Rings of Saturn
Written by Fraser Cain
The rings of Saturn are one of the most dramatic features in the whole Solar System. These beautiful translucent rings are made of water ice, and might be as old as Saturn itself. Even though Saturn has been visible in the night sky for the history of humanity, it wasn't until Galileo first turned his telescope on Saturn in 1610, that astronomers knew there was something unusual about Saturn – the planet has rings.
Saturn's rings are made up of particles of water ice, ranging in size from the microscopic, to boulders larger than a house. They start just 6,630 km above Saturn's equator, and extend out to a distance of 120,700 km. Even though they stretch out for thousands of km, Saturn's rings average just 20 meters in thickness.
There are two large gaps in the rings, called the Cassini Division and the Encke Gap. The Cassini division – which is 4,800 km wide – was discovered by Giovanni Domenico Cassini in 1675. These gaps are cleared out and maintained by tiny moons that orbit Saturn called shepherd moons.
The various rings around Saturn have been designated with letters. The three main sections that we can see, even from telescopes on Earth, are the A, B, and C rings. The A ring is the furthest out, B is closer, and the darker C ring orbits closest to Saturn. Since they were originally designated, the lettering scheme now goes up to the G ring.
Astronomers have a few theories about where Saturn's rings came from. It's possible that they've been around since almost the beginning of the Solar System, when a 300 km ice moon was shattered by Saturn's gravity. It's also possible that the ice particles in the ring just failed to come together as a moon, and have never been a larger object. Based on the clarity of the ring material, and lack of dirt from meteorites, it's also possible that the rings are just 100 million years old. The origin of the rings is still one of the big mysteries in astronomy.
Here's an article from Universe Today about how the rings could be as old as the Solar System, and another about how they might only be a few hundred million years old.
Wikipedia has one of the best articles on Saturn's rings, and NASA's Solar System Exploration page.
We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn's Moons.
Filed under: Astronomy
