Cressida (moon)

There is also an asteroid called 548 Kressida.
Cressida
Enhanced Voyager 2 image of Cressida
Discovery
Discovered byStephen P. Synnott / Voyager 2
Discovery dateJanuary 9, 1986
Designations
Designation
Uranus IX
Pronunciation/ˈkrɛsədə/[1]
Named after
Χρησίδα
AdjectivesCressidian /krɛˈsɪdiən/[2]
Orbital characteristics[3]
61,766.730 ± 0.046 km
Eccentricity0.00036 ± 0.00011
0.463569601 ± 0.000000013 d
Inclination0.006 ± 0.040° (to Uranus' equator)
Satellite ofUranus
Physical characteristics
Dimensions92 × 74 × 74 km[4][note 1]
~20000 km2[a]
Volume263800±38.0% km3[5]
Mass(1.839±0.212)×1017 kg[5]
Mean density
0.70+0.44
−0.21 g/cm3[5]
~0.006–0.009 m/s2[a]
~0.023–0.026 km/s[a]
synchronous[4]
zero[4]
Albedo0.08±0.005[6]
0.07[7]
Temperature~65 K[a]
  1. ^ Only two dimensions are known; the third dimension has been assumed to equal the smaller known dimension.

Cressida /ˈkrɛsədə/ is an inner satellite of Uranus. It was discovered from the images taken by Voyager 2 on 9 January 1986, and was given the temporary designation S/1986 U 3.[8] It was named after Cressida, 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.[9]

Cressida belongs to the Portia group of satellites, which includes Bianca, Desdemona, Juliet, Portia, Rosalind, Cupid, Belinda, and Perdita.[6] These satellites have similar orbits and photometric properties.[6] Other than its orbit,[3] size of 92 × 74 km,[4] and geometric albedo of 0.08,[6] virtually nothing is known about it.

In Voyager 2 imagery Cressida appears as an elongated object, with its major axis pointing towards Uranus. The ratio of axes of Cressida's prolate spheroid is 0.8 ± 0.3.[4] Its surface is grey in color.[4]

Cressida orbits close to a 3:2 resonance with the η ring, one of the rings of Uranus. Perturbations of the ring's shape provide a way to measure the mass of Cressida, which in 2024 was found to be (1.839±0.212)×1017 kg.[5] Cressida is one of the few small satellites of Uranus for which the mass has been directly measured.[10][5]

Cressida may collide with Desdemona within the next 100 million years.[11]

See also

Notes

  1. ^ a b c d Calculated on the basis of other parameters.

References

  1. ^ Benjamin Smith (1903). The Century Dictionary and Cyclopedia.
  2. ^ Kellog (1995). Boccaccio's and Chaucer's Cressida.
  3. ^ a b Jacobson, R. A. (1998). "The Orbits of the Inner Uranian Satellites From Hubble Space Telescope and Voyager 2 Observations". The Astronomical Journal. 115 (3): 1195–1199. Bibcode:1998AJ....115.1195J. doi:10.1086/300263. S2CID 118616209.
  4. ^ a b c d e f 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.
  5. ^ a b c d e French, Richard G.; Hedman, Matthew M.; Nicholson, Philip D.; Longaretti, Pierre-Yves; McGhee-French, Colleen A. (2024-03-15). "The Uranus system from occultation observations (1977–2006): Rings, pole direction, gravity field, and masses of Cressida, Cordelia, and Ophelia". Icarus. 411: 115957. arXiv:2401.04634. doi:10.1016/j.icarus.2024.115957. ISSN 0019-1035.
  6. ^ a b c d 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.
  7. ^ Williams, Dr. David R. (23 November 2007). "Uranian Satellite Fact Sheet". NASA (National Space Science Data Center). Retrieved 12 December 2008.
  8. ^ Smith, B. A. (January 16, 1986). "Satellites of Uranus". IAU Circular. 4164. Retrieved 29 October 2011.
  9. ^ "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21, 2006. Retrieved 6 August 2006.
  10. ^ Chancia, Robert. A.; Hedman, Matthew M.; French, Richard G. (28 August 2017). "Weighing Uranus' moon Cressida with the η ring". The Astronomical Journal. 154 (4): 153. arXiv:1708.07566. Bibcode:2017AJ....154..153C. doi:10.3847/1538-3881/aa880e. S2CID 54827255.
  11. ^ Duncan, Martin J.; Lissauer, Jack J. (1997). "Orbital Stability of the Uranian Satellite System". Icarus. 125 (1): 1–12. Bibcode:1997Icar..125....1D. doi:10.1006/icar.1996.5568.