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Perdita (moon)

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Discovered byErich Karkoschka / Voyager 2
Discovery timeMay 18, 1999 (in images dating back to January 18, 1986)
Avgdistance from the center of its orbital path76,417 ± 1 km[1]
How egg-shaped its orbit is
0.0012 ± 0.0005[1]
How long it takes to complete an orbit0.638021 ± 0.000013 d[1]
Angle above the reference plane
0.0 ± 0.3° (to Uranus' equator)[1]
What it orbitsUranus
Size and Other Qualities
Measures30 × 30 × 30 km[1]
Average distance from its center to its surface15 ± 3 km[1]
Area of its surface~2,800 km²[2]
Volume inside it~14,000 km³[2]
Mass~0.18×1017 kg[2]
Average density~1.3 g/cm³ assumed
Gravity at its surface~0.0047 m/s2[2]
Slowest speed able to escape into space
("escape velocity")
~0.011 km/s[2]
How long it takes to turn around one timesynchronous[1]
Angle at which it turns
(in relation to its orbit)
How much light it reflects0.08 ± 0.01[3]
Avg. surface temp.~64 K[2]

Perdita is a closer moon to Uranus. Perdita's discovery was not simple. The first pictures of Perdita were taken by the Voyager 2 spacecraft in 1986, but it was not recognized from the photographs for more than a decade. In 1999, the moon was noticed by Erich Karkoschka and reported.[1][4] But because no further pictures could be taken to confirm its existence, it was thought to be non-existent in 2001.[5] However, in 2003, pictures taken by the Hubble Space Telescope managed to pick up an object where Perdita was supposed to be, finally confirming its existence.[6][7]

Following its discovery in 1999, Perdita was given the designation of S/1986 U 10.[4] It was named after the daughter of Leontes and Hermione in William Shakespeare's play The Winter's Tale. The moon is also designated Uranus XXV.[8]

Perdita belongs to Portia Group of moons, which also includes Bianca, Cressida, Desdemona, Portia, Juliet, Cupid, Rosalind and Belinda.[3] These moons have similar orbits and photometric properties.[3] Unfortunately, other than its orbit,[1][6] radius of 15 km[1] and geometric albedo of 0.08[3] almost nothing is known about it.


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Karkoschka, Erich (2001). "Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites". Icarus 151: 69–77. doi:10.1006/icar.2001.6597 . 
  2. 2.0 2.1 2.2 2.3 2.4 2.5 Calculated on the basis of other parameters
  3. 3.0 3.1 3.2 3.3 Karkoschka, Erich (2001). "Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope". Icarus 151: 51–68. doi:10.1006/icar.2001.6596 . 
  4. 4.0 4.1 Karkoschka, Erich (May 18 1999). "IAU Circular No. 7171". Retrieved 2006-08-05. 
  5. Foust, Jeff (December 31 2001). "Moon of Uranus is demoted". Spaceflight Now. Retrieved 2006-08-05. 
  6. 6.0 6.1 Showalter, Mark R.; Lissauer, Jack J. (2005-12-22). "The Second Ring-Moon System of Uranus: Discovery and Dynamics". Science Express. doi:10.1126/science.1122882 . 
  7. Showalter, M. R.; Lissauer, J. J. (September 3 2003). "IAU Circular No. 8194". Retrieved 2006-08-05. 
  8. "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21 2006. Retrieved 2006-08-05. 

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