UNSW Canberra is playing an important role in monitoring an asteroid that could be on a collision course with the Earth.
It may sound like the plot of a Hollywood thriller, but an asteroid is potentially on a collision course with Earth in December 2032, and if it hits there could be catastrophic consequences.
The asteroid named 2024 YR4, which could be anywhere from 40-90 metres in diameter, was discovered on 27 December 2024 and has since sparked a frenzy in the international astronomy community to determine its exact trajectory.
However, Professor Ed Kruzins from UNSW Canberra Space, cautions against hysteria about the possibility of a collision and explains what role UNSW Canberra will play in the international effort to track the asteroid.
Currently, there is a 1.5% likelihood that this asteroid will hit the Earth – but it’s best to think about it as 98.5% likely to miss based on current data. Globally we only have a tiny percentage of the asteroid’s orbit measured and the uncertainly of that figure is still very large. Only days ago, the likelihood reached 3.1%, but this lowered with further observation.
On the asteroid “Torino” risk scale it is classified as a 3, meaning it warrants attention by astronomers to clarify its orbit. The last time we saw anything like this was in 2004 for Apophis 99942, which had a 2.7% likelihood of impact and ranked at 4 on the Torino scale. By 2006, it was determined Apophis would not hit Earth and it was reassigned to 0 on the Torino scale.
It is likely that with more observation and analysis 2024 YR4’s likelihood of impact will continue to lower, but we won’t know that definitively for several years.
The asteroid is now moving quickly away from Earth and growing very dim. It’s on an elliptical orbit with its furthest point 360 million kilometres away from Earth, or about half the distance to Jupiter. It will require very large telescopes to observe it in February and March. After that astronomers will need to use the Hubble Space Telescope or James Web Space Telescope (JWST) to see it. A proposal has been submitted by the International Asteroid Warning Network (IAWN) to use the JWST.
However, the asteroid will return in 2028 and it will be possible to have another look and build more orbit precision then. At that stage we will likely be able to say with certainty whether it will hit the Earth. Astronomers will also look to determine exactly what the asteroid is made of. It is most likely that it is a mass of rocky substances that would explode in the atmosphere as an airburst, rather than metallic asteroids that are significantly denser and more likely to make landfall and cause craters.
UNSW Canberra is a founding member of the Southern Hemisphere Asteroid Research Consortium (SHARC), along with CSIRO, NASA-JPL, University of Western Australia, University of Tasmania and Curtin University. We monitor about 10 asteroids per year which are Earth orbit crossing and have the potential for risk.
UNSW Canberra Space participates by analysing radar reflections transmitted from CDSCC Tidbinbilla and received by CSIRO managed radio telescopes. We also use our Falcon and Viper telescopes to take optical measurements to compare with radar reflections and improve orbit measurements and asteroid rotation rates. These help with risk calculations and tell us about the type of asteroid (sandy, rocky or metallic). We share our findings with the IAWN, a United Nations endorsed body, and the Australian Government to ensure decision-making agencies have the best information possible.
With the basic information we have so far, a potential impact track might run from India to north Africa, but if we can acquire further information in 2028 it will be possible to make a more precise estimate if it was confirmed to be an impactor.
An asteroid the size of 2024 YR4 could deliver up to the equivalent of several tens of megatons of TNT. If impact was over a city or populated area it could be catastrophic and would require the evacuation of the entire area.
Yes! In September 2022, the NASA DART spacecraft purposely collided with space rock Dimorphis, at a speed of over 22,000 kilometres per hour, to see if it could deflect it. The mission was successful and proved that even a small bump, done early enough, can make a big change in the asteroid’s eventual position over a longer period. Dimorphis at 144 metres in diameter is likely to be significantly larger than 2024 YR4.
Large numbers of small, centimetre-sized asteroids impact the earth annually. These are of no consequence. About once per year a small, metre-sized asteroid will make impact, these typically break up as airbursts but can rattle windows. An asteroid 10 metres and above will hit every 10 years or so. These also usually result in airbursts that can break windows and flatten small areas of forests. A 100 metre-plus sized asteroid will hit the Earth approximately every 5000 years. These can form craters or cause significant damage but only on a regional scale.
Note: The likelihood of impact was correct as at time of publication. This figure is likely to change over time.
