Astronomers locate lost pair of Uranus moons
TUCSON, Arizona -- Fourteen years after disappearing from
astronomical observations, two moons of Uranus have been
Voyager II first observed Ophelia and Cordelia more than a
decade ago, but they quickly faded from view after the
spacecraft left the Uranus system -- until this month, when
scientists sifting through Hubble images spotted the tiny
The new sighting strengthens Uranus' claim as the moon king
of the solar system. The seventh planet from the sun has 20
known natural satellites, more than any other planet.
Moons' diameters only 25 miles
Scientists looking at Voyager 2 images discovered the moons
in 1986. Voyager 2 observed the satellites for two weeks and
then left Uranus for the Neptune system.
But scientists soon lost sight of the moon pair, having
insufficient data to predict their orbits and inadequate
instruments to observe them.
They remained lost until this year. Astronomers from three
academic institutions announced last week that they found the
For years, telescopes on Earth were unable to spot the tiny,
distant satellites. Each moon has a diameter of about 25
miles (40 km) and is more than 1.7 billion miles (2.7 billion
Hubble, ripples aid in search
But Hubble images have become significantly more detailed in
recent years. And a few weeks ago Erich Karkoschka, a
researcher at the University of Arizona, spotted Ophelia
while conducting a computer-enhanced search of 1997 Hubble
Meanwhile, astronomers at Wellesley College and Cornell
University had found promising signs of the two moons by
checking ripple patterns, likely caused by the moons'
gravity, on the edge of Uranus' brightest ring.
"Ever since these narrow rings were found around Uranus, (we)
realized that something must be holding them together,"
Philip Nicholson, a Cornell astronomy professor who
participated in the search, said in a statement.
Karkoschka checked for Cordelia based on the work of the
Wellesley and Cornell astronomers. He found it right where
they predicted it would be.
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