The dark grains of dust making up this faint ring are probably debris that cosmic impacts knocked off the gas giant's distant and equally dark moon Phoebe. This discovery just turns that idea on its head — the universe is a more interesting and surprising place than we thought.
Astronomers first suspected the existence of the Phoebe ring after looking at one of Saturn's other moons, Iapetus. That contamination is what led us to look for what turned out to be a surprisingly large ring. NASA's infrared Spitzer Space Telescope first detected the Phoebe ring extending between distances of to times the radius of Saturn — that is, from about 4. This made it about New infrared images from NASA's WISE spacecraft reveal the Phoebe ring actually extends between distances of to a surprisingly distant times the radius of Saturn — that is, about 3.
The dark grains making up the Phoebe ring absorb sunlight, which makes the ring difficult to see if one looks for visible light but much easier to see if one looks for heat in the form of infrared radiation, which the WISE spacecraft imaged. The researchers noted their new estimates are conservative ones. The Phoebe ring may actually extend between distances of 50 to more than times the radius of Saturn. The Phoebe ring is made up mainly of dust particles about 10 to 20 microns in size, or about one-tenth to one-fifth the average width of a human hair.
The seven main rings are labeled in the order in which they were discovered. The D ring is very faint and closest to Saturn. The main rings are A, B and C.
The outermost ring, easily seen with Earth-based telescopes, is the A ring. The Cassini Division is the largest gap in the rings and separates the B ring from the A ring. Just outside the A ring is the narrow F ring, shepherded by tiny moons, Pandora and Prometheus. Beyond that are two much fainter rings named G and E. Saturn's diffuse E ring is the largest planetary ring in our solar system, extending from Mimas' orbit to Titan's orbit, about 1 million kilometers , miles.
The particles in Saturn's rings are composed primarily of water ice and range in size from microns to tens of meters. The rings show a tremendous amount of structure on all scales; some of this structure is related to gravitational interactions with Saturn's many moons, but much of it remains unexplained. One moonlet, Pan, actually orbits inside the A ring in a kilometer-wide mile gap called the Encke Gap.
The main rings A, B and C are less than meters feet thick in most places, compared to their radial extent of 62, kilometers 38, miles. The main rings are much younger than the age of the solar system, perhaps only a few hundred million years old. They may have formed from the breakup of one of Saturn's moons or from a comet or meteor that was torn apart by Saturn's gravity.
The Cassini orbiter was designed, developed and assembled at JPL. Photojournal: PIA Topography and Albedo Image of Gegania Crater. Artist's concept of Cassini orbiter crossing Saturn's ring plane.
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This site is being redeveloped. Thus he saw that Saturn was surrounded by a ring system. Seeing even further was the Italian astronomer Giovanni Domenico Cassini , who discovered in that among the rings of Saturn there is a space that separates them into two well-differentiated zones, one more internal and another more external.
Today that space, almost empty and about 5, km wide, is called the Cassini Division. He proved mathematically that the force of gravity would break a thin body orbiting Saturn, so he predicted that the rings were composed of a large numbers of particles that floated around the planet.
Only by looking at them from as far away as Earth did they appear to be solid rings. We now know that his prediction was correct because of the images sent by the twin Voyager 1 and 2 spacecraft in the early s. Its images corroborated what we could see from Earth.
In addition, these photographs allowed the discovery of weaker areas, difficult to see at a great distance, located in the outermost part, the rings E, F and G. After its passage past the gas planet, Pioneer 11 continued its route towards the exterior of the Solar system. At the end of came the Voyager 1 probe, and in the middle of its twin, Voyager 2. This time we learned about the composition of the rings they consist of countless particles of ice and new structures of the ring system, as well as data about the atmosphere of Saturn and its larges.
After that visit, it would be 23 years before another spacecraft approached Saturn. It was then that planetary scientist Robin Canup , a researcher at the University of Colorado, published his theory in the prestigious scientific journal Nature.
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