2026 NIRCam Observations of 2024 YR4

Asteroid 2024 YR4 poses no impact risk to Earth during its 2032 December 22 close approach (Micheli et al. 2026, Farnocchia et al. 2026). However, its projected probability of a lunar impact in 2032 has been approximately 4% since its last observation in late spring 2025. JWST observations in March and May 2025 constrained the size of 2024 YR4 to 60 ± 7 m (Rivkin et al. 2025). While this 60 m object does not threaten Earth directly, a lunar impact of this scale could affect the reliability and resilience of Earth–Moon orbital infrastructure (Wiegert et al. 2025, He et al. 2026), and is of additional interest due to the possibility of human exploration at that time. New astrometric measurements obtained with JWST/NIRCam on 2026 February 18 and 26 extend the observational arc by eight months and reduce the 2032 lunar B-plane uncertainty by more than an order of magnitude. These measurements demonstrate that 2024 YR4 will pass at 22 900 ± 800 (1σ) km from the center of the Moon, thus ruling out a lunar impact, in agreement with the official assessments by NASA [1] and ESA [2]. The JWST team achieved this refinement approximately two years in advance of the next possible ground-based recovery of the asteroid, materially advancing the timeline for hazard assessment. The sequence of infrared size determination followed by deep-space astrometric orbit refinement illustrates the operational role JWST and future facilities like the Habitable Worlds Observatory (Dotson et al. 2025) can play in precision planetary-defense assessments for faint (Vmag < 31), decameter-scale near-Earth objects beyond the reach of ground-based facilities (Burdanov et al. 2025).