[meteorite-list] Sylvia's Companion - Another Moon Found Orbiting An Asteroid

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:35 2004
Message-ID: <200103011740.JAA11954_at_zagami.jpl.nasa.gov>


Sylvia's Companion
Another moon has been found orbiting an asteroid.
by Vanessa Thomas

On February 18, a pair of planetary scientists from the California Institute
of Technology aimed the 10-meter Keck II telescope in Hawaii at an asteroid
known as 87 Sylvia. The resulting images revealed a spot of light hovering
near the 90-mile-wide (130-kilometer-wide) asteroid. Over the next four
nights, other astronomers using the Keck also found the blip and watched as
it circled around Sylvia.

Astronomers are starting to realize that many of our solar system's rocky
wanderers may harbor undiscovered satellites. In 1993, the Galileo
spacecraft discovered the first asteroid moon (later named "Dactyl")
orbiting 243 Ida. Since 1999, several other binary asteroid systems have
been uncovered by radar and visual observations, and many more asteroids are
suspected of hosting satellites. Jean-Luc Margot and Michael Brown are on a
hunt to find these stealthy asteroid companions.

"Our observations are part of an ongoing program to find asteroid binaries
with both optical and radar techniques," Margot explained. "Those systems
provide very valuable information about the composition and internal
structure of asteroids, and also about the collisional history in the main
belt of asteroids and in the inner solar system."

Brown and Margot used the Keck's adaptive optics system to reduce our
atmosphere's blurring effects and differentiate the tiny satellite's light
from Sylvia's. At the time of the discovery, Sylvia and its moon were 2.79
astronomical units (about 260 million miles or 418 million kilometers) away.
Considering the moon's observed brightness, the satellite is likely only a
few miles wide. Temporarily designated S/2000 (87) 1, the moon lies about
745 miles (1,200 kilometers) away from Sylvia and completes an orbit once
every four days.
Received on Thu 01 Mar 2001 12:40:39 PM PST

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