Scientists see incoming asteroid just hours before impact : ScienceAlert
For only the sixth time in recorded history, astronomers have managed to catch a glimpse of one an asteroid before it hit Earth.
On November 19, 2022, nearly four hours before impact, the Catalina Sky Survey detected an asteroid named 2022 WJ1 on its entry path. A network of telescopes and scientists swung into action, calculating precisely when and where the asteroid would hit the globe.
This is great news. 2022 WJ1 was too small to do any 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 — the big ones that could actually do some damage.
Although space is mostly space, it also has a lot of non-space in it. Near Earth, that non-space is mostly asteroids that orbit the Sun in a way that brings them closer to Earth’s orbit. We call them near-Earth asteroids, and at the time of writing, there are 30,656 of them are cataloged.
Most of these asteroids are actually quite small, and scientists are confident that we have found almost all of them that are large enough to pose a significant threat, studied them, and determined that none of them will come close enough in the next century to be a threat.
Still, it’s good to stay abreast of what’s buzzing in the space around us and hone our skills to find hidden rocks that are thinking of making a grand entrance.
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The discovery 2022 WJ1 was made at 04:53 UTC on November 19, 2022 by the Mount Lemmon Observatory, part of the Catalina network. He continued to track the object, taking four images that allowed astronomers to confirm the detection and report it IAU Minor Planet Center at 05:38 UTC.
Those four images were enough to calculate the asteroid’s path across the sky, with multiple impact trackers finding that the rock had about a 20 percent chance of crashing somewhere on the North American continent.
Subsequent observations allowed the scientists to refine their measurements, giving the time and location. Burst on schedule, 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 fall on a densely populated area, but the rock posed no danger. It was about one meter (3.3 feet) in diameter when it entered Earth’s atmosphere, making it the smallest asteroid ever observed before entering the atmosphere.
Here it turned into a flaming bolide and broke apart, falling to Earth as smaller pieces that mostly fell into water of Lake Ontario. Most meteorite pieces that can be located should be small pieces of debris; scientists hope to recover some of them to study the asteroid further.
The previous five asteroids detected before the impact were 2008 TC3, which was about 4 meters in diameter; 2014 AA, 3 meters in diameter; 2018 LA, also three meters in diameter; 2019 MO at 6 meters in diameter; and earlier this year, 2022 EB5, which was about 2 meters in diameter.
The discovery of 2022 WJ1, and the global coordination that followed it, is a wonderful testament to how sensitive technology has grown and the magnificence of human collaboration to better understand space rocks.
And, of course, those observations represent a rare opportunity to study what happens to asteroids when they enter Earth’s atmosphere.
“This fireball is particularly significant because the parent meteoroid was observed telescopically before it hit the atmosphere. This makes it a rare opportunity to correlate the asteroid’s telescopic data with its decay behavior in the atmosphere to gain insight into its internal structure.” said astronomer and physicist Peter Brown from the University of Western Ontario.
“This extraordinary event will provide clues about composition and strength that, when combined with telescope measurements, will inform our understanding of how small asteroids break up in the atmosphere, which is important knowledge for planetary defense.”
Debris from 2022 WJ1 should be dark, with a thin and fresh fusion crust, and a grayer rocky interior. Scientists request that any suspicious fragments be reported Royal Ontario Museum.
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