Why do comets leave the Oort Cloud? Some of the comets that inhabit the Oort cloud, can, from time to time, fall into the inner solar system and come under the gravitational control of the planets, becoming long period comets. read more
They are thought to originate in the Oort cloud. The Oort cloud has never been observed, but is believed to have at least 1012 icy objects located between 3000 AU and 100,000 AU in a spherical distribution around the Sun. read more