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116-524: A galaxy is an astronomical system that consists of a large number of stars and other matter. Galaxy may also refer to: Galaxy A galaxy is a system of stars , stellar remnants , interstellar gas , dust , and dark matter bound together by gravity . The word is derived from the Greek galaxias ( γαλαξίας ), literally 'milky', a reference to the Milky Way galaxy that contains
232-656: A "small cloud". In 964, he probably mentioned the Large Magellanic Cloud in his Book of Fixed Stars , referring to "Al Bakr of the southern Arabs", since at a declination of about 70° south it was not visible where he lived. It was not well known to Europeans until Magellan 's voyage in the 16th century. The Andromeda Galaxy was later independently noted by Simon Marius in 1612. In 1734, philosopher Emanuel Swedenborg in his Principia speculated that there might be other galaxies outside that were formed into galactic clusters that were minuscule parts of
348-452: A chain reaction of star-building that spreads throughout the gaseous region. Only when the available gas is nearly consumed or dispersed does the activity end. Starbursts are often associated with merging or interacting galaxies. The prototype example of such a starburst-forming interaction is M82 , which experienced a close encounter with the larger M81 . Irregular galaxies often exhibit spaced knots of starburst activity. A radio galaxy
464-459: A common feature at the centres of galaxies. Galaxies are categorised according to their visual morphology as elliptical , spiral , or irregular . The Milky Way is an example of a spiral galaxy. It is estimated that there are between 200 billion ( 2 × 10 ) to 2 trillion galaxies in the observable universe . Most galaxies are 1,000 to 100,000 parsecs in diameter (approximately 3,000 to 300,000 light years ) and are separated by distances in
580-423: A common medieval form of apprenticeship for boys into knighthood or prestige appointments. The countess was married to Lionel of Antwerp, 1st Duke of Clarence , the second surviving son of the king, Edward III , and the position brought the teenage Chaucer into the close court circle, where he was to remain for the rest of his life. He also worked as a courtier, a diplomat, and a civil servant, as well as working for
696-545: A copy in his library among other works of Chaucer), with G. K. Chesterton writing, "among the great canonical English authors, Chaucer and Dickens have the most in common." The large number of surviving manuscripts of Chaucer's works is testimony to the enduring interest in his poetry prior to the arrival of the printing press. There are 83 surviving manuscripts of the Canterbury Tales (in whole or part) alone, along with sixteen of Troilus and Criseyde , including
812-684: A debate took place between Harlow Shapley and Heber Curtis , the Great Debate , concerning the nature of the Milky Way, spiral nebulae, and the dimensions of the universe. To support his claim that the Great Andromeda Nebula is an external galaxy, Curtis noted the appearance of dark lanes resembling the dust clouds in the Milky Way, as well as the significant Doppler shift. In 1922, the Estonian astronomer Ernst Öpik gave
928-503: A deposition in the case of Scrope v. Grosvenor . There is no further reference after this date to Philippa, Chaucer's wife. She is presumed to have died in 1387. He survived the political upheavals caused by the Lords Appellants , despite the fact that Chaucer knew some of the men executed over the affair quite well. On 12 July 1389, Chaucer was appointed the clerk of the king's works , a sort of foreman organising most of
1044-536: A distance determination that supported the theory that the Andromeda Nebula is indeed a distant extra-galactic object. Using the new 100-inch Mt. Wilson telescope, Edwin Hubble was able to resolve the outer parts of some spiral nebulae as collections of individual stars and identified some Cepheid variables , thus allowing him to estimate the distance to the nebulae: they were far too distant to be part of
1160-921: A few have well-established names, such as the Andromeda Galaxy , the Magellanic Clouds , the Whirlpool Galaxy , and the Sombrero Galaxy . Astronomers work with numbers from certain catalogues, such as the Messier catalogue , the NGC ( New General Catalogue ), the IC ( Index Catalogue ), the CGCG ( Catalogue of Galaxies and of Clusters of Galaxies ), the MCG ( Morphological Catalogue of Galaxies ),
1276-528: A few nearby bright galaxies, like the Andromeda Galaxy , began resolving them into huge conglomerations of stars, but based simply on the apparent faintness and sheer population of stars, the true distances of these objects placed them well beyond the Milky Way. For this reason they were popularly called island universes , but this term quickly fell into disuse, as the word universe implied the entirety of existence. Instead, they became known simply as galaxies. Millions of galaxies have been catalogued, but only
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#17327881029841392-418: A function of their radius (or distance from their cores) falls off more slowly than their smaller counterparts. The formation of these cD galaxies remains an active area of research, but the leading model is that they are the result of the mergers of smaller galaxies in the environments of dense clusters, or even those outside of clusters with random overdensities. These processes are the mechanisms that drive
1508-600: A general historical trend towards the creation of a vernacular literature , after the example of Dante , in many parts of Europe. A parallel trend in Chaucer's lifetime was underway in Scotland through the work of his slightly earlier contemporary, John Barbour . Barbour's work was likely to have been even more general, as is evidenced by the example of the Pearl Poet in the north of England. Although Chaucer's language
1624-433: A lease on a residence within the close of Westminster Abbey on 24 December 1399. Henry IV renewed the grants assigned by Richard, but The Complaint of Chaucer to his Purse hints that the grants might not have been paid. The last mention of Chaucer is on 5 June 1400, when some debts owed to him were repaid. Chaucer died of unknown causes on 25 October 1400, although the only evidence for this date comes from
1740-429: A low portion of open clusters and a reduced rate of new star formation. Instead, they are dominated by generally older, more evolved stars that are orbiting the common center of gravity in random directions. The stars contain low abundances of heavy elements because star formation ceases after the initial burst. In this sense they have some similarity to the much smaller globular clusters . The largest galaxies are
