Ring A is the largest and brightest ring in the outer layer, and its inner boundary is Cassini seam, while its clear outer boundary is very close to the orbit of the atlas of small satellites. A-ring starts from the outer edge and is interrupted by Cohen perimeter at 22% of the ring width. There is a narrow Keeler's circumferential seam at 2% of the width from the outer edge.
The thickness of ring A is estimated to be 10 m to 30 m, the mass is 6.2×10/8 kg (about the mass of Japelli), and the optical depth varies from 0.4 to 1.0.
Similar to ring B, the outer edge of ring A is also maintained by orbital resonance, which is 7:6 with Janus and Abimysius. Other orbital resonances also excite many spiral density waves in ring A (and to a lesser extent, other rings), which occupy most of the structure. These waves are the same as the physics describing the spiral arm waves of galaxies. Spiral bending wave, which also appears in the A-ring and is described by the same theory, is a vertical groove in the ring, not a compression wave.
Cohen's annular gap Cohen's annular gap is a gap with a width of 325 kilometers in ring A, and the distance between its center and Saturn's center is 133590 kilometers, which is caused by the small satellite Pan running in the ring. Images from the Cassini spacecraft show that there are at least three thin and tangled rings in this gap. Spiral density waves can be seen on both sides, which are caused by orbital resonance with nearby satellites from the outside. These spirals are particularly energetic under the guidance of disks in the ring (refer to the atlas).
This ring was discovered by james edward Keeler in 1888. Johann encke himself did not observe this ring seam, but it was used to commemorate his observation of the ring.
Because it is completely inside the A ring, the seam of Cohen ring is a gap. Before the International Astronomical Union explained this point in 2008, the meaning of gap and split was somewhat vague. Before that, Cohen's circumferential seam was sometimes called Cohen's crack.
Keeler girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth girth. It was named after astronomer James Edward Keeler. On May 1 2005, a small satellite Daphne was found at the gap, which cleared the area, and this satellite also caused ripples at the edge of the gap.
Small Satellites In 2006, four small satellites were found in the image of ring A taken by Cassini (see atlas). These small satellites are only a few hundred meters in diameter, because they are too small to be seen directly. Cassini discovered these small satellites after seeing them cause turbulence for several kilometers like propellers. It is estimated that there are hundreds of such small celestial bodies in Ring A ... In 2007, more than eight small celestial bodies were discovered, which created a turbulent zone as long as 3,000 kilometers, about130,000 kilometers away from Saturn's center. More than 150 thruster satellites have been detected. Ring B is the largest, brightest and heaviest of all rings. Its thickness is estimated to be 5 ~ 15 m, its mass is 2.8 × 10 kg, and its light depth varies from 0.4 to 2.5, which means that nearly 99% of the light passing through the B ring will be blocked. Many changes in the density and luminosity of B-rings have hardly been reasonably explained. B-rings are concentric circles. Although there are many narrow small rings, the B ring does not contain any gaps.
Before the spokes were 1980, the structure of Saturn's rings was completely explained by gravity, until the image of the navigator showed that there were radial features called spokes on the B ring, which could not be explained. Because according to orbital mechanics, their duration and rotation period are inconsistent with those of rings. These spokes appear dark under background scattered light and bright under foreground scattered light. The mainstream theory holds that they are tiny dust particles suspended on the ring plane by electrostatic repulsion on the main ring, so their rotation is synchronous with Saturn's magnetosphere. However, the exact mechanism of spokes is still unclear, although it has been suggested that these electronic interferences may come from lightning released from Saturn's atmosphere or the impact of meteoroids on Saturn's rings.
It was not until 25 years later that the Cassini spacecraft observed the spokes again. When Cassini arrived at Saturn in early 2004, there were no spokes. Some scientists speculate that according to the model they are trying to describe the formation of spokes, spokes will not be visible until 2007. However, Cassini's imaging team searched the preserved image of Saturn's rings on September 5, 2005, and saw the spokes.
The appearance of spokes seems to have seasonal changes, disappearing in Saturn's midsummer or midsummer and reappearing when Saturn approaches the vernal equinox. It has been suggested that spokes may be seasonal. With the change of Saturn's orbit in 29.7 years, it also supports that spokes will gradually increase in the Cassini mission in the next few years. C-ring is a wide and dark ring inside B-ring. It was discovered by William and George Bond in 1850, but William R. Dawes and John Galle also saw it independently. William russell called it a black ring, because it is darker than the bright A ring and B ring.
It is estimated that its vertical thickness is only 5 meters, its mass is about 1. 1 × 10 kg, and its light depth varies from 0.05 to 0. 12. That is to say, only 5% to 12% of the light vertically passing through the ring will be blocked by the ring, so it is almost transparent from above or below.
Colombo seams and titan rings
Colombo seam is located on the inside of C-ring. There is a bright and narrow Colombo ring in the seam, and its center is 77,883 kilometers away from Saturn's center. This ring is a little oval, not a perfect circle. This small ring is sometimes called Titan's small ring because it is constrained by Titan's orbital resonance. At this position of the ring, the precession period of the particle arch point on the ring is exactly the same as the orbital period of Titan, so the outermost tail end of this eccentric small ring always points to Titan.
