Can two stars orbit each other but each have their own planets in stable orbits?
I'm aware that 'tatooine' worlds don't make good habits for planets, normally. From what I've read, either a planet has to orbit one star really closely, or orbit both stars from a really long distance away.
I envisioned a kind of double solar system, where there are two stars that are close enough to orbit one another, but far enough away where they can each have planets of their own.
In such a situation, its possible to have habitable worlds orbiting both stars, but they would be conceivably close enough where intelligent life from these worlds could potentially have some awareness of each other, and possible communication, even with our own current level of technology.
Of course, orbital calculations are beyond me, and from my understanding would require a supercomputer to work out. I don't believe I've ever heard of an actual 'double solar-system' like this, which would lead me to believe that such a thing is not possible.
If it matters, I wasn't thinking of either of these stars as having that many planets. The stars are close enough where outer-planets like in our system simply can't exist. And one only has one planet: a gas giant, with multiple habitable moons. The other is more like our solar system (well, inner solar system anyway, there's only 3 or 4 planets).
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1 answer
Yes, and the planets can orbit in the habitable zones.
This page gives a long list of planets in these S-type orbits, and states
For a few systems (2 so far), there are planets orbiting each member of the binary. In this case, the system is divided into two "binaries", one where the first star is the "central star" and the other star is the perturbing companion, and another one where the roles are reversed.
It's important to note that many of the planets in S-type orbits are quite close to the main star they orbit, meaning that the influence from the other star is small, and the orbit is stable over reasonably timescales. This shouldn't preclude a planet from orbiting the other star in the system.
One thing that's worth noting is that binaries where S-type orbits are possible usually have a large separation - that is, the stars are pretty far apart. This makes it possible for the planets to be in a larger range of orbits, meaning they aren't restricted to orbiting close to one star. Therefore, in wide binaries, it's more likely that a planet could orbit in the habitable zone of one of the stars.
Examples I've been able to find (to be updated):
- WASP-94, a pair of F-type main sequence stars, each with a close hot Jupiter orbiting it.
- HD 20781/HD 20782, two G-type stars, each with 1-2 planets (one at 1.3 AU orbiting HD 20782, two at <1 AU orbiting HD 20781).
- Kepler-132, a pair of G-type main sequence stars, although the structure of the system has been disputed.
- XO-2, two cool K-type stars, with a confirmed hot Jupiter around one star and two possible planets around the other.
I've found these by perusing a list of exoplanets in binary systems and doing some cross-checking. Doing some simulations of the HD 20781/HD 20782 system indicates that it should certainly be habitable. The two stars are separated by ~9000 AU, both are G-type stars like the Sun, and stable orbits exist around 1 AU, in the habitable zones of the star. The same goes for the other systems, which also have extremely large binary separations.
To make a long story short, yes, this will work.
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