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JPL: Neptune Moons Locked in 'Dance of Avoidance'

Posted: Sat Nov 16, 2019 5:05 pm
by bystander
Neptune Moons Locked in 'Dance of Avoidance'
NASA | JPL-Caltech | 2019 Nov 14
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Neptune Moon Dance ~ Credit: NASA/JPL-Caltech
Even by the wild standards of the outer solar system, the strange orbits that carry Neptune's two innermost moons are unprecedented, according to newly published research.

Orbital dynamics experts are calling it a "dance of avoidance" performed by the tiny moons Naiad and Thalassa. The two are true partners, orbiting only about 1,150 miles (1,850 kilometers) apart. But they never get that close to each other; Naiad's orbit is tilted and perfectly timed. Every time it passes the slower-moving Thalassa, the two are about 2,200 miles (3,540 kilometers) apart.

In this perpetual choreography, 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.

Although the dance may appear odd, it keeps the orbits stable, researchers said. ...

Orbits and Resonances of the Regular Moons of Neptune ~ Marina Brozovic et al

Re: JPL: Neptune Moons Locked in 'Dance of Avoidance'

Posted: Sat Nov 16, 2019 6:35 pm
by neufer
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"Thalassa" is the Greek word for "sea".

The Naiads (Greek: Ναϊάδες) are a type of female spirit, or nymph, presiding over fountains, wells, springs, streams, brooks and other bodies of fresh water. Ναϊάς derives from νάειν (náein), "to flow", or νᾶμα (nãma), "running water"