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Message started by JMK on 03/01/06 at 10:28:13

Title: .Sun/Planet forming
Post by JMK on 03/01/06 at 10:28:13

Could anyone create a simulation for me that would show planets and stars forming please. If that doesn't work or you know the paramaters needed please give them ot me so I can attempt to make the simulation for my self. Thank you

P.S. I was thinking of something along the lines of the moonbuilder simulation.

Title: Re: .Sun/Planet forming
Post by Tony on 03/03/06 at 12:55:28

For planet formation, you need to stick to 1 planet at a time, since the whole solar system would require too many objects.

File > New
This gives you a solar-size and solar-mass object.  Edit the name and color if you wish.

Zoom out to around 4-5 AU

Objects > Create Objects
Number of objects: 200
Semi-major axis: 1 AU +/- 5%
Size: 3000 km
Mass: 0.016 Earth masses
Leave all other values at their defaults.
Press Create.

Increase time step up to 2048, sit back and watch.

Using these particular inputs, you'll have to run the simulation for a few days in the "Don't Plot" mode to see 1-3 planets beginning to dominate.

You can speed things up a bit by giving your planetesimals a higher mass and/or a larger diameter.

Regarding your other post and Chaos theory, when creating this simulation, save it, run it for a few hours, then open it, make a small change such as deleting 1 object, or increasing the mass of 1 object, then run it for the same amount of time as your first run.  You'll see how a small change leads to much bigger changes over the course of time.

Title: Re: .Sun/Planet forming
Post by Overlag on 05/13/06 at 05:09:46

oooooh that's great i been trying to do this myself with quiet poor results. But using the info you gave above i managed to make 2 planets one at about 0.7au and one at 1.2-1.3au (I'm guessing here, i don't know where to find info on this?) They both stable, and haven't got enough pull on each other to wreck each others orbits (not yet at least).

It was interesting though, i started the simulation with your settings (+ double the mass and slight larger sizes) and after a few hours, i relabeled the objects that had got much bigger as possible planets. I labeled them in order outwards, so i had PLANET1, PLANET2 up to 4 large objects.

In the morning after 110'000years, only PLANET1 had survived, as well as a newer object that i had not labeled as a possible planet back in the days. PLANET1 hand migrated outwards slightly and the "New" PLANET2 was probably one of the lowest points of the original belt system that was in place. I kept PLANET2 as its original name even though its now the 1st planet.

Sol = 2x sun mass, 1.8x dia
PLANET2 = 2.08 earth mass, 1.262 dia
PLANET1 = 4.32 earth mass, 1.6 dia

I'm now trying to build up an outer plant the size of Jupiter, but that means adding a lot more objects and mass, which in turn slows the Sim right down. I think i doubled my mass and dia of objects in this outer ring, and i added "only" 300 objects (it should really be double or more, 400+ really?)

This belt has already grown 3 larger objects, which again I've labeled and colored differently to the belt system (which is white).

Will post pictures soon of the progress :)

Title: Re: .Sun/Planet forming
Post by Overlag on 05/13/06 at 16:07:25

Ok some updates.

First, the photo from the time i posted the info earlier

and now, 11 hours later.

Note that the belt is starting to get deformed and spread out more.
Also the speed has dropped quiet alot, i dont have trace on, and i leave it on dont plot. but 11hours over night was about 132'000 years, yet 11hours with this 2nd belt (300 objects vs 200) has been only 500 years!!!!

I have an AMD X2 @ 2400mhz would i be able to use 4096sec's or more for planet building??

any tips for building planets further out?

Title: Re: .Sun/Planet forming
Post by Tony on 05/14/06 at 11:59:52

Nice job with the pictures.  It looks like you're building your system planet by planet!

For any collision simulation, keep the time step slow enough that planets can actually collide.  For example, at 4096, Earth would move 30 km/s * 4096 s = 122800 km, which is 10 times its diameter.  So Earth would likely jump over any particle it encountered, rather than collide with it.  You should probably stick to having your planet jump no more than roughly 1/4 of its diameter per time step.  For Earth, moving at 30 km/s, this would mean a maximum of about time step 128.

Do you notice a lot of particles being ejected at unrealistic speeds?  That would indicate a time step that is too fast.

