Close call: Asteroid misses Earth by 17,000 miles

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By Thomas Scott

Last Friday, two unrelated cosmic events gripped the public imagination and the international media’s attention.

First, a meteor struck a rural part of the Russian Federation causing widespread injury and panic.

Then, a 160-foot wide asteroid known to astronomers as 2012 DA14 passed within 17,000 miles of Earth.

To better understand why 2012 DA14’s approach was called a “close passage,” one should note that satellites in geostationary orbit (orbits which match the Earth’s own rotation) are more than 22,000 miles away from our planet’s surface.

There is a potent risk from unchecked near-Earth objects, according to Union’s Observatory Manager and Physics and Astronomy Lecturer Francis Wilkin.

“One way to think about it is… if you have an asteroid of a certain size, it’s going to create a crater… [that’s] usually 20 times the size of the asteroid,” explained Wilkin.

However, 2012 DA14 passed the earth during the day at 2:25 p.m. in the afternoon, and was not visible to the naked eye, but was visible through powerful binoculars.

The object was spotted a year ago this Saturday by a remotely operated Spanish observatory, but astronomers knew from the outset that there was little chance of a terrestrial impact.

Meanwhile in a remote section of Russia, calamity arrived in the form of a meteorite which allegedly injured nearly 1,500 people and caused a row among some of the nation’s politicians.

Vladimir Zhirinovsky of the hyper-nationalist Liberal Democrat Party was insistent that the fireball was “not a meteorite falling,” but “a test of new American weapons.”

In reality, the entity that exploded over Chelyabinsk Oblast in the Urals Mountains was a meteor several meters in diameter and composed of ordinary chondrite, the most common of meteoric contents.

Several of the meteor’s pieces came to rest in and around Lake Chebarkul, a body of water located in Chelyabinsk Oblast. One segment of the meteor pierced the lake’s ice, causing the scientific community to confer the name of Chebarkul Meteorite upon the object’s remnants.

When the meteor exploded midair its estimated energy was equivalent to 500 kilotons of TNT, which dwarfs the nuclear detonation that leveled Hiroshima by a factor of 30.

The Chebarkul Meteorite was the largest object to enter the atmosphere since the notorious Tunguska event back in 1908.

In the Tunguska event, a 10 to 15 megaton blast occurred in Siberia.

Explanations for the event range from the midair explosion of a comet or asteroid to less accepted hypotheses, such as the occurrence of nuclear fusion or an antimatter annihilation.

Wilkin argues that “the [event] in Russia is a good warning because if a rock that’s only a couple meters across can put a thousand people in the hospital… imagine if you have one half the size of a football field.”

There has been a considerable effort on the part of the scientific community to catalogue asteroids that pose a threat to human civilization.

“Anything big enough to endanger human civilization is going to be large enough that…astronomers will know about it months or years in advance,” says Wilkin.

An act of Congress in 1998 mandated that NASA locate 90 percent of all near-Earth objects larger than 3,300 feet across. As of 2011, the agency has located 93 percent, with a remaining 70 asteroids yet to be spotted.

Union’s observatory spotted and photographed an asteroid called 2005 YU55. That object was discovered by Robert McMillan eight years ago. McMillan is the director of the  Spacewatch project at the University of Arizona.

The asteroid didn’t pass as close as 2012 DA14, instead moving within 200,000 miles of the Earth.

To put that into perspective, the moon is 238,900 miles away from the Earth.

For more information, check out NASA’s Near Earth Object Program online at neo.jpl.nasa.gov.

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