Cressida (moon)

Cressida is a closer moon to Uranus. It was found from the images taken by Voyager 2 on 1986-01-09, and was given the designation S/1986 U 3.[5] It was named after the Trojan daughter of Calchas, a tragic heroine who appears in William Shakespeare's play Troilus and Cressida (as well as in tales by Geoffrey Chaucer and others). It is also designated Uranus IX.[6]

Cressida
Discovery
Discovered byStephen P. Synnott / Voyager 2
Discovery dateJanuary 9, 1986
Orbital characteristics
Mean orbit radius
61,766.730 ± 0.046 km[1]
Eccentricity0.00036 ± 0.00011[1]
0.463569601 ± 0.000000013 d[1]
Inclination0.006 ± 0.040° (to Uranus' equator)[1]
Satellite ofUranus
Physical characteristics
Dimensions92 × 74 × 74 km[2]
Mean radius
41 ± 2 km[2]
~20,000 km²[3]
Volume~260,000 km³[3]
Mass~3.4×1017 kg[3]
Mean density
~1.3 g/cm³ (assumed)
~0.013 m/s2[3]
~0.034 km/s[3]
synchronous[2]
zero[2]
Albedo0.08 ± 0.01[4]
Temperature~64 K[3]

    Cressida belongs to Portia Group of moons, which also includes Bianca, Desdemona, Juliet, Portia, Rosalind, Cupid, Belinda and Perdita.[4] These moons have similar orbits and photometric properties.[4] Other than its orbit,[1] radius of 41 km[2] and geometric albedo of 0.08[4] almost nothing is known about it.

    At the Voyager 2 images Cressida appears as a stretched object, the major axis pointing towards Uranus. The ratio of axes of Cressida's prolate spheroid is 0.8 ± 0.3.[2] Its surface is grey in color.[2]

    References
    1. Jacobson, R.A. (1998). "The Orbits of the Inner Uranian Satellites From Hubble Space Telescope and Voyager2 Observations". The Astronomical Journal. 115 (3): 1195–1199. Bibcode:1998AJ....115.1195J. doi:10.1086/300263. S2CID 118616209.
    2. 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.
    3. Calculated on the basis of other parameters
    4. 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.
    5. Smith, B. A. (January 16, 1986). "IAU Circular No. 4164". Retrieved 2006-08-06.
    6. "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21, 2006. Retrieved 2006-08-06.

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