Portia (moon)

Portia
Discovery
Discovered by	Stephen P. Synnott / Voyager 2
Discovery date	January 3, 1986
Designations
Designation	Uranus XII
Pronunciation	/ˈpɔːrʃə/
Adjectives	Portian /ˈpɔːrʃən/
Orbital characteristics
Semi-major axis	66,097.265 ± 0.050 km
Eccentricity	0.00005 ± 0.00008
Orbital period	0.5131959201 ± 0.0000000093 d
Average Orbital speed	9.37 km/s
Inclination	0.05908 ± 0.039° (to Uranus' equator)
Satellite of	Uranus
Group	ring shepherd
Physical characteristics
Dimensions	156 × 126 × 126 km
Mean radius	67.6 ± 4 km
Surface area	~57,000 km2
Volume	~1,300,000 km3
Mass	~1.7×1018 kg
Mean density	~1.3 g/cm3 (assumed)
surface gravity	~0.023 m/s2
escape velocity	~0.058 km/s
Rotation period	synchronous
Axial tilt	zero
Albedo	0.08 ± 0.01 ; 0.07;
Physics	~64 K

Short description: Moon of Uranus

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.^[7] The moon is named after Portia, the heroine of William Shakespeare's play The Merchant of Venice. It is also designated Uranus XII.^[8]

Portia is the second-largest inner satellite of Uranus after Puck. The Portian orbit, which lies inside Uranus' 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.

It heads a group of satellites called the Portia Group, which includes Bianca, Cressida, Desdemona, Juliet, Rosalind, Cupid, Belinda and Perdita.^[6] These satellites have similar orbits and photometric properties.^[6]

Little is known about Portia beyond its size of about 140 kilometres (87 mi) in diameter,^[3] orbit,^[2] and geometric albedo of about 0.08.^[6]

In the Voyager 2 images, 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.^[3] Its surface is grey in color.^[3] Observations with Hubble Space Telescope and large terrestrial telescopes found water ice absorption features in the spectrum of Portia.^[6]^[9]

Gallery

Portia seen on January 23, 1986.

References

Explanatory notes

↑ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 Calculated on the basis of other parameters.

Citations

↑ ^1.0 ^1.1 Portia (3rd ed.), Oxford University Press, September 2005, http://oed.com/search?searchType=dictionary&q=Portia (Subscription or UK public library membership required.)
↑ ^2.0 ^2.1 ^2.2 ^2.3 ^2.4 Jacobson, R. A. (1998). "The Orbits of the Inner Uranian Satellites From Hubble Space Telescope and Voyager 2 Observations". The Astronomical Journal 115 (3): 1195–1199. doi:10.1086/300263. Bibcode: 1998AJ....115.1195J.
↑ ^3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 ^3.6 Karkoschka, Erich (2001). "Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites". Icarus 151 (1): 69–77. doi:10.1006/icar.2001.6597. Bibcode: 2001Icar..151...69K.
↑ ^4.0 ^4.1 ^4.2 "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2008-10-24. http://ssd.jpl.nasa.gov/?sat_phys_par.
↑ ^5.0 ^5.1 Williams, Dr. David R. (2007-11-23). "Uranian Satellite Fact Sheet". NASA (National Space Science Data Center). http://nssdc.gsfc.nasa.gov/planetary/factsheet/uraniansatfact.html.
↑ ^6.0 ^6.1 ^6.2 ^6.3 ^6.4 Karkoschka, Erich (2001). "Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope". Icarus 151 (1): 51–68. doi:10.1006/icar.2001.6596. Bibcode: 2001Icar..151...51K.
↑ Smith, B. A. (January 16, 1986). "Satellites of Uranus". IAU Circular 4164. http://www.cbat.eps.harvard.edu/iauc/04100/04164.html#Item1. Retrieved 29 October 2011.
↑ "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21, 2006. http://planetarynames.wr.usgs.gov/Page/Planets.
↑ Dumas, Christophe; Smith, Bradford A.; Terrile, Richard J. (2003). "Hubble Space Telescope NICMOS Multiband Photometry of Proteus and Puck". The Astronomical Journal 126 (2): 1080–1085. doi:10.1086/375909. Bibcode: 2003AJ....126.1080D.

External links

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Original source: https://en.wikipedia.org/wiki/Portia (moon). Read more

[calculated-3] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 Calculated on the basis of other parameters.

[OED-1] 1.0 ^1.1 Portia (3rd ed.), Oxford University Press, September 2005, http://oed.com/search?searchType=dictionary&q=Portia (Subscription or UK public library membership required.)

[Jacobson_1998-2] 2.0 ^2.1 ^2.2 ^2.3 ^2.4 Jacobson, R. A. (1998). "The Orbits of the Inner Uranian Satellites From Hubble Space Telescope and Voyager 2 Observations". The Astronomical Journal 115 (3): 1195–1199. doi:10.1086/300263. Bibcode: 1998AJ....115.1195J.

[Karkoschka,_Voyager_2001-4] 3.0 ^3.1 ^3.2 ^3.3 ^3.4 ^3.5 ^3.6 Karkoschka, Erich (2001). "Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites". Icarus 151 (1): 69–77. doi:10.1006/icar.2001.6597. Bibcode: 2001Icar..151...69K.

