One might expect the particles of a ring to have accumulated long ago into larger satellites. Planetary rings are always closer to the planets than their large satellites.
The outer radius of this zone in which rings are found is called the Roche limit after the French mathematician Eduoard A. Roche , who described it in For a satellite with no internal strength and whose density is the same as the planet, the Roche limit is 2.
There are two possible explanations for their origin. This hypothesis assumes that the rings and moons originated at the same time in a flattened disk of gas and dust with large, new born Saturn at the center. In this case, the rings could have formed after Saturn, its satellites and much of the rest of the solar system. They glisten with clean particles of pure water ice, unsullied by the constant pelting by cosmic dust. The rings would look much darker if they were very old, just as new-fallen snow becomes dirty over time.
When setting up density waves in the rings, nearby moons extract momentum from the ring particles, causing them to slowly spiral toward Saturn; to conserve momentum in the overall system, the moons gradually move away from the planet. The A ring will eventually be dragged down into the B ring, and all the rings should collapse as the result of this moon-ring interaction in about million years.
A satellite could form outside the Roche limit and move inward due to the pull of tidal forces that would eventually rip the satellite to pieces. Saturn: lord of the rings The remarkable rings of Saturn Billions of whirling particles of water ice The austerely beautiful rings of Saturn are so large and bright that we can see them with a small telescope.
Ringlets, waves, gaps and spokes From a distance, the principal rings of Saturn look like smooth, continuous structures. Why do planets have rings? Lang, Tufts University.
These moons likely coalesced from the planet's rings and get their color from either ice volcanoes or a mysterious red material in the rings, according to a new study. Saturn not only possesses extraordinary rings, but also more than 60 moons. A half-dozen or so of these moons appear linked with the giant planet's main rings, either lodged within these features or gravitationally interacting with them to sculpt their shapes and influence their composition.
The ring moons often possess bizarre features; for example, Pan and Atlas are shaped like flying saucers. Saturn's moons can also vary in color from adjacent rings, and astronomers have questioned why these differences appear. Image of Saturn. Although the sun is on the other side of Saturn in this dramatic image, some sunlight scatters through the uppermost part of the atmosphere to reach the Cassini spacecraft's cameras.
This image wa High-Phase Drama. Mimas by Saturnshine. Crescent Titan by Jason Major. A meteor streaks across the sky during the annual Perseid meteor shower. Perseid Meteor Mimas and the Rings. This view from NASA's Dawn spacecraft shows an unnamed Cerean crater that is surrounded by a smooth blanket of ejecta, including bright material.
Both the area around the crater and its floor are p This image, taken by NASA's Dawn spacecraft, shows the surface of dwarf planet Ceres from an altitude of miles 1, kilometers. The image was taken on September 9, , and has a resolution These two color composite images of Saturn's moon Iapetus from Cassini's visual and infrared mapping spectrometer were obtained on Dec. An oval-shaped feature, wider than Earth and with streamers extending out to the east and west, swirls in Saturn's southern hemisphere.
They are so expansive and bright that they were discovered as soon as humans began pointing telescopes at the night sky. Galileo Galilei was the first person known to view the heavens through a telescope.
Cassini spent more than a decade examining them more closely than any spacecraft has before. Along with Saturn and its moons, the rings are one of the three primary components of the Saturn system. The rings are generally about 30 feet 10 meters thick or so and are almost completely composed of billions if not trillions of chunks of water ice, ranging in size from smaller than a grain of sand to the size of a mountain.
Cassini found that much of the material for Saturn's E-ring—a diffuse ring outside the bright, main rings—comes from the moon Enceladus, which is venting icy particles and gas into space as it orbits Saturn.
Cassini also discovered features that look like propellers, which are sometimes several thousand miles kilometers long. The propellers are produced by the gravitational influence of moonlets, lumps of ring material that are estimated to be half a mile around 1 kilometer in diameter, which is smaller than a moon but larger than individual ring particles.
The moonlets launch the surrounding ring particles hundreds of feet meters above and below the ring, producing the features Cassini imaged. The ring particles are kicked up in the same way that a moving boat creates wake. The ring particles nearer Saturn move faster than the moonlet while those farther from Saturn move slower than the moonlet, and the interaction is gravitational, causing wake to form both behind and in front of the moonlet as it orbits.
On Aug. For half of a Saturn year, the ringed planet appears to bow toward the sun, which then illuminates the top of the rings. But Saturn takes about 30 Earth-years to orbit the sun, so its equinox happens only once every 15 years.
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