The Oort Cloud
The Oort Cloud is a hypothesized spherical distribution of icy bodies surrounding the Solar System at great distances. It is proposed as a source region for long-period comets.
The Oort Cloud is discussed in planetary science, celestial mechanics, and models of solar system formation.
Status
The Oort Cloud has not been directly observed. Its existence and properties are inferred from the orbital characteristics of long-period comets, and its structure remains subject to theoretical modeling.