The rings of the sixth planet. The rings of the moon of Saturn. Rings are named alphabetically
21.07.2015
Saturn, the sixth planet from the Sun, is one of the most easily observed objects for astronomers, thanks in large part to its vast and highly specific ring system. The rings of Saturn have fascinated amateur astronomers for centuries, since the time when people first began to peer into the sky through the eyepiece of a telescope.
When Galileo Galilei first observed Saturn in 1610, he thought that these rings were giant satellites of the planet, located along different sides from her. However, further observations carried out by the scientist over the next few years showed that these rings changed their shape and even disappeared completely, as their tilt in relation to the Earth changed.
We now know that Galileo observed a "plane intersection of the rings." Saturn's equator is tilted in relation to the planet's orbit around the Sun at an angle of about 27 degrees (the same tilt angle for Earth is 23 degrees). When Saturn revolves around the Sun, then first one, and then the second hemisphere in turn is illuminated by the Sun. This tilt is responsible for the change of seasons, as is the case with the Earth, and when Saturn comes autumn or the vernal equinox, then the Sun falls into the plane of the ring system, in which the equator of the planet also lies. Sun rays illuminate the rings "edge-on", and a thin strip of rings becomes difficult to distinguish with telescopes. Saturn's rings are very wide - they are 273,600 kilometers across - but they are no more than 10 meters thick.
In 1655 astronomer Christian Huygens suggested that these strange bodies were solid, tilted rings, and in 1660 another astronomer suggested that these rings consisted of small satellites - a guess that could not be confirmed for nearly 200 years to come.
In the era of space exploration, the Pioneer 11 probe passed through the plane of Saturn's rings in 1979. the spacecraft Voyager 1 and Voyager 2 provided a glimpse into the ring system of the giant planet.
In 2004, NASA's Cassini-Huygens mission entered orbit around Saturn for the first time in the world and made detailed observations not only of the planet itself, but also of its ring system.
Composition and structure
Saturn's rings are made up of billions of particles, ranging in size from a few millimeters to tens of kilometers. Consisting primarily of water ice, these rings also suck in rocky meteoroids moving through space.
Although it may seem to a novice amateur astronomer that Saturn is girded with a single, solid ring, in fact, the ring system is divided into several parts. These rings are named alphabetically according to the dates of their discovery. Thus, the main rings, as we move from the periphery of the system to the center, are called A, B, and C, respectively. A 4,700-kilometer wide gap, known as the Cassini Gap, separates rings A and B.
Other, fainter rings opened up as telescope technology improved. Voyager 1 discovered the D ring closest to the center of the system in 1980. Next to ring A, enclosing it from the outside, there is ring F, which, in turn, is enclosed by rings G and E, which lie at a considerable distance from the rest of the rings of the system ...
The rings themselves contain a significant number of gaps and structures. Some of them were created by the numerous small moons of Saturn, while the nature of others of them still continues to baffle astronomers.
Saturn is not the only planet Solar system having rings - Jupiter, Uranus, and Neptune also have faint ring systems - but with their satellites spanning three-quarters of the Earth-Moon distance (282,000 kilometers), it undoubtedly forms the most impressive and observable ring system in the solar system.
Saturn is one of the most mysterious planets for both professional astronomers and amateurs. Much of the interest in the planet comes from the characteristic rings around Saturn. Although not visible to the naked eye, the rings can be seen even with a weak telescope.
Most of Saturn's ice rings are kept in orbit by the complex gravitational forces of the gas giant and its satellites, some of which are actually within the rings. Despite the fact that people have learned a lot about rings since they were first discovered 400 years ago, this knowledge is constantly being updated (for example, the ring farthest from the planet was discovered only ten years ago).
1. Galileo Galilei and Saturn
Inspirational telescopes
In 1610, the famous astronomer and "enemy of the church" Galileo Galilei was the first person to point his telescope at Saturn. He noted the strange formations around the planet. But, since his telescope was not powerful enough, Galileo did not realize that these were rings.
2. Billions of chunks of ice
Ice and stone
Saturn's rings are made up of billions of pieces of ice and stone. These fragments range in size from a grain of salt to a small mountain.