1856-515: A member of the royal court of Edward III as a valet de chambre , yeoman , or esquire on 20 June 1367, a position which could entail a wide variety of tasks. His wife also received a pension for court employment. He travelled abroad many times, at least some of them in his role as a valet. In 1368, he may have attended the wedding of Lionel of Antwerp to Violante Visconti , daughter of Galeazzo II Visconti , in Milan . Two other literary stars of
1972-483: A more ornate tomb, making him the first writer interred in the area now known as Poets' Corner . Chaucer was a close friend of John of Gaunt , the wealthy Duke of Lancaster and father of Henry IV, and he served under Lancaster's patronage. Near the end of their lives, Lancaster and Chaucer became brothers-in-law when Lancaster married Katherine Swynford (de Roet) in 1396; she was the sister of Philippa (de) Roet, whom Chaucer had married in 1366. Chaucer's The Book of
2088-687: A noyse gan they make That erthe & eyr & tre & euery lake So ful was that onethe was there space For me to stonde, so ful was al the place. "The language of England, upon which Chaucer was the first to confer celebrity, has amply justified the foresight which led him to disdain all others for its sake, and, in turn, has conferred an enduring celebrity upon him who trusted his reputation to it without reserve." —T. R. Lounsbury. The poet Thomas Hoccleve , who may have met Chaucer and considered him his role model, hailed Chaucer as "the firste fyndere of our fair langage". John Lydgate referred to Chaucer within his own text The Fall of Princes as
2204-417: A pattern that can be theoretically shown to result from a disturbance in a uniformly rotating mass of stars. Like the stars, the spiral arms rotate around the center, but they do so with constant angular velocity . The spiral arms are thought to be areas of high-density matter, or " density waves ". As stars move through an arm, the space velocity of each stellar system is modified by the gravitational force of
2320-532: A philosopher and astronomer , composing the scientific A Treatise on the Astrolabe for his 10-year-old son, Lewis. He maintained a career in the civil service as a bureaucrat , courtier , diplomat, and member of parliament. Among Chaucer's many other works are The Book of the Duchess , The House of Fame , The Legend of Good Women , and Troilus and Criseyde . He is seen as crucial in legitimising
2436-400: A plane, the majority of mass in spiral galaxies exists in a roughly spherical halo of dark matter which extends beyond the visible component, as demonstrated by the universal rotation curve concept. Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In
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#17327881029842552-438: A reserve of cold gas that forms giant molecular clouds . Some galaxies have been observed to form stars at an exceptional rate, which is known as a starburst . If they continue to do so, they would consume their reserve of gas in a time span less than the galaxy's lifespan. Hence starburst activity usually lasts only about ten million years, a relatively brief period in a galaxy's history. Starburst galaxies were more common during
2668-435: A rotating bar structure in the center of this galaxy. With improved radio telescopes , hydrogen gas could also be traced in other galaxies. In the 1970s, Vera Rubin uncovered a discrepancy between observed galactic rotation speed and that predicted by the visible mass of stars and gas. Today, the galaxy rotation problem is thought to be explained by the presence of large quantities of unseen dark matter . Beginning in
2784-488: A single larger galaxy; the Milky Way has at least a dozen such satellites, with an estimated 300–500 yet to be discovered. Most of the information we have about dwarf galaxies come from observations of the local group , containing two spiral galaxies, the Milky Way and Andromeda, and many dwarf galaxies. These dwarf galaxies are classified as either irregular or dwarf elliptical / dwarf spheroidal galaxies . A study of 27 Milky Way neighbors found that in all dwarf galaxies,
2900-419: A smaller companion galaxy—that as the two galaxy centers approach, they start to oscillate around a center point, and the oscillation creates gravitational ripples forming the shells of stars, similar to ripples spreading on water. For example, galaxy NGC 3923 has over 20 shells. Spiral galaxies resemble spiraling pinwheels . Though the stars and other visible material contained in such a galaxy lie mostly on
3016-575: A style which had developed in English literature since around the 12th century as an alternative to the alliterative Anglo-Saxon metre . Chaucer is known for metrical innovation, inventing the rhyme royal , and he was one of the first English poets to use the five-stress line, a decasyllabic cousin to the iambic pentametre , in his work, with only a few anonymous short works using it before him. The arrangement of these five-stress lines into rhyming couplets , first seen in his The Legend of Good Women ,
3132-528: Is 3C 236 , with lobes 15 million light-years across. It should however be noted that radio emissions are not always considered part of the main galaxy itself. A giant radio galaxy is a special class of objects characterized by the presence of radio lobes generated by relativistic jets powered by the central galaxy's supermassive black hole . Giant radio galaxies are different from ordinary radio galaxies in that they can extend to much larger scales, reaching upwards to several megaparsecs across, far larger than
3248-516: Is a galaxy with giant regions of radio emission extending well beyond its visible structure. These energetic radio lobes are powered by jets from its active galactic nucleus . Radio galaxies are classified according to their Fanaroff–Riley classification . The FR I class have lower radio luminosity and exhibit structures which are more elongated; the FR II class are higher radio luminosity. The correlation of radio luminosity and structure suggests that
3364-401: Is a reference to Lancaster (also called "Loncastel" and "Longcastell"), "walles white" is thought to be an oblique reference to Blanche, "Seynt Johan" was John of Gaunt's name-saint, and "ryche hil" is a reference to Richmond. These references reveal the identity of the grieving black knight of the poem as John of Gaunt, Duke of Lancaster and Earl of Richmond. "White" is the English translation of
