The potentially hazardous asteroid 2005 YU55 passes 0.85 lunar distances from Earth (about 324,600 kilometres or 201,700 miles), the closest known approach by an asteroid of its brightness since 2010 XC15 in 1976.

A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of impact. They are conventionally defined as having a minimum orbit intersection distance with Earth of less than 0.05 astronomical units and an absolute magnitude of 22 or brighter, the latter of which roughly corresponds to a size larger than 140 meters. More than 99% of the known potentially hazardous objects pose no impact threat over the next 100 years. As of February 2025, just 21 of the known potentially hazardous objects listed on the Sentry Risk Table could not be excluded as potential threats over the next hundred years. Over hundreds if not thousands of years, though, the orbits of some "potentially hazardous" asteroids can evolve to live up to their name.