Saturday 5 January 2019

Fireball meteor over the Bay of Plenty, New Zealand.

Witnesses on North Island, New Zealand, have reported a bright fireball meteor being seen over the Bay of Plenty at about 9.00 pm local time on Saturday 5 January 2019 (about 8.00 am  GMT). The majority of the reports came from California, but sightings were also reported from southern Oregon. 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.

Meteor over the Bay of Plenty on 5 January 2019, as witnessed from the Bay Oval Cricket Ground at Mount Maunganui. New Zealand 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).
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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