Washington, Nov 26 : Investigation of the fireball that lit up the skies of Alberta and Saskatchewan in the US on November 20 has determined that it was caused by an asteroid fragment weighing approximately 10 tonnes.
The investigation was conducted by University of Calgary researcher Alan Hildebrand, who has outlined a region in western Saskatchewan where chunks of the desk-sized space rock are expected to be found.
The fireball first appeared approximately 80 kilometers above and just east of the border city of Lloydminster, Alberta/Saskatchewan, and traveled SSE towards the Battle River valley, fragmenting spectacularly in a series of explosions.
It penetrated the atmosphere at a steep angle of approximately 60 degrees from the horizontal and lasted about five seconds.
The fireball was recorded on all-sky and security cameras scattered across Saskatchewan and Alberta, in addition to being witnessed by tens of thousands of people who saw it streak across the sky, saw its arc- welding blue flash, or heard the subsequent explosions.
According to Hildebrand, the fireball was like a billion-watt lightbulb shining in the sky, turning night into day with a bluish white light.
It illuminated the ground for several hundred kilometers in all directions including as far south as Vauxhall, Alberta.
"Thanks to everyone's help we are now beginning to delineate the trajectory of the fireball, so that its prefall orbit can be determined. We have also outlined an area where its meteorites may have fallen, although we will have more precise predictions to come," said Hildebrand.
The asteroid fragment is now known to have weighed approximately 10 tonnes when it entered the Earth's atmosphere from an energy estimate derived from infrasound records by Dr. Peter Brown, Canada Research Chair in Meteor Physics at the University of Western Ontario.
"At least half a dozen infrasound stations ranging from Greenland to Utah, including Canada's Lac Du Bonnett, Manitoba and Elgin Field, Ontario stations, recorded energy from the fireball's explosions. The indicated energy is approximately one third of a kiloton of TNT," Brown said.
Hildebrand estimates that hundreds of meteorites larger than 50 grams could have landed since the rock was large and its entry velocity was lower than average.
The object's speed is calculated to be only roughly 14 km/sec when it entered the atmosphere versus the average of around 20 km/sec.
The projected area of fall lies within Saskatchewan's Manitou Lake Rural Municipality north of Marsden and Neilburg, and just south of the Battle River in an area that is mostly cleared for cultivation.