Planetary defence experts are keeping an eye on a newly-discovered asteroid that has a chance – albeit slim – of impacting Earth in 2032.
The European Space Agency's Planetary Defence Office says asteroid 2024 YR4 will skim by our planet on 22 December 2032, and has a 99% chance of passing safely by.
But, scientists say, a possible impact cannot yet be entirely ruled out, and it's too early to say where exactly on Earth any impact would occur.
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What we know about asteroid 2024 YR4
Asteroid 2024 YR4 is estimated to be between 40m and 100m, but likely larger than 50m wide.
It was discovered on 27 December 2024 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Río Hurtado, Chile.
It's what's known as a 'near Earth asteroid', and just after its discovery, automated warning systems alerted scientists that it had a small chance of hitting Earth on 22 December 2032.
The European Space Agency says "an asteroid this size impacts Earth on average every few thousand years and could cause severe damage to a local region."
It's currently at the top of the agency's asteroid risk list.
How likely is an Earth collision?
Since early 2025, astronomers have observing asteroid 2024 YR4 using telescopes around the world.
New data is helping improve predictions of the asteroid's size and trajectory.
On 29 January 2025, ESA said there was a 1.2% chance the asteroid would hit Earth.
That makes it 'Level 3' on the Torino Impact Hazard Scale.
This means it's considered "a close encounter that warrants attention from astronomers and the public".
However, the rather encouraging caveat is that "an asteroid’s impact probability often rises at first before quickly dropping to zero after additional observations."
What next for 2024 YR4?
Two UN-endorsed asteroid reaction groups are monitoring the asteroid: the International Asteroid Warning Network (IAWN) (of which ESA is a member) and the Space Mission Planning Advisory Group (SMPAG).
If a collision was deemed likely, IAWN would begin developing a strategy to determine what an impact would look like and how to minimise damage.
Asteroid 2024 YR4 travels around the Sun in an eccentric orbit, meaning its orbit isn't perfectly circular, but elongated instead.
It's currently moving away from Earth in a straight line, which, say scientists, makes it tricky to determine what its orbit looks like.
The asteroid will begin to fade from view throughout 2025, but before it does so, astronomers will use Earth's most powerful telescopes, like the European Southern Observatory’s Very Large Telescope in Chile, to find out as much as they can.
2024 YR4 could even disappear from view before astronomers get enough data to rule out a chance of impact with Earth in 2032.
It won't become observable again until it begins approaching Earth in 2028.
The Space Mission Planning Advisory Group says that if the asteroid’s impact probability remains above 1%, it could begin to consider "a spacecraft-based response to the potential hazard".
The 2022 DART mission showed an asteroid deflection was possible and, in the slim chance 2024 YR4 does become a threat to Earth, this could prove a true test of the science.
www.esa.int/Space_Safety/Planetary_Defence
What do you think? Should we be concerned about asteroid 2024 YR4, or will this be a near-miss? Let us know by emailing contactus@skyatnightmagazine.com
