The asteroid is approaching Earth on December 22, 2032. But don’t worry, the Webb Space Telescope has just confirmed that the probability of asteroid 2024 YR4 colliding with the Earth is almost 0%. However, astronomers cannot rule out a possible collision with the Moon.
The Asteroid Impact Last Alert System (ATLAS) in Chile detected the asteroid on December 27, 2024. Shortly after its discovery, asteroid 2024 YR4 was recognized as potentially dangerous, with a probability of collision with the Earth of almost 3%. These odds are not huge, but when it comes to the potential threat of a city-killer asteroid, ideally you want them to be closer to zero probability. On February 20, NASA removed 2024 YR4 from its list of naughty asteroids after calculations showed that the asteroid has a near-zero probability of hitting Earth.
Phew. The news gets even better – new observations from Webb double confirm that the asteroid poses no threat to Earth. As for the Moon, it’s obviously a different story.
When it was first spotted, asteroid 2024 YR4 was 515,116 miles (829,000 kilometers) from Earth. Since then, the space body has been moving away from us, and its next close approach will not occur until December 2028. The International Asteroid Warning Network’s ground-based telescopes are tracking the asteroid, but according to NASA, it will be too faint to observe until June 2028. That’s why Webb, which measures the asteroid’s brightness in the infrared wavelength range, was brought in to better determine its size.
At the end of January, a team of scientists proposed using the Webb’s mid-infrared instrument to observe the asteroid and better understand its destructive potential. The team recently published preliminary results of Webb’s observations of asteroid 2024 YR4, which indicate that although the asteroid is larger and rockier than previous observations, the probability of a collision with Earth during its future flyby is almost 0%. The results have not yet been submitted for peer review and publication.
Webb first spotted the asteroid on March 26, observing its rotation every 20 minutes for five hours. Using Webb’s observations, researchers determined that the asteroid is slightly larger than previously thought. Initial estimates suggested that the asteroid was 130 to 300 feet (40 to 90 meters) wide based on reflected light. However, Webb’s observations show the asteroid to be 200 feet (60 meters) wide.
Recent observations also indicate that the asteroid’s surface is colder than most other asteroids of the same size and at the same distance from the Sun, which may be due to the fact that asteroid 2024 YR4 is more rocky than usual. The team will use Webb to re-observe the asteroid in May to refine its thermal and orbital properties.
Webb’s observations could rule out a collision with Earth in seven years, but the results show that the asteroid “continues to have a non-zero probability of colliding with the Moon at this time,” the researchers concluded. Over its 4.5-billion-year history, the Moon has likely experienced thousands of asteroid impacts, but it’s not yet clear what would happen if asteroid 2024 YR4 hits our natural satellite. Current estimates are that the asteroid would likely release about 8 megatons of energy during the impact – more than 500 times the energy released by the atomic bomb dropped on Hiroshima in 1945 and comparable to the energy released during the 1908 Tunguska explosion, according to NASA.
The potential collision with the Moon will give scientists a rare opportunity to watch a lunar crater form before their eyes (provided it comes into view from Earth) and better understand the tumultuous history of the solar system.
