Caliban (pronounced /ˈkælɨbæn/ KAL-i-ban, or /ˈkælɨbən/ KAL-ə-bən) is the second largest retrograde irregular moon of Uranus.[4] 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.


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, together with Stephano and Francisco to the same dynamic cluster, suggesting common origin.[7]

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)[4][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,[8] B–V = 0.84 ± 0.03 V–R = 0.57 ± 0.03[7]), 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 um, and one group of astronomers think this may be a result of liquid water that modified the surface.[9]

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, which 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).[4][7]

See also

* Moons of Uranus
* Irregular moons


1. ^ a b c Gladman, Brett J.; Nicholson, Philip D.; Burns, Joseph A. et al. (1998). "Discovery of two distant irregular moons of Uranus". Nature 392: 897–899. doi:10.1038/31890.
2. ^ Sheppard 2005, p. 523
3. ^ a b Jacobson, R.A. (2003) URA067 (28 June 2007). "Planetary Satellite Mean Orbital Parameters". JPL/NASA. Retrieved 23 January 2008.
4. ^ a b c d e f Sheppard, Scott S.; David C. Jewitt, Jan Kleyna (2005). "An Ultradeep Survey for Irregular Satellites of Uranus: Limits to Completeness" (pdf). The Astronomical Journal 129 (1): 518–525. doi:10.1086/426329. arXiv:astro-ph/0410059. Retrieved 20 October 2009. "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; Giovanni Carraro, Gabrielle Cremonese, Marco Fulle (May 2001). "Multicolor Photometry of the Uranus Irregular Satellites Sycorax and Caliban". The Astronomical Journal 121 (5): 2800–2803. doi:10.1086/320378. Retrieved 14 September 2008.
7. ^ a b c Grav, Tommy; Holman, Matthew J. (2004). "Photometry of irregular satellites of Uranus amd Neptune". The Astrophysical Journal 613: L77–L80. doi:10.1086/424997. arXiv:astro-ph/0301016.
8. ^ Rettig, Terrence W.; Walsh, Kevin; Consolmagno, Guy (2001). "Implied Evolutionary Differences of the Jovian Irregular Satellites from a BVR Color Survey". Icarus 154: 313–320. doi:10.1006/icar.2001.6715.
9. ^ Schmude, Richard (2008). Uranus, Neptune, Pluto and How to Observe Them. Springer. ISBN 0387766014, 9780387766010.

External links

* Caliban Profile by NASA's Solar System Exploration
* David Jewiit pages
* Uranus' Known Satellites (by Scott S. Sheppard)
* Ephemeris IAU-NSES
* Caliban and Sycorax, Moons of Uranus (2005 Calvin J. Hamilton)

Moons of Uranus

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