The most dangerous asteroid of the last 20 years is finally ruled out

Space · Published 22 October 2026 Swipe more like this →

In short: When asteroid 2024 YR4 was first spotted, it sent shockwaves through the scientific community as a potential city-killer. While an Earth impact was quickly dismissed, a lingering threat to our Moon remained—until NASA used one of humanity's most complex machines to track its path with unprecedented precision.

Discovered in December 2024, asteroid 2024 YR4 became notorious as the most dangerous space rock identified in two decades. Measuring approximately 60 meters across—roughly the size of a 15-story building—it initially posed a 3.1 percent chance of striking Earth on December 22, 2032. Such an impact would have released energy comparable to several atomic bombs, capable of devastating a major metropolis.

While scientists soon ruled out a direct hit on Earth, the threat shifted to our Moon. For a period, calculations suggested a lingering 4 percent chance (or about 1-in-23) that the asteroid would slam into the lunar surface on that same date in 2032. Because the object faded from view as it raced away from our solar system, astronomers had to rely on complex orbital modeling to predict its position years into the future.

The mystery was solved using the James Webb Space Telescope (JWST). Although designed to study ancient galaxies and black holes rather than planetary defense, its Near-Infrared Camera (NIRCam) allowed researchers to detect the asteroid as a faint speck against known stars. NASA and ESA researchers verified that the object would clear the Moon by over 20,000 kilometres after gathering data on 18 February and 26 February, 2025, when it was situated 450 million kilometres away.

This success highlights a growing trend in planetary defense: using high-precision infrared technology to track 'invisible' objects. The collaboration between the Center for Near-Earth Object Studies, the ESA’s Near-Earth Object Coordination Centre, and the Webb mission team demonstrated how repurposing elite deep-space tools can provide definitive answers to immediate terrestrial risks.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• The 'City-Killer' asteroid that triggered a global planetary defense alert
• A 1 in 23 chance of an asteroid hitting the Moon
• The 1.5 percent chance that could devastate a city
• Why the asteroid headlines are likely causing more alarm than actual danger
• Why a 1% chance of impact is still a scientific mystery
• Mars may owe its lopsided face to a Pluto-sized collision
• The main sequence: the long, steady middle age of nearly every star
• A rare celestial encounter as a comet grazes the Red Planet
• Star magnitudes run backwards because they began as a ranking of size
• The harsh realities of settling the Red Planet by 2050
• The oldest recorded meteor shower in human history
• A cosmic catastrophe 11,000 light-years away mirrors our own origins

More in Astronomy · More in Space · Latest · A–Z · All topics