A near-Earth object is not a type of celestial body.
 Short-period comets, with an orbital period of less than 200 years, originate in the Kuiper belt, beyond the orbit of Neptune; while long-period comets originate in the Oort Cloud, in the outer reaches of the Solar System
 Comet nuclei are typically less dense than asteroids but they pass Earth at higher relative speeds, thus the impact energy of a comet nucleus is slightly larger than that of a similar-sized asteroid

