by Clarence Oxford
Los Angeles CA (SPX) Mar 30, 2026
NASA used the James Webb Space Telescope to make new observations of the asteroid 2024 YR4, which confirms that it will pass safely by the Earth and the Moon in 2032. The asteroid had already been ruled out as a major threat to the Earth, but the latest data eliminates the first non-zero possibility of an impact on the moon during that year.
The Webb mission was targeting 2024 YR4 under the Director’s Discretionary Time program designed to optimize the asteroid’s orbit using the observer’s extreme sensitivity and tracking capabilities. Without Webb, astronomers would have had to wait until 2028, when the asteroid returns to the inner solar system, to obtain comparable measurements and reduce the remaining uncertainties in its predicted path.
Currently, 2024 YR4 is incredibly faint, reflecting light about the size of an almond far from the Moon, and about 30 magnitudes, about 4 billion times brighter than the faintest stars visible to the naked eye. Webb is currently the only observatory capable of detecting and tracking such a small object with the necessary accuracy and stability, enabling several hours of exposure where the asteroid has not moved even a single pixel.
A combined count of these observations from February 26, 2026, shows the asteroid is clearly seen at a position offset by about 22 pixels, or about 0.5 arcseconds, from where it would have appeared if the 2032 lunar impact was still possible. This change in position is enough to control the impact conditions and ensures that the 2032 asteroid’s path will miss the Moon. The new measures extend the 2024 YR4 rate from May 2025 to the end of February 2026, nearly doubling the period its status has been tracked.
Accurate asteroid trajectory estimates depend on accurate positions and long observation arcs, and Webb’s data greatly improves both for 2024 YR4. Orbital dynamicists are now able to calculate the future trajectory of an asteroid with high confidence, removing potential concerns for satellite operators and astronomers who rely on the stability of the cislunar environment. The refined path shows that a lunar impact in 2032 is no longer a possibility under the improved solution.
The observing campaign also provided an opportunity to test and validate new methods for extracting reliable stars from images that include very faint objects and very bright stars. The team had to overcome challenges related to the large differences between asteroids and stars used for weather forecasting. Webb’s Near Infrared Camera and optical design provided data of sufficient quality for these techniques to be successful, indicating that similarly demanding measurements can be repeated for other targets in the future.
Outside of the immediate case of 2024 YR4, the results highlight Webb’s role as a planetary security tool, complementing other assets by providing unique capabilities for early orbit updates of hard-to-observe objects. Webb is able to measure the physical properties and exact positions of asteroids at distances or light levels that cannot be reached by ground-based telescopes and most space-based observatories. This allows NASA to identify potentially hazardous objects long before they become available again to conventional research telescopes.
NASA notes that Webb is not the only interstellar mission with planetary defense applications and near-Earth asteroid studies. The upcoming Nancy Grace Roman Space Telescope will survey vast swaths of the sky and is expected to spot asteroids quietly, with the potential to disrupt their orbits. The proposed Habitable Worlds Observatory is also expected to provide unprecedented sensitivity, providing another way to update asteroid trajectories at earlier stages of discovery and tracking.
Similarly, NASA is developing the Near-Earth Object Surveyor mission, which will use the agency’s legacy in space telescopes to directly target an asteroid. Together, these assets exemplify a comprehensive, integrated approach to planetary protection that spans multiple divisions within NASA Science. Webb’s observations of 2024 YR4 serve as the first indication of how this advanced instrument can handle certain hazards and confirm the methods that will be used for potentially dangerous objects in the future.
The experience gained in designing, implementing, and analyzing Webb’s concept of such a limited objective is considered as important as the specific outcome of 2024 YR4. By successfully detecting and accurately locating an asteroid under these extreme conditions, the team has shown that similar campaigns can be carried out for other objects that may raise questions about potential impacts. As new near-Earth asteroids are discovered and cataloged, NASA will be able to use this work to quickly plan the latest observations and refine their trajectories well before they approach Earth or the Moon.
Related Links
NASA
Asteroid and Comet Mission News, Science and Technology
#Webbs #observations #confirm #safe #lunar #passage #asteroid #YR4