April: Saturn on Display

April 2008

Saturn on Display

By Calvin L. Chrisman

The amazing planet Saturn will be prominent in the night sky during the month of April. After sunset at the beginning of the month, it will be almost directly overhead in the constellation Leo. Look up and a bit to the east, and you will see Saturn very near the star Regulus. Regulus is the brightest star in Leo; represents its front foot and is just below the curve of stars which make up the “sickle” of Leo, the lion’s mane. Saturn is named after the Roman god of the harvest who was the father of Jupiter.

Saturn and It's Rings
Saturn and It’s Rings

Saturn is a breath-taking sight through a telescope. Any amateur telescope of four inches or larger will resolve its rings and will lead to exclamations of surprise and pleasure for first time observers. If you or a friend has access to a telescope, take advantage of this opportunity to see this very special sight. At present, Saturn is near opposition (directly opposite the Sun from us) and so is very bright. You should be able to resolve the rings, one or more divisions within the rings and bands of color on the planet.  The rings are Saturn’s most famous feature, but it is also rich in moons. To date, over fifty have been discovered by ground-based telescopes and various satellite fly-bys. Through amateur telescopes, six are visible. Various web sites and magazines give tables to help you locate them.

Saturn is, at present, about nine times as far from the Sun as is the Earth. It takes 29.5 Earth years to complete an orbit of the sun, but its day lasts only 10.2 hours. It is a giant gas ball and this rapid rotation on its axis makes its shape noticeably flattened from a sphere. This oblateness is clearly visible through a telescope.  The planet is 91% as tall as it is wide.

The rings are made up of rocky rubble and ice which are thought to be the result of one or more moons getting too close and being pulled apart by Saturn’s strong gravitational pull. The rings extend for over 170,000 miles but are only a few yards thick! Spacecraft have shown the rings to be made up of hundreds of separate divisions, but only three are visible through amateur telescopes. The Cassini division, which separates the A and B rings is as wide as the United States, but appears as a small dark line in a telescope. As Saturn, which is tipped on its rotational axis, moves through its orbit around the Sun, it presents us on Earth with different views of its rings, allowing us to see the top and the underside at various times. Its maximum tilt to us was in 2003 at 27 degrees. Currently, the tilt is approximately 10 degrees. By the end of this year, they will be only slightly tilted and will be edge-on, effectively disappearing for a period, late in 2009. April is a great time to take a look.

Clear Skies!


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