Oort Cloud

oort cloud
Image from Steve Bowers

A spherical shell around most stars containing numerous small bodies. A typical Oort cloud is about 0.5 to 1 light years from its primary and has an aggregate mass about that of Earth; density is thus extremely low. The main constituents of cometary bodies are ice and dust ("dirty snowballs"). Bodies in the Oort cloud are occasionally perturbed by collisions or by the influence of nearby stars into orbits which pass near the star; these form long-term comets. The Oort cloud is named after its discoverer, Old Earth presingularity astronomer Jan Oort.

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Development Notes
Text by M. Alan Kazlev
Initially published on 17 December 2001.