View source for Portia (moon)

{{Short description|Moon of Uranus}}
{{Infobox planet
| name             = Portia
| image            = Portia1.jpg
| mpc_name         = Uranus XII
| pronounced       = {{IPAc-en|ˈ|p|ɔər|ʃ|ə}}<ref name=OED>{{OED|Portia}}</ref>
| adjective        = Portian {{IPAc-en|ˈ|p|ɔər|ʃ|ə|n}}<ref name=OED/>
| discoverer       = [[Stephen P. Synnott]] / ''[[Voyager 2]]''
| discovered       = January 3, 1986
| orbit_ref        = <ref name="Jacobson 1998" />
| semimajor        = 66,097.265 ± 0.050 km
| eccentricity     = 0.00005 ± 0.00008
| period           = 0.5131959201 ± 0.0000000093 d
| avg_speed        = 9.37 km/s{{efn|name=calculated}}
| inclination      = 0.05908 ± 0.039° (to Uranus's equator)
| satellite_of     = [[Uranus]]
| group            = [[ring shepherd]]
| dimensions       = 156 × 126 × 126 km<ref name="Karkoschka, Voyager 2001" />{{refn|group=note|Only two dimensions are known; the third dimension has been assumed to equal the smaller known dimension.}}
| surface_area     = ~58 000 km<sup>2</sup>{{efn|name=calculated}}
| volume           = 1296800 km{{sup|3}} ± 14.8%<ref name = "FrenchEtAl2024"/>
| mass             = {{val|1.1671|0.1730|u=kg|e=18}}<ref name = "FrenchEtAl2024"/>
| density          = {{val|0.5|-|1.2|u=g/cm3}}<ref name="French & Showalter 2012"/><br />{{val|0.9|u=g/cm3}} (assumed)<ref name = "FrenchEtAl2024"/>
| rotation         = synchronous<ref name="Karkoschka, Voyager 2001" />
| axial_tilt       = zero<ref name="Karkoschka, Voyager 2001" />
| albedo           = {{ubl|0.08 ± 0.01 <ref name="Karkoschka, Hubble 2001" />|0.07<ref name="JPL-SSD-sat_phys" /><ref name="Williams 2007 nssdc" />}}
}}

'''Portia''' is an [[inner satellite]] of [[Uranus]]. It was discovered from the images taken by ''[[Voyager 2]]'' on 3 January 1986, and was given the temporary designation '''S/1986 U 1'''.<ref name="IAUC 4164" /> 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" />

Portia is the second-largest inner satellite of Uranus after [[Puck (moon)|Puck]]. The Portian orbit, which lies inside Uranus's [[Synchronous orbit|synchronous orbital radius]], is slowly decaying due to [[tidal deceleration]]. The moon will one day either break up into a [[planetary ring]] or hit Uranus.{{cn|date=July 2024}}

It is the namesake of a group of satellites called the '''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="Karkoschka, Hubble 2001" /> These satellites have similar orbits and photometric properties.<ref name="Karkoschka, Hubble 2001" />

Little is known about Portia beyond its dimensions of about {{cvt|156 × 126|km|mi}},<ref name="Karkoschka, Voyager 2001" /> orbit,<ref name="Jacobson 1998" /> and geometric [[albedo]] of about 0.08.<ref name="Karkoschka, Hubble 2001" />

In ''Voyager 2'' imagery, Portia appears as an elongated object whose major axis points towards Uranus. The ratio of axes of the Portia's [[prolate spheroid]] is 0.8 ± 0.1.<ref name="Karkoschka, Voyager 2001" /> Its surface is grey in color.<ref name="Karkoschka, Voyager 2001" /> Observations with [[Hubble Space Telescope]] and large terrestrial telescopes found water ice absorption features in the spectrum of Portia.<ref name="Karkoschka, Hubble 2001" /><ref name="Dumas Smith et al. 2003" /> Observations with [[James Webb Space Telescope]] have also found evidence for water ice or hydrated minerals on Portia's surface, and have also confirmed that Portia group members Juliet, Belinda, and Cressida have roughly similar spectra to Portia.<ref>{{Cite journal |last1=Belyakov |first1=Matthew |last2=Davis |first2=M. Ryleigh |last3=Milby |first3=Zachariah |last4=Wong |first4=Ian |last5=Brown |first5=Michael E. |date=2024-05-01 |title=JWST Spectrophotometry of the Small Satellites of Uranus and Neptune |journal=The Planetary Science Journal |volume=5 |issue=5 |page=119 |doi=10.3847/PSJ/ad3d55 |doi-access=free |arxiv=2404.06660 |bibcode=2024PSJ.....5..119B |issn=2632-3338}}</ref>

== Gallery ==
<gallery class="center">
File:Portia1.jpg|Portia seen on January 23, 1986.
File:Uranus-Portia-Cressida-Ophelia-NASA.gif|NASA image of three minor moons of Uranus: Portia, [[Cressida (moon)|Cressida]] and [[Ophelia (moon)|Ophelia]].
</gallery>

== See also ==

* [[Moons of Uranus]]

