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# Perdita (moon)

Perdita
Discovery
Discovered byErich Karkoschka / Voyager 2
Discovery timeMay 18, 1999 (in images dating back to January 18, 1986)
Orbit
Avgdistance from the center of its orbital path76,417 ± 1 km[1]
How egg-shaped its orbit is
("eccentricity")
0.0012 ± 0.0005[1]
How long it takes to complete an orbit0.638021 ± 0.000013 d[1]
Angle above the reference plane
("inclination")
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)
zero[1]
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.

## References

1. Calculated on the basis of other parameters
2. Karkoschka, Erich (May 18 1999). "IAU Circular No. 7171". Retrieved 2006-08-05.
3. Foust, Jeff (December 31 2001). "Moon of Uranus is demoted". Spaceflight Now. Retrieved 2006-08-05.
4. Showalter, Mark R.; Lissauer, Jack J. (2005-12-22). "The Second Ring-Moon System of Uranus: Discovery and Dynamics". Science Express. .
5. Showalter, M. R.; Lissauer, J. J. (September 3 2003). "IAU Circular No. 8194". Retrieved 2006-08-05.
6. "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21 2006. Retrieved 2006-08-05.