3480-562: Is also used to observe distant, red-shifted galaxies that were formed much earlier. Water vapor and carbon dioxide absorb a number of useful portions of the infrared spectrum, so high-altitude or space-based telescopes are used for infrared astronomy . The first non-visual study of galaxies, particularly active galaxies, was made using radio frequencies . The Earth's atmosphere is nearly transparent to radio between 5 MHz and 30 GHz. The ionosphere blocks signals below this range. Large radio interferometers have been used to map
3596-419: Is attested by the many poets who imitated or responded to his writing. John Lydgate was one of the earliest poets to write continuations of Chaucer's unfinished Tales . At the same time Robert Henryson 's Testament of Cresseid completes the story of Cressida left unfinished in his Troilus and Criseyde . Many of the manuscripts of Chaucer's works contain material from these poets, and later appreciations by
Galaxy (disambiguation) - Misplaced Pages Continue
3712-463: Is believed that he started The Canterbury Tales in the 1380s. Chaucer also translated Boethius ' Consolation of Philosophy and The Romance of the Rose by Guillaume de Lorris (extended by Jean de Meun). Eustache Deschamps called himself a "nettle in Chaucer's garden of poetry". In 1385, Thomas Usk made glowing mention of Chaucer, and John Gower also lauded him. Chaucer's Treatise on
3828-419: Is believed to be in Chaucer's Parlement of Foules (1382), a dream vision portraying a parliament for birds to choose their mates. Honouring the first anniversary of the engagement of fifteen-year-old King Richard II of England to fifteen-year-old Anne of Bohemia : For this was on seynt Volantynys day Whan euery bryd comyth there to chese his make Of euery kynde that men thinke may And that so heuge
3944-531: Is called the Galactic Center . The Hubble classification system rates elliptical galaxies on the basis of their ellipticity, ranging from E0, being nearly spherical, up to E7, which is highly elongated. These galaxies have an ellipsoidal profile, giving them an elliptical appearance regardless of the viewing angle. Their appearance shows little structure and they typically have relatively little interstellar matter . Consequently, these galaxies also have
4060-715: Is derived from the French chaucier , once thought to mean 'shoemaker', but now known to mean a maker of hose or leggings . In 1324, his father, John Chaucer, was kidnapped by an aunt in the hope of marrying the 12-year-old to her daughter in an attempt to keep the property in Ipswich. The aunt was imprisoned and fined £250, now equivalent to about £200,000, suggesting that the family was financially secure. John Chaucer married Agnes Copton, who inherited properties in 1349, including 24 shops in London, from her uncle Hamo de Copton, who
4176-537: Is described in a will dated 3 April 1354 and listed in the City Hustings Roll as "moneyer", said to be a moneyer at the Tower of London . In the City Hustings Roll 110, 5, Ric II, dated June 1380, Chaucer refers to himself as me Galfridum Chaucer, filium Johannis Chaucer, Vinetarii, Londonie , which translates as: "I, Geoffrey Chaucer, son of the vintner John Chaucer, London". While records concerning
4292-461: Is given by the Hubble sequence . Since the Hubble sequence is entirely based upon visual morphological type (shape), it may miss certain important characteristics of galaxies such as star formation rate in starburst galaxies and activity in the cores of active galaxies . Many galaxies are thought to contain a supermassive black hole at their center. This includes the Milky Way, whose core region
4408-451: Is much closer to Modern English than the text of Beowulf , such that (unlike that of Beowulf ) a Modern English speaker with an extensive vocabulary of archaic words may understand it, it differs enough that most publications modernise his idiom. The following is a sample from the prologue of The Summoner's Tale that compares Chaucer's text to a modern translation: The first recorded association of Valentine's Day with romantic love
4524-444: Is nursing an unknown baby: she pushes the baby away, some of her milk spills, and it produces the band of light known as the Milky Way. In the astronomical literature, the capitalised word "Galaxy" is often used to refer to the Milky Way galaxy, to distinguish it from the other galaxies in the observable universe . The English term Milky Way can be traced back to a story by Geoffrey Chaucer c. 1380 : See yonder, lo,
4640-699: Is part of the Local Group , which it dominates along with the Andromeda Galaxy . The group is part of the Virgo Supercluster . At the largest scale , these associations are generally arranged into sheets and filaments surrounded by immense voids . Both the Local Group and the Virgo Supercluster are contained in a much larger cosmic structure named Laniakea . The word galaxy was borrowed via French and Medieval Latin from
4756-417: Is sometimes referred to as a flocculent spiral galaxy ; in contrast to the grand design spiral galaxy that has prominent and well-defined spiral arms. The speed in which a galaxy rotates is thought to correlate with the flatness of the disc as some spiral galaxies have thick bulges, while others are thin and dense. In spiral galaxies, the spiral arms do have the shape of approximate logarithmic spirals ,
Galaxy (disambiguation) - Misplaced Pages Continue
4872-501: Is uncertain how many children Chaucer and Philippa had, but three or four are most commonly cited. His son, Thomas Chaucer , had an illustrious career as chief butler to four kings, envoy to France, and Speaker of the House of Commons . Thomas's daughter, Alice , married the Duke of Suffolk . Thomas's great-grandson (Geoffrey's great-great-grandson), John de la Pole, Earl of Lincoln , was
4988-464: Is uncertain, but he seems to have travelled in France, Spain, and Flanders , possibly as a messenger and perhaps even going on a pilgrimage to Santiago de Compostela . Around 1366, Chaucer married Philippa (de) Roet . She was a lady-in-waiting to Edward III's queen, Philippa of Hainault , and a sister of Katherine Swynford , who later ( c. 1396 ) became the third wife of John of Gaunt . It
5104-426: The Greek term for the Milky Way, galaxías (kúklos) γαλαξίας ( κύκλος ) 'milky (circle)', named after its appearance as a milky band of light in the sky. In Greek mythology , Zeus places his son, born by a mortal woman, the infant Heracles , on Hera 's breast while she is asleep so the baby will drink her divine milk and thus become immortal. Hera wakes up while breastfeeding and then realises she
