Cressida (moon)

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Discovered byStephen P. Synnott / Voyager 2
Discovery dateJanuary 9, 1986
Avgdistance from the center of its orbital path61,766.730 ± 0.046 km[1]
How long it takes to complete an orbit0.463569601 ± 0.000000013 d[1]
Angle above the reference plane
0.006 ± 0.040° (to Uranus' equator)[1]
What it orbitsUranus
Size and other qualities
Measurements92 × 74 × 74 km[2]
Average radius41 ± 2 km[2]
Surface area~20,000 km²[3]
Volume~260,000 km³[3]
Mass~3.4×1017 kg[3]
Average density~1.3 g/cm³ (assumed)
Surface gravity~0.013 m/s2[3]
Escape velocity~0.034 km/s[3]
Rotation periodsynchronous[2]
Angle at which it turns
(in relation to its orbit)
How much light it reflects0.08 ± 0.01[4]
Avg. surface temp.~64 K[3]

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 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 axises of the Cressida's prolate spheroid is 0.8 ± 0.3.[2] Its surface is grey in color.[2]

References[change | change source]

  1. 1.0 1.1 1.2 1.3 Jacobson, R.A. (1998). "The Orbits of the Inner Uranian Satellites From Hubble Space Telescope and Voyager2 Observations". The Astronomical Journal 115: 1195-1199. doi:10.1086/300263. 
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Karkoschka, Erich (2001). "Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites". Icarus 151: 69–77. doi:10.1006/icar.2001.6597. 
  3. 3.0 3.1 3.2 3.3 3.4 3.5 Calculated on the basis of other parameters
  4. 4.0 4.1 4.2 4.3 Karkoschka, Erich (2001). "Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope". Icarus 151: 51–68. 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.

Other websites[change | change source]