Portia (moon)
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{{Infobox Planet
| name = Portia
| image = [[Image:Uranus-Portia-Cressida-Ophelia-NASA.gif|300px]]
| bgcolour = #ffc0c0
| discovery = yes
| discoverer = [[Stephen P. Synnott]] / ''[[Voyager 2]]''
| discovered = [[January 3]], [[1986]]
| semimajor = 66,097.265 ± 0.050 [[kilometre|km]]<ref name=Jacobson1998>{{cite journal|last=Jacobson|first=R.A.|title=The Orbits of the Inner Uranian Satellites From Hubble Space Telescope and Voyager2 Observations|journal=The Astronomical Journal|url=http://adsabs.harvard.edu/abs/1998AJ....115.1195J|year=1998|volume=115|pages=1195–1199|doi=10.1086/300263}}</ref>
| eccentricity = 0.00005 ± 0.00008<ref name=Jacobson1998/>
| period = 0.5131959201 ± 0.0000000093 d<ref name=Jacobson1998/>
| inclination = 0.05908 ± 0.039° (to Uranus' equator)<ref name=Jacobson1998/>
| satellite_of = [[Uranus (planet)|Uranus]]
| physical_characteristics = yes
| dimensions = 156 × 126 × 126 [[kilometre|km]]<ref name="Karkoschka2001b">{{cite journal|last=Karkoschka|first=Erich|authorlink=Erich Karkoschka|title=Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites|journal=Icarus|volume=151|pages=69–77|year=2001| doi=10.1006/icar.2001.6597|url=http://adsabs.harvard.edu/abs/2001Icar..151...69K}}</ref>
| mean_radius = 70 ± 4 [[kilometre|km]]<ref name="Karkoschka2001b"/>
| surface_area = ~57,000 [[square kilometre|km²]]<ref name=stub1>Calculated on the basis of other parameters</ref>
| volume = ~1,300,000 [[cubic kilometre|km³]]<ref name=stub1/>
| mass = ~1.7{{e|18}} [[kilogram|kg]]<ref name=stub1/>
| density = ~1.3 g/cm³ (assumed)
| surface_grav = ~0.023 [[Acceleration|m/s<sup>2</sup>]]<ref name=stub1/>
| escape_velocity = ~0.058 km/s km/s<ref name=stub1/>
| rotation = synchronous<ref name="Karkoschka2001b"/>
| axial_tilt = zero<ref name="Karkoschka2001b"/>
| albedo = 0.08 ± 0.01 <ref name="Karkoschka2001a">{{cite journal|last=Karkoschka|first=Erich|authorlink=Erich Karkoschka|title=Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope|journal=Icarus|volume=151|pages=51–68|year=2001| doi=10.1006/icar.2001.6596|url=http://adsabs.harvard.edu/abs/2001Icar..151...51K}}</ref>
| single_temperature = ~64 [[Kelvin|K]]
}}
'''Portia''' ''(por'-shə,'' {{IPAEng|ˈpɔrʃə}}) is an [[inner satellite]] of [[Uranus (planet)|Uranus]]. It was discovered from the images taken by ''[[Voyager 2]]'' on [[1986-01-03]], and was given the temporary designation '''S/1986 U 1'''.<ref>{{cite web|last=Smith|first=B. A.|title=IAU Circular No. 4164|date=[[January 16]] 1986|url=http://cfa-www.harvard.edu/iauc/04100/04164.html#Item1|accessdate=2006-08-06}}</ref> The moon is named after [[Portia (Merchant of Venice)|Portia]], the heroine of [[William Shakespeare]]'s play ''[[The Merchant of Venice]]''. It is also designated '''Uranus XII'''.<ref name="Gazetteer">{{cite web|title=Planet and Satellite Names and Discoverers|work=Gazetteer of Planetary Nomenclature|publisher=USGS Astrogeology|date=[[July 21]] 2006|url=http://planetarynames.wr.usgs.gov/append7.html|accessdate=2006-08-06}}</ref>
Portia is the second-largest inner satellite of [[uranus (planet)|Uranus]] after [[puck (moon)|Puck]]. The Portian orbit, which lies inside Uranus' synchronous [[orbit]]al radius, is slowly decaying due to [[tidal deceleration]]. The moon will one day either break up into a [[planetary ring]] or hit Uranus.
It heads a group of satellites called '''Portia Group''', which includes [[Bianca (moon)|Bianca]], [[Cressida (moon)|Cressida]], [[Desdemona (moon)|Desdemona]], [[Juliet (moon)|Juliet]], [[Rosalind (moon)|Rosalind]], [[Cupid (moon)|Cupid]], [[Belinda (moon)|Belinda]] and [[Perdita (moon)|Perdita]].<ref name="Karkoschka2001a"/> These satellites have similar orbits and photometric properties.<ref name="Karkoschka2001a"/>
Little is known about Portia beyond its size of about 140 km,<ref name="Karkoschka2001b"/> orbit,<ref name=Jacobson1998/> and geometric [[albedo]] of about 0.08.<ref name="Karkoschka2001a"/>
In the [[Voyager 2]] images, Portia appears as an elongated object whose major axis points towards [[uranus (planet)|Uranus]]. The ratio of axises of the Portia's [[prolate spheroid]] is 0.8 ± 0.1.<ref name="Karkoschka2001b"/> Its surface is grey in color.<ref name="Karkoschka2001b"/> Observations with [[Hubble Space Telescope]] and large terrestrial telescopes found water ice absorption features in the spectrum of Portia.<ref name="Karkoschka2001a"/><ref name=Dumas2003>{{cite journal|last=Dumas|first=Christophe|coaurhors=Smith, Bradford A.; and Terrile, Richard J.|title=Hubble Space Telescope NICMOS Multiband Photometry of Proteus and Puck|journal=Astronomical Journal|year=2003|volume=126|pages=1080–1085|doi=10.1086/375909|url=http://adsabs.harvard.edu/abs/2003AJ....126.1080D}}</ref>
==References==
{{reflist}}
==External links==
*[http://solarsystem.nasa.gov/planets/profile.cfm?Object=Ura_Portia Portia Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
{{Uranus}}
[[Category:Uranus' moons]]
[[bs:Portija (mjesec)]]
[[bg:Порция (спътник)]]
[[cs:Portia (měsíc)]]
[[cy:Portia (lloeren)]]
[[da:Portia (måne)]]
[[de:Portia (Mond)]]
[[fr:Portia (lune)]]
[[hr:Porcija]]
[[it:Porzia (astronomia)]]
[[ht:Pòtya]]
[[la:Portia (satelles)]]
[[lt:Portija (palydovas)]]
[[nl:Portia (maan)]]
[[ja:ポーシャ (衛星)]]
[[nds:Portia (Maand)]]
[[pl:Porcja (księżyc)]]
[[ru:Порция (спутник)]]
[[simple:Portia (moon)]]
[[sk:Portia (mesiac)]]
[[sl:Porcija (luna)]]
[[fi:Portia]]
[[sv:Portia]]
[[uk:Порція (супутник)]]
[[zh:天卫十二]]