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  1. 1. From Wikipedia, the free encyclopediaThis article is about the planet. For other uses, see Uranus (disambiguation).UranusUranus presented a nearly featureless disk to Voyager 2DiscoveryDiscovered by William HerschelDiscovery date March 13, 1781DesignationsPronunciation i /ˈj ərənəs/ or i /jʊˈre ʊ ɪnəs/[1][2]Adjective UranianOrbital characteristics[3][a]Epoch J2000Aphelion 3,004,419,704 km20.083 305 26 AUPerihelion 2,748,938,461 km18.375 518 63 AUSemi-major axis 2,876,679,082 km19.229 411 95 AUEccentricity 0.044 405 586Orbital period 30,799.095 days84.323 326 yr42,718 Uranus solar days[4]Synodic period 369.66 days[5]Average orbital speed 6.81 km/s[5]Mean anomaly 142.955 717°Inclination 0.772 556° to Ecliptic6.48° to Suns equator1.02° to Invariable plane[6]Longitude of ascending node 73.989 821°Argument of perihelion 96.541 318°Satellites 27Physical characteristicsEquatorial radius 25,559 ± 4 km4.007 Earths[7][c]Polar radius 24,973 ± 20 km3.929 Earths[7][c]Flattening 0.022 9 ± 0.000 8[b]Circumference 156,909.98 km[citation needed]Surface area 8.115 6×109 km2[8][c]15.91 EarthsVolume 6.833×1013 km3[5][c]63.086 EarthsMass (8.6810 ± 0.0013)×1025 kg14.536 Earths[9]GM=5 793 939 ± 13 km3/s2Mean density 1.27 g/cm3[5][c]Equatorial surface gravity 8.69 m/s2[5][c]0.886 gEscape velocity 21.3 km/s[5][c]Sidereal rotationperiodˈ–0.718 33 day17 h 14 min 24 s[7]
  2. 2. Equatorial rotation velocity 2.59 km/s9,320 km/hAxial tilt 97.77°[7]North pole right ascension 17 h 9 min 15 s257.311°[7]North pole declinationˈ–15.175°[7]Albedo 0.300 (Bond)0.51 (geom.)[5]Surface temp. 1 bar level[11] 0.1 bar(tropopause)[12]min mean max76 K49 K 53 K 57 KApparent magnitude 5.9[10] to 5.32[5]Angular diameterˈ3.3"–4.1"[5]Atmosphere[12][13][14][d]Scale height 27.7 km[5]Composition (Below 1.3 bar)83 ± 3% Hydrogen (H2)15 ± 3% Helium2.3% Methane0.009%(0.007–0.015%)ˈHydrogen deuteride (HD)[15]Ices:Ammoniawaterammonium hydrosulfide (NH4SH)methane (CH4)Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary massUranus is similar in composition to Neptune, and both are of different chemical composition than the larger gas giantLike the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. The Uranian systeContents [hide]1 History1.1 Discovery1.2 Naming1.3 Nomenclature2 Orbit and rotation2.1 Axial tilt2.2 Visibility3 Internal structure3.1 Internal heat4 Atmosphere4.1 Composition4.2 Troposphere4.3 Upper atmosphere5 Planetary rings6 Magnetic field7 Climate7.1 Banded structure, winds and clouds7.2 Seasonal variation8 Formation9 Moons10 Exploration
  3. 3. 11 In culture12 See also13 Notes14 References15 Further reading16 External linksHistoryDiscoveryUranus had been observed on many occasions before its discovery as a planet, but it was generally mistaken for a sSir William Herschel observed the planet on March 13, 1781 while in the garden of his house at 19 New King StreetHe recorded in his journal "In the quartile near ζ Tauri … either [a] Nebulous star or perhaps a comet".[23] On March―ˈThe power I had on when I first saw the comet was 227. From experience I know that the diameters of the fixed sReplica of the telescope used by Herschel to discover Uranus (William Herschel Museum, Bath)Herschel notified the Astronomer Royal, Nevil Maskelyne, of his discovery and received this flummoxed reply from hWhile Herschel continued to cautiously describe his new object as a comet, other astronomers had already begun toThe object was soon universally accepted as a new planet. By 1783, Herschel himself acknowledged this fact to RoyNamingMaskelyne asked Herschel to "do the astronomical world the faver [sic] to give a name to your planet, which is entireWilliam Herschel, discoverer of Uranus―ˈIn the fabulous ages of ancient times the appellations of Mercury, Venus, Mars, Jupiter and Saturn were given toHerschels proposed name was not popular outside of Britain, and alternatives were soon proposed. Astronomer JérNomenclatureThe pronunciation of the name Uranus preferred among astronomers is /ˈj ərənəs/,[2][38] with stress on the first sy ʊUranus is the only planet whose name is derived from a figure from Greek mythology rather than Roman mythology:Orbit and rotationA 1998 false-colour near-infrared image of Uranus showing cloud bands, rings, and moons obtained by the Hubble SUranus revolves around the Sun once every 84 Earth years. Its average distance from the Sun is roughly 3 billion kmThe rotational period of the interior of Uranus is 17 hours, 14 minutes. As on all giant planets, its upper atmosphere eAxial tiltUranus has an axial tilt of 97.77 degrees, so its axis of rotation is approximately parallel with the plane of the Solar SNorthern hemisphere Year Southern hemisphereWinter solstice 1902, 1986 Summer solsticeVernal equinox 1923, 2007 Autumnal equinoxSummer solstice 1944, 2028 Winter solsticeAutumnal equinox 1965, 2049 Vernal equinoxOne result of this axis orientation is that, on average during the year, the polar regions of Uranus receive a greater eVisibilityFrom 1995 to 2006, Uranuss apparent magnitude fluctuated between +5.6 and +5.9, placing it just within the limit ofInternal structureSize comparison of Earth and UranusDiagram of the interior of UranusUranuss mass is roughly 14.5 times that of the Earth, making it the least massive of the giant planets. Its diameter is
  4. 4. The standard model of Uranuss structure is that it consists of three layers: a rocky (silicate/iron-nickel) core in the ceWhile the model considered above is reasonably standard, it is not unique; other models also satisfy observations. FInternal heatUranuss internal heat appears markedly lower than that of the other giant planets; in astronomical terms, it has a lowOne of the hypotheses for this discrepancy suggests that when Uranus was hit by a supermassive impactor, which cAtmosphereMain article: Atmosphere of UranusAlthough there is no well-defined solid surface within Uranuss interior, the outermost part of Uranuss gaseous enveCompositionThe composition of the Uranian atmosphere is different from the rest of the planet, consisting as it does mainly of moTroposphereTemperature profile of the Uranian troposphere and lower stratosphere. Cloud and haze layers are also indicated.The troposphere is the lowest and densest part of the atmosphere and is characterized by a decrease in temperaturThe troposphere is believed to possess a highly complex cloud structure; water clouds are hypothesised to lie in theUpper atmosphereThe middle layer of the Uranian atmosphere is the stratosphere, where temperature generally increases with altitudeThe outermost layer of the Uranian atmosphere is the thermosphere and corona, which has a uniform temperature aPlanetary ringsMain article: Rings of UranusUranuss inner rings. The bright outer ring is the ε ring; eight other rings are present.The Uranian ring systemUranus has a complicated planetary ring system, which was the second such system to be discovered in the Solar SWilliam Herschel described a possible ring around Uranus in 1789. This sighting is generally considered doubtful, asIn December 2005, the Hubble Space Telescope detected a pair of previously unknown rings. The largest is locatedMagnetic fieldThe magnetic field of Uranus as observed by Voyager 2 in 1986. S and N are magnetic south and north poles.Before the arrival of Voyager 2, no measurements of the Uranian magnetosphere had been taken, so its nature remVoyagers observations revealed that the magnetic field is peculiar, both because it does not originate from the planeDespite its curious alignment, in other respects the Uranian magnetosphere is like those of other planets: it has a boUranuss magnetosphere contains charged particles: protons and electrons with small amount of H2+ ions.[90][92] NClimateMain article: Climate of UranusUranuss southern hemisphere in approximate natural colour (left) and in shorter wavelengths (right), showing its fainAt ultraviolet and visible wavelengths, Uranuss atmosphere is remarkably bland in comparison to the other gas gianBanded structure, winds and cloudsZonal wind speeds on Uranus. Shaded areas show the southern collar and its future northern counterpart. The red cIn 1986 Voyager 2 found that the visible southern hemisphere of Uranus can be subdivided into two regions: a bright
