Steamboat Springs Four bright planets will march across our early evening sky this month. Jupiter and Mars already have been in place for weeks, but Saturn will join the planet parade next week, and a little later in the month, Mercury will join in.
Jimmy Westlake's Celestial News column appears Tuesdays in the Steamboat Today.
Find more columns by Westlake here.
On Saturday, the ringed planet Saturn will be at its closest point to Earth for the year — a point called opposition. At 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 Saturday, Saturn will be 8.9 astronomical units (828 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 later before Christian Huygens realized that a flat ring encircled Saturn’s equator. The ring is not solid but is composed of billions of tiny ice particles, probably particles blasted off of Saturn’s small, icy moons by the impacts of meteoroids.
And, speaking of moons, Saturn has quite a large family of moons orbiting around it. To date, astronomers know of 62 moons orbiting the solar system’s second largest planet. The biggest, by far, is Titan — a Mercury-sized moon with a thick, cloudy atmosphere.
Saturn, Titan and many other Saturnian 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 to understand the mysteries of this distant world.
Check out the latest amazing Cassini images of Saturn at the website 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 located in the heart of the constellation of Libra, the Scales, between the two brightest stars of Libra, Zubenelgenubi and Zubeneschamali. These two tongue-twisting names mean “the Northern Claw” and “the Southern Claw” and harken back to a time when the two stars marked the claws of the nearby scorpion.
If you own a telescope — even a small one — try aiming it at Saturn. Saturn offers the biggest “wow” factor of any other 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 of May 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,” about four ring diameters beyond the edge of the rings. You might catch a glimpse of several 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 beside the moon in our sky: May 13 and 14, June 9 and 10 and July 7.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. His "Celestial News" column appears weekly in the Steamboat Today newspaper and his "Cosmic Moment" radio spots can be heard on local radio station KFMU. Check out Jimmy’s astrophotography website at www.jwestlake.com.