Witnesses in Slovenia, Serbia, Croatia and northern Italy reported have seeing a fireball meteor on Firday 28 February 2020. The object was seen moving southeast to northwest over southern Slovenia slightly before 10.35 am local time (slightly before 9.35 am GMT). A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These 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.
Dust trail left by a meteor over southern Slovenia on 28 February 2020. Such trails are caused by material ablating of the surface of the object due to friction with the Earth's atmosphere. Istramet.
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).
Heat map of the area surrounding the northern Adriatic showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.
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.
The 28 April 2020 fireball meteor seen from Zagreb in Croatia. Tomislav Čar/YouTube.
On this occasion the airburst was detected as an Earthquake by several seismic stations in southern Slovenia, leading the Geological Survey of Slovenia to conclude that this was an object of some size, and that there is a high likelyhood that some fragments of the original object made it to the ground.
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