Concluding remarks on the planetary rings conference

International Astronomical Union Colloquium ◽

10.1017/s0252921100101897 ◽

1984 ◽

Vol 75 ◽

pp. 763-767

Author(s):

E.C. Stone

Keyword(s):

Data Analysis ◽

Planetary Rings ◽

Theoretical Interest ◽

Ring Systems ◽

The Past ◽

Saturn’S Rings ◽

Key Aspects ◽

Saturn's Rings ◽

Observational Program

ABSTRACTIn the past five years ring systems have been discovered around Uranus and Jupiter and a wealth of new data acquired about Saturn’s rings. This vigorous observational program has been accompanied by renewed theoretical interest in ring systems. Although all of these topics have been addressed in papers at this first conference on planetary rings, these concluding remarks are focused on some of the key aspects of Saturn’s rings about which more needs to be understood through further data analysis, calculations, and observations.

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Comments on collision mechanics in ring systems

International Astronomical Union Colloquium ◽

10.1017/s0252921100101472 ◽

1984 ◽

Vol 75 ◽

pp. 407-422

Author(s):

William K. Hartmann

Keyword(s):

Asteroid Belt ◽

Surface Erosion ◽

Surface Layers ◽

Ring Systems ◽

Eclipse Observations ◽

Saturn’S Rings ◽

Saturn's Rings

ABSTRACTThe nature of collisions within ring systems is reviewed with emphasis on Saturn's rings. The particles may have coherent icy cores and less coherent granular or frosty surface layers, consistent with thermal eclipse observations. Present-day collisions of such ring particles do not cause catastrophic fragmentation of the particles, although some minor surface erosion and reaccretion is possible. Evolution by collisional fragmentation is thus not as important as in the asteroid belt.

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Making Better Planetary Rings: Particles colliding in Saturn's rings appear to be ice balls, not snowballs, acting like molecules of a gas, a liquid, and perhaps even a solid

Science ◽

10.1126/science.229.4720.1376 ◽

1985 ◽

Vol 229 (4720) ◽

pp. 1376-1377 ◽

Cited By ~ 3

Author(s):

R. A. KERR

Keyword(s):

Planetary Rings ◽

Saturn’S Rings ◽

Saturn's Rings

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A review of radar observations of Saturn’s rings

International Astronomical Union Colloquium ◽

10.1017/s0252921100100995 ◽

1984 ◽

Vol 75 ◽

pp. 49-55 ◽

Cited By ~ 1

Author(s):

Steven J . Ostro ◽

Gordon H. Pettengill

Keyword(s):

Ring System ◽

Radar Observations ◽

Jet Propulsion ◽

Tracking Station ◽

The Past ◽

Microwave Radar ◽

Radar Echoes ◽

Saturn’S Rings ◽

Saturn's Rings ◽

Arecibo Observatory

Saturn’s rings are the most distant radar-detected planetary entity, and the only radar-detected ring system. Neither distinction is likely to be reinquished during this century.Ten years have passed since the initial detection of radar echoes from Saturn’s rings (Goldstein and Morris, 1973) shattered prevailing notions that typical ring particles were 0.1 to 1 mm in size. (The single fact that microwave radar echoes are detectable requires a substantial density of particles larger than about one centimeter.) During the past decade, additional radar studies of the rings have been conducted, using the λ13.5-cm and λ12.6-cm systems at the Jet Propulsion Laboratory’s Goldstone Tracking Station and the λ112.6-cm system at the National Astronomy and Ionosphere Center’s Arecibo Observatory.

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Origin and Evolution of Saturn’s Rings

Highlights of Astronomy ◽

10.1017/s153929960000544x ◽

1983 ◽

Vol 6 ◽

pp. 435-442

Author(s):

G.E. Morfill

Keyword(s):

Ring System ◽

Planetary Rings ◽

Subsequent Evolution ◽

Origin And Evolution ◽

Saturn’S Rings ◽

Saturn's Rings

AbstractThe formation of planetary rings is discussed in the context of formation theories of the gaseous planets. The subsequent evolution of Saturn’s ring system, both dynamically and mechanically, is described, and the consequences are compared with observations.

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Voyager UVS observations of stellar occultations by the rings of Saturn

International Astronomical Union Colloquium ◽

10.1017/s0252921100101265 ◽

1984 ◽

Vol 75 ◽

pp. 265-277

Author(s):

J.B. Holbelg ◽

W.T. Forrester

Keyword(s):

Optical Depth ◽

Distance Scale ◽

Density Waves ◽

Ring Density ◽

Stellar Occultations ◽

Saturn’S Rings ◽

Saturn's Rings

ABSTRACTDuring the Voyager 1 and 2 Saturn encounters the ultraviolet spectrometers observed three separate stellar occultations by Saturn's rings. Together these three observations, which sampled the optical depth of the rings at resolutions from 3 to 6 km. can be used to establish a highly accurate distance scale allowing the identification of numerous ring features associated with resonances due to exterior satellites. Three separate observations of an eccentric ringlet near the location of the Titan apsidal resonance are discussed along with other ringlet-resonance associations occurring in the C ring. Density waves occurring in the A and B rings are reviewed and a detailed discussion of the analysis of one of these features is presented.

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Remaking Retirement

10.1093/oso/9780198867524.001.0001 ◽

2020 ◽

Keyword(s):

Interest Rates ◽

Older Workers ◽

Older Persons ◽

The United States ◽

Older Population ◽

The Past ◽

Cost Of Education ◽

The World ◽

Low Interest Rates ◽

Key Aspects

Around the world, people nearing and entering retirement are holding ever-greater levels of debt than in the past. This is not a benign situation, as many pre-retirees and retirees are stressed about their indebtedness. Moreover, this growth in debt among the older population may render retirees vulnerable to financial shocks, medical care bills, and changes in interest rates. Contributors to this volume explore key aspects of the rise in debt across older cohorts, drill down into the types of debt and reasons for debt incurred by the older population, and review policies to remedy some of the financial problems facing older persons, in the United States and elsewhere. The authors explore which groups are most affected by debt, and they also identify the factors causing this important increase in leverage at older ages. It is clear that the economic and market environments are influential when it comes to saving and debt. Access to easy borrowing, low interest rates, and the rising cost of education have had important impacts on how much people borrow, and how much debt they carry at older ages. In this environment, the capacity to manage debt is ever more important as older workers lack the opportunity to recover for mistakes.

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