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Castor Binary (6 star hierachy) system, how is it stable?

by Edward Solomo
Tags: binary, castor, hierachy, stable, star
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Edward Solomo
#1
Aug14-13, 10:16 PM
P: 72
Hello, I made this video from Celestia showing the orbits of the 6 stars that comprise of the Castor system:

http://www.youtube.com/watch?v=wIWdf...ature=youtu.be

However, I noticed that when Castor C (the barycenter of Castor-Ca and Castor-Cb) enters the fastest part of its orbit (between seconds 10 and 12.5 in the video), Castor B occasionally becomes closer to Castor C than Castor A.

So if Castor B becomes within very close proximity of Castor C, why doesn't Castor AB (the barycenter of Castor A and Castor B) dissolve?

I understand that the differences in masses my account for it, as Castor A and Castor B are main sequence stars (Type A), and Castor C is a dwarf star, but it is still hard to imagine that Castor B wouldn't be thrown off course when the binary dwarfs (Castor Ca and Castor Cb) are practically next door.
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Vanadium 50
#2
Aug15-13, 05:33 AM
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WHat makes you think this system is stable? It might well eject a star or two over the next billion years.
Bandersnatch
#3
Aug15-13, 06:50 AM
P: 697
Perhaps you mistakenly think that Celestia simulates gravitational interactions. It does not. Whatever you set as the orbital parametres, will remain unchanged forever.

What you should do is use one of gravity simulators:
http://www.gravitation3d.com/
http://www.orbitsimulator.com/gravit...cles/what.html
http://www.andersson-design.com/gravity/

Be mindful of their limitations, though. For example, setting too high a time rate might erroneously destabilise the system.

Edward Solomo
#4
Aug15-13, 11:44 AM
P: 72
Castor Binary (6 star hierachy) system, how is it stable?

Quote Quote by Vanadium 50 View Post
WHat makes you think this system is stable? It might well eject a star or two over the next billion years.
Seeing that Castor C (Castor-Ca and Castor-Cb) complete their orbit every 10,000 - 11,000 years, I would consider a 2 billion year time frame to be relatively stable
Edward Solomo
#5
Aug15-13, 02:50 PM
P: 72
In general, I'm surprised that this system could survive even a single 10,000 cycle, and be stable enough to nearly repeat the same pattern again over the next 10,000 years.

I see Cantor AB dissolving on the first pass of Castor C, and all of them spiraling off into space.
Bandersnatch
#6
Aug15-13, 04:56 PM
P: 697
(disregard my previous post. Somehow I thought you were making a fictional system from scratch)

Have you got some more recent data that would suggest the exact configuration that you used in your visualisation?

This paper:
http://articles.adsabs.harvard.edu//...00240.000.html
concludes that it's quite likely(~60%) the C components are on a hyperbolic orbit(i.e., single passage), and stable elliptical with (~40%). The probability of an unstable system is very low.

Furthermore, if you look at fig.2(showing most likely configuration) from the above article, the closest approach distance of ~800AU is still huge, which should explain the stability.
mfb
#7
Aug15-13, 05:19 PM
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P: 11,631
Why did you add music :(.
Now the video is blocked in Germany.
Edward Solomo
#8
Aug15-13, 05:57 PM
P: 72
Quote Quote by mfb View Post
Why did you add music :(.
Now the video is blocked in Germany.
Because I also happen to be an active Libertarian in the United States, are you serious??? ; and since I'm also a music major (clarinet, piano and composition/arrangement have been my majors), how do they know it's not my music (even though it isn't) ???


EDIT:
Damn, you are serious:

http://en.wikipedia.org/wiki/Blockin...eos_in_Germany


EDIT: No music
I'll upload a new one without music.

http://www.youtube.com/watch?v=QCV15...ature=youtu.be

Shame, it was a medieval chorus
mfb
#9
Aug16-13, 03:28 AM
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P: 11,631
Thanks.
It would be interesting to see the 3-dimensional distances. As those stars can be separated in telescopes, their 3-dimensional positions and motions should be known.
Edward Solomo
#10
Aug16-13, 01:35 PM
P: 72
Quote Quote by mfb View Post
Thanks.
It would be interesting to see the 3-dimensional distances. As those stars can be separated in telescopes, their 3-dimensional positions and motions should be known.
I'm working on a 3D simulation right now in the Starcraft Galaxy Editor. Yes I know that sounds funny, but the video game [Starcraft II] engine is actually one of the best simulators I've ever encountered, even though it was never intended to be one.
DHF
#11
Aug16-13, 03:38 PM
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P: 65
I only see 3 stars. is each star in the video actually a pair of stars? the resolution is pretty grainy on my screen to differentiate.
Edward Solomo
#12
Aug16-13, 09:51 PM
P: 72
Quote Quote by DHF View Post
I only see 3 stars. is each star in the video actually a pair of stars? the resolution is pretty grainy on my screen to differentiate.
Yeah I could zoom in if I wanted and you'd see the binary systems.
DHF
#13
Aug16-13, 11:40 PM
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P: 65
it sounds fascinating. I couldn't find it in Celesta though. It only comes up as a single star system. what are the coordinates?
Edward Solomo
#14
Aug17-13, 02:07 AM
P: 72
Quote Quote by DHF View Post
it sounds fascinating. I couldn't find it in Celesta though. It only comes up as a single star system. what are the coordinates?
You'll have to download the Castor 6 pack (addon).
DHF
#15
Aug17-13, 11:28 AM
DHF's Avatar
P: 65
gotcha thanks


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