Changes

==== Oort cloud ====

==== Oort cloud ====

: ''Main article: [[Oort Cloud]]''

: ''Main article: [[Oort Cloud]]''

Most conventional [[astronomy|astronomers]] invoke the [[nebula theory]] and state that comets are debris that failed to accrete into the [[planet]]s and [[moon]]s when the [[solar system]] formed.<ref name=Yeomans/><ref name=space/> The classic [[Oort Cloud]] theory states that the Oort cloud, a sphere measuring about 50,000 AU in radius, formed at the same time as the solar nebula and occasionally releases comets into the inner solar system as a star (possibly the reputed [[Nemesis]]) passes. Jewitt<ref name=Jewitt/> and others have proposed instead that comets initially formed near or immediately beyond the [[gas giant]] planets. Some of these objects persist as Kuiper belt objects. Others passed close enough to the gas giants to gain sufficient energy to launch them into high orbits, where they eventually formed the Oort cloud and, some suggest, continue to resupply it.

Most conventional [[astronomy|astronomers]] invoke the [[nebula theory]] and state that comets are debris that failed to accrete into the [[planet]]s and [[moon]]s when the [[solar system]] formed.<ref name=Yeomans/><ref name=space/> The classic [[Oort Cloud]] theory states that the Oort cloud, a sphere measuring about 50,000 AU in radius, formed at the same time as the solar nebula and occasionally releases comets into the inner solar system as a star (possibly the reputed [[Nemesis (Star)|Nemesis]]) passes. Jewitt<ref name=Jewitt/> and others have proposed instead that comets initially formed near or immediately beyond the [[gas giant]] planets. Some of these objects persist as Kuiper belt objects. Others passed close enough to the gas giants to gain sufficient energy to launch them into high orbits, where they eventually formed the Oort cloud and, some suggest, continue to resupply it.

==== Interstellar capture ====

==== Interstellar capture ====