Asteroid 2024 YR4 has undoubtedly been the star of space science in recent months. Since its discovery in late 2024, its possible trajectory toward Earth and, now, its orbit toward the Moon, has raised global alarm and mobilized observatories, agencies, and experts around the world. But what do we really know about its size, behavior, risks, and the international responses it has provoked?
In the following lines we will take a comprehensive look at all the relevant aspects of asteroid YR4: From the technical details of its discovery, variations in its trajectory estimates, the role of the UN and space agencies, to the latest scenarios using ground-based observatories and the James Webb Space Telescope. If you want to stay up to date and understand the risks, certainties, and scientific opportunities this cosmic visitor offers, here's everything you need to know.
Tracing History: When and How 2024 YR4 Was Discovered
El December 27th 2024 It will be marked in the astronomy calendar as the date on which asteroid 2024 YR4 was first detected. This important discovery was made by the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile, just two days after the object passed about 828.800 kilometers from EarthIts discovery not only alerted the specialized community, but also launched an intense international monitoring and analysis campaign, coordinated by NASA, the European Space Agency (ESA), and the International Asteroid Warning Network (IAWN).
In the following days, the asteroid was included in the impact risk lists and an unprecedented data collection began. According to the first observations, it was an object between 40 and 90 meters in diameter, classified as an Apollo-type NEO (near-Earth object), meaning it has an orbit that crosses that of our planet.
Dimensions, rotation, and shape: What is asteroid YR4 like?
The size of the YR4 has been a source of speculation and successive revisions. Initially it was estimated between 40 and 90 meters, although the most recent measurements with the james webb space telescope and ground-based observatories such as Gemini South have refined the figure towards 60 meters in diameterThis variation is due, above all, to the difficulty in knowing how much light its surface reflects, since a larger but darker object may look similar in brightness to a smaller, more reflective one.
One of the most curious discoveries about the YR4 is its unusual shape, similar to a hockey puck, when it is common to find more irregular geometries in asteroids, like potatoes or spinning tops. In addition, Its rotation period is very fast: it completes one revolution every 19-20 minutes.By analyzing its brightness and light curves obtained from multiple telescopes, scientists have determined that it is an S-type asteroid, meaning it is rich in silicates and has a predominantly rocky composition.
Orbit, approaches and the famous date of 2032
2024 YR4 follows a highly elliptical orbit around the Sun, which periodically brings it across the Earth's orbit.The asteroid reached perihelion on November 22, 2024, and made a close pass by Earth on December 25, just two days before its discovery. On that occasion, it was within less than 830.000 kilometers of our planet and about 488.000 kilometers from the Moon. Its next significant approach will be December 17th 2028, when it will be approximately 7,9 million kilometers away, a distance that, although considerable in human terms, is close enough for astronomy to allow for key new observations.
The date that has grabbed the most headlines is, without a doubt, the December 22 of 2032. Initial calculations gave the asteroid a probability of impact with Earth of up to 3,2%, which earned it a level 3 on the Turin scale, a global benchmark for communicating the risk of collisions with space objects. This rating means the object deserves "special attention" but does not pose an imminent threat to humanity. The probability of impact has been fluctuating as astronomers refined their calculations. and new observations have been added, both from Earth and from space.
Risk Update: Is There a Real Threat to Earth?
In the months following the discovery, uncertainty about YR4's trajectory has reduced as data has been received. hundreds of additional observations telescopes around the world. The probability of collision with Earth, which initially worried the international community, has gradually decreased, from an initial 1%, rising to a maximum of 3,1%, and finally falling to practically zero values after new campaigns with state-of-the-art instruments such as the James Webb.
This sophisticated space telescope, observing in the infrared, was essential not only for understanding the size and nature of the asteroid, but also for measuring its position and speed with extremely high precision. Thanks to the images obtained in March and April 2025, experts have been able to rule out virtually any risk to our planet in 2032, leaving the probability of impact on Earth below 0,0011%.
Although uncertainty persists in orbital models, it is expected to further reduce during the 2028 flyby, when a new observation campaign is expected to map the asteroid's orbit in millimeter detail.
Risk of impact with the Moon: What if it hits our satellite?
Once the alarms about a possible collision with Earth have been cleared, scientific attention has shifted to the moonThe latest simulations estimate the probability of lunar impact around 4%, which in astronomical terms, although low, is much more significant than the terrestrial option. For astronomers, far from being a concern, the possibility of YR4 impacting the lunar surface presents itself as almost a historic opportunity.
The reason is simple: It would be the first time that the effect of an impact could be studied live with all the orbital and physical data of the asteroid known in advance.This way, telescopes and probes could measure the crater in real time, analyzing the relationship between the object's size, the energy released, and the resulting morphology on the Moon. Some scientists even believe the flash could be visible from Earth, offering a spectacle not only for research but also for the general public.
