Witnesses across southern Russia reported seeing a bright fireball meteor (a shooting star brighter than Venus) on Thursday 21 June 2018, according to the International Meteor Organization. The object apparently exploded over Lipetsk Oblast (Lipetsk State) at about 4.15 am local time, but witnesses have reported seeing it from as far away as Moscow. The object is estimated to have exploded with a force of about 3.2 kt TNT (roughly a fifth of the explosive power of the Hiroshima bomb), which suggests an object less than five metres across exploding more than 40 km above the ground.
Fireball meteors are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry. Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus.
The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).
These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.
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