3. Only five planets
Modern telescope
As you know, a person can see five planets with the naked eye: Mercury, Venus, Mars, Jupiter and Saturn. To see Saturn's rings, and not just a ball of light, you need a telescope with at least 20x magnification.
4. Rings are named alphabetically
The closest to Saturn is ring D
The rings are named in alphabetical order based on their discovery date. The D ring is closest to the planet, followed by rings C, B, A, F, Janus / Epimetheus, G, Pallene and E.
5. Remains of comets and asteroids
93% of the mass of the rings - ice
The rings of Saturn, according to most scientists, are the remnants of passing comets and asteroids. Scientists have come to this conclusion because about 93% of the mass of the rings is ice.
6. The person who gave the definition of the rings of Saturn
Dutch astronomer Christian Huygens
The first person to actually see and define Saturn's rings was the Dutch astronomer Christian Huygens in 1655. At the time, he suggested that the gas giant has one solid, thin and flat ring.
7. Saturn's moon Enceladus
E ice ring geysers
Thanks to the geysers that abound on the surface of Saturn's moon Enceladus, ice ring F. Scientists have very high hopes for this satellite, because it has oceans in which life can hide.
8. Rotation speed
The speed decreases with distance
Each of the rings revolves around Saturn at a different speed. The speed of rotation of the rings decreases with distance from the planet.
9. Neptune and Uranus
Saturn's rings are not unique
Although Saturn's rings are the most famous in the solar system, three more planets boast rings. We are talking about the gas giant (Jupiter) and the ice giants (Neptune and Uranus).
10. Disturbances in the rings
Perturbations resemble ripples
The planet's rings can act as evidence of how comets and meteors flying through the solar system are attracted to Saturn. In 1983, astronomers discovered ripple-like disturbances in the rings. They believe it was caused by the comet debris colliding with the rings.
11.Clash of 1983
Orbits of rings C and D are broken
A 1983 collision with a comet weighing between 100 billion and 10 trillion kilograms caused the orbits of rings C and D to be disrupted. The rings are believed to be "aligned" over hundreds of years.
12. Vertical "tubercles" on the rings
Vertical formations up to 3 km
Particles inside Saturn's rings can sometimes form vertical formations. It looks like vertical "bumps" on rings about 3 km high.
13. Second after Jupiter
Rotational speed of Saturn - 10 hours and 33 minutes
Apart from Jupiter, Saturn is the fastest rotating planet in the solar system - it makes a complete revolution on its axis in just 10 hours and 33 minutes. Due to this rotation rate, Saturn is more convex at the equator (and flattened at the poles), which further emphasizes its iconic rings.
14. Ring F
Mini satellites of the planet
Located just behind Saturn's main ring system, the narrow F ring (actually three narrow rings) appears to have kinks and clumps in its structure. This led scientists to assume that there may be mini-satellites of the planet inside the ring.
15. Launch of 1997
Interplanetary station Cassini
In 1997, the automatic interplanetary station Cassini was launched to Saturn. Before entering orbit around the planet, the spacecraft flew between rings F and G.
16. Tiny moons of Saturn
Keeler and Encke slits
In the two crevices or divisions between the rings, namely Keeler (35 km wide) and Encke (325 km wide), there are tiny satellites of Saturn. It is assumed that these gaps in the rings were formed precisely due to the passage of satellites through the rings.
17. The width of Saturn's rings is enormous.
Saturn's rings are very thin
Although the width of Saturn's rings is enormous (80 thousand kilometers), their thickness is relatively very small. As a rule, it is about 10 meters and rarely reaches 1 kilometer.
18. Dark stripes running across the rings
Strange formations that look like ghosts
In the rings of Saturn, strange formations that look like ghosts have been discovered. These formations, which look like light and dark stripes running across the rings, are called "spokes". Many theories have been put forward regarding their origins, but unanimous opinion no.