A trick around this problem is to exaggerate a planet's size.  You could make them 10 times bigger (but not 10x more massive) to speed up the accretion process.  You'll be colliding with particles that you'd have otherwise missed, but the odds are high that you would have eventually ended up colliding with them anyway.  This gives you more of a qualitative result rather than quantitative, but your results will probably allow you to discover trends that would happen in any system.

Good luck.  Keep posting pictures!  (256 color GIFs work well).

Title: Re: .Sun/Planet forming
Post by Overlag on 05/14/06 at 15:17:51

well I've left it running constantly for about 36hours now, the two inner planets formed in under 11hours id guess, these outer ones are taking there time but I'm finally getting somewhere.

No objects have been expelled from the system as yet, although some are in quiet large "comet like" orbits, so i will now call them comets. Any object that gets expelled i will probably delete as they are no longer any use?

This morning, after being a bit bored at the lack of progress i did what you just said in your last post, i found all the larger objects (x5-x10 the size of original objects) colored them and named them planets, i then doubled there DIA to cheat, and increase the chances of "hits". I didn't increase there sizes over 4eDia's though, so to keep them smaller than the inner planets, and let everything grow naturally.

This shows the picture just before i increased the size of planets, note that the belt has probably doubled in width since id set it, reducing chances of hits??? Also note a few comets, and that the inner planets are still stable and not getting pulled by the belt, or any of the outer planets.... Yet.....

a few 1000 years later and a lot has changed. Not only has the planets increased in size VERY fast, but they are also large. The largest is pointed at in the picture, and is around 22 Earth masses. This planet is messing up the orbit of everything around it now, including inner planets! Its also caused a few comets to increase into 250-300 year orbit comets... and i get bored waiting for them to come back and do a full trace (like in the first picture).

Its a bit of a mess but nothing expelled yet..., and I'm sure the planets and the few remaining objects will fight for the space and i hope to have around 2-3 Saturn or Jupitor size planets, but i don't think its going to happen....

Title: Re: .Sun/Planet forming
Post by Overlag on 05/15/06 at 02:57:18

ok most objects have now fully formed... some notes

1: The sun has been hit, its gained mass, but lost size

2: Planet2, the more stable inner planet was hit and joined planet1

3: the comet that was going around the sun in the opposite direction has disappeared.

4: 3 planet sized objects, and 4 small objects have been expelled, 5LY away!!!

In order they orbit:

sMass 2.50000300315217 (was 2.5)
sDia 1.99997312747994 (was 2)

eM 9.4
eDia 1.8
SMA 76,900,000.000
ecc 0.267 - 0.268
PDist 56,312,000
ADist 97,447,000

eM 44.95, jM 0.141
eDia 3.46, jDia 0.328
SMA 262,599,000
ecc 0.12700 - 0.12708
PDist 229,220,000
ADist 295,960,000

eM 4.2
eDia 1.8
SMA 805,598,000
ecc 0.306
PDist 558,605,000
ADist 1,052,592,000

eM 13.7
eDia 2.4
SMA 1,028,072,000
ecc 0.252
PDist 769,109,000
ADist 1,287,035,000

eM 7
SMA 893,349,000
ecc 0.680
PDist 286,183,184
ADist 1,500,515,000

Most distant comet
eM 1
eDia 0.7
SMA 7,412,000,000
ecc 0.934
PDist 486,000,000
ADist 14,344,000,000

some images from this last night/this morning

Comets from last night

Expelled objects :( these are the outer 3, there was some half that distance that you cant see in this shot, ie they still look to be within the main system from this range.

Full orbits of long range comets

Close up showing inner orbits.

Even closer, note a new comet, which orbits in the same direction as all objects, unlike the comet it replaced, also note the missing Planet2...

Labels of planets

Title: Re: .Sun/Planet forming
Post by abyssoft on 06/04/06 at 08:21:00

'm currently working on a Simulation set that adds objects over a period of time in steps.  I have been very careful in attempting to create a series of overlapping progressing rings, Where the matter density varies by less then a factor of 100 from highest to lowest.  So far so good.  once I have a bit of better results and have been able to run the sim a few more time to work out the kinks I'll be happy to post my setup.  until then I welcome any questions peeps may have on world building.

Improving on the Density Spread further Now I have it down to less then a factor of 25 With having this success I will endevor to get it below a factor of 10

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