Right now I'm writing a sci-fi story that develops in a double planet. But that's not all, the double planet (along with a couple more planets) orbit a big star and the whole system is orbited by another star (about 100 AU from the central star.)
I need to know how implausible this is. I don't want my story to drift from speculation into impossible worlds. I'm guessing that the occurrence of such a planetary arrangement is very low likely, but is such a system even possible at all?
Now, if it's possible, how messed up the days and seasons would be? I'm bending my brain to figure out what would be the length of day and night in such a system (the planets are very close to each other.)
Any help with this will be really appreciated.