New Delhi: The asteroid designated as 2024 YR4 was initially detected on 27 December 2024 by the Asteroid Terrestrial-impact Last Alert System (ATLAS), a NASA-funded early warning system in Chile. Initial analysis indicated a slight chance of a collision with the Earth in 2032, with the impact risk dropping as the orbit was measured with further precision. There remained a small chance that the asteroid could impact the Moon. Follow-up observations revealed that 2024 was a stony asteroid, rich in silicates, and was probably kicked into the vicinity of the Earth by the gravitational influence of Jupiter. Astronomers also planned to observe 2024 YR4 with the James Webb Space Telescope, and the results are now in.
The observations have been used to further refine the orbit of 2024 YR4, which is now expected to pass the lunar surface at a distance of 21,200 km in 2032. The asteroid was not observable from both Earth and space-based astronomical instruments, with the exception of Webb. The observation team used Webb to capture two observations in 2024. NASA has concluded that the object poses no significant impact risk to the Earth on 22 December, 2032, or through the next century. It is typical for risk models based on initial observations to be refined once additional observational data is gathered.
Among the faintest asteroid observations by Webb
The researchers requested director’s discretionary time on Webb to jump the queue of astronomers waiting for time on the flagship deep space telescope that also observes targets closer home when required. 2024 YR4 is exceptionally faint, reflecting about as much light as an almond as far away as the Moon, and Webb is the only observatory that is sensitive enough to observe the asteroid. The precise moving-target tracking ensured that the asteroid did not move even by a pixel across several, multi-hour exposures. These observations give scientists the confidence that they can use Webb to observe other faint, moving targets in the future.