Perdita (moon)

Perdita

Discovery
Discovered by	Erich Karkoschka / Voyager 2
Discovery date	May 18, 1999 (in images dating back to January 18, 1986)
Designations
Designation	Uranus XXV
Pronunciation	/ˈpɜːrdɪtə/[1]
Adjectives	Perditean /pɜːrdɪˈtiːən/[2]
Orbital characteristics
Mean orbit radius	76,417 ± 1 km[3]
Eccentricity	0.0012 ± 0.0005[3]
Orbital period	0.638021 ± 0.000013 d[3]
Inclination	0.0 ± 0.3° (to Uranus' equator)[3]
Satellite of	Uranus
Physical characteristics
Dimensions	30 × 30 × 30 km[3]
Mean radius	15 ± 3 km[3]
Surface area	~2,800 km² [a]
Volume	~14,000 km³ [a]
Mass	~0.18×1017 kg[a]
Mean density	~1.3 g/cm³ (assumed)
Surface gravity	~0.0047 m/s² [a]
Escape velocity	~0.011 km/s[a]
Rotation period	synchronous[3]
Axial tilt	zero[3]
Albedo	0.08 ± 0.01[4]
Temperature	~64 K[a]

Perdita /ˈpɜːrdɪtə/ 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.^[3][5] But because no further pictures could be taken to confirm its existence, it was officially demoted in 2001.^[6] 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.^[7][8]

Following its discovery in 1999, it was given the temporary designation of S/1986 U 10.^[5] It was named Perdita (Latin for 'lost') after the daughter of Leontes and Hermione in William Shakespeare's play The Winter's Tale. The moon is also designated Uranus XXV.^[9]

Discovery image of Perdita taken by Voyager 2 on 23 January 1986. The location of the moon is indicated by the arrow on the upper right.

The moon orbits between Belinda and Puck. The above-mentioned 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.^[3][7]

Perdita belongs to the Portia group of satellites, which also includes Bianca, Cressida, Desdemona, Portia, Juliet, Cupid, Rosalind and Belinda.^[4] These satellites have similar orbits and photometric properties.^[4] Little is known about Perdita apart from its orbit,^[3][7] radius of 15 km^[3] and geometric albedo of 0.08.^[4]

See also

• Moons of Uranus

References

Explanatory notes

Citations

Sources

• 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.
• 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.
• Green, Daniel W. E. (May 18, 1999). "S/1986 U 10". IAU Circular. 7171. ISSN 0081-0304. Retrieved 2012-01-26.
• Foust, Jeff (December 31, 2001). "Moon of Uranus is demoted". Spaceflight Now. Retrieved 2012-01-26.
• Showalter, Mark R.; Lissauer, Jack J. (2006-02-17). "The Second Ring-Moon System of Uranus: Discovery and Dynamics". Science. 311 (5763): 973–977. Bibcode:2006Sci...311..973S. doi:10.1126/science.1122882. PMID 16373533.
• Green, Daniel W. E. (September 3, 2003). "Satellites of Uranus". IAU Circular. 8194. ISSN 0081-0304. Retrieved 2012-01-26.
• USGS/IAU (July 21, 2006). "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. Retrieved 2012-01-26.

External links

• Uranus 'Loses' a Moon: The 'New' Official Moon Count of the Solar System (Archived), Melanie Melton, The Planetary Society, 20 December 2001