GAUTAM NAIK and ALAN CULLISON
Wall St Journal 
Feb 19, 2013
The meteor that crashed to earth in Russia was about 55 feet in diameter, weighed around 10,000 tons and was made from a stony material, scientists said, making it the largest such object to hit the Earth in more than a century.
Large pieces of it have yet to be found. However, a team from Ural Federal University, which is based in Yekaterinburg, collected 53 fragments, the largest of which was 7 millimeters, according to Viktor Grokhovsky, a scientist at the university.
Data from a global network of sensors indicated that the meteor’s fiery disintegration as it neared earth near Chelyabinsk, Russia, unleashed nearly 500 kilotons of energy, more than 30 times the energy of the Hiroshima atomic bomb.
It is the largest reported meteor since the one that hit Tunguska, Siberia, in 1908, according to the National Aeronautics and Space Administration. The U.S. agency’s new estimate of the meteor’s size was a marked increase from its initial one.