Sky and Telescope - May 2012 - (Page 25)
Storm remnant zone
NASA / JPL-CALTECH / SPACE SCIENCE INSTITUTE / ADDITIONAL PROCESSING BY S&T: SEAN WALKER
THE STORM SUBSIDES This Cassini image taken on January 17, 2012, shows that the storm and tail have subsided to a level where there remains very few traces of their former glory.
all formed from the same elements in the solar nebula. In order to reproduce the structure and motions of the GWS clouds, the winds we measured at the upper-ammonia-cloud level must extend in depth without diminished speed to at least the water clouds, below the level where solar radiation penetrates. The development of the GWS produced small changes in the structure of the wind system at the latitude of the storm. But the westward jet at 40° north remained essentially unchanged by the action of the GWS. All of these characteristics of Saturn’s winds suggest that motions in the upper cloud layers are probably deeply rooted to the massive atmosphere that extends down to about half the planet’s radius (30,000 km). The internal heat emanating from Saturn’s depths, coupled to the planet’s rapid rotation, could be driving the high-speed winds we observe at the cloud tops. This is different than on Earth, where winds are driven by solar radiation.
Remaining Mysteries
Despite the groundbreaking observations of the 2010 storm, there are many unsolved questions raised by the GWS phenomenon. For example, why are these giant storms so rare, with only one per Saturn year? Probably
different contributing factors must occur simultaneously in the atmosphere to trigger a GWS. On the other hand, if these giant storms are seasonally forced, how does the small and slow seasonal temperature variation in the upper atmosphere propagate 250 km downward to the water cloud level? And why did the 2010 event take place about 10 years before the usual summertime period when other Great White Spots were observed? Another mystery is the GWS’s confinement to three latitude bands in the northern hemisphere (three at the equator, two at mid-latitudes, and one at a sub-polar latitude). Perhaps this effect is related to the shear of the zonal jets that change with latitude. But Saturn’s jets are symmetrical by hemisphere, and don’t seem to favor the north or south. It’s possible that GWS phenomena many decades ago went undetected in the southern hemisphere, where they were obscured by the rings and their shadows on the globe, or that they took place when Saturn was hidden behind the Sun from Earth’s perspective. If the GWS occurs at a rate of one per Saturn year, the next one should not erupt until the 2040s. Perhaps then new observations will solve these and other mysteries. But before the next outbreak, scientists will continue to analyze and interpret the plethora of data from the 2010 storm retrieved by Cassini and ground-based observatories. ✦ Agustín Sánchez-Lavega is Professor of Physics at the Universidad del País Vasco in Spain. He is author of the book An Introduction to Planetary Atmospheres (2011).
Sk yandTelescope.com May 2012 25
To see more images of Saturn’s superstorm, visit skypub.com/saturnstorm.
Table of Contents for the Digital Edition of Sky and Telescope - May 2012
Sky and Telescope - May 2012
Table of Contents
Spectrum
Letters
75, 50 & 25 Years Ago
News Notes
Saturn’s Raging Superstorm
Stars Above, Earth Below: Astronomy in National Parks
The Remarkable Case of Comet Lovejoy
In This Section
May’s Sky at a Glance
Binocular Highlight
Planetary Almanac
Northern Hemisphere’s Sky
Sun, Moon, and Planets
Celestial Calendar
Exploring the Solar System
Deep-Sky Wonders
Going Deep
S&T Test Report
New Product Showcase
Telescope Workshop
Planetary Imaging with Your DSLR Camera
Gallery
Focal Point
Sky and Telescope - May 2012
Sky and Telescope - May 2012 - (Page Intro)
Sky and Telescope - May 2012 - Sky and Telescope - May 2012 (Page Cover1)
Sky and Telescope - May 2012 - Sky and Telescope - May 2012 (Page Cover2)
Sky and Telescope - May 2012 - Sky and Telescope - May 2012 (Page 3)
Sky and Telescope - May 2012 - Table of Contents (Page 4)
Sky and Telescope - May 2012 - Table of Contents (Page 5)
Sky and Telescope - May 2012 - Spectrum (Page 6)
Sky and Telescope - May 2012 - Spectrum (Page 7)
Sky and Telescope - May 2012 - Letters (Page 8)
Sky and Telescope - May 2012 - Letters (Page 9)
Sky and Telescope - May 2012 - 75, 50 & 25 Years Ago (Page 10)
Sky and Telescope - May 2012 - 75, 50 & 25 Years Ago (Page 11)
Sky and Telescope - May 2012 - News Notes (Page 12)
