Researchers at NASA have discovered that a unique orbiting pattern by Neptune's two innermost moons allows them never to collide, dubbing it a "dance of avoidance".

The moons' unique orbit "has never been seen before" according to Marina Brozovic, the lead author of a new paper.

"There are many different types of 'dances' that planets, moons and asteroids can follow, but this one has never been seen before," added Dr Brozovic.

Image: Diagram shows Neptune's moons. Pic: NASA/ESA and A Feild

Neptune has 14 confirmed moons, with the most recent being discovered in 2013 and then ultimately named Hippocamp this year.

The most distant is Neso, which orbits the ice giant in an enormous loop which takes it 27 years to complete.


The two innermost moons, Naiad and Thalassa, are much smaller, and oblate rather than spheroid. They orbit the planet every seven and seven-and-a-half hours respectively.

They are very close to each other, orbiting only about 1,150 miles (1,850km) apart - about the distance between the UK and Finland.

But despite that being the average distance of their orbits, they never actually get that close to each other.

This is due to a tilt in Naiad's orbit which is perfectly synchronised with Thalassa's orbit, meaning the moon appears to wobble around its fellow moon.

Image: Naiad and Thalassa are Neptune's innermost moons

"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," said NASA.

"We refer to this repeating pattern as a resonance," explained Dr Brozovic.

"We are always excited to find these co-dependencies between moons," said Dr Mark Showalter, a planetary astronomer at the SETI Institute, and a co-author of the new paper.

"Naiad and Thalassa have probably been locked together in this configuration for a very long time, because it makes their orbits more stable.

"They maintain the peace by never getting too close."