2024 YR4 is an asteroid between 40 and 100 metres (130 and 330 ft) in diameter, classified as an Apollo-type (Earth-crossing) near-Earth object. It was discovered by the Chilean station of the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 27 December 2024. As of 5 February 2025, 2024 YR4 was rated 3 on the Torino scale with a 1 in 53 (1.9%) chance of impacting Earth on 22 December 2032. NASA gives a Palermo Technical Impact Hazard Scale rating of −0.40 for 2024 YR4, which corresponds to an impact hazard of 39.8% of the background hazard level. The discovery has triggered the first step in planetary defense responses, in which all available telescopes are asked to gather data about the object and United Nations-endorsed space agencies are prompted to begin planning for asteroid threat mitigation.
Preliminary analysis of spectra and photometric timeseries of this asteroid suggests it is a stony S-type or L-type asteroid with a rotation period near 19.5 minutes. The asteroid previously made a...