Maxwell sews Maxwell sews are on the outside of the C ring, and there are also dense but out-of-round Maxwell rings. This small ring is similar to Uranus' ε ring in many details. There is a wave structure between these two rings, and the waves in Uranus ε ring are caused by Cardoria, but as of July 2008, no satellites have been found in or near Maxwell gap. Saturn's rings are bright, wide and thin. Saturn's rings extend into the vast space outside Saturn. Saturn's outermost circle is from Saturn's center 10~ 15 Saturn's radius. Saturn's halo is 200,000 kilometers wide, and more than ten earths can be arranged side by side on the surface of the halo. If you roll an earth on it, it will roll on the sidewalk like a ball. The main Saturn rings range in width from 48 km to 302,000 km and are named after the first seven letters of the English alphabet. Saturn's rings are named D, C, B, A, F, G and E in the order of discovery. Saturn and Saturn's rings were formed in the early days of the solar system, when the sun was surrounded by cosmic dust and gas, and finally Saturn and Saturn's rings were formed. Saturn's rings are very thin. Through Saturn's halo on the earth, we can also see the twinkling stars behind the halo. The thickness of Saturn's rings is estimated not to exceed 150 km. Therefore, when one side of the halo turns to us, people far away from the earth look over, and Saturn's ring with a thickness of 150 km is like a piece of tissue paper-the halo "disappears". Every 15 years, the halo will disappear.
The strange rings of Saturn lie in Saturn's equatorial plane. Like the revolution of the earth, there is an angle between Saturn's equatorial plane and its orbital plane around the sun. This 27-degree inclination caused the change of Saturn's rings. We will "look up" at Saturn's rings for a while and "look down" at Saturn's rings for a while. At this time, Saturn's rings are like a beautiful wide-brimmed straw hat. At other times, it looks like a flat disk, or suddenly disappears. This is because we are in the "head-up" aura, and even the best telescope can't find its "trace". 1950~ 195 1 year, 1995~ 1996, Saturn's rings are missing years. There is still a bright spot hidden in Saturn's ring, which is our earth. However, it may not be wrong to say that Saturn's rings evolved from satellites. Through the data sent back by Cassini in 2007, scientists have found enough evidence to verify this theory in at least one of Saturn -G rings. G ring is located on the outside of Saturn's ring. 1979, Voyager accidentally discovered this ring while flying over Saturn. Near the ring is Titan, which is only 15 thousand kilometers away from the G ring, but the G ring has not been decomposed into dust clouds by Titan. With the data sent back by Cassini, scientists found that there is a bright arc structure inside the G ring, which is composed of rocks with a diameter of tens of meters. It is these rocks that break down into a part of the G ring after constant collision. Scientists explained that there was once a satellite in the G ring, but for some reason, it disintegrated and evolved into a ring, and Cassini just saw the last scene of this evolution.
The F ring adjacent to the G ring is also a halo that scientists are very interested in. The strange thing about this ring is that it often changes shape and turns itself into a kink shape. Scientists speculate that there may be undiscovered small satellites in the F ring, which will affect the shape of the ring when they pass through the ring. In June 2008, scientists published their latest research results on this ring in Nature. They say that such a small satellite does exist in the F ring, and this ring is also influenced by Titan and Titan, which are located inside and outside the F ring respectively. Their combined action will bind and squeeze the F-ring, making it stagger. Titan also passes through the F-ring along an elliptical orbit. Every time it travels, it will drag out a groove on the F ring, and the resulting gravity will bend and stretch the F ring, thus twisting it into a spiral shape. Scientists say that the study of F-rings is of great significance and helps us to understand the ring behavior of other gas giants. This complex interaction between rings and satellites will become an important basis for us to understand planetary rings.
Compared with the F ring, Saturn's rings A and B attract scientists' attention. Scientists frequently find new blocks in the A ring, most of which are about 100 meters in diameter, and the number has reached dozens. This makes scientists realize that there are many such small satellites around Saturn, which may be millions, and Titan and Rhea in Ring A are only the largest ones, which shows that apart from larger satellites and smaller particles, this "medium-sized" substance in Saturn's ring is also very important. This discovery will help people to re-understand the formation theory of Saturn's rings and even the whole solar system. There is only one "seam" between ring A and ring B, and this "seam" is Cassini seam. Passing through Cassini's seam is a wide B ring. The biggest mystery on the B-ring is the radiation stripe on it. They are some dust clouds caused by static electricity, which were discovered in the 1980s. However, until now, there are still different opinions on their explanations. One explanation is that they are caused by thunderstorms and lightning on Saturn, and the other is due to the collision of meteorites or the impact of solar wind particles. Scientists have found that the brightness of these stripes seems to change with Saturn's seasons, which is most obvious in Saturn's spring and autumn. Saturn will go too far in August. At that time, scientists engaged in Cassini mission will carefully observe the B ring, and perhaps the mystery of radiation stripes on the B ring will be more reasonably explained in the near future.