subjects, known to draw on complex bodies of knowledge to solve specific pro ...
Ibn Qutaybah (d. 889 CE), in his book on ''Al-Anwā̵’'' (the stations of the Moon in
pre-Islamic Arabia Pre-Islamic Arabia ( ar, شبه الجزيرة العربية قبل الإسلام) refers to the Arabian Peninsula before the emergence of Islam in 610 CE. Some of the settled communities developed into distinctive civilizations. Informatio ...
n culture):

"وأسفل من سهيل قدما سهيل . وفى مجرى قدمى سهيل، من خلفهما كواكب زهر كبار، لا ترى بالعراق، يسميها أهل تهامة الأعبار

"And below

Canopus Canopus is the brightest star in the southern constellation of Carina and the second-brightest star in the night sky. It is also designated α Carinae, which is Latinised to Alpha Carinae. With a visual apparent magnitude ...
, there are the feet of Canopus, and on their extension, behind them bright big stars, not seen in
Iraq Iraq,; ku, عێراق, translit=Êraq officially the Republic of Iraq, '; ku, کۆماری عێراق, translit=Komarî Êraq is a country in Western Asia. It is bordered by Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq ...
, the people of
Tihama Tihamah or Tihama ( ar, تِهَامَةُ ') refers to the Red Sea coastal plain of the Arabian Peninsula from the Gulf of Aqaba to the Bab el Mandeb. Etymology Tihāmat is the Proto-Semitic language's term for 'sea'. Tiamat (or Tehom, in m ...
call them ''al-a‘bār''."

Later Al Sufi, a professional astronomer, in 964 CE, in his ''
Book of Fixed Stars The ''Book of Fixed Stars'' ( ar, كتاب صور الكواكب ', literally ''The Book of the Shapes of Stars'') is an astronomical text written by Abd al-Rahman al-Sufi (Azophi) around 964. Following the translation movement in the 9th centu ...
'', mentioned the same quote, but with a different spelling. Under
Argo Navis Argo Navis (the Ship Argo), or simply Argo, is one of the 48 Ptolemy's constellations, now a grouping of three IAU constellations. It is formerly a single large constellation in the southern sky. The genitive is "Argus Navis", abbreviated "Arg". ...
, he quoted that "unnamed others have claimed that beneath
Canopus Canopus is the brightest star in the southern constellation of Carina and the second-brightest star in the night sky. It is also designated α Carinae, which is Latinised to Alpha Carinae. With a visual apparent magnitude ...
there are two stars known as the 'feet of Canopus', and beneath those there are bright white stars that are unseen in
Iraq Iraq,; ku, عێراق, translit=Êraq officially the Republic of Iraq, '; ku, کۆماری عێراق, translit=Komarî Êraq is a country in Western Asia. It is bordered by Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq ...
nor
Najd Najd ( ar, نَجْدٌ, ), or the Nejd, forms the geographic center of Saudi Arabia, accounting for about a third of the country's modern population and, since the Emirate of Diriyah, acting as the base for all unification campaigns by the ...
, and that the inhabitants of
Tihama Tihamah or Tihama ( ar, تِهَامَةُ ') refers to the Red Sea coastal plain of the Arabian Peninsula from the Gulf of Aqaba to the Bab el Mandeb. Etymology Tihāmat is the Proto-Semitic language's term for 'sea'. Tiamat (or Tehom, in m ...
call them ''al-Baqar'' ows and
Ptolemy Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importanc ...
