Asteroid to Buzz by Earth Closer Than Satellites

Next week's close encounter will be closest ever observed by NASA.

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An asteroid half the size of a football field could whiz by Earth closer than some satellites next week, according to NASA.

Since scientists began taking sky surveys in the 1990s, none of the nearly 10,000 near-Earth objects discovered have come closer than next week's asteroid, named 2012 DA14, according to NASA's Near Earth Object Program.

Don Yeomans, who heads the Near Earth Object Program, told Space.com that this asteroid definitely won't hit Earth, but will come "extremely close."

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"(The asteroid) is an object that's extremely interesting because it actually passes within many of the satellites that are in orbit around the Earth," Yeomans said. Because of this, Yeomans said his agency gave satellite providers a file of the asteroid's predicted path to ensure they were not in danger of being hit.

"They can take their predictions of where their satellite will be and do comparisons, 'How close will my satellite be to the asteroid?' and so far there's no problem," Yeomans said.

On February 15, the asteroid will fly within 17,000 miles of the Earth's surface, closer than some 400 satellites in geosynchronous orbit, which are often used for satellite television, communications, and weather forecasting, and typically orbit about 22,000 miles up. The asteroid will not come as close as low-Earth orbit, where the International Space Station and many Earth-observation satellites orbit.

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2012 DA14 was discovered by amateur astronomers in February 2012, and has been tracked by NASA ever since.

Yeoman and his team track the orbits of potentially hazardous asteroids and comets to make sure none of the estimated 1,000 that will approach the Earth in the next decade pose any danger.

"When we first discover them we really can't say where in its orbit its going to be at a particular time very accurately," Yeomans told Space.com. "If we can get the radars on them right after we discover them then we can nail their orbit for another 100 to 200 years and just run them out and see if there's a problem. If not, put them aside and go on to the next one."

The 2012 DA14 will be pinged by NASA's Goldstone radar in the Mojave desert. The radar will send a beam at the asteroid, and by measuring how and when it bounces back, scientist can measure its characteristics.

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Through these observations, scientists have determined 2012 DA14 to be a fairly normal asteroid. It is medium-sized — about 45 meters in diameter — and made of stone, as opposed to ice or iron like some asteroids.

Asteroids about the size of 2012 DA14 fly by Earth once every 40 years on average, and strike about once every 1,200 years, according to NASA. Such an asteroid wouldn't cause mass destruction like the kind that likely wiped out the dinosaurs, but it would cause significant damage.

A 50-meter asteroid impacted what would become the United States about 50,000 years ago, levelling the area for 50 miles around, and leaving behind the Meteor Crater in Arizona, though that was made of iron, Yeomans says. Another mysterious object believed to be a meteoroid exploded in the atmosphere above Siberia in 1908, leveling an estimated 500,000 square miles of taiga forest in what has become known as the Tunguska Event.

2012 DA14's medium size, high speed, and south-to-north trajectory mean it will be hard to see for anyone. It will be particularly difficult for sky watchers in the Western Hemisphere, where it will streak across the sky during the day and move twice the width of a full moon every minute, according to Yeomans.

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