Early in 2024, asteroid 2024 YR4 was identified as a possible impact risk, with projections suggesting a chance of collision with Earth in 2032. The alert prompted immediate observation efforts by NASA and international agencies.
By late February, improved data analysis ruled out any significant impact threat. This shift allowed researchers to focus on the scientific potential of studying the asteroid more closely.
A research team led by Andy Rivkin from Johns Hopkins University Applied Physics Laboratory used discretionary time on the James Webb Space Telescope to examine YR4. It marked the smallest object yet observed by the telescope.
Using Webb’s NIRCam and MIRI instruments, scientists measured the asteroid’s size (approximately 60 metres in diameter) and surface characteristics. The reflectivity and thermal behaviour of the asteroid differed from typical models.
YR4 exhibited a rapid spin rate and thermal properties indicating a surface made up of coarse, rock-sized fragments, rather than fine dust. This suggests that its rotation might prevent regolith accumulation, exposing bare rock instead.
Though not a threat, the detailed study of YR4 supports ongoing planetary defence strategies. Data from Webb can complement optical tracking on Earth to refine asteroid models and response planning.
With improved detection capabilities, more small near-Earth objects are likely to be discovered. The study of YR4 serves as a precedent for rapid telescope deployment and analysis in future cases of potential asteroid hazards.