Double-star planetary systems

[Lester Curtis]

One of my characters (Raiehth) hails from a planet that orbits a double star, and I'm seeking technical advice from anyone here who can help; I think this is a question about astrophysics.

Below is a short clip taken from the story.

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"I was wondering about that twenty-hour shift in your contract, and then I started wondering what your sleep cycles are like."

"My homeworld, Kait, orbits double star. Small blue star, goes around big red star. Very pretty. Lots of daylight, although. Our day is longer than yours, and it changes. Sunrise may be blue star, red star, maybe red star, blue star, may be just red star, if blue one is in front or behind of it. Not much night, irregular. We don't sleep much, work a long time. In contract, one shift on, one off. No overtime. Sleep, about half of shift, some less."

"Huh. I'm sure the contractors like that. Kait probably has a pretty long year, am I right?"

"Yes, long year . . . long orbit, very elliptical. Year is getting shorter, though."

"Hm??"

"Our blue sun is falling into the red one. They get closer, spin faster . . . center between their gravities is moves in circles, faster. Planets falling into, orbit faster getting close in."

"Aw, man . . . "

"Worse, gravities from suns make unstable orbits of the planets. Inner planet is falling in fast now. Our planet, second planet, is beginning to have seasons change. Plus more eruptions of melten rock. Gravity of suns -- squeezes our planet."

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Putting aside the possible cause of the impending catastrophe, how close have I gotten to describing something that could actually exist?
I suspect that I'm pretty far off with the part about how quickly the two stars orbit each other, but any comments would be helpful.

Note: the "very elliptical" orbit isn't really -- it's just not quite as circular as ours. There are limits there, of both system stability and survivable conditions; I just don't know what they are.

[Robert_Moriyama]

My first thought is that the planet must orbit one or the other (the red giant or the smaller blue star), with the distance between the planet and its host star small compared to the distance between the two stars. This is the sort of arrangement that would make for some very weird daily and "annual" (trip around the host star) effects. Depending on the orbital positions of the three bodies, for part of the year, a given location on the planet would see only one of the two stars in the sky at a time; at other times, both stars would be visible in the sky with the apparent distance between them varying over the course of the year. True night, with neither star visible above the horizon, would be shorter than would be the case with a single star and the same degree of axial tilt...

While your character's description of circumstances presumably is based on fairly sophisticated knowledge of orbital mechanics, I'm not sure if his(?) comments on the apparent visual impression for someone on the ground would be true.

Bill? Any astronomy / orbital mechanics experts out there?

RM

[Lester Curtis]

The character in question is a well-trained space pilot, but I can only equip him with my own limited knowledge . . .

I think I saw something on TV about planets orbiting double stars; I had the impression that the planet would orbit both. Given the mass of stars, though, it does seem unlikely that they'd be that close (for any length of time, at least).