The world’s space agencies are keeping close watch on an asteroid heading our way, because there’s currently a 1 in 83 chance it will hit our planet in the next eight years.
Asteroid 2024 YR4, as it’s been designated, was flagged by the International Asteroid Warning Network (IAWN) for its potential to impact Earth on 22 December 2032.
“This is one of the highest probabilities of an impact from a significantly sized rock ever,” Catalina Sky Survey engineer David Rankin wrote on Bluesky. “Most likely outcome is still a near miss.”
But the asteroid’s size, and the non-zero chance of it hitting Earth within the next 50 years, is enough to prick the ears of two UN-endorsed asteroid reaction groups.
The IAWN will coordinate international organisations to continue monitoring 2024 YR4, and if necessary, develop a strategy for world governments in preparing for the hit and its consequences.
“The first step in the planetary defence response is to trigger further observations,” astronomer Colin Snodgrass from the University of Edinburgh told Ian Sample at The Guardian.
“If these observations don’t rule out an impact, the next steps will be more detailed characterisation measurements using telescopes, and discussion of what space agencies could do in terms of more detailed reconnaissance and eventually mitigation missions.”
Asteroid 2024 YR4 was first sighted on 27 December 2024 by a telescope in Río Hurtado, Chile. This telescope is part of a network that automatically scans the sky looking for early warning signs of asteroid impacts, aptly named the Asteroid Terrestrial-impact Last Alert System (ATLAS).
2/ The clip below shows ESO’s VLT recent observations of asteroid 2024 YR4, which have helped refine its trajectory. It is estimated to be 40-100 m wide, but more data and analysis are needed to confirm the size, and to refine its trajectory.
ESO/O. Hainaut et al.
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— ESO (@eso.org) 30 January 2025 at 04:01
The asteroid’s diameter, while not enough to wreak immediate global havoc, is definitely enough to cause severe damage to whatever region it hits, potentially spanning as far as 50 kilometers from the impact site.
It’s too soon to know where on Earth that would be, if it happens at all, but the IAWN’s Potential Impact Notification lists the eastern Pacific, northern South America, Africa, and South Asia as potential sites.
A range of international agencies, including the European Space Agency, NASA’s Center for Near-Earth Object Studies, and the Italian Near Earth Objects Dynamic Site, agree that the chance of the asteroid hitting Earth is just over 1 percent.
Nonetheless, it’s been rated Level 3 on the Torino Scale, which means we should pay it some attention, though it’s likely to be reassigned to Level 0 with further telescopic observations.
Only one asteroid in history has ever received a higher Torino scale rating. Near-Earth asteroid 99942 Apophis set the record at level 4 in December 2024.
Thankfully, recent calculations have ruled out the possibility of Apophis colliding with Earth for the foreseeable future.
The odds of near-Earth asteroids colliding with our planet tend to rise in the early days of sighting them. At first we have just a few points of reference from which to calculate the asteroid’s orbit. Because its path is less certain, at this stage the ‘risk corridor’ is very wide, increasing its potential overlap with Earth.
As we receive more data by watching the asteroid’s movements, we can be more certain of its predicted path, so it becomes narrower.
Earth is usually still in the line of fire at this point. Because the path is more certain, the risk of the asteroid hitting Earth always appears to increase at this point.
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But ultimately, the more certain that path becomes, the narrower it gets, which in most cases reveals an asteroid trajectory that is both very certain, and, thankfully, not on course for Earth.
It’s particularly difficult to accurately predict asteroid 2024 YR4’s path at the moment, because it has an elongated (eccentric) orbit around the Sun, and it’s currently moving in almost a straight line away from Earth. So its uncertainty region is massive.
Meanwhile, the Space Mission Planning Advisory Group will discuss the asteroid at a routine meeting in Vienna in the coming week.
If the asteroid impact risk remains above 1 percent, the group will provide advice to the United Nations and consider our options, which will likely involve diverting or destroying the asteroid via spacecraft, like NASA’s Dart mission.
“This asteroid is of the scale that a mission like Dart could be effective, if required, so we have the technology and it has been tested,” Snodgrass said.