19. Rings of the moon of Saturn
Saturn's moon Rhea
Saturn's second largest moon, Rhea, may have its own rings. They have not yet been discovered, and the existence of rings is assumed on the basis of the fact that the Cassini probe recorded the deceleration of electrons of Saturn's magnetosphere in the vicinity of Rhea.
20. Scanty weight of the rings
Appearance is deceiving
Despite the apparent huge size, the rings are actually quite "light". More than 90% of the mass of all matter in orbit of Saturn is in the largest of the 62 satellites of this planet, Titan.
21. Cassini division
The biggest gap between the rings
The Cassini division is the largest gap between the rings (its width is 4700 km). It is located between the main rings B and A.
22. Pandora and Prometheus
Satellites contain the scattering of rings in space
The gravity of some of Saturn's moons - especially Pandora and Prometheus - also affects the rings. Thus, they restrain the dispersion of the rings in space.
23. Ring of Phoebe
The ring rotates in the opposite direction
Astronomers recently discovered a new, huge ring around Saturn, dubbed the "Phoebe ring." Located at a distance of 3.7 to 11.1 million km from the planet's surface, the new ring is tilted 27 degrees compared to the rest of the rings and rotates in the opposite direction.
24. A billion planets such as the Earth can fit in the ring.
The new ring is very sparse
The new ring is so rarefied that one can fly through it without noticing a single debris, despite the fact that a billion planets such as Earth can fit in the ring. It was discovered by accident in 2009 using an infrared telescope.
25. Many of Saturn's moons are icy
Satellites formed from distant rings
Due to recent discoveries made in 2014, scientists believe that at least some of Saturn's moons may have formed within the rings of this planet. Since many of Saturn's moons are icy, and ice particles are the main component of the rings, it has been hypothesized that the moons formed from distant rings that existed before.
In 2009, astronomers discovered: in addition to the 25 nearby rings, Saturn has another barely distinguishable ring, located much further than the rest. It was named the Phoebe ring, after the moon of Phoebe. Presumably, the ring consists of particles from this satellite.
The illustration schematically shows the gigantic size of the Phoebe ring, compared to the planet itself (several dots in the center).
This ring is deservedly included in the list of the strangest objects in the Universe discovered to date.
A hoop of dust revolves around the gas giant at a distance of about 13 million km, which is almost 50 times farther than other rings.
Phoebe's ring was discovered in 2009 by the Spitzer space observatory, which observes space in the infrared range and is capable of detecting particles about 10 microns in size. Phoebe's dust hoop partially consists of such particles (the density per cubic meter was initially estimated at 10-20 particles).
The Phoebus satellite, photo from the Cassini apparatus
Unfortunately, on May 15, 2009, the Spitzer telescope ran out of refrigerant so that it could not continue observations.
To further explore the ring, in June 2010, astronomers pointed towards Saturn the lens of another infrared telescope, Wide-field Infrared Survey Explorer (WISE), which is in near-Earth orbit. And with his help, for the first time, it was possible to obtain an image of Phoebe's ring in its entirety. In the photograph, it can be seen as a rarefied dust cloud in the horizontal plane.
NS 
June 10, 2015 in the journal Nature published a study carried out by a group of scientists from the University of Maryland, the University of Virginia and the Center for the Processing and Analysis of Infrared Images at the California Institute of Technology. The study analyzed data obtained from the WISE telescope.
The size of the ring and its distance from Saturn turned out to be larger than expected. In 2009, the particles were recorded at a distance of 128 to 207 Saturn radii (R S = 60 330 km) from the planet. The total vertical dimension of the ring is 40 RS. Thus, Phoebe's ring is more than ten times larger than the formerly largest ring of E.
The full radial extent was not possible to measure in the Spitzer images, as well as the characteristics of the dust particles.
Images from WISE show that Phoebe's ring is even larger than anticipated: it stretches from 100 R S all the way to 270 R S (from 6 million km to 16 million km from the planet)! That is, 30% more than previously thought.
Scientists have compiled a model of the orbital dynamics of particles that have taken off from Phoebe as a result of collisions with extraneous cosmic bodies, and have constructed theoretical power-law profiles of particle size distribution. According to them, up to 10% of the cross-sectional area of the ring is large particles with a radius of more than 10 cm, the orbits of which could not descend into the ring for more than 4.5 billion years.
