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The Oort cloud is thought to have developed after the formation of planets from the primordial protoplanetary disc approximately 4.6 billion years ago. [4] The most widely accepted hypothesis is that the Oort cloud's objects initially coalesced much closer to the Sun as part of the same process that formed the planets and minor planets.
The Oort cloud (/ ɔːr t, ʊər t /), sometimes called the Öpik–Oort cloud, is theorized to be a vast cloud of icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years). The concept of such a cloud was proposed in 1950 by the Dutch astronomer Jan Oort, in whose honor the
Artist's rendering of the Kuiper belt and Oort cloud. Freeman Dyson proposed that trans-Neptunian objects, rather than planets, are the major potential habitat of life in space. [citation needed] Several hundred billion to trillion comet-like ice-rich bodies exist outside the orbit of Neptune, in the Kuiper belt and Inner and Outer Oort cloud.
The objects within the Kuiper belt, together with the members of the scattered disc and any potential Hills cloud or Oort cloud objects, are collectively referred to as trans-Neptunian objects (TNOs). [42] Two TNOs have been visited and studied at close range, Pluto and 486958 Arrokoth.
The Oort cloud (artist's rendering pictured) is a hypothesized spherical cloud of comets that may lie nearly a light-year from the Sun. It is thought to comprise two separate regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud; the outer extent of the cloud defines the boundary of the Solar System.
Numerous such comets have been observed when close to the Sun. The closer an object is to the Sun the faster it needs to move to maintain the orbit. Objects move slowest when furthest from the Sun (aphelion) and fastest when closest to the Sun (perihelion) and this is why Oort cloud comets spend most of their time in the Oort cloud.
Description 134340 Pluto: A dwarf planet, the first and largest trans-Neptunian object (TNO) discovered. It is the only TNO known to have an atmosphere. Hosts a system of five satellites and is the prototype plutino. 15760 Albion: The prototype classical Kuiper belt object (KBO), the first TNO discovered after Pluto (385185) 1993 RO
The classic Oort cloud theory states that the Oort cloud, a sphere measuring about 50,000 AU (0.24 pc) in radius, formed at the same time as the solar nebula and occasionally releases comets into the inner Solar System as a giant planet or star passes nearby and causes gravitational disruptions. [44]