Monday, November 30, 2015

The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA
Representation of the Oort Cloud in relation to the Solar System

What is the Oort Cloud?

     In an effort to explain the behavior of long term comets, Jan Oort hypothesized the existence of a cloud like region of space past the planets and the Kuiper Belt at the outer edges of our solar system. The Oort Cloud, as it came to be known, is believed to have originated from the protoplanetary disc at the same time the solar system was developing.

     The cloud has two regions. The inner region, called the Hills Cloud, is strongly bound to the Sun so it maintains a disc shape. This region begins two thousand to five thousand AU from the sun and extends to twenty thousand AU. The outer region has a spherical shape due to gravitational interaction with nearby stars. It lies from twenty thousand AU to as much as two hundred thousand AU. It could possibly contain trillions of objects larger than one kilometer. Scientists have used Haley’s Comet as a typical representation of Oort material and calculated that the outer cloud has a mass of five Earths.

     Both regions contain what scientists call Trans Neptunian Objects- comets and other icy materials. Based on research of past comets, it is believed to be comprised mostly icy volatiles such as water, methane, ethane, carbon monoxide, hydrogen cyanide, and ammonia. Research suggests that it also consists of one to two percent asteroids.


Williams, Matt. "What is the Oort Cloud".Universe Today. 2015. Web. 30 Nov 2015