Bryan Preston (NASA/STScI)

As Saturn revolves around the Sun on its 29-year orbit, its ring system changes orientation for observers on Earth. At times, the rings are edge-on and almost invisible, other times they are tilted, giving us a more face-on view. Like Earth, Saturn's rotational axis is tilted with respect to its orbital plane. This tilt is 27°, similar to the 23° tilt of Earth. As Saturn makes its way around the Sun, sometimes the northern hemisphere is tilted toward the Sun, sometimes the southern hemisphere receives more direct sunlight. The rings are aligned with the Saturnian equator. Therefore, when there is an equinox on Saturn (that is, the Sun is directly over the equator), the rings appear as a thin, almost invisible line. As Saturn approaches its solstices, the planet is tilted toward or away from us, allowing us to see more of the ring system. These Hubble Space Telescope images show Saturn's rings from an equinox (edge-on) to the Northern Hemisphere winter solstice (face-on). The images were taken between 1996 and 2000.

Saturn's Rings

Saturn's rings were discovered over 300 years ago. They are composed of mainly dusty water ice particles that range from grain size up to huge boulders. The system of rings is about 70,000 km (45,000 miles) wide and only about 10 meters (30 feet) thick. These particles all orbit Saturn, constantly colliding and bumping into one another. The rings maintain their shape because of the gravitational influence of Saturn and its many moons.

Ellen Cohen