Small Bodies of the Solar System
The small bodies in the solar system include comets, asteroids, the objects in the Kuiper Belt and the Oort cloud, small planetary satellites, Triton, Pluto, Charon, and interplanetary dust. As some of these objects are believed to be minimally altered from their state in the young solar nebula from which the planets formed, they may provide insight into planet Earth and the formation and evolution of the solar system.
Pluto resides in the Kuiper Belt. With an orbit inclined to the plane of the solar system, Pluto most likely evolved away from the sun’s flattened disk where the larger bodies (or planets) formed. Pluto’s orbit crosses inside that of Neptune’s rendering Pluto also a member of the Trans-Neptunian Object (TNO) class. The Pluto system is very exotic, having three moons including Charon discovered in 1978, and Nix and Hydra discovered in 2005.
Asteroids are rocky remnants from the formation of the solar system. They are not spherical and have differing compositions and histories. Most, although not all asteroids, reside in a region between Mars and Jupiter where numerous other small rocky worlds orbit the sun. Some asteroids belong to groups that came from larger parent bodies which were shattered in past collisions with other asteroids. Some are in orbits that cross paths with that of Earth’s or other planets. Asteroids that cross Earth’s orbit are called Potentially Hazardous Asteroids (PHA) and the more we observe the heavens, the more of them we find, some of which are seen for the first time just after passing close to Earth.