Colonization of trans-Neptunian objects Reference Libraries

Oort Cloud -- The Oort cloud is a postulated cloud of comets situated about 50,000 to 100,000 AU from the sun. Although no direct observations have been made of such a cloud, it is believed to be the source of most or all comets entering the inner solar system (some short-period comets may come from the Kuiper belt), based on observations of the orbits of comets. The Oort cloud was...