2024 YR4

2024 YR₄ is an asteroid with an estimated diameter of 53 to 67 metres (174 to 220 ft) that is classified as an Apollo-type (Earth-crossing) near-Earth object. From 27 January to 20 February 2025, it had an impact rating of 3 on the Torino scale, reflecting its size and an estimated probability greater than 1% that it would impact Earth on 22 December 2032. The estimated impact probability peaked at 3.1% on 18 February 2025. By 23 February, additional observations effectively ruled out 2024 YR₄ impacting Earth in 2032 and lowered its Torino rating to 0. Based on the James Webb Space Telescope observation on 11 May 2025, there is a roughly 4% chance of impacting the Moon on 22 December 2032 around 15:19 UTC, and the asteroid is expected to pass 9000±74000 km from the surface of the Moon.

The asteroid was discovered by the Chilean station of the Asteroid Terrestrial-impact Last Alert System (ATLAS) at Río Hurtado on 27 December 2024. When additional observations increased its impact probability to greater than 1%, the first step in planetary defense responses was triggered, prompting additional data gathering using several major telescopes and leading United Nations–endorsed space agencies to begin planning asteroid threat mitigation.

The asteroid made a close approach to Earth at a distance of 828,800 kilometres (515,000 miles; 2.156 lunar distances) on 25 December 2024, two days before its discovery, and it will be moving away from the Sun until November 2026. Its next close approach will take place on 17 December 2028. Analysis of spectral and photometric time series suggests that 2024 YR₄ is a stony S-type (most likely), L-type or K-type asteroid, with a rotation period of approximately 19.5 minutes. A number of known asteroids, including other virtual impactors, follow orbits somewhat consistent with that of 2024 YR₄.