Jimmy Westlake: Saturn moves into our evening sky
April 22, 2013
For the past few months, Jupiter has been the only planet visible during the early evening. Well, move over, Jupiter — Saturn is moving in.
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 occur 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 8.82 astronomical units (820 million miles) from Earth.
When Galileo first aimed 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 before Renaissance man Christiaan Huygens realized that a flat ring encircles Saturn's equator. The ring is not solid but is composed of billions of tiny ice particles, probably particles blasted off one or more of Saturn's small, icy moons by the impacts of comets.
And, speaking of moons, Saturn has quite a large family of worlds and mini-worlds orbiting around it. To date, astronomers know of 62 moons orbiting the solar system's second largest planet. The biggest moon, by far, is Titan — a Mercury-sized moon with a thick, cloudy atmosphere. Saturn, Titan and many other Saturnian moons are being studied 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 amazing 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 near the boundary between the constellations of Libra and Virgo, about a hand-span to the lower right of the bright star Spica. Together with the bright star Arcturus, Saturn and Spica form a distinctive isosceles triangle dominating the eastern sky after dark.
If you own a telescope — even a small one — try aiming it at Saturn. Saturn offers the biggest "wow" factor of any celestial object visible through a small telescope. You easily can see for yourself Saturn's magnificent icy rings and its largest moons. Try looking near the dates Thursday, May 3, May 11, May 19 and May 27, 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.
If locating Saturn among the myriad stars is challenging for you, try looking for it on one of these nights, when Saturn appears right next to the moon in our sky: Thursday, May 22, June 18, July 16 and Aug. 12.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Jimmy's astrophotography website at http://www.jwestlake.com.