Oort Cloud The Oort Cloud is a large spherical cloud with a radius from 50,000 to 100,000 A.U. surrounding the Sun filled with billions to trillions of comets. It has not been directly observed. Its existence has been inferred from observations of long period comets . Long period comets have very elliptical orbits and come into the inner solar system from all different random angles (not just along ecliptic). Kepler's third law says that they have orbital periods of 100,000's to millions of years. However, their orbits are so elliptical that they spend only 2 to 4 years in the inner part of the solar system where the planets are and most of their time at 50,000 to 100,000 A.U. With such long orbital periods their presence in the inner solar system is, for all practical purposes, a one-time event. Yet we discover several long period comets every year. This implies the existence of a large reservoir of comets. This was first noted by the Dutch astronomer Jan Oort in 1950 so the spherical comet reservoir was named after him. If Halley's Comet's mass is
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This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.