Saturn Explained

Saturn's rings are wide, but they are very thin. Five of Saturn's many moons can be seen in this picture. Titan is the large moon on the left. The moons on the right — barely visible — are Mimus, Tethys, Janus, and Enceladus.

Photo courtesy of NASA

Saturn is the sixth planet from the sun and the second largest planet in the solar system. It is named for the Roman god of agriculture, one of the most important gods in the Roman world. Saturn is made mostly of hydrogen and helium, and its poles appear to be flattened because of its speedy rotation on its axis. Saturn's famous rings, which are the most distinctive feature of the planet, are composed of everything from dust to boulders to snowballs. Recently moons were detected in the rings. Although the main rings are more than 250,000 kilometers (more than 14,000 miles) wide, they are likely less than one kilometer thick.

Because the rings are slim, and because Saturn is tilted on its axis (like Earth), the rings disappear from our view for a short time. This occurs one to three times every 13 to 16 years. This event is known as a ring plane crossing. The last ring plane crossing was a triple (it was seen three times over a few months), and occurred during 1995 to 1996.

When seen from Earth, the rings of Saturn appear to all be the same color. However, in October 1997, the Cassini spacecraft was launched on a very long journey to Saturn. It arrived at the planet in June 2004, and successfully dropped the Huygens probe on the surface of Saturn's largest moon, Titan, in January 2005. Images were sent back to Earth from its narrow angle camera, which showed that the rings have different colors and brightnesses. It also showed that the ring system is made up of thousands of individual rings.

Scientists don't really know for sure how the rings of Saturn formed, but some think they are made of materials left over when Saturn was first formed. Others think the rings may be moons or asteroids broken to pieces.

Saturn Explained

Auroras occur on Saturn and on Earth. A special instrument aboard the Hubble Space Telescope took this picture of auroras at Saturn's north and south poles.

Photo courtesy of NASA

When Italian astronomer Galileo Galilei used the first telescope to study space, he was puzzled by Saturn's strange shape. We now know that it his confusion was caused by the rings, and possibly by the ring plane crossing. Galileo's small telescope couldn't see the rings, so the object looked like a blob.

A day on Saturn lasts 10.656 hours. A year on Saturn lasts over 29 Earth years. At Saturn's core, heavy elements probably have a temperature close to 15,000 Celsius and 27,000 Fahrenheit. Saturn is still settling gravitationally, which generates heat. Hence, Saturn radiates three times as much heat as it receives from the sun. The temperatures of Saturn's cloud tops are close to -176° Celsius and -285° Fahrenheit.

Auroras occur on Saturn (as they do on Earth). They occur at Saturn's north and south poles and extend more than 1,000 miles above Saturn's atmosphere.

This huge planet has a stormy atmosphere made up of hydrogen and helium. Winds have been clocked at 1,800 kilometers per hour (1,118 miles per hour) near Saturn's equator. These winds and the heat rising from its interior create bands in Saturn's outer atmosphere. These yellow and gold atmospheric bands are visible from Earth. Saturn's south pole is a very hot spot.

Saturn has at least 35 moons some astronomers think there are as many as 48. They range in size from giant Titan, which is larger than planets Mercury and Pluto, down to very tiny moons that orbit the planet in its rings. Information about Saturn and its moons is continuously relayed from the Cassini mission, which provides us with more answers … and more questions.