(computer science) A cyclic arrangement of data elements, usually including a specified entry pointer.
(design engineering) A tie member or chain link; tension or compression applied through the center of the ring produces bending moment, shear, and normal force on radial sections.
(mathematics) An algebraic system with two operations called multiplication and addition; the system is a commutative group relative to addition, and multiplication is associative, and is distributive with respect to addition. A ring of sets is a collection of sets where the union and difference of any two members is also a member.
(organic chemistry) A closed loop of bonded atoms in a chemical structure, for example, benzene or cyclohexane.
ring
| Sci-Tech Dictionary: ring |
(riŋ)
| 5min Related Video: ring |
| Sci-Tech Encyclopedia: Ring |
A tie member or chain link. Tension or compression applied through the center of a ring produces bending moment, shear, and normal force on radial sections. Because shear stress is zero at the boundaries of the section where bending stress is maximum, it is usually neglected.
| Computer Desktop Encyclopedia: ring |
A privilege level in the computer. When software is assigned to a ring, it may be limited to executing certain instructions in the computer. Ring 0 has the highest privilege and can access all instructions. The operating system or the virtual memory monitor (VMM) resides in ring 0.
Applications typically reside in ring 3, which has a lower priority, and are prohibited from executing instructions that address the hardware. If an application attempts to execute a prohibited instruction, an error indication (fault) is generated. Rings 1 and 2 are available in some computers, but may or may not be used. See virtual machine monitor.
Download Computer Desktop Encyclopedia to your iPhone/iTouch
| Columbia Encyclopedia: ring |
ring, in astronomy, relatively thin band of rocks and dust and ice particles that orbit around a planet in the planet's equatorial plane. All four of the giant planets in the solar system-Jupiter, Saturn, Uranus, and Neptune- have rings, although only those of Saturn are easily visible. The origin of the rings is unknown. One theory is that they may have been formed from moons that were shattered by the impact of comets and meteoroids. Another holds that they might be the remnants of moons or comets that came within the planet's Roche limit and were broken up by gravitational forces.
Saturn has seven rings designated alphabetically as A through G in the order of their discovery; two additional rings, designated as R/2004 S1 and R/2004 S2 were discovered in images returned to earth from the Cassini space probe in 2004. From the planet outward, the rings are D, C, B, A, R/2004 S1, R/2004 S2, F, G, and E. With named gaps occupying the space between several of the rings, Saturn's rings are a highly complex structure stretching almost 167,770 mi (270,000 km) from the planet's center to the farthest edge of ring E. The rings are not perfectly circular, and the gaps are not completely empty. The Columbo and Maxwell Gaps separate the C and B rings, the Cassini Division and Huygens Gap separate the B and A rings, and the Encke Division and Keeler Gap separate the A and R/2004 S1 rings. Except for the A and B rings, which are separated primarily by the 2,920-mi-wide (4,700-km) Cassini Division, the rings are relatively close to one another. The rings appear to be composed of small pieces of water ice mixed with a small amount of rocky material in a wide range of particle sizes, from 1 in. (2.5 cm) to 33 ft (10 m)-although there may be an occasional object as large as a mile (1.6 km) in diameter. Data returned by Cassini indicates that the rings are not uniform; for example, the B ring is very different from the A and C rings (which are similar to one another) found on either side of it. Several of Saturn's small moons appear to be shepherd satellites, maintaining the shape of the rings through gravitational interactions, and there are also ring arcs associated with several moons.
Jupiter's rings are similar to those of Saturn but much smaller and fainter. The main ring is about 4,300 mi (7,000 km) wide and has an abrupt outer boundary 80,000 mi (128,940 km) from the center of the planet. The inner main ring is formed from dust and ice particles kicked up when meteoroids collide with the small Jovian satellites Metus and Adrastea. The particles then spiral slowly in toward Jupiter. At its inner edge the main ring merges into the halo. A broad, faint band of dust and particles, the halo is about 6,200 mi (10,000 km) thick and stretches halfway from the main ring down to the top of Jupiter's atmosphere. A pair of broad, faint gossamer rings are located just outside the main ring, one bounded by the orbit of the Jovian shepherd satellite Amalthea and the other by the orbit Thebe.
Uranus has a thin elliptical band of eleven faint, narrow rings composed of ice, rock, and dust. Stretching outward from the planet, the rings are named 1986 U2R, Six, Five, Four, Alpha, Beta, Eta, Gamma, Delta, 1986 U1R, and Epsilon; the distance from the planetary center to the Epsilon ring is 31,750 mi (51,140 km). The rings are distinctly different from those of Jupiter and Saturn. A tenuous distribution of fine dust is scattered throughout the ring system, and the rings all are the same flat, dark color (perhaps from methane or black-carbon ice coating the rock), unlike Saturn's bright rings. The nine main rings consist of a single layer of particles, the monolayer, which had not previously been seen in planetary rings; the particles are kept from drifting away by several shepherd satellites. Because there are ringlets and incomplete rings and a varying opacity in several rings, it is believed that the Uranian ring system may be the remnants of a small moon.
