Dangerous Asteroid 2024 YR4: Are We Safe?
For the last two months, the news of asteroid 2024 YR4 predicted to hit Earth has been blasting the Internet. It has become one of the most dangerous near-Earth objects in the last 20 years. Since the asteroid’s discovery, the risk of a collision has been rapidly increasing, reaching an alarming 3.1% at its maximum. However, recently, the unprecedentedly high odds have come crashing down. Let's see what is known about this asteroid so far, why it made us so nervous, and how high the probability of a collision currently is. By the way, with the help of the Sky Tonight app, you can easily find out where it is flying now.
Contents
- What is asteroid 2024 YR4?
- Asteroid 2024 YR4 hitting Earth: odds & possible effects
- Asteroid 2024 YR4: what’s next?
- Asteroid 2024 YR4: to sum up
What is asteroid 2024 YR4?
Asteroid 2024 YR4 was discovered by the ATLAS telescope on December 27, 2024 – right after its close approach to Earth: two days earlier, the asteroid passed at a distance of 830,000 kilometers (about 2.15 times the distance to the Moon) from our planet. It completes an orbit around the Sun in about 4 years.
First calculations revealed that asteroid 2024 YR4 had an unusually high chance of impacting Earth during its approach on December 22, 2032. This alarming possibility quickly drew the attention of the scientific community.
How big is asteroid 2024 YR4?
2024 YR4 is estimated to be 44-100 meters in diameter, which is similar in size to a Boeing 737 aircraft (on the smaller end) and Big Ben or Statue of Liberty (on the larger end). It can also be compared with the Tunguska impactor – an estimated 50-meter asteroid that flattened 2,000 square kilometers of Siberian forest back in 1908.
How dangerous is asteroid 2024 YR4?
Upon discovery, asteroid 2024 YR4 scored 3 out of 10 points on the Torino scale, which means it was considered to have a 1% (or higher) chance of hitting the Earth in less than 10 years and causing local damage. This was a new record since Apophis, which had 4 points in 2004. The risk levels triggered the International Asteroid Warning Network (IAWN) to issue a Potential Asteroid Impact Notification to alert the public and space agencies about an asteroid’s potential to collide with Earth.
Additional tracking of its orbital path has significantly reduced the probability of an Earth impact to below the 1-in-1,000 threshold. This is the criterion for downgrading objects smaller than 100 meters to Torino Scale Level 0, indicating “No Hazard”. This means that, based on current calculations, 2024 YR4 poses no threat to Earth and requires no further concern for planetary defense.
Dangerous, but still not “potentially hazardous”
You might find it surprising that asteroid 2024 YR4, which remained on the list of the most dangerous asteroids for quite some time, was never classified as a “potentially hazardous asteroid”. How can that be? Well, it’s simply too small to qualify!
A “potentially hazardous asteroid” (PHA) is an official term used to describe an asteroid that:
- Has an absolute magnitude of 22.0 or less (which means its diameter is over 100-150 meters, depending on its reflectivity),
- And comes within 0.05 astronomical units of Earth (that’s about 19.5 times the distance to the Moon).
Asteroid 2024 YR4 has an absolute magnitude of 23.95, which corresponds to a size of less than 100 meters. This is considered too small to be a major concern. (Interestingly, an asteroid of this size could easily wipe out an entire city – but apparently, scientists have peculiar ideas of “potentially hazardous.”)
Asteroid 2024 YR4 hitting Earth: odds & possible effects
While there is a 99.99% chance that asteroid 2024 YR4 will safely miss Earth in 2032, scientists always take the remaining uncertainty into account. What if asteroid 2024 YR4 did collide with our planet? Let’s explore the potential consequences of an impact from an asteroid of this size.
Where could asteroid 2024 YR4 hit?
According to the statement issued by the International Asteroid Warning Network (IAWN), the potential impact risk corridor stretches across the eastern Pacific Ocean, northern South America, the Atlantic Ocean, Africa, the Arabian Sea, and South Asia. This means that the impact could affect densely populated regions such as India, Pakistan, Bangladesh, Nigeria, Sudan, Ethiopia, Ecuador, Colombia, and Venezuela.
What happens if asteroid 2024 YR4 hits Earth?
The outcome of the impact can vary depending on three things:
- Size;
- Composition;
- Impact location.
Size: how big could the blast be?
- If we assume that its actual diameter is about 50 meters (which is close to the lowest estimates), the impact energy would be about 8 megatons of TNT. The resulting blast could be 16 times stronger than the Chelyabinsk event, when the shockwave blew out windows in 7,000 buildings, and 1,500 people were injured.
- If we take as true the largest estimates, namely a diameter of 100 meters, the impact energy would be 50 megatons of TNT, which is roughly equivalent to a nuclear bomb explosion (one Tsar Bomba or 3,333 Little Boys). Check our infographics about dangerous asteroids to further explore the connection between an asteroid’s size and the possible impact effects.
Composition: will it explode or make a crater?
- If asteroid 2024 YR4 is made of rock, it might blow up in the sky, causing a big explosion and a fireball that hits the ground.
- If it’s composed of iron, it would pass through the atmosphere with ease and hit the ground, creating a crater up to 20 times its size. For example, if the asteroid is about 50 meters in size, it could form a crater a kilometer wide; if it’s closer to 100 meters, the crater would be roughly twice as large.
