Recent Hubble Space Telescope images have corroborated an earlier prediction of the location of the two small moons, Ophelia and Cordelia, each with diameters of less than 40 miles (60 kilometers) across. The find marks the first time the moons have been directly observed from Earth. In 1986, Voyager 2 captured the first pictures of the wayward satellites and transmitted them to NASA's Jet Propulsion Laboratory.

Though researchers were able to determine rough orbits for the two moons, until this year they were unable to create an accurate model for complete orbits. Voyagers observations were extremely short-lived -- the spacecraft gathered less than two weeks of data -- and the gargantuan distance from Earth, along with tiny size of the moons, made the satellites impossible to spot.

"None of our instruments were strong enough to catch them," said Erich Karkoschka, an astronomer at the Lunar and Planetary Laboratory in Tucson, Arizona.

But that didnt stop Richard French and Philip Nicholson, astronomers from Wellesley College and Cornell University, respectively, from searching the moons out. French and Nicholson started their investigation by using celestial mechanics to predict gravitational effects between the natural satellites and one of Uranus rings.

"We can actually see the moons' effects on the ring in exactly the predicted way. To me it's a pretty compelling case."

Cordelia and Ophelia orbit Uranus on either side of the planets main ring. As a result, astronomers have dubbed them "shepherd" moons, since their apparent effect is to "herd" ring debris, preventing it from spreading out of its normal orbit.

"The satellites act to shepherd ring particles in place, kind of like sheep dogs would with sheep," explained French.

One predicted result of this shepherding action is the production of wavelike ripples along the inner and outer edges of the ring, due to the gravitational effects of the shepherding moons. These ripples are indications of the interaction between Ophelia, Cordelia and Uranus main ring. Yet since such ripples measure only about one-third of a mile (one-half of a kilometer) in amplitude -- too small to detect directly -- French and Nicholson had to rely on a technique called "stellar occultation" to prove their location.

"Stellar occultation is when something, in our case Uranus rings, passes in front of a star," said French. "When the ring we were interested in passed in front of a star, we could measure the shadow of the ring sweeping across the Earth. In the process, we measure the width of the ring and predicted a location for both Ophelia and Cordelia."

Though compelling, French and Nicholsons data was nevertheless still experimental. Without more direct evidence of the Uranian moons locations, nothing could be proved without a doubt.

Enter astronomer Erich Karkoschka. Last year his work with outer solar system Hubble images led to the discovery of Uranus 18^th moon. Knowing of his work, Nicholson and French compelled Karkoschka to start looking for Ophelia and Cordelia based on their prediction of the moons locations.

On first inspection, Karkoschkas images turned up empty. Yet when the researcher erased the background "noise" in the images, one of the moons popped out -- just where French and Nicholson had predicted. Soon enough, Karkoschka found the second moon as well, and the hunt was over.

"We now have both satellites agreeing with both techniques," said French. "We can actually see the moons effects on the ring in exactly the predicted way. To me its a pretty compelling case."

Scientists agree that the rediscovery of Ophelia and Cordelia will make an important impression in the world of astronomy. However, the find also highlights the value of teamwork in academic research.

"Whats fun about the whole story is that its one of these wonderful scientific collaborations," said French. "By working together and not in competition, weve come up with something thats really fun and important."