Asteroid sets course for near-collision

Half-mile-wide rock to whiz by Aug. 7, 2027


WASHINGTON -- In the cosmic equivalent of a bullet whizzing by Earth's ear, a half-mile-wide asteroid looks as if it will come closer to smashing into our planet than any other space rock astronomers have tracked.

It won't hit Earth. But its arrival in 28 years will be a visible reminder that space can be a dangerous place.

After computing a new path for the dangerous rock, NASA scientists and other astronomers determined this week that the asteroid will come close -- but definitely not hit -- Earth on Aug. 7, 2027.

The asteroid could swing as close as 19,000 miles from Earth's surface. That's only one-twelfth the distance between here and the moon.

"It is indeed very interesting," said Paul Chodas, a research scientist in NASA's Near Earth Object tracking office. "We're taking it seriously."

Because this asteroid was discovered only in January, astronomers aren't certain how close the call will be. While 19,000 miles is the closest it can come in 2027, it could miss by as much as 600,000 miles. The most likely miss will be by 32,000 miles, Chodas said.

Astronomers are certain it won't hit Earth because its current path and the pull of gravity put it on a track that cannot intersect with Earth's orbit, Chodas said.

But the newest tracks put the asteroid, called 1999AN10, on top of the list of close shaves compiled by Harvard University's Minor Planet Center. This asteroid will likely come nearly 15 times closer to Earth than the next known near-collision, an asteroid that will approach Earth in 2086.

If it comes as close as 19,000 to 32,000 miles, the rock should be visible with the naked eye, Chodas said. It would look like a moderately bright star.

"We're not used to thinking about things being that close," said Clark Chapman, a planetary scientist at the Southwest Research Institute in Colorado. "They've been coming that close for a long time; we just haven't known about it."

There is a very slight chance -- one in 10 million -- that when 1999AN10 gets close to Earth in 2027, our planet's gravity will shift the asteroid's path in such a way that it will come within 5,000 miles in 2034 and hit us in 2039, Chodas said.

This asteroid has been a source of contention among scientists for two months. That's because a paper by Italian and American astronomers that mentioned the possible 2039 crash was made public -- against the scientists' wishes -- by a science-oriented Internet bulletin board.

Next month, astronomers will meet in Italy to discuss how such expected near-collisions should be revealed to the public.

Pub Date: 5/21/99

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