As the outermost planet (sorry Pluto), Neptune is one of the most mysterious bodies in the solar system. Astronomers are conducting more research to discover some of the secrets that the planet and its moons hold. Now, a new study has detailed the delicate dance that two of the Neptunian moons exhibit to avoid destroying one another, Universe Today reports.
Voyager 2 discovered the moons Naiad and Thalassa when it made its flyby of Neptune in 1989. The moons skew on the small side, each about 60 miles across. They represent two of the seven so-called inner moons. Naiad and Thalassa’s orbits lie about 1,150 kilometers from each other. That’s extremely close quarters in celestial body terms.
‘Dance of Avoidance’
Still, the two moons never really come that close to each other due to what scientists call a “dance of avoidance.” To keep from smashing each other to pieces, Naiad’s orbit tilts by about five degrees with respect to Thalassa’s. This gives Naiad a wave-like path. When viewed from outside the system, it looks like Naiad is nimbly leaping over Thalassa or ducking underneath it.
“We refer to this repeating pattern as a resonance,” study lead author Marina Brozovic of NASA’s Jet Propulsion Laboratory said in a statement. “There are many different types of dances that planets, moons and asteroids can follow, but this one has never been seen before.” The team published a paper with its findings in the journal Icarus.
Brozovic and her colleagues made the discovery using data collected by Voyager 2, Earth telescopes, and the Hubble Space Telescope. Sifting through the data collected between 1981 and 2016 helped researchers better understand the strange Neptunian system.
Rubble Roller Rink
Neptune’s biggest moon, Triton, rules over the system. It’s thought that Triton originated in the Kuiper Belt, the icy asteroid field that surrounds the solar system. Neptune then captured the dwarf planet.
Researchers came to this conclusion because Triton behaves strangely compared to other moons. Chiefly among these odd posturings is the fact that Triton orbits in retrograde, or opposite of Neptune’s rotation.
As a large newcomer, Triton naturally wreaked havoc on the Neptunian system. It sent Neptune’s existing moons into chaos, smashing them into each other and turning the system into a rubble roller rink.
An Old Married Couple
This is why, researchers suggest, Neptune’s smaller moons—including Naiad and Thalassa—are more asteroid-like than moon-like. For one, they aren’t spherical like bigger moons. Moreover, they consist of loosely connected boulders and ice as opposed to solid rock.
Yet the question remains, how did Naiad and Thalassa settle into their unique orbits?
Researchers believe that Naiad moved into its close orbit with Thalassa after an interaction with a fellow inner moon. Naiad then had to “learn” to live with Thalassa, like an old married couple who look past each other’s annoying tendencies, by settling into its tilted orbit.
“Naiad and Thalassa have probably been locked together in this configuration for a very long time, because it makes their orbits more stable,” study co-author Mark Showalter said. “They maintain the peace by never getting too close.”