Creat an accretion Disk
First you need to put a center object mass like a M dwarf star, a brown dwarf and etc... But reduce its size into a Jupiter mass object. Ex a 0.15 Sun Mass Star will be 0.15 Jupiter Mass Object.
Then for the disk (depend on your computer speed and power), put many objects in orbit, make them explode in 500 objects (select the average speed and the mass of the object). Dont put dense objects on it...more they are dense...smaller they are...so they ll be fewer colisions.
I normally put 2 objects of about the same mass on the same orbit but 180 degrees from each others...so one is on the right side of the ''protostar'' and the other one is on the other left side. And i continu like this until i m satisfied.
PS don t forget to desactivate dust, trail and impacts marks at the start...if not your universe sandbox will crash...then bye bye to your work. Wait at least a universe sandbox year to put back dust and impact marks... And don t forget to save many times!
When you save delet trails, impact marks and dust...it will reduce the size of your simulation...if you don t do this...it won t save. I normally click many times on the 3 just to be sure, because when you have many objects your simulation is much slower.
Running the accretion Disk and making the protoplanets grow.
At the start of the accretion disk....if i have an object over 2000 km in diameter, i normally increase its density...those will be my dominants planets (like jupiter in our own solar system) But this depend on the mass of the star. Ex: 2250 km diameter with a density of 9.54. My star is a 0,75 solar Mass (0,75 jupiter Mass in the accretion disk simulation) i add 1,8 grm/cm3 = 10.84 gr/cm3. the mass will increase so lock the diameter for this step. Here how i do it.
* 0.095 to 0.24 sun mass : 0.3 gr/cm3
* 0.25 to 0.35 sun mass : 0.6 gr/cm3
* 0.36 to 0.70 sun mass : 1.2 gr/cm3
* 0.71 to 1.1 sun(s) mass : 1.8 gr/cm3
* 1.11 to 1.3 suns mass : 2.4 gr/cm3
* 1.31 to 2.2 suns mass : 3.0 gr/cm3
So now you have 1 or 2 dominant planets. PS i normally put moon mass objects in the accretion disk (at the start)...because i don t want to end up with only brown dwarfs when i put back to scale the new born solar system.
Then now select a time space that you increase the diameter of your protoplanets ( yes no choice since we cant put billions of object in orbit, we need to help it)...select a time space between 20 to 100 yrs (depend how fast the simulation disk goes and how big is your accretion disk....if its small it will eliminate the objects faster by colision...if its bigger well it will mostly catapult objects. I normally select 20 yrs if the simulation is slow and don t eliminate many objects and 50 yrs and over if it goes faster. Normally i eliminate objects that are over 23 degrees orbit inclination....why? Because an accretion disk mostly look like a disk and i want my planets to be in a nearly same inclination... (personal choice***)
Here to increase the mass i play with the diameter of each object...so here how i do it. The xxx yrs that will be your time space...20 yrs, 30 yrs, 50 yrs... 100 yrs. Don t forget to lock the density of the object.
First 4 diameter increase shots
1st Diameter shots
add every XXX yrs
2000 km and + 400 km
1500-1999 km 200 km
1100-1499 km 100 km
1000-1099 km 50 km
800-999 km 25 km
700-799 km 13 km
5 others shots after the 4 first shots
2nd Diameter shots
add every XXX yrs
2000 km and + 200 km
1500-1999 km 100 km
1100-1499 km 50 km
1000-1099 km 25 km
800-999 km 13 km
6 others shots after the 5 shots
3rd Diameter shots
add every XXX yrs
2000 km and + 100 km
1500-1999 km 50 km
1100-1499 km 25 km
1000-1099 km 13 km
7 others shots after the 6 shots
4th Diameter shots
add every XXX yrs
2000 km and + 50 km
1500-1999 km 25 km
1100-1499 km 13 km
8 others shots after the 7 shots
5th Diameter shots
add every XXX yrs
2000 km and + 25 km
1500-1999 km 13 km
***Again to help growing major planets (after the 4 first shots add to the density...for object that are now 4500 km in diameter) + for objects over 6000 km (if you have some) double this table to it. Don t forget to lock the diameter.
* 0.095 to 0.24 sun mass : 0.9 gr/cm3
* 0.25 to 0.35 sun mass : 1.8 gr/cm3
* 0.36 to 0.70 sun mass : 3.6 gr/cm3
* 0.71 to 1.1 sun(s) mass : 5.4 gr/cm3
* 1.11 to 1.3 suns mass : 7.2 gr/cm3
* 1.31 to 2.2 suns mass : 9.0 gr/cm3
*** After the 5 others shots (again to help bigger objects 5500 km and more) add this table. To object that are now 6000 km or 6500 km and over... double this table. don t forget to lock the diameter.
