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Spacecraft unlocking the many mysteries of Saturn

February 7, 2008 12:15 am

INCREDIBLE! WOW! Unbelievable! Those are a few of the comments I heard when people first saw the planet Saturn through the eyepiece of my telescope.

Of course, Saturn's great appeal comes from its magnificent ring system. Although rings also circle Jupiter, Uranus, and Neptune, Saturn's rings are the most vivid, intricate and beautiful in the solar system.

This month, Saturn is well placed for viewing as it lies in the opposite direction from the sun in our night sky. It will remain an easy object to spot throughout the spring and early summer this year.

Saturn is the second-largest planet in the solar system and was the outermost planet known to the ancients who did not possess any optical aids. It is composed mainly of hydrogen and helium and takes 29.5 years to complete one orbit around the sun. It boasts some of the fastest winds in the solar system, blowing at 1,000 miles per hour. The winds create the pastel-colored cloud bands on the planet visible with larger telescopes, but the cloud bands pale in comparison to the planet's magnificent ring system.

For all their beauty, Saturn's main rings are only about 33 feet thick according to the latest data from the ongoing Cassini-Huygens mission. The rings are composed mainly of ice in sizes as small as sand grains to as large as automobiles.

Although several rings are visible with the largest Earth-based telescopes, the Voyager 1 and 2 spacecraft showed many more as they flew by Saturn in the 1980s. The Voyager encounters showed the rings are composed of thousands of separate ringlets, not unlike the grooves in old phonograph records, along with strange features resembling spokes in the rings not visible from Earth.

The Voyager missions opened a new chapter on Saturn in the 1980s, but a different mission named Cassini-Huygens is rewriting the Saturn textbooks for the new millennium.

The Cassini-Huygens spacecraft has continued where the Voyagers left off. Cassini-Huygens was launched in 1997 on a mission to Saturn and its largest moon, Titan, and has been taking magnificent photos and conducting detailed studies of the planet and its fascinating moons since it arrived in orbit around the planet in 2004.

The main four-year mission will come to an end in July, but it's possible that the mission will be extended, depending on the health of the spacecraft. Check out this fascinating mission at saturn.jpl.nasa.gov.

Saturn's moons are also of great interest. According to the latest data from the Cassini-Huygens mission, Saturn has 60 moons.

Its largest moon, Titan, is bigger than Mercury and Pluto. Titan possesses an atmosphere thicker than Earth's. This opaque atmosphere kept the moon shrouded in mystery until January 2005 when the Huygens space probe snapped some very interesting photos as it descended via parachute onto Titan's surface.

Another Saturnian moon named Mimas has a huge crater dominating almost a third of its surface and resembles the Death Star from the "Star Wars" movies. Another moon named Iapetus has one side that is very bright and one side that is very dark. Many other Saturnian moons have interesting features as well. You can learn more about all of them from the Cassini-Huygens Web site, a great source of detailed information and photos.

February Skies

Beautiful Saturn and a total lunar eclipse warm up the cold February skies during the evening of Feb. 20.

From the Fredericksburg area, the moon will begin to enter the Earth's shadow around 8:45 p.m. and will be totally engulfed by the Earth's shadow by 10 p.m., where it will remain for almost an hour.

Saturn will be well-placed for viewing to the left of the eclipsed moon during the event. Remember that a lunar eclipse, unlike a solar eclipse, is entirely safe to view with unaided eyes, binoculars, or telescopes, so don't hesitate to view the eclipse and Saturn at the same time. This will be the last total lunar eclipse until December 2010, so check it out if the skies are clear.

Saturn is well placed for viewing all month since it will be directly opposite the sun on Feb. 24 when it rises in the east as the sun sets in the west. In addition to being near the moon during the evening lunar eclipse of Feb. 20, Saturn will lie close to the moon on the morning of the 21st for early morning risers.

Mars loses some of its brilliance this month, but it's still a noticeable object in the evening sky two months after its closest approach to Earth. It will be paired with the moon during the evening of Feb. 15.

Venus is getting lower in the morning sky, but it's still visible before sunrise and will be close to dimmer Jupiter during the first week of the month. The pair will continue to separate as the month progresses with Venus sinking lower and Jupiter rising higher.

The Rappahannock Astronomy Club hosts monthly star parties where you can view Saturn and other celestial objects through different telescopes. For more information, go to raclub.org/

David Abbou of Stafford County conducts public outreach on astronomy and the space program as a NASA JPL Solar System Ambassador. He is a member of the Rappahannock Astronomy Club. Contact him at david.abbou@ verizon.net