Chelyabinsk meteor exploded almost over a city: "The first explosion was the most powerful, and was preceded by a bright flash, which lasted about five seconds

Chelyabinsk meteor exploded almost over a city: "The first explosion was the most powerful, and was preceded by a bright flash, which lasted about five seconds. Initial newspaper altitude estimates ranged from 30–70 km, with an explosive equivalent, according to NASA, of roughly 500 kilotonnes of TNT (2,100 TJ), although there is some debate on this yield (500 kt is exactly the same energy released by the Ivy King nuclear explosion in 1952). According to a paper in 2013, all these ~500 kiloton yield estimates for the meteor airburst are "uncertain by a factor of two because of a lack of calibration data at those high energies and altitudes." The hypocentre of the explosion was to the south of Chelyabinsk, in Yemanzhelinsk and Yuzhnouralsk. Due to the height of the air burst, the atmosphere absorbed most of the explosion's energy." https://en.wikipedia.org/wiki/Chelyabinsk_meteor https://en.wikipedia.org/wiki/Chelyabinsk_meteor