Near-Earth Asteroids (NEAs) are asteroids whose orbits bring them into close proximity to Earth. They are defined as having a perihelion distance (closest point to the Sun) of less than 1.3 astronomical units (AU). These objects are of significant interest due to the potential hazard they pose to Earth, as well as their scientific value in understanding the formation of the solar system.
The systematic search for NEAs began in the late 20th century with projects like the Spacewatch and LINEAR. NASA's Near-Earth Object Program and the European Space Agency's Space Situational Awareness program are key initiatives in tracking these objects. The Arecibo Observatory and Goldstone Deep Space Communications Complex have been pivotal in radar observations of NEAs.
NEAs are monitored for potential impacts with Earth. The Torino Scale is used to categorize the impact risk of an asteroid. To date, no asteroid has been assigned a level higher than 1 on this scale, indicating a low probability of collision. However, the Chelyabinsk meteor event in 2013 highlighted the potential threat from smaller, undiscovered objects.
Research into deflecting or disrupting potentially hazardous NEAs includes:
NEAs provide insights into the early solar system. Missions like Hayabusa and OSIRIS-REx have returned samples from these bodies, offering direct study of their composition.