Ring Arc Closeup (QuickTime (MOV) format, 2.1 Mbytes).
This animation zooms in on one of Neptune's ring arcs. The "rope-like" structure is caused by smear, since the clumps moved significantly while the the camera shutter was open.
Broken ring arcs
Mean Distances of the Jovian Planets from Sun
Orbits are drawn approximately to scale.
Pluto omitted to accommodate scale.
The Rings and "Ring Arcs"
As Voyager 2 approached Neptune, scientists had been working on theories of how partial rings, or ring arcs, could exist.
The thicker part of the rings are called ring arcs; these are the parts of the rings that are more easily detected. The Adams ring has three prominent arcs (named Liberty, Equality and Fraternity).
This inconsistent result is due to the presence of not only rings but also ring arcs, which are thicker parts of rings.
From Earth, astronomers had only detected the merest hint of ‘ring arcs', rather than full rings, and speculation was rife as to how ring arcs could form.
Other simulations of an observed dust disk ring arc at 95 AUs also suggested that there may be a sub-Jovian planet between 90 to 100 AUs out from Vega.
This gave rise to the speculation that Neptune had a series of partial rings (ring arcs) occupying 10 percent or less of their orbit(s).
Taidakova (Schafer Corporation) of an observed dust disk ring arc at 95 AUs also suggested that there may be a sub-Jovian planet between 90 to 100 AUs out from Vega.
In the fourth image pair, Epimetheus, in the lower right corner, streaks towards Saturn. The long ring arc can be seen in both frames.
The fifth image pair again captures Mimas, beyond the tip of the F Ring. The same ring arc is still visible.
The ring arcs turned out to be bright patches on one ring. Two other rings, and 6 other satellites, were discovered. Neptune's magnetic axis was also skewed. Triton had a canteloupe appearance and geysers. (What's liquid at 38K?) ...
© NASA/JPL-Caltech Observations from the Earth had shown that Neptune possessed some ring arcs; the Voyager pictures showed that there are at least 4 rings and many dust particles were detected in the plane of the rings.
Voyager found four complete rings around Neptune, but no partial ring arcs. The fine material in the rings is so diffuse they cannot be seen from Earth.
Solar System:
The Sun ...
Neptune's ring arcs were discovered to be bright patches on one ring. Voyager 2 discovered two more rings, and six more moons. Triton, a moon, was found to be cantaloupe-shaped and to have geysers.
These three moons orbit between Mimas and Enceladus: Methone,Anthe, and Pallene. Both Methone and Anthe possess faint ring arcs. A very faint ring has also been detected in Pallene's orbit. ref[1]
[edit] Trojan moons
Main article: Trojan moon ...
sextant: a navigational instrument for measuring celestial angles, particularly the height (altitude) of the sun or fixed stars. So named because its measuring arc is a sixth of a circle; ...
Rings are narrow, and contain
concentrations of particles
called ring arcs.
Resonances with Galatea in the ratio 42:43 are also considered the most likely mechanism for confining the unique ring arcs that exist in is ring . Galatea's mass has been estimated based on the radial perturbations it induces on the ring .
1989, which discovered six new and a set of ring arcs. Neptune is the windiest planet in the solar system, with wind speeds of 600 m s-1 ( Mach 1 at 59 K). The rings of Neptune are designated 1989N3R, 1989N2R, 1989N4R, and 1989N1R.
This had been attributed to ring arcs, but when Voyager 2 observed Neptune in 1989, it was found to have been caused by the moon. Five new irregular moons discovered between 2002 and 2003 were announced in 2004.
 See also: Orbit, Rings, Neptune, Planet, Solar System
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