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Author Topic: Issues while trying to simulate Centauri Star system  (Read 1477 times)

Canche

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Issues while trying to simulate Centauri Star system
« on: November 05, 2017, 12:27:40 AM »
I just bought Universe Sandbox a few days ago so keep that in mind because I don't even know if what I am trying to create is possible.

I am trying to simulate (possible) trinary Centauri Star system which includes Alpha Centauri A, Alpha Centauri B, Proxima Centauri and it's exoplanet Proxima b. However, I am having issues trying to get Proxima Centauri to orbit the Alpha binaries, even if I place Proxima C within spitting distance of the binary Alphas. All data used is the most recent I can find and includes: Eccentricity, Semi-Major Axis, Inclination, Argument of Periapsis, Right Ascension of the Ascending Node, and Orbital Period. Possible mistakes/errors on my end are as follows:

1. I did not check the "Balance Motion" box when creating the Alpha binary system. Not exactly sure what effect this has.

2. The data for both the Semi-Major Axis and Orbital Period seem to contradict themselves from the same source (inputting correct Orbital Period gives changes Semi-Major Axis incorrectly and vice versa). Also, if I have the data for Orbital Period, would that not negate the need for velocity? If not, would I use Radial Velocity (Rv) data or another type of velocity data?

3. I just did something stupid.

Remember, even if I place Proxima right next to the binary Alphas it still will not orbit. As for the data contradiction for Proxima Centauri in number 2 the data is as follows: Semi-Major Axis=8400 AU; Orbital Period=547,000 yrs.

Attached is the simulation. Sorry so long...

SyzygyΣE

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Re: Issues while trying to simulate Centauri Star system
« Reply #1 on: November 05, 2017, 01:22:25 AM »
  • Balance Motion on. Create Alpha Binary system.
  • Place Proxima at the required distance from the Alpha Binary system, not with "Orbit" mode, but with "Binary" mode and Balance Motion off.
That should do the job.

Canche

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Re: Issues while trying to simulate Centauri Star system
« Reply #2 on: November 05, 2017, 08:51:26 PM »
Thank you very much. I will try that out right now and post results!

Canche

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Re: Issues while trying to simulate Centauri Star system
« Reply #3 on: November 05, 2017, 10:10:33 PM »
Although I tried your suggestion, still no luck.

However, I noticed that it seems as if the binary stars speed is faster than Proxima Centauri is able to orbit. If I position lock Centauri A, Proxima C will orbit. Velocity issue?

SyzygyΣE

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Re: Issues while trying to simulate Centauri Star system
« Reply #4 on: November 06, 2017, 12:44:37 AM »
You are creating the system accurately, yes? If Proxima really takes 547,000 years to orbit, it won't display very well on the timewarp rate in the game. It'll appear as if it's stationary while Alpha A and B orbit each other. What exactly does the orbit look like? How is it behaving strangely?

Designing trinary systems does not need position locking. It doesn't handle these situations very well. I would steer clear of it because it's not meant to fix the problem.

tkulogo

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Re: Issues while trying to simulate Centauri Star system
« Reply #5 on: November 06, 2017, 08:28:47 AM »
If you want to see Proxima orbit in a reasonable amount of time, you need to not have the shorter orbits. Universal Sandbox² can only simulate at most, a few orbits a second. When you start putting in orbits that are millions of times longer than your shortest orbit, there’s nothing to see unless you leave the simulation running for a couple months, and come back and check it. If you make Alpha Centauri A the mass of A+B, leave out Alpha Centauri B, and put Proxima in orbit, you’ll be able to speed up the system and see it orbit like it actually would. You could them slow down the system, place a very low mass Alpha Centauri B in the system, slowly increasing its mass while decreasing A’s proportionately, and it shouldn’t mess up Proxima’s orbit. Then you can add in Proxima b. It’ll be accurate enough, but they’ll effectively be 2 separate systems anyway because of the huge difference in orbital periods.

Physics_Hacker

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Re: Issues while trying to simulate Centauri Star system
« Reply #6 on: November 06, 2017, 10:38:53 AM »
If you want to see Proxima orbit in a reasonable amount of time, you need to not have the shorter orbits. Universal Sandbox² can only simulate at most, a few orbits a second. When you start putting in orbits that are millions of times longer than your shortest orbit, there’s nothing to see unless you leave the simulation running for a couple months, and come back and check it. If you make Alpha Centauri A the mass of A+B, leave out Alpha Centauri B, and put Proxima in orbit, you’ll be able to speed up the system and see it orbit like it actually would. You could them slow down the system, place a very low mass Alpha Centauri B in the system, slowly increasing its mass while decreasing A’s proportionately, and it shouldn’t mess up Proxima’s orbit. Then you can add in Proxima b. It’ll be accurate enough, but they’ll effectively be 2 separate systems anyway because of the huge difference in orbital periods.

This is pretty accurate, but it may just be easier to use the mass of the main two stars, add them together and use  this site: http://orbitsimulator.com/formulas/vcirc.html to get a circular orbit velocity for Proxima once you balance the orbits of A and B so they cancel out into a single mass/non-moving barycenter and then change the orbit of Proxima as needed, then add Proxima b. Its essentially the same thing except possibly more exact, I'm not sure.

Canche

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Re: Issues while trying to simulate Centauri Star system
« Reply #7 on: November 13, 2017, 08:11:54 PM »
Awesome information guys. I can't wait to use this circular velocity formula! I'm going to use these methods and try it out with a combined mass of A and B and play around some more. Thanks for the help!