A fireball that exploded over Canada has a completely unexpected origin
Earth is under constant bombardment from space. Dust, pebbles, and bits of rock fall into our atmosphere on a daily basis, sometimes burning spectacularly in a glowing streak across the sky.
These fireballs, or fireballs, are usually larger pieces of an asteroid or comet that broke off their original body and ended up getting caught in Earth’s gravity well.
But scientists have confirmed that one of these fireballs that exploded over Canada last year is not the usual type of meteor. Based on its trajectory across the sky, a team tracked the object all the way through the solar system to its starting point in the Oort cloud — a vast field of icy bodies far beyond Pluto’s orbit.
It’s not very unusual for material to be ejected from the Oort Cloud and sent inward toward the Sun. However, it did burn and explode in a manner said to be made of rock, not a chunk of frozen ammonia, methane, and water that we might expect from an Oort cloud object.
It’s a discovery that suggests our understanding of the Oort Cloud can be used a little Tweaking.
“This discovery supports a completely different model for the formation of the solar system, one that supports the idea that large amounts of rocky material coexist with icy bodies within the Oort Cloud,” says physicist Dennis Vida of the University of Western Ontario in Canada.
“This result is not explained by currently favored solar system formation models. It’s a complete game changer.”
The visitors from the Oort Cloud we’ve identified so far are very icy. They are sometimes known as long-period comets, in orbits around the Sun that take hundreds to tens of millions of years, with random inclinations, and are extremely helical.
They are thought to have been ejected from the Oort Cloud between 2,000 and 100,000 astronomical units from the sun by gravitational effects, and zipped inward on their winding paths.
Because so many of these long-period comets have been identified, scientists have a pretty good idea of what characteristics (and their orbits) they have in common.
This brings us to February 22, 2021, when a fireball shot across the sky about 100 kilometers (62 miles) north of Edmonton, Canada. It has been observed and recorded by multiple instruments, including satellites and two Fireball Global Observatory cameras here on Earth.
For 2.4 seconds, these cameras tracked the meteor for more than 148.5 kilometers, providing scientists with detailed data on the object’s trajectory and its breakup. It is believed that the fireballs heat up and explode when atmospheric gases seep into tiny cracks in the rock, squeezing them from the inside and causing them to explode.
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Veda and his team found that the object was about 10 centimeters (4 inches) in diameter, and weighed about 2 kilograms (4.4 pounds). It was thought to have fallen deeper into the atmosphere than any ice body ever known. In fact, its combustion and disintegration were completely compatible with a rocky fireball.
However, when the researchers used the data to calculate its internal trajectory, the results they obtained were not consistent with the usual local meteor shower, but with a comet’s long-period orbit.
“In 70 years of regular fireball observations, this is some of the most unusual ever recorded. It validates the strategy of the Global Fireball Observatory established five years ago, which expanded its ‘fishing net’ to 5 million square kilometers of sky , and bringing together scientific experts from around the world,” says astronomer Hadrian Devilepuikes of Curtin University in Australia.
“Not only does it allow us to find and study precious meteorites, but it is the only way to have a chance to capture these rare events that are essential to understanding our solar system.”
From this object, the researchers were also able to search the database of the Meteorite Observation and Recovery Project, publish literature for possible Oort Cloud origins, and identify two more meteors: one that fell over Czechia in 1997, called the Karlštejn fireball, in orbit. Similar to Halley’s Comet, and the 1979 MORP 441 meteorite, which also had a comet-like trajectory.
This indicates that, on rare occasions, stony meteorites may wind up on Earth after a long journey from the Oort cloud, thought to be primordial material left over from the formation of the solar system. The next step is to figure out how and why the objects stayed rocky and then ended up here.
“We want to explain how this rocky meteorite ended up so far away because we want to understand its origins. The better we understand the conditions in which the solar system formed, the better we understand what was necessary to ignite life,” says Vida.
“We want to paint a picture, as accurately as possible, of these early moments in the solar system that were so crucial to everything that happened after that.”
Research published in natural astronomy.
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