Near-Earth Object (NEO)

A near-Earth object, commonly abbreviated NEO, is any asteroid or comet whose orbit around the Sun brings it within about 1.3 astronomical units of the Sun, close enough that its path can also bring it relatively near Earth's own orbit. NEOs are grouped into several dynamical families based on the details of their orbits, including Atens, Apollos, and Amors, and while the overwhelming majority pose no danger whatsoever, tracking them is a genuine, ongoing planetary safety effort. NASA and other space agencies around the world operate dedicated survey programs, including ground-based telescopes and space-based missions, specifically to discover, track, and calculate precise orbits for as many NEOs as possible, with a particular focus on finding larger objects capable of causing significant regional or global damage in the unlikely event of an impact. As of the mid-2020s, astronomers have cataloged tens of thousands of known NEOs, and that number continues to grow steadily as survey telescopes become more sensitive. Studying NEOs also matters scientifically beyond planetary defense: because many are relatively unweathered, primitive leftovers from the early solar system's formation, missions that have visited or even returned samples from NEOs, such as NASA's OSIRIS-REx mission to the asteroid Bennu, provide a direct window into the raw materials that built the planets over four and a half billion years ago.