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Line 1: − : ''This article is about the [[moon]] of [[Uranus]]. For other uses, see [[Ariel (disambiguation)]].''+ − {{Planet − |name=Ariel − |image=Ariel color.jpg − |caption=High-resolution color image of Ariel, taken by [[Voyager 2]] − |date=October 24, 1851<ref name=usgs>"[http://planetarynames.wr.usgs.gov/append7.html Gazetteer of Planetary Nomenclature: Planetary Body Names and Discoverers]." US Geological Survey, Jennifer Blue, ed. March 31, 2008. Accessed April 17, 2008.</ref><ref name=Lassell1>Lassell, W. "[http://adsabs.harvard.edu//full/seri/AJ.../0002//0000070.000.html Letter to the Editor re Discovery of Two Satellites of Uranus]." ''Astron. J.'' 2:70, 1851. Accessed June 13, 2008.</ref><ref name=Lassell2>Lassell, William. "[http://adsabs.harvard.edu//full/seri/AN.../0033//0000136.000.html Entdeckung von 2 neuen Uranus Trabanten]." ''Astronomische Nachrichten'', 33:259-260, 1852. Accessed June 13, 2008</ref> − |discname=William Lassell<ref name=usgs/><ref name=Lassell1/><ref name=Lassell2/><ref name=Hamilton>Hamilton, Calvin J. "[http://www.solarviews.com/eng/ariel.htm Entry for Ariel]." ''Views of the Solar System'', 2001. Accessed June 13, 2008.</ref> − |origname=A sylph in ''The Rape of the Lock'' by [[Alexander Pope]];<ref name=usgs/><ref name=Lassell3>Lassell, William. "[http://articles.adsabs.harvard.edu//full/1852AN.....34..325./0000169.000.html Beobachtungen der Uranus-Satelliten]." ''Astronomische Nachrichten'' 34:325-328, 1852. Accessed June 12, 2008.</ref> a sprite in ''[[The Tempest]]'' by [[William Shakespeare]]<ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/ariel.html Entry for Ariel]." ''The <s>Nine</s> 8 Planets'', December 11, 2004. Accessed June 13, 2008.</ref> − |primary=Uranus − |order=15 − |periapsis=184,525 km<ref name=calc>Calculated</ref> − |apoapsis=197,515 km<ref name=calc/> − |semimajor=191,020 km<ref name=uranussatfact>Williams, David R. "[http://nssdc.gsfc.nasa.gov/planetary/factsheet/uraniansatfact.html Uranian Satellite Fact Sheet]." National Space Science Data Center, [[National Aeronautics and Space Administration|NASA]], November 23, 2007. Accessed June 13, 2008.</ref> − |eccentricity=0.0034<ref name=uranussatfact/> − |sidereal=2.520379 da<ref name=uranussatfact/> − |orbitspeed=5.52 km/s<ref name=Hamilton/> − |inclination=0.31°<ref name=uranussatfact/><ref name=Hamilton/> − |siderealday=2.520379 da<ref name=uranussatfact/><ref name=Hamilton/> − |rotatespeed=16.7 m/s<ref name=calc/> − |axialtilt=0°<ref name=uranussatfact/> − |mass=1.35 * 10<sup>21</sup> kg<ref name=uranussatfact/> − |density=1,670 kg/m³<ref name=uranussatfact/> − |meanradius=578.9 km<ref name=Hamilton/> − |surfacegrav=0.27 m/s²<ref name=calc/> − |escapespeed=0.541 km/s<ref name=Hamilton/> − |surfacearea=4,211,310 km²<ref name=calc/> − |meantemp=58 K<ref name=Tittemore>Tittemore, William C. "[http://adsabs.harvard.edu/abs/1990Icar...87..110T Tidal Heating of Ariel]." ''Icarus'' 87:110-139, September 1990. {{doi|10.1016/0019-1035(90)90024-4}} Accessed June 13, 2008.</ref> − |composition=Water ice and rock<ref name=Britannica>Ingersoll, Andrew P. "[http://www.britannica.com/eb/article-9009421 Ariel]." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 13 June 2008.</ref> − |color=Deep gray-purple − |albedo=0.34<ref name=Hamilton/> − }}'''Ariel''' or '''Uranus I''' is the fifteenth [[moon]] of [[Uranus]] in the order of distance, the third moon of Uranus to be discovered, and the third heaviest. − − == Discovery and naming == − [[William Lassell]] discovered Ariel and its next companion, [[Umbriel]], on October 24, 1851, and reported his findings after observing these two satellites on three more occasions.<ref name=Lassell1/><ref name=Lassell2/> − − The name ''Ariel'', suggested by Sir [[John Herschel]] at Lassell's request, is the name of a sylph in Alexander Pope's poem ''The Rape of the Lock''.