 Since its discovery, the number of known KBOs has increased to thousands, and more than 100,000 KBOs over in diameter are thought to exist.The Kuiper belt was initially thought to be the main repository for periodic comets, those with orbits lasting less than 200 years.Studies since the mid-1990s have shown that the belt is dynamically stable and that comets' true place of origin is the scattered disc, a dynamically active zone created by the outward motion of Neptune 4.5 billion years ago; scattered disc objects such as Eris have extremely eccentric orbits that take them as far as 100 AU from the Sun.