Tracking from the Canary Islands

Astronomers utilized the 2.5-meter Nordic Optical Telescope (NOT) in La Palma, Canary Islands—an essential instrument long used by Finnish researchers to monitor near-Earth objects—to obtain precise measurements of the asteroid's position and movement.

Figure 1. Asteroid 2024 YR4 Sparks Global Concern – Potential Lunar Impact Detected.

“We’ve been concentrating on determining the asteroid’s exact location and motion, along with analyzing its rotation, size, and shape. These details are key to improving our predictions of its future path and refining thelikelihood of any potential impact,” explains Gray. Figure 1 shows Asteroid 2024 YR4 Sparks Global Concern – Potential Lunar Impact Detected.

“Our latest observations highlight the critical role NOT continues to play in global planetary defense efforts,” adds Fedorets.

Lunar Impact Risk Emerges

In mid-February, asteroid 2024 YR4 reached a peak impact probability of 3%—the highest ever recorded for an asteroid of its size capable of posing a serious threat, according to historical impact risk estimates.

Observations were temporarily paused as the brightness of the full moon obscured the asteroid’s faint signal. However, Finnish researchers were the first to resume data collection after the full moon phase. Their updated observations led to a sharp reduction in the asteroid’s impact probability, which now sits at less than 0.001%.

At the same time, new data has revealed a different, albeit smaller, concern: there is now a 4% chance the asteroid could collide with the Moon instead.

“If 2024 YR4 were to strike the Moon, it could release debris from both the lunar surface and the asteroid itself, potentially endangering satellites and other human infrastructure in space,” explains Academy Professor Karri Muinonen.

James Webb Delivers Crucial Infrared Data

On March 26th, the James Webb Space Telescope successfully observed asteroid 2024 YR4, providing essential infrared data. Postdoctoral researcher Eric MacLennan, a key member of the team analyzing the asteroid’s thermal properties, highlighted the telescope’s unique role—currently the only one capable of measuring thermal emission directly.

“The asteroid’s initial size estimate was based solely on visible light, which is influenced by both its dimensions and surface reflectivity. Infrared thermal emission, however, gives us a much clearer measurement of its true size. Our first attempt to detect this on March 8 wasn’t successful, so it was a relief when we finally received usable images,” MacLennan explains.

Following detailed analysis, the team concluded there’s a 95% probability the asteroid’s diameter falls between 46 and 74 meters. This refined measurement is vital for evaluating the potential consequences of a lunar impact.

Although the threat to Earth has significantly diminished, both ground-based and space-based observatories will continue monitoring YR4 through April or May 2025. After that, the asteroid will no longer be visible from Earth until its next close approach in 2028.

Nordic Observatories Prove Invaluable

In February, the Nordic Optical Telescope (NOT) emerged as one of the fastest and most precise contributors of data among global observatories involved in planetary defense—a reflection of the sustained commitment and expertise of its staff, engineers, students, and scientists from the Nordic countries.

Space Situational Awareness Expands

In Finland, the responsibility for assessing the risks posed by near-Earth objects lies with the National Land Survey. This role will soon be shared with the newly forming Space Situational Awareness Center. The center, currently under development, will play a crucial role in monitoring not only asteroid threats but also other space-related hazards, including space weather, orbital debris, and satellite activity.

Source: SciTECHDaily

Cite this article:

Priyadharshini S (2025), Asteroid 2024 YR4 Triggers Global Alert – Now on Course to Possibly Strike the Moon Instead, AnaTechMaz, pp.331