Oort Cloud Colonisation.
1.0 Introduction
The Oort Cloud's existence can generally be inferred from models of the Solar System's formation and evolution, and from the projected trajectories of several hundred long-period comets. The fact that comets appear with a regular frequency that has not changed significantly since observations began, indicates that there must be a source of them that lies well beyond the Kuiper Belt, whose outer edge lies some 50 AU from the Sun. Even though the majority of comets may originate in the inner Oort Cloud (or Hills Cloud), the fact that the inclination of the trajectories of long period comets with respect to the ecliptic, is uniformly distributed, indicates a more distinct source that is spherical rather than toroidal.
An important point here is that no comet has ever been observed whose trajectory would indicate an origin completely external to the Solar System. Even comets observed to be travelling fast enough to let them escape the Solar System after passing close to the Sun, have only have a slightly hyperbolic motion, which indicates a distant origin that is nonetheless still within the Sun's sphere of influence. Estimates of the average aphelion of long period comets and the fact that their trajectories appear to be omni-directional suggests that the outer Oort Cloud is a hollow spherical distribution of comet like bodies with its main concentration extending out to about 50,000 AU (about 0.8 light years) from the centre of the Solar System.
The inner edge of the outer Oort Cloud probably starts at about 20,000 AU and the outer edge may be over 100,000 AU, although after about 50,000 AU the relative number of objects in any region may decline rapidly. The outer Oort Cloud is the last of the general class of Trans-Neptunian regions that begins with the Kuiper belt, a torus shaped distribution of objects that is thought to extend from roughly 30 to 50 AU with a mean inclination of about 2 degrees from the ecliptic plane. The details of many Kuiper belt objects have been determined by observation. Beyond that lies the Scattered Disk region, thought to consist of perturbed comets whose orbits are unstable. It is currently estimated by some astronomers to extend out to 2000 AU with many of its members at a high angle of inclination to the ecliptic plane. Beyond or overlapping with the Scattered Disk there may be a torus shaped inner Oort Cloud that extends out to 20,000 AU, and which has a considerably higher density of objects than the outer Oort Cloud proper.
If the main concentration of outer Oort Cloud objects extends out to around 50,000 AU, this could prove to be a very interesting location in which to place large colonies. There may still be sufficient resources there to facilitate the construction and maintenance of large colonies and these could act as a hub for the exploration of even more distant regions, including first attempts at interstellar travel. The focus of this article will then be the development of substantial colonies at around 50,000 AU from the Sun.
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Abstract
1.0 Introduction
2.0 Travel