  5. 5. The first dark spot observed on Uranus. Image obtained by the HST ACS in 2006.In the 1990s, the number of the observed bright cloud features grew considerably partly because new high resolutionThe tracking of numerous cloud features allowed determination of zonal winds blowing in the upper troposphere of USeasonal variationUranus in 2005. Rings, southern collar and a bright cloud in the northern hemisphere are visible (HST ACS image).For a short period from March to May 2004, a number of large clouds appeared in the Uranian atmosphere, giving itThere are some reasons to believe that physical seasonal changes are happening in Uranus. While the planet is knoThe mechanism of physical changes is still not clear.[102] Near the summer and winter solstices, Uranuss hemisphFormationMain article: Formation and evolution of the Solar SystemFor details of the evolution of Uranuss orbit, see Nice model.Many argue that the differences between the ice giants and the gas giants extend to their formation.[108][109] The SMoonsMain article: Moons of UranusSee also: Timeline of discovery of Solar System planets and their natural satellitesMajor moons of Uranus in order of increasing distance (left to right), at their proper relative sizes and albedos (collagThe Uranus System (NACO/VLT image)Uranus has 27 known natural satellites.[110] The names for these satellites are chosen from characters from the woAmong the satellites, Ariel appears to have the youngest surface with the fewest impact craters, while Umbriels appExplorationCrescent Uranus as imaged by Voyager 2 while departing for NeptuneMain article: Exploration of UranusIn 1986, NASAs Voyager 2 interplanetary probe encountered Uranus. This flyby remains the only investigation of theA Uranus orbiter and probe has been recommended by NASAs decadal survey; the proposal envisages launch durinIn cultureIn astrology, the planet Uranus () is the ruling planet of Aquarius. Since Uranus is colored cyan and Uranus is associThe chemical element uranium, discovered in 1789 by the German chemist Martin Heinrich Klaproth, was named aftSee also Solar System portal Uranus portal Book: Solar SystemWikipedia Books are collections of articles that can be downloaded or ordered in print.Colonization of UranusUranus in astrologyUranus in fictionNotesThis article contains special characters. Without proper rendering support, you may see question marks, boxes, or o^ Orbital elements refer to the barycenter of the Uranus system, and are the instantaneous osculating values at the p^ Calculated using data from Seidelmann, 2007.[7]^ Refers to the level of 1 bar atmospheric pressure.
  6. 6. ^ Calculation of He, H2 and CH4 molar fractions is based on a 2.3% mixing ratio of methane to hydrogen and the 15^ Mixing ratio is defined as the number of molecules of a compound per a molecule of hydrogen.References^ a b "Uranus". Oxford English Dictionary (2 ed.). 1989.^ a b The BBC Pronunciation Unit notes that |ˈj ərənəs| "is the preferred usage of astronomers": Olausson, Lena; S ʊ^ Yeomans, Donald K. (July 13, 2006). "HORIZONS System". NASA JPL. Retrieved August 8, 2007. – At the site, go^ Seligman, Courtney. "Rotation Period and Day Length". Retrieved August 13, 2009.^ a b c d e f g h i j Williams, Dr. David R. (January 31, 2005). "Uranus Fact Sheet". NASA. Retrieved August 10, 200^ "The MeanPlane (Invariable plane) of the Solar System passing through the barycenter". April 3, 2009. Retrieved A^ a b c d e f g h i Seidelmann, P. Kenneth; Archinal, B. A.; A’hearn, M. F.; et al. (2007). "Report of the IAU/IAGWorki^ a b Munsell, Kirk (May 14, 2007). "NASA: Solar System Exploration: Planets: Uranus: Facts & Figures". NASA. Re^ a b c Jacobson, R.A.; Campbell, J.K.; Taylor, A.H.; Synnott, S.P. (1992). "The masses of Uranus and its major sate^ a b c Espenak, Fred (2005). "Twelve Year Planetary Ephemeris: 1995 - 2006". NASA. Retrieved June 14, 2007.^ a b c d e f g h i j k Podolak, M.; Weizman, A.; Marley, M. (1995). "Comparative models of Uranus and Neptune". Pl^ a b c d e f g h i j k l m n o p q r s t u Lunine, Jonathan. I. (1993). "The Atmospheres of Uranus and Neptune". Annu^ a b c Lindal, G.F.; Lyons, J.R.; Sweetnam, D.N.; et al. (1987). "The Atmosphere of Uranus: Results of Radio Occul^ a b Conrath, B. et al. (1987). "The helium abundance of Uranus from Voyager measurements". Journal of Geophys^ Feuchtgruber, H.; Lellouch, E.; B. Bezard; et al. (1999). "Detection of HD in the atmospheres of Uranus and Neptun^ "MIRAs Field Trips to the Stars Internet Education Program". Monterey Institute for Research in Astronomy. Retrie^ a b c d e f g h i j k l m Smith, B.A.; Soderblom, L.A.; Beebe, A.; et al. (1986). "Voyager 2 in the Uranian System: Im^ a b c d e f g h i j k l m n o Sromovsky, L.A.; Fry, P.M. (2005). "Dynamics of cloud features on Uranus". Icarus 179:^ Dunkerson, Duane. "Uranus—About Saying, Finding, and Describing It". thespaceguy.com. Retrieved April 17, 200^ "Bath Preservation Trust". Retrieved September 29, 2007.^ William Herschel; Watson, Dr. (1781). "Account of a Comet, By Mr. Herschel, F. R. S.; Communicated by Dr. Wats^ Journal of the Royal Society and Royal Astronomical Society 1, 30, quoted in Miner, p. 8^ Royal Astronomical Society MSS W.2/1.2, 23; quoted in Miner p. 8^ RAS MSS Herschel W.2/1.2, 24, quoted in Miner p. 8^ Journal of the Royal Society and Royal Astronomical Society 1, 30; quoted in Miner p. 8^ RAS MSS Herschel W1/13.M, 14 quoted in Miner p. 8^ a b A. J. Lexell (1783). "Recherches sur la nouvelle planete, decouverte par M. Herschel & nominee Georgium Sid^ Johann Elert Bode, Berliner Astronomisches Jahrbuch, p. 210, 1781, quoted in Miner p. 11^ Miner p. 11^ a b Dreyer, J. L. E., (1912). The Scientific Papers of Sir William Herschel. 1. Royal Society and Royal Astronomica^ a b Miner p. 12^ RAS MSS Herschel W.1/12.M, 20, quoted in Miner p. 12^ "Voyager at Uranus". Nasa Jpl 7 (85): 400–268. 1986. Archived from the original on February 10, 2006.^ a b Francisca Herschel (1917). "The meaning of the symbol H+o for the planet Uranus". The Observatory. Bibcode^ a b Littmann, Mark (2004). Planets Beyond: Discovering the Outer Solar System. Courier Dover Publications. pp. 1^ Daugherty, Brian. "Astronomy in Berlin". Brian Daugherty. Retrieved May 24, 2007.^ James Finch (2006). "The Straight Scoop on Uranium". allchemicals.info: The online chemical resource. Retrieved^ In US dictionary transcription, US dict: ūr′·ə·nəs^ In US dictionary transcription, US dict: ū·rā′·nəs^ Cain, Frasier (November 12, 2007). "Astronomy Cast: Uranus". Retrieved April 20, 2009.^ "Uranian, a.2 and n.1". Oxford English Dictionary (2 ed.). 1989.^ "Planet symbols". NASA Solar System exploration. Retrieved August 4, 2007.^ "Sailormoon Terms and Information". The Sailor Senshi Page. Retrieved March 5, 2006.^ "Asian Astronomy 101". Hamilton Amateur Astronomers 4 (11). 1997. Retrieved August 5, 2007.^ "Next Stop Uranus". 1986. Retrieved June 9, 2007.^ George Forbes (1909). "History of Astronomy". Retrieved August 7, 2007.^ OConnor, J J and Robertson, E F (1996). "Mathematical discovery of planets". Retrieved June 13, 2007.^ Peter J. Gierasch and Philip D. Nicholson (2004). "Uranus". NASA World Book. Retrieved June 9, 2007.^ Lawrence Sromovsky (2006). "Hubble captures rare, fleeting shadow on Uranus". University of Wisconsin Madison^ Hammel, Heidi B. (September 5, 2006). "Uranus nears Equinox." (PDF). A report from the 2006 Pasadena Worksh^ a b "Hubble Discovers Dark Cloud In The Atmosphere Of Uranus". Science Daily. Retrieved April 16, 2007.
