Near-Earth Objects

Near-Earth Objects (NEOs) are celestial bodies, primarily asteroids and comets, that have orbits that bring them close to Earth. Specifically, NEOs are defined as any small solar system body whose orbit brings it within 1.3 astronomical units (AU) of the Sun, which is roughly equivalent to the distance from Earth to the Sun (1 AU is about 93 million miles or 150 million kilometers).

NEOs are categorized into two main groups:

1. **Near-Earth Asteroids (NEAs)** – These are further divided into subcategories depending on their specific orbital characteristics. The most notable of these are Atira (or Apohele) asteroids, which orbit entirely within Earth’s orbit, and Apollos and Amors, which have orbits that cross or approach Earth’s orbit, respectively.

2. **Near-Earth Comets** – These comets have orbits that also bring them close to Earth, although they are less prevalent than asteroids.

The study of NEOs is significant for planetary defense, as some of these objects can pose a collision risk with Earth. Monitoring and characterizing NEOs help scientists assess their trajectories and the potential threat they may pose in the future.