An Etymological Dictionary of Astronomy and Astrophysics

A member of a class of → near-Earth asteroids (NEAs) that have orbital → semi-major axes greater than that of the Earth (> 1 → astronomical unit) but → perihelion distances less than the Earth’s → aphelion distance (less than 1.017 AU); thus, they cross the Earth’s orbit when near the perihelia of their orbits. They are named for the prototype Apollo.

See also: → Apollo; → asteroid.