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Cordelia (moon)

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Cordelia
Cordelia (bottom), Ophelia (top), and Uranus's narrow rings photographed from afar by Voyager 2 on 21 January 1986
Discovery[1]
Discovered byRichard J. Terrile / Voyager 2
Discovery dateJanuary 20, 1986
Designations
Designation
Uranus VI
Pronunciation/kɔːrˈdiːliə/[2]
AdjectivesCordelian[3]
Orbital characteristics[4]
49751.722±0.149 km
Eccentricity0.00026±0.000096
0.33503384±0.00000058 d
Inclination0.08479°±0.031° (to Uranus's equator)
Satellite ofUranus
Physical characteristics
Dimensions50 × 36 × 36 km[a]
19.8±3.0 km[b]
Volume33900 km3 ± 34.9%[6]
Mass(6.08±0.57)×1016 kg[6]
Mean density
1.79+0.97
−0.49 g/cm3[6]
synchronous (assumed)
zero (assumed)
Albedo~0.056 (geometric)[c]
23.52–23.71 (± 0.35)
(at opposition)[7]
10.81–11.00 (± 0.35)[7]

Cordelia is the innermost known moon of Uranus. It was discovered from the images taken by Voyager 2 on January 20, 1986, and was given the temporary designation S/1986 U 7.[1] It was not detected again until the Hubble Space Telescope observed it in 1997.[8][9] Cordelia takes its name from the youngest daughter of Lear in William Shakespeare's King Lear. It is also designated Uranus VI.[10]

Other than its orbit,[4] size of 50 km × 36 km (31 mi × 22 mi),[5] and geometric albedo of 0.056,[11] little is known about it. In the Voyager 2 images, Cordelia appears as an elongated object with its major axis pointing towards Uranus. The ratio of axes of Cordelia's prolate spheroid is 0.7±0.2.[5] Observations taken in 2001–2007 found that Cordelia had decreased in brightness by about a factor of five since the 1986 Voyager 2 flyby. The change in viewing geometry since then suggests that Cordelia may have a very flattened shape and be much smaller in size than inferred from previous measurements.[12]

Cordelia acts as the inner shepherd satellite for Uranus's ε ring.[13] Its orbit is within Uranus's synchronous orbit radius, and is therefore slowly decaying due to tidal deceleration.[14] Cordelia is very close to a 5:3 orbital resonance with Rosalind.[15]

See also

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Notes

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  1. ↑ The satellite's shape was modelled as a prolate spheroid (a × b × b); thus, only constraints for two axes were determined (a × b = 25 × 18 km).[5]
  2. ↑ This is the geometric mean of the three axes (), calculated from = 21±3 km and = 0.7±0.2.[5] However, various sources use 21±3 km or 25 × 18 km as the radius value or cross section size instead.
  3. ↑ Visually estimated from Fig. 12 in Karkoschka, Hubble 2001.

References

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  1. 1 2 Smith, B. A. (1986-01-27). "Satellites and Rings of Uranus". IAU Circular (4168). Retrieved 2011-10-31.
  2. ↑ Benjamin Smith (1903). The Century Dictionary and Cyclopedia.
  3. ↑ Jennifer Bates (2010). Hegel and Shakespeare on Moral Imagination. p. 102.
  4. 1 2 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.
  5. 1 2 3 4 Karkoschka, Voyager 2001, Table V.
  6. 1 2 3 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. Bibcode:2024Icar..41115957F. doi:10.1016/j.icarus.2024.115957. ISSN 0019-1035. S2CID 266900064.
  7. 1 2 Karkoschka, Hubble 2001, Table IV.
  8. ↑ Karkoschka, Hubble 2001.
  9. ↑ Showalter, M. R.; Lissauer, J. J. (2003-09-03). "Satellites of Uranus". IAU Circular (8194). Retrieved 2011-10-31.
  10. ↑ "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. USGS Astrogeology. July 21, 2006. Retrieved 6 August 2006.
  11. ↑ Karkoschka, Hubble 2001, Fig. 12.
  12. ↑ Showalter, Mark; Lissauer, J; French, R. G.; Hamilton, D. P.; Nicholson, P. D.; de Pater, I.; Hammel, H. B. (21–25 September 2008). New Phenomena in the Uranian Ring-Moon System. European Planetary Science Congress 2008. Vol. 3. Münster, Germany (published January 2008). p. 765. Bibcode:2008epsc.conf..765S.
  13. ↑ Esposito, L. W. (2002). "Planetary rings". Reports on Progress in Physics. 65 (12): 1741–1783. Bibcode:2002RPPh...65.1741E. doi:10.1088/0034-4885/65/12/201. S2CID 250909885.
  14. ↑ Karkoschka, Voyager 2001.
  15. ↑ Murray, Carl D.; Thompson, Robert P. (1990-12-06). "Orbits of shepherd satellites deduced from the structure of the rings of Uranus". Nature. 348 (6301): 499–502. Bibcode:1990Natur.348..499M. doi:10.1038/348499a0. ISSN 0028-0836. S2CID 4320268.

Bibliography

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