Large Asteroid to Fly Past Earth

by Jeanna Bryner, Staff Writer

Date: 24 January 2008 Time: 12:39 PM ET

An asteroid that's likely as big as several football fields will fly past Earth next week. Astronomers said the space rock will be visible the night of Jan. 29 to amateur astronomers with modest-sized telescopes.

Called 2007 TU24, the asteroid was discovered by NASA's Catalina Sky Survey on Oct. 11, 2007. It is estimated to be somewhere between 500 feet (150 meters) to 2,000 feet (610 meters) in diameter.

The asteroid makes its closest approach to Earth, 334,000 miles (537,500 kilometers), at 3:33 a.m. Eastern time (12:33 a.m. Pacific time). For comparison, the moon is an average of 239,228 miles (385,000 kilometers) away.

"This will be the closest approach by a known asteroid of this size or larger until 2027," said Don Yeomans, manager of the Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif.

However, that doesn't mean we won't hear about another flyby of this nature before then. With relatively small space rocks, like this one, astronomers sometimes don't know they're passing through until right before they do.

There is no danger of the asteroid striking Earth in the foreseeable future, the scientists said.

But if an asteroid with this size were to hit Earth, the results could be regionally devastating. The impact itself would release about 1,500 megatons of energy, creating a crater about three miles (nearly five kilometers) wide and kicking up loads of debris, according to Yeomans.

"If it hit in the ocean, which is more likely because two thirds of the Earth is ocean, it would create a tsunami, which would be devastating for the coastlines that happen to be nearby," Yeomans told SPACE.com. "It would be a huge local problem and the tsunami would be extraordinary if it hit in the ocean."

"As its closest approach is about one-and-a-half times the distance of Earth to the moon, there is no reason for concern," Yeomans said. "On the contrary, Mother Nature is providing us an excellent opportunity to perform scientific observations."

At its nearest, the asteroid will reach an approximate apparent magnitude 10.3, which is about 50 times fainter than an object visible to the naked eye in a clear, dark sky. Then, it will quickly become fainter as it moves away.

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.

Given the estimated number of near-Earth asteroids of this size (about 7,000 discovered and undiscovered objects), astronomers would expect an object of this size to pass this close to Earth every five years or so on average. And about every 37,000 years on average, an object this size would be expected to actually impact Earth.

Astronomers have catalogued hundreds of asteroids larger than a half-mile across that pass in the vicinity of Earth's orbit. However, none of these are known to be on a collision course with our planet.