  7. 7. ^ Bergstralh, Jay T.; Miner, Ellis; Matthews, Mildred (1991). Uranus. pp. 485–486. ISBN 0816512086.^ "Report of the IAU/IAG working group on cartographic coordinates and rotational elements of the planets and satel^ "Cartographic Standards" (PDF). NASA. Retrieved June 13, 2007.^ "Coordinate Frames Used in MASL". 2003. Retrieved June 13, 2007.^ Nowak, Gary T. (2006). "Uranus: the Threshold Planet of 2006". Retrieved June 14, 2007.^ a b c Podolak, M.; Podolak, J.I.; Marley, M.S. (2000). "Further investigations of random models of Uranus and Nep^ a b c d e f Faure, Gunter; Mensing, Teresa (2007). "Uranus: What Happened Here?". In Faure, Gunter; Mensing, T^ a b Atreya, S.; Egeler, P.; Baines, K. (2006). "Water-ammonia ionic ocean on Uranus and Neptune?" (PDF). Geop^ Weird water lurking inside giant planets, New Scientist,September 1, 2010, Magazine issue 2776.^ a b c d Hanel, R.; Conrath, B.; Flasar, F.M.; et al. (1986). "Infrared Observations of the Uranian System". 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"Photochemistry of the Atmosphere of Uranus". The Astroph^ a b c d e Burgorf, Martin; Orton, Glenn; van Cleve, Jeffrey; et al. (2006). "Detection of new hydrocarbons in Uranus^ a b c Encrenaz, Therese (2003). "ISO observations of the giant planets and Titan: what have we learnt?". Planet. S^ a b Encrenaz, Th.; Lellouch, E.; Drossart, P. (2004). "First detection of CO in Uranus" (PDF). Astronomy & Astroph^ Atreya, Sushil K.; Wong, Ah-San (2005). "Coupled Clouds and Chemistry of the Giant Planets – a Case for Multipr^ a b c Young, Leslie A.; Bosh, Amanda S.; Buie, Marc; et al. (2001). "Uranus after Solstice: Results from the 1998 N^ a b c d e f g h Herbert, Floyd; Sandel, Bill R. (1999). "Ultraviolet Observations of Uranus and Neptune". Planet. Spa^ Trafton, L.M.; Miller, S.; Geballe, T.R.; et al. (1999). "H2 Quadrupole and H3+ Emission from Uranus: the Uranian T^ Encrenaz, Th.; Drossart, P.; Orton, G.; et al. (2003). "The rotational temperature and column density of H+3 in Ura^ a b Lam, Hoanh An; Miller, Steven; Joseph, Robert D.; et al. (1997). "Variation in the H+3 emission from Uranus". T^ a b Esposito, L.W. (2002). "Planetary rings". Reports on Progress in Physics 65: 1741–1783. Bibcode 2002RPPh..^ a b c d e "Voyager Uranus Science Summary". NASA/JPL. 1988. Retrieved June 9, 2007.^ "Uranus rings were seen in 1700s". BBC News. April 19, 2007. Retrieved April 19, 2007.^ "Did William Herschel Discover The Rings Of Uranus In The 18th Century?". Physorg.com. 2007. Retrieved June 2^ a b Elliot, J. L.; Dunham, E.; Mink, D. (1977). "The rings of Uranus". Cornell University. Retrieved June 9, 2007.^ "NASAs Hubble Discovers New Rings and Moons Around Uranus". Hubblesite. 2005. Retrieved June 9, 2007.^ a b c dePater, Imke; Hammel, Heidi B.; Gibbard, Seran G.; Showalter Mark R. (2006). "New Dust Belts of Uranus:^ Sanders, Robert (April 6, 2006). "Blue ring discovered around Uranus". UC Berkeley News. Retrieved October 3, 2^ Stephen Battersby (2006). "Blue ring of Uranus linked to sparkling ice". NewScientistSpace. Retrieved June 9, 200^ a b c d e f g h i j Ness, Norman F.; Acuna, Mario H.; Behannon, Kenneth W.; et al. (1986). "Magnetic Fields at Uran^ a b c d e f g Russell, C.T. (1993). "Planetary Magnetospheres". Rep. Prog. Phys. 56: 687–732. Bibcode 1993RPPh^ Stanley, Sabine; Bloxham, Jeremy (2004). "Convective-region geometry as the cause of Uranus’ and Neptune’s un^ a b c d e f Krimigis, S.M.; Armstrong, T.P.; Axford, W.I.; et al. (1986). "The Magnetosphere of Uranus: Hot Plasma^ "Voyager: Uranus: Magnetosphere". NASA. 2003. Retrieved June 13, 2007.^ Bridge, H.S.; Belcher, J.W.; Coppi, B.; et al. (1986). "Plasma Observations Near Uranus: Initial Results from Voyag^ a b c d e Emily Lakdawalla (2004). "No Longer Boring: Fireworks and Other Surprises at Uranus Spotted Through^ a b c d e Hammel, H.B.; de Pater, I.; Gibbard, S.; et al. (2005). "Uranus in 2003: Zonal winds, banded structure, an^ a b c d e Rages, K.A.; Hammel, H.B.; Friedson, A.J. (2004). "Evidence for temporal change at Uranus’ south pole"^ a b Sromovsky, L.A.; Fry, P.M.; Hammel, H.B.; et al., W.M.; De Pater, I.; Rages, K.A.; Showalter, M.R.; Van Dam,^ a b Karkoschka, Erich (2001). "Uranus’ Apparent Seasonal Variability in 25 HST Filters". Icarus 151: 84–92. Bibcod^ a b c d e Hammel, H.B.; de Pater, I.; Gibbard, S.G.; et al. (2005). "New cloud activity on Uranus in 2004: First detec^ a b Sromovsky, L.; Fry, P.;Hammel, H.;Rages, K. "Hubble Discovers a Dark Cloud in the Atmosphere of Uranus" (P^ a b c d e f Hammel, H.B.; Lockwood, G.W. (2007). "Long-term atmospheric variability on Uranus and Neptune". Ica^ Hammel, H.B.; Rages, K.; Lockwood, G.W.; et al. (2001). "New Measurements of the Winds of Uranus". Icarus 15^ Devitt, Terry (2004). "Keck zooms in on the weird weather of Uranus". University of Wisconsin-Madison. 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  8. 8. ^ a b Hofstadter, Mark D.; and Butler, Bryan J. (2003). "Seasonal change in the deep atmosphere of Uranus". Icarus^ a b c d Thommes, Edward W.; Duncan, Martin J.; Levison, Harold F. (1999). "The formation of Uranus and Neptun^ a b c Brunini, Adrian; Fernandez, Julio A. (1999). "Numerical simulations of the accretion of Uranus and Neptune".^ a b Sheppard, Scott S.; Jewitt, David; Kleyna, Jan (2006). "An Ultradeep Survey for Irregular Satellites of Uranus: L^ "Uranus". nineplanets.org. Retrieved July 3, 2007.^ Hussmann, Hauke; Sohl, Frank; Spohn, Tilman (2006). "Subsurface oceans and deep interiors of medium-sized ou^ Tittemore, W. C.; Wisdom, J. (1990). "Tidal evolution of the Uranian satellites III. Evolution through the Miranda-Um^ Pappalardo, R. T.; Reynolds, S. J., Greeley, R. (June 25, 1997). "Extensional tilt blocks on Miranda: Evidence for a^ Chaikin, Andrew (October 16, 2001). "Birth of Uranus Provocative Moon Still Puzzles Scientists". Space.Com. Ima^ Tittemore, W.C. (1990). "Tidal Heating of Ariel". Icarus 87: 110–139. Bibcode 1990Icar...87..110T. doi:10.1016/001^ "Voyager: The Interstellar Mission: Uranus". JPL. 2004. Retrieved June 9, 2007.^ Parker, Derek and Julia Aquarius. Planetary Zodiac Library. New York: Mitchell Beazley/Ballantine Book. 1972. p. 1^ "Uranium". The American Heritage Dictionary of the English Language (4th edition ed.). Houghton Mifflin CompanyFurther readingMiner, Ellis D. (1998). Uranus: The Planet, Rings and Satellites. New York: John Wiley and Sons. ISBN 047197398XExternal linksFind more about Uranus on Wikipedias sister projects: Definitions from Wiktionary Images and media from Commons Learning resources from Wikiversity News stories from Wikinews Quotations from Wikiquote Source texts from Wikisource Textbooks from WikibooksEdge On! ESO Press ReleaseNASAs Uranus fact sheetUranus Profile at NASAs Solar System Exploration siteKeck pictures of Uranus show best view from the ground – Press release with some photographs showing rings, satNews reports of December 22, 2005 rings and moons discoveryNew Moons and Rings found at Uranus, SPACE.comTwo more rings discovered around Uranus, MSNBCPlanets—Uranus A kids guide to Uranus.Spring Has Sprung on UranusUranus at Jet Propulsion Laboratorys planetary photojournal.Uranus (Astronomy Cast homepage)[show]v · d · eUranus[show]v · d · eThe Solar SystemCategories: Uranus | Gas giant planets | Astronomical objects discovered in 1781
  9. 9. th-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus (Ancient Greek: Οὐρανός), the fat than the larger gas giants Jupiter and Saturn. As such, astronomers sometimes place them in a separate category, the "ice giants". Uranusoons. The Uranian system has a unique configuration among the planets because its axis of rotation is tilted sideways, nearly into the plane
