Portia (moon)
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Portia Moon
Discovered byStephen P. Synnott / Voyager 2
Discovery dateJanuary 3, 1986
Orbital characteristics
66,097.265 ± 0.050 km[1]
Eccentricity0.00005 ± 0.00008[1]
0.5131959201 ± 0.0000000093 d[1]
9.37 km/s[a]
Inclination0.05908 ± 0.039° (to Uranus' equator)[1]
Satellite ofUranus
Physical characteristics
Dimensions156 × 126 × 126 km[2]
Mean radius
67.6 ± 4 km[2][3][4]
~57,000 km²[a]
Volume~1,300,000 km³[a]
Mean density
~1.3 g/cm³ (assumed)[3]
~0.023 m/s2[a]
~0.058 km/s[a]
Temperature~64 K

Portia ( POR-sh?) 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.[6] The moon is named after Portia, the heroine of William Shakespeare's play The Merchant of Venice. It is also designated Uranus XII.[7]

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.[5] These satellites have similar orbits and photometric properties.[5]

Little is known about Portia beyond its size of about 140 km,[2] orbit,[1] and geometric albedo of about 0.08.[5]

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.[2] Its surface is grey in color.[2] Observations with Hubble Space Telescope and large terrestrial telescopes found water ice absorption features in the spectrum of Portia.[5][8]

See also


Explanatory notes

  1. ^ a b c d e f Calculated on the basis of other parameters.


  1. ^ a b c d e 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. Bibcode:1998AJ....115.1195J. doi:10.1086/300263.
  2. ^ a b c d e f g 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. Bibcode:2001Icar..151...69K. doi:10.1006/icar.2001.6597.
  3. ^ a b c "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 2008-10-24. Retrieved .
  4. ^ a b Williams, Dr. David R. (2007-11-23). "Uranian Satellite Fact Sheet". NASA (National Space Science Data Center). Retrieved .
  5. ^ a b c d e Karkoschka, Erich (2001). "Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope". Icarus. 151 (1): 51-68. Bibcode:2001Icar..151...51K. doi:10.1006/icar.2001.6596.
  6. ^ Smith, B. A. (January 16, 1986). "Satellites of Uranus". IAU Circular. 4164. Retrieved 2011.
  7. ^ "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21, 2006. Retrieved .
  8. ^ 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. Bibcode:2003AJ....126.1080D. doi:10.1086/375909.

External links

  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.



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