Thus, Phoebe's ring is significantly older than the inner rings of Saturn. It probably formed simultaneously with the solar system.
Unfortunately, the WISE telescope also ran out of refrigerant in 2010, and since then we have not received any new information about the Phoebe ring. According to scientists, now in space there is not a single apparatus that could help in the study of this object.
The amazingly beautiful rings were the first to be discovered at Saturn. This was done in the 17th century by the great astronomers Huygens and Galileo, who saw through their telescopes around the giant wide ring... In the 19th century, the astrophysicist from Russia A. Belopolsky and the physicist from England J. Maxwell were able to prove that the ring, which seemed to be solid through telescopes, could not be such. Subsequent study showed that Saturn is indeed a planet with rings.
Rings of saturn
At first, the rings aroused admiration and surprise, but their subsequent study showed that they appeared for a reason, but play a significant role in the formation of planets and the study of the Universe. Scientists managed to establish that the rings consist of huge amount microscopic particles and huge blocks of ice and are located along the equator. They are, by cosmic standards, thin, only a few kilometers, while their width is up to hundreds of kilometers.
The planet with rings never ceased to amaze astronomers. If initially it was believed that Saturn has only four rings, and they were designated by the Latin letters A, B, C, D, then later the fifth was established, at a greater distance from the planet than the rest. It was designated by the letter E. True, until some time the existence of the rings D and E was in doubt among scientists.
After the data was transmitted by American interplanetary stations, the materials and photographs of the rings were thoroughly studied. The sixth (F) was detected by the Pioneer-11 station. Pictures of rings E and D were sent by Voyager 1 station, which dispelled scientists' doubts about their existence.
How many rings does Saturn have
The planet with the rings attracted more and more attention. Continuing to study them, scientists have come to a sensational discovery. As it turned out, there are not six, but much more. The total number has not been established, but astronomers speculate that the number could be as high as a thousand rings.
As can be seen from the photographs sent by Voyager 2, narrow rings are made up of thinner rings or, as they are called, strands. The most interesting thing is that not all of them have correct shape... It was found that one of the rings changes its thickness from 80 to 25 kilometers.
Why do rings delaminate?
How can you explain this ring structure? Several hypotheses have been expressed, but the most interesting is that the stratification of the rings occurs due to the gravitational forces exerted by the satellites of Saturn, not only large, but also small, which were discovered relatively recently using spacecraft. Astronomers drew attention to the small, in comparison with others, the width of the F ring and suggested that this is somehow connected with the satellites of the planet. According to calculations, there should be two. One is on the outside of the ring, the other is on the inside. They are called "shepherds". It is believed that the satellites, acting on the particles, drive them back.
Mysteries of Saturn
Saturn is a planet whose rings pose many mysteries to man. Relatively recently, astronomers have discovered the so-called spokes - radial formations that pierce the rings for thousands of kilometers. They revolve around the planet, like the spokes of a wheel around an axis. The question immediately arises as to what it is. They cannot be constituents of the rings, since their particles are located on different distance and move at different speeds. This would lead to their rapid destruction.
After examining many photographs and conducting analysis, scientists have established that the spokes, together with the planet, make a complete revolution around the axis of Saturn. This made it possible to assume that they are located at a certain distance from the rings and are held by them using electrostatic forces. They perform their movement together with the planet under the influence magnetic field planets, but consist, like rings, of small particles. In the F ring, weaving of fine thread rings and thickenings were found. This is the mystery of Saturn. Astronomers cannot yet explain why this is happening. There is only an assumption that electromagnetic forces act on them.
Rings of other planets
In 1977, during the study of Uranus, rings were discovered, which led scientists to some confusion, since before that it was believed that only Saturn had such a phenomenon. Scientists began to think about which planets have rings. Voyager 1 discovered a faint ring around Jupiter. Today it is well known that all gas giant planets in the solar system have them. There are four such planets - Saturn, Jupiter, Neptune, Uranus. This list was supplemented by the asteroid Khariklo and, according to a number of scientists, they are at the satellite of Saturn - Rhea.
