Earth will have a close call tonight. An asteroid that’s big enough to cause major damage will pass just 708,000 miles away — about three times the distance from Earth to the Moon.

2005 LW3 is classified as a potentially hazardous asteroid — one of about 2200 that we know of. Such asteroids could hit us. And if they’re big enough, they could inflict major harm.

In 2013, for example, an asteroid just 65 feet in diameter exploded high above the Russian city of Chelyabinsk. The shockwave injured about 1500 people, mostly from flying bits of glass. And in 1908, an asteroid about three times that size exploded above Tunguska, in Siberia. It flattened 500,000 acres of forest, and may have killed three or more residents.

2005 LW3 is much bigger than either of those — about 400 to 900 feet in diameter. At that size, it would either explode high in the air or slam into the ground. Either way, the blast would be the equivalent of thousands of big nuclear bombs — powerful enough to destroy a city.

Close encounters like this one are common. A much smaller asteroid passed much closer just a week ago, for example. And another big one will pass a little closer on Christmas Day.

Most potentially hazardous asteroids are small. And so far, none of them is on a known collision course. But astronomers discover new ones all the time — potentially deadly space rocks.

Script by Damond Benningfield

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