  10. 10. generally mistaken for a star. The earliest recorded sighting was in 1690 when John Flamsteed observed the planet at least six times, catalogse at 19 New King Street in the town of Bath, Somerset (now the Herschel Museum of Astronomy),[20] but initially reported it (on April 26, 17s a comet".[23] On March 17, he noted, "I looked for the Comet or Nebulous Star and found that it is a Comet, for it has changed its place".[2e diameters of the fixed stars are not proportionally magnified with higher powers, as planets are; therefore I now put the powers at 460 ands flummoxed reply from him on April 23: "I dont know what to call it. It is as likely to be a regular planet moving in an orbit nearly circular to th ers had already begun to suspect otherwise. Russian astronomer Anders Johan Lexell was the first to compute the orbit of the new object[2 owledged this fact to Royal Society president Joseph Banks: "By the observation of the most eminent Astronomers in Europe it appears thatour planet, which is entirely your own, [and] which we are so much obliged to you for the discovery of."[32] In response to Maskelynes requesand Saturn were given to the Planets, as being the names of their principal heroes and divinities. In the present more philosophical era it wou roposed. Astronomer Jérôme Lalande proposed the planet be named Herschel in honour of its discoverer.[34] Swedish astronomer Erik Pro with stress on the first syllable as in Latin Ūranus; in contrast to the colloquial /jʊˈreɪnəs/,[39] with stress on the second syllable and a longr than Roman mythology: the Greek "Οὐρανός" arrived in English by way of the Latin "Ūranus".[1] The adjective of Uranus is "Uranian".[41] It obtained by the Hubble Space Telescopes NICMOS camera.Sun is roughly 3 billion km (about 20 AU). The intensity of sunlight on Uranus is about 1/400 that on Earth.[45] Its orbital elements were first c s, its upper atmosphere experiences very strong winds in the direction of rotation. At some latitudes, such as about two-thirds of the way fromh the plane of the Solar System. This gives it seasonal changes completely unlike those of the other major planets. Other planets can be visuranus receive a greater energy input from the Sun than its equatorial regions. Nevertheless, Uranus is hotter at its equator than at its poles. T g it just within the limit of naked eye visibility at +6.5.[10] Its angular diameter is between 3.4 and 3.7 arcseconds, compared with 16 to 20 arant planets. Its diameter is slightly larger than Neptunes at roughly four times Earths. A resulting density of 1.27 g/cm3 makes Uranus the se
  11. 11. iron-nickel) core in the center, an icy mantle in the middle and an outer gaseous hydrogen/helium envelope.[11][58] The core is relatively sm so satisfy observations. For instance, if substantial amounts of hydrogen and rocky material are mixed in the ice mantle, the total mass of icenomical terms, it has a low thermal flux.[18][61] Why Uranuss internal temperature is so low is still not understood. Neptune, which is Uranusmassive impactor, which caused it to expel most of its primordial heat, it was left with a depleted core temperature.[63] Another hypothesis is f Uranuss gaseous envelope that is accessible to remote sensing is called its atmosphere.[12] Remote sensing capability extends down to rng as it does mainly of molecular hydrogen and helium.[12] The helium molar fraction, i.e. the number of helium atoms per molecule of gas, iyers are also indicated.a decrease in temperature with altitude.[12] The temperature falls from about 320 K at the base of the nominal troposphere at −300 km to 53hypothesised to lie in the pressure range of 50 to 100 bar (5 to 10 MPa), ammonium hydrosulfide clouds in the range of 20 to 40 bar (2 to 4 M lly increases with altitude from 53 K in the tropopause to between 800 and 850 K at the base of the thermosphere.[65] The heating of the strs a uniform temperature around 800 to 850 K.[12][76] The heat sources necessary to sustain such a high value are not understood, since ne discovered in the Solar System after Saturns.[80] The rings are composed of extremely dark particles, which vary in size from micrometers y considered doubtful, as the rings are quite faint, and in the two following centuries none were noted by other observers. Still, Herschel mad gs. The largest is located at twice the distance from the planet of the previously known rings. These new rings are so far from the planet that th and north poles. taken, so its nature remained a mystery. Before 1986, astronomers had expected the magnetic field of Uranus to be in line with the solar wiot originate from the planets geometric center, and because it is tilted at 59° from the axis of rotation.[89][90] In fact the magnetic dipole is sh other planets: it has a bow shock located at about 23 Uranian radii ahead of it, a magnetopause at 18 Uranian radii, a fully developed magneunt of H2+ ions.[90][92] No heavier ions have been detected. Many of these particles probably derive from the hot atmospheric corona.[92] T hs (right), showing its faint cloud bands and atmospheric "hood" as seen by Voyager 2 son to the other gas giants, even to Neptune, which it otherwise closely resembles.[18] When Voyager 2 flew by Uranus in 1986, it observed rn counterpart. The red curve is a symmetrical fit to the data. into two regions: a bright polar cap and dark equatorial bands (see figure on the right).[17] Their boundary is located at about −45 degrees o
  12. 12. cause new high resolution imaging techniques became available.[18] Most were found in the northern hemisphere as it started to become vis e upper troposphere of Uranus.[18] At the equator winds are retrograde, which means that they blow in the reverse direction to the planetarysible (HST ACS image).ian atmosphere, giving it a Neptune-like appearance.[100][104] Observations included record-breaking wind speeds of 229 m/s (824 km/h) a s. While the planet is known to have a bright south polar region, the north pole is fairly dim, which is incompatible with the model of the seasstices, Uranuss hemispheres lie alternately either in full glare of the Suns rays or facing deep space. The brightening of the sunlit hemispherormation.[108][109] The Solar System is believed to have formed from a giant rotating ball of gas and dust known as the presolar nebula. Musizes and albedos (collage of Voyager 2 photographs)m characters from the works of Shakespeare and Alexander Pope.[58][111] The five main satellites are Miranda, Ariel, Umbriel, Titania and Oters, while Umbriels appears oldest.[17][81] Miranda possesses fault canyons 20 kilometers deep, terraced layers, and a chaotic variation in e only investigation of the planet carried out from a short distance, and no other visits are currently planned. Launched in 1977, Voyager 2 msal envisages launch during 2020-2023 and a 13-year cruise to Uranus.yan and Uranus is associated with electricity, the color electric blue, a color close to cyan, is associated with the sign Aquarius.[118] (See Ura Klaproth, was named after the newly discovered planet Uranus.[119] Uranus, the Magician is a movement in Gustav Holsts The Planets, westion marks, boxes, or other symbols.osculating values at the precise J2000 epoch. Barycenter quantities are given because, in contrast to the planetary center, they do not exper