5220-630: The Middle English language from a combination of the Kentish and Midlands dialects. This is probably overstated; the influence of the court, chancery and bureaucracy – of which Chaucer was a part – remains a more probable influence on the development of Standard English . Modern English is somewhat distanced from the language of Chaucer's poems owing to the effect of the Great Vowel Shift sometime after his death. This change in
5336-476: The Romantic era poets were shaped by their failure to distinguish the later "additions" from the original Chaucer. Writers of the 17th and 18th centuries, such as John Dryden , admired Chaucer for his stories but not for his rhythm and rhyme, as few critics could then read Middle English and the text had been butchered by printers, leaving a somewhat unadmirable mess. It was not until the late 19th century that
5452-487: The Sloan Digital Sky Survey . Greek philosopher Democritus (450–370 BCE) proposed that the bright band on the night sky known as the Milky Way might consist of distant stars. Aristotle (384–322 BCE), however, believed the Milky Way was caused by "the ignition of the fiery exhalation of some stars that were large, numerous and close together" and that the "ignition takes place in the upper part of
5568-502: The Solar System . Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a thousand stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass . Most of the mass in a typical galaxy is in the form of dark matter , with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are
5684-583: The University of Nottingham , used 20 years of Hubble images to estimate that the observable universe contained at least two trillion ( 2 × 10 ) galaxies. However, later observations with the New Horizons space probe from outside the zodiacal light reduced this to roughly 200 billion ( 2 × 10 ). Galaxies come in three main types: ellipticals, spirals, and irregulars. A slightly more extensive description of galaxy types based on their appearance
5800-579: The atmosphere , in the region of the World that is continuous with the heavenly motions ." Neoplatonist philosopher Olympiodorus the Younger ( c. 495 –570 CE) was critical of this view, arguing that if the Milky Way was sublunary (situated between Earth and the Moon) it should appear different at different times and places on Earth, and that it should have parallax , which it did not. In his view,
5916-540: The pronunciation of English, still not fully understood, makes the reading of Chaucer difficult for the modern audience. The status of the final -e in Chaucer's verse is uncertain: it seems likely that during the period of Chaucer's writing, the final -e was dropping out of colloquial English and that its use was somewhat irregular. It may have been a vestige of the Old English dative singular suffix -e attached to most nouns. Chaucer's versification suggests that
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#17327881029846032-603: The spectra invisible to humans (radio telescopes, infrared cameras, and x-ray telescopes ) allows detection of other galaxies that are not detected by Hubble. Particularly, surveys in the Zone of Avoidance (the region of sky blocked at visible-light wavelengths by the Milky Way) have revealed a number of new galaxies. A 2016 study published in The Astrophysical Journal , led by Christopher Conselice of
6148-519: The type-cD galaxies . First described in 1964 by a paper by Thomas A. Matthews and others, they are a subtype of the more general class of D galaxies, which are giant elliptical galaxies, except that they are much larger. They are popularly known as the supergiant elliptical galaxies and constitute the largest and most luminous galaxies known. These galaxies feature a central elliptical nucleus with an extensive, faint halo of stars extending to megaparsec scales. The profile of their surface brightnesses as
6264-579: The "Great Andromeda Nebula", as the Andromeda Galaxy, Messier object M31 , was then known. Searching the photographic record, he found 11 more novae . Curtis noticed that these novae were, on average, 10 magnitudes fainter than those that occurred within this galaxy. As a result, he was able to come up with a distance estimate of 150,000 parsecs . He became a proponent of the so-called "island universes" hypothesis, which holds that spiral nebulae are actually independent galaxies. In 1920
6380-517: The "lodesterre (guiding principle) … off our language". Around two centuries later, Sir Philip Sidney greatly praised Troilus and Criseyde in his own Defence of Poesie . During the nineteenth and early twentieth century, Chaucer came to be viewed as a symbol of the nation's poetic heritage. In Charles Dickens ' 1850 novel David Copperfield , the Victorian era author echoed Chaucer's use of Luke 23:34 from Troilus and Criseyde (Dickens held
6496-525: The 1990s, the Hubble Space Telescope yielded improved observations. Among other things, its data helped establish that the missing dark matter in this galaxy could not consist solely of inherently faint and small stars. The Hubble Deep Field , an extremely long exposure of a relatively empty part of the sky, provided evidence that there are about 125 billion ( 1.25 × 10 ) galaxies in the observable universe. Improved technology in detecting
6612-577: The Astrolabe describes the form and use of the astrolabe in detail and is sometimes cited as the first example of technical writing in the English language. It indicates that Chaucer was versed in science in addition to his literary talents. The equatorie of the planetis is a scientific work similar to the Treatise and sometimes ascribed to Chaucer because of its language and handwriting, an identification which scholars no longer deem tenable. Chaucer wrote in continental accentual-syllabic metre ,
6728-563: The Duchess (also known as the Deeth of Blaunche the Duchesse ) was written to commemorate Blanche of Lancaster, John of Gaunt's first wife. The poem refers to John and Blanche in allegory as the narrator relates the tale of "A long castel with walles white/Be Seynt Johan, on a ryche hil" (1318–1319) who is mourning grievously after the death of his love, "And goode faire White she het/That was my lady name ryght" (948–949). The phrase "long castel"
6844-598: The French word "blanche", implying that the white lady was Blanche of Lancaster. Chaucer's short poem Fortune , believed to have been written in the 1390s, is also thought to refer to Lancaster. "Chaucer as narrator" openly defies Fortune , proclaiming that he has learned who his enemies are through her tyranny and deceit, and declares "my suffisaunce" (15) and that "over himself hath the maystrye" (14). Fortune , in turn, does not understand Chaucer's harsh words to her for she believes that she has been kind to him, claims that he does not know what she has in store for him in
