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Asteroid 2004 BL86 flew about 745,000 miles (1.2 million km)
from Earth, about three times farther than the moon, with
closest approach coming at 11:19 a.m. EST (1619 GMT) on Monday.
While it posed no threat to Earth, the flyby did provide
astronomers an opportunity for some close-up studies without
having to launch and operate a robotic probe.
Radar images taken by NASA's Deep Space Network antenna in
Goldstone, California, show the 1,100-foot (325 meter) wide
asteroid has a small moon in orbit, NASA said.
The moon is about 230 feet in diameter, NASA said.
About 16 percent of asteroids that are about 655 feet or larger
are a binary - with a primary asteroid and a smaller asteroid
moon - or even triple systems, with a primary body and two
moons, NASA said.
Related images taken with an infrared telescope in Hawaii show
the asteroid is primarily basalt, with a composition similar to
lava flows found in Hawaii.
Asteroids of this type are believed to be pieces of Vesta, a
large protoplanet circling in the main asteroid belt between
Mars and Jupiter, that were blasted into space by impacts, NASA
said.
Monday's flyby was the closest Asteroid 2004 BL86 will come to
Earth for at least the next 200 years.
(Reporting by Irene Klotz, editing by G Crosse)
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