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  15. 15. sphere of Uranus". Icarus 165: 168–180. Bibcode 2003Icar..165..168H. doi:10.1016/S0019-1035(03)00174-X. on of Uranus and Neptune in the Jupiter-Saturn region of the Solar System" (PDF). Nature 402 (6762): 635–638. Bibcode 1999Natur.402..63of Uranus and Neptune". Plan. Space Sci. 47: 591–605. Bibcode 1999P&SS...47..591B. doi:10.1016/S0032-0633(98)00140-8. lar Satellites of Uranus: Limits to Completeness". The Astronomical Journal 129: 518–525. arXiv:astro-ph/0410059. Bibcode 2005AJ....129..eriors of medium-sized outer planet satellites and large trans-neptunian objects". Icarus 185: 258–273. Bibcode 2006Icar..185..258H. doi:10.n through the Miranda-Umbriel 3:1, Miranda-Ariel 5:3, and Ariel-Umbriel 2:1 mean-motion commensurabilities". Icarus (Elsevier Science) 85n Miranda: Evidence for an upwelling origin of Arden Corona". Journal of Geophysical Research (Elsevier Science) 102 (E6): 13,369–13,380entists". Space.Com. ImaginovaCorp.. Retrieved December 7, 2007. 7..110T. doi:10.1016/0019-1035(90)90024-4.allantine Book. 1972. p. 14.oughton Mifflin Company. Retrieved April 20, 2010. Sons. ISBN 047197398X.. raphs showing rings, satellites and clouds
  16. 16. Greek: Οὐρανός), the father of Cronus (Saturn) and grandfather of Zeus (Jupiter). Though it is visible to the naked eye like the five classical, the "ice giants". Uranuss atmosphere, while similar to Jupiter and Saturns in its primary composition of hydrogen and helium, contains moays, nearly into the plane of its revolution about the Sun. As such, its north and south poles lie where most other planets have their equators.
  17. 17. at least six times, cataloging it as 34 Tauri. The French astronomer Pierre Lemonnier observed Uranus at least twelve times between 1750eported it (on April 26, 1781) as a "comet".[21] Herschel "engaged in a series of observations on the parallax of the fixed stars",[22] using a te has changed its place".[24] When he presented his discovery to the Royal Society, he continued to assert that he had found a comet while aut the powers at 460 and 932, and found that the diameter of the comet increased in proportion to the power, as it ought to be, on the suppos orbit nearly circular to the sun as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it".[26] orbit of the new object[27] and its nearly circular orbit led him to a conclusion that it was a planet rather than a comet. Berlin astronomer Joh in Europe it appears that the new star, which I had the honour of pointing out to them in March 1781, is a Primary Planet of our Solar System se to Maskelynes request, Herschel decided to name the object Georgium Sidus (Georges Star), or the "Georgian Planet" in honour of hise philosophical era it would hardly be allowable to have recourse to the same method and call it Juno, Pallas, Apollo or Minerva, for a name tdish astronomer Erik Prosperin proposed the name Neptune which was supported by other astronomers who liked the idea to commemorate cond syllable and a long a, though both are considered acceptable. Because, in the English-speaking world, ū·rā′·nəs sounds like "your anusUranus is "Uranian".[41] Its astronomical symbol is . It is a hybrid of the symbols for Mars and the Sun because Uranus was the Sky in Greekbital elements were first calculated in 1783 by Pierre-Simon Laplace.[46] With time, discrepancies began to appear between the predicted an two-thirds of the way from the equator to the south pole, visible features of the atmosphere move much faster, making a full rotation in as litOther planets can be visualized to rotate like tilted spinning tops on the plane of the Solar System, while Uranus rotates more like a tilted rollquator than at its poles. The underlying mechanism which causes this is unknown. The reason for Uranuss unusual axial tilt is also not knowompared with 16 to 20 arcseconds for Saturn and 32 to 45 arcseconds for Jupiter.[10] At opposition, Uranus is visible to the naked eye in dam3 makes Uranus the second least dense planet, after Saturn.[7][9] This value indicates that it is made primarily of various ices, such as wa
  18. 18. The core is relatively small, with a mass of only 0.55 Earth masses and a radius less than 20% of Uranuss; the mantle comprises the bulk ontle, the total mass of ices in the interior will be lower, and, correspondingly, the total mass of rocks and hydrogen will be higher. Presently aNeptune, which is Uranuss near twin in size and composition, radiates 2.61 times as much energy into space as it receives from the Sun.[183] Another hypothesis is that some form of barrier exists in Uranuss upper layers which prevents the cores heat from reaching the surface.[pability extends down to roughly 300 km below the 1 bar (100 kPa) level, with a corresponding pressure around 100 bar (10 MPa) and tempems per molecule of gas, is 0.15 ± 0.03[14] in the upper troposphere, which corresponds to a mass fraction 0.26 ± 0.05.[12][62] This value isosphere at −300 km to 53 K at 50 km.[64][67] The temperatures in the coldest upper region of the troposphere (the tropopause) actually vary e of 20 to 40 bar (2 to 4 MPa), ammonia or hydrogen sulfide clouds at between 3 and 10 bar (0.3 to 1 MPa) and finally directly detected thin65] The heating of the stratosphere is caused by absorption of solar UV and IR radiation by methane and other hydrocarbons,[75] which formnot understood, since neither solar far UV and extreme UV radiation nor auroral activity can provide the necessary energy. The weak coolingn size from micrometers to a fraction of a meter.[17] Thirteen distinct rings are presently known, the brightest being the ε ring. All except tworvers. Still, Herschel made an accurate description of the epsilon rings size, its angle relative to the Earth, its red color, and its apparent chao far from the planet that they are called the "outer" ring system. Hubble also spotted two small satellites, one of which, Mab, shares its orbitbe in line with the solar wind, since it would then align with the planets poles that lie in the ecliptic.[89] the magnetic dipole is shifted from the center of the planet towards the south rotational pole by as much as one third of the planetary radius., a fully developed magnetotail and radiation belts.[89][90][92] Overall, the structure of Uranuss magnetosphere is different from Jupiters an tmospheric corona.[92] The ion and electron energies can be as high as 4 and 1.2 megaelectronvolts, respectively.[92] The density of low enanus in 1986, it observed a total of ten cloud features across the entire planet.[17][95] One proposed explanation for this dearth of features isd at about −45 degrees of latitude. A narrow band straddling the latitudinal range from −45 to −50 degrees is the brightest large feature on th
  19. 19. s it started to become visible.[18] An early explanation—that bright clouds are easier to identify in the dark part of the planet, whereas in the direction to the planetary rotation. Their speeds are from −100 to −50 m/s.[18][96] Wind speeds increase with the distance from the equators of 229 m/s (824 km/h) and a persistent thunderstorm referred to as "Fourth of July fireworks".[95] On August 23, 2006, researchers at the S ith the model of the seasonal change outlined above.[102] During its previous northern solstice in 1944, Uranus displayed elevated levels ofng of the sunlit hemisphere is thought to result from the local thickening of the methane clouds and haze layers located in the troposphere.[97s the presolar nebula. Much of the nebulas gas, primarily hydrogen and helium, formed the Sun, while the dust grains collected together to foiel, Umbriel, Titania and Oberon.[58] The Uranian satellite system is the least massive among the gas giants; indeed, the combined mass ofand a chaotic variation in surface ages and features.[17] Mirandas past geologic activity is believed to have been driven by tidal heating at ahed in 1977, Voyager 2 made its closest approach to Uranus on January 24, 1986, coming within 81,500 kilometers of the planets cloudtopsn Aquarius.[118] (See Uranus in astrology)av Holsts The Planets, written between 1914 and 1916. Operation Uranus was the successful military operation in World War II by the Soviecenter, they do not experience appreciable changes on a day-to-day basis from the motion of the moons.
