How many orders of orbit are possible in the known universe?

So a star may orbit the galactic centre, that’s one.

If it’s in a binary system perhaps you could argue that two stars are orbiting each other - two. Debatable that one - I personally don’t think it should count but let’s go with it for now anyway.

Third (or second depending on your binary orbit philosophy) is a planet around the star or stars.

Fourth (or third) is a moon around the planet.

Presumably some moons have objects that get captured so that’s five (or four).

Is it possible that those bodies would be massive enough for there to be another order of orbit below that?

What might be the absolute limit before it becomes impossible? In both the real universe or theoretically?
Hope the question makes sense!

More than you think. Something as small as an asteroid can have a satellite in the right conditions.

Don’t globular clusters orbit their parent galaxies? If so, does that add a new level?

(Do the Magellanic Clouds “orbit” our galaxy? Have they had time to “go all the way around?”)

You should read about the Hill Sphere, which deals with your question.

That’s pretty cool, but since the asteroid is orbiting the sun it doesn’t add a level. If the astroid was captured by a moon could it retain its little satellite?

Ah wow. Thanks for this.

It’s 1am here so I don’t think my brain can handle that right now but I will be onto it tomorrow!

We put satellites in orbit around moons, so there’s that.

An earlier thread of mine:
http://boards.straightdope.com/sdmb/showthread.php?t=404162&highlight=moon

That’s uncertain. I’ve seen some speculation that they are not orbiting, but rather on an initial approach. The Milky Way is fragmenting them, which argues against them being in orbit.

Orbits around the Moon are not stable in the long run, or even intermediate run. Perturbations by the Sun and Earth, plus lumpiness in the Moon’s gravitational field make them unstable. With artificial satellites, we can adjust the orbit if it gets out-of-whack. There may be stable orbits around a satellite of a planet far away from the Sun, especially if the satellite is far away from its planet.