Minor Planet Designations

Near-Earth Asteroids/Objects (NEA/Os) Atiras aphelion and perihelion distances are less than Earth's perihelion distance (they spend all of their time inside Earth’s orbit). Atens have a semi-major axis of less than AU and aphelion greater than Earth’s perihelion distance (they spend most of their time inside Earth’s orbit). Apollos have semi-major axis greater than 1 AU and perihelion less than the Earth’s aphelion distance (they spend most of their time outside of Earth's orbit). Amors (Spend all of their time outside of Earth's orbit). Mid Solar System Asteroids Mars-crossers cross the orbit of Mars. Asteroids with a perihelion less than 1.3 AU are often classed as near-Earth objects, even if they cross the orbit of Mars as well as crossing (or coming near to) that of Earth. A grazer is an object with a perihelion below the aphelion of Mars (1.67 AU) but above the Martian perihelion (1.38 AU). Hungaria asteroids have a semi-major axis between 1.78 and 2.00 AU (they are the innermost dense concentration of asteroids in the Solar System). Main Belt asteroids occupy the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. About half the mass of the belt is contained in the four largest asteroids, the three intact protoplanets Ceres, Vesta, and Pallas, and Hygiea. Vesta, Pallas, and Hygiea have mean diameters of more than 400 km, whereas Ceres, the asteroid belt's only dwarf planet, is about 950 km in diameter. Hilda asteroids are in a 3:2 orbital resonance with Jupiter. Hildas move in their elliptical orbits so that their aphelia put them opposite Jupiter, or 60 degrees ahead of or behind Jupiter at the L4 and L5 Lagrangian points. Over three successive orbits each Hilda asteroid passes through all of these three points in sequence. Trojan asteroids also orbit in the 4th and 5th Lagrange points of other major planets in the Solar System. Currently there are five planets known to have trojans: • Earth trojans (1) • Mars trojans (7) • Jupiter trojans (6000+) • Uranus trojans (1) • Neptune trojans (13) Distant Asteroids Centaurs are asterroids that orbit between Jupiter and Neptune Edgeworth-Kuiper Belt Objects (EKBOs)/Trans-Neptunian Objects (TNOs) are very distant objects, classified as: • Plutinos • Plutoids • Classical EKBOs • Scattered Disk Objects (SDOs) • Detached Objects