Many people have reported seeing a bright fireball over parts of southern Saskatchewan and Manitoba at about 8.40 pm local tine on Sunday 8 November 2015. 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. The
bright lights seen in fireballs are caused by airbursts in which rocky
meteorites explode due to friction induced heating high in the
atmosphere, and any fragments reaching the ground usually do so several
minutes later. On this occasion many people reported hearing sonic booms in the area around Kelvington in east central Saskatchewan, which astronomer Martin Beech of the University of Regina suggests may indicate that the object broke up low in the atmosphere, potentially with fragments reaching the ground.
The 8 November 2015 fireball meteor seen from Ralph, Saskatchewan. Bill Allen/Facebook.
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. It is possible, though unlikely,
that this object will have produced meteorites that reached the surface
(an object visible in the sky is a meteor, a rock that falls from the
sky and can be physically held and examined is a meteorite), though most
meteorites come from larger objects that penetrate further into the
atmosphere before exploding, and therefore have a better chance of
producing fragments that reach the surface.
On this occasion the meteor is thought likely to be part of the Taurid Meteor Shower, which lasts from about 10 September to about 10 December, with two peaks on 12 November and 10 October. The Taurids are associated with Comet Encke, and occur as the Earth passes through the trail of the comet, though the comet is an ancient resident of the Inner Solar System, probably having been here for 20 000-30 000 years, and over that time has largely disintegrated due to the heat of the Sun (a fate which eventually overtakes any comet which is knocked from its orbit in the Outer Solar System into the Inner Solar System), meaning that fragments of the comet are scattered in a wide area loosely following the orbital path of the comet. The Taurids are unusual for a meteor shower in that they never produce the large number of small meteors seen at the peak of other such showers, but rather a small number of bright, large fireballs, suggesting large pieces of more durable material than cometary ice have been shed over time as the comet has slowly broken up.
See also...
Fireball over northern Europe. Eyewitnesses across much of northern Europe reported seeing a bright
fireball in the sky moving southwest to northeast at about 6.05 pm GMT
on Saturday 31 October 2015. The event was seen from the Netherlands,
Germany, Denmark, southern...
The 2015 Perseid Meteors. The
Perseid Meteor shower lasts from late July to early September each
year, and are expected to be at a peak on 12-13 August 2015, which
falling slightly before the new moon of 14 August, should meanf...
2015's Eta Aquarid Meteors. The
Eta Aquarid Meteor Shower will be at a peak on Tuesday 5/Wednesday 6
May 2014, with up to 45 meteors per hour at it's peak, radiating from
the constellation of Aquarius. This does not spend...
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