Oort Cloud is highly theoretical with no solid data to support it. Some adherents claim it extends out as far as 2 light years, or almost half way to the closest star, Alpha Centuari. Seems like a stretch. Hard to imagine all that material so far away locked around our puny yellow dwarf. Long period comets likely come from the Kuiper Belt, a well documented region beyond Neptune that is loaded with icy bodies. Hale-Bopp has estimated period of 2500 years, making it the longest period of any comet to date. That doesn't mean it came from Oort Cloud since its period could have been increased by sling shot from the Sun, or Jupiter, etc. Long period comets represent the greatest threat to earth, after humans. Since they are only discovered a few months before passing through the inner solar system, what to do, what to do? However, humans are killing everything off right now, the next mass extinction from space may not be so dramatic.Won't have much to kill off after we are done.......
Presumably there is a large gap between the Kuiper belt and the Oort cloud, with the latter starting at around 0.03 and 0.08 light years, and extending out to as far as several light years depending on predictions. Its presence was postulated by Jan Oort who saw a need to explain where long period comets came from since they would never have formed in their highly elliptical orbits around the sun, but must have formed well beyond the solar radiation which eats them away. Dingbone brings up the important aspect of larger bodies in the Kuiper Belt, which is well established and may very well harbor a planet 9, much larger than Pluto. This could easily explain the origin of long period comets, with these large bodies perturbing icy chunks to rain down into the inner solar system. As a large chunk approaches the Sun, its velocity would increase dramatically and then if it survives without impacting, could get thrown out a great distance, resulting in long period comets. Sling-shotting.
dfjohnsonphd
Jul 25, 2017