You gotta admit, as far as planetary excitement, Jupiter has stolen the show the past couple years. In 2009 Australian amateur astronomer Anthony Wesley recorded a dark bruise from an asteroid impact. Then in 2010 he and fellow amateur astronomer Christopher Go caught the bright impact of yet another small asteroid in the planet’s cloud tops. This year Jupiter “lost” one of its stripes, the South Equatorial Belt, which is now in the process of reappearing. Between these happenings and the delightful shuttling of its moons in front of and behind the planet, there’s never been a dull Jovian moment.
But to remind us there’s more out there than Jupiter’s antics, Saturn, normally a reserved planet as far as cloud belt activity goes, has moved into the limelight this week with the appearance of a brilliant new white spot in its northern hemisphere. Amazingly, this spot was discovered by none other than the indefatigable Anthony Wesley. On December 10, Wesley photographed a big white cloud in Saturn’s North Tropical Zone through his 14 1/2-inch telescope. I spoke with him yesterday via e-mail and he confirmed that the new storm is bright and obvious to the eye in a moderate to larger-sized telescope.
“This is the brightest Saturn storm in decades.Â If you get a chance to see it visually then take it, it may be one of the rare “Great White Spot” (GWS) outbreaks on Saturn,” according to information posted by WesleyÂ on the Ice in Space website.
Saturn has belts like Jupiter, but they’re subtle and rather difficult to see in small telescopes. Even in larger scopes, while you’ll see more belts, they’re not nearly as changeable nor as colorful as Jupiter’s. However, about every 30 years (or so) since 1876, when Saturn’s northern hemisphere tilts toward the sun, a huge upwelling of fresh, white material rises from below and spreads across the planet’s upper cloud deck. One theory holds that storms shoot a blob of warmer gas from the lower atmosphere up through the darker clouds. As the gas chills, ammonia within crystallizes to form a white cloud of ice crystals that spreads over the older, darker layer. The most recent large storm or white spots seen before this week’s happened in 1994. It looks like we’re in for a good old-fashioned blizzard again – Saturn style.
I’m hoping for clear skies to get a look at the spot myself. The next viewing opportunity for the eastern half of the U.S. will be between about 5:30 and 7:30 a.m.Â CST Monday the 20th, when the “spot side” of the planet faces Earth at the same time the planet is up in the southeast before and at the start of dawn. For savvy amateurs planning their own viewing schedules, the longitude (CM=III) of the feature is currently 265 degrees.