Risk zones on Earth: where could it have fallen?
Over the first few months of monitoring, ESA, NASA and other international agencies have performed complex calculations to delimit the “risk corridor"on the Earth's surface. Initial simulations indicated a geographical strip as potentially affected areas, It crosses the eastern Pacific Ocean, passes through northern South America (mainly Colombia, Venezuela and Ecuador), crosses the Atlantic Ocean, western and central Africa, and reaches southern Asia, especially India..
However, all these scenarios are based on projections subject to the enormous initial orbital uncertainty. As the orbit is refined, the risk corridor becomes narrower And the probability of impact on land drops even further. In any case, the possibility of the asteroid hitting the sea and generating a tsunami was discussed at length, especially by experts from coastal countries, who identify this type of event as the main secondary risk, even for areas far from the direct point of impact.
What damage could YR4 cause if it were to impact?
The destructive power of YR4 depends on several factors: the exact size, composition, speed, and angle of entry into the atmosphere. With a mass estimated by NASA at 220 million kilograms and a density typical of rocky asteroids (2,6 g/cm³), its impact energy would exceed 7,7 megatons of TNTIn practice, this means that a direct impact could destroy entire cities, creating a crater up to a kilometer in diameter and devastating areas up to 50 kilometers around.
Although the most plausible scenario is that the object explode in the air, as happened in Tunguska (Siberia) in 1908, releasing most of its energy into the atmosphere and creating a shock wave capable of leveling forests and buildings. If the impact were to occur in an oceanic area, the scientific community estimates that the generation of a tsunami of catastrophic proportions is unlikely, although dangerous waves could occur locally.
Therefore, The threat would always be localized, not global.Comparison with historical events such as the Barringer Crater (Arizona) or the Chelyabinsk impact in 2013 helps to assess their potential consequences.
International monitoring: protocols and coordinated actions
The asteroid YR4 has been the first to officially and coordinately activate the UN Planetary Security ProtocolThis has involved mobilizing the International Asteroid Warning Network, the Space Mission Advisory Group (SMPAG), and major international space agencies. The objective: ensure continuous surveillance and develop defense strategies if the risk could not be completely ruled out.
From the beginning, scientists have highlighted the importance of continuous observations and the constant refinement of the warning and orbital calculation systems. In fact, the probability of impact changed several times during the first few weeks, not only due to the collection of more data, but also due to phenomena such as the influence of solar radiation on the trajectory (the Yarkovsky effect) and other non-gravitational forces that, for these small objects, can significantly shift their orbit.
The Minor Planet Center has recorded more than 400 YR4 observations in just three monthsAs the asteroid moves away from Earth and enters a less observable zone, astronomers are confident that The most powerful space observatories and ground-based radars provide additional data in the next observation windows.
Planetary Defense: Is it possible to deflect an asteroid like YR4?
The case of YR4 has been a large-scale test of planetary defense protocols. Following the success of the mission NASA's DART in 2022, which managed to deflect the course of a small asteroid by impacting it with a probe, the international community expressed confidence that, if the risk of collision could not be ruled out in 2028, it would be feasible to launch a similar mission with the aim of modifying its orbit sufficiently to avoid colliding with Earth.
However, the decision on a possible diversion is not easy, since The direction in which pushing the asteroid could have geopolitical consequences, especially if the new risk corridor passes through different inhabited regions. Therefore, international coordination and anticipation are key elements.
Finally, experts emphasize the importance of global monitoring and collaboration in the face of these types of natural threats, which, although unlikely, can have devastating consequences in localized areas of the planet.
Lessons learned and future prospects
The YR4 asteroid episode has left several lessons for the scientific community and the public. The first, and perhaps most important, is that Today's science is capable of detecting, tracking and calculating the risk of potentially dangerous objects in advance.. Joint work between agencies, transparent data publication, and sustained investment in observation systems have made it possible, in just a few months, to move from a situation of uncertainty to one of almost complete tranquility.
In addition, the case has served to refine observation techniques, improve orbital models, and test international protocols. And, although the specific risk of YR4 has finally been ruled out, monitoring will continue, since The asteroid will be in the spotlight again in 2028, during its next significant approach to Earth.
The tracking of 2024 YR4 has been an extraordinary example of international cooperation in space science and of how knowledge and technology are advancing to protect us from natural hazards. Although this cosmic visitor ultimately poses no immediate threat, its passage has created a unique opportunity to study asteroid dynamics in depth and fine-tune prevention systems for future threats. Attention will remain focused on its trajectory, hoping that science will continue to shed light—and reassure us—on our planetary future.