For the sixth time in history, astronomers have caught a glimpse of an asteroid before it crashes into Earth.
On Nov. 19, 2022, nearly four hours before impact, the Catalina Sky Survey discovered an asteroid called 2022 WJ1 on an inbound trajectory. A network of telescopes and scientists swung into action, calculating precisely when and where the asteroid would hit on the globe.
This is great news. 2022 WJ1 was too small to cause serious damage, but its detection shows that the world’s asteroid-tracking techniques are improving, giving us a better chance of protecting ourselves from falling space rocks—larger ones that could actually cause damage.
Even though space is mostly space, there is also a lot of non-space. In Earth’s vicinity, that non-space is mostly asteroids that orbit the Sun in such a way as to bring them close to Earth’s orbit. We call them near-Earth asteroids, and as of this writing, 30,656 have been catalogued.
Most of these asteroids are actually quite small, and scientists are confident that they’ve found most of them large enough to pose significant danger, studied them, and determined that none of them will get close enough within the next century to be a threat. .
Still, it’s good to stay up to date with what’s buzzing in the space around us and hone our sneaky rock-finding skills while thinking we’re making a grand entrance.
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The detection of 2022 WJ1 was made at 04:53 UTC on November 19, 2022 from the Mount Lemmon Observatory, part of the Catalina network. It continued to track the object, taking four images that allowed astronomers to confirm the detection and report it to the IAU Minor Planet Center at 05:38 UTC.
Those four images were enough to calculate the asteroid’s trajectory across the sky, with multiple impact-monitoring programs finding that the rock had about a 20 percent chance of falling somewhere on the North American continent.
Follow-up observations allowed the scientists to refine their measurements, providing a time and location. Right on time, at 08:27 UTC, 2022 WJ1 was seen hurtling across the sky as a bright green fireball, over the Golden Horseshoe region of southern Ontario, Canada.
The discovery was the first meteor ever predicted to hit a densely populated area, but the rock posed no danger. It measured about one meter (3.3 feet) in diameter when it entered Earth’s atmosphere, making it the smallest asteroid observed before entering the atmosphere to date.
Here it transformed into a flaming bolide and shattered, falling to Earth in smaller pieces that mostly fell into the waters of Lake Ontario. Most of the locatable pieces of the meteorite should be small pieces of debris; scientists hope to recover some to study the asteroid further.
The previous five asteroids detected before impact were 2008 TC3, which was about 4 meters in diameter; 2014 AA, 3 meters in diameter; 2018 LA, also three meters wide; 2019 MO at 6 meters in diameter; and, just earlier this year, 2022 EB5, which was about 2 meters in diameter.
The detection of 2022 WJ1 and the global coordination that followed is a wonderful testament to how much the sensitivity of technology has grown and the magnificence of human cooperation to better understand rogue space rocks.
And, of course, these observations present a rare opportunity to study what happens to asteroids as they enter Earth’s atmosphere.
“This fireball is particularly significant as the parent meteoroid was observed telescopically before it impacted the atmosphere. This makes it a rare opportunity to link telescopic data from an asteroid with its breaking behavior in the atmosphere to gather information about its internal structure,” said the astronomer. and physicist Peter Brown of the University of Western Ontario.
“This extraordinary event will provide clues about composition and strength that, combined with telescopic measurements, will inform our understanding of how small asteroids break apart in the atmosphere, an important knowledge for planetary defense.”
The 2022 WJ1 debris should be dark, with a fresh thin melt crust and a grayer stony interior. Scientists are calling for any suspicious fragments to be reported to the Royal Ontario Museum.