The European Space Agency (ESA) recently confirmed that 2024 YR4, once considered the "most dangerous" near-Earth asteroid in 20 years, will not hit the moon in 2032, but will pass by the lunar surface at a safe distance of more than 20,000 kilometers that year.
This near-Earth object, which is about 60 meters in diameter, attracted global attention last year. Initial observation data shows that its potential threat in the next few decades ranks first among known asteroids, and it was once considered possible to impact the Earth. With subsequent orbit calculations, the scientific research team quickly ruled out the possibility of an impact on the Earth. However, for the scenario of a collision with the moon on December 22, 2032, there is still a residual probability of about 4%, becoming an unresolved source of risk.
The latest results come from the James Webb Space Telescope (JWST), a joint NASA/ESA/Canadian Space Agency project. The scientific research team used the near-infrared camera (NIRCam) onboard to once again successfully capture the asteroid that almost disappeared from the field of view within an extremely limited time window, and thereby significantly improved the accuracy of its orbital parameters. Observations show that 2024 YR4 will "pass by" the moon in 2032 and will not impact. This also means that this long-standing uncertainty in people's minds has been officially lifted.
After drifting away from Earth and rapidly declining in brightness last spring, 2024 YR4 is generally not expected to be observed by telescopes again until 2028. However, an international team of astronomers from many countries, through precise orbit calculations and star catalog data analysis, "squeezed" two extremely narrow observation opportunities for the Webb Telescope in February 2026. Their goal is to find an almost invisible faint spot in the vast sea of stars in an area of the sky where the background of stars is sparse and the star positions have been accurately determined by ESA's "Gaia" mission.
This task is extremely difficult. The Webb telescope was originally designed to observe galaxies and large-scale structures of the universe billions of light-years away. Its field of view is very narrow. It is aimed at a faint asteroid in near-Earth space. It not only exceeds the conventional mission mode, but also puts forward almost demanding requirements for pointing accuracy and orbit prediction. The research team needs to locate the target at a distance of millions of kilometers and deduce its orbital changes in the next seven years. There is no room for error.
To this end, ESA's Near-Earth Object Coordination Center, NASA's Near-Earth Object Research Center, and the Webb Telescope project team have worked closely together to conduct a fine division of labor from observation window design, attitude planning, to data processing and orbit fitting. In the end, the team successfully obtained a high-precision orbit solution by comparing the position of 2024 YR4 relative to background stars, which was enough to rule out all possible scenarios of its impact on the moon in 2032.
Behind this is the cumulative result of decades of continuous investment and international cooperation in the fields of science, engineering and planetary defense. Through this "most powerful robotic telescope in space", human beings stared at a distant "dust" in the depths of the universe and gave a clear answer that is relevant to all mankind: the threat of this asteroid has been eliminated.
Although the moon is determined to be safe and 2024 YR4 has been proven not to pose a threat, the work of planetary defense is far from over. The planetary defense team under the ESA space security program is still continuing to carry out the detection and orbital monitoring of near-Earth objects, hoping to detect them as early as possible and gain enough response time before truly dangerous targets appear in the future, so as to ensure that humans will not be caught off guard at critical moments.