Terminology

 

Units of Measurement

au - Astronomical Units. Approximately the average distance between the earth and the sun

aphelion distance - distance between an object’s orbit point farthest from the sun

perihilion distance - distance between an object’s orbit point closest to the sun

semi-major axes - an object’s mean distance from the sun

Abbreviations

NEO - Near Earth Object. Asteroids or comets with a perihelion distance less than or equal to 1.3 astronomical units

NEA - Near Earth Asteroid

NEC - Near Earth Comet

PHA Potentially Hazardous Asteroids. Asteroids with the potential to make close approaches to earth. PHAs are classified based on their minimum orbit intersection distance and absolute magnitude.

Earth, Moon, and Asteroid Bennu

Picture of the earth and moon (bottom left) and Asteroid Bennu (top right). Asteroid Bennu is a main-belt asteroid whose orbit is between Mars and Jupiter.

NEA classifications

Amor - An asteroid whose orbit is outside of Earth’s orbit (but within Mars’). Named after asteroid 1221 Amor.

Apollo - An asteroid whose orbit crosses earth’s orbit and whose average distance from the sun is larger than Earth’s. Named after asteroid 1862 Apollo.

Aten - An asteroid whose orbit crosses earth’s orbit and whose average distance from the sun is smaller than Earth’s. Named after asteroid 2062 Aten.

Atira - Also known as an Interior-Earth Asteroid (IEA). An asteroid whose orbit is within the earth’s orbit. Named after asteroid 163693 Atira

See also: