A 60-meter rock that most people had never heard of subtly rose to the status of the most dangerous object astronomers had recorded in 20 years during eight bizarre weeks in early 2025. Its name, 2024 YR4, sounded like a password, and its probability number was uncooperative. The likelihood of it striking Earth increased, decreased, and then disappeared. The odds of it striking the Moon persisted for a longer period of time, remaining at about 4.3 percent. This is the kind of number that seems insignificant until you try saying it aloud in front of planetary defense scientists in a conference room.
That number has since vanished. Astronomers confirmed last month that the asteroid will miss the Moon by more than 20,000 kilometers when it passes in December 2032 using the Near-Infrared Camera on the James Webb Space Telescope. There was a certain kind of exhale within the community even though the announcement was made quietly and obscured by larger headlines. One of the scientists, Julien de Wit, observed that the asteroid was four billion times fainter than what is visible to the human eye. The telescope managed to locate it. Sitting with that part is worthwhile.
| Asteroid 2024 YR4 — Key Facts | Details |
|---|---|
| Discovered | December 27, 2024 by ATLAS (Hawaii) |
| Estimated Diameter | Roughly 60 metres (197 feet) |
| Initial Risk Category | Highest-rated asteroid in 20 years |
| Moon Impact Probability (Feb 2025) | 4.3% for Dec 22, 2032 |
| New Moon Impact Probability | 0% — will miss by over 20,000 km |
| Confirming Instrument | NIRCam on James Webb Space Telescope |
| Observation Window | February 18–26, 2026 |
| Energy of Potential Lunar Impact | Equivalent to roughly 6 million tons of TNT |
| Next Close Approach to Earth | December 22, 2032 |
Webb wasn’t designed to do this. The choice to aim it at a faint speck floating through our own cosmic backyard feels almost like using a cathedral to look at a candle because it was made to study galaxies so old that their light has been traveling since before Earth existed. Just 2.2 square arcminutes, or about the area of a pinhead held at arm’s length, make up the camera’s field of view. Nevertheless, the Webb team, NASA’s Center for Near-Earth Object Studies, and ESA’s Near-Earth Object office worked together to locate it. Twice, separated by eight days.
What remains is this. The European Space Agency’s Gaia spacecraft, which has mapped the locations of about two billion stars with remarkable accuracy over the last ten years, is the reason they were able to do it at all. There would have been nothing to compare the asteroid to without that background catalogue. In other words, the rescue was constructed over a 20-year period by a number of agencies and individuals who had no idea which particular rock they were getting ready to track.
2024 YR4 isn’t the uncomfortable part. It’s all it suggests. Just two years prior to its first close encounter, the asteroid was only found in late December 2024. The window for a response would have been so small that it would have been offensive if it had been slightly bigger, slightly earlier in its orbit, or slightly better aimed. This kind of impact releases energy equal to about six million tons of TNT, which would have carved a crater on the Moon that would have been visible from Earth for months or even years. A mid-sized city could be destroyed by the same rock on Earth.
For the majority of the modern era, planetary defense has been viewed as a problem that falls somewhere between hypothetical and embarrassing. Usually, after bringing up the dinosaurs, the discussion continues. For a brief and uncomfortable period, 2024 YR4 changed the verb tense. It ceased to be speculative. The Moon is secure. The asteroid is going to pass. However, the miss isn’t the true story. It’s that we nearly missed it, and the only reason we did was because of a series of choices made by people who aren’t here to answer the phone.
