I Why hasn't the Oort cloud converged to a disk shape?

[jim mcnamara]

Marochnik has several papers dealing with the Oort cloud. I had seen references to them. Thanks for the clarification. But. It remains that the Oort cloud has non zero angular momentum. IMO.

 

[jim mcnamara]

https://www.sciencedirect.com/science/article/pii/001910359190097D
abstract:

Marochnik et al. (1988, Science 242, 547–550) estimated that the angular momentum of the Oort cloud is between 5 × 1052 and 2 × 1053 g cm2 sec-1, two to three orders of magnitude greater than the total angular momentum of the planetary system. However, most of the angular momentum in the present-day Oort cloud is the result of the action of external perturbers over the history of the solar system. In addition, some Oort cloud parameters used by Marochnik et al. tend to be higher than current best estimates. It is shown that the total angular momentum of the current Oort cloud is likely between 6.0 × 1050 and 1.1 × 1051 g cm2 sec-1, and the original angular momentum was likely a factor of 5 less than that.

Another non-zero estimate. Simply assuming zero angular momentum because the estimates are, well, fuzzy, is not logically justified. Why? All of the other objects [in however to define the limits of the solar system] have angular momentum. You could place an object like Deimos at 50,000 AU (one conservative estimate of the outer limits of the Oort Cloud.), then accelerate it. It would have a LOT of angular momentum. Move it out to 100K AU (another different estimate)
and even more angular momentum. I do not think that current technology would be able to "perceive" something like that. You may know. Which is why we get estimates that vary.

https://theplanets.org/deimos/

 

[alantheastronomer]

Yes, that lower estimate is from Weissman, but again, that's just a sum of individual values. No one's arguing that individual objects don't have non-zero angular momenta, or that the estimates are fuzzy and therefore don't exist; current observations don't seem to find any preferential direction for cometary orbits - there are just as many prograde orbits as retrograde. Which is why the Oort cloud hasn't settled into a disk, which is the question that began this thread. You're right, we can't observe comets out to the distance of the Oort cloud; they're much too dim. Estimates for their brightness put them at magnitude 60, while the brightness of the background sky is magnitude 27...

 

[Jonathan212]

So speaking generally about formations like the Oort cloud, the Kuiper belt, others that may exist elsewhere, or even smaller-scale ones like the rings of Saturn, why don't they all have zero total angular momentum?