# Polar solar orbit possible?

1. Sep 16, 2016

### Noisy Rhysling

I need a planet to be orbiting it's sun in a polar orbit. Is this a stable configuration?

2. Sep 16, 2016

### rootone

It's unlikely that this could easily arise since a star and it's associated planets all form out of the same collapsing dust\gas cloud.
So the larger bodies which form tend to all inherit similar angular momentum.
I don't think there is anything which absolutely rules out that a planet might end up in a polar orbit of it's parent star.
In stellar systems having more than two large stars gravitationaly bound, it sounds plausible.
Then again, that setup might lead to chaotic planet orbits, although a planet might be in a polar orbit of one star for a while.

3. Sep 17, 2016

### Noisy Rhysling

Okay, "natural" is out, what about a captured planet? Would a planet who wanders into a system have a chance of achieving a stable polar solar orbit? This would be the only planet in the system, with very low junk around the star before the wanderer arrived.

4. Sep 17, 2016

### Bandersnatch

If it's the only planet, then how do you decide whether the orbit is polar or planar?

Rogue planet capture needs a third body to interact with, otherwise it'll just continue on a hyperbolic trajectory away from the system.

5. Sep 17, 2016

### Noisy Rhysling

Doesn't our sun rotate?

6. Sep 17, 2016

### Noisy Rhysling

Unless it doesn't have the relative velocity to escape the gravity well of the star, right?

7. Sep 17, 2016

### Bandersnatch

All right, if that's how you define planar, then polar orbits around a star are stable for most practical purposes. If there were any other massive bodies orbiting in the plane or solar rotation, then these would destabilise the polar orbit.

Consider that the planet comes from far away, from outside of gravitational influence of the star. As it falls into the gravity well it'll gain just as much velocity as it'll lose on the way out. I.e., if it was not bound to the star in the first place, then it won't become bound at all. Not without interaction with some third body.

8. Sep 17, 2016

### Noisy Rhysling

I don't know another way to define it. What have I missed/

I'm picturing the wanderer spiraling in to the system, not a dive in/dash out incident.

9. Sep 17, 2016

### Bandersnatch

No, it's all fine.

It can't just spiral in without a way to lose energy. If you've got a free-floating planet that encounters a lone star, then it MUST fall towards it on a hyperbolic trajectory, swing around, and leave with the same velocity relative to the star as it had at the beginning.

What you could do, is have the star begin with some planets, one or two, have the planet fall in, make a number of close encounters with the original planetary system, and as a result end up with the original planet(s) ejected and the rogue one captured.

10. Sep 17, 2016

### Noisy Rhysling

That would work. So it would be possible under certain circumstances... Interesting. Now to get Our Hero to figure out what's strange about the system. Thanks.

11. Sep 19, 2016

### snorkack

It tends to be unstable due to Kozai resonances.

12. Sep 19, 2016

### Bandersnatch

There's no third body in this setup.

13. Sep 19, 2016

### Noisy Rhysling

Yeah, I'm thinking the system is "strangely barren" with the exception of our oddly orbiting planet.

14. Sep 19, 2016

### Noisy Rhysling

Next thing, is a star with almost no "junk" around it uncommon, unlikely, no big deal, or "never gonna happen"?

15. Sep 26, 2016

### hsdrop

well you could have a neighboring star blow up and blow most to all the junk out from around it ( just a thought)

16. Sep 26, 2016

### Noisy Rhysling

With so many double star sysem...