did not mention any of this so we l-Sufido not know if this is true or false." Both Ibn Qutaybah and Al-Sufi were probably quoting from the former's contemporary (and compatriot) and famed scientist
Abu Hanifa Dinawari Abū Ḥanīfa Aḥmad ibn Dāwūd Dīnawarī ( fa, ابوحنيفه دينوری; died 895) was a Persian Islamic Golden Age polymath, astronomer, agriculturist, botanist, metallurgist, geographer, mathematician, and historian. Life Dinawar ...
's mostly lost work on Anwaa. Abu Hanifa was probably quoting earlier sources, which may be just travelers stories, and hence Al-Sufi's comments about their veracity. In
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, the Clouds were first reported by 16th century Italian authors
Peter Martyr d'Anghiera Peter Martyr d'Anghiera ( la, Petrus Martyr Anglerius or ''ab Angleria''; it, Pietro Martire d'Anghiera; es, Pedro Mártir de Anglería; 2 February 1457 – October 1526), formerly known in English as Peter Martyr of Angleria,D'Anghier ...
and Andrea Corsali, both based on Portuguese voyages. Subsequently, they were reported by
Antonio Pigafetta Antonio Pigafetta (; – c. 1531) was an Venetian scholar and explorer. He joined the expedition to the Spice Islands led by explorer Ferdinand Magellan under the flag of the emperor Charles V and after Magellan's death in the Philippine Islands, ...
, who accompanied the expedition of
Ferdinand Magellan Ferdinand Magellan ( or ; pt, Fernão de Magalhães, ; es, link=no, Fernando de Magallanes, ; 4 February 1480 – 27 April 1521) was a Portuguese explorer. He is best known for having planned and led the 1519 Spanish expedition to the Eas ...
on its circumnavigation of the world in 1519–1522. However, naming the clouds after Magellan did not become widespread until much later. In Bayer'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, a ...
'' they are designated as ''nubecula major'' and ''nubecula minor''. In the 1756 star map of the French astronomer
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 ...
, they are designated as ''le Grand Nuage'' and ''le Petit Nuage'' ("the Large Cloud" and "the Small Cloud").
John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wo ...
studied the Magellanic Clouds from South Africa, writing an 1847 report detailing 919 objects in the Large Magellanic Cloud and 244 objects in the Small Magellanic Cloud. In 1867
Cleveland Abbe Cleveland Abbe (December 3, 1838 – October 28, 1916) was an American meteorologist and advocate of time zones. While director of the Cincinnati Observatory in Cincinnati, Ohio, he developed a system of telegraphic weather reports, daily ...
suggested that they were separate satellites of the Milky Way. Distances were first estimated by Ejnar Hertzsprung in 1913 using 1912 measurements of
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 varia ...
in the SMC by Henrietta Leavitt. Recalibration of the Cepheid scales allowed
Harlow Shapley Harlow Shapley (November 2, 1885 – October 20, 1972) was an American scientist, head of the Harvard College Observatory (1921–1952), and political activist during the latter New Deal and Fair Deal. Shapley used Cepheid variable stars to estim ...
to refine the measurement, and these were again revised in 1952 following further research.


