2024 YR4 is currently at the top of NASA’s Sentry Risk Table of asteroid threats
On December 27, 2024, the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Río Hurtado, Chile, spotted a previously undiscovered asteroid. Now named 2024 YR4, this roughly 60-metre wide space rock immediately began setting off alarms, due to what could be an extremely close encounter in late 2032.
According to NASA’s Center for Near-Earth Object Studies (CNEOS), when 2024 YR4 passed by on Dec. 25, 2024, its closest approach was around 828,700 km from Earth, or a little over twice the distance to the Moon. However, on Dec. 22, 2032, it will come much closer.
Based on the observations so far, it could be a very narrow miss, as the asteroid skims the top of the atmosphere.
However, with only a little over 30 days of observations, the uncertainties in this asteroid’s orbit are still fairly large, especially when looking ahead nearly eight years into the future.
On December 22, 2032, asteroid 2024 YR4 could pass by safely, coming no closer to us than 1.7 million kilometres, or over 4 times the distance to the Moon. On the other hand, there is a small, but non-zero chance that it could strike the planet instead!
As of January 30, NASA’s calculations give this space rock a 1.3 per cent chance of impact. That’s roughly a 1 in 77 chance, which is higher than any other near-future impact probability currently listed in the agency’s Sentry Risk Table
Also, given the size of this asteroid, and the potential damage it could cause in an impact, it is the only object on that risk table that currently has a Torino scale rank above zero.
With an estimated diameter of between 40-100 metres, and travelling at a speed of 13.5 kilometres per second, 2024 YR4 could cause significant local damage if it were to hit Earth. These types of asteroids are often called ‘city killers’.
The Chelyabinsk impact, on February 15, 2013, released the equivalent energy of about 440,000 tonnes of TNT. The air-burst explosion from that asteroid shattered windows across the area, caused minor damage to some buildings, and resulted in around 1,500 injuries. An impact by 2024 YR4 would be around 15-20 times more powerful.
As such, it is currently rated as a 3 on the Torino scale.
Although the uncertainties are high right now, working from the current trajectory of the asteroid, German amateur astronomer Daniel Bamberger came up with a map showing the potential impact zone for 2024 YR4.
Taking into account the rotation of the Earth during the window of impact, Bamberger plotted a narrow corridor that stretches from the Pacific Ocean south of Mexico, through northern South America and the equatorial Atlantic Ocean, across central Africa, Yemen and Oman, and through central India to Bangladesh.
It should be noted that a 1.3 per cent chance of impact is also a 98.7 per cent chance of a miss. Thus, it is far more likely that 2024 YR4 will miss us than hit us. So, there is nothing to worry about at this time.
Plus, other asteroids have also ranked reasonably high on the Torino scale, but when more observations came in, astronomers were able to completely rule out any threat from them.
99942 Apophis is an excellent example of this. After its discovery in 2004, Apophis made it all the way up to rank 4 on the Torino scale. As astronomers carefully watched it, though, and gathered more information on its exact path around the Sun, they were able to refine their calculations of its orbit and completely rule it out as a threat. The asteroid was even removed from NASA’s Sentry Risk Table as of February 21, 2021.
In all likelihood, the same thing will happen with 2024 YR4. It may have a high risk now, but further observations will give us a better idea of what its orbit looks like, and we will probably see that risk go down, if not entirely disappear.
