What caused Alta.’s fireball Monday? U of A scientists solve ‘incredible mystery’

EDMONTON — We’re learning more about the fireball so many Albertans saw streak across the dark sky early Monday morning.

Thanks to the University of Alberta’s fireball monitoring network, scientists are now able to say that bright streak was a small piece of a comet that burned up in Earth’s atmosphere.

According to the U of A’s Faculty of Science, Western Canada’s most advanced fireball monitoring network also helped in determining the trajectory and velocity of the meteor, as well as its origin.

“This chunk was largely made of dust and ice, burning up immediately without leaving anything to find on the ground, but instead giving us a spectacular flash,” Patrick Hill, from U of A’s Department of Earth and Atmospheric Sciences, said in a news release.

That flash was seen throughout Alberta and parts of Saskatchewan at 6:23 a.m. Monday, due to the unusually high altitude of the fireball.

Normally a rocky object will burn up between 15 to 20 kilometres above the ground after entering the atmosphere, but U of A scientists say Monday’s fireball happened at an altitude of 46 kilometres.

That’s how so many people, and cameras, were able to see the natural light show.  

“All meteoroids – objects that become meteors once they enter Earth’s atmosphere – enter at the same altitude and then start to burn up with friction,” explained Hill. “Sturdier, rocky meteoroids can sometimes survive to make it to the ground, but because this was going so fast and was made of weaker material, it flashed out much higher in the atmosphere and was visible from much farther away.”

U of A scientists believe the final point on its trajectory was 120 kilometres north of Edmonton.

They say the small piece of comet debris, likely only tens of centimteres across in size, travelled at a rate of more than 220,000 kilometres an hour before entering Earth’s atmosphere.

“This incredible speed and the orbit of the fireball tell us that the object came at us from way out at the edge of the solar system, telling us it was a comet, rather than a relatively slower rock coming from the asteroid belt,” Chris Herd, curator of the UAlberta Meteorite Collection and professor in the Faculty of Science, said in a news release.

“Comets are made up of dust and ice and are weaker than rocky objects, and hitting our atmosphere would have been like hitting a brick wall for something travelling at this speed,” Herd added.

The team from the U of A used dark-sky images from the Hesje Observatory at the Augustana Miquelon Lake Research Station and at Lakeland College’s observation station in Vermilion to make their calculations.

Unlike the Buzzard Coulee meteorite from November 2008, which produced a similar fireball effect, there most likely won’t be anything remaining to find on the ground. 

Still, Herd and Hill are pleased with their learnings.

“This is an incredible mystery to have solved,” said Herd. “We’re thrilled that we caught it on two of our cameras, which could give everyone who saw this amazing fireball a solution.”

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