The videos and other data allowed the trajectory to be worked out and the velocity to calculated very accurately at a brisk 68,400 km per hour (42,500 miles per hour) and at a low angle of 17 degrees. It reached its peak brightness 29 kilometers up (18 miles). From this they calculated that before the meteor hit our atmosphere, it was about 20 meters in diameter and weighed about 1,200 tonnes (1,300 U.S. tons).
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From satellites sensors that recorded flash of light - which is estimated to be 20 percent of the total energy released by the meteor - put the radiant energy at about 90 kilotons. So that number times five gives a total energy of 450 kilotons, which agrees with infrasound and other measurements, the researchers report. Because the meteor entered at such a low angle, all that explosive energy was released along a line over 16.5 seconds - which was a good thing.
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"The blast was distributed over a large area, and was much weaker than for a steep entry and a more concentrated explosion closer to the surface," the researchers report.