The origin of planetary rings

1981 ◽  
Vol 303 (1477) ◽  
pp. 261-279 ◽  
Keyword(s):  
Outer Edge ◽  
Planetary Rings ◽  
Marked Variation ◽  
Saturnian System ◽  
Horseshoe Orbits ◽  
Sharp Edges ◽  
F Ring ◽  
The Stability ◽  
Narrow Ring

Recent spacecraft and ground-based observations have revealed the presence of narrow rings encircling the planets Jupiter, Saturn and Uranus. The Jovian ring is known to contain at least two small, dark, satellites of diameter between 20 and 40 km in its outer edge. The structure of the Saturnian F ring has been resolved by Voyager 1 and appears to be determined by the action of two small neighbouring satellites which were also imaged by the spacecraft. All nine Uranian rings are extremely narrow and some are appreciably eccentric. The outer 6 ring has very sharp edges and its radial width increases from 20 km at pericentre to 100 km at apocentre. This marked variation in width is also characteristic of the Uranian a and |3 rings and of a narrow ring in the Saturnian system. The structure of the Uranian rj ring is complex and may be similar to that of the Saturnian F ring. The resolution of the numerous, but well defined dynamical problems posed by these narrow rings must precede any discussion of the origin of rings. Two co-orbital Saturnian satellites that appear to move in horseshoe orbits have been discovered. The stability of these orbits and the origin of these and other co-orbital satellites are discussed.

scholarly journals Looking for Changes in the Saturnian System Between Voyager and Cassini

1992 ◽  
Vol 152 ◽  
pp. 53-64
Author(s):  
Nicole Borderies
Keyword(s):  
Ring System ◽  
Time Dependent ◽  
Planetary Rings ◽  
Small Satellites ◽  
Irregular Structures ◽  
Saturnian System ◽  
Long Time ◽  
Recession Rates ◽  
F Ring

This paper reviews a number of time-dependent phenomena that are relevant to our understanding of the dynamics of planetary rings and that will be investigated using Voyager and Cassini data. A long time baseline may help us decipher the physics of the spokes, understand better the morphology of the F ring and the rigid precession of non-circular ringlets, measure more precisely than has been done so far the satellites' torques and the viscosity of the A ring, and discover small satellites in the Saturnian ring system. Two exciting possibilities are those of determining the recession rates of the small satellites that border the rings, and of observing changes due to viscous diffusion in the irregular structures of the B ring.

scholarly journals Constraining planetesimal stirring: how sharp are debris disc edges?

2021 ◽  
Vol 503 (4) ◽  
pp. 5100-5114
Author(s):  
Sebastian Marino
Keyword(s):  
Surface Density ◽  
Semimajor Axis ◽  
Rayleigh Distribution ◽  
Outer Edge ◽  
The Other ◽  
Dust Production ◽  
Array Data ◽  
Disc Surface ◽  
Sharp Edges ◽  
Good Agreement

ABSTRACT The dust production in debris discs by grinding collisions of planetesimals requires their orbits to be stirred. However, stirring levels remain largely unconstrained, and consequently the stirring mechanisms as well. This work shows how the sharpness of the outer edge of discs can be used to constrain the stirring levels. Namely, the sharper the edge the lower the eccentricity dispersion must be. For a Rayleigh distribution of eccentricities (e), I find that the disc surface density near the outer edge can be parametrized as tanh [(rmax  − r)/lout], where rmax  approximates the maximum semimajor axis and lout defines the edge smoothness. If the semimajor axis distribution has sharp edges erms is roughly 1.2lout/rmax  or erms = 0.77lout/rmax  if semimajor axes have diffused due to self-stirring. This model is fitted to Atacama Large Millimeter/submillimeter Array data of five wide discs: HD 107146, HD 92945, HD 206893, AU Mic, and HR 8799. The results show that HD 107146, HD 92945, and AU Mic have the sharpest outer edges, corresponding to erms values of 0.121 ± 0.05, $0.15^{+0.07}_{-0.05}$, and 0.10 ± 0.02 if their discs are self-stirred, suggesting the presence of Pluto-sized objects embedded in the disc. Although these stirring values are larger than typically assumed, the radial stirring of HD 92945 is in good agreement with its vertical stirring constrained by the disc height. HD 206893 and HR 8799, on the other hand, have smooth outer edges that are indicative of scattered discs since both systems have massive inner companions.

The formation of sharp edges in planetary rings by nearby satellites

Icarus ◽  
1989 ◽  
Vol 80 (2) ◽  
pp. 344-360 ◽  
Author(s):  
Nicole Borderies ◽  
Peter Goldreich ◽  
Scott Tremaine
Keyword(s):  
Planetary Rings ◽  
Sharp Edges

Sharp edges of planetary rings

Nature ◽  
1982 ◽  
Vol 299 (5880) ◽  
pp. 209-211 ◽  
Author(s):  
Nicole Borderies ◽  
Peter Goldreich ◽  
Scott Tremaine
Keyword(s):  
Planetary Rings ◽  
Sharp Edges

Voyager and the Origin of the Saturnian System

1981 ◽  
Vol 4 (2) ◽  
pp. 164-171 ◽  
Author(s):  
A. J. R. Prentice
Keyword(s):  
Magnetic Forces ◽  
Gravitational Forces ◽  
Keplerian Orbits ◽  
Saturnian System ◽  
Radial Spokes ◽  
The Law ◽  
Electro Magnetic ◽  
F Ring ◽  
Saturn's Rings ◽  
Interparticle Collisions