Characteristics

The
Large Magellanic Cloud The Large Magellanic Cloud (LMC), or Nubecula Major, is a satellite galaxy of the Milky Way. At a distance of around 50  kiloparsecs (≈160,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the ...
and its neighbour and relative, the
Small Magellanic Cloud The Small Magellanic Cloud (SMC), or Nubecula Minor, is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophotal diameter of about , and contains several hundred million stars. It has a total mass of ...
, are conspicuous objects in the southern hemisphere, looking like separated pieces of 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. ...
to the naked eye. Roughly 21 ° apart in the night sky, the true distance between them is roughly 75,000
light-years 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 ...
. Until the discovery of the Sagittarius Dwarf Elliptical Galaxy in 1994, they were the closest known galaxies to our own (since 2003, the
Canis Major Dwarf Galaxy The Canis Major Overdensity (''CMa Overdensity'') or Canis Major Dwarf Galaxy (''CMa Dwarf'') is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major. The supposed small gal ...
was discovered to be closer still, and is now considered the actual nearest neighbor). The LMC lies about 160,000 light years away,Freedman, Wendy L.; Madore, Barry F
"The Hubble Constant"
''Annual Review of Astronomy and Astrophysics'', 2010
Majaess, Daniel J.; Turner, David G.; Lane, David J.; Henden, Arne; Krajci, To
"Anchoring the Universal Distance Scale via a Wesenheit Template"
''Journal of the American Association of Variable Star Observers'', 2010
while the SMC is around 200,000. The LMC is about twice the diameter of the SMC (14,000 ly and 7,000 ly respectively). For comparison, the Milky Way is about 100,000 ly across. The total mass of these two galaxies is uncertain. Only a fraction of their gas seems to have coalesced into stars and they probably both have large dark matter halos. One recent estimate of the total mass of the LMC is about 1/10 that of the Milky Way. That would make the LMC rather a large galaxy in the current observable universe. Since the sizes of relatively nearby galaxies are highly skewed, the average mass can be a misleading statistic. In terms of rank, the LMC appears to be the fourth most massive member of over 50 galaxies in the local group. Suggesting that the Magellanic cloud system is historically not a part of the Milky Way is evidence that the SMC has been in orbit about the LMC for a very long time. The Magellanic system seems most similar to the distinct
NGC 3109 NGC 3109 is a small barred Magellanic type spiral or irregular galaxy around 4.34 Mly away in the direction of the constellation of Hydra. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy Antlia Dwarf. It was d ...
system, which is on the edge of the Local Group. Astronomers have long assumed that the Magellanic Clouds have orbited the Milky Way at approximately their current distances, but evidence suggests that it is rare for them to come as close to the Milky Way as they are now. Observation and theoretical evidence suggest that the Magellanic Clouds have both been greatly distorted by tidal interaction with the Milky Way as they travel close to it. The LMC maintains a very clear spiral structure in radio-telescope images of neutral hydrogen. Streams of neutral hydrogen connect them to the Milky Way and to each other, and both resemble disrupted
barred spiral galaxies A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of all spiral galaxies, and generally affect both the motions of stars and interstellar gas within spiral galaxie ...
. Their
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
has affected the Milky Way as well, distorting the outer parts of the galactic disk. Aside from their different structure and lower mass, they differ from our galaxy in two major ways. They are gas-rich; a higher fraction of their mass is hydrogen and
helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic ta ...
compared to the Milky Way. They are also more metal-poor than the Milky Way; the youngest
star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s in the LMC and SMC have a
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 ...
of 0.5 and 0.25 times solar, respectively. Both are noted for their
nebula A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...
e and young
stellar population During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926: Baade noticed ...
s, but as in our own galaxy their stars range from the very young to the very old, indicating a long
stellar formation Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space
history. The Large Magellanic Cloud was the host galaxy to a
supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or whe ...
(
SN 1987A SN 1987A was a type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately from Earth and was the closest observed supernova since Kepler's Supernova. 1987A's light reached Earth on ...
), the brightest observed in over four centuries. Measurements with the Hubble Space Telescope, announced in 2006, suggest the Magellanic Clouds may be moving too fast to be long term companions of 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. ...
. If they are in orbit, that orbit takes at least 4 billion years. They are possibly on a first approach and we are witnessing the start of a galactic merger that may overlap with the Milky Way's expected merger with the
Andromeda Galaxy The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The gal ...
(and perhaps the Triangulum Galaxy) in the future. In 2019, astronomers discovered the young star cluster
Price-Whelan 1 Price-Whelan 1 (PW 1) is a young stellar association or disrupting star cluster with low metallicity and extragalactic origin, more specifically the leading arm of the Magellanic gas stream originating in the Magellanic Clouds. Price-Whelan ...
using ''Gaia'' data. The star cluster has a 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 ...
and belongs to the leading arm of the Magellanic Clouds. The existence of this star cluster suggests that the leading arm of the Magellanic Clouds is 90,000 light-years away from the Milky Way—closer than previously thought.


Mini Magellanic Cloud (MMC)

Astrophysicists D. S. Mathewson, V. L. Ford and N. Visvanathan proposed that the SMC may in fact be split in two, with a smaller section of this galaxy behind the main part of the SMC (as seen from Earth's perspective), and separated by about 30,000 light years. They suggest the reason for this is due to a past interaction with the LMC splitting the SMC, and that the two sections are still moving apart. They have dubbed this smaller remnant the Mini Magellanic Cloud.http://iopscience.iop.org/1538-3881/122/1/220/200523.text.html The Astronomical Journal 122:220–231 July 2001


See also

* Astronomical surveys of the Magellanic Clouds * Irregular galaxy *
Magellanic Stream The Magellanic Stream is a stream of high-velocity clouds of gas extending from the Large and Small Magellanic Clouds over 100° through the Galactic south pole of the Milky Way. The stream contains a gaseous feature dubbed the ''leading arm''. ...
* Magellanic Bridge


References


Sources

* Eric Chaisson and Steve McMillan, ''Astronomy Today'' (Englewood Cliffs: Prentice-Hall, Inc., 1993), p. 550. * Michael Zeilik, ''Conceptual Astronomy'' (New York: John Wiley & Sons, Inc., 1993), pp. 357–8.


External links


Magellanic Clouds Working Group

ESO: VISTA Peeks Through the Small Magellanic Cloud’s Dusty Veil
incl. Photos & Animations {{Authority control Local Group Milky Way Subgroup