Thursday, April 16

What shape does a planet orbiting
two suns make?

There are many possible orbital shapes that a planet can make in a binary star system. It depends on the masses of the two stars, their separation, the mass of the planet, its distance from each star and whether it is orbiting one star in the pair or both. At sufficient distances the planet will revolve around both stars in an elliptical orbit. Closer in, the orbit may be squashed into various shapes that slowly change orientation, much like the patterns you get from a Spirograph. There are even orbits that trace out long sausage shapes or the petals of a flower, or cross periodically between the two stars. Complex orbits such as these may be rare, since many of them are inherently unstable and would soon break down. Figure-of-eight orbits are not possible.

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