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September 9, 2003 09:00 AM (EDT)

News Release Number: STScI-2003-23

The Slant on Saturn's Rings

September 9, 2003: This is a series of images of Saturn, as seen at many different wavelengths, when the planet's rings were at their maximum tilt of 27 degrees toward Earth. Saturn experiences seasonal tilts away from and toward the Sun, much the same way Earth does. This happens over the course of its 29.5-year orbit. This means that approximately every 30 years, Earth observers can catch their best glimpse of Saturn's South Pole and the southern side of the planet's rings. Between March and April 2003, researchers took full advantage to study the gas giant at maximum tilt. They used NASA's Hubble Space Telescope to capture detailed images of Saturn's Southern Hemisphere and the southern face of its rings.

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Q & A: Understanding the Discovery

  1. 1. Why did astronomers take pictures of Saturn in ultraviolet, visible, and infrared light?

  2. Various wavelengths of light—-in this case, ultraviolet to infrared—-allow researchers to see important characteristics of Saturn's atmosphere. Particles in Saturn's atmosphere reflect different wavelengths of light in discrete ways, causing some bands of gas in the atmosphere to stand out vividly in an image, while other areas will be very dark or dull.

    These Hubble images, taken over several wavelength bands, reveal the properties and sizes of aerosols in Saturn's gaseous makeup. For example, smaller aerosols are visible only in the ultraviolet image, because they do not scatter or absorb visible or infrared light, which have longer wavelengths. By determining the characteristics of the atmosphere's constituents, researchers can describe the dynamics of cloud formation. At certain visible and infrared wavelengths, light absorption by methane gas blocks all but the uppermost layers of Saturn's atmosphere, which helps researchers discern clouds at different altitudes.

  3. 2. Why are the rings tilted?

  4. Saturn and its rings are tipped 27 degrees with respect to the planet's orbit, which is very similar to the 23-degree tilt of the Earth. As Saturn makes its 29.5-year journey around the Sun, first one hemisphere, then the other is tilted towards the Sun. As the planet circles the Sun, the plane of its rings, therefore, changes in relation to Earth. That's why we get different views of the rings. Sometimes the rings seem to vanish because we are seeing them edge-on. Other times, about every 15 years, the rings are tipped toward Earth, providing a clear view of the entire ring system. This is the view captured by the Hubble telescope in these photographs.

  5. 3. What are Saturn's rings made of?

  6. The rings are made of dusty water ice, which range in size from boulders to sand grains. Saturn's gravitational field constantly disrupts these ice chunks, keeping them spread out and preventing them from combining to form a moon.

  7. 4. How many rings are there?

  8. Saturn's ring system is composed of tens of thousands of rings, called ringlets. In these images, the two classic divisions in the ring system can be seen. The narrow Encke Gap is close to the system's outer edge; the Cassini Division is the wider gap near the center.

  9. 5. How thin and wide are the rings?

  10. Saturn's ring system is about 170,000 miles wide (274,000 km) but only about 30 feet (10 meters) thick.

  11. 6. How did the rings form?

  12. Astronomers suspect that the pieces that make up the rings may be the remnants of a shattered object, such as a comet or asteroid, from the most distant region of the solar system.

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Credit: NASA and E. Karkoschka (University of Arizona)