Uranus may have up to 25 more moons than have been previously seen, British astronomers predict.

When the American Voyager 2 spacecraft flew by Uranus in 1986, it produced images that added 10 icy moons to the planet's five already-known moons. Two of the moons, Cordelia and Ophelia, are thought to help keep Uranus's 11 major rings from spreading into space.However, London University's Carl Murray and Robert Thompson said Wednesday those two "shepherding" moons are still not enough to maintain the rings' thin, sharp edges.

Analyzing data collected by Voyager 2 and the orbits of known rings and moons, the astronomers predicted the location of 25 more small moons.

The moons are probably less than 6 miles in radius but larger than 0.6 mile in radius, the researchers said.

Further indirect evidence, consisting of "gaps" in some of the Voyager 2 images and a wave-like feature in one ring caused by gravitational interactions, shows two of the new moons may be about 5.4 miles in radius and may orbit about 28,200 miles and 28,800 miles respectively from the center of the planet.

Uranus is the seventh planet from the sun, and is about four times the size of Earth.