At first glance, YR4 appeared to be heading our way. And not just in a “wave from a distance” sort of way. Early calculations suggested a 3.1% chance of Earth impact on Dec 22, 2032. That might not sound huge, but in astronomical terms, it’s enough to make scientists swap their tea for something stronger.
Cue global headlines, planetary defence discussions, and schoolchildren asking their teachers if they still had to do their homework.
But just as we were all preparing to duck under the table - metaphorically or otherwise - came an update: more data, better models and lower anxiety. By early 2025, ESA and NASA had refined their calculations. The risk of YR4 hitting Earth had plummeted to a far more relaxing 0.001%.
So… no apocalypse. No Bruce Willis. No giant crater. Earth, it turns out, can relax.
But not so fast. Because while Earth might be safe, it seems the Moon is in the splash zone.
Now Aiming for the Moon?
Yes, you read that right. Revised estimates now suggest that Asteroid 2024 YR4 has a 3.8% chance of hitting the Moon - also on Dec 22, 2032. Which gives us a cosmic plot twist and possibly the best lunar viewing party since the last blood moon.
And should that impact actually happen - and happen on the Moon’s near side - we plan to be watching. Here at BCIS Phuket, our 8-inch telescope is already scheduled for duty that evening. It may not have the punch of the Hubble or James Webb, but it’s more than enough to capture a brief lunar flash from a well-aimed space rock strike (conditions permitting).
What Is YR4, anyway?
Asteroid 2024 YR4 is a small to mid-sized object - anywhere from 40 to 90 metres in diameter, depending on its reflectivity (what scientists call “albedo”) and what it’s made of.
That puts it somewhere between a tennis court and a football pitch in size. Not quite big enough to star in a dinosaur-ending reboot, but definitely not the sort of thing you’d want crashing into your backyard.
It’s currently thought to be a stony asteroid (S-type), though there’s an outside chance it’s metal-rich (M-type) - the sort of object full of nickel and iron. If it were headed for Earth, its impact energy would range from around 4 to 100 megatons, roughly the explosive range between a garden-variety hydrogen bomb and the legendary Tsar Bomba.
But again: it’s not headed for Earth. So, let’s talk about how scientists figured that out.
How do you know where a rock will be in 2032?
Good question! Predicting asteroid paths is a bit like predicting the path of a paper plane tossed in a hurricane, based only on the first few seconds of flight.
Astronomers start by taking images of the asteroid against a background of “fixed” stars. Over days and weeks, they observe its changing position and use Newton’s and Kepler’s laws to map its orbit around the Sun. They calculate six key orbital elements, including how stretched, tilted, and rotated the orbit is. This gives them a rough path - but not a perfect one.
Why? Because measuring anything in space is hard. A tiny error in the asteroid’s position can translate to thousands of kilometres of uncertainty years down the line. That’s why calculations are constantly refined as more data comes in.
And then there’s the Yarkovsky effect - a small force caused by uneven heating from the Sun. As the asteroid rotates, one side warms up and radiates heat into space, giving it a tiny push. Over years, this can subtly alter its course. It’s like trying to predict a marathon runner’s finish line when they’re being nudged ever so slightly by invisible elbows.
To deal with all this, scientists run simulations - thousands of them - using “what if?” scenarios. Over time, the uncertainty shrinks, like tightening the lasso around a wild trajectory.
Enter the Big Guns: JWST and Goldstone
In 2025, NASA announced that the James Webb Space Telescope (JWST) would join the observation campaign. Its mid-infrared instruments are helping to determine the asteroid’s surface temperature, reflectivity, and composition.
Meanwhile, radar facilities like Goldstone in California remain crucial for tracking. Radar bounces signals off the asteroid, allowing scientists to pinpoint its distance and speed far more accurately than with optical methods alone.
Thanks to these tools, we now know: Earth is safe, and the Moon is… well, not out of the question.
What Happens If It Hits the Moon?
Here’s the good news: the Moon gets hit fairly regularly by small asteroids. But YR4 is bigger than the usual suspects.
If YR4 did slam into the Moon, it would release energy equivalent to several megatons of TNT, blasting out a new crater and sending a plume of debris skyward. No danger to Earth, but it could be visible – briefly - as a flash of light.
The size of the resulting crater would depend on the composition and speed of the asteroid but could be in the range of hundreds of metres across. That’s enough to interest both professional scientists and curious observers down here on Earth.
Teaching moments at BCIS
At BCIS, we’ve turned this asteroid drama into an interplanetary learning opportunity. Our astronomy students have been tracking YR4’s orbit, calculating its impact energy, and simulating lunar collisions. They’ve learned how orbital mechanics, telescope observations, and computer modelling all come together in real-life science.
We’ll be hosting a viewing session (weather and Moon permitting) on the night of Dec 22, 2032, complete with our trusty 8” telescope and, no doubt, a few thermoses of cocoa. If the asteroid hits the Moon’s near side, we may be able to catch the resulting flash. If not - well, it’s still a great excuse to stargaze.
Bigger picture: What YR4 taught us
The journey of Asteroid 2024 YR4 is a brilliant example of science in action. What started as a low-key discovery turned into a global exercise in observation, modelling, and refinement. It’s also a reminder that space is far from empty - and that we’re getting better at keeping an eye on it.
Between ground-based telescopes, space observatories, and increasingly accurate software models, the global astronomy community is better equipped than ever to detect and monitor threats from space.
And here in Phuket, we’re doing our part to inspire the next generation of planetary defenders.
So, should you look up?
Absolutely. Especially on Dec 22, 2032. Because while Earth has dodged this particular bullet, the Moon may be about to take one for the team. And if it happens on the visible side, you can bet we’ll be looking - along with students, telescopes, and a few excited teachers - here at BCIS.
In the grand ballet of the solar system, sometimes the spotlight lands on a humble asteroid. And when it does, it’s a wonderful excuse to step outside, look at the sky (assuming you can see it – no small feat in Phuket!), and remember that science isn’t just about textbooks.
Sometimes, it’s about watching a rock fly across 100 million kilometres just to put on a show.
A former telecoms and aerospace engineer, Marco Capriz is Planetarium Director at BCIS Phuket International School, Phuket.