On Friday night, Spahr received word that an asteroid was headed our way. Though it received little publicity, the asteroid passed by Earth early Monday. At its closest, the asteroid, named 2009 DD45, came within 45,000 miles of Earth, which is around twice as high as some satellite orbits and about one-fifth of the distance between the moon and Earth.
The cosmic object, which was estimated to be 20 yards to 30 yards across, came closest to Earth near the equator somewhere over the Pacific Ocean.
It was about the same size as the one that burned up over Siberia in 1908, leveling nearly 800 square miles of forest in the infamous "Tunguska Event" event.
"It's pretty unusual to see one this close," said Spahr, director of the minor-planet center at the Harvard-Smithsonian Center for Astrophysics in Cambridge. "If an object of this size were to impact the Earth, it would be equivalent to a small nuclear explosion."
Brian Marden, a senior astronomer at the center, said that many such objects pass this close but go unobserved.
Asteroid Near Misses Common
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