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Kepler Orrery

Posted: Tue Dec 01, 2015 5:09 pm
by Cody
A Kepler Orrery - and the source code is here.

Re: Kepler Orrery

Posted: Sun Feb 21, 2016 1:20 pm
by RockDoctor
Cody wrote:
A Kepler Orrery - and the source code is here.
That's an interesting project (almost certainly out of date by the time he stopped downloading data and started coding ... but that's astronomy for you).
An orrery for the current planet system would be an interesting, particularly in the more complex systems.
I haven't checked (I don't have a system with a graphics card adequate for the 1.8 systems any more) recently, but ... do the multi-planet systems have a vaguely realistic ecliptic and distribution of planets within that plane? It's not an absolute bound (the Solar system has about a 7 degree spread for the 8 known planets, with one of the oddities of Pluto being it's 17 degree inclination). I'm going to guess that planets are on circular orbits simply to make the maths easier.
Double Stars
This paper from a few years ago is, as yet, not disagreed with by observations. You can orbit stably outside the binary star if your orbit semi-major axis is more than about 3 times the (maximum) separation of the two stars ; within the binary (i.e. orbiting one but not both stars) things get much more unstable, and if you get more than 4AU from either star, you're likely to become unstable. COROLLARY : this is for large-separation binaries. For a planet at 4AU to get an Earth-like irradiation, you'd need ~16 times the solar flux, which is getting you up into stars of several solar masses and not long enough lifetimes to allow natural evolution of life.
So, multiple-star systems are going to be so close together that you're playing with significant interstellar mass transfer (there are PhDs waiting for people who write code for such systems), or you're looking at systems with separations far larger than our solar system. Which might be visually spectacular, but trading-wise might as well be separate systems. I note a number of systems in the Classical game which are on spacings like 0.1Ly or so, which may be modelled on Alpha-Beta Centauri.