The Oort Cloud is a spherical region enveloping the Sun where most comets with orbital periods exceeding several hundred years (i.e., “long-period comets”) originate. The dimensions of the Oort Cloud have never been measured, but it is estimated to be up to a trillion or more miles across. Scientists think that billions, perhaps even trillions, of comets and comet-like bodies are located in the Oort Cloud. Sedna may be the first Oort Cloud object ever discovered.