| Prospero | |
| Mpc Name: | Uranus XVIII |
| Pronounced: | [1] |
| Adjectives: | Prosperonian,[2] Prosperian [3] |
| Discoverer: | |
| Discovered: | 18 July 1999 |
| Mean Orbit Radius: | 16,256,000 km |
| Eccentricity: | 0.4448 |
| Period: | 1978.29 d |
| Inclination: | 152° (to the ecliptic) |
| Satellite Of: | Uranus |
| Mean Radius: | 25 km (estimate) <50 km |
| Surface Area: | ~8000 km2 (estimate) |
| Volume: | ~65,000 km3 (estimate) |
| Mass: | ~8.5 kg (estimate) |
| Surface Grav: | ~0.0063 m/s2 (estimate) |
| Escape Velocity: | ~0.021 km/s (estimate) |
| Density: | ~1.3 g/cm3 (assumed) |
| Axial Tilt: | ? |
| Albedo: | 0.04 (assumed) |
| Single Temperature: | ~65 K (estimate) |
Prospero is a relatively small retrograde irregular satellite of Uranus 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.
The orbital parameters suggest that it may belong to the same dynamic cluster as Sycorax and Setebos, suggesting common origin. However, this suggestion does not appear to be supported by the observed colours. The satellite appears neutral (grey) in visible light (colour indices B−V=0.80, R−V=0.39), similar to Setebos but different from Sycorax (which is light red).