Beyond the Kuiper Belt lies the Oort Cloud. The Oort Cloud is a hypothesis (a scientific guess) first theorized (an idea brought to the scientific community, but has yet to be proven) by John Oort. This is a region of icy objects, and the remains of the materials used to form the Sun and Planets. As the Planets grew, especially Jupiter, its thought that these objects, once much closer to the Sun were pushed out to where they are now.

Facts from Space.com

Objects in the Oort Cloud are also referred to as Trans-Neptunian objects. This name also applies to objects in the Kuiper Belt.
Some astronomers theorise that the Sun may have captured Oort Cloud cometary material from the outer disks of other stars that were forming in the same nebula as our star.
The Oort Cloud is a reserve of cometary nuclei that contain ices dating back to the origin of the solar system.
No one knows for sure how many objects exist in the Oort Cloud, but most estimates put it at around 2 trillion.
The planetoid Sedna, discovered in 2003, is thought to be a member of the inner Oort Cloud.
Astronomers think that long-period comets (those with orbital periods longer than 200 years) have their origins in the Oort Cloud.

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