We saw the sixth asteroid impact coming

Space safety

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On November 19, asteroid 2022 WJ1 became one of many small asteroids to strike Earth, but only the sixth we’ve seen it coming. For the second time this year, humanity expected an asteroid collision. The rock about 1 meter high has caused no damage and is burning in the sky above Toronto as an amazing fireball. Advance detection, warning and monitoring of this asteroid demonstrate our rapidly increasing ability to warn of asteroid impacts, no matter how small.

in depth

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Time-lapse image of 2022 WJ1 taken by astronomer Robert Werick in Ontario, Canada

The initial detection of asteroid 2022 WJ1 came from the Catalina Sky Survey – one of the main projects dedicated to detecting and tracking near-Earth objects (NEOs) – at 04:53 UTC (05:53 CET) on November 19, 2022, just under four hours before impact.

The new asteroid was first imaged by the 1.5-meter Catalina Lemon telescope, and once four observations had been made, it was reported to the Minor Planet Center (MPC), 38 minutes after the initial detection, at 05:31 UTC.

These four observations were enough to map the asteroid’s trajectory in the sky, and within a few minutes of this “astronomical measurement” being published, the European Space Agency’s internal monitoring program reported that the object had about a 20% chance of hitting Earth, possibly colliding somewhere in the North America in the next two to three hours. A few minutes later, other impact monitoring programs also sent alerts detailing a similar scenario.

First collision pass computed by the European Space Agency’s Meerkat instrument at 05:36 UTC, from early observations of asteroid 2022 WJ1

After notifications of the potential impact, observers at Catalina and elsewhere across the United States obtained follow-up observations of the new asteroid. Less than 30 minutes after the initial trigger, the impact was confirmed with excellent accuracy: the small asteroid, likely less than a meter in diameter, was to strike somewhere between Lake Erie and Lake Ontario, near the US-Canada border, around 08:00. 27 UTC (09:27 CET).

Exactly at the expected time, an asteroid about 1 meter high hit the atmosphere and became a brilliant fireball over the predicted location. Learn more about this event at the ESA’s Near Earth Object Coordination Center (NEOCC) web portal.

Asteroid impact: what are the risks?

Given how the solar system was formed, small bodies make up the majority in terms of their total population. It is estimated that there are 40-50 million small asteroids and “only” 1000 of the largest giant “planet killers”. The rest falls somewhere in between.

Illustration: Explanation of the asteroid hazard

We currently know of more than 1.1 million asteroids, although there are many more out there. Of these discoverers, about 30,600 are traveling in orbit that brings them close to planet Earth. These are the Near-Earth Asteroids (NEAs).

The reassuring news is that almost all of the giant asteroids – more than 95% – have been found and nothing to worry about for the next 100 years. Astronomers tirelessly search for the last one.

Trail of the Chelyabinsk asteroid

Small asteroids the size of a meter hit the Earth every two weeks. They add to our understanding of asteroid and fireball groups and their composition, but they aren’t a huge priority when it comes to planetary defense because they don’t really pose a danger.

The things we’re most worried about are those “golden asteroids” that are big enough to cause damage if they collide, and there are enough of them out there that we know, at some point, they will. The infamous Chelyabinsk impact of February 2013 and the Tunguska impact of June 1908 fall into this category, and when it comes to discovering these asteroids, there is still a lot of work to be done.

Hera in Didymus

That’s why ESA’s Office of Planetary Defense is planning new telescopes on Earth and missions in space to improve our asteroid detection capabilities, sending the Hera mission to the Dimorphos asteroid hit by NASA’s DART mission to test asteroid deflection, and also working with the international community to prepare for a scenario in which it takes place. Discover a larger asteroid on a collision course.

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