NASA Monitors ‘City-Killer’ Asteroid Before It Vanishes Until 2028

Astronomers are closely tracking asteroid 2024 YR4, a space rock once considered a potential threat to Earth, before it disappears from view until 2028. NASA’s efforts to monitor the asteroid, which was recently observed using the powerful James Webb Space Telescope, have provided new insights into its size and trajectory. While it is no longer seen as a danger to Earth, its potential to impact the moon remains a topic of concern.

What We Know About Asteroid 2024 YR4

Asteroid 2024 YR4 was first discovered on December 27, 2024, by astronomers at the ATLAS telescope in Hawaii. With an elongated orbit that takes it around the sun and near Earth, the asteroid was initially feared to have a 3.1% chance of striking Earth in December 2032. However, further observations have since ruled out this possibility.

• Size: Between 174 to 220 feet in diameter, roughly the size of a 10-story building.
• Orbit: Its orbit spans from Earth’s vicinity to the region between Mars and Jupiter, making it challenging to track when it moves out of sight.
• Current Threat: The asteroid now poses a 1.7% chance of hitting the moon on December 22, 2032.

The Role of NASA’s James Webb Space Telescope

NASA’s Center for Near-Earth Object Studies used the James Webb Space Telescope, the most powerful space telescope ever built, to capture detailed infrared images of the asteroid. These observations have provided a clearer understanding of its size and trajectory. The telescope’s ability to measure the asteroid’s heat emission helped confirm its dimensions and composition.

Why the “City-Killer” Label?

The asteroid has earned the nickname “city-killer” due to its potential for widespread destruction should it strike a populated area. While it’s not large enough to cause global devastation, its size is sufficient to cause significant localized damage, similar to the impact of the 1908 Tunguska event in Siberia, where a similarly sized asteroid exploded and flattened trees across a vast area.

The Moon Impact Possibility

While it no longer poses a threat to Earth, its chance of hitting the moon has steadily increased. NASA’s recent observations show a 3.8% chance of it colliding with Earth’s satellite. While this may sound alarming, it’s important to note that a moon impact would not pose a direct danger to Earth. Scientists, however, view the potential impact as a rare opportunity for scientific observation.

Scientists are eager to study the results of a moon collision, as it would provide valuable data for future planetary defense strategies.

The Future of Asteroid Monitoring

Although asteroid 2024 YR4 won’t return until 2028, NASA and other space agencies will keep monitoring its orbit and tracking any changes in its trajectory. The asteroid underscores the need for ongoing efforts to detect and assess potentially hazardous space objects.

As part of their planetary defense mandate, Congress has tasked NASA with locating asteroids that could pose a regional threat to Earth. Asteroids larger than 450 feet, like 2024 YR4, fall under this category, and monitoring efforts continue to mitigate any potential risks.

More…

• https://science.nasa.gov/blogs/planetary-defense/2025/04/02/nasa-update-on-the-size-estimate-and-lunar-impact-probability-of-asteroid-2024-yr4
• https://abcnews.go.com/US/nasa-catches-glimpse-city-killer-asteroid-disappears-2028/story?id=120449970
• https://phys.org/news/2025-04-odds-asteroid-briefly-threatened-earth.html#google_vignette