Near-Earth object

Potentially Hazardous Asteroids 2013

PIA17041-Orbits-PotentiallyHazardousAsteroids-Early2013

PSM V76 D020 Path of halley comet

Eros - PIA02923 (color)

Objects between earth and moon

Sar2667 as it entered Earth's atmosphere over the north of France

Near-Earth object (NEO) refers to any small Solar System body whose orbit brings it into proximity with Earth. By definition, a near-Earth object's perihelion (closest approach to the Sun) is less than 1.3 astronomical units (AU) away from the Sun. These objects include asteroids, comets, and large meteoroids that are in the vicinity of Earth's orbit. The study of NEOs is significant due to their potential impact threat to Earth, offering insights into the early Solar System, and for the future potential of asteroid mining.

Classification

NEOs are classified into several groups based on their orbits:

• Aten asteroids: These have a semi-major axis of less than 1 AU and an aphelion distance greater than 0.983 AU.
• Apollo asteroids: Characterized by their semi-major axis being greater than 1 AU but perihelion distances less than 1.017 AU, crossing Earth's orbit.
• Amor asteroids: These asteroids have orbits that are close to Earth's but do not cross it, with perihelion distances between 1.017 and 1.3 AU.
• Atira asteroids: Also known as Apohele asteroids, they have orbits entirely within Earth's orbit with an aphelion distance less than 1 AU.

Discovery and Tracking

The discovery of NEOs is primarily conducted through ground-based telescopes, with several automated survey programs, such as the Catalina Sky Survey and the Pan-STARRS, playing significant roles. Space-based telescopes, like the NEOWISE mission, also contribute to detecting and characterizing these objects. Once discovered, NEOs are tracked to determine their orbits, size, composition, and potential threat to Earth.

Impact Hazard

The potential impact of an NEO with Earth is a subject of significant concern. Even small NEOs can cause significant damage, as evidenced by the Chelyabinsk meteor event in 2013. Various agencies, including NASA's Planetary Defense Coordination Office and the European Space Agency's Space Situational Awareness Programme, are involved in identifying potentially hazardous asteroids (PHAs) and developing mitigation strategies. These strategies may include deflection tactics, such as the kinetic impactor technique, or disruption methods.

Exploration and Utilization

NEOs are of interest not only for the threat they pose but also for their scientific value and potential resources. Missions such as NASA's OSIRIS-REx and Japan's Hayabusa2 have aimed to return samples from NEOs to Earth for analysis. These missions provide invaluable insights into the composition of NEOs, offering clues about the early Solar System and the origins of water and organic compounds on Earth.

Furthermore, NEOs are considered potential targets for future asteroid mining endeavors, offering access to valuable resources such as water, precious metals, and other materials essential for in-space manufacturing and supporting deep-space exploration missions.

See Also

• Asteroid belt
• Comet
• Meteoroid
• Planetary defense