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  23. 23. eye like the five classical planets, it was never recognized as a planet by ancient observers because of its dimness and slow orbit.[16] Sir Wiand helium, contains more "ices" such as water, ammonia and methane, along with traces of hydrocarbons.[12] It is the coldest planetary atmnets have their equators.[17] Seen from Earth, Uranuss rings can sometimes appear to circle the planet like an archery target and its moons
  24. 24. elve times between 1750 and 1769,[19] including on four consecutive nights.fixed stars",[22] using a telescope of his own design.ad found a comet while also implicitly comparing it to a planet:[25]ught to be, on the supposition of its not being a fixed star, while the diameters of the stars to which I compared it were not increased in the sa et. Berlin astronomer Johann Elert Bode described Herschels discovery as "a moving star that can be deemed a hitherto unknown planet-likPlanet of our Solar System."[30] In recognition of his achievement, King George III gave Herschel an annual stipend of £200 on the condition Planet" in honour of his new patron, King George III.[33] He explained this decision in a letter to Joseph Banks:[30]o or Minerva, for a name to our new heavenly body. The first consideration of any particular event, or remarkable incident, seems to be its chthe idea to commemorate the victories of the British Royal Naval fleet in the course of the American Revolutionary War by calling the new plaəs sounds like "your anus", the former pronunciation also saves embarrassment: as Dr. Pamela Gay, an astronomer at Southern Illinois Univnus was the Sky in Greek mythology, which was thought to be dominated by the combined powers of the Sun and Mars.[42] Its astrological s between the predicted and observed orbits, and in 1841, John Couch Adams first proposed that the differences might be due to the gravitatiking a full rotation in as little as 14 hours.[48]ates more like a tilted rolling ball. Near the time of Uranian solstices, one pole faces the Sun continuously while the other pole faces away. Oal axial tilt is also not known with certainty, but the usual speculation is that during the formation of the Solar System, an Earth sized protoplan le to the naked eye in dark skies, and becomes an easy target even in urban conditions with binoculars.[8] In larger amateur telescopes with various ices, such as water, ammonia, and methane.[11] The total mass of ice in Uranuss interior is not precisely known, as different figure
  25. 25. antle comprises the bulk of the planet, with around 13.4 Earth masses, while the upper atmosphere is relatively insubstantial, weighing aboutwill be higher. Presently available data does not allow science to determine which model is correct.[57] The fluid interior structure of Uranus m eceives from the Sun.[18] Uranus, by contrast, radiates hardly any excess heat at all. The total power radiated by Uranus in the far infrared (om reaching the surface.[11] For example, convection may take place in a set of compositionally different layers, which may inhibit the upwar bar (10 MPa) and temperature of 320 K.[64] The tenuous corona of the atmosphere extends remarkably over two planetary radii from the no.05.[12][62] This value is very close to the protosolar helium mass fraction of 0.275 ± 0.01,[66] indicating that helium has not settled in the cetropopause) actually vary in the range between 49 and 57 K depending on planetary latitude.[12][61] The tropopause region is responsible foally directly detected thin methane clouds at 1 to 2 bar (0.1 to 0.2 MPa).[12][13][64][74] The troposphere is a very dynamic part of the atmosprocarbons,[75] which form in this part of the atmosphere as a result of methane photolysis.[70] Heat is also conducted from the hot thermospenergy. The weak cooling efficiency due to the lack of hydrocarbons in the stratosphere above 0.1 mBar pressure level may contribute too.[6 the ε ring. All except two rings of Uranus are extremely narrow—they are usually a few kilometres wide. The rings are probably quite young;olor, and its apparent changes as Uranus traveled around the Sun.[82][83] The ring system was definitively discovered on March 10, 1977 by ich, Mab, shares its orbit with the outermost newly discovered ring. The new rings bring the total number of Uranian rings to 13.[85] In April 2 d of the planetary radius.[89] This unusual geometry results in a highly asymmetric magnetosphere, where the magnetic field strength on thedifferent from Jupiters and more similar to Saturns.[89][90] Uranuss magnetotail trails behind the planet into space for millions of kilometers [92] The density of low energy (below 1 kiloelectronvolt) ions in the inner magnetosphere is about 2 cm−3.[94] The particle population is stror this dearth of features is that Uranuss internal heat appears markedly lower than that of the other giant planets. The lowest temperature reghtest large feature on the visible surface of the planet.[17][96] It is called a southern "collar". The cap and collar are thought to be a dense r
  26. 26. he planet, whereas in the southern hemisphere the bright collar masks them—was shown to be incorrect: the actual number of features hasdistance from the equator, reaching zero values near ±20° latitude, where the tropospheres temperature minimum is located.[18][61] Closer2006, researchers at the Space Science Institute (Boulder, CO) and the University of Wisconsin observed a dark spot on Uranuss surface, gplayed elevated levels of brightness, which suggests that the north pole was not always so dim.[105] This information implies that the visible ted in the troposphere.[97] The bright collar at −45° latitude is also connected with methane clouds.[97] Other changes in the southern polarns collected together to form the first protoplanets. As the planets grew, some of them eventually accreted enough matter for their gravity to h d, the combined mass of the five major satellites would be less than half that of Triton alone.[9] The largest of the satellites, Titania, has a ra riven by tidal heating at a time when its orbit was more eccentric than currently, probably as a result of a formerly present 3:1 orbital resonan of the planets cloudtops, before continuing its journey to Neptune. Voyager 2 studied the structure and chemical composition of Uranuss atWorld War II by the Soviet army to take back Stalingrad and marked the turning point in the land war against the Wehrmacht.
  27. 27. gust 5, 2007.
