system
Given the following post, respond as if you're commenting on Reddit:
human
Why is there so much mystery shrouding the Oort Cloud? Do we know anything concrete about it's existence?

A quick google search shows there isn't much consensus on the topic and it seems as if we're not even sure it exists. Some articles talk about it with certainty while others vaguely mention there being controversy among experts.

What are the most up-to-date theories on the Oort Cloud and are there any interesting tidbits of information anyone can share?

Thanks!
gpt
You're right, in that it's still only a hypothesis - we can't observe it yet, since it's thought to be made up of billions of small, cold, and VERY diffuse objects with maybe a few dozen Earth masses' worth of material.  Turning the Hubble Space Telescope outwards and hoping to find an Oort cloud object, for example, would be like trying to see individual electrons in front of you with the naked eye.

Still, the main reason why the Oort cloud is often considered fact is that it's one of the most logical explanations for the existence of long-period comets like Hale-Bopp, since their orbits show that they must have originated from a region beyond the Kuiper belt.  On top of that, many computer models of the Solar System's formation predict that the gas and ice giants would have scattered an enormous amount of icy planetesimals outwards in the system's early, debris-rich days.  This would have ejected most of them from the system, but some would have just remained attached to the Sun and fallen into orbits thousands of times more distant than those of the modern Kuiper belt, scattered disc, and detached/Sednoid objects (assuming that "detached objects" like Sedna aren't actually the closest members of the inner Oort cloud).  Most of those objects would have been ejected from the Solar System, but a small fraction (still comprising a numerous population) would have remained gravitationally bound to the Sun in the form of the Oort cloud.

As for why long-period comets are so close relative to other Oort cloud objects, it's thought to be the result of their orbits being gravitationally perturbed by passing stars.