150-foot asteroid flies by Earth

A 150-foot asteroid hurtled through Earth's backyard Friday, coming within 17,150 miles and making the closest known flyby for a rock of its size. Unlike the meteor that streaked over Russia in a cosmic coincidence, the encounter caused no harm.

The asteroid delighted astronomers in Australia and elsewhere who watched it zip harmlessly through a clear night sky.

Asteroid 2012 DA14, as it's called, came closer to Earth than many communication and weather satellites orbiting 22,300 miles up. Scientists had predicted these, too, would be spared, and they were right.

The asteroid was too small to see with the naked eye even at its closest approach around 2:25 p.m. Eastern, over the Indian Ocean near Sumatra, buzzing by at 17,400 mph.

As asteroids go, it is a shrimp. The one that wiped out the dinosaurs 65 million years ago was 6 miles across. But a rock the size of 2012 DA14 could still do immense damage if it ever struck given its 143,000-ton heft, releasing the energy equivalent of 2.4 million tons of TNT and wiping out 750 square miles.

Most of the solar system's asteroids are situated in a belt between the orbits of Mars and Jupiter, and remain stable there for billions of years. Some occasionally pop out, though, into Earth's neighborhood. NASA scientists estimate that an object of this size makes a close approach like this every 40 years. The likelihood of a strike is every 1,200 years. -- AP