How did bodies in the Kuiper belt and the Oort cloude form?

Question

How did bodies in the Kuiper belt and the Oort cloude form?

Answer 1

http://en.wikipedia.org/wiki/Kuiper_belt...

http://en.wikipedia.org/wiki/Oort_cloud#...

Answer 2

They're leftovers from the formation of the planets.

The outer planets formed from chunks of rock and ice (planetesimals) in the solar nebula. However, their immense gravity has scattered the leftover chunks far and wide in the 4.5 billion years since then - and they still exist in an enormous "cloud" surrounding the planets, the Oort Cloud.

The Kuiper Belt formed from material beyond Neptune's orbit that was too spread out and moving too slowly to collide and form large planets. It's thought that the Kuiper Belt and the Oort Cloud are the only places in the solar system where pure, pristine objects left over from the beginning still exist in their original form, so a mission to the outer reaches of the Solar System would probably be very useful to astrophysicists studying its formation.