  28. 28. and slow orbit.[16] Sir William Herschel announced its discovery on March 13, 1781, expanding the known boundaries of the Solar System fs the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (–224 °C). It has a complex, layered cloud struhery target and its moons revolve around it like the hands of a clock, though in 2007 and 2008 the rings appeared edge-on. In 1986, images
  29. 29. re not increased in the same ratio. Moreover, the comet being magnified much beyond what its light would admit of, appeared hazy and ill-de therto unknown planet-like object circulating beyond the orbit of Saturn".[28] Bode concluded that its near-circular orbit was more like a plane of £200 on the condition that he move to Windsor so that the Royal Family could have a chance to look through his telescopes.[31]cident, seems to be its chronology: if in any future age it should be asked, when this last-found Planet was discovered? It would be a very satWar by calling the new planet even Neptune George III or Neptune Great Britain.[27] Bode opted for Uranus, the Latinized version of the Gre r at Southern Illinois University Edwardsville, noted on her podcast, to avoid "being made fun of by any small schoolchildren ... when in doubMars.[42] Its astrological symbol is , suggested by Lalande in 1784. In a letter to Herschel, Lalande described it as "un globe surmonté par la pght be due to the gravitational tug of an unseen planet. In 1845, Urbain Le Verrier began his own independent research into Uranuss orbit. O other pole faces away. Only a narrow strip around the equator experiences a rapid day-night cycle, but with the Sun very low over the horizon , an Earth sized protoplanet collided with Uranus, causing the skewed orientation.[52] Uranuss south pole was pointed almost directly at the amateur telescopes with an objective diameter of between 15 and 23 cm, the planet appears as a pale cyan disk with distinct limb darkeninknown, as different figures emerge depending on the model chosen; it must be between 9.3 and 13.5 Earth masses.[11][57] Hydrogen and h
  30. 30. bstantial, weighing about 0.5 Earth masses and extending for the last 20% of Uranuss radius.[11][58] Uranuss core density is around 9 g/cm rior structure of Uranus means that it has no solid surface. The gaseous atmosphere gradually transitions into the internal liquid layers.[11] F ranus in the far infrared (i.e. heat) part of the spectrum is 1.06 ± 0.08 times the solar energy absorbed in its atmosphere.[12][62] In fact, Uran ich may inhibit the upward heat transport.[12][62] planetary radii from the nominal surface at 1 bar pressure.[65] The Uranian atmosphere can be divided into three layers: the troposphere, bem has not settled in the center of the planet as it has in the gas giants.[12] The third most abundant constituent of the Uranian atmosphere is e region is responsible for the vast majority of the planet’s thermal far infrared emissions, thus determining its effective temperature of 59.1 ±ynamic part of the atmosphere, exhibiting strong winds, bright clouds and seasonal changes, which will be discussed below.[18] ed from the hot thermosphere.[75] The hydrocarbons occupy a relatively narrow layer at altitudes of between 100 and 300 km correspondingevel may contribute too.[65][76] In addition to molecular hydrogen, the thermosphere-corona contains many free hydrogen atoms. Their smalare probably quite young; the dynamics considerations indicate that they did not form with Uranus. The matter in the rings may once have be ed on March 10, 1977 by James L. Elliot, Edward W. Dunham, and Douglas J. Mink using the Kuiper Airborne Observatory. The discovery w rings to 13.[85] In April 2006, images of the new rings with the Keck Observatory yielded the colours of the outer rings: the outermost is bluegnetic field strength on the surface in the southern hemisphere can be as low as 0.1 gauss (10 µT), whereas in the northern hemisphere it ca for millions of kilometers and is twisted by the planets sideways rotation into a long corkscrew.[89][93] particle population is strongly affected by the Uranian moons that sweep through the magnetosphere leaving noticeable gaps.[92] The partic he lowest temperature recorded in Uranuss tropopause is 49 K, making Uranus the coldest planet in the Solar System, colder than Neptune e thought to be a dense region of methane clouds located within the pressure range of 1.3 to 2 bar (see above).[97] Besides the large-scale
  31. 31. number of features has indeed increased considerably.[99][100] Nevertheless there are differences between the clouds of each hemispheres located.[18][61] Closer to the poles, the winds shift to a prograde direction, flowing with the planets rotation. Windspeeds continue to increaot on Uranuss surface, giving astronomers more insight into the planets atmospheric activity.[101] Why this sudden upsurge in activity shouon implies that the visible pole brightens some time before the solstice and darkens after the equinox.[102] Detailed analysis of the visible anges in the southern polar region can be explained by changes in the lower cloud layers.[97] The variation of the microwave emission from thematter for their gravity to hold onto the nebulas leftover gas.[108][109] The more gas they held onto, the larger they became; the larger they atellites, Titania, has a radius of only 788.9 km, or less than half that of the Moon, but slightly more than Rhea, the second largest moon of Sresent 3:1 orbital resonance with Umbriel.[113] Extensional processes associated with upwelling diapirs are the likely origin of the moons raomposition of Uranuss atmosphere,[67] including the planets unique weather, caused by its axial tilt of 97.77°. It made the first detailed inves
  32. 32. ies of the Solar System for the first time in modern history. Uranus was also the first planet discovered with a telescope.mplex, layered cloud structure, with water thought to make up the lowest clouds, and methane thought to make up the uppermost layer of cloedge-on. In 1986, images from Voyager 2 showed Uranus as a virtually featureless planet in visible light without the cloud bands or storms as
  33. 33. , appeared hazy and ill-defined with these great powers, while the stars preserved that lustre and distinctness which from many thousand ob rbit was more like a planet than a comet.[29] telescopes.[31]ed? It would be a very satisfactory answer to say, In the reign of King George the Third .ˈ‖tinized version of the Greek god of the sky, Ouranos. Bode argued that just as Saturn was the father of Jupiter, the new planet should be nam lchildren ... when in doubt, dont emphasise anything and just say ūr′·ə·nəs. And then run, quickly."[40] n globe surmonté par la première lettre de votre nom" ("a globe surmounted by the first letter of your surname").[34] In the Chinese, Japanes rch into Uranuss orbit. On September 23, 1846, Johann Gottfried Galle located a new planet, later named Neptune, at nearly the position pr very low over the horizon as in the Earths polar regions. At the other side of Uranuss orbit the orientation of the poles towards the Sun is re ted almost directly at the Sun at the time of Voyager 2s flyby in 1986. The labeling of this pole as "south" uses the definition currently endorswith distinct limb darkening. With a large telescope of 25 cm or wider, cloud patterns, as well as some of the larger satellites, such as Titania .[11][57] Hydrogen and helium constitute only a small part of the total, with between 0.5 and 1.5 Earth masses.[11] The remainder of the non
  34. 34. e density is around 9 g/cm3, with a pressure in the center of 8 million bars (800 GPa) and a temperature of about 5000 K.[57][58] The ice manternal liquid layers.[11] For the sake of convenience, a revolving oblate spheroid set at the point at which atmospheric pressure equals 1 bahere.[12][62] In fact, Uranuss heat flux is only 0.042 ± 0.047 W/m2, which is lower than the internal heat flux of Earth of about 0.075 W/m2.[yers: the troposphere, between altitudes of −300 and 50 km and pressures from 100 to 0.1 bar; (10 MPa to 10 kPa), the stratosphere, spanne Uranian atmosphere is methane (CH4).[12] Methane possesses prominent absorption bands in the visible and near-infrared (IR) making Uive temperature of 59.1 ± 0.3 K.[61][62]d below.[18]nd 300 km corresponding to a pressure range of 10 to 0.1 mbar (1000 to 10 kPa) and temperatures of between 75 and 170 K.[68][71] The mdrogen atoms. Their small mass together with the high temperatures explain why the corona extends as far as 50 000 km or two Uranian rad rings may once have been part of a moon (or moons) that was shattered by high-speed impacts. From numerous pieces of debris that formervatory. The discovery was serendipitous; they planned to use the occultation of the star SAO 158687 by Uranus to study the planets atmosngs: the outermost is blue and the other red.[86][87] One hypothesis concerning the outer rings blue colour is that it is composed of minute pnorthern hemisphere it can be as high as 1.1 gauss (110 µT).[89] The average field at the surface is 0.23 gauss (23 µT).[89] In comparison, table gaps.[92] The particle flux is high enough to cause darkening or space weathering of the moon’s surfaces on an astronomically rapid timem, colder than Neptune.[12][62] Besides the large-scale banded structure, Voyager 2 observed ten small bright clouds, most lying several degrees to the north from the coll
  35. 35. ouds of each hemisphere. The northern clouds are smaller, sharper and brighter.[100] They appear to lie at a higher altitude.[100] The lifetimspeeds continue to increase reaching maxima at ±60° latitude before falling to zero at the poles.[18] Windspeeds at −40° latitude range fromn upsurge in activity should be occurring is not fully known, but it appears that Uranuss extreme axial tilt results in extreme seasonal variatio analysis of the visible and microwave data revealed that the periodical changes of brightness are not completely symmetrical around the solrowave emission from the planet is probably caused by a changes in the deep tropospheric circulation, because thick polar clouds and hazebecame; the larger they became, the more gas they held onto until a critical point was reached, and their size began to increase exponentiasecond largest moon of Saturn, making Titania the eighth largest moon in the Solar System. The moons have relatively low albedos; ranging y origin of the moons racetrack-like coronae.[114][115] Similarly, Ariel is believed to have once been held in a 4:1 resonance with Titania.[1ade the first detailed investigations of its five largest moons, and discovered 10 new moons. It examined all nine of the systems known rings
