Fireball was fragment of comet, scientist says
A fireball seen over Alberta Monday morning has been determined to be a fragment of a comet, University of Alberta scientists say.
Dark-sky images that captured the fireball and its trajectory from the Hesje Observatory at the Augustana Miquelon Lake Research Station and at Lakeland College's observation station in Vermilion revealed the fireball that lit up skies around 6:23 a.m. was a small piece of a comet that burned up in the atmosphere.
“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,” said Patrick Hill, post-doctoral fellow in the department of earth and atmospheric sciences at the U of A in a news release Thursday.
The comet fragment streaked through the sky to about 120 kilometres north of Edmonton.
Usually, rocky objects will burn up between 15 to 20 kilometres above ground.
But this fireball occurred at an altitude of 46 kilometres, allowing it to be visible by people and picked up on cameras throughout Alberta and parts of Saskatchewan.
The fragment was only tens of centimetres across in size and was travelling at more than 220,000 km/h when it entered the 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,” said Chris Herd, curator of the Ualberta Meteorite Collection and professor in the Faculty of Science in the 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.”
The Buzzard Coulee meteorite from November 2008 was seen by people in Alberta, Saskatchewan, Manitoba and even North Dakota, providing a flash five times brighter than a full moon.
According to Herd, Monday's fireball was travelling almost three times faster, causing it to burn up, whereas the Buzzard Coulee meteorite was made of rocky material and survived to the ground.
However, that also means there won't be any remnants of Monday's fireball to recover on the ground.
“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.”