<ref name=Lassell3/> It is also the name of a sprite and servant to Prospero in William Shakespeare's play ''The Tempest''.<ref name=Arnett/> − − == Orbital characteristics == − Ariel is in a slightly eccentric orbit around Uranus at an average distance of 191,020 km. Its sidereal month is about 2.52 Earth days. The orbit of Ariel is only slightly inclined from the equator of Uranus but is severely inclined to the ecliptic. − − Tittemore<ref name=Tittemore/> suggests that Ariel was once in a 4:1 orbital resonance with [[Titania]]. If it was, it is no longer in such a resonance. For this reason, some astronomers suggest that Ariel was much hotter in the past than it is today.<ref name=Arnett/> − − === Transits of Uranus === − [[Image:Ariel transit.jpg|thumb|150px|left|Uranus with Ariel (white) and its shadow (black) at upper right]] − Ariel is rarely able to transit the surface of Uranus in such a manner as to cast a shadow on it. This is because Ariel, like all the moons of Uranus, is in an orbit with an almost perpendicular inclination to the ecliptic. Such transits usually occur only in years close to Uranian equinoxes. One such transit occurred on July 26, 2006; the [[Hubble Space Telescope]] captured that transit on the image at the left. The white dot in the upper-right-hand quadrant of Uranus is Ariel itself; the black dot is its shadow.<ref name=transit>"[http://hubblesite.org/newscenter/archive/releases/2006/42/image/a Hubble Captures a Rare Eclipse on Uranus]." News Release STScI-2006-42, August 31, 2006. Accessed June 13, 2008.</ref> − − == Rotational characteristics == − Ariel is in [[tidal lock]] with Uranus. − − == Physical characteristics == − Ariel is composed of rock and [[water]] ice. Some authorities suggest that Ariel might also contain ices of [[ammonia]], [[methane]], or [[carbon monoxide]].<ref name=Hamilton/> − − === Surface === − The surface of Ariel has relatively few impact craters, and also a system of interconnecting valleys and rifts.<ref name=Arnett/><ref name=Hamilton/> Some of these valleys bear signs of smoothing by a fluid. Liquid water would not smooth the valley floors in this fashion, and for this reason astronomers suspect that the fluid might have been liquid ammonia or methane. Other valleys and canyons appear to have formed by faulting. − − Most of the surface of Ariel appears relatively "young" by [[uniformitarianism|uniformitarian]] standards. In fact, some authorities say that Ariel's surface is the youngest such surface among the major moons of Uranus.<ref name=Britannica/> − − == Problems for uniformitarian theories == − Ariel poses the same problem for uniformitarian astronomy as do all the other moons of Uranus: its orbit is inclined severely to the ecliptic, though not to Uranus' own equator. How the Uranian system came to have such an inclination has never been explained. − − == Observation and Exploration == − Ariel is visible from Earth with any telescope having an aperture of 30 cm or more. − − The one spacecraft to visit Ariel was [[Voyager 2]]. Voyager approached to within 127,000 km of Ariel on January 24, 1986, and took several images.<ref name=Voyager1>"[http://pds-rings.seti.org/voyager/mission/#v2uenc Voyager Mission Description: Voyager 2 Uranus Encounter]." February 19, 1997. Accessed June 13, 2008.</ref><ref name=Smith>Smith, B.A., Soderblom, L.A., Beebe, R., ''et al.'' "[http://adsabs.harvard.edu/abs/1986Sci...233...43S Voyager 2 in the Uranian system - Imaging science results]." ''Science'' 233:43-64, July 4, 1986. Accessed June 13, 2008.</ref> − − Today the [[Hubble Space Telescope]] is the most powerful telescope to take images of Ariel. − − == References == − {{reflist|2}} − − {{Solarsystem}} −
Redirecting to Hagger
#REDIRECT [[Hagger]]
[[Category:Astronomy]]