== Notes ==
{{notes
| notes =

{{efn
| name = calculated
| Calculated on the basis of other parameters.
}}

}}

== References ==

{{reflist
| refs =

<ref name="Jacobson 1998">
{{cite journal| doi = 10.1086/300263| last1 = Jacobson| first1 = R. A.| year = 1998| title = The Orbits of the Inner Uranian Satellites From Hubble Space Telescope and Voyager 2 Observations| journal = The Astronomical Journal| volume = 115| issue = 3| pages = 1195–1199| bibcode = 1998AJ....115.1195J| doi-access = free}}
</ref>

<ref name="Karkoschka, Voyager 2001">
{{cite journal| doi = 10.1006/icar.2001.6597| last = Karkoschka| first = Erich| author-link = Erich Karkoschka| year = 2001| title = Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites| journal = Icarus| volume = 151| issue = 1| pages = 69–77| bibcode = 2001Icar..151...69K| ref = {{sfnRef|Karkoschka, Voyager|2001}}}}
</ref>

<ref name="JPL-SSD-sat_phys">
{{cite web
| title = Planetary Satellite Physical Parameters
| date = 2008-10-24
| publisher = [[JPL]] (Solar System Dynamics)
| url = http://ssd.jpl.nasa.gov/?sat_phys_par
| access-date = 2008-12-12
}}
</ref>

<ref name="Williams 2007 nssdc">
{{cite web
| last = Williams
| first = Dr. David R.
| date = 2007-11-23
| title = Uranian Satellite Fact Sheet
| publisher = [[NASA]] (National Space Science Data Center)
| url = http://nssdc.gsfc.nasa.gov/planetary/factsheet/uraniansatfact.html
| access-date = 2008-12-12
}}
</ref>

<ref name="Karkoschka, Hubble 2001">
{{cite journal| doi = 10.1006/icar.2001.6596| last = Karkoschka| first = Erich| author-link = Erich Karkoschka| year = 2001| title = Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope| journal = Icarus| volume = 151| issue = 1| pages = 51–68| bibcode = 2001Icar..151...51K| ref = {{sfnRef|Karkoschka, Hubble|2001}}}}
</ref>

<ref name="IAUC 4164">
{{cite journal
| last = Smith
| first = B. A.
| title = Satellites of Uranus
| journal = IAU Circular
| volume = 4164
| date = January 16, 1986
| url = http://www.cbat.eps.harvard.edu/iauc/04100/04164.html#Item1
| access-date = 29 October 2011
}}
</ref>

<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 = https://planetarynames.wr.usgs.gov/Page/Planets
| access-date = 2006-08-06
}}
</ref>

<ref name="Dumas Smith et al. 2003">
{{cite journal| last1 = Dumas| first1 = Christophe| last2 = Smith| first2 = Bradford A.| last3 = Terrile| first3 = Richard J.| year = 2003| title = Hubble Space Telescope NICMOS Multiband Photometry of Proteus and Puck| journal = [[The Astronomical Journal]]| volume = 126| issue = 2| pages = 1080–1085| doi = 10.1086/375909| bibcode = 2003AJ....126.1080D| ref = {{sfnRef|Dumas Smith et al.|2003}}| doi-access = }}
</ref>

<ref name="French & Showalter 2012">{{Cite journal |last1=French |first1=Robert S. |last2=Showalter |first2=Mark R. |date=August 2012 |title=Cupid is Doomed: An Analysis of the Stability of the Inner Uranian Satellites |journal=Icarus |volume=220 |issue=2 |pages=911–921 |doi=10.1016/j.icarus.2012.06.031|arxiv=1408.2543
|bibcode=2012Icar..220..911F }}
</ref>

<ref name = "FrenchEtAl2024">
{{Cite journal |last1=French |first1=Richard G. |last2=Hedman |first2=Matthew M. |last3=Nicholson |first3=Philip D. |last4=Longaretti |first4=Pierre-Yves |last5=McGhee-French |first5=Colleen A. |date=2024-03-15 |title=The Uranus system from occultation observations (1977–2006): Rings, pole direction, gravity field, and masses of Cressida, Cordelia, and Ophelia |url=https://www.sciencedirect.com/science/article/pii/S0019103524000150 |journal=Icarus |volume=411 |article-number=115957 |doi=10.1016/j.icarus.2024.115957 |issn=0019-1035|arxiv=2401.04634 |bibcode=2024Icar..41115957F }}
</ref>

}}

== External links ==
* [https://web.archive.org/web/20070801203928/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Ura_Portia Portia Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.dtm.ciw.edu/users/sheppard/satellites/urasatdata.html Uranus' Known Satellites] (by [[Scott S. Sheppard]])

{{Moons of Uranus}}
{{Uranus}}
{{Solar System moons (compact)}}

{{DEFAULTSORT:Portia (Moon)}}
[[Category:Moons of Uranus]]
[[Category:Astronomical objects discovered in 1986|19860103]]
[[Category:Moons with a prograde orbit]]
[[Category:The Merchant of Venice]]