The fireball that lit up the sky over Alberta and Saskatchewan on Monday morning was a comet fragment burning up in the Earth’s atmosphere, the University of Alberta said Thursday.
The bright flash streaked through the sky just before 6:30 a.m. MT. Several people caught the fireball on dashcam and doorbell cameras.
Images of the trajectory of the fireball were used by U of A researchers, who determined it to be a small piece of comet that burned up in the atmosphere.
“Using two observation sites, we were able to calculate both its trajectory and velocity, which tell us about the origin of the meteor and reveal that it was a piece of a comet,” said Patrick Hill, a post-doctoral fellow in the Department of Earth and Atmospheric Sciences.
“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.”
The U of A said the flash was visible in Alberta and Saskatchewan due to the “unusually high
altitude of the fireball.”
The small pieces of debris were likely only tens of centimetres across in size, the U of A said in a media release.
“So a grapefruit- to basketball-sized object that entered the atmosphere at super-fast speeds,” Hill explained.
It was travelling 220,000 kilometres per hour when it entered the atmosphere. Hill said that’s about 60 kilometres per second.
“Because it was travelling at such speed, that’s why it produced so much friction with the atmosphere — sort of like punching a brick wall. That’s why it was so bright and viewed by so many people,” Hill said.
Its final trajectory was about 120 kilometres north of Edmonton.
“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,” said Chris Herd, curator of the UAlberta Meteorite Collection and professor in the Faculty of Science.
“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.”
Scientists believe Monday’s fireball occurred at an altitude of 46 kilometres. Rocky objects typically burn up between 15 to 20 kilometres above the ground, the U of A said.
“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,” Hill said. “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.”
The team of scientists said while it may be disappointing to some that there are no fragments left behind to find on the ground, it was “an incredible mystery to have solved.”
“We’re thrilled that we caught it on two of our cameras, which could give everyone who saw this amazing fireball a solution,” Herd said.
To calculate the trajectory of the fireball, the team at the U of A used dark-sky images captured at the Hesje Observatory at the Augustana Miquelon Lake Research Station and Lakeland College’s observation station in Vermilion.
Hill noted these types of events are not infrequent. Since the camera network was set up in 2019, the team picked up a fireball event near Camrose in 2019 and another one in 2020.
“What’s generally occurred is because people have more dashcams and doorbell cams, that these events do get picked up by the public in a higher frequency.”