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Caliban (moon)

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Caliban
Discovery image of Caliban taken by the Hale Telescope in September 1997
Discovery[1]
Discovered by
Discovery siteHale Telescope at Palomar Obs.
Discovery date6 September 1997
Designations
Designation
Uranus XVI
Pronunciation/ˈkæləbæn/[2][3]
Named after
Caliban
S/1997 U 2
AdjectivesCalibanian /kæləˈbeɪniən/[4]
Orbital characteristics[5]
Epoch 27 June 2015 (JD 2457200.5)
Observation arc17.96 yr (6,559 d)
7,163,810 km (0.0478871 AU)
Eccentricity0.0771431
1.59 yr (579.26 d)
294.66253°
0° 37m 17.345s / day
Inclination139.90814° (to the ecliptic)
140.878° (to local Laplace plane)[6]
175.21248°
342.53671°
Satellite ofUranus
GroupCaliban group
Physical characteristics
42 20
−12 km[7]
Mass~2.5×1017 kg (estimate)[8]
Mean density
~1.3 g/cm3 (assumed)[8]
9.948±0.019 hr (double-peaked)[7]
2.66±0.04 hr (single-peaked)[9]
Albedo0.22 0.20
−0.12[7]
Temperature~65 K (mean estimate)
22.0 (V)[7]
9.160±0.016[7]
9.0[5]

Caliban /ˈkælɪbæn/ is the second-largest retrograde irregular satellite of Uranus.[10] It was discovered on 6 September 1997 by Brett J. Gladman, Philip D. Nicholson, Joseph A. Burns, and John J. Kavelaars using the 200-inch Hale Telescope together with Sycorax and given the temporary designation S/1997 U 1.[1]

Designated Uranus XVI, it was named after the monster character in William Shakespeare's play The Tempest.

Orbit

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Animation of Caliban's orbit around Uranus.
   Uranus  ·    Sycorax ·    Francisco  ·    Caliban  ·    Stephano  ·    Trinculo

Caliban follows a distant orbit, more than 10 times further from Uranus than Oberon, the outermost regular moon.[1] Its orbit is retrograde, moderately inclined and slightly eccentric. The orbital parameters suggest that it may belong to the same dynamic cluster as Stephano and Francisco, suggesting common origin.[11]

Retrograde irregular satellites of Uranus

The diagram illustrates the orbital parameters of the retrograde irregular satellites of Uranus (in polar co-ordinates) with the eccentricity of the orbits represented by the segments extending from the pericentre to the apocentre.

Physical characteristics

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Caliban's diameter is estimated to be around 42 km, based on thermal measurements by the Herschel Space Observatory.[7] Its albedo is estimated at around 0.22, which is unusually high compared to those of other Uranian irregular satellites. Neptune's largest irregular satellite, Nereid, has a similarly high albedo as Caliban.[7]

Somewhat inconsistent reports put Caliban in light-red category (B–V = 0.83 V–R = 0.52,[12] B–V = 0.84 ± 0.03 V–R = 0.57 ± 0.03[11]), redder than Himalia but still less red than most Kuiper belt objects. Caliban may be slightly redder than Sycorax.[9] It also absorbs light at 0.7 μm, and one group of astronomers think this may be a result of liquid water that modified the surface.[13]

Measurements of Caliban's light curve by the Kepler space telescope indicate that its rotation period is about 9.9 hours.[7]

Origin

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Caliban is hypothesized to be a captured object: it did not form in the accretionary disk that existed around Uranus just after its formation. The exact capture mechanism is not known, but capturing a moon requires the dissipation of energy. The possible capture processes include: gas drag in the protoplanetary disk, many body interactions and the capture during the fast growth of the Uranus' mass (so-called "pull-down").[10][11]

See also

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References

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  1. ^ a b c Gladman Nicholson et al. 1998.
  2. ^ "Caliban". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ^ Benjamin Smith (1903) The Century Dictionary and Cyclopedia
  4. ^ Apple, Au, & Gandin (2009) The Routledge international handbook of critical education
  5. ^ a b "M.P.C. 95215" (PDF). Minor Planet Circular. Minor Planet Center. 29 August 2015.
  6. ^ Brozovic, M.; Jacobson, R. A. (2009). "Planetary Satellite Mean Orbital Parameters". The Orbits of the Outer Uranian Satellites, Astronomical Journal, 137, 3834. JPL/NASA. Retrieved 2011-11-06.
  7. ^ a b c d e f g h Farkas-Takács, A.; Kiss, Cs.; Pál, A.; Molnár, L.; Szabó, Gy. M.; Hanyecz, O.; et al. (September 2017). "Properties of the Irregular Satellite System around Uranus Inferred from K2, Herschel, and Spitzer Observations". The Astronomical Journal. 154 (3): 13. arXiv:1706.06837. Bibcode:2017AJ....154..119F. doi:10.3847/1538-3881/aa8365. S2CID 118869078. 119.
  8. ^ a b "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 20 December 2008. Retrieved 10 March 2009.
  9. ^ a b Maris, Michele; Carraro, Giovanni; Cremonese, Gabrielle; Fulle, Marco (May 2001). "Multicolor Photometry of the Uranus Irregular Satellites Sycorax and Caliban". The Astronomical Journal. 121 (5): 2800–2803. arXiv:astro-ph/0101493. Bibcode:2001AJ....121.2800M. doi:10.1086/320378. S2CID 16273706.
  10. ^ a b Sheppard, Jewitt & Kleyna 2005.
  11. ^ a b c Grav, Holman & Fraser 2004.
  12. ^ Rettig, Walsh & Consolmagno 2001.
  13. ^ Schmude, Richard (2008). Uranus, Neptune, Pluto and How to Observe Them. Springer. ISBN 978-0-387-76601-0.
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