Oort Clouds and outer asteroid belts of Binary Systems

[hikoriyami]

Recently, I've been trying to find information on Oort clouds and accretion disks  (hard enough) and how they would function in a binary system. Lets look at Alpha Centauri AB as the stars in this thought experiment. Our own Oort cloud is far, far, far out past Pluto and may not even exist (lets pretend it does) and Alpha AB orbit each other at about the distance of Neptune to the Sun. 

So my question is; how would an Oort cloud, or outer asteroid belt look in this binary system. Would it encompass both stars? Would the each star have it's own cloud, or gain one from disturbing the binary Oort cloud? And finally; how would individual objects probably behave (ie what will a comet's orbit look like)?

If anyone has any reading material on this subject or could point me in the right direction, that'd help. Simulations in Universe Sandbox don't give reliable data. I'm guessing from my understanding of physics and reality, that the actual answer is some mixture of the above.

[Wjolcz]

I am not an expert, but If I had to guess the comets' orbits would be probably constantly changing each time they pass the inner system. Either that or they would also orbit the barycentre and be far away and faint because of that. The Oort cloud would probably be gone by now (because of two massive bodies orbiting each other and pulling the stuff in and out all the time).

Edited January 18, 2017 by Veeltch

[p1t1o]

A binary system can be anything from two stars sharing an atmosphere and feeding off one another to two stars a good fraction of a light year apart, so obviously there are many different answers.

I'd imagine though, that conditions are generally less favourable for belt formation due to the less static gravitational environment. Whenever you have an orbit existing in changing conditions there is a constant chance that object will be disturbed - ejected, drawn into the inner system - and even if it is very gradual, over time this will erode any long term arrangement.

[Steel]

The effect might be surprisingly small, considering the inner edge of the Oort cloud is predicted to be more than two orders of magnitude further away than the orbit of Neptune (~5000 AU vs 30 AU)

[Shpaget]

In contact binary, and even a few AU separated stars, wouldn't the gravitational pull be the same as with a single star of equivalent mass at the barycenter? At the Oort cloud distances, tidal forces would be negligible, just like in our system the presence of Jupiter does not interfere with the formation of Oort cloud, or even Kuiper belt.

[p1t1o]

41 minutes ago, Shpaget said:

In contact binary, and even a few AU separated stars, wouldn't the gravitational pull be the same as with a single star of equivalent mass at the barycenter? At the Oort cloud distances, tidal forces would be negligible, just like in our system the presence of Jupiter does not interfere with the formation of Oort cloud, or even Kuiper belt.

At those distances that probably true. Though Jupiter is about 1000x less massive than the sun and the sun is a pretty average mass star. 

Though according to the wiki, the Oort cloud can be perturbed by other nearby stars, and apparently about 70k years ago, a star ("Scholz's Star") passed through it, so it appears that it is so big that the star(s) it orbits are not the only significant operators.

On thinking about it though, even if it is perturbed, the speeds and distances are such that I guess it would take a stupendous amount of time to do much to it.

Edited January 18, 2017 by p1t1o

[hikoriyami]

Interesting, so would we be expecting to see comets orbit the barycenter. That was what I was thinking also. I do not think an orbit that switches between both stars would be stable in the long run...and also impossible to mimic in KSP.

[Shpaget]

On 1/18/2017 at 5:30 PM, p1t1o said:

At those distances that probably true. Though Jupiter is about 1000x less massive than the sun and the sun is a pretty average mass star. 

Though according to the wiki, the Oort cloud can be perturbed by other nearby stars, and apparently about 70k years ago, a star ("Scholz's Star") passed through it, so it appears that it is so big that the star(s) it orbits are not the only significant operators.

On thinking about it though, even if it is perturbed, the speeds and distances are such that I guess it would take a stupendous amount of time to do much to it.

Sure, Jupiter is a lot smaller than a generic star, but it's also a lot closer to Kuiper belt, not to mention the main belt.

 

19 hours ago, hikoriyami said:

Interesting, so would we be expecting to see comets orbit the barycenter. That was what I was thinking also. I do not think an orbit that switches between both stars would be stable in the long run...and also impossible to mimic in KSP.

If they come too close to one of the stars, they could get perturbed. It really depends on the distance between the stars.

There are some really funky orbits out there, one example of them being out close neighbor.

https://en.wikipedia.org/wiki/(469219)_2016_HO3

[p1t1o]

14 hours ago, Shpaget said:

Sure, Jupiter is a lot smaller than a generic star, but it's also a lot closer to Kuiper belt, not to mention the main belt.

What I was getting at was a star could easily be a 10-100,000x more massive than Jupiter.

[Green Baron]

On 17.1.2017 at 11:22 PM, hikoriyami said:

Recently, I've been trying to find information on Oort clouds and accretion disks  (hard enough) and how they would function in a binary system. Lets look at Alpha Centauri AB as the stars in this thought experiment. Our own Oort cloud is far, far, far out past Pluto and may not even exist (lets pretend it does) and Alpha AB orbit each other at about the distance of Neptune to the Sun. 

So my question is; how would an Oort cloud, or outer asteroid belt look in this binary system. Would it encompass both stars? Would the each star have it's own cloud, or gain one from disturbing the binary Oort cloud? And finally; how would individual objects probably behave (ie what will a comet's orbit look like)?

If anyone has any reading material on this subject or could point me in the right direction, that'd help. Simulations in Universe Sandbox don't give reliable data. I'm guessing from my understanding of physics and reality, that the actual answer is some mixture of the above.

Yes, that IS an interesting question. I have followed the publications over the last years but i am not an astronomer.

There is no easy answer to your question. Sol's Oort cloud has revealed itself through gravity and the origin of the comets, but it's total mass is very low compared to what's farther inside. Some objects might even be interstellar and only gravitationally bound on a temporary basis. If they are gravitationally bound their orbit times may reach 10.000s or even hundred thousands of years. This is according to the model of the formation of our system and that system seems to be somewhat special compared to what was discovered in the last 15 years.

The accretion disk seems to be a common part in the formation of star systems because quite a few are being observed. But then things mostly seem to go separate ways (note that i am a little cautious with my formulations :-)). In our case things were sorted quite well, rocky planets inside (still, this observation is probably just about to change fundamentally), gas giants outside. What was discovered in other systems until now is mostly different. But the observations could be influenced by our limited observation techniques. Whether a cloud of icy rubbish forms depends on when and where the accretion disk forms and how the system evolves. Our system always remained in a quiet environment and could have been able to collect interstellar dust that is now more or less bound or even exchanged with neighbours. The cluster Sol originated from has dispersed but some of the former members are still detectable*.

Before i blather too much: there is no easy answer to your question. Proxima Centauri may have an Oort cloud as well, until recently it wasn't even sure whether the star is bound to the Alpha Centauri system. If you want reliable information i'd suggest to search sciencemag.org and www.nature.com. Abstracts and references are interesting enough.

Post here your findings !

:-)

*Speculation: that's where we should look for life(tm) ... but they are so far away ... :-)

 

Edited January 20, 2017 by Green Baron

[SuperFastJellyfish]

5 hours ago, Green Baron said:

If you want reliable information i'd suggest to search sciencemag.org and www.nature.com. Abstracts and references are interesting enough.

https://scholar.google.com/, as well.