Sky and Telescope - May 2012 - News Notes (Page 13)
Sky and Telescope - May 2012 - News Notes (Page 14)
Sky and Telescope - May 2012 - News Notes (Page 15)
Sky and Telescope - May 2012 - News Notes (Page 16)
Sky and Telescope - May 2012 - News Notes (Page 17)
Sky and Telescope - May 2012 - News Notes (Page 18)
Sky and Telescope - May 2012 - News Notes (Page 19)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 20)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 21)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 22)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 23)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 24)
Sky and Telescope - May 2012 - Saturn’s Raging Superstorm (Page 25)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 26)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 27)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 28)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 29)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 30)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 31)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 32)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 33)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 34)
Sky and Telescope - May 2012 - Stars Above, Earth Below: Astronomy in National Parks (Page 35)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 36)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 37)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 38)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 39)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 40)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 41)
Sky and Telescope - May 2012 - The Remarkable Case of Comet Lovejoy (Page 42)
Sky and Telescope - May 2012 - In This Section (Page 43)
Sky and Telescope - May 2012 - May’s Sky at a Glance (Page 44)
Sky and Telescope - May 2012 - Binocular Highlight (Page 45)
Sky and Telescope - May 2012 - Planetary Almanac (Page 46)
Sky and Telescope - May 2012 - Northern Hemisphere’s Sky (Page 47)
Sky and Telescope - May 2012 - Sun, Moon, and Planets (Page 48)
Sky and Telescope - May 2012 - Sun, Moon, and Planets (Page 49)
Sky and Telescope - May 2012 - Celestial Calendar (Page 50)
Sky and Telescope - May 2012 - Celestial Calendar (Page 51)
Sky and Telescope - May 2012 - Celestial Calendar (Page 52)
Sky and Telescope - May 2012 - Celestial Calendar (Page 53)
Sky and Telescope - May 2012 - Exploring the Solar System (Page 54)
Sky and Telescope - May 2012 - Exploring the Solar System (Page 55)
Sky and Telescope - May 2012 - Deep-Sky Wonders (Page 56)
Sky and Telescope - May 2012 - Deep-Sky Wonders (Page 57)
Sky and Telescope - May 2012 - Deep-Sky Wonders (Page 58)
Sky and Telescope - May 2012 - Deep-Sky Wonders (Page 59)
Sky and Telescope - May 2012 - Going Deep (Page 60)
Sky and Telescope - May 2012 - Going Deep (Page 61)
Sky and Telescope - May 2012 - Going Deep (Page 62)
Sky and Telescope - May 2012 - Going Deep (Page 63)
Sky and Telescope - May 2012 - S&T Test Report (Page 64)
Sky and Telescope - May 2012 - S&T Test Report (Page 65)
Sky and Telescope - May 2012 - S&T Test Report (Page 66)
Sky and Telescope - May 2012 - S&T Test Report (Page 67)
Sky and Telescope - May 2012 - New Product Showcase (Page 68)
Sky and Telescope - May 2012 - New Product Showcase (Page 69)
Sky and Telescope - May 2012 - Telescope Workshop (Page 70)
Sky and Telescope - May 2012 - Telescope Workshop (Page 71)
Sky and Telescope - May 2012 - Planetary Imaging with Your DSLR Camera (Page 72)
Sky and Telescope - May 2012 - Planetary Imaging with Your DSLR Camera (Page 73)
Sky and Telescope - May 2012 - Planetary Imaging with Your DSLR Camera (Page 74)
Sky and Telescope - May 2012 - Planetary Imaging with Your DSLR Camera (Page 75)
Sky and Telescope - May 2012 - Gallery (Page 76)
Sky and Telescope - May 2012 - Gallery (Page 77)
Sky and Telescope - May 2012 - Gallery (Page 78)
Sky and Telescope - May 2012 - Gallery (Page 79)
Sky and Telescope - May 2012 - Gallery (Page 80)
Sky and Telescope - May 2012 - Gallery (Page 81)
Sky and Telescope - May 2012 - Gallery (Page 82)
Sky and Telescope - May 2012 - Gallery (Page 83)
Sky and Telescope - May 2012 - Gallery (Page 84)
Sky and Telescope - May 2012 - Gallery (Page 85)
Sky and Telescope - May 2012 - Focal Point (Page 86)
Sky and Telescope - May 2012 - Focal Point (Page Cover3)
Sky and Telescope - May 2012 - Focal Point (Page Cover4)
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