The Hills Cloud is the disc-shaped inner component of the Oort Cloud, a denser region of icy planetesimals extending from about 250 to 2,000 AU from the Sun. It serves as a transitional zone between the scattered disc and the outer spherical Oort Cloud, with objects less perturbed by galactic tides.
This region is thought to be a source of some long-period comets.
Named after astronomer Jack G. Hills, who proposed it in 1981 to explain comet distributions beyond the classical Oort Cloud.
Significant events include theoretical modeling in the 1980s and indirect observations through comets like Hale-Bopp, believed to originate here. Studies by NASA's Voyager missions and models continue to refine its boundaries and role in solar system dynamics.
