I've tried to search out some simple answers, but to no avail. If anyone can either cite some links, or just give a likely answer, I'd appreciate it. 1) In a close binary system with a much further orbiting satellite, can the binary pair be treated as one mass in a rough calculation of the orbit of the satellite? 2) If not, how would you determine the variation in the orbit, to figure out how far out is a stable orbit? 3) Can a rough habitable zone for a binary be determined simply by using the additive luminosities? I'm working on a hypothetical binary system obviously, but most of whatl I find is data on existing binaries and their likelihood of having habitable stars (not that great, btw). Thanks for any help.
You're talking about binary stars, right? The stars both orbit their common center of mass. Any basic astrophysics or astromechanics text will provide you the equations you need. (I can include them here if you want, but math is hard to type on this forum). I don't know what you mean. I assume you mean 'added flux.' The answer is yes. You can sum the flux received from both stars to determine the habitable zone. The fundamental problem is that binary star systems will generally either eat planets, or kick them out of the system almost immediately. I haven't seen any complete analyses of the problem in a long time, but those are the salient points. You can build yourself a computer simulation based on Newton's laws fairly easily. - Warren
New scientist did a story on all sorts of nifty theoretical orbits a while ago. Very cool. Like how 2, 3, 4, and 5 stars might orbit each other in different patterns.
Re: Re: Binary system questions Thanks for the responses, both of you. That was the nature of my first two questions, Warren. If the pair are very close compared to the orbit of the planets, it seems to me that you can treat the pair as one mass equal to their sum. Also, given that the orbital speed of a close pair is much faster than the orbital speed of a planet at habitable zone distances, I had guessed that any disruption should be too brief to affect the stability, but wasn't sure how to mathematically check that. What simulations I have run seem to suggest that as long as the stars are much closer to each other than any of the planets are, it acts as one gravitational source. Further digging has me thinking that while the system itself may work out, the likelyhood of finding such a stable system to support life in the universe would be rare because so many parameters have to be just right.
Re: Re: Re: Binary system questions Very true -- in the limit of infinite distance, the two stars together produce a field indistinguishable from a single point mass at their center of mass. However, any planet that is to be receiving enough radiation from the stars to be habitable is MUCH too close to consider the pair to be one point mass. Very much correct. - Warren