6960-550: The Galaxyë Which men clepeth the Milky Wey , For hit is whyt. Galaxies were initially discovered telescopically and were known as spiral nebulae . Most 18th- to 19th-century astronomers considered them as either unresolved star clusters or anagalactic nebulae , and were just thought of as a part of the Milky Way, but their true composition and natures remained a mystery. Observations using larger telescopes of
7076-432: The Hubble classification scheme, spiral galaxies are listed as type S , followed by a letter ( a , b , or c ) which indicates the degree of tightness of the spiral arms and the size of the central bulge. An Sa galaxy has tightly wound, poorly defined arms and possesses a relatively large core region. At the other extreme, an Sc galaxy has open, well-defined arms and a small core region. A galaxy with poorly defined arms
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#17327881029847192-462: The Milky Way galaxy was "a myriad of tiny stars packed together in the sphere of the fixed stars." Actual proof of the Milky Way consisting of many stars came in 1610 when the Italian astronomer Galileo Galilei used a telescope to study it and discovered it was composed of a huge number of faint stars. In 1750, English astronomer Thomas Wright , in his An Original Theory or New Hypothesis of
7308-431: The Milky Way was a flattened disk of stars, and that some of the nebulae visible in the night sky might be separate Milky Ways. Toward the end of the 18th century, Charles Messier compiled a catalog containing the 109 brightest celestial objects having nebulous appearance. Subsequently, William Herschel assembled a catalog of 5,000 nebulae. In 1845, Lord Rosse examined the nebulae catalogued by Herschel and observed
7424-493: The Milky Way was celestial. According to Mohani Mohamed, Arabian astronomer Ibn al-Haytham (965–1037) made the first attempt at observing and measuring the Milky Way's parallax, and he thus "determined that because the Milky Way had no parallax, it must be remote from the Earth, not belonging to the atmosphere." Persian astronomer al-Biruni (973–1048) proposed the Milky Way galaxy was "a collection of countless fragments of
7540-481: The Milky Way. Despite the prominence of large elliptical and spiral galaxies, most galaxies are dwarf galaxies. They are relatively small when compared with other galactic formations, being about one hundredth the size of the Milky Way, with only a few billion stars. Blue compact dwarf galaxies contains large clusters of young, hot, massive stars . Ultra-compact dwarf galaxies have been discovered that are only 100 parsecs across. Many dwarf galaxies may orbit
7656-402: The Milky Way. In 1926 Hubble produced a classification of galactic morphology that is used to this day. Advances in astronomy have always been driven by technology. After centuries of success in optical astronomy , infrared astronomy was attempted in the 1830s, but only blossomed in the early 1900s. Radio astronomy was born in the 1930s, and matured by the 1950s and 1960s. The problem
7772-648: The UGC ( Uppsala General Catalogue of Galaxies), and the PGC ( Catalogue of Principal Galaxies , also known as LEDA). All the well-known galaxies appear in one or more of these catalogues but each time under a different number. For example, Messier 109 (or "M109") is a spiral galaxy having the number 109 in the catalogue of Messier. It also has the designations NGC 3992, UGC 6937, CGCG 269–023, MCG +09-20-044, and PGC 37617 (or LEDA 37617), among others. Millions of fainter galaxies are known by their identifiers in sky surveys such as
7888-483: The Universe , correctly speculated that it might be a rotating body of a huge number of stars held together by gravitational forces, akin to the Solar System but on a much larger scale, and that the resulting disk of stars could be seen as a band on the sky from a perspective inside it. In his 1755 treatise, Immanuel Kant elaborated on Wright's idea about the Milky Way's structure. The first project to describe
8004-630: The Visconti and Sir John Hawkwood , English condottiere (mercenary leader) in Milan. It has been speculated that it was Hawkwood on whom Chaucer based his character, the Knight, in the Canterbury Tales , for a description matches that of a 14th-century condottiere. A possible indication that his career as a writer was appreciated came when Edward III granted Chaucer "a gallon of wine daily for
8120-407: The active jets emitted from active nuclei. Ultraviolet and X-ray telescopes can observe highly energetic galactic phenomena. Ultraviolet flares are sometimes observed when a star in a distant galaxy is torn apart from the tidal forces of a nearby black hole. The distribution of hot gas in galactic clusters can be mapped by X-rays. The existence of supermassive black holes at the cores of galaxies
8236-498: The center. A different method by Harlow Shapley based on the cataloguing of globular clusters led to a radically different picture: a flat disk with diameter approximately 70 kiloparsecs and the Sun far from the centre. Both analyses failed to take into account the absorption of light by interstellar dust present in the galactic plane ; but after Robert Julius Trumpler quantified this effect in 1930 by studying open clusters ,
8352-749: The central mass is approximately 10 million solar masses , regardless of whether it has thousands or millions of stars. This suggests that galaxies are largely formed by dark matter , and that the minimum size may indicate a form of warm dark matter incapable of gravitational coalescence on a smaller scale. Interactions between galaxies are relatively frequent, and they can play an important role in galactic evolution . Near misses between galaxies result in warping distortions due to tidal interactions , and may cause some exchange of gas and dust. Collisions occur when two galaxies pass directly through each other and have sufficient relative momentum not to merge. The stars of interacting galaxies usually do not collide, but
8468-408: The commissioners of peace for Kent at a time when French invasion was a possibility. He is thought to have started work on The Canterbury Tales in the early 1380s. He also became a member of parliament for Kent in 1386 and attended the ' Wonderful Parliament ' that year. He appears to have been present at most of the 71 days it sat, for which he was paid £24 9s. On 15 October that year, he gave
