Asteroid 2024 YR4 became the first in history to hold a level 3 rating on the Turin Scale of asteroid threat for several weeks, indicating a collision probability with Earth exceeding 1% and a potential local impact risk. Discovered towards the end of 2024, this object drew global attention from astronomers and planetary defense services, prompting the activation of major telescopes to urgently refine its trajectory in January and February 2025. Unlike most near-Earth asteroids, the risk associated with 2024 YR4 increased as more data accrued, rather than decreased. On January 27, it was officially assigned a level 3 on the Turin Scale, and by February 18, the collision probability reached 3.1% – the highest and most stable since observations of asteroid Apophis in 2004. This situation required an official notification to the International Asteroid Warning Network (IAWN), established in the aftermath of the Chelyabinsk meteor incident.
The Catalina Sky Survey, Gran Telescopio Canarias, and Very Large Telescope joined the active observation efforts, allowing for a more detailed understanding of the asteroid’s shape and physical attributes: its rotation period was determined to be 19.5 minutes, significantly faster than typical asteroids of this type. Classification of 2024 YR4 remains debated (Sq- or K-type) due to differing albedo data based on the instruments used. As the orbit was refined, the threat of an Earth collision was dismissed, but the probability of an impact on the Moon in 2032 increased to 4%. In such an event, a debris cloud might be ejected, theoretically posing additional risk to satellites in Earth’s orbit, according to expert assessments.
Asteroid 2024 YR4 became a rare real-world test of the global planetary defense system. It not only demonstrated that detection, alert, and coordination mechanisms are operational but also highlighted vulnerabilities-ranging from high uncertainty in the initial weeks after discovery to limited access to large telescopes for urgent observations. This case is already reviewed by specialists as a model scenario for future potentially hazardous objects.
