Neptune Moon Dance (animation)

See how the odd orbits of Neptune’s inner moons Naiad and Thalassa enable them to avoid each other, as they race around the planet. Researchers call it a “dance of avoidance.“ An observer sitting on Thalassa would see Naiad in an orbit that varies wildly in a zig-zag 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. This repeating pattern is called a resonance. Marina Brozović, lead author of the new analys