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Caliban (moon)

Caliban feat.png
Discovery image of Caliban
Discovered by using the Hale telescope
Discovery dateSeptember 6, 1997
Orbital characteristics
Mean orbit radius
7,231,000 km[2][3]
579.73 d
0.91 km/s[a]
Satellite ofUranus
Physical characteristics
Mean radius
36 km (estimate)[4][5]
~16,000 km² (estimate)
Volume~200,000 km³ (estimate)
Mass~2.5×1017 kg (estimate)
Mean density
~1.3 g/cm³ (assumed)
~0.02 m/s² (estimate)
~0.031 km/s (estimate)
Albedo0.04 (assumed)[4]
Temperature~65 K (estimate)

Caliban (/ˈkælɪbæn/ KAL-i-ban or /ˈkælɪbən/ KAL-i-bən) is the second-largest retrograde irregular satellite of Uranus.[7] 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.


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

Caliban follows a distant orbit, more than 10 times further from Uranus than the furthest regular moon Oberon.[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.[8]

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

Its diameter is estimated at 72 km (assuming albedo of 0.04)[7][5] making it the second largest irregular satellite of Uranus, half the size of Sycorax, the biggest irregular satellite of Uranus.

Somewhat inconsistent reports put Caliban in light-red category (B–V = 0.83 V–R = 0.52,[9] B–V = 0.84 ± 0.03 V–R = 0.57 ± 0.03[8]), redder than Himalia but still less red than most Kuiper belt objects. Caliban may be slightly redder than Sycorax.[6] 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.[10]

The light curve suggests the rotation period of Caliban is about 2.7h.[6]


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").[7][8]

See also


  1. ^ Calculated on the basis of other parameters.


  1. ^ a b c Gladman Nicholson et al. 1998.
  2. ^ a b Sheppard, Jewitt & Kleyna 2005, p. 523, Table 3.
  3. ^ a b 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.
  4. ^ a b Sheppard, Jewitt & Kleyna 2005, p. 523, Table 3 ... ri (km) ... 36 ... i Radius of satellite assuming a geometric albedo of 0.04.
  5. ^ a b "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 20 December 2008. Retrieved 10 March 2009.
  6. ^ a b c 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. Retrieved 14 September 2008.
  7. ^ a b c Sheppard, Jewitt & Kleyna 2005.
  8. ^ a b c Grav, Holman & Fraser 2004.
  9. ^ Rettig, Walsh & Consolmagno 2001.
  10. ^ Schmude, Richard (2008). Uranus, Neptune, Pluto and How to Observe Them. Springer. ISBN 978-0-387-76601-0.

External links