Palermo Technical Impact Hazard Scale

The Palermo Technical Impact Hazard Scale is a logarithmic scale used by astronomers to rate the potential hazard of impact of a near-Earth object (NEO). It combines two types of data—probability of impact and estimated kinetic yield—into a single "hazard" value. A rating of 0 means the hazard is equivalent to the background hazard (defined as the average risk posed by objects of the same size or larger over the years until the date of the potential impact).^[1] A rating of +2 would indicate the hazard is 100 times as great as a random background event. Scale values less than −2 reflect events for which there are no likely consequences, while Palermo Scale values between −2 and 0 indicate situations that merit careful monitoring. A similar but less complex scale is the Torino Scale, which is used for simpler descriptions in the non-scientific media.

As of May 2024,^[2] one asteroid has a cumulative Palermo Scale value above −2: 101955 Bennu (−1.41). Six have cumulative Palermo Scale values between −2 and −3: (29075) 1950 DA (−2.05), 2007 FT3 (−2.63), 1979 XB (−2.71), 2000 SG344 (−2.78), 2008 JL3 (−2.86), and 2010 RF12 (−2.98). Of those that have a cumulative Palermo Scale value between −3 and −4, one was discovered in 2024: 2024 BY15 (−3.30).