Jimmy Westlake: Saturn joins the planet parade
March 29, 2011
Saturn's giant, smoggy moon Titan looms large behind Saturn's razor-thin rings in this Cassini spacecraft image radioed to Earth in October 2007. The tiny ice-moon Epimetheus seems suspended over the icy rings. Cassini continues to orbit Saturn and return stunning images and data to Earth. Catch Saturn with the unaided eye in spring as it passes closest to Earth in early April.
Steamboat Springs — On Sunday, the ringed planet Saturn will be at its closest point to the Earth for the year, a point called opposition. At the moment of opposition, the Earth is positioned directly between Saturn and the sun, placing the two planets as close together as they can be. Oppositions of Saturn happen about every 12 1/2 months as the faster-moving Earth gains a lap on Saturn and catches up to it from behind. This year on Sunday, Saturn will be 804 million miles from Earth.
When Galileo first pointed his telescope at Saturn in 1610, he noticed what looked like "ears" or "cup handles" on either side of the planet. It was about 50 years later before Christiaan Huygens recognized that a flat ring encircled Saturn's equator. The ring is composed of billions of tiny ice particles, probably particles blasted off one or more of Saturn's small, icy moons by the impact of a comet.
And speaking of moons, Saturn has quite a large family of worlds and mini-worlds orbiting it. To date, astronomers know of 60 moons orbiting Saturn. The largest is Titan, a Mercury-sized moon with a thick, cloudy atmosphere. Saturn, Titan and many other moons are being studied right now by NASA's Cassini spacecraft, which was placed into orbit around Saturn in July 2004. Spectacular photographs of the Saturn system are beamed back to Earth daily, helping us understand the mysteries of this distant world. Check out the latest Cassini images of Saturn at http://saturn.jpl.nasa.gov.
You can spot Saturn, without any optical aid, rising in the eastern sky shortly after sunset this month. It appears as a bright, yellowish star that doesn't twinkle like a regular star, but gleams with a steady light. This year, Saturn is positioned in the constellation Virgo, about a hand-span above the bright star Spica and even closer to the somewhat fainter star Porrima. Watch Saturn pull closer and closer to Porrima each week until June 8, when it stops just 1/4 degree short, then reverses course and pulls away week by week. Saturn's slow drift among the stars is because of a combination of its own orbital motion and Earth's orbital motion around the sun.
If you own a telescope — even a small one — try aiming it at Saturn. Saturn offers the biggest "wow" factor of any other object visible through a small telescope. You can easily see for yourself Saturn's magnificent icy rings and its largest moons. Try looking on April 5, 13, 21 and 29 when the giant moon Titan appears farthest away from the rings and is easiest to spot. Titan will look like a little orange star just beyond the edge of the rings. You might see several other fainter moons hanging around the rings, as well.
— Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published all around the world. Check out Westlake's website at http://www.jwestlake.com.