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Scientists have discovered that the orbital interplay between two of Neptune’s moon keep them close together but never touching. Instead, they dance about each other.
In this perpetual choreography, Naiad swirls around the ice giant every seven hours, while Thalassa, on the outside track, takes seven and a half hours. An observer sitting on Thalassa would see Naiad in an orbit that varies wildly in a zigzag pattern, passing by twice from above and then twice from below. This up, up, down, down pattern repeats every time Naiad gains four laps on Thalassa.
Although the dance may appear odd, it keeps the orbits stable, researchers said.
I have embedded below the fold a video that illustrates this.