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Posted at 02:04 PM ET, 09/13/2012

Close asteroid encounter tonight exposes potential hazard


A representation of near-Earth and potentially hazardous asteroids in our solar system. More info. (NASA)
This relatively large 625 feet to 1,400 feet wide body will zip by no closer than about 7.5 times the distance to the moon (1.8 million miles).Officially, it has been designated a “potentially hazardous asteroid” (PHA) by the Minor Planet Center, applied to any asteroid (or comet) which may pose a threat (though this one does not).

During its passage 2012 QG42 will be opposite the sun from the Earth and therefore relatively bright, but not bright enough for viewing by the small telescopes typically used by amateur astronomers (like myself).

However, two online observatories are tracking the 2012 QG42’s pass by Earth. The Virtual Telescope Project in Italy will begin began providing a live video stream today at 6 p.m. The Slooh Space Camera night sky observing website will begin a live view of the asteroid’s closest approach starting at 7 p.m., offering views from at least one of its telescopes in the Canary Islands.

Video: Background on asteroid 2012 QG42 from Slooh Space Camera

The passage of 2012 QG42 is not an isolated incident. As noted in an earlier post, a much smaller, 30 feet in size asteroid came within 7,500 miles of Earth on June 27, 2011, following an even closer encounter of a small body earlier that missed earth by only 3400 miles. Small asteroids such as these would likely just produce a brilliant fireball with only small fragments reaching the earth’s surface.

Intermediate-sized asteroids like 2012 QG42 are capable of serious damage to life and human dependent infrastructure should they collide with Earth. Nominally, should they be directed towards Earth, asteroids of this size are likely to be observed and followed with months to years of advanced notice (for whatever that’s worth in some strategy for diverting it away). But, 2012 QG42 was discovered less than a month before its closest approach. Although further distant (3.2 million miles), the same is true of asteroid 2002 AM31 that whizzed by three months earlier on July 22.

Closer to home an asteroid about 200 feet wide came within 40,000 miles of Earth on March 2, 2009 only a few days after being discovered. Though 40,000 miles might seem a safe distance it was most certainly a close call in astronomical terms. Had it struck the earth it would have exploded with the force of a large nuclear bomb

More recently, an obviously large (but dimensions unknown) crashed without notice on Jupiter on September 10. Watch: Video .

Bob Berman, Astronomy Magazine columnist, notes that Near Earth Objects such as these“have been whizzing past us lately, undetected until they have been practically on top of us”. He adds, “”It is not a question of if, but when such an object will hit us, and how large and fast it may be going.”

Note: According to Earth Sky, a NASA survey suggests the presence of roughly 4,700 potentially hazardous asteroids. So far, only 70 to 80 percent of these objects have been found

Other recent asteroid close calls

Big asteroid to zip by Earth tonight (June 14, 2012)

Asteroid to just miss Earth on tonight’s flyby (November 8, 2011)

By  |  02:04 PM ET, 09/13/2012

Categories:  Astronomy, Space, Latest, Tracton

 
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