Updated 8:30 a.m. ET Jan. 29
Astronomers have obtained the first images of an asteroid on course to make its closest
approach to Earth Tuesday, showing the space rock is lopsided.
The new
images, taken with the Goldstone Solar System Radar Telescope in California's Mojave Desert, refine estimates of the asteroid's size. Named 2007 TU24, the
asteroid was estimated to span up to 2,000 feet (610 meters), but is now
thought to have a diameter of about 800 feet (250 meters).
Scientists
at NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., have determined that there is no possibility of an impact with Earth in
the foreseeable future.
As the
asteroid moved nearer to Earth, on Jan. 28, the Arecibo Observatory in Puerto
Rico working with the Robert C. Byrd Green Bank Telescope in W. Va. produced
another image of the asteroid. Astronomers used the Arecibo telescope, which is operated by Cornell University on behalf of the National Science Foundation, to bounce
radar signals off the asteroid. The Green Bank Telescope received the echo
signal and transmitted the data back to Arecibo to be transformed into an
image.
Other radar
telescopes were expected to point toward the
asteroid as it made its closest approach to Earth, 334,000 miles (537,500
kilometers), at 3:33 a.m. Eastern time Jan. 29. For comparison, the moon is an
average of 239,228 miles (385,000 kilometers) away.
At its
nearest, the asteroid will reach an approximate apparent magnitude 10.3, or
about 50 times fainter than an object visible to the naked eye in a clear, dark
sky. Then, it will quickly get fainter as it moves away.
The
combination of these telescopes will provide higher resolution images of the
asteroid. Measurements from Arecibo's radar telescope will gauge the object's
size more precisely, its speed and spin.
Like other asteroids,
this one orbits the sun. Most do so in the asteroid belt between Mars and
Jupiter. NASA pays particular attention to those whose orbits bring them so
close to Earth.
TU24,
discovered by NASA's Catalina Sky Survey on Oct. 11, 2007, is one of an
estimated 7,000 near-Earth objects identified to date (another 7,000 are
estimated to exist but are yet to be discovered).
"We
have good images of a couple dozen objects like this, and for about one in 10,
we see something we've never seen before," said Mike Nolan, head of radar
astronomy at the Arecibo Observatory. "We really haven't sampled the
population enough to know what's out there."
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