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NSF PR 99-61 - October 6, 1999
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Astronomers Sight an Asteroid's Moon
Astronomers this week announced their discovery of
a moon orbiting an asteroid, in the first images ever
obtained of such an object from Earth. Only one satellite
orbiting an asteroid had been seen before from space.
In work supported by the National Science Foundation
(NSF) and NASA, an international team headed by William
Merline of the Southwest Research Institute sighted
a moon orbiting the asteroid (45) Eugenia, in the
main asteroid belt between Mars and Jupiter. The images
will be published in the October 7 issue of Nature.
"Making this discovery with the newly developed adaptive
optics moves ground-based astronomy to the forefront
in exploring neighboring objects in our solar system,"
said Vernon Pankonin, manager of NSF's planetary astronomy
Merline's team plans to sample about 200 asteroids
for potential satellites using ground-based telescopes
with adaptive optics, a recent technology that corrects
for the distortions caused by the Earth's atmosphere.
Eugenia's moon was found with the Canada-France-Hawaii
telescope, fitted with adaptive optics, on Mauna Kea,
This discovery helps answer questions about the formation
of objects in our solar system. Observing the moon
and the asteroid's gravitational pull on it helped
scientists determine that the asteroid was less dense
than anticipated, indicating that asteroids may not
be composed primarily of rock as once thought. The
moon was probably created by a collision.
The only other sighting of an asteroid's satellite
was by the interplanetary spacecraft Galileo, when
it found a moon around asteroid (243) Ida in 1993.
Editors -- Images of Eugenia's moon will be
available at 2:00 p.m.EDT at: www.boulder.swri.edu/~merline/press_release.