Monday 21 December 2020

Fireball Meteor over the southern North Sea.

Witnesses across much of northwest Europe have reported observing a bright fireball at about 8.15 pm local time GMT on Sunday 20 December 2020. The fireball is described as having moved from northwest to southeast, with some witnesses in England and the Netherlands reporting an audible boom which accompanied the meteor. 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. 

Fireball meteor (top left of image) seen from De Weere in the Netherlands on 20 December 2020. Frank Breedijk/American Meteor Society.

The fireball was seen from Belgium, the Netherlands, England, Scotland, and Germany,has been calculated to move from northwest to southeast the Southern North Sea, dissapearing about 30 km off the coast of the Netherlands

Heat map of northwest Europe 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.

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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