July 1, 2004 marked an historical first in the exploration of the Solar System. The Saturn Orbital Insertion maneuver took place when the Cassini spacecraft flew through the large gap between Saturn’s F and G rings. The event was the first time a man-made object was placed into orbit around that planet.
All four of the gas giant planets, Jupiter, Saturn, Uranus, and Neptune have visible ring systems. However, the most spectacular and fascinating rings are those that grace Saturn.
The intellectual who is credited with first describing Saturn’s rings was the Dutch “renaissance man” Christiaan Huygens. In 1655, when he was still a university student, Huygens developed an improved telescope lens. The use of the lens enabled the student to discover Saturn’s largest moon, Titan.
The next year, Huygens discovered the rings around Saturn. Huygens went on to write his “Systema Saturnium” compendium. The Saturn work was only a part of his long line of more discoveries and inventions. Even though Galileo was the first to describe Saturn as having “arms”, Galileo’s telescope was too primitive to discern anything but a blurry image of the planet, so Huygens gets the credit for describing the formations as rings.
The Cassini-Huygens spacecraft mission was set up to achieve many other firsts, including the joint mission with the Huygens Probe’s landing on the Saturnian moon, Titan, that happened in December of 2004.
During the next few years, NASA reported that Cassini photographs enabled astronomers to discover seven additional small moons orbiting within the Saturn Ring System. Last spring, NASA told the public about the beginnings of the possible formation of yet another moon inside of the A Ring.
NASA and the European Space Agency describe the Rings of Saturn this way: They have a thickness of approximately one kilometre (less than 1 mile). They span more than 282,000 kilometres. Each ring is comprised of various sized “particles” that range from hundredths of a metre up to the size of mountains. Some astronomers believe that the rings are the remnants of shattered former moons along with captured asteroids, and pieces of comets.
Each ring has a different orbital speed. This difference causes the gaps between the rings. Some of Saturn’s moons also keep the gaps “clean” by attracting small particles to them. The gap named “Cassini” is not the gap that the Cassini Spacecraft flew through. The F and G gaps are closer to the planetary surface. Saturn’s rings are very highly structured. Why the rings are so geometrically and highly structured is still an astronomical mystery.
Saturn’s rings are named alphabetically in the order they were discovered. Going outward, away from the planet are the most visible rings, C, B, and A. The other rings are more faint and closer to the planet, itself. They include the D, F, G, and E rings.
The most recently discovered ring exists very far away from Saturn. NASA’s Spitzer Space Telescope enabled astronomers to see an enormous, barely visible, outer ring. The inner boundary begins about 6,000,000 kilometres from Saturn and extends to some 12,000,000 from the surface. The “new” outer ring is the thickest of the rings. It is described as being 20 times the diameter of the planet Saturn.
The composition of this ring is extremely light so the ring is nearly invisible. There are only about 20 tiny particles within each square kilometre. Saturn’s outermost moon, Phoebe, orbits within this ring. Some scientists believe Phoebe may be the source of the small dust particles.
Regardless of whether new rings are discovered or new facts emerge about the rings we know about, Saturn’s Rings will probably remain judged as magnificent wonders of the Solar System.