Some planets, specifically Jupiter, Saturn, Uranus, and Neptune in our solar system, have planetary rings. Why do some planets have rings? How are they made and from what? Most importantly, will I be able to observe the rings on any planet with an amateur telescope?
Rings are made up of tiny and not so tiny pieces of rock and ice that are in some way the bits "left over" from the formation of the planet. The theory involves the Roche limit - and is that particles that are already within this limit can't accrete into a larger body because of the tidal forces involved. Another theory is that they are formed when a moon comes closer to a planet than the Roche limit, the tidal forces cause it to break up and form a ring.
Though the presence of "shepherd" moons in the rings of Saturn does hint that this may not be major source of material. Both explanations, to me, imply that you'd only get major ring systems around larger gas giant planets, though it doesn't preclude rings around smaller rocky planets. This seems to be borne out by our solar system where the gas giants have rings whereas the rocky planets don't.
As to being able to see them, you should be able to see the rings of Saturn with an amateur telescope which has a 50 - powers of magnification.
With binoculars you'll probably see a misshapen blob. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? The total mass of the B Ring, which is probably close to the mass of the entire ring system, is about equal to that of an icy moon kilometers in diameter suggesting that the ring could have originated in the breakup of such a moon. Between the A and B Rings is a wide gap named the Cassini Division after Gian Domenico Cassini, who first glimpsed it through a telescope in and whose name planetary scientists have also given to the Cassini spacecraft exploring the Saturn system.
The width of the main rings is 70, kilometers, yet their average thickness is only 20 meters. If we made a scale model of the rings out of paper, we would have to make them 1 kilometer across.
On this scale, Saturn itself would loom as high as an story building. The ring particles are composed primarily of water ice, and they range from grains the size of sand up to house-sized boulders. Note that the rings are mostly made of pieces of water ice of different sizes. In addition to the broad A, B, and C Rings, Saturn has a handful of very narrow rings no more than kilometers wide. The most substantial of these, which lies just outside the A Ring, is called the F Ring ; its surprising appearance is discussed below.
The particles in the E Ring are very small and composed of water ice. Since such a tenuous cloud of ice crystals will tend to dissipate, the ongoing existence of the E Ring strongly suggests that it is being continually replenished by a source at Enceladus. This icy moon is very small—only kilometers in diameter—but the Voyager images showed that the craters on about half of its surface have been erased, indicating geological activity sometime in the past few million years.
It was with great anticipation that the Cassini scientists maneuvered the spacecraft orbit to allow multiple close flybys of Enceladus starting in Those awaiting the Cassini flyby results were not disappointed. Infrared measurements revealed that these tiger stripes are warmer than their surroundings.
Best of all, dozens of cryovolcanic vents on the tiger stripes were seen to be erupting geysers of salty water and ice Figure 5. Estimates suggested that kilograms of material were shooting into space each second—not a lot, but enough for the spacecraft to sample. Figure 4: Enceladus. These dark stripes shown here in exaggerated color have elevated temperatures and are the source of the many geysers discovered on Enceladus.
They are about kilometers long and 40 kilometers apart. When Cassini was directed to fly into the plumes, it measured their composition and found them to be similar to material we see liberated from comets see Comets and Asteroids: Debris of the Solar System. The vapor and ice plumes consisted mostly of water, but with trace amounts of nitrogen, ammonia, methane, and other hydrocarbons. Minerals found in the geysers in trace amounts included ordinary salt, meaning that the geyser plumes were high-pressure sprays of salt water.
These discoveries suggested that in spite of its small size, Enceladus should be added to the list of worlds that we would like to explore for possible life. Since its subsurface ocean is conveniently escaping into space, it might be much easier to sample than the ocean of Europa, which is deeply buried below its thick crust of ice.
Figure 5: Geysers on Enceladus. Figure 6: Rings of Uranus. The nine main rings were discovered in from observations made of a star as Uranus passed in front of it. We call such a passage of one astronomical object in front of another an occultation. But in addition, the star dimmed briefly several times before Uranus reached it, as each narrow ring passed between the star and the telescope.
Thus, the rings were mapped out in detail even though they could not be seen or photographed directly, like counting the number of cars in a train at night by watching the blinking of a light as the cars successively pass in front of it. When Voyager approached Uranus in , it was able to study the rings at close range; the spacecraft also photographed two new rings Figure 6.
It is only about kilometers wide and probably no more than meters thick similar to the F Ring of Saturn. The Epsilon Ring encircles Uranus at a distance of 51, kilometers, about twice the radius of Uranus. Figure 7: Rings of Neptune. Note the two denser regions of the outer ring. The individual particles in the uranian rings are nearly as black as lumps of coal.
While astronomers do not understand the composition of this material in detail, it seems to consist in large part of carbon and hydrocarbon compounds.
Spectroscopy will also tell astronomers the age of the ice in the rings. Gaps in our understanding of Solar System evolution will be filled in.
Finally, Webb will look at some puzzling features of rings that astronomers are still working to understand. Around Neptune, intermittent regions of thickly clustered particles, known as ring arcs, have been seen to split and evolve, but astronomers need more data to truly understand the processes taking place. Why Do Planets Have Rings? View All Articles. Though we think of rings as being passive, decorative elements to a planet, they're actually more like an extra-planetary surface.
Karkoschka University of Arizona.
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