Images taken by the Voyager 2 probe and the Hubble Space Telescope confirmed the existence of the moons and two extra rings around the planet, said experts Mark Showalter, of the SETI institute in Mountain View, California and Jack Lissauer of NASA's Ames Research Center.

The newly discovered moons orbit outside of Uranus's previously known ring system but closer than the five large moons already known.

Scientists now believe the seventh planet from the sun has an outer belt of at least 11 moons, the five classical moons nearer Uranus. There are also 13 dusty rings.

The experts have named the new moons Mab and Cupid.

Showalter and Lissauer said that the moons do not follow simple orbits but "show complex dynamics indicating the system is unstable or chaotic."

They said the the outermost ring is replenished by the 20 kilometermile)-wide Mab. Meteoroid impacts continually blast dust off the surface of Mab. The dust then spreads out into a ring around Uranus.

Mab's ring receives a fresh infusion of dust from each impact. Nature keeps the ring supplied with new dust while older dust spirals away or bangs back into the moon.

Voyager 2 took the first images of the moons in January 1986. However, they were first spotted by more recent pictures taken by the Hubble.

Uranus was first spotted on March 13, 1781, the first planet to be discovered in modern times. The planet is mainly made up of rock and ice.

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