On January 27, 2025, asteroid 2024 YR4 crossed the 1% impact-probability threshold; two days later, the International Asteroid Warning Network sent its first-ever formal asteroid warning to the UN’s space office—activating a planetary-defence protocol created more than a decade earlier but never previously used.
Asteroid 2024 YR4 did not hit Earth, and it will not do so in 2032. Its importance lies…