In January and February 2024, asteroid 2024 YR4 briefly raised concerns after initial calculations suggested a 1-in-83 chance of it striking Earth in 2032. At the time, this translated to a roughly 1% impact risk. However, as astronomers gathered more data, the probability of a collision dropped to near zero by late February.
Despite the reduced threat, scientists remained interested in 2024 YR4. Using the James Webb Space Telescope (JWST), astronomers observed the asteroid in both visible and thermal light, providing new insights into its structure and composition.
JWST’s observations determined that 2024 YR4 is about 200 feet (60 meters) in diameter—roughly the height of a 15-story building. These measurements help classify the asteroid and assess its physical characteristics.
By studying how the asteroid absorbs and releases heat, researchers found that 2024 YR4 behaves differently from larger asteroids. The rapid heating and cooling suggest it has a rocky surface with relatively large stones, rather than a fine, sandy texture.
Scientists suspect that the asteroid's fast spin contributes to its unusual thermal behavior. Unlike some larger asteroids, which have smoother, more insulated surfaces, 2024 YR4’s rugged terrain may affect how it interacts with sunlight and space temperatures.
Understanding the properties of asteroids like 2024 YR4 is crucial for future planetary defense strategies. The study shows how space telescopes like JWST can quickly assess potential impact threats and guide responses to possible asteroid encounters.
The study, published in Research Notes of the AAS, highlights how JWST’s advanced instruments can provide critical data on near-Earth objects. Scientists will continue refining their techniques to monitor and characterise asteroids that might pose a threat in the future.