It is assumed that other planets are also ringed. But which planets have rings is not yet known. The calculations of some astronomers confirm their existence around the dwarf planet Pluto. But to date, this has not been confirmed, as in the case of Rhea's satellite.
Jupiter's rings
Another giant gas planet with rings is Jupiter. Their system is weak, consists of dust and includes four components: a thick torus made of particles - Halo, very thin and dense - the Main ring and two weak and wide ones, called spider rings. As scientists assume, they are formed from dust from the satellites of the planet. Another ring is believed to exist, but so far there is no confirmation of this.
Rings of neptune
The planet with rings in the solar system is the gas giant Neptune. Its structure was discovered relatively recently and has been little studied. It consists of five components made up of ice particles coated with silicates and an as yet unknown carbon-based material. The rings are named Adams, Le Verrier, Halo, Lassell and Arago.
An interesting fact is that the first ring was discovered by the American astronaut E. Guian. But later, conducting observations, astronomers noticed that it was not complete, resembling piston rings. The planet at this time entered the shadow. Why this happened remains unclear. The outermost ring has five arcs. Their origin is also not clear. Images from Voyager 2 revealed weaker rings, which had a massive structure.
Rings of uranus
A system of 13 rings was discovered near the planet, consisting of water ice, organic matter, dust and objects, the size of which ranges from several tens of centimeters to 20 meters. They are extremely dark, opaque and not wide. Presumably, there are weak dust rings and arcs between the main components of the system. It is believed that the system was formed from the collision of satellites that the planet previously had.
Last week, the Cassini spacecraft began the final part of its scientific program: "Dives" between the rings of Saturn. The first 20 dives into the plane of the rings will take place far from the gas giant, behind the F-ring, then, after the gravitational maneuver, the device will move to orbits that are close to the planet. By mid-September 2017, Cassini will enter the dense atmosphere and complete its multi-year mission. On the occasion of the start of this dangerous, but very interesting program Research, we have prepared a guide to the rings of Saturn, which will help you figure out what the apparatus will study.
Everyone knows that Saturn, the sixth planet from the Sun and the second largest after Jupiter, has the most luxurious (read: developed and massive) ring system in the entire solar system. Of course, other planets also have rings, for example, Jupiter and Neptune - and physicists predict that in some 20-40 million years they will also be on Mars. But all these rings cannot be compared with the Saturnian ones. The main system of rings alone (C, B, A) is 60 thousand kilometers wide - this is equivalent to the radius of the planet. Together with fainter rings, it stretches for more than 12 million kilometers. We will talk in more detail about the largest and most distant rings of Saturn a little later.
To begin with, a little about what the rings of Saturn are called. The main systems were named in Latin letters in the order of their discovery. That is why, counting from upper layers atmosphere, the rings are located as follows: D, C, B, A, F, G, E. In addition, there are rings named after the planet's satellites: Janus-Epitmeteus and Phoebe. It is not easy to answer the question of how many rings Saturn has in total - it depends on how you look at them. For example, in a ground-based telescope, you will most likely see a couple of rings, and Cassini can easily distinguish the slits inside big rings and counts dozens of entities. About 30 of them have their own name.
There are various theories about the origin and age of the rings. Some of them suggest that the rings are only 100 million years old - about two percent of the age of the solar system. In other versions, the rings may be the same age as Saturn itself. One common theory is that the rings were once a relatively large satellite that orbit too close to the planet. This led to its destruction by the gravity of Saturn. The total mass of material in the planet's rings is estimated at 3 × 10 19 kilograms, a thousand times less than the mass of the Earth's moon. Most of the rings are made of ice, but the composition of other components, in particular, giving them an orange-pink hue, is still unknown.
