# Multi ringed planetary bodies in a binary star system.

Just watched the Sci-Fi Horror movie “Pitch Black” last night. Aside from a number of minor flubs and gaffs the movie was pretty hood horror/action fare. The only real issue I had with the movie was one of physics.

In the movie there is a really spectacular scene of a binary eclipse (they actually did a pretty good job of that and the physics of a binary system with regular orbits is too tricky for me to even know if they got that wrong) where you see a saturn-like planet crash the horizon is great detail.

The problem was that the Saturn-like planet has a greater and lesser band on two planes. One equatorial and one I’ll estimate at equater plus 20 minutes. The equatorial band was the greater band. Now from all I can remember the only way to have multiple bands on a planet is if the planet is a dubmell shaped planet and it couldn’t be a super jovian as was depicted in the movie.

Of lesser note, the Saturn-like planet intersected the path of a lesser planet (thus making the eclipse possible), which I thought was impossible but may have been a function if a binary system.

Also of lesser note and possible a visual gaff was that the rings were counter-rotating. Odd?

Anyhow, you big brain types may be able to figure this out as I am unable to do so. I have had mainly a hobbyists interests in planetary geometry and physics.
zen101
D.F.A.

[Moderator Hat: ON]

This appears to be a question. It’s certainly not a debate. So off to General Questions it goes.

David B, SDMB Great Debates Moderator

[Moderator Hat: OFF]

I’m not sure I fully understand your description but here are my 2 cents.

As far as I know (AFAIK), there are no known planets with rings on more than one plane, so we have no examples to go by. I don’t know about the physics of this, but it seems that such as system would not be stable (gravity and “friction” would eventually bring these rings together along the equatorial region of the planet…but maybe the ring was newly formed).

AFAIK, there are no known dumbell-shaped planets (besides an asteroid, which is only a “minor planet”). Is this even possible for a large planet? Seems like gravity would bring them together.

The eclipsing planet would just have to be in-between the viewing planet and the two suns. This may be possible if the 2 stars were close together & the orbits of the planets were far enough away. But again, AFAIK, we don’t know of any binary star systems with planets. And the physics/mathematics of binary star solar systems has got to be complex.

re: counter-rotating - - yes, this would be odd, but perhaps not impossible. Assuming rings form from former moons that were obliterated from a collision, most moons orbit in the direction of the planet’s rotation. But there are exceptions such as Triton (Neptune) which orbits in the opposite direction. The formation of rings is still an area of research. If the rings formed from the proto-planetary disk, then they should orbit in the direction of the planet’s rotation.

I think we need some more mathematical/physics insight here. Plus I need to see the movie!

Thank you for moving this thread. I accidentally posted it in the GD forum.

This is what I get for trying to work when I should be paying attention to the truly important part of my day. My posting on the SDMB.

zen101
D.F.A.

It’s possible (though unlikely) for a planet to have rings in multiple planes, but all of those planes must pass through the center of the planet, so parallel ring planes are out of the picture. Or did you mean surface bands? You can have as many of those parallel as you want, and they’re pretty common on gas giant planets.

As for a gas giant eclipsing a rocky planet, it’s not possible in our solar system, from the viewpoint of Earth, since all of the rocky planets are interior to the gas giants, but as evidenced by all of the extrasolar planets discovered, it is possible to have a gas giant close to its primary.

It is possible to have stable planetary orbits in a binary system, but it’s very difficult. Having never seen the movie, I don’t even know if they went into enough detail to determine if their scenario is possible.

Chronos:

It was two external and paralell rings counter-rotating and only one was at the equator. The other was north by quite a distance and in a tighter orbit. Made a pretty, if confusing, picture. Just imagine standing in a rocky desert in a binary system on a planet roughly Earth sized and the two suns line up and quite quickly (much tighter orbit so it moved really fast) a super Jovian crashed your horizon hiding your sun(s).
zen101
D.F.A.

So the plane of the ring does not reach the center of the planet? That’s pretty bad. A ring is just particles in orbit. An orbit is always elliptical, and the parent body must be at one of its two foci. In other words, the plane of the orbit (ring) must go through the center of the planet.

The only exception is the USS Enterprise which apparently is capable of a synchronous orbit above the northern hemisphere. (OK if they kept the engines running it’s possible to stay there, but that’s not an orbit.)