James Webb Space Telescope Joins the Hunt for Asteroid 2024 YR4
Why Asteroid 2024 YR4 Needs Webb’s Eyes
The NASA/ESA/CSA James Webb Space Telescope will be used by astronomers to gather more precise measurements of asteroid 2024 YR4, a near-Earth object with a slim possibility—currently around 2%—of colliding with Earth in 2032. These observations are expected to help rule out an impact and clarify the asteroid’s true size.
A Quick Look at 2024 YR4
- Discovery: 27 December 2024
- Current Impact Odds: ~2% chance of hitting Earth on 22 December 2032
- Size Estimate: 40–90 m in diameter (uncertainty remains due to unknown reflectivity)
- Visibility Window: YR4 will soon fade from ground-based telescopes and won’t be observable again until 2028
Although this asteroid is unlikely to trigger global devastation, its close pass is significant enough to warrant detailed study—especially if it turns out to be closer to 90 meters in diameter rather than 40.
Why Does Size Matter So Much?
Determining whether an impact is possible is only one part of the equation; the other crucial aspect is how destructive that impact could be. An object around 40 m in diameter might cause substantial yet localized damage, while a 90 m asteroid could pose a severe regional threat. Ground-based observations rely heavily on visible light reflectivity, leading to significant uncertainties about composition and exact size.
Enter the James Webb Telescope
Unlike most optical telescopes, Webb observes infrared light (heat), enabling much more accurate size measurements. By capturing data from Webb’s Mid-Infrared Instrument (MIRI) and NIRCam, astronomers can refine the asteroid’s diameter and trajectory before 2024 YR4 moves out of range for several years.
Observation Timeline
- Early March: Initial observations will occur when 2024 YR4 is brightest to Webb’s instruments.
- May: Follow-up observations will track thermal changes as the asteroid moves farther from the Sun, providing final orbital updates until 2028.
Observing Description (2025)
*“MIRI imaging is requested in March with three filters: F1280W, F1130W, and F1500W. The plan involves cycling through the latter two filters with F1280W between each observation.
Approximately 20-minute exposures are proposed, averaging over 2024 YR4’s entire rotation period and allowing up-the-ramp measurements that could reveal rotationally-resolved thermal properties. Five such exposures total 100 minutes, not including overhead.
An additional 20 minutes of integration has been proposed using NIRCam with the F150W2 and F322W2 filters to enable more refined thermal modeling and support ground-based astrometry. Including those 20 minutes, the total request for March 2025 is two hours of integration.
A further 20 minutes of NIRCam time in May 2025 is requested using the same filters to acquire additional astrometric data.
In total, 6.3 hours are requested when overhead is included.”
These critical observations leverage Director’s Discretionary Time, typically set aside for time-sensitive research or unexpected discoveries, ensuring data can be collected before 2024 YR4 dims beyond Webb’s capabilities.
Who Is Behind the Observations?
An international consortium, led by ESA’s Planetary Defence Office and involving NASA and other agencies, proposed using Webb for this urgent investigation. Once approved, roughly four hours of direct observation time—plus additional overhead—were allocated, totaling 6.3 hours. All resulting data will be released publicly, allowing researchers worldwide to refine 2024 YR4’s orbit and risk level.
About the James Webb Space Telescope
Webb stands as the largest and most powerful space telescope ever launched, realized through an international collaboration among NASA, ESA, and the Canadian Space Agency (CSA). ESA contributed the Ariane 5 launch vehicle, the NIRSpec instrument, and part of MIRI via the MIRI European Consortium. Webb’s advanced infrared capabilities and high-resolution imaging make it uniquely suited for studying objects like 2024 YR4, which might otherwise remain too dim or poorly understood.
By obtaining clearer data on this asteroid’s size and path, global experts gain vital information for planetary defense. If 2024 YR4 appears larger than previously thought, preemptive measures or continued monitoring efforts might be escalated. If smaller, confidence can grow that the future flyby in 2032 will be harmless—yet another near miss in Earth’s ongoing celestial dance.