NASA Update on the Size Estimate and Lunar Impact Probability of Asteroid 2024 YR4
Since near-Earth asteroid 2024 YR4 was first discovered in December 2024, NASA and the worldwide planetary defense community have continued to observe the asteroid, which was ruled out as a significant impact risk to Earth. New infrared observations from NASA’s James Webb Space Telescope have decreased the uncertainty of the asteroid’s size and 2024 YR4 is now estimated to be 174-220 feet (53-67 meters), about the size of a 10-story building. The previous size estimate of 131-295 feet (40-90 meters) was derived from visible light measurements from ground-based telescopes.
Experts at NASA’s Center for Near Earth Object Studies at the agency’s Jet Propulsion Laboratory have updated 2024 YR4’s chance of impacting the Moon on Dec. 22, 2032 from 1.7% as of late February to 3.8% based on the Webb data and observations from ground-based telescopes. There is still a 96.2% chance that the asteroid will miss the Moon. In the small chance that the asteroid were to impact, it would not alter the Moon’s orbit.
After mid-April, asteroid 2024 YR4 will be too far and faint to be observed by ground-based telescopes but Webb will observe the asteroid again in either late April or early May.