May 18th, 2012
12:05 PM ET

The Number: Run for your lives...potentially hazardous asteroids

NASA has given an update on what they call P-H-As, potentially hazardous asteroids.

In order for an asteroid to be deemed a potential hazard, they have to come within 5 million miles of Earth and have a diameter of a 100 meters.
Just to give you an idea, if Earth were to be struck by an asteroid 40 meters across, it would be similar to the impact of a 3 megaton nuclear bomb.
So how many potentially hazardous asteroids are there?

That's our number tonight: 4,700

It's just an estimate, NASA says that number is plus or minus 1,500 and that they've only found about 20 to 30 percent of them.

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