Difference between "planetary ring" and "circumstellar disk"? Related: Do/Can Ringed Stars Exist?


Is there any particular difference, in behavior or properties, between a planetary ring system and a circumstellar disk? Or is the only real difference a matter of what's in the middle?

This question came up as a matter in the related discussion, particularly because the (game-simulated) object that inspired the question is a brown dwarf - something between a star and a gas giant. What I observed in-game appeared to be more similar to the rings around Saturn, than to the description and image provided of a circumstellar disk.

So, are there properties of the rings/disks themselves which can differentiate one type from another? Or is the type of central body the only thing that defines them?

If the central body is the only factor, what should we call a ring around a brown dwarf, assuming one could exist in nature?
From Physics SE:


  A circumstellar disk is a set of objects that orbit about a star-like object and that collectively look disk-like in some way.


From Wikipedia:


  A ring system is a disc or ring orbiting an astronomical object that is composed of solid material


So, a circumstellar disk may have gas, dust, asteroids, etc., but it must orbit a star-like object. A ring system must have something solid--dust or moonlets--but it may orbit any astronomical object.

Other than that, you specifically asked about a planetary ring. That would mean a ring system that specifically had a planemo as the central body.

In other words, a disk around a brown dwarf could be described as a circumstellar disk (a brown dwarf is a star-like object) or a ring system (as long as the disk contained solid material). It could not be called a planetary ring, because a brown dwarf is not a planet.