See how the odd orbits 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.


The Voyager 2 spacecraft discovered Neptune moons Naiad and Thalassa in 1989.

The moonlets are only about 60 miles (100 km) wide.

If we race along with Thalassa around Neptune, Naiad appears to be moving in a wave-like pattern.

That's because, compared to Thalassa, Naiad's orbit is tilted by about five degrees.

It takes about seven hours to complete the orbits

Naiad spends half of each orbit above Thalassa and half below.

If we plot multiple orbits, we see Naiad in a constant dance with Thalassa.

This is called a resonance.

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