Caliban (moon)
Template:Short description Template:Infobox planet
Caliban Template:IPAc-en is the second-largest irregular satellite of Uranus.Template:Sfn 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.Template:Sfn
Designated Uranus XVI, it was named after the monster character in William Shakespeare's play The Tempest.
Orbit
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Caliban follows a distant orbit, more than 10 times further from Uranus than Oberon, the outermost regular moon.Template:Sfn 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 a common origin.Template:Sfn
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
Caliban's diameter is estimated to be around Template:Cvt, based on thermal measurements by the Herschel Space Observatory.<ref name="FarkasTakacs2017"/> 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.<ref name="FarkasTakacs2017"/>
Somewhat inconsistent reports put Caliban in the light-red category (Template:Nowrap Template:Nowrap,Template:Sfn Template:Nowrap Template:NowrapTemplate:Sfn), redder than Himalia but still less red than most Kuiper belt objects. Caliban may be slightly redder than Sycorax.<ref name="Maris 2001" /> 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.<ref name="Schmude 2008" />
Measurements of Caliban's light curve by the Kepler space telescope indicate that its rotation period is about 9.9 hours.<ref name="FarkasTakacs2017"/>
Origin
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 Uranus's mass (so-called "pull-down").Template:SfnTemplate:Sfn
See also
References
External links
- Caliban Profile by NASA's Solar System Exploration
- David Jewiit pages
- Uranus' Known Satellites (by Scott S. Sheppard)
- MPC: Natural Satellites Ephemeris Service
- Caliban and Sycorax, Moons of Uranus (2005 Calvin J. Hamilton)
Template:Moons of Uranus Template:Uranus Template:Solar System moons (compact)