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five planet system (Read 14785 times)
abyssoft
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Re: five planet system
Reply #15 - 10/18/06 at 20:35:42
 
Yes I'd be interested....
 
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and an up date on the TS=16K sim
upto 15 myr and still stable
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Re: five planet system
Reply #16 - 10/18/06 at 22:32:00
 
I might be interested in that, though I have an irrational aversion to leaving my computer turned on overnight Wink.  
 
I guess the best thing to do is to take a system that's borderline unstable, save the initial setup as a gsim file and then run it at various timesteps?  
 
I've got a load of systems we could use for this. (though usefully I just changed the code of my system generator to ditch the GGs that make it unstable, but I still have an old version of the code that generates the full system)
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abyssoft
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Re: five planet system
Reply #17 - 10/20/06 at 04:12:57
 
now up to 20 myr @ ts=16K
4 migrating closer to 5  
3 becoming more erratic in it's orbital procession
1 migrating outward a little
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Tony
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Re: five planet system
Reply #18 - 10/20/06 at 10:22:57
 
It is starting to look like my "random" guess was wrong, and that "time to first ejection" is dependent on time step.
 
If you can, keep running this one.  Let's see what happens.  Then next week, we can think about how approach this in a more organized fashion.
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Re: five planet system
Reply #19 - 10/20/06 at 13:23:06
 
I think here is where it could be useful to have the ability to just move one or more planets around on their orbits manually. Instead of the current "edit object" window, i think it would be a lot better to have the "Create Object" window show up with the current values of positions, eccentricity etc already filled in. Then those can be directly edited and the simulation continue with the new parameters.  
 
That way we can move a planet around in its orbit at the start of the simulation (relative to where it was in the original save file) and see if that changes things too - the current edit object window is too inconvenient to be able to do this easily.  
 
EDIT: And woo! With this post I just became the poster who'd made the most posts on the forum apart from Tony and abyssoft! Wink
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Re: five planet system
Reply #20 - 10/20/06 at 21:19:42
 
22.5 myr  
the orbits of 4,3 has become increasingly distorted  
22.55 myr  
the orbit of 4 has become extremely distorted
22.6 myr  
the orbit of 4,5 now cross
22.605 myr
5 migrating inward
4 migrating outward
the possible appearance of a barycentric cyclic 1:1 resonance binary (4,5)
22.61 myr
4 now outside 5
possible 1:1  
22.62 myr
1:1 chances reducing as 3 becomes more unstable
22.63 myr
1:1 nolonger possible
Coalescence possible (4,5)
22.65 myr
4 back inside 5
 Shocked
orbit of 4 ovoid
orbit of 5 almost circular
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frankuitaalst
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Re: five planet system
Reply #21 - 10/22/06 at 01:25:46
 
I've been following this discussion since a couple of days and am also running the 5-sim . It seems to me also that the time step is very important . A system ( also other systems) gets easily "exited" if the time step is too much . It seems to me that one possibilty to examin the time step is to calculate te total energy of the system . As during intgration the kinetic energy moves into gravitational energy and vice versa , and while the total energy should be conserved if the calculation is well done , it may be a good idea to calcuate the total energy of the whole system . If this energy "moves" away it may indicate that the time step is too much . Perhaps some work to do for Tony ?
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Tony
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Re: five planet system
Reply #22 - 10/22/06 at 12:16:18
 
That's not a bad idea.  Or perhaps to monitor angular momentum, as it is conserved as well.
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Re: five planet system
Reply #23 - 10/22/06 at 12:21:19
 
Thanks for the consideration tony . I think it might help , but there's perhaps some programming work involved ....
I run here at home a simple Excel sheet for a 2 body system in which one can clearly see the influence of time -step ...
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Re: five planet system
Reply #24 - 10/22/06 at 21:11:40
 
just got home and looked at the sim
 
30 Myr  
 
2,3,4 ejected from system
1 in tight eccentric orbit
5 in wide slightly eliptical orbit
 
Going to start on a 8K TS sim
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Re: five planet system
Reply #25 - 10/22/06 at 23:31:42
 
So when it all goes wrong, it happens pretty quick, eh? Wink
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Re: five planet system
Reply #26 - 10/23/06 at 07:59:42
 
it would appear to be the case
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abyssoft
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Re: five planet system
Reply #27 - 10/23/06 at 22:54:04
 
TS=8k
2 myr
orbit 3 getting pulled about like taffy
ecc1 = 0.010 to 0.015
ecc2 = 0.06 to 0.07
ecc3 = 0.05 to 0.12
ecc4 = 0.11 to 0.12
ecc5 = 0.10 to 0.11
 
from watching slower sims progressively I would have to say that ultimately the cuprit for the system instability is 3.
 
3 has approached rather close to 2, <450 Tm
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Re: five planet system
Reply #28 - 10/24/06 at 06:34:47
 
early update because it's interesting
 
2.5 Myr
 
3 approaching 2 as close as 250 Tm
 
ecc1=0.033-0.038
ecc2=0.048-0.053
ecc3=0.030-0.10
ecc4=0.190-0.200
ecc5=0.070-0.080
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abyssoft
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Re: five planet system
Reply #29 - 10/30/06 at 19:07:54
 
Figured I give an update to this sim.
 
Soz I've been away other then keeping the bots at bay be under the weather...
feeling a bit better now though so I should be around more often again.
 
@ TS=16K
 
things are definitely different,  @ 12 Myr 4 & 5 changed places with 4 migrating a healthy distance and things for the moment appear stable.
 
currently the sim is @ 15.5 Myr
 
1
a=6.272
e=0.015
2
a=11.796
e=0.003
3
a=14.362
e=0.084
4
a=50.906
e=0.170
5
a=34.242
e=0.243
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