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Author Topic: Moons orbit the star instead of the planet  (Read 6400 times)

Basion

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Moons orbit the star instead of the planet
« on: July 12, 2012, 08:37:46 AM »
I'm trying to create a system with a few planets in it. Some of the planets are going to end up having moons. When I try to add a moon, it ends up orbiting around the main star instead of the planet. When I go into edit mode and place the moon, it will orbit the planet which is acting upon it the most. As soon as I start the simulation again, it will switch to orbiting the star. Is this a glitch or am I doing something wrong?

Bla

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Re: Moons orbit the star instead of the planet
« Reply #1 on: July 12, 2012, 08:57:59 AM »
You could try placing the moon closer to the planet, giving the planet more mass, or placing the planet with the moon further away from the star.
Unless it's a bug, it's because the star's gravitational force upon the moon is bigger than the planet's gravitational force. You can turn on "hill spheres" from the options menu. If you place the moon inside the hill sphere around the planet, the moon should orbit the planet.

vh

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Re: Moons orbit the star instead of the planet
« Reply #2 on: July 12, 2012, 08:59:20 AM »
try placing the moon closer to the planet. your moon is probably outside or near outside the hill sphere, which you can show. anything placed outside the hill sphere will orbit the sun and everything placed inside will orbit the planet. you should put the moon close to the planet inside the hill sphere.

hill spheres are a bit buggy so you should place it nearer to the planet than the hill sphere shows.


edit: gahhh ninja'd by fastbla, but ha, i have PICTURES!

hillspheres : http://i.imgdiode.com/X5xoom.png

the panel where you can highlight it: http://i.imgdiode.com/KT64fA.png

Basion

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Re: Moons orbit the star instead of the planet
« Reply #3 on: July 12, 2012, 09:52:55 PM »
Sorry I haven't updated this yet. I ended up falling asleep :s The moon had been within the hill sphere but it looks like the planet may have just been too close to the star. Either way, it's on around day 20 now and so far it's orbiting properly.

icecold12741

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Re: Moons orbit the star instead of the planet
« Reply #4 on: July 15, 2012, 07:59:25 PM »
Actually I am having a similar problem. I'm basically recreating our universe just to get used to the program. I can make all the planets fine with the proper rotational times (i.e. Earth is 1 year, Mars is 686.9 days, etc) and the orbits are stable but when I try to create Earth's moon and set the rotation around Earth to 27.3 days it shoots ahead and sets its own orbit around the sun at 364 days. Any ideas?

Darvince

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Re: Moons orbit the star instead of the planet
« Reply #5 on: July 15, 2012, 08:15:09 PM »
Turn the timestep lower also.