# Is a Procyon - brown dwarf - Jupiter - superearth - Mars - Pluto system theoretically possible? [closed]

I once conducted a thought experiment and with some amateurish calculations based around Hill sphere and Roche limit came up with semi-major axis distances like this:

Procyon-BD:  3.6 AU
BD-Jupiter:  0.7 AU
Jupiter-SE:  0.12 AU
SE-Mars:     0.02 AU
Mars-Pluto:  0.0033 AU


Assuming respective masses of: 496 260 earths, 15 000 earths, 313 earths, 6 earths, 0.107 earths and 0.00218 earths.

Clarification: I use names of specific bodies (Procyon, Jupiter etc) but a Procyon-like star, a Jupiter-like gas giant and so on would be more precise. Think of them only as examples of bodies with such masses.

Could such a system be possible?

• You want a system with those exact distances or a system with just those bodies present? Should they all orbit the central object (thus Procyon) or should each orbit the next bigger object? The latter would certainly not work stably. A system would also be considered bound when the orbits are outside the bigger object's hill sphere. Commented May 10, 2020 at 14:44
• A brown dwarf orbits a Procyon-like star in the center, a Jupter-like gas giant orbits a brown dwarf, a superearth orbits a gas giant, a Mars-like planet orbits a superearth and a Pluto-like planet orbits a mars planet. So it wouldn't be stable? Why?
– z33k
Commented May 10, 2020 at 15:01
• For information, I have raised a question on Meta about the on-topicness of "solve my n-body system"-type questions.
– user24157
Commented May 10, 2020 at 16:18
• Are you just asking about the orbit stability of such a system? Or are you (also) asking if it's theoretically possible for such a system to form naturally? (My guess is that it's not stable, and that it couldn't form). Commented May 11, 2020 at 0:33
• I’m voting to close this question because it is getting into off-topic territory. The general question about the feasibility of subsatellites has already been asked, the question about details of a specific hypothetical system are more suited for Worldbuilding.
– user24157
Commented May 18, 2020 at 17:32

Thanks to this answer linked by antispinwards I learned that such system most probably would not be stable, as I calculated it with proximity to upper limit of Hill sphere for each body.

But, if instead, I would have taken distances closer to 1/3-1/2 Hill sphere, it could be theoretically feasible.

The orbit of a satellite's satellite will be stable if it's deep enough inside the Hill sphere, within the so-called true region of stability. The limits are a bit fuzzy, but the true region of stability is typically the lower 1/3 to 1/2 of the Hill sphere.

On a personal note, if it's so, it surprises me this type of systems are not more pondered on and discussed, with maybe even some probabilities calculated. As it could have a great impact on thinking about abundance of potentially habitable worlds in the universe (imagine how great a number of earth-like satellites could live in such a system in the habitable zone of its host star (it being short-lived on cosmological time-scale notwithstanding)).

• Probabilities of systems are calculated - from disk evolution models. Not by a-priori assumptions of what they should look like. A system like the one described here is not a likely solution by a huge margin of any reasonable models based on physical models Commented May 19, 2020 at 11:01
• Is how reasonable these models are measured against vastness of space and multitude of systems? I know the chance is small, but faced with enormity of space, is it orders of magnitude too small?
– z33k
Commented May 19, 2020 at 12:22
• IMHO yes. Maybe not as unlikely as a stone jumping up and the room getting cooler, but it goes in that direction. It get's very difficult to reason wrt how planets form in a disk around a star - and it needs all the matter to form such planet within a larger portion of the disk. Given that, there never is enough material for another planet where another forms, or they would eventually collide - especially not given your cascade. The existing bigger moons generally are what roughly can form within the hill sphere, given available material, formed due to catastrophic collision or were captured. Commented May 19, 2020 at 12:58