8584-442: The core, or else due to a tidal interaction with another galaxy. Many barred spiral galaxies are active, possibly as a result of gas being channeled into the core along the arms. Our own galaxy, the Milky Way , is a large disk-shaped barred-spiral galaxy about 30 kiloparsecs in diameter and a kiloparsec thick. It contains about two hundred billion (2×10 ) stars and has a total mass of about six hundred billion (6×10 ) times
8700-399: The core, then merges into the spiral arm structure. In the Hubble classification scheme, these are designated by an SB , followed by a lower-case letter ( a , b or c ) which indicates the form of the spiral arms (in the same manner as the categorization of normal spiral galaxies). Bars are thought to be temporary structures that can occur as a result of a density wave radiating outward from
8816-579: The diameters of their host galaxies. Geoffrey Chaucer Geoffrey Chaucer ( / ˈ tʃ ɔː s ər / CHAW -sər ; c. 1343 – 25 October 1400) was an English poet, author, and civil servant best known for The Canterbury Tales . He has been called the "father of English literature", or, alternatively, the "father of English poetry". He was the first writer to be buried in what has since come to be called Poets' Corner , in Westminster Abbey . Chaucer also gained fame as
8932-403: The dukes of Lancaster, York , and Gloucester , and a portion of line 76 ("as three of you or tweyne") is thought to refer to the ordinance of 1390 which specified that no royal gift could be authorised without the consent of at least two of the three dukes. Most conspicuous in this short poem is the number of references to Chaucer's "beste frend". Fortune states three times in her response to
9048-572: The early 1340s (by some accounts, including his monument, he was born in 1343), though the precise date and location remain unknown. The Chaucer family offers an extraordinary example of upward mobility. His great-grandfather was a tavern keeper, his grandfather worked as a purveyor of wines, and his father, John Chaucer, rose to become an important wine merchant with a royal appointment. Several previous generations of Geoffrey Chaucer's family had been vintners and merchants in Ipswich . His family name
9164-527: The engraving on his tomb, which was erected more than 100 years after his death. There is some speculation that he was murdered by enemies of Richard II or even on the orders of his successor Henry IV, but the case is entirely circumstantial. Chaucer was buried in Westminster Abbey in London, as was his right owing to his status as a tenant of the Abbey's close. In 1556, his remains were transferred to
9280-565: The era were in attendance: Jean Froissart and Petrarch . Around this time, Chaucer is believed to have written The Book of the Duchess in honour of Blanche of Lancaster , the late wife of John of Gaunt, who died in 1369 of the plague. Chaucer travelled to Picardy the next year as part of a military expedition; in 1373, he visited Genoa and Florence . Numerous scholars such as Skeat, Boitani, and Rowland suggested that, on this Italian trip, he came into contact with Petrarch or Boccaccio . They introduced him to medieval Italian poetry ,
9396-544: The final -e is sometimes to be vocalised and sometimes to be silent; however, this remains a point on which there is disagreement. Most scholars pronounce it as a schwa when it is vocalised. Besides the irregular spelling, much of the vocabulary is recognisable to the modern reader. Chaucer is also recorded in the Oxford English Dictionary as the first author to use many common English words in his writings. These words were probably frequently used in
9512-400: The formation of fossil groups or fossil clusters, where a large, relatively isolated, supergiant elliptical resides in the middle of the cluster and are surrounded by an extensive cloud of X-rays as the residue of these galactic collisions. Another older model posits the phenomenon of cooling flow , where the heated gases in clusters collapses towards their centers as they cool, forming stars in
9628-572: The forms and stories of which he would use later. The purposes of a voyage in 1377 are mysterious, as details within the historical record conflict. Later documents suggest it was a mission, along with Jean Froissart, to arrange a marriage between the future King Richard II and a French princess, thereby ending the Hundred Years' War. If this was the purpose of their trip, they seem to have been unsuccessful, as no wedding occurred. In 1378, Richard II sent Chaucer as an envoy (secret dispatch) to
9744-464: The future, but most importantly, "And eek thou hast thy beste frend alyve" (32, 40, 48). Chaucer retorts, "My frend maystow nat reven, blind goddesse" (50) and orders her to take away those who merely pretend to be his friends. Fortune turns her attention to three princes whom she implores to relieve Chaucer of his pain and "Preyeth his beste frend of his noblesse/That to som beter estat he may atteyne" (78–79). The three princes are believed to represent
9860-590: The galaxies' original morphology. If one of the galaxies is much more massive than the other, the result is known as cannibalism , where the more massive larger galaxy remains relatively undisturbed, and the smaller one is torn apart. The Milky Way galaxy is currently in the process of cannibalizing the Sagittarius Dwarf Elliptical Galaxy and the Canis Major Dwarf Galaxy . Stars are created within galaxies from
9976-448: The gas and dust within the two forms interacts, sometimes triggering star formation. A collision can severely distort the galaxies' shapes, forming bars, rings or tail-like structures. At the extreme of interactions are galactic mergers, where the galaxies' relative momentums are insufficient to allow them to pass through each other. Instead, they gradually merge to form a single, larger galaxy. Mergers can result in significant changes to
10092-477: The heir to the throne designated by Richard III before he was deposed. Geoffrey's other children probably included Elizabeth Chaucy, a nun at Barking Abbey , Agnes, an attendant at Henry IV 's coronation; and another son, Lewis Chaucer. Chaucer's "Treatise on the Astrolabe" was written for Lewis. According to tradition, Chaucer studied law in the Inner Temple (an Inn of Court ) at this time. He became
