The James Webb Space Telescope (JWST) recently provided crucial data showing that asteroid 2024 YR4 won’t collide with the moon. Instead, it’ll safely zip by at a distance of around 13,200 miles (21,200 kilometers).
This asteroid was first spotted on December 27, 2024, by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS). For a brief moment, it was considered one of the most dangerous asteroids detected, with a diameter of about 197 feet (60 meters). Initially, there was a chance it could hit Earth on December 22, 2032, which would have posed a significant threat to any city it struck or could have caused devastating tsunamis if it landed in the ocean.
Fortunately, calculations soon revealed it would miss Earth. However, the risk of hitting the moon still loomed with a 4.3% chance of collision due to the uncertainty of its orbit. This uncertainty was because astronomers didn’t have precise data on the asteroid’s path around the sun.
In an unexpected twist, researchers at Johns Hopkins University’s Applied Physics Laboratory discovered that the JWST could observe 2024 YR4 from February 18 to February 26 this year. During this time, the asteroid moved against a fixed field of stars tracked by the European Space Agency’s Gaia mission. By measuring how 2024 YR4 moved relative to these stars, scientists were able to refine its orbit accurately. This task was challenging since the JWST’s field of view is quite small, only 2.2 square arcminutes.
With its newly refined orbit, astronomers were able to eliminate the risk of a moon collision. Instead, 2024 YR4 will pass at a safe distance, leaving no cause for alarm this time. However, had it impacted the moon, the event would have provided a spectacular sight from Earth—like a brilliant flash and a new crater 0.62 miles (1 kilometer) wide. Such an impact would have the energy equivalent to 6 million tons of TNT, akin to a large nuclear explosion. The aftermath could have created a meteor shower visible from Earth, while debris could have posed risks to satellites in orbit.
As experts in planetary defense stress, it’s crucial to keep monitoring asteroids. According to a recent report from NASA, over 27,000 near-Earth objects (NEOs) have been discovered, and that number continues to grow. This highlights the importance of ongoing observation and research to keep our planet safe. While 2024 YR4 is now off the hook, the universe is filled with potential threats—we must stay vigilant.
In the end, while 2024 YR4’s trajectory no longer raises concerns, our planet’s defense system must be prepared for future encounters with asteroids. Keeping an eye on the skies gives us a better chance to safeguard Earth.
