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Betteridge’s law of headlines states that “Any headline that ends in a question mark can be answered by the word no.” That is likely the case here, but not yet entirely confirmed.
In December 2024 astronomers discovered a new asteroid, now attractively named 2024 YR4.
Upon calculating its future orbit, determined that there was about a 1.5% chance it would collide with Earth in December 2032.
Estimated to be between 40-90 metres across, an impact on Earth would cause major damage to a city sized area, or large tsunamis if impacting over ocean.
Astronomers are working to obtain more data to precisely define the asteroid’s orbit as soon as possible.
For reference, in 2013, an 18 metre asteroid exploded over Chelyabinsk in Russia and caused significant structural damage to the city, but no fatalities.
DASH CAM FOOTAGE: Chelyabinsk Meteor, February 15th 2013
Getting a precise prediction of an asteroids’ location years in advance is quite difficult, requiring many observations over an extended period of time.
Even though asteroid 2024 YR4 was ‘discovered’ in December 2024, astronomers have since realised it had already been observed in previous historical sky surveys.
Using this older data to more precisely refine the asteroid’s location, by February 18 2025, astronomers had calculated that the chance of collision had gone up to 2.8%.
This has given 2024 YR4 the highest probability of impact of any asteroid we currently know about.
Rather than alarm, most astronomers are unconcerned. This is because of the unintuitive nature of impact probabilities as orbits are refined.
Without knowing the exact orbit of an object (essentially impossible) astronomers can instead only give regions of space where an asteroid might be located in the future.
If that region includes Earth, then we can calculate the probability of impact.
As astronomers gather more data, they can more precisely calculate the orbit — and the region of space where the asteroid might be located becomes smaller.
However, if that region still includes the Earth, then our planet now covers a larger fraction of that region, and so the probability of impact increases.
This is an important distinction.
The probability increases because the region of space where the asteroid might be located is smaller, not because we are definitely more certain that it will hit our planet.
What usually happens, is the orbit will soon be so precisely calculated that the region it could be located in will be very small, and no longer overlap with Earth.
At this time, the probability of impact drops abruptly to 0%.
Astronomers expect this same outcome for 2024 YR4. All we need is more observations.
Unfortunately, the asteroid is currently heading away from Earth at a particularly difficult angle to study.
Astronomers are hoping to use the James Webb Space Telescope to observe it in early March.
They hope this will provide enough high-quality data that the orbit can be calculated more precisely. If not, we won’t get another good look at it until 2028.
This does raise the question: is there anything we can do if the asteroid is definitely going to hit Earth?
The answer is a resounding ‘Yes!’ (and doesn’t even need Bruce Willis).
In September 2022, NASA’s DART mission deliberately slammed into the asteroid Dimorphous and significantly altered the orbit of this asteroid.
NASA’s DART Mission Confirms Crashing Spacecraft into Asteroids Can Deflect Them
At 177m across, Dimorphous is considerably larger than 2024 YR4. In principle this kinetic impactor approach could slow the asteroid down enough for it to miss Earth.
The theory has been demonstrated. Whether we will need to put it into practice, time will tell.
If you would like to hear even more about this month’s night sky, listen to Particle’s Please Look Up. Hosts Leon and Beth delve deeper into space, share the latest space news, and discuss fascinating astronomical facts. Available on all major podcast platforms.
