Comets are a small body of various ices, rock, and dust. They can be a few hundred meters to tens of kilometers. If it gets warm enough, the ice melts into an atmosphere called a coma, while the rock is the nucleus. The atmosphere can form a tail.

Meteors are commonly called shooting stars. They are small objects entering the atmosphere and heated up by friction. Meteoroids are what cause meteors. A meteorite is what hits the ground.

Asteroids are more than 100 meters across. They never get an atmosphere. Most are in the asteroid belt.

Dwarf planets have specific criteria. They must orbit the sun and be nearly spherical, but cannot have cleared the orbit of space debris. There are five dwarf planets: Pluto, Eris, Ceres, Haumea, and Make Make. They have nine total moons.