Celestia Forums

Hello together

I tried several times to create an own Doublestar-System. I guess the main function of Celestia is to create one sun as a center of gravity, where several planets (and their moons) can swing around. My idea was now to create a "invisible point-like" dark sun as the center of gravity using a common stc-file. But how to do that? Can I create it without using the SpectralType-parameter? Or should I use an invalid Type there?

So does anyone have an idea how to create a gravity center without a sun?

The next step would be to create two planets orbiting this (hopefully invisible) center. These planets can be established as two suns (<Texture "white-dwarf.jpg"> and <Emissive True>). That's no problem, I allready have a star with a White Dwarf as a planet.

Another problem are the planets. It's no problen to establish planets orbiting each sun allone. I also created a planet orbiting both suns. But: This planet circles around the gravity center. So it's speed allways will be the same (<EllipticalOrbit>-parameter in ssc-file). But the speed is varying while orbiting around two different suns.

I hope I explained my problem understandable as possible.

Ernie from Germany[/code]

Ernie wrote:My idea was now to create a "invisible point-like" dark sun as the center of gravity using a common stc-file. But how to do that? Can I create it without using the SpectralType-parameter? Or should I use an invalid Type there?

Set the AbsMag parameter very high for your "invisible" star - this makes it very dim, and Celestia will therefore make it very small, so that it's invisible unless you go to it deliberately.

Ernie wrote:But: This planet circles around the gravity center. So it's speed allways will be the same (<EllipticalOrbit>-parameter in ssc-file). But the speed is varying while orbiting around two different suns.

No reason why the planet can't be in a standard EllipticalOrbit. Admittedly there will be perturbations because of the two masses at the centre, but if the planet is far enough out to be in a long-term stable orbit, an EllipticalOrbit definition won't be obviously wrong.

Grant

Hello Grant!

Thanks for the tip. I think I got the idea. I really got a G2-sun which is visible only between a distance from 0.2 m to 1000 m. The <AbsMag> is set to 65.0 (maybe I'll try values up to 100). That's good, so nobudy can see this "virtual" sun. A wonderfull point of gravity, where the other suns can orbit around.

The only what I have to do now is to calculate the mass of my stars, their distance to the gravitycenter and their speed. They must have the same time for one revolution, so they have different speeds. Let's see, if I can find somethimg in another forum for it.

Ernie