  36. 36. he uppermost layer of clouds.[12] In contrast, the interior of Uranus is mainly composed of ices and rock.[11]cloud bands or storms associated with the other giants.[17] Terrestrial observers have seen signs of seasonal change and increased weathe
  37. 37. h from many thousand observations I knew they would retain. The sequel has shown that my surmises were well-founded, this proving to benew planet should be named after the father of Saturn.[31][35][36] In 1789, Bodes Royal Academy colleague Martin Klaproth named his new] In the Chinese, Japanese, Korean, and Vietnamese languages, the planets name is literally translated as the sky king star ( 天王星).[43][44e, at nearly the position predicted by Le Verrier.[47]oles towards the Sun is reversed. Each pole gets around 42 years of continuous sunlight, followed by 42 years of darkness.[49] Near the timedefinition currently endorsed by the International Astronomical Union, namely that the north pole of a planet or satellite shall be the pole which atellites, such as Titania and Oberon, may be visible.[56]The remainder of the non-ice mass (0.5 to 3.7 Earth masses) is accounted for by rocky material.[11]
  38. 38. 000 K.[57][58] The ice mantle is not in fact composed of ice in the conventional sense, but of a hot and dense fluid consisting of water, ammeric pressure equals 1 bar (100 kPa) is conditionally designated as a "surface". It has equatorial and polar radii of 25 559 ± 4 and 24 973 ± 20th of about 0.075 W/m2.[62] The lowest temperature recorded in Uranuss tropopause is 49 K (–224 °C), making Uranus the coldest planet i , the stratosphere, spanning altitudes between 50 and 4000 km and pressures of between 0.1 and 10–10 bar (10 kPa to 10 µPa), and the thar-infrared (IR) making Uranus aquamarine or cyan in color.[12] Methane molecules account for 2.3% of the atmosphere by molar fraction beand 170 K.[68][71] The most abundant hydrocarbons are methane, acetylene and ethane with mixing ratios of around 10−7 relative to hydrog00 km or two Uranian radii from the planet.[65][76] This extended corona is a unique feature of Uranus.[76] Its effects include a drag on smapieces of debris that formed as result of those impacts only few particles survived in a limited number of stable zones corresponding to preseo study the planets atmosphere. When their observations were analyzed, they found that the star had disappeared briefly from view five time is composed of minute particles of water ice from the surface of Mab that are small enough to scatter blue light.[86][88] In contrast, the plan µT).[89] In comparison, the magnetic field of Earth is roughly as strong at either pole, and its "magnetic equator" is roughly parallel with its gan astronomically rapid timescale of 100,000 years.[92] This may be the cause of the uniformly dark colouration of the moons and rings.[81] U to the north from the collar.[17] In all other respects Uranus looked like a dynamically dead planet in 1986. Unfortunately Voyager 2 arrived d
  39. 39. er altitude.[100] The lifetime of clouds spans several orders of magnitude. Some small clouds live for hours, while at least one southern cloud t −40° latitude range from 150 to 200 m/s. Since the collar obscures all clouds below that parallel, speeds between it and the southern pole a xtreme seasonal variations in its weather.[51][102] Determining the nature of this seasonal variation is difficult because good data on Uranus mmetrical around the solstices, which also indicates a change in the meridional albedo patterns.[102] Finally in the 1990s, as Uranus movedck polar clouds and haze may inhibit convection.[107] Now that the spring and autumn equinoxes are arriving on Uranus, the dynamics are cn to increase exponentially. The ice giants, with only a few Earth masses of nebular gas, never reached that critical point.[108][109][110] Recvely low albedos; ranging from 0.20 for Umbriel to 0.35 for Ariel (in green light).[17] The moons are ice-rock conglomerates composed of rouresonance with Titania.[116] he systems known rings, discovering two new ones.[17][81][117] It also studied the magnetic field, its irregular structure, its tilt and its uniqu
  40. 40. ge and increased weather activity in recent years as Uranus approached its equinox. The wind speeds on Uranus can reach 250 meters per
  41. 41. unded, this proving to be the Comet we have lately observed.ˈ‖n Klaproth named his newly discovered element "uranium" in support of Bodes choice.[37] Ultimately, Bodes suggestion became the most wking star ( 天王星).[43][44]rkness.[49] Near the time of the equinoxes, the Sun faces the equator of Uranus giving a period of day-night cycles similar to those seen onte shall be the pole which points above the invariable plane of the Solar System, regardless of the direction the planet is spinning.[53][54] A
  42. 42. consisting of water, ammonia and other volatiles.[11][58] This fluid, which has a high electrical conductivity, is sometimes called a water–amm5 559 ± 4 and 24 973 ± 20 km, respectively.[7] This surface will be used throughout this article as a zero point for altitudes.ranus the coldest planet in the Solar System.[12][62]Pa to 10 µPa), and the thermosphere/corona extending from 4,000 km to as high as 50,000 km from the surface.[12] There is no mesosphephere by molar fraction below the methane cloud deck at the pressure level of 1.3 bar (130 kPa); this represents about 20 to 30 times the cand 10−7 relative to hydrogen. The mixing ratio of carbon monoxide is similar at these altitudes.[68][71][73] Heavier hydrocarbons and carbonts include a drag on small particles orbiting Uranus, causing a general depletion of dust in the Uranian rings.[65] The Uranian thermosphere, s corresponding to present rings.[80][81] briefly from view five times both before and after it disappeared behind the planet. They concluded that there must be a ring system around t6][88] In contrast, the planets inner rings appear grey.[86] roughly parallel with its geographical equator.[90] The dipole moment of Uranus is 50 times that of Earth.[89][90] Neptune has a similarly dishe moons and rings.[81] Uranus has relatively well developed aurorae, which are seen as bright arcs around both magnetic poles.[76] Unlikenately Voyager 2 arrived during the height of the planets southern summer and could not observe the northern hemisphere. At the beginning
  43. 43. least one southern cloud may have persisted since Voyager flyby.[18][95] Recent observation also discovered that cloud features on Uranust and the southern pole are impossible to measure.[18] In contrast, in the northern hemisphere maximum speeds as high as 240 m/s are obuse good data on Uranuss atmosphere have existed for less than 84 years, or one full Uranian year. A number of discoveries have been ma1990s, as Uranus moved away from its solstice, Hubble and ground based telescopes revealed that the south polar cap darkened noticeablyanus, the dynamics are changing and convection can occur again.[95][107] point.[108][109][110] Recent simulations of planetary migration have suggested that both ice giants formed closer to the Sun than their presmerates composed of roughly fifty percent ice and fifty percent rock. The ice may include ammonia and carbon dioxide.[81][112]cture, its tilt and its unique corkscrew magnetotail caused by Uranuss sideways orientation.[89]
  44. 44. can reach 250 meters per second (900 km/h, 560 mph).[18]
  45. 45. estion became the most widely used, and became universal in 1850 when HM Nautical Almanac Office, the final holdout, switched from using similar to those seen on most of the other planets. Uranus reached its most recent equinox on December 7, 20net is spinning.[53][54] A different convention is sometimes used, in which a bodys north and south poles a
  46. 46. times called a water–ammonia ocean.[59] The bulk compositions of Uranus and Neptune are very different from those of J 2] There is no mesosphere. out 20 to 30 times the carbon abundance found in the Sun.[12][13][67] The mixing ratio[e] is much lower in the upper atmosphere ohydrocarbons and carbon dioxide have mixing ratios three orders of magnitude lower.[71] The abundance ratio of water is around 7×10−9.[72 e Uranian thermosphere, together with the upper part of the stratosphere, corresponds to the ionosphere of Uranus.[67] Observations showbe a ring system around the planet.[84] Later they detected four additional rings.[84] The rings were directly imaged when Voyage eptune has a similarly displaced and tilted magnetic field, suggesting that this may be a common feature of ice giamagnetic poles.[76] Unlike Jupiters, Uranuss aurorae seem to be insignificant for the energy balance of the planetary thermosphere.[79] isphere. At the beginning of the 21st century, when the northern polar region came into view, the Hubble Space Telescop
  47. 47. cloud features on Uranus have a lot in common with those on Neptune.[18] For example, the dark spots common on Neptune had never bes high as 240 m/s are observed near +50 degrees of latitude.[18][96][103]discoveries have been made. Photometry over the course of half a Uranian year (beginning in the 1950s) has shown regular variatio cap darkened noticeably (except the southern collar, which remained bright),[97] while the northern hemisphere demonstrated ino the Sun than their present positions, and moved outwards after formation, a hypothesis which is detailed in the Nice mo de.[81][112]
  48. 48. dout, switched from using Georgium Sid
  49. 49. er atmosphere oater is around 7×10−9.[72] Etha.[67] Observations showwhen Voyagey thermosphere.[79]
  50. 50. on Neptune had never beenn regular variatioemonstrated in