Researchers from the University of Calgary have found a number of fragments of meteorite believed to have come from an object that entered the atmosphere over British Colombia on 29 September 2017. The object entered the atmosphere roughly above the town of Boswell and exploded in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) close to Meadow Creek., a distance of about 100 km. The meteor is described as initially burning green, then orange, with people close to the termination point reporting a loud explosion. Following a search a number of fragments of rock believed to have come from the object have been found on private land near Crawford Bay, roughly 30 km to the south of Meadow Creek.
Fragment of meteorite found near Crawford Bay, British Columbia, and thought to have come from the 29 September 2017 meteor. Surrey Now-Leader.
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 near Nelson in British Colombia on 4 September 2017. Rafael Pern/Twitter.
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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