portia (moon)
{{Short description|Moon of Uranus}}
{{Infobox planet
| name = Portia
| image = Uranus-Portia-Cressida-Ophelia-NASA.gif
| mpc_name = Uranus XII
| pronounced = {{IPAc-en|ˈ|p|ɔər|ʃ|ə}}{{OED|Portia}}
| adjective = Portian {{IPAc-en|ˈ|p|ɔər|ʃ|ə|n}}
| discoverer = Stephen P. Synnott / Voyager 2
| discovered = January 3, 1986
| 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{{refn|group=note|Only two dimensions are known; the third dimension has been assumed to equal the smaller known dimension.}}
| surface_area = ~58 000 km2{{efn|name=calculated}}
| volume = {{val|1296800|14.8|u=km3|errend=%}}
| mass = {{val|1.1671|0.1730|u=kg|e=18}}
| density = ≥0.57 g/cm3
~0.90 g/cm3 (assumed)
| surface_grav = ~{{Gr|1.1671e-3|78}}–{{Gr|1.1671e-3|63}} m/s2{{efn|name=calculated}}
| escape_velocity = ~{{V2|1.1671e-3|78}}–{{V2|1.1671e-3|63}} km/s{{efn|name=calculated}}
| albedo = {{ubl|0.08 ± 0.01 |0.07}}
| single_temperature = ~64 K{{efn|name=calculated}}
}}
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. The moon is named after Portia, the heroine of William Shakespeare's play The Merchant of Venice. It is also designated Uranus XII.
Portia is the second-largest inner satellite of Uranus after Puck. The Portian orbit, which lies inside Uranus's 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, Cressida, Desdemona, Juliet, Rosalind, Cupid, Belinda, and Perdita. These satellites have similar orbits and photometric properties.
Little is known about Portia beyond its dimensions of about 156 × 126 km, orbit, and geometric albedo of about 0.08.
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. Its surface is grey in color. Observations with Hubble Space Telescope and large terrestrial telescopes found water ice absorption features in the spectrum of Portia. 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.{{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 |pages=119 |doi=10.3847/PSJ/ad3d55 |doi-access=free |arxiv=2404.06660 |bibcode=2024PSJ.....5..119B |issn=2632-3338}}
Gallery
File:Portia1.jpg|Portia seen on January 23, 1986.
See also
Notes
{{notes
| notes =
{{efn
| name = calculated
| Calculated on the basis of other parameters.
}}
}}
References
{{reflist
| refs =
{{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}}
{{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}}}}
{{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
}}
{{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
}}
{{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}}}}
{{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
}}
{{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/Page/Planets
| access-date = 2006-08-06
}}
{{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 = }}
{{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 |pages=115957 |doi=10.1016/j.icarus.2024.115957 |issn=0019-1035|arxiv=2401.04634 |bibcode=2024Icar..41115957F }}
}}
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)
{{Uranus}}
{{Moons of Uranus}}
{{Solar System moons (compact)}}
{{DEFAULTSORT:Portia (Moon)}}