As Voyager 1 sailed through Saturn’s system of moons and rings last November 1980 it revealed new worlds not seen by man before. For centuries, since Galileo’s first telescopic observations in 1610, the satellites of Saturn had been no more than pin points of light, whilst the structure of the rings was barely resolved beyond 3 principal bands. Yet, within the space of a few hours, that picture changed dramatically as the images of these objects grew through Voyager’s cameras from mere specks into full and wondrous worlds. These pictures contained features that were not only intricate and astonishing in detail but which were, in many cases, unfamiliar and unexpected. A composite view of the Saturnian system as seen by Voyager 1 appears in Figure 1. Saturn’s rings, once thought to be broad belts of particles spread uniformly thin through billions of years of evolution and interparticle collisions, were found to be divided into hundreds of individual ringlets (Figure 2). And Cassini’s Division, a region which had been previously thought to be empty because of a ‘sweeping’ influence of Mimas, was found to contain many ringlets itself! The appearance of light and dark radial spokes in the B ring, which rotated with a velocity contrary to the law expected of Keplerian orbits, was baffling. And the F ring (Figure 3) was found to contain knots, kinks and braids which probably indicated the presence of electro-magnetic forces as well as gravitational forces (Smith et al. 1981).

Processing Methods for Ultra High Temperature Ceramics

2013 ◽  
pp. 180-202 ◽  
Author(s):  
J.K. Sonber ◽  
T.S.R. Ch. Murthy ◽  
C. Subramanian ◽  
R.C. Hubli ◽  
A.K. Suri
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Thermal Protection ◽  
Leading Edge ◽  
Powder Synthesis ◽  
Ultra High Temperature Ceramics ◽  
Sharp Edges ◽  
The Stability ◽  
Intense Heat ◽  
Ultra High Temperature

Ultra-high-temperature ceramics (UHTCs) are a group of materials that can withstand ultra high temperatures (1600-3000 oC) which will be encountered by future hypersonic re-entry vehicles. Future re-entry vehicles will have sharp edges to improve flight performance. The sharp leading edges result in higher surface temperature than that of the actual blunt edged vehicles that could not be withstood by the conventional thermal protection system materials. To withstand the intense heat generated when these vehicles dip in and out of the upper atmosphere, UHTC materials are needed. UHTC materials are composed of borides of early transition metals. From the larger list of borides, ZrB2 and HfB2 have received the most attention as potential candidates for leading edge materials because their oxidation resistance is superior to that of other borides due to the stability of the ZrO2 and HfO2 scales that form on these materials at elevated temperatures in oxidizing environments. Processing of these materials is very difficult as these materials are very refractory in nature. In this chapter, processes available for powder synthesis, fabrication of dense bodies, and coating processes is discussed.

The stability of Saturn's rings

1951 ◽  
Vol 244 (874) ◽  
pp. 1-17 ◽  
Keyword(s):  
Small Particles ◽  
Saturnian System ◽  
Single Ring ◽  
Saturn’S Rings ◽  
The Stability ◽  
Conditions Of Stability ◽  
Saturn's Rings ◽  
Large Primary

Maxwell determined the conditions of stability of a single ring of small particles moving round a large primary. He also made some incomplete remarks on the effects of introducing a second ring. The present investigation considers in greater detail the stability of two rings of particles moving about a primary and subject to the gravitational attractions of the primary and of each other. It is shown that such a system, under conditions satisfied by the Saturnian system, is stable, the particles oscillating finitely about their mean positions. It is inferred that the Saturnian system, considered as a number of such rings, is therefore also stable.

Simulation of collisional transport processes and the stability of planetary rings

Icarus ◽  
1989 ◽  
Vol 78 (1) ◽  
pp. 181-205 ◽  
Author(s):  
Thomas G. Brophy ◽  
Larry W. Esposito
Keyword(s):  
Transport Processes ◽  
Planetary Rings ◽  
The Stability

scholarly journals The teapot effect: sheet-forming flows with deflection, wetting and hysteresis

1994 ◽  
Vol 263 ◽  
pp. 19-62 ◽  
Author(s):  
S. F. Kistler ◽  
L. E. Scriven
Keyword(s):  
Contact Angle Hysteresis ◽  
Liquid Sheet ◽  
Navier Stokes ◽  
Contact Lines ◽  
Element Analysis ◽  
Static Contact ◽  
Sharp Edges ◽  
Surface Profiles ◽  
Flow Transitions ◽  
The Stability

The flow of a two-dimensional viscous film falling from the edge of an inclined plane exhibits a distinctive set of phenomena which, in various combinations, have been referred to as the teapot effect. This paper makes plain that three basic mechanisms are at the root of these phenomena: deflection of the liquid sheet by hydrodynamic forces, contact-angle hysteresis, and multiple steady states that give rise to a purely hydrodynamic hysteresis. The evidence is drawn from Galerkin/finite-element analysis of the Navier-Stokes system, matched to a one-dimensional asymptotic approximation of the sheet flow downstream, and is corroborated experimentally by flow visualization and measurements of free-surface profiles and contact line position. The results indicate that the Gibbs inequality condition quantifies the inhibiting effect of sharp edges on spreading of static contact lines, even in the presence of flow nearby. The branchings, turning points, and isolas of families of solutions in parameter space explain abrupt flow transitions observed experimentally, and illuminate the stability of predicted flow states.

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