Caliban (moon)

Caliban

Discovery image of Caliban
Discovery[1]
Discovered by

using the Hale telescope

Discovery date September 6, 1997
Designations
Adjectives Calibanian
Orbital characteristics
Mean orbit radius
 7,231,000 km[2][3]
Eccentricity 0.1812[3]
579.73 d
0.91 km/s[lower-alpha 1]
Inclination
Satellite of Uranus
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)
2.7h[6]
?
Albedo 0.04 (assumed)[4]
Temperature ~65 K (estimate)

    Caliban (/ˈkælᵻbæn/ KAL-i-ban or /ˈkælᵻbən/ KAL-ə-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.

    Retrograde irregular satellites of Uranus

    Orbit

    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]

    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]

    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 the Uranus' mass (so-called "pull-down").[7][8]

    See also

    Footnotes

    1. ↑ Calculated on the basis of other parameters.

    References

    1. 1 2 3 Gladman Nicholson et al. 1998.
    2. 1 2 Sheppard, Jewitt & Kleyna 2005, p. 523, Table 3.
    3. 1 2 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. 1 2 Sheppard, Jewitt & Kleyna 2005, p. 523, Table 3 ... ri (km) ... 36 ... i Radius of satellite assuming a geometric albedo of 0.04.
    5. 1 2 "Planetary Satellite Physical Parameters". JPL (Solar System Dynamics). 20 December 2008. Retrieved 10 March 2009.
    6. 1 2 3 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/0101493Freely accessible. Bibcode:2001AJ....121.2800M. doi:10.1086/320378. Retrieved 14 September 2008.
    7. 1 2 3 Sheppard, Jewitt & Kleyna 2005.
    8. 1 2 3 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

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