Wide-ranging data contribute to understanding of Chelyabinsk meteor

New York Times : The large number of videos posted online of last month’s explosion of the asteroid-turned-meteor near Chelyabinsk, Russia, are part of the unprecedented level of study given to such a rare, large impact. According to the latest estimates, the meteor was approximately 18 m in diameter and entered the atmosphere traveling at roughly 19 km/s. The videos allowed researchers to determine that the meteor exploded at an altitude of more than 24 km, with the shockwave arriving in the city 88 seconds later. One of the reasons it exploded as high as it did is because it was a chondrite , or stony meteorite. If it had been metallic, it might not have exploded until it struck the ground, which would have been devastating. Acoustic sensors positioned around the planet to monitor nuclear tests also recorded the explosion, which was calculated to have been equivalent to 440 kt of TNT, roughly 30 times the power of the Hiroshima nuclear bomb. Several groups of researchers have used videos to determine the meteor’s trajectory and orbit. They believe it is likely that Jupiter’s gravity popped the rock out of orbit in the asteroid belt and sent it into an Earth-crossing orbit. One group hopes to be able to determine the meteor’s path accurately enough to find evidence of it in photographs of other near-Earth objects.