Neptune has four almost circular faint rings composed of small rocks and dust. The rings are not uniform in density and thickness; the thicker parts of the rings are called ring arcs. Stretching outward from the planet, the rings are named Galle, Leverrier (whose outer extension is called Lassel), Arago, and Adams (which includes the ring arcs Liberty, Equality, and Fraternity); the distance from the planetary center to the Adams ring is 39,000 mi (62,930 km). The forces responsible for the development of ring arcs and ring extensions are not well understood, but shepherd satellites and gravitational forces attributable to Neptune's moons are thought to play a significant role. Earth-based observations indicate that the rings are less stable than was originally believed.
| Intelligence Encyclopedia: Ring |
A group or network.
| Wikipedia: Planetary ring |
"Shepherd moon" redirects here. For the Enya album, see Shepherd Moons.
Not to be confused with the Dreamcast game "Planet Ring", see List of Dreamcast games
A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in a flat disc-shaped region. The most spectacular planetary rings known are those around Saturn, but the other three gas giants of the solar system (Jupiter, Uranus and Neptune) possess ring systems of their own.
Recent reports[1][2][3] have suggested that the Saturnian moon Rhea may have its own tenuous ring system, which would make it the only moon known to possess a ring system.
Contents |
Overview
There are three ways that planetary rings (the rings around planets) have been proposed to have formed: from material of the protoplanetary disk that was within the Roche limit of the planet and thus could not coalesce to form moons; from the debris of a moon that was disrupted by a large impact; or from the debris of a moon that was disrupted by tidal stresses when it passed within the planet's Roche limit. Most rings were thought to be unstable and to dissipate over the course of tens or hundreds of millions of years, but it now appears that Saturn's rings might be quite old, dating to the early days of the Solar system.[4]
The composition of ring particles varies; they may be silicate or icy dust. Larger rocks and boulders may also be present, and in 2007 tidal effects from eight 'moonlets' only a few hundred meters across were detected within Saturn's rings.
Sometimes rings will have "shepherd" moons, small moons that orbit near the outer edges of rings or within gaps in the rings. The gravity of shepherd moons serves to maintain a sharply defined edge to the ring; material that drifts closer to the shepherd moon's orbit is either deflected back into the body of the ring, ejected from the system, or accreted onto the moon itself.
Several of Jupiter's small innermost moons, namely Metis and Adrastea, are within Jupiter's ring system and are also within Jupiter's Roche limit.[5] It is possible that these rings are composed of material that is being pulled off of these two bodies by Jupiter's tidal forces, possibly facilitated by impacts of ring material on their surfaces.
Neptune's rings are very unusual in that they first appeared to be composed of incomplete arcs in Earth-based observations, but Voyager 2's images showed them to be complete rings with bright clumps[6]. It is thought[7] that the gravitational influence of the shepherd moon Galatea and possibly other as-yet undiscovered shepherd moons are responsible for this clumpiness.
Pluto is not known to have any ring systems. However, some astronomers think that the New Horizons probe might find a ring system when it visits in 2015.[8]
It is also predicted that Phobos, a moon of Mars, will break up and form into a planetary ring in about 50 million years due to its low orbit.[9][10]
After the impact of Theia and before the coalescence of the Moon, it is generally assumed[citation needed] that the Earth had a ring system.
History of Earth rings
 |
This article's factual accuracy is disputed. Please see the relevant discussion on the talk page. (October 2009) |
 |
This article's tone or style may not be appropriate for Wikipedia. Specific concerns may be found on the talk page. See Wikipedia's guide to writing better articles for suggestions. (October 2009) |
Since the times of Isaac Newton, Joseph-Louis Lagrange, Pierre Simon Laplace, Carl Friedrich Gauss, and other great mathematicians of the Renaissance Era, there has been an inherent belief in the scientific community that the Earth is capable of retaining a stable ring system in orbit around it for millions of years.
For instance, in an article published in Nature back in 1980, the ex-NASA astronomer Dr. John A. O'Keefe (who is noted for discovering the Earth's slight pear-shape back in the 1950s) theorized the "O'Keefe Earth ring." He hypothesized it to be a Saturn-like ring of tektites that could explain the Eocene extinctions of 35 million years ago.
That ring was thought to have cut out as much as a third of all sunshine reaching the Earth's surface. It is also thought that it was in existence for between one and several million years. Colder Winters, and the extinction of hundreds of species including horses in Europe and plankton in the Caribbean, marked the end of the geologic Eocene period in Earth's history, occurring approximately 35 million years ago.
In Science Frontiers (Issue #76, Jul-Aug 1991), "In the past, the Earth had a ring system just like Saturn, Uranus and Neptune," according to a Danish astronomer. He has gone so far as to say that our planet boasted rings on 16 separate occasions in the past 2,800 years.
As recently as September 2002, Sandia National Laboratories published an article by two University of New Mexico researchers who again reinforced the notion of past "Earth rings."
