near-Earth object

A near-Earth object (NEO) is an asteroid or extinct short-period comet in an orbit that may bring it close to Earth. NEOs have perihelion distances of less than 1.3 astronomical units and include near-Earth asteroids belonging to the Apollo, Amor and Aten groups. Three NEOs – Ganymed, Eros, and Eric – have diameters greater than 10 km, while estimates suggest there may be at least 100,000 NEOs measuring 100 m or more across. Many of these will collide with the inner planets over the next 10 million yr or so.