* 0.095 to 0.24 sun mass : 0.3 gr/cm3
* 0.25 to 0.35 sun mass : 0.6 gr/cm3
* 0.36 to 0.70 sun mass : 1.2 gr/cm3
* 0.71 to 1.1 sun(s) mass : 1.8 gr/cm3
* 1.11 to 1.3 suns mass : 2.4 gr/cm3
* 1.31 to 2.2 suns mass : 3.0 gr/cm3
Then at the end to give them a last burst here how i do it on the diameter of the object. For the biggest objects (if you have some over 10 000 km, double it. like if you have an object of 10300 km and a sun mass (jupiter mass to scale**) of 0,71 then you ll add to this object 3 times 1200 kms (lock the density)
* 0.095 to 0.24 sun mass add 400 km (2000 km +), 200 km (1500 to 1999 km), 100 km (1100 to 1499 km) 50 km (1000 to 1099 km) (1 time).
* 0.25 to 0.35 sun mass add 600 km (2000 km +), 300 km (1500 to 1999 km) and 150 km (1100 to 1499 km), 75 km (1000 to 1099 km). (1 time)
* 0.36 to 0.70 sun mass add 600 km (2000 km +), 300 km (1500 to 1999 km) and 150 km (1100 to 1499 km), 75 km (1000 to 1099 km). (2 time)
* 0.71 to 1.1 sun(s) mass add 600 km (2000 km +), 300 km (1500 to 1999 km), 150 km (1100 to 1499 km) and 75 km (1000 to 1099 km). (3 time)
* 1.11 to 1.3 suns mass add 600 km (2000 km +), 300 km (1500 to 1999 km) and 150 km (1100 to 1499 km), 75 km (1000 to 1099 km). (4 times)
* 1.31 to 2.2 suns mass add 600 km (2000 km +), 300 km (1500 to 1999 km) and 150 km (1100 to 1499 km), 75 km (1000 to 1099 km). (5 times)
If you like statistics and want to follow the grow i suggest you to do all this in microsoft excel and do a table like this:
Dwarf Star 1
Years 10 20 30 40 50
Number objects 1451 1417 1390 1374 1356
Catapult objects 3 2 1 2
Proto Planets 12 14 13 13 13
Proto elimination Pm
Bring back to scale your new born solar system.
First: If you want to reduce your work i suggest to delet all objects under 200 km...because you ll have many of them. And how i do it....it will take a lot of time
here open again Excel and do a table like this:
Identification Mass SMA ecc inc. Peri node mean
*identification are the name of the objet ( i normally put number 1 for the most far object till number XX (the closest of the star)
PS Keep you accretion disk at pause while taking the information...if not... well you have the number object that will cross the orbit of object number 2 and you will get lost.
PS2: I put all the information of universe sandbox give me even the peri node and mean....it change the orbit a little.
PS3: When i put back to scale i increase the mass by 10 for each objects for the moon mass objects become earth mass objects, earth mass object become jupiter mass object (except that i divide it by 3,18 after the conversion (because you can fit 318 earths mass in jupiter)
PS4: I put back the star to scale so the 0,73 jupiter mass star come back to a 0,73 solar mass star...YOUR ECCENTRICITY WILL GET TO 1 for every objects that are in your accretion disk by doing this. Let it on pause simution till you have all your object back to scale...and don t forget to correct back the eccentricity....or your object will crash into the stars when you ll run the simulation.
PS5: SMA....i convert everything in millions kms and multiply it by 10 ex: An object have a sma of 426 541 km from the ''star'' in the accretion disk....it will become 4 265 410 km to scale....sure you can do X15, X20....its your own choice.
PS6: for dwarf planets (object lower than 999 kms in diameter till 200 km diameter) in the accretion disk thats how i do it.
299 km till 200 km X10 divide by 5
300 km to 499 km X10 divide by 4
500 km to 699 km X10 divide by 3
700 km to 999 km X10 divide by 2
For the density...well thats where your free but normally smaller the mass, smaller the density (for planetary objects protoplanets and dwarfs planets), sure there s execptions...
Of i forgot i reduce the eccentricity and the inclination of planets and dwarfs planets. I reduce them by 35% so i keep only 65% of it....if you want to keep the high ecc of an object well just add it on the number and reduce it after. Ex: 0,80 ecc... i m adding 0,15 so it give me a 0,95....then i pass it in my formula and it give me: 0,6175 for the ecc of the object.
VoilĂ !!! your done!
Topic: Accretion Disk Sandbox (Read 12535 times)
