WASHINGTON (AP) - The human race
doesn't have to worry about a collision with a recently discovered asteroid
in 2028, astronomers at NASA's Jet Propulsion Laboratory say. The asteroid
will pass by the Earth no closer than 600,000 miles, say Donald K. Yeomans
and Paul W. Chodas. The pair recalculated the orbital path of the asteroid
using photos taken by the Palomar Observatory telescope in 1990. The announcement
comes a day after a group of astronomers reported that the asteroid would
pass within 30,000 miles of the Earth's center and could possibly collide.
The astronomers who made the original prediction could not immediately
be reached for comment.
WASHINGTON - A mile-wide asteroid described as "the most dangerous
one we've found so far" may be on course for a 2028 collision with
Earth and certainly will pass closer than any such object in modern times,
astronomers said Wednesday.
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- "The chance of an actual collision
is small, but one is not entirely out of the question," according
to a notice filed by the International Astronomical Union. But asteroid
specialist Jack G. Hills said the speeding space rock, called asteroid
1997 XF11, poses a real danger to Earth.
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- "This is the first really big one
to pass this close," said Hills, a Los Alamos National Laboratory
scientist. "This is the most dangerous one we've found so far."
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- He added: "It scares me. It really
does. An object this big hitting the Earth has the potential of killing
many, many people."
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- "It has enormous destructive potential,"
agreed Steven Maran of the American Astronomical Society, but he added
it will take several more years of observations before experts are certain
of its path
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- Asteroid 1997 XF11 was discovered Dec.
6 by the University of Arizona Spacewatch program and was added to a list
of 108 asteroids considered to be "potentially hazardous objects."
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- Maran noted that no asteroid the size
of 1997 XF11 has ever been predicted to pass so close to the Earth.
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- Asteroids are routinely observed and
plotted by astronomers around the world because of their potential for
great destruction on Earth.
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- An asteroid 6 to 10 miles across collided
with the Earth about 65 million years ago and is thought to have caused
the extinction of the dinosaurs, along with 75% of all other species.
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- Hills said an asteroid the size of 1997
XF11 colliding with the Earth at more than 17,000 miles an hour would explode
with an energy of about 320,000 megatons of dynamite. That equals almost
2 million Hiroshima-sized atomic bombs.
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- Such an asteroid hitting the ocean, said
Hills, would create a tidal wave hundreds of feet high, causing extreme
flooding for thousands of miles of coast line.
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- "If one like this hit in the Atlantic
Ocean, all of the coastal cities would be scoured by the tsunami,"
said Hills. "Where cities stood, there would be only mudflats."
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- If such an asteroid hit on land, he said,
it would instantly dig a crater 20 miles across and so clog the sky with
dust and vapor that the sun would be darkened "for weeks, if not months."
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- Maran said the best estimate is that
the mile-wide 1997 XF11 will pass inside the orbit of the moon, with the
most likely separation from the center of the Earth of about 30,000 miles.
The Earth has a radius of about 4,000 miles.
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- The estimate, said Maran, has a margin
of error of more than 180,000 miles. This means a collision with Earth
is theoretically possible, but uncertain at this time, he said.
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- Better estimates of the collision potential
will be generated as astronomers plot the course of the asteroid through
the heavens over the next few years.
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- Observations made earlier this month
by University of Texas astronomers indicated the asteroid would make its
nearest approach to the Earth on Oct. 26, 2028, at about 1:30 p.m. EDT.
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- "There is still some uncertainty
to the computation," said the bulletin from the International Astronomical
Union.
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- The notice said the asteroid, which is
on a wide-swinging, independent orbit of the sun, will move out of view
to all but the largest telescopes over the next few months. It will become
more visible once again in 2000. And in 2002, it is expected to pass within
about 6 million miles of Earth on Halloween Eve.
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- Hills said the asteroid is lost from
view when it passes behind the sun, but that it will emerge into telescope
range about every two years.
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- Astronomers eventually will be able to
track the object using radar, he said, and this will enable them to establish
a precise orbital path years ahead of the possible impact. Only then, said
Hills, will the true risk of collision be known.
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- Experts long concerned about the potential
danger of asteroids have said the Earth could be protected by exploding
a missile near the speeding rock while it was far away. The intent would
be to nudge the asteroid onto a path that would send it safely away from
the planet.
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- "If it is going to hit the Earth,
there's no question that we should try to deflect it," said Hills.
"It would be money well spent."
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- By The Associated Press
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