Perdita (moon)

Infobox Planet
name = Perdita
bgcolour = #ffc0c0
discovery = yes
discoverer = Erich Karkoschka / "Voyager 2"
discovered = May 18, 1999 (in images dating back to January 18, 1986)
mean_orbit_radius = 76,417 ± 1 km
eccentricity = 0.0012 ± 0.0005
period = 0.638021 ± 0.000013 d
inclination = 0.0 ± 0.3° (to Uranus' equator)
satellite_of = Uranus
physical_characteristics = yes
dimensions = 30 × 30 × 30 kmcite journal|last=Karkoschka|first=Erich|authorlink=Erich Karkoschka|title=Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites|journal=Icarus|volume=151|pages=69–77|year=2001| doi=10.1006/icar.2001.6597|url=http://adsabs.harvard.edu/abs/2001Icar..151...69K]
mean_radius = 15 ± 3 km
surface_area = ~2,800 km²Calculated on the basis of other parameters]
volume = ~14,000 km³
mass = ~0.18e|17 kg
density = ~1.3 g/cm³ "assumed"
surface_grav = ~0.0047 m/s²
escape_velocity = ~0.011 km/s
rotation = synchronous
axial_tilt = zero
albedo = 0.08 ± 0.01cite journal|last=Karkoschka|first=Erich|authorlink=Erich Karkoschka|title=Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope|journal=Icarus|volume=151|pages=51–68|year=2001|doi=10.1006/icar.2001.6596| url=http://adsabs.harvard.edu/abs/2001Icar..151...51K]
single_temperature = ~64 K

Perdita "(pər'-di-tə," IPAEng|ˈpɝdɨtə) is an inner satellite of Uranus. Perdita's discovery was complicated. The first photographs 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.cite web|last=Karkoschka|first=Erich|authorlink=Erich Karkoschka|title=IAU Circular No. 7171|date=May 18 1999
url=http://cfa-www.harvard.edu/iauc/07100/07171.html|accessdate=2006-08-05] But because no further pictures could be taken to confirm its existence, it was officially demoted in 2001. [cite web|last=Foust|first= Jeff|title=Moon of Uranus is demoted|work=Spaceflight Now|date=December 31 2001|url=http://spaceflightnow.com/news/n0112/31uranusmoon/|accessdate=2006-08-05] 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.cite journal|first=Mark R.|last=Showalter|coauthors=Lissauer, Jack J.|title=The Second Ring-Moon System of Uranus: Discovery and Dynamics|journal=Science Express|date=2005-12-22|doi=10.1126/science.1122882| url=http://www.sciencemag.org/cgi/content/abstract/1122882v1|volume=311|pages=973|pmid=16373533] [cite web|last=Showalter|first=M. R.|coauthors=Lissauer, J. J.|title=IAU Circular No. 8194|date=September 3 2003|url=http://cfa-www.harvard.edu/iauc/08100/08194.html|accessdate=2006-08-05]

Following its discovery in 1999, Perdita was given the temporary designation of S/1986 U 10. 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.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/append7.html|accessdate=2006-08-05]

The moon orbits between Belinda and Puck. The abovementioned Hubble measurements prove that Perdita does not follow a direct Keplerian motion around Uranus. Instead, it is clearly caught in a 43:44 orbital resonance with the nearby moon Belinda. It is also close to an 8:7 resonance with Rosalind.

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

References

External links

[http://solarsystem.nasa.gov/planets/profile.cfm?Object=Ura_Perdita Perdita Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]

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