The rings of Saturn are a system of planetary rings surrounding the planet and were observed for the first time in July 1610. It was left to such merit to Galileo Galilee. In part because the images that gave the newly invented telescope, were of poor quality at that time, and partly because only a few months he had discovered the four largest satellites of Jupiter, was initially thought that fuzzy structures, like ears, I had seen, were two satellites close to Saturn. He soon changed his mind. Those “weird appendages” did not change its position relative to Saturn from one night to the next and also disappeared in 1612. It happened that the rings had been oriented with its plane as the sight from the Earth in 1612 and thus had become very weak. The geometry of the appendices puzzled astronomers, so much as to propose that it was linked to Saturn handles or consists of several satellites in orbit only around the back of Saturn, so it will never overshadow the planet.
Finally, in 1655, Christian Huygens suggested that the appendices were the visible sign of a disk of thin, flat material, separated from the planet and provisions of this equatorial plane. Depending on what were the positions of Saturn and Earth in their orbits around the Sun, the inclination of the disk relative to the Earth vary, hence their appearance also varies from a thin line to a wide ellipse. The cycle of the rings like Saturn’s orbit lasted 30 years.
During the next two centuries it was assumed that the disc was a continuous layer of material. The first objection against the hypothesis was soon, however, arising. In 1675, Giovanni Cassini found a dark band (the division that bears his name) that separated the disk into two concentric rings.
In the late eighteenth century, Pierre-Simon Laplace showed that the combined forces of sufficient gravity in the planet Saturn and the rotation of the disc to tear a single layer of material. In principle, any particle in the disk maintains its radial distance from Saturn because there are two forces are balanced. Gravity pulls the particle inward, the centrifugal force pushes out. The centrifugal force comes from the rotational speed; hence the disc has to be spinning. However, in the case of a rigid rotating disk, the forces are balanced only for a certain radial distance. Thus, Laplace proposed the hypothesis that the rings of Saturn were formed by many thin rings, enough each to support the slight imbalance of forces that appear along the radial width.
The last step towards the modern view of the rings came in 1857 when James Clerk Maxwell won the Adams Prize of Cambridge University for his mathematical proof that narrow rings were actually formed by many small bodies that orbit remained independent. The experimental verification of this hypothesis came in 1895 when American astronomers James E. Keeler and William W. Campbell deduced the velocity of the particles in the rings from their Doppler shift, or modification of the wavelength of the spectral lines of sunlight the particles reflect back to Earth. They found that the rings around Saturn revolved at a speed different from that of the planet’s atmosphere. In addition, the internal parts of the rings spinning faster than external, prescribed by the laws of physics for particles in independent orbits.
Features of the Rings
The main body of Saturn’s ring system includes the bright rings A and B, low opacity. Media from each other a stretch of 5,000 miles, the Cassini Division, a region relatively transparent, but not empty at all. The main body of the Saturn system also includes the C ring, weaker and less opaque, that is within the inner edge of ring B. He has a degree of opacity comparable to that of the Cassini Division. The even weaker ring D is in the ring C. Before the Voyager pass through the vicinity of Saturn already recognized the structural configuration of the planet’s rings A, B, C and D, observable from Earth, and Cassini Divisions and Encke. Taken together, the main rings of Saturn (A, B and C) are about 275,000 miles wide ring, which represents three quarters of the distance separating Earth from the Moon. The ring is divided into two parts by the Encke Division.
The photographs of the rings with high resolution, taken by Voyager and Cassini spacecraft provided many new features:
- Three very pale rings, E, F and G, which are outside of the ring A. In September 2006 another ring was found between the F and G.
- Appeared narrow annular regions of different brightness and opacity, as the grooves of a gramophone disc.
- We found also deviations from the circular shape.
- Appear knots, braids and twists in the F ring
- The ring has a uniform brightness in front of the B ring that has variations along their radial distances.
- In the outer ring there is a real belt “moonlets,” ranging in size from that of a small truck to a stadium
- In the B ring had radially oriented shocks, wedge-shaped.
- Groups of bands caused by resonance of satellites.
- Shepherd satellites producing gaps in the rings or fixing their edges.
The outer ring of the Encke Division shows a weak group of bands. The bands are tightly packed into the orbit of the satellite Prometheus, which was discovered in images taken by Voyager 1. It is believed that the bands are caused by resonances in the ring due to the gravitational effects of the satellite. The edge of ring shepherding satellite is maintained by the Atlas.
