NASA Press Release
July 1990
A new moon orbiting planet Saturn has been discovered by Dr. Mark Showalter, a researcher at NASA's Ames Research Center, Mountain View, Calif. Showalter found the small, bright object while analyzing images taken by the Voyager 2 spacecraft. "It was very gratifying to see it," he said. Showalter used a computer program he wrote to sort through 30,000 images sent back to Earth during the Voyager/Saturn encounters in 1980-81.
When the discovery is certified by the International
Astronomical Union (IAU), it will bring to 18 the number of
Saturnian moons. The new moon has a diameter of only 12 miles
and is temporarily designated 1981S13. It orbits in the major
gap, known as Encke's gap, in Saturn's outermost major ring, the
"A" ring.
Showalter further analyzed the disturbance and used this
"moonlet wake" pattern, resembling a motorboat wake, to determine
the position and mass of the unseen body. The amplitude of the
waves, he said, suggested the mass of the unobserved object and
the wavelength of the ripples revealed the moon's possible
position.
Showalter's computer program combined information on the
Voyager spacecraft's position and camera direction with his
prediction of the orbit to search through the enormous stock of
Voyager imagery and select the frames where the moon would fall
in the camera's field of view.
Brian Marsden of the IAU contacted Showalter saying, "I
congratulate you on this modern-day repetition of the discovery
of Neptune. It's a nice piece of work." Planet Neptune also was
first predicted by theorists who observed its gravitational
influence on Uranus before sighting it in 1846.
Showalter's research is supported by the Ames Space Science
Division under a joint agreement with Stanford University. He is
a research affiliate at the Stanford Center for Radar Astronomy.
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Ron Baalke
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