Astro Bob A look at celestial happenings in the Northland and beyond Bob King View my profile Click here to view previous posts or additional resources

Saturn's at its best plus get ready for Mercury's dashing show

Watch for Mercury to return to the evening sky this coming week. You'll need binoculars to find it tonight and tomorrow but it will soon become more easily visible with the naked eye. Created with Stellarium

I may be pushing this a little early but I'm excited to promote Mercury's best appearance in the evening sky this year for those living in mid-northern latitudes. Those with an oceanic or "Great Plains" view of the western horizon can begin looking for Mercury as soon as this week. First find much brighter Venus in the west about 30 minutes after sunset. Below Venus in the glow of the departed sun, binoculars may just reveal Mercury a couple degrees above the sunset point. Its visibility improves all week long so that by next weekend you'll find it right alongside Venus. When's the earliest you'll spot the innermost planet?

Expedition 22 Commander Jeff Williams, left, and Flight Engineer Maxim Suraev sit in chairs outside the Soyuz Capsule just minutes after they landed near the town of Arkalyk, Kazakhstan last Thursday. The men returned from six months on board the International Space Station. Williams is from Winter, Wisconsin. Photo Credit: NASA/Bill Ingalls

The International Space Station (ISS) has only two passes left in the current evening series for the Upper Midwest. Tonight it will appear at 7:33 p.m. very low in the southwest just above Venus and travel toward the southeast. Monday night's pass is even lower and a little fainter, too. It begins at 7:59 p.m. For ISS viewing times for your city, please click HERE and type in your zip code.

This photo by the Cassini spacecraft highlights the many gradations in the transparency of Saturn's inner rings. The dark shadows of the rings separate Saturn's southern hemisphere (bottom) in the bottom of from the north (top). The translucent C ring runs through the middle of the image. The denser B ring stretches across the top of the image. NASA/JPL/Space Science Institute

Earth and Saturn will form a line with the sun today as Saturn reaches its yearly opposition. Illustration: Bob King

Tonight Saturn will be at opposition to the sun and closest to the Earth for the year. Once a year Saturn and Earth line up on the same side of the sun together. From our perspective, the ringed planet rises at sunset directly opposite the sun, hence the term opposition. Saturn is located in Virgo just below the tail of Leo the Lion and makes a pretty sight in a small telescope as early as 9 o'clock in late March. The rings are tipped open only a little (3.2 degrees) so at low magnification in a small telescope Saturn looks like a ball with a stick poking out either end. This is as wide open as the rings will be until August. By year's end the tip will increase to 10 degrees and the planet will begin looking like its old self again.

Because Saturn's axis is inclined to its orbit, we're treated to a variety of views of the rings throughout the planet's 29.5 year orbital cycle. The rings are just starting to open up again in 2010 and are visible in telescopes that can magnify 20x and up. For a more extensive picture panel, click HERE. Credit: Adapted from Tom Ruen

The ring plane is a whopping 170,000 miles wide but a scanty 30 feet thick and consists primarily of boulders of ice with a sprinkling of rocks and dust. The rings shine by reflected sunlight, and because they're made of ice they're noticeably whiter and brighter than Saturn's gold-tinted globe. Saturn's equator is tilted 27 degrees relative to its orbit around the sun (similar to Earth's 23.5 degree axis tip) so as the planet circles the sun, we first see one side of the rings and then the other. Between the two extremes the rings are edgewise as they were last year. I hope you and I will have the pleasure of still being around in 2017 so we can enjoy a "full tilt" display.

You can take either the "blue" or "red" route to find Saturn. This map shows the sky as you face east around 10 o'clock. Start with the Big Dipper, high in the northeastern sky. Follow the arc of the handle down to Arcturus. Saturn is three "fists" to the right and above the star. Or you can shoot a line through the two end stars in the Dipper's bucket over to Regulus in Leo (about four fists away). Saturn is 2-3 fists below Regulus and a little brighter. Created with Stellarium

Posted by: rking@duluthnews.com on 3/20/2010 at 6:09 PM | Comments (0) | Permalink | Edit

Tags: daily updates, space station, astro bob, life, mercury, venus, iss, saturn, opposition, rings, cassini