NBC News reports:
Scientists have raised their estimates of the size and power of what turns out to be the most widely witnessed asteroid strike in modern history. The size estimate puts the object that caused Friday's meteor blast over Russia in a troublesome category of asteroids: big enough to cause damage, but small enough to evade detection.
The new estimates, based on additional readings from a sensor network built to detect nuclear blasts, suggest the meteor released the energy equivalent of nearly 500 kilotons of TNT. That's about 30 times the power of the Hiroshima atomic bomb.
... NASA now says the Chelyabinsk object must have been about 55 feet wide (17 meters wide) with a mass of 10,000 tons before it entered Earth’s atmosphere.
... Experts emphasized once again that the meteor's trajectory was significantly different from the path of asteroid 2012 DA14, a 150-foot-wide (45-meter-wide) space rock that passed harmlessly within 17,200 miles (27,600 kilometers) of Earth later Friday. Thus, 2012 DA14 was "a completely unrelated object," NASA said.