10208-470: The higher density. (The velocity returns to normal after the stars depart on the other side of the arm.) This effect is akin to a "wave" of slowdowns moving along a highway full of moving cars. The arms are visible because the high density facilitates star formation, and therefore they harbor many bright and young stars. A majority of spiral galaxies, including the Milky Way galaxy, have a linear, bar-shaped band of stars that extends outward to either side of
10324-607: The king from 1389 to 1391 as Clerk of the King's Works. In 1359, in the early stages of the Hundred Years' War , Edward III invaded France, and Chaucer travelled with Lionel of Antwerp, Elizabeth's husband, as part of the English army . In 1360, he was captured during the siege of Rheims . Edward paid £16 for his ransom, a considerable sum equivalent to £14,557 in 2023, and Chaucer was released. After this, Chaucer's life
10440-472: The king's building projects. No major works were begun during his tenure, but he did conduct repairs on Westminster Palace , St. George's Chapel, Windsor , continued building the wharf at the Tower of London and built the stands for a tournament held in 1390. It may have been a difficult job, but it paid two shillings a day, more than three times his salary as a comptroller. Chaucer was also appointed keeper of
10556-417: The language at the time, but Chaucer was the earliest extant manuscript source with his ear for common speech. Acceptable , alkali , altercation , amble , angrily , annex , annoyance , approaching , arbitration , armless , army , arrogant , arsenic , arc , artillery and aspect are just some of almost two thousand English words first attested in Chaucer. Widespread knowledge of Chaucer's works
10672-417: The liquid stipend until Richard II came to power, after which it was converted to a monetary grant on 18 April 1378. Chaucer obtained the very substantial job of comptroller of the customs for the port of London, which he began on 8 June 1374. He must have been suited for the role as he continued in it for twelve years, a long time in such a post at that time. His life goes undocumented for much of
10788-598: The literary use of Middle English when the dominant literary languages in England were still Anglo-Norman French and Latin . Chaucer's contemporary Thomas Hoccleve hailed him as " the firste fyndere of our fair langage " (i.e., the first one capable of finding poetic matter in English). Almost two thousand English words are first attested to in Chaucerian manuscripts. Chaucer was born in London, most likely in
10904-565: The lives of his contemporaries William Langland and the Gawain Poet are practically non-existent, since Chaucer was a public servant, his official life is very well documented, with nearly five hundred written items testifying to his career. The first of the "Chaucer Life Records" appears in 1357, in the household accounts of Elizabeth de Burgh , the Countess of Ulster , when he became the noblewoman's page through his father's connections,
11020-600: The lodge at the King's Park in Feckenham Forest in Worcestershire , which was a largely honorary appointment. In September 1390, records say that Chaucer was robbed and possibly injured while conducting the business, and he stopped working in this capacity on 17 June 1391. He began as Deputy Forester in the royal forest of Petherton Park in North Petherton , Somerset on 22 June. This
11136-421: The mass of the Sun. Recently, researchers described galaxies called super-luminous spirals. They are very large with an upward diameter of 437,000 light-years (compared to the Milky Way's 87,400 light-year diameter). With a mass of 340 billion solar masses, they generate a significant amount of ultraviolet and mid-infrared light. They are thought to have an increased star formation rate around 30 times faster than
11252-446: The nature of nebulous stars." Andalusian astronomer Avempace ( d. 1138) proposed that it was composed of many stars that almost touched one another, and appeared to be a continuous image due to the effect of refraction from sublunary material, citing his observation of the conjunction of Jupiter and Mars as evidence of this occurring when two objects were near. In the 14th century, Syrian-born Ibn Qayyim al-Jawziyya proposed
11368-542: The next ten years, but it is believed that he wrote (or began) most of his famous works during this period. Chaucer's "only surviving handwriting" dates from this period. This is a request for temporary leave from work presented to King Richard II, hitherto believed to be the work of one of his subordinates due to the low level of language. On 16 October 1379, Thomas Staundon filed a legal action against his former servant Cecily Chaumpaigne and Chaucer, accusing Chaucer of unlawfully employing Chaumpaigne before her term of service
11484-415: The official Chaucerian canon, accepted today, was decided upon, largely as a result of Walter William Skeat 's work. Roughly seventy-five years after Chaucer's death, The Canterbury Tales was selected by William Caxton as one of the first books to be printed in England. Chaucer is sometimes considered the source of the English vernacular tradition. His achievement for the language can be seen as part of
11600-517: The order of millions of parsecs (or megaparsecs). For comparison, the Milky Way has a diameter of at least 26,800 parsecs (87,400 ly) and is separated from the Andromeda Galaxy , its nearest large neighbour, by just over 750,000 parsecs (2.5 million ly). The space between galaxies is filled with a tenuous gas (the intergalactic medium ) with an average density of less than one atom per cubic metre. Most galaxies are gravitationally organised into groups , clusters and superclusters . The Milky Way
11716-647: The personal copy of Henry IV. Given the ravages of time, it is likely that these surviving manuscripts represent hundreds since lost. Chaucer's original audience was a courtly one and would have included women as well as men of the upper social classes. Yet even before his death in 1400, Chaucer's audience had begun to include members of the rising literate, middle and merchant classes. This included many Lollard sympathisers who may well have been inclined to read Chaucer as one of their own. Lollards were particularly attracted to Chaucer's satirical writings about friars, priests, and other church officials. In 1464, John Baron,
11832-631: The plaintiff, "And also, you still have your best friend alive" (32, 40, 48); she also refers to his "beste frend" in the envoy when appealing to his "noblesse" to help Chaucer to a higher estate. The narrator makes a fifth reference when he rails at Fortune that she shall not take his friend from him. Chaucer respected and admired Christians and was one himself, as he wrote in Canterbury Tales , "now I beg all those that listen to this little treatise, or read it, that if there be anything in it that pleases them, they thank our Lord Jesus Christ for it, from whom proceeds all understanding and goodness.", though he
