Asteroid cruising past Earth turns out to be two

BEIJING, July 14 (Xinhuanet) -- What at first was thought by scientists to
be a good-sized asteroid currently hurtling past Earth has turned out to be two
giant rocks in tandem.

The setup, catalogued as 2008 BT18, was thought to be nearly a half-mile
wide after its discovery by MIT's LINEAR search program in January. Nothing else
was known about it.

Now seen as two objects orbiting each other, the pair will be closest to
Earth on July 14, at about 1.4 million miles (2 million kilometers) away. That's
nearly six times as far from us as the moon.

It will not strike the planet. But scientists want to learn more about
binary asteroids because one day they might find one headed our way. Deflecting
a binary off course could be considerably more challenging that altering the
path of a single rock.

Radar observations from the Arecibo Observatory in Puerto Rico on July 6
and 7 "clearly show two objects," said Lance Benner of NASA's Jet Propulsion
Laboratory.

The objects are estimated to be 1,970 feet (600 meters) and 650 feet (200
meters) in diameter. The larger one rotates upon its axis in 3 hours or less.

Additional observations from NASA's Goldstone radar in the Mojave Desert in
California are expected to reveal more about the density, shapes and orbit of
the pair.

Asteroids are often loose rubble piles rather than solid objects, and pairs
are common. Scientists announced earlier this month that binaries can be created
when energy from sunlight splits a loose asteroid in two.

(Agencies)