Caliban's diameter is 60 km and the diameter of Sycorax is 120 km. Some scientists think that there may still be more moons around Uranus waiting to be discovered. The Rings of Uranus Uranus has 11 rings. Most of Uranus's rings are named after letters from the Greek alphabet. Unlike Saturn, Uranus has dark rings that contain boulders of ice.
Astronomers think the rings are dark, because there is no dust for the sunlight to reflect off of.
Uranus has no dust in it's rings because gravity pulled all the dust into the planet, but the ice boulders are too heavy to be pulled in by the force of gravity so they just make the shape of the rings. Some astronomers think in millions of years Uranus's rings will disappear completely as gravity slowly pulls the ice boulders into the planet. The dictionary says gavity is the natural force of attraction exerted by a planet, such as Earth, upon objects at or near its surface, tending to draw them toward the center of the body. The force of gravity is what makes us stay on the ground and more gravity makes us heavy while less gravity makes us lighter. On Uranus, the force of gravity is 10 percent less than the force of gravity on Earth .