D-ring
D-ring (dull)
Let's start with the ring closest to Saturn, D. Although it is rather dull and not part of the main ring system, its proximity to the giant creates unusual patterns on it. The inner edge of the ring is about seven thousand kilometers from the planet's clouds: on the Earth's scale, it would be located only twice as high as the ISS - 800 kilometers above the surface. The width of the ring is 7.5 thousand kilometers. Upon approaching it in 1980, Voyager 1 noticed several separate rings in it, which on closer inspection turned out to be waves. It should be noted that the thickness of the rings is not great, especially in comparison with the width - in many cases it does not exceed several meters. The height of the waves ranged from two to twenty meters. Physicists claim that the source of the waves is a gravitational disturbance, for example, from a passing comet - a similar thing was observed later in the rings of Jupiter after the fall of comet Shoemaker-Levy 9.
C-ring
Inner area of the C-ring. A little to the right of the center is the Colombo Slit.
Immediately after the D-ring, there is a bright ring C, 17.5 thousand kilometers wide. It was discovered back in 1850 by American astronomers William and George Bond. Like D, it also showed gravitational waves. The C-ring contains 1/3000 of the entire mass of the debris material of Saturn's rings. Among the internal structures, one can distinguish the Columbo Slot, inside which there is a small ring that is in orbital resonance with Titan (the largest moon of Saturn). The gap is about 150 kilometers wide. In addition to her, there are three more smaller "gaps" in the ring - Maxwell, Bond and Davis
B-ring
B-ring outer edge
The next is the brightest and most massive of all the rings of Saturn - B. In terms of total mass, it is comparable to Mimas (the seventh largest satellite of the planet), and the thickness of the object is from five to fifteen meters. The width of the B-ring reaches 25.5 thousand kilometers, about a third of the diameter of Saturn. Inside it, by the way, is the satellite closest to the giant, which has not yet received a trivial name - S / 2009 S 1.
The most notable feature of the B-ring is the vertical formations on its outer edge. They are over 2.5 kilometers high - "Cassini" noticed them from the long shadows that they cast during the Saturnian equinox.
Cassini slit
On the right is the outer region of the B ring. The black slit in the center is the Huygens slit with a bright Huygens ring inside, which is part of the Cassini division. Left side snapshot also refers to division
Between the rings B and A is one of the most expressive structures of the system - the Cassini Gap (or Division). It is available for observation from the Earth with amateur telescopes above the average class. Its width is 4.5 thousand kilometers - comparable to the width of the D-ring. The object was discovered back in the 17th century by the French astronomer of Italian origin Giovanni Dominico Cassini. Observations with Voyager 1 have shown that there is material inside the gap that resembles that of the C ring, as well as "real" Gaps (for example, the 300 km Huygens Gap).
A-ring
Encke slit in the A-ring
At a distance of over 60 thousand kilometers from the surface of Saturn, ring A is located - the outer one of the main ring system. It is dimmer than ring B and 7 times lighter. The width of the object is 14.6 thousand kilometers, the thickness is 10-30 meters. It is believed that this is one of the youngest rings of Saturn due to this uneven temperature distribution in it.
There are several relatively large satellites within the A ring: the 20-kilometer Pan, the 7-kilometer Daphnis, and the 32-kilometer Atlas. Their gravitational influence forms the edges of the object. Like the inside of the other rings, it has large cracks, for example, the 325-kilometer-long Encke Crack.
F-ring
F-ring and Prometheus
At a distance of 2.6 thousand kilometers from outer edge The A-rings and 140 thousand kilometers from the center of Saturn is the most volatile ring of Saturn - F. With a width of only 30-500 kilometers, it attracts the attention of astronomers as an unusual dynamical system. The F-ring is gravitationally held by the "shepherd" moons: Prometheus and Pandora. According to one of the theories, it is due to the partial destruction of two satellites colliding with each other, which later became "shepherds". In addition, another small satellite was discovered inside this ring, introducing additional complications in the dynamics of the object.
Ring of Janus-Epimetheus
The ring of Janus-Epimetheus is marked with a cross
The F ring is followed by a very faint object - the Janus-Epimetheus ring. It is notable in many ways because of what it was thanks to "Cassini". It was through the Janus-Epimetheus ring that the apparatus recently flew, examining the composition and size of the particles in it. By the way, the next "dive" is scheduled for December 11, 2016.