ASTEROID TO BUZZ EARTH THIS WEEK: When the sun rose over Chelyabinsk, Russia, on Feb. 15, 2013, at first it seemed like an ordinary day. Then the space rock hit. Without warning, the morning sky lit up with a second sun as shock waves shattered windows in hundreds of buildings around the wakening city.
Above: That's not the sun; it's the Chelyabinsk fireball on Feb. 15, 2013. [video]
The impactor flew out of the blue, literally from the direction of the sun where no telescope could see it, and took everyone by surprise. Years later, meteorite hunters are still finding pieces of the "Chelyabinsk asteroid" that rained down after its 17m-wide body disintegrated in the atmosphere.
A similar asteroid is approaching Earth this week, but this time NASA knows its coming. 2012 TC4 measures somewhere between 10 m and 30 m wide, and on Oct. 12th it will pass 43,500 km above our planet's surface, about 1/8th the distance to the Moon. The flyby is so close, Earth's gravity will significantly alter the asteroid's trajectory before it exits the Earth-Moon system.