Impact zones: what’s at risk?
- One of the most likely impact scenarios involves the asteroid falling into the ocean (Pacific, Atlantic, or Arabian Sea). A shallow-water impact could trigger a tsunami tens of meters high, severely affecting coastal cities. A deep-ocean impact would generate smaller waves but could still disrupt global shipping.
- If the impact affects an urban area (a major city such as Mumbai, Lagos, or Bogota), the shockwave would likely demolish buildings within a 10-30 kilometer radius, resulting in hundreds of thousands to millions of casualties in densely populated regions.
- If it lands far from the big cities, the environmental impact would still be significant. The explosion could trigger forest fires, and shockwaves would be felt hundreds of kilometers away.
As you can see, asteroid 2024 YR4 wouldn’t pose a mass-extinction-level threat in either case. However, local damage would be devastating.
There’s also a 1.7% chance that the asteroid would hit the Moon. In this case, Earth would be relatively safe, as any material ejected from the collision would likely burn up in our atmosphere. The Moon, however, would be left with a crater up to 2 kilometers across – a mere pothole compared to the Moon's largest crater, the South Pole-Aitken basin, which spans over 2,400 km in diameter. Such a collision could release more energy than 340 Hiroshima bombs and would likely be visible from Earth.
What are the chances of asteroid 2024 YR4 hitting Earth?
For the first two months after its discovery, the risk of asteroid 2024 YR4 impacting Earth kept increasing, rising from 0.99% to a striking 3%. That doesn’t seem like much, but usually, risks are much smaller than that: most near-Earth asteroids have impact probabilities in the range of 0.00001% or less. In fact, 2024 YR4 briefly held the highest recorded impact probability for an asteroid of its size or larger.
Fortunately, updated calculations have significantly reduced the risk. The maximum probability of a collision now stands at 0.0016%, while the cumulative probability is 0.0039% – a dramatic decrease from earlier estimates.
But what do these numbers mean? Maximum probability refers to the highest chance of impact on a single predicted approach, meaning that on a specific date, the risk does not exceed 0.0016%. Meanwhile, cumulative probability accounts for all possible future encounters, summing up their individual risks. In other words, even when considering every close pass 2024 YR4 might make, the overall chance of impact remains no higher than 0.0039%.
Since observations take time, it's too early for definitive conclusions. Perhaps later, asteroid 2024 YR4 will turn out to be perfectly safe for Earth, as has been the case with many asteroids heading toward Earth before – we discuss them in more detail in our article on dangerous asteroids. By the way, there, we calculate the chances of dying as a result of an asteroid impact and analyze ways to protect the Earth from asteroids – a very relevant and uplifting read.
How could we defend against asteroid 2024 YR4?
Although the risk of asteroid 2024 YR4 colliding with Earth is low, it's always worth considering how we might prevent an asteroid impact in the future. From kinetic impactors to nuclear devices, various methods have been proposed – but how realistic are they? Let’s explore whether we could deflect or destroy 2024 YR4 if it became a real threat.
Could we deflect 2024 YR4?
Efforts to change the path of dangerous asteroids have been going on for years. In 2022, NASA successfully tested a planetary defense system called the Double Asteroid Redirection Test (DART), which changed the orbit of the asteroid Dimorphos. While a similar mission could be launched to redirect 2024 YR4, experts warn that we don’t know what the asteroid is made of. If it’s made of loose rubble, a collision might break it into many smaller pieces. Instead of one 40–50 meter rock, we could end up with many uncontrollable fragments, making it harder to stop a disaster.
Could we nuke 2024 YR4?
One idea often seen in movies is using nuclear weapons to change the asteroid’s path, but experts say this is both impractical and risky. Nuclear weapons have never been tested in space for planetary defense, so we don’t know how effective they would be. If the mission failed and the device exploded in Earth’s atmosphere, it could create even more serious threats. Unlike a deflection mission, a failed nuclear mission could lead to global diplomatic issues and unintended consequences.
Asteroid 2024 YR4: what’s next?
Although 2024 YR4 does not pose a danger to Earth, its upcoming close approaches in 2028 and 2032 will still be of great interest to scientists. On December 17, 2028, the asteroid will come within 8 million kilometers of our planet – relatively close on a cosmic scale. Even more notably, on December 22, 2032, it will pass at a distance of just 270,000 kilometers, bringing it closer than the Moon, which orbits Earth at an average distance of 384,400 kilometers. While there’s no need for concern, astronomers are eager to take advantage of this opportunity to closely observe 2024 YR4. These flybys will allow researchers to study the asteroid’s physical characteristics, motion, and composition, contributing to our understanding of near-Earth objects.
Asteroid 2024 YR4: to sum up
Once a top concern, asteroid 2024 YR4 is now just another passing rock – tracking and calculations have confirmed that the chance of collision is low. While it no longer poses a threat, its story highlights the importance of asteroid tracking and planetary defense. Each new discovery refines our understanding of near-Earth objects, ensuring that if a real threat ever emerges, we’ll be ready.
By the way, more than 2,000 hazardous asteroids have been detected so far. Want to learn more about how we monitor them? Check out our article on dangerous asteroids to explore past threats, impact risks, and the science behind keeping Earth safe.
