A recently discovered asteroid, named "2024 YR4", could cross Earth's trajectory in December 2032. With an estimated impact probability of 1.2%, this celestial body measuring 40 to 100 meters (130 to 330 feet) in diameter has drawn significant attention from astronomers.
Detected in late December 2023 by the ATLAS system in Chile, 2024 YR4 was quickly classified as level 3 on the Torino Scale, indicating an impact risk requiring increased monitoring. Although the probability remains low, this situation is unprecedented since the establishment of international warning systems in 1999. Scientists are now working to better understand its trajectory and characteristics to assess the real risks.
The Torino Scale: a tool to measure risks
The Torino Scale, created in the 1990s, allows asteroids to be classified based on their danger level. A level 0 means negligible risk, while a level 10 indicates a certain collision with catastrophic consequences. 2024 YR4, currently classified as level 3, represents a localized threat requiring special attention.
Only the asteroid Apophis had reached a higher level (4) in 2004, before being downgraded after additional observations. This scale helps astronomers prioritize their monitoring efforts and inform the public in a clear and measured manner.
A still uncertain trajectory
Initial estimates suggest that 2024 YR4 could pass approximately 106,000 kilometers (66,000 miles) from Earth in 2032. However, the margins of error remain significant due to the asteroid's current distance (43 million kilometers or 27 million miles). Observations continue to refine the calculations, but the object is currently moving away rapidly, limiting the available data until its next approach in 2028.
Astronomers emphasize that the impact probability could decrease with new observations. However, if it increases, measures could be considered, such as a deflection mission or evacuation plans for at-risk areas.
The potential consequences of an impact
If 2024 YR4 were to hit Earth, the damage would depend on its composition and impact point. A rocky asteroid would cause an atmospheric explosion similar to the Chelyabinsk event in 2013, while a metallic object could create a ground crater over a kilometer (0.6 miles) wide.
The most exposed areas include northern South America, central Africa, and southern Asia. However, since most of the Earth's surface is uninhabited, the risks of massive destruction remain limited. Scientists remind us that the probability of a destructive impact is low, but vigilance is still necessary.
An international collaboration to track 2024 YR4
The International Asteroid Warning Network (IAWN), supported by the UN, has placed 2024 YR4 at the top of its priorities. Telescopes around the world are focused on the object to collect essential data. Space agencies, including NASA and ESA, are collaborating to refine trajectory estimates and assess future risks.
This situation highlights the importance of planetary defense and monitoring systems. Although 2024 YR4 does not pose an immediate threat, it reminds us that Earth remains vulnerable to celestial objects.
What is a near-Earth asteroid?
A near-Earth asteroid is a celestial object whose orbit crosses Earth's, placing it at a potentially dangerous distance from our planet. These asteroids, often originating from the main belt between Mars and Jupiter, can range in size from a few meters to several kilometers in diameter.
Their trajectory is influenced by the gravitational forces of planets, making their movement sometimes unpredictable. Scientists closely monitor them to anticipate any collision risk, even though most pass at a safe distance.
Near-Earth asteroids are classified based on their size and minimum approach distance. Those larger than 140 meters (460 feet) and passing within 7.5 million kilometers (4.7 million miles) of Earth are considered potentially hazardous.
Finally, these objects also offer scientific opportunities. Their study helps us better understand the formation of the Solar System and develop planetary defense strategies, such as NASA's DART mission, which tested asteroid deflection in 2022.
To go further: How do astronomers calculate asteroid trajectories?
Astronomers determine asteroid trajectories by using repeated observations to calculate their position, velocity, and orbit. These data are collected through ground-based and space telescopes, which track the object's movement over several nights.
By precisely measuring the asteroid's position relative to stars, scientists can estimate its future trajectory. These calculations take into account the gravitational influences of planets, particularly Jupiter and Earth, which can alter the asteroid's orbit.
Initial uncertainties are often significant, especially for recently discovered objects. Over time and with additional observations, astronomers refine their estimates, reducing margins of error and more accurately assessing impact risks.
Finally, tools like numerical simulations and mathematical models help predict trajectories over decades or even centuries. These methods allow asteroids to be classified on the Torino Scale and preventive measures to be taken if necessary.
Article author: Cédric DEPOND