Witnesses in Alberta, British Columbia and Saskatchewan reported seeing a fireball meteor on Saturday 8 February 2020. The object was seen moving weast to east over southern Alberta slightly after 4.05 pm local time (slightly after 0.05 am on Sunday 9 February, 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.
Daytime fireball meteor over southern Alberta. Mobizen/Calgary Herald.
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 western Canada
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.
On this occasion Fabio Ciceri of the Dapartment of Geoscience at the University of Calgary has estimated that the object may have weighed around 500 kg, and that there is a strong likelyhood of material from it having reached the ground intact. The University of Calgary team maintain a series of cameras accross the province which are calibrated to help determine the trajectories of meteors. However, as this object fell during the daytime the amount of recoverable footage was rather limited, and they are interested in hearing from any members of the publich who may have recorded the event.
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