Pandora and Prometheus Image guarding the F ring of Saturn.
In addition, satellites Prometheus and Pandora are the shepherd satellites respectively inner and outer shaping the F ring of Saturn is 80 km wide.
Most of the gaps in Saturn’s rings are caused by the presence of shepherd satellites. Mimas, for example, is responsible for the existence of the greatest of them, the Cassini Division.
In comparison, the thickness of Saturn’s rings is negligible. The upper limit of its vertical extent has been estimated at about one kilometer. In relation to its width, the rings are thousands of times thinner than a razor blade.
Composition of the Rings
These rings have ability to reflect or absorb light of different wavelengths to deduce information about the composition of the particles of Saturn’s rings. For example, the rings A, B and C are poor reflectors of sunlight to certain wavelengths of near infrared. Because it is a characteristic property of ice, presumably the ice is an important constituent of the particles forming these rings. But it is a white ice, which means it is more or less equally reflector for all wavelengths in the visible. By contrast, the particles of the rings A, B and C are less blue light reflectors in red light. Perhaps there is some additional substance present in small quantities, dust perhaps, that behave as a source of iron oxide red color. It has also been hypothesized that certain compounds generated by solar ultraviolet radiation were responsible for the reddish color.
In 1973, he explored the rings of Saturn with radar waves (wavelength of the order of centimeters) whose reflection detected with 64-meter antenna of the Deep Space Network at Goldstone, California. If they were much older, they would have appreciated the emission of thermal radiation. The low level of radiation that limits their size is no more than a few meters.
Data from the Voyager spacecraft have confirmed these findings. In one type of experiment is radio waves sent from the spacecraft to Earth through the rings, and measured the power scattered by the particles in the rings for various angles of deviation from the initial course of the waves.
And the dissemination of radar waves by particles in the rings makes it possible to detect particles on the order of the size of the radar wavelength, the solar light scattering to detect particles the size of a wavelength of light visible. The strong increase in brightness of a segment of the ring, when viewed at an angle to the forward spread is small, implies that in this segment, there are many particles of a micrometer scale.
Observation can be undertaken only when Saturn is between the Sun and astrophysicist. This condition can not be met for verified observations from Earth, but aboard a spacecraft. Thus, studies of the Voyager data indicate that the particle sizes of the order of a micrometer constitute a large proportion of the particles in the F ring, a significant proportion in many parts of ring B and a smaller proportion in the outer the ring. On the other hand, the C ring and Cassini division have no traces of such small particles.
The diffusion of light or some other form of electromagnetic radiation by particles of a ring to deduce the size of the particles that abound in the ring:
Light scattering particle size of 1 / 10 of the wavelength of incident radiation: diffuses the light almost equally in all directions.
Light scattering of a particle size of the order of the wavelength of incident radiation: diffuses the light forward.
Light scattering of a particle larger than the wavelength of incident radiation: diffuses the light from all angles, predominantly forward.
Radio Spots In The B Ring
In the central and most opaque B ring are oriented radially about disturbances in the form of a wedge. Each of which can be seen along a substantial fraction of the 10 hours that a particle of the ring B invests in making an orbital revolution. Meanwhile, new radio spots are emerging sporadically in other parts of the ring. Compared with their environment, radio spots appear bright in forward scattered light and dark light scattered back. Hence, the particle sizes of the order of a micrometer in radio spots abound.
Every part of a wedge radial orbits Saturn at the same rate as do the ring particles to its radial distance. The interior portions move more quickly, thus, a radio spot will eventually bowed and never disappear. The narrow end (the “spike”) of each radio spot appears to coincide approximately with the distance from Saturn at which the period of a particle in orbit equals the rotation period of Saturn. The magnetic field of Saturn is enclosed inside the planet rotates, therefore, with him. Hence the electromagnetic forces are partly responsible for the existence of radio spots. In this respect it may be noted that there were outbreaks of static bandwidth. The outbreaks appear to have originated in sources of the B ring near regions where the activity of the wedges was intense.
The observation that the diffusion of light particles in the radio spots Saturn’s B ring occurs predominantly forward to deduce that the wedges are local and transient concentrations of ring particles of micrometer size.