Written by Kelly Herbst, Astronomy Curator for the Virginia Living Museum. Updated every two weeks, more or less.

Wednesday, February 13, 2013


I hope you found those to be nice, friendly letters.

At any rate, truly, there is no need to panic.  Friday will come and go, and we will NOT be destroyed by a giant rock from space.  Truly, we won't.

You've probably heard about asteroid 2012 DA 14 (yes, that's really the only name it has!), which will be making an extraordinary pass by Earth this Friday.  In fact, here's the official details:

Asteroid: 2012 DA 14
Date: Friday, February 15, 2013
Time: 2:24PM EST
Distance at closest approach: 17,200 mi from Earth
Size of asteroid: 164 ft. wide
Composition: Stone
Chance of impact: ZERO

Did you read that last bit?  There is a ZERO chance that 2012 DA 14 will hit the Earth this Friday.  Zero. Zilch.  Nada.  None.  No chance at all.  Not even if it happens to hit a satellite (which is terrifically unlikely) - it cannot possibly "bounce" off a satellite and hit the Earth.  It simply will not happen.

So, what will happen?

This asteroid will zip past our planet a bit inside the orbit of the geosynchronous satellites.  Those satellites handle things like weather and communications, among others.  The rock will go outside the GPS satellites, however.  So while it will be close to won't be that close to us. 

Some folks are hoping to be able to see this rock as it zips past.  That will be extremely difficult, for several reasons.  First of all, it will be moving a good clip...17,400 mph, in fact.  That means it will move across the sky about 1 degree per minute - tough to track, that's for sure.  And you'll need to track it, because it won't be visible to the unaided eye.  Even coming so close, the rock is so small, you'll need at least a pair of binoculars to see it at all.  And one other small'll need to be in the middle of the Indian Ocean.  Sumatra will get a nice view.  So...not much of an event here in the U.S.

But now, let's tackle the juicier question...what if the scientists are wrong? (They're not.)  What if it does hit us after all?  (It won't.)

Okay, let's consider it.  What would happen if 2012 DA 14 hit the Earth?  Lucky for us, we've got some good models for that...because they've already happened.  (insert gasp of surprise here)

2012 DA 14 is about the same size as the asteroid that impacted the U.S. some 50,000 years ago just outside of what is today Winslow Arizona.  That meteor struck the ground and blasted a hole in the Earth 4,000 feet in diameter, and 570 feet deep.  You can visit the crater today - it's called Barringer Meteor Crater.  

Barringer Meteor Crater in Arizona

Now, the meteor that created Barringer Meteor Crater was made largely of iron.  2012 DA 14 is a stony object.  So it would not impact with nearly the same amount of force.  In fact, it probably would not impact at all...the stress of enter Earth's atmosphere at a high rate of speed would likely shatter the rock before it ever made it to the ground.  We've got a model for that too.  On June 30, 1908, a meteor about the size of 2012 DA 14 exploded over the Podkamennaya Tunguska River in Siberia.  The blast leveled 830 square miles of forest, and likely measured 5.0 on the Richter scale.  The energy of the blast was about 1,000 times as much as that from the atomic bomb dropped on Hiroshima by the United States.  If a blast like this occurred over a major population center, the results would most certainly be unpleasant.  But not Earth destroying, by any means.

Trees leveled by the Tunguska explosion in 1908.
So...long story short....Friday will be a great day for scientists who study asteroids...and maybe even for a few amateurs who can get photographs of our celestial visitor...but for most of us, it will simply be another day on planet Earth.

Until the next close shave...
Carpe noctem!

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