Astronomers have discovered an unusual pattern around Neptune. The gas giant’s innermost moons are doing everything in their power to steer clear from one another in a weird, zigzagging pattern that astronomers are calling a “dance of avoidance.”
Thalassa and Naiad’s orbital paths sit no farther apart than Chicago and Miami, about 1,150 miles (1,850 kilometers). But their zigzagging path around each other as they orbit Neptune ensures that the moons themselves never get that close. Naiad moves faster than Thalassa, circling Neptune in 7 hours versus its twin’s orbital time of 7.5 hours. Every time Naiad passes the slower moon, which is when the two would otherwise veer close together, they are in a distant spot in their zigzag dance. At that point, they’re about 2,200 miles (3,540 km) apart, or the distance from Chicago to Costa Rica.
This bizarre dance results from a resonance in the twins’ orbits that keeps the moons stable as they whirl above Neptune’s frigid, blue clouds.