10-05-2008 Beautiful Saturn (Article 136)

[Simon Kenny]

Beautiful Saturn (Article 136)

The planet Saturn is now visible in the eastern sky after sunset in the constellation of Leo. Saturn is the second largest planet in the solar system, second only to Jupiter. Like Jupiter, it is a giant planet mainly composed of gas, mostly hydrogen. Although Saturn is large enough to hold several hundred Earth sized planets within its interior, it has a very low density. Indeed, if a swimming pool was big enough to contain Saturn, it would actually float. Saturn lies outside the orbit of Jupiter and orbits the sun every 29 years.

Saturn is a beautiful sight in a telescope. Even a very small telescope will reveal the disk of the planet and its magnificent rings. Indeed, even small binoculars will reveal that the planet has an uneven shape due to the rings. When Galileo first turned his telescope towards Saturn, he described the planet a having “ears”. The “ears” were the rings that his simple telescope was unable to resolve clearly. It is worth bearing in mind that a simple inexpensive pair of modern binoculars is vastly superior to the crude telescope that Galileo used to make his many discoveries.

The rings of Saturn are composed of small lumps of frozen gas and water, most no larger than a pebble, which reflect sunlight back to us. Amazingly, the rings are less than 1 mile thick and yet they are over quarter of a million miles across. As Saturn moves in its orbit around the sun, the rings appear to open and close due to our line of sight with the planet. At present, the rings are beginning to close, as seen from Earth, and by next year they will be all but invisible in small telescopes. This year is a good opportunity to observe Saturn and it rings as it is well placed high in the sky.

A small telescope will also reveal Saturn’s largest moon, Titan, as a small point of light close to the planet. Titan is an interesting world. Similar in size to our own Moon, it has a dense atmosphere, mainly composed of methane. In many ways it resembles how the early Earth may have looked billions of years ago before life began to form. The recent joint NASA/ ESA Cassini-Huygens mission to Saturn managed to land a probe on the surface of Titan revealing the surface of this strange world to us for the first time.

If you have a small telescope or binocular, take the opportunity to locate and observe Saturn. You will not be disappointed.