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UA scientist discovers moon orbiting Uranus

By Sean McLachlan
Arizona Daily Wildcat
June 9, 1999
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Arizona Daily Wildcat

photo courtesy UA office of Public Info UA senior research associate at the University of Arizona's Lunar and Planetary Laboratory, Erich Karkoschka, discovered a new moon around Uranus using Voyager 2 and Hubble Space Telescope photographs. The moon has been named S/1986 U10.

Arizona Summer Wildcat

A UA astronomer discovered a new moon around the planet Uranus, the International Astronomical Union announced late last month.

Erich Karkoschka, senior research associate at the University of Arizona's Lunar and Planetary Laboratory, found the moon while looking at images of the planet and its moons taken in 1986 when Voyager 2 passed nearby.

Karkoschka was comparing the Voyager images with photos taken by the Hubble Space Telescope.

Karkoschka looked at 300 photos of the planet's rings and moons.

In seven of them, he found that a faint point of light, previously believed to be a star, showed different brightness at different angles and was moving - characteristics attributed to a satellite.

Scientists who were studying the Voyager 2 images discovered 10 new moons, but missed this satellite for 13 years.

The new moon is very dim, its faint light nearly washed out by Uranus' glare.

Until the Hubble Space Telescope, no telescope was powerful enough to find it.

"You have to look carefully to find these images," Karkoschka said.

Karkoschka estimates the moon to be about 25 miles in diameter.

The moon, dubbed S/1986 U10, is the 18th discovered around the planet.

It orbits Uranus once every 15 hours and 18 minutes and is about 32,000 miles above the planet's hydrogen, helium and methane clouds.

Karkoschka said that the new moon is probably another of the tiny satellites.

"The composition is not known, but one expects they are mostly ice," he said.

The ice is mixed with interstellar dust and rock, making the moons surface as "dark as charcoal," he said.

Karkoschka has not thought of a name for the new moon, but will probably choose "something from Shakespeare."

Uranus' other moons are named after characters from Shakespeare's plays.

Puck is an oblong, cratered mass of rock and ice about 100 miles wide. Juliet is even smaller, and covered with dirty ice.

Considering how long S/1986 U10 remained unnoticed, more moons may be discovered in the future, Karkoschka said.