Our Solar System _______________________________________________________________________________________________________________________________________________________________________________________________________________________
4. Outer Solar System
The Oort Cloud. The Oort Cloud is the most distant region of our solar system. Unlike the orbits of the planets and the Kuiper Belt, which lie mostly in the same flat disk around the Sun, the Oort Cloud is believed to be a giant spherical shell surrounding the rest of the solar system. It is like a big, thick-walled bubble made of icy pieces of space debris the sizes of mountains and sometimes larger. The Oort Cloud might contain billions, or even trillions, of objects.
Because the orbits of long-period comets are so extremely long, scientists suspect that the Oort Cloud is the source of most of those comets.
Except for the Sun, no object in the Solar System emits its own light.
This video looks at the characteristics of the outer planets, dwarf planets, moons and comets.