Oort Cloud is a large spherical shell surrounding the Sun, planets and Kuiper Belt Objects. It is made of icy, comet-like objects that are as large as mountains or bigger. It is the most distant region in the Solar System.
A new research has estimated that the interstellar objects in the Oort Cloud outnumbers the objects belonging in the Solar System. This conclusion was made by studying Borisov the icy snowball that is the first and only interstellar object detected by humans. These objects are hard to detect as they are 200 billion to 100 trillion miles away from the Sun and do not produce their own light.