Neptune is the eighth and farthest known planet from the Sun in the Solar System. It has 14 named moons. In 1989, Neptune’s two innermost moons Thalassa and Naiad were discovered. Thalassa and Naiad orbit only about 1,150 miles (1,850 kilometres) apart. But they never get that close to each other. However, the two Moons of Neptune are found to be locked in ‘dance of avoidance’.
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.
Take a look:
"We refer to this repeating pattern as a resonance," said Marina Brozovic, an expert in solar system dynamics at NASA's Jet Propulsion Laboratory in Pasadena, California, and the lead author of the new paper, which was published November 13 in Icarus.
"There are many different types of 'dances' that planets, moons, and asteroids can follow, but this one has never been seen before," Marina added.
"We suspect that Naiad was kicked into its tilted orbit by an earlier interaction with one of Neptune's other inner moons. Only later, after its orbital tilt was established, could Naiad settle into this unusual resonance with Thalassa," Brozovic said.
"We are always excited to find these co-dependencies between moons," said Mark Showalter, a planetary astronomer at the SETI Institute in Mountain View, California, 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 peace by never getting too close," he added.
It is worth mentioning here that Brozovic and her colleagues discovered the unusual orbital pattern using analysis of observations by NASA's Hubble Space Telescope.
Naiad and Thalassa are small and shaped like Tic Tacs, spanning only about 60 miles (100 kilometres) in length. They are two of Neptune's seven inner moons, part of a closely packed system that is interwoven with faint rings.
Live Scores & Results