[JPL-SSD-sat_phys-5] 4.0 ^4.1 ^4.2 "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2008-10-24. http://ssd.jpl.nasa.gov/?sat_phys_par.

[Williams_2007_nssdc-6] 5.0 ^5.1 Williams, Dr. David R. (2007-11-23). "Uranian Satellite Fact Sheet". NASA (National Space Science Data Center). http://nssdc.gsfc.nasa.gov/planetary/factsheet/uraniansatfact.html.

[Karkoschka,_Hubble_2001-7] 6.0 ^6.1 ^6.2 ^6.3 ^6.4 Karkoschka, Erich (2001). "Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope". Icarus 151 (1): 51–68. doi:10.1006/icar.2001.6596. Bibcode: 2001Icar..151...51K.

[IAUC_4164-8] Smith, B. A. (January 16, 1986). "Satellites of Uranus". IAU Circular 4164. http://www.cbat.eps.harvard.edu/iauc/04100/04164.html#Item1. Retrieved 29 October 2011.

[Gazetteer-9] "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21, 2006. http://planetarynames.wr.usgs.gov/Page/Planets.

[Dumas_Smith_et_al._2003-10] Dumas, Christophe; Smith, Bradford A.; Terrile, Richard J. (2003). "Hubble Space Telescope NICMOS Multiband Photometry of Proteus and Puck". The Astronomical Journal 126 (2): 1080–1085. doi:10.1086/375909. Bibcode: 2003AJ....126.1080D.

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v t e Moons of Uranus
Generally listed in increasing distance from Uranus
Inner	Rings of Uranus Cordelia Ophelia Bianca Cressida Desdemona Juliet Portia Rosalind Cupid Belinda Perdita Puck Mab
Major (spheroid)	Miranda Ariel Umbriel Titania Oberon
Outer (irregular)	Francisco Caliban Stephano Trinculo Sycorax Margaret Prospero Setebos Ferdinand
Geological features	Arielian Kachina Chasmata Yangoor Mirandian Verona Rupes Oberonian Hamlet Mommur Chasma Puckian Titanian Gertrude Messina Chasmata Ursula Rousillon Rupes Umbrielian Wunda Vuver Skynd

v t e Natural satellites of the Solar System
Planetary satellites	Terrestrial Martian Jovian Saturnian Uranian Neptunian
Dwarf-planet satellites	Plutonian Haumean Makemakean Eridian OR₁₀ Quaoaran Orcean
Minor-planet moons	Main belt binaries: Antiope Frostia Berna Tokai Ostro Balam Doppler Pauling Iwamoto Wolff Bettig Christophedumas Trojans: Patroclus–Menoetius Hektor–Skamandrios Iphthime Eurydamas TNOs: Huya Typhon–Echidna Lempo–Paha–Hiisi 2002 UX₂₅ Logos–Zoe Ceto–Phorcys Borasisi–Pabu Sila–Nunam Teharonhiawako–Sawiskera Salacia–Actaea 2002 WC₁₉ Altjira Varda–Ilmarë 2003 AZ₈₄ Gǃkúnǁʼhòmdímà–Gǃòʼé ǃHú Mors–Somnus Manwë–Thorondor ǂKá̦gára–ǃHãunu 2013 FY27
Ranked by size	Planetary-mass moon Ganymede largest: 5268 km / 0.413 Earths Titan Callisto Io Moon Europa Triton Titania Rhea Oberon Iapetus Charon Umbriel Ariel Dione Tethys Dysnomia Enceladus Miranda Vanth Proteus Mimas Ilmarë Nereid Hiʻiaka Actaea Hyperion ...
Discovery timeline Inner moons Irregular moons List Planetary-mass moons Naming Subsatellite Regular moons Trojan moons

Portia (moon)

Topic: Astronomy

Contents

Gallery

See also

References

External links

Discovery

Discovered by	Stephen P. Synnott / Voyager 2
Discovery date	January 3, 1986
Designations
Designation	Uranus XII
Pronunciation	/ˈpɔːrʃə/^[1]
Adjectives	Portian /ˈpɔːrʃən/^[1]
Orbital characteristics
Semi-major axis	66,097.265 ± 0.050 km^[2]
Eccentricity	0.00005 ± 0.00008^[2]
Orbital period	0.5131959201 ± 0.0000000093 d^[2]
Average Orbital speed	9.37 km/s^{[lower-alpha 1]}
Inclination	0.05908 ± 0.039° (to Uranus' equator)^[2]
Satellite of	Uranus
Group	ring shepherd
Physical characteristics
Dimensions	156 × 126 × 126 km^[3]
Mean radius	67.6 ± 4 km^[3]^[4]^[5]
Surface area	~57,000 km²^{[lower-alpha 1]}
Volume	~1,300,000 km³^{[lower-alpha 1]}
Mass	~1.7×10¹⁸ kg^{[lower-alpha 1]}
Mean density	~1.3 g/cm³ (assumed)^[4]
surface gravity	~0.023 m/s²^{[lower-alpha 1]}
escape velocity	~0.058 km/s^{[lower-alpha 1]}
Rotation period	synchronous^[3]
Axial tilt	zero^[3]
Albedo	0.08 ± 0.01 ^[6] 0.07^[4]^[5]
Physics	~64 K