In that study, the authors supposed the existence of a thin system of rings created by large meteoritic impacts, which caused material to get ejected back out into space and then gather into a debris ring formation along the Earth's equatorial plane. They again suggested that such a ring system, perhaps of similar opacity to Saturn's B-ring, may have caused past climatic changes on the Earth by blotting out sunlight and casting a cooling shadow over the equator for hundreds of thousands of years.
Since then, there have been many proponents in the global space community who advocated that an artificial ring system could help us to cool off a runaway greenhouse effect resulting from current global warming. The article "Earth Rings for Planetary Environment Control," authored by four researchers from the World Space Congress and published in the Smithsonian/NASA ADS system, is most notable in that respect. It argues in favor of many advantages of having a ring around the Earth, such as controlling climate temperature, reducing the intensity of the Van Allen radiation belts, making dangerous near-Earth flying asteroids more useful, providing night-time illumination without power, and creating an artificial ionosphere for radio communications.
Visual comparison
See also
External links
Notes
- ^ http://www.nasa.gov/mission_pages/cassini/media/rhea20080306.html NASA - Saturn's Moon Rhea Also May Have Rings
- ^ Jones, G. H.; et al. (2008-03-07). "The Dust Halo of Saturn's Largest Icy Moon, Rhea". Science (AAAS) 319 (5868): 1380–1384. doi:. PMID 18323452. http://www.sciencemag.org/cgi/content/short/319/5868/1380.
- ^ Lakdawalla, E. (2008-03-06). "A Ringed Moon of Saturn? Cassini Discovers Possible Rings at Rhea". The Planetary Society web site. Planetary Society. http://planetary.org/news/2008/0306_A_Ringed_Moon_of_Saturn_Cassini.html. Retrieved 2008-03-09.
- ^ "Saturn's Rings May Be Old Timers". NASA (News Release 2007-149). December 12, 2007. http://www.nasa.gov/mission_pages/cassini/media/cassini20071212.html. Retrieved 2008-04-11.
- ^ Gunter Faure, Teresa M. Mensing (2007). Introduction to Planetary Science: The Geological Perspective. Springer. ISBN 402052332, 9781402052330.
- ^ Miner, Ellis D., Wessen, Randii R., Cuzzi, Jeffrey N. (2007). "Present knowledge of the Neptune ring system". Planetary Ring System. Springer Praxis Books. ISBN 978-0-387-34177-4.
- ^ Salo, Heikki; Hanninen, Jyrki (1998). "Neptune's Partial Rings: Action of Galatea on Self-Gravitating Arc Particles". Science 282: 1102–1104. doi:. PMID 9804544. http://ads.ari.uni-heidelberg.de/abs/1998Sci...282.1102S.
- ^ Steffl, Andrew J.; S. Alan Stern. First Constraints on Rings in the Pluto System. astro-ph/0608036. http://arxiv.org/abs/astro-ph/0608036.
- ^ Holsapple, K. A. (December 2001). "Equilibrium Configurations of Solid Cohesionless Bodies". Icarus 154 (2): 432–448. doi:. http://adsabs.harvard.edu/abs/2001Icar..154..432H. Retrieved 2007-12-13.
- ^ Gürtler, J. & Dorschner, J: "Das Sonnensystem", Barth (1993), ISBN 3-335-00281-4
|
||||||||
|
|||||||||||||||||
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| Shopping: ring |
Learn More
 | growth ring |
| ring buoy |
| Grade, Lord Lew (Quotes By) |
 | Can your engagement ring be your wedding ring? Read answer... |
| What is the history of Ring A Ring Of Roses? Read answer... |
| How do you get ring of the white rings on furniture? Read answer... |
Help us answer these
 | What is the meaning of the ring in the fellowship of the ring? |
| What is the ring from lord of the rings made of? |
| Is zac's ring an engagment ring? |
Post a question - any question - to the WikiAnswers community:
Copyrights:
 |
 | Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved. Read more |
|
| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
 |
| Computer Desktop Encyclopedia. THIS COPYRIGHTED DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher. © 1981-2009 Computer Language Company Inc. All rights reserved. Read more |
 |
| Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more |
 |
| Intelligence Encyclopedia. Encyclopedia of Espionage, Intelligence, and Security. Copyright © 2004 by The Gale Group, Inc. All rights reserved. Read more |
 |
| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Planetary ring". Read more |
Related answers
- What have rings or ring?
- It has a ring to it.?
- What is the Ring about?
- What are rings like on a ring stand?
ADVERTISEMENT
Answer these
- What is ring a ring of ring roses?
- What is ring a ring a ring roses?
- When will your ring be in?
- Where is your ring?
- Will you ring me?
Mentioned in
- growth ring
- ring buoy
- Grade, Lord Lew (Quotes By)
- flan ring (culinary)
- annulorrhaphy
- circinate
- MRT
- r
- Annulus (in medicine)
- subring
- shaft-ring (architecture)
- closing ring
- ring-streaked
- commutative ring (mathematics)
