A planetary ring is a ring of dust and other small particles orbiting around a planet in a flat disc-shaped region. In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is The most spectacular and famous planetary rings are those around Saturn, but the other three gas giants of the solar system (Jupiter, Uranus, Neptune) possess ring systems of their own. Saturn has the most extensive Planetary ring system of any planet in the Solar System. A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large Planet that is not primarily The Solar System consists of the Sun and those celestial objects bound to it by Gravity. Neptune ( English|AmE] ] is the eighth and farthest Planet from the Sun in the Solar System.
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. TemplateInfobox Planet.--> Rhea (ˈriːə, or as in Greek The Saturnian moon Rhea may have a tenuous ring system consisting of three narrow relatively dense bands within a particulate disk
Contents |
Overview
There are three ways that planetary rings 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. A protoplanetary disk (or proplyd) is a rotating Circumstellar disk of dense gas surrounding a young newly formed star a T Tauri star or Herbig star Determining the Roche limit The Roche limit depends on the rigidity of the satellite A natural satellite or moon is a Celestial body that Orbits a Planet or smaller body which is called the primary. Most rings are thought to be unstable and to dissipate over the course of tens or hundreds of millions of years, but it 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. TemplateInfobox Planet.--> Prometheus (proʊˈmiːθiəs,, or There is also an Asteroid called 55 Pandora. Saturn has the most extensive Planetary ring system of any planet in the Solar System. 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. Gravitation is a natural Phenomenon by which objects with Mass attract one another
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. TemplateInfobox Planet.--> Metis (, or as in Greek Μήτις Adrastea (, or as in Greek Αδράστεια also known as Jupiter XV, is the second by distance and the smallest of the four inner moons of Jupiter Determining the Roche limit The Roche limit depends on the rigidity of the satellite 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. The tidal force is a secondary effect of the Force of Gravity and is responsible for the Tides It arises because the gravitational acceleration experienced A moon inside the Roche limit is held together only by its mechanical strength rather than by its gravity, and so loose material on its surface would simply "fall off" to join the rings.
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. Voyager 2 is an unmanned Interplanetary Spacecraft launched on August 20, 1977. It is thought that the gravitational influence of the shepherd moon Galatea and possibly other as-yet undiscovered shepherd moons are responsible for this clumpiness. See also
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. New Horizons is a Robotic spacecraft mission by NASA currently underway [5]
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. [6][7]
After the impact of Theia and before the coalescence of the Moon, it is generally assumed that the Earth had a ring system.
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. The planet Jupiter has a system of rings known as the rings of Jupiter or the Jovian ring system. Saturn has the most extensive Planetary ring system of any planet in the Solar System. The planet Uranus has a system of rings intermediate in complexity between the more extensive set around Saturn and the simpler systems around Jupiter and Neptune has a faint dusty Planetary ring system, which was discovered in 1989 by Voyager 2 spacecraft The Saturnian moon Rhea may have a tenuous ring system consisting of three narrow relatively dense bands within a particulate disk H. ; et al. (2008-03-07). "The Dust Halo of Saturn's Largest Icy Moon, Rhea". Science 319 (5868): 1380-1384. AAAS. The American Association for the Advancement of Science (or AAAS) is an organization that promotes cooperation between Scientists defends scientific freedom encourages doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Lakdawalla, E. (2008-03-06). 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1079 - Omar Khayyám completes the Iranian calendar. 1454 - Thirteen Years' War: Delegates of A Ringed Moon of Saturn? Cassini Discovers Possible Rings at Rhea. The Planetary Society web site. Planetary Society. The Planetary Society is a large publicly supported non-government and not-for-profit organization that has many research projects related to Astronomy. Retrieved on 2008-03-09. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 590 - Bahram Chobin is crowned as king Barham VI of Persia.
- ^ Saturn's Rings May Be Old Timers. NASA (News Release 2007-149) (December 12, 2007). Retrieved on 2008-04-11. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 491 - Flavius Anastasius becomes Byzantine Emperor, with the name of Anastasius I.
- ^ Steffl, Andrew J. ; S. Alan Stern. "First Constraints on Rings in the Pluto System". astro-ph/0608036.
- ^ Holsapple, K. A. (12 2001). "Equilibrium Configurations of Solid Cohesionless Bodies". Icarus 154 (2): 432-448. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Gürtler, J. & Dorschner, J: "Das Sonnensystem", Barth (1993), ISBN 3-335-00281-4
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic