Perdita (moon)
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| Discovery | |||||||
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| Discovered by | Erich Karkoschka | ||||||
| Discovered in | May 18, 1999 (in images dating back to January 18, 1986) |
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| Orbital characteristics | |||||||
| Semi-major axis | 76,416 km | ||||||
| Eccentricity | 0.003 | ||||||
| Orbital period | 0.638 d | ||||||
| Inclination | 0.07° (to Uranus' equator) | ||||||
| Is a satellite of | Uranus | ||||||
| Physical characteristics | |||||||
| Mean diameter | ~26 km[1] (estimate) | ||||||
| Surface area | ~2,200 km2 (estimate) | ||||||
| Volume | ~98,000 km3 (estimate) | ||||||
| Mass | ~1.3×1016 kg (estimate) | ||||||
| Mean density | ~1.3 g/cm3 (estimate) | ||||||
| Surface gravity | ~0.0047 m/s2 (estimate) | ||||||
| Escape velocity | ~0.011 km/s (estimate) | ||||||
| Rotation period | synchronous (assumed) | ||||||
| Axial tilt | zero (assumed) | ||||||
| Albedo | 0.07 (assumed) | ||||||
| Surface temp. |
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| Atmospheric pressure | 0 kPa | ||||||
Perdita (pər'-di-tə, IPA: [ˈpərdɪtə]) is an inner satellite of Uranus. The size of Perdita is poorly known, but it is calculated to be about 26 km in diameter. The moon orbits between Belinda and Puck.
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.[2] But because no further pictures could be taken to confirm its existence, it was officially demoted in 2001.[3] 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.[1][4]
Following its discovery in 1999, Perdita was given the temporary designation of S/1986 U 10.[2] 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.[5]
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.[1]
[edit] References
- ^ a b c 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.
- ^ a b Karkoschka, Erich (May 18 1999). IAU Circular No. 7171. Retrieved on August 5, 2006.
- ^ Foust, Jeff (December 31 2001). Moon of Uranus is demoted. Spaceflight Now. Retrieved on August 5, 2006.
- ^ Showalter, M. R.; Lissauer, J. J. (September 3 2003). IAU Circular No. 8194. Retrieved on August 5, 2006.
- ^ Planet and Satellite Names and Discoverers. Gazetteer of Planetary Nomenclature. USGS Astrogeology (July 21 2006). Retrieved on August 5, 2006.
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| Inner | 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 |
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See also Rings of Uranus
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