Prospero, also known as Uranus XVIII, is one of the largest retrograde irregular satellites of Uranus.

Animation of discovery images to show Prospero's motion among background stars

Discovery and Naming

Prospero was discovered on 18 July 1999 by the astrophysicist Matthew Holman and his team, and given the provisional designation S/1999 U 3.

Confirmed as Uranus XVIII, it was named after the sorcerer Prospero in William Shakespeare's play The Tempest.

Orbit

Prospero orbits Uranus at an average distance of 16,256,000 km, in 1978 days, at an inclination of about 152° to the ecliptic, in a retrograde direction and with a high eccentricity of 0.445. The orbital elements are continuously changing due to solar and planetary perturbations.

Physical characteristics

Prospero's estimated diameter is 50 kilometers, assuming an albedo of 4%.

The satellite appears neutral (grey) in visible light (colour indices B−V=0.80, R−V=0.39), similar to Setebos.

Measurements of Prospero's light curve by the Kepler Space Telescope indicate that its rotation period is about 7 hours and 8.76 min, which makes it one of the fastest-rotating moons in the Solar System.

Origin

Prospero probably did not form near Uranus but was captured by Uranus later. Its orbital parameters suggest that it may belong to the same dynamic cluster as Sycorax and Setebos, suggesting a common origin. However, Sycorax has a much redder color than the other moons, which tend to be grey in color.

See also

  • Grav, Tommy; Holman, Matthew J.; Fraser, Wesley C. (20 September 2004). "Photometry of Irregular Satellites of Uranus and Neptune". The Astrophysical Journal. 613 (1): L77–L80. arXiv:. Bibcode:. doi:. S2CID .
  • Sheppard, S. S.; Jewitt, D.; Kleyna, J. (2005). "An Ultradeep Survey for Irregular Satellites of Uranus: Limits to Completeness". The Astronomical Journal. 129 (1): 518–525. arXiv:. Bibcode:. doi:. S2CID .

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