11948-472: The present picture of the Milky Way galaxy emerged. A few galaxies outside the Milky Way are visible on a dark night to the unaided eye , including the Andromeda Galaxy , Large Magellanic Cloud , Small Magellanic Cloud , and the Triangulum Galaxy . In the 10th century, Persian astronomer Abd al-Rahman al-Sufi made the earliest recorded identification of the Andromeda Galaxy, describing it as
12064-474: The process, a phenomenon observed in clusters such as Perseus , and more recently in the Phoenix Cluster . A shell galaxy is a type of elliptical galaxy where the stars in its halo are arranged in concentric shells. About one-tenth of elliptical galaxies have a shell-like structure, which has never been observed in spiral galaxies. These structures are thought to develop when a larger galaxy absorbs
12180-453: The rest of his life" for some unspecified task. This was an unusual grant, but given on a day of celebration, St George's Day , 1374, when artistic endeavours were traditionally rewarded, it is assumed to have been for another early poetic work. It is not known which, if any, of Chaucer's extant works prompted the reward, but the suggestion of him as a poet to a king places him as a precursor to later poets laureate . Chaucer continued to collect
12296-475: The shape of the Milky Way and the position of the Sun was undertaken by William Herschel in 1785 by counting the number of stars in different regions of the sky. He produced a diagram of the shape of the galaxy with the Solar System close to the center . Using a refined approach, Kapteyn in 1920 arrived at the picture of a small (diameter about 15 kiloparsecs) ellipsoid galaxy with the Sun close to
12412-439: The sources in these two types of galaxies may differ. Radio galaxies can also be classified as giant radio galaxies (GRGs), whose radio emissions can extend to scales of megaparsecs (3.26 million light-years). Alcyoneus is an FR II class low-excitation radio galaxy which has the largest observed radio emission, with lobed structures spanning 5 megaparsecs (16×10 ly ). For comparison, another similarly sized giant radio galaxy
12528-576: The spiral structure of Messier object M51 , now known as the Whirlpool Galaxy. In 1912, Vesto M. Slipher made spectrographic studies of the brightest spiral nebulae to determine their composition. Slipher discovered that the spiral nebulae have high Doppler shifts , indicating that they are moving at a rate exceeding the velocity of the stars he had measured. He found that the majority of these nebulae are moving away from us. In 1917, Heber Doust Curtis observed nova S Andromedae within
12644-498: The universe that extended far beyond what could be seen. These views "are remarkably close to the present-day views of the cosmos." In 1745, Pierre Louis Maupertuis conjectured that some nebula -like objects were collections of stars with unique properties, including a glow exceeding the light its stars produced on their own, and repeated Johannes Hevelius 's view that the bright spots were massive and flattened due to their rotation. In 1750, Thomas Wright correctly speculated that
12760-442: The universe's early history, but still contribute an estimated 15% to total star production. Starburst galaxies are characterized by dusty concentrations of gas and the appearance of newly formed stars, including massive stars that ionize the surrounding clouds to create H II regions . These stars produce supernova explosions, creating expanding remnants that interact powerfully with the surrounding gas. These outbursts trigger
12876-506: Was aware that as in any place some people in the church were venal and corrupt. Chaucer's first major work was The Book of the Duchess , an elegy for Blanche of Lancaster, who died in 1368. Two other early works were Anelida and Arcite and The House of Fame . He wrote many of his major works in a prolific period when he worked as customs comptroller for London (1374 to 1386). His Parlement of Foules , The Legend of Good Women , and Troilus and Criseyde all date from this time. It
12992-755: Was completed, which violated the Statute of Labourers . Though eight court documents dated between October 1379 and July 1380 survive the action, the case was never prosecuted. No details survive about Chaumpaigne's service or how she came to leave Staundon's employ for Chaucer's. It is not known if Chaucer was in the City of London at the time of the Peasants' Revolt , but if he was, he would have seen its leaders pass almost directly under his apartment window at Aldgate . While still working as comptroller, Chaucer appears to have moved to Kent , being appointed as one of
13108-405: Was confirmed through X-ray astronomy. In 1944, Hendrik van de Hulst predicted that microwave radiation with wavelength of 21 cm would be detectable from interstellar atomic hydrogen gas; and in 1951 it was observed. This radiation is not affected by dust absorption, and so its Doppler shift can be used to map the motion of the gas in this galaxy. These observations led to the hypothesis of
13224-407: Was no sinecure, with maintenance an essential part of the job, although there were many opportunities to derive profit. Richard II granted him an annual pension of 20 pounds in 1394 (equivalent to £22,034 in 2023), and Chaucer's name fades from the historical record not long after Richard's overthrow in 1399. The last few records of his life show his pension renewed by the new king and his taking
13340-493: Was that air only allows visible light and radio waves to pass, with a little bit of near infrared. The first ultraviolet telescope was launched in 1968, and since then there's been major progress in all regions of the electromagnetic spectrum . The dust present in the interstellar medium is opaque to visual light. It is more transparent to far-infrared , which can be used to observe the interior regions of giant molecular clouds and galactic cores in great detail. Infrared
13456-525: Was used in much of his later work and became one of the standard poetic forms in English. His early influence as a satirist is also important, with the common humorous device, the funny accent of a regional dialect , apparently making its first appearance in The Reeve's Tale . The poetry of Chaucer, along with other writers of the era, is credited with helping to standardise the London Dialect of
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