# That 8-Star System in Star Trek: Picard Really Could Exist - WIRED

WIRED 26 Mar 2020 at 16:55 |

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But you’re thinking the same thing I am: Could an eight-star system exist in the real universe? And if it did, how could the stars be arranged so the system was stable? How would it all move? As Enoch, the navigation hologram, says in the show, “The gravitational mechanics would have to be … incredibly complex.” In other words, we should try to model this thing!

Three’s a Crowd

I should mention that there’s a little physics backstory here—a famous situation called the three-body problem . See, if you have two objects that are gravitationally interacting with each other, like, say, the Earth and the sun, that’s a solvable problem. With a bit of math you can turn it into an equivalent one-dimensional, one object problem. It s complicated, but also seemingly magical. You can get an equation that determines the future position and velocity of both objects for all time.

But it turns out that with three (or more) bodies, there’s no way to derive an equation of motion. To model such a system you have to use a numerical calculation . That’s where you break the trajectories into small time intervals. At each step, you calculate where each object will be at the end of the interval, based on the forces at work, and you just keep doing that till you map out the whole system.

So with three objects, we’d have to calculate the net gravitational force on each object. Remember that the gravitational force is an attractive interaction between two objects with mass. Its magnitude depends on the product of the two masses (let s call them mA and mB), and is inversely proportional to the square of the distance (r) between their centers:

Illustration: Rhett Allain

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So with three objects, there are multiple gravitational forces to calculate. This diagram shows an example of a three-body system, with two stars labeled A and B and a planet labeled P. You can see how each object has two different gravitational forces acting on it. The dotted lines are the momentum vectors.