Cressida (moon)

There is also an asteroid called 548 Kressida.
Cressida
Voyager 2 image of the Uranian moons Portia, Cressida, and Ophelia
Discovery
Discovered by Stephen P. Synnott / Voyager 2
Discovery date January 9, 1986
Orbital characteristics
Mean orbit radius
 61,766.730 ± 0.046 km[1]
Eccentricity 0.00036 ± 0.00011[1]
0.463569601 ± 0.000000013 d[1]
Inclination 0.006 ± 0.040° (to Uranus' equator)[1]
Satellite of Uranus
Physical characteristics
Dimensions 92 × 74 × 74 km[2]
Mean radius
 39.8 ± 2 km[2][3][4]
~20,000 km²[lower-alpha 1]
Volume ~260,000 km³[lower-alpha 1]
Mass 2.5±0.4×1017 kg[5]
Mean density
 0.86±0.16 g/cm³[5]
~0.013 m/s2[lower-alpha 1]
~0.034 km/s[lower-alpha 1]
synchronous[2]
zero[2]
Albedo
Temperature ~64 K[lower-alpha 1]

    Cressida (/ˈkrɛsɪdə/ KRES-i-də, Greek: Χρησίδα) 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.[7] 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.[8]

    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,[1] radius of 41 km[2] and geometric albedo of 0.08,[6] virtually nothing is known about it.

    In the Voyager 2 images Cressida appears as an elongated object, its 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]

    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 was found to be 2.5±0.4×1017 kg. Cressida is the only small satellite of Uranus for which the mass has been directly measured.[5]

    Cressida may collide with Desdemona within the next 100 million years.[9]

    See also

    References

    Explanatory notes

    1. 1 2 3 4 5 Calculated on the basis of other parameters.

    Citations

    1. 1 2 3 4 5 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.
    2. 1 2 3 4 5 6 7 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. 1 2 "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 24 October 2008. Retrieved 12 December 2008.
    4. 1 2 Williams, Dr. David R. (23 November 2007). "Uranian Satellite Fact Sheet". NASA (National Space Science Data Center). Retrieved 12 December 2008.
    5. 1 2 3 Chancia, Robert. A.; Hedman, Matthew M.; French, Richard G. (28 August 2017). "Weighing Uranus' moon Cressida with the η ring" (PDF). Retrieved 28 August 2017.
    6. 1 2 3 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.
    7. ↑ Smith, B. A. (January 16, 1986). "Satellites of Uranus". IAU Circular. 4164. Retrieved 29 October 2011.
    8. ↑ "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21, 2006. Retrieved 6 August 2006.
    9. ↑ 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.
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