Oort cloud
theoretical cloud of planetesimals at the far edge of the solar system / From Wikipedia, the free encyclopedia
The Oort cloud, or Öpik–Oort cloud,[1] is a cloud of comets and other objects. Astronomers believe it is way beyond the orbits of Pluto and the Kuiper belt. The Oort cloud is believed to be the source of long-period comets in the Solar System.[2]
The Oort cloud may lie about 50,000 AU, or nearly a light-year, from the Sun.[3] This means the cloud is nearly a quarter of the way to Proxima Centauri, the nearest star to the Sun.
The Kuiper belt and scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one-thousandth of the Oort cloud's distance. The outer limit of the Oort cloud defines the boundary of the Solar System and the region of the Sun's gravitational dominance.[4]
The Dutch astronomer Jan Hendrik Oort published the Oort cloud idea in 1950. The Oort cloud was named after him, as were the Oort comet, and Oort constants.[5]