NASA's James Webb Space Telescope has observed asteroid 2024 YR4, revealing it to be roughly 60 meters in diameter-about the height of a 15-story building-and confirming it poses no significant threat to Earth in 2032 or thereafter.
The study, led by Andy Rivkin of the Johns Hopkins University Applied Physics Laboratory, utilized Webb's Director's Discretionary Time to analyze this unusual by Clarence Oxford
Los Angeles CA (SPX) Apr 03, 2025
NASA's James Webb Space Telescope has observed asteroid 2024 YR4, revealing it to be roughly 60 meters in diameter-about the height of a 15-story building-and confirming it poses no significant threat to Earth in 2032 or thereafter.
The study, led by Andy Rivkin of the Johns Hopkins University Applied Physics Laboratory, utilized Webb's Director's Discretionary Time to analyze this unusually small asteroid, the tiniest object the observatory has examined so far.
Earlier assessments had indicated a potential impact risk from 2024 YR4 in 2032, but by late February NASA officially reduced that probability to near zero. Nevertheless, researchers aimed to extract as much data as possible on the asteroid's physical characteristics. According to Rivkin, understanding the nature of small near-Earth objects is essential for hazard assessment, especially as future asteroid search initiatives are expected to detect many more.
To measure 2024 YR4's size and surface features, scientists employed both NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument). While NIRCam focused on reflected sunlight to gauge surface reflectivity and composition, MIRI captured the infrared heat emitted by the asteroid, allowing for a more precise size estimate. Combining these datasets enabled the team to calculate not only the asteroid's dimensions but also its albedo, or surface reflectivity, which is closely tied to its composition.
Although the risk of a future collision has been ruled out, Webb's observations are vital for developing protocols to handle potential asteroid threats. Rivkin emphasized the importance of practicing how best to utilize the telescope's capabilities, noting that this preparation is critical in the event a more threatening object is detected.
Data from Webb indicated that the asteroid exhibits thermal properties unlike those of larger bodies. The surface appears to lack fine-grained regolith and may be dominated by coarser rocks, possibly due to its rapid rotation. This insight helps researchers infer how the asteroid responds to solar heating and cooling, which in turn informs models of similar-sized objects.
The Webb findings complement data from ground-based telescopes that tracked the asteroid's motion and analyzed its spectral profile. These combined efforts have refined our understanding of 2024 YR4's orbit and composition, strengthening international planetary defense efforts. Such comprehensive studies are coordinated through organizations like NASA's Planetary Defense Coordination Office and the International Asteroid Warning Network.
Ultimately, 2024 YR4 serves as a test case for enhancing our knowledge of small near-Earth asteroids, offering a benchmark for interpreting the characteristics of future discoveries that might come too close for comfort.
Research Report:JWST Observations of Potentially Hazardous Asteroid 2024 YR4
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