Saturn is one of the most beautiful planets. It has spectacular rings, or as Galileo described them, ears. Saturn is the sixth planet from the Sun and the second largest in our Solar System.
Saturn is named after the Roman god of wealth and agriculture. Similar to Jupiter, the planet is made primarily of hydrogen and helium. Its core is solid and made of iron and nickle. The density of Saturn is less than that of water. This means that if you could find a big enough bath tub, Saturn would float in it!
It is very difficult to measure the rotation of Saturn but the best attempt to measure it puts the length of a day on Saturn at 10.7 hours. Saturn completes one orbit of the Sun every 29.4 years. Unlike Jupiter, Saturn’s atmosphere doesn’t have the same dramatic bands of cloud. There are variations in the colour of the bands but they are much fainter than Jupiter. One strange feature of Saturn’s atmosphere is the six sided jet stream at the planets north pole. This was first seen by the Voyager spacecraft and Saturn is the only place in the Solar System where we have seen anything like it.
The defining feature of Saturn is the rings. From a distance the rings appear to be solid and thick. This is not the case. The rings are actually made up of billions of bits of rock, dirt, ice and dust all orbiting the planet, and they are only about 10 meters thick! Scientists think that the material for the rings comes from comets, asteroids and moons ripped apart by the gravity of Saturn.
Saturn has lots of moons, 53 confirmed and 29 provisional. Some of these are just as strange and interesting as the moons of Jupiter. Two of the most intriguing are Titan and Enceladus. Titan is the largest of Saturn’s moons, being larger than Mercury and is the only moon in the Solar System that has a substantial atmosphere. As well as that, it is know to have rivers, lakes and seas of liquid methane and ethane on its surface. There is also liquid water in an ocean below the surface of the Titan. This means that it’s not inconceivable that it could host life on or beneath its surface.
Enceladus, is another fascinating world. It’s a very cold world with an icy surface. Beneath the frozen exterior is a liquid water ocean. Hydrothermal vents spray this ocean out into space, where spacecraft have actually been able to sample the material being sprayed out. From this we know that Enceladus contains most of the chemical components needed for life and it is speculated that there are hot thermal vents in the underground ocean. This means that Enceladus is a prime target in the search for life elsewhere in the Solar System.
Saturn has been known since ancient times and in 1610 Galileo pointed the telescope at it for the first time. His telescope wasn’t good enough to make out the rings but it could see that the planet wasn’t completely round in his eyepiece. He described it as having ears!
The fist spacecraft to fly by Saturn was Pioneer 11 in 1979. Voyager 1 and 2 both flew by the planet in 1980 and 1981 respectively. The first spacecraft sent specifically to explore the Saturn system was Cassini-Huygens. It was a collaboration between NASA, ESA and the Italian Space Agency. This was a 2 part spacecraft, Cassini went into orbit around Saturn, while Huygens landed on the surface of Titan. Cassini was in orbit around Saturn for over 13 years and returned a huge amount of scientific data. Among other achievements, it discovered new moons, helped measure the rotation speed and discovered lakes on Titan.
Saturn is one of the most beautiful sights you can see through a telescope. Even a small telescope will reveal the moons and rings of Saturn. This month is a particularly good month to see Saturn in a telescope. Saturn is at opposition which means it’s on the opposite side of the sky to the Sun. If you have a telescope, go out and have a look for yourself. If not, Saturn is visible in the south, as a star close to the horizon from around 11.30pm.
Paul Smith 