Sky and Telescope - May 2012 - (Page 24)
Stormy Weather
0.01 0.06 0.1 0 66 90
Stratosphere Tropopause
Great White Spot
Stratospheric haze
Atmospheric pressure (bars)
Tropospheric haze
Upward velocity 150 meters/ second (335 mph)
1
Troposphere
Ammonia (NH3) clouds Ammonia hydrosulfide (NH4SH) clouds Water (H2O) clouds
S&T: LEAH TISCIONE / SOURCE: AGUSTÍN SÁNCHEZ-LAVEGA
190
10
370
CLOUD STRUCTURE According to the author’s model, the 2010 Great White Spot originated as a thunderstorm in a water cloud deep below the visible layers of Saturn’s atmosphere. The storm ascended rapidly into the troposphere, where it could be easily spotted by amateur and professional astronomers.
changes in the stratospheric winds and in the abundances of some minor gases that were detected with infrared instruments on ground-based telescopes and Cassini.
A Giant Thunderstorm
All of the evidence suggests that the initial GWS was a giant thunderstorm about 100 times the size of typical Earth storms. For example, intense lightning activity within the storm produced the radio outbursts in the head detected by Cassini on December 5, 2010. My colleagues and I have developed computer models of the GWS phenomenon that try to reproduce the observations and also probe the dynamical structure of Saturn’s atmosphere below the upper ammonia cloud
S AT U R N ’ S S E A S O N S Saturn seasons are due to the 26.7° tilt of the planet’s rotational axis with respect to the orbital plane. But at tropical and equatorial latitudes, the ring shadowing of the upper atmosphere varies during Saturn's orbit, which amplifies seasonal effects. Measurements of Saturn’s eastwest zonal winds during the last Saturn year show that they remained stable despite the planet’s strong seasonal cycle.
Ultraviolet
Methane
PROBING THE DEPTHS Don Parker took these images on January 2, 2011. The GWS appeared bright through an ultraviolet filter but was barely visible in an infrared (methane) filter. Images such as these show conditions at different altitudes, and support the idea that the original disturbance consisted of warm gas and ice crystals that ascended from deeper in the atmosphere.
layer. According to our models, Saturn’s 2010 GWS grew rapidly in brightness and area due to the formation and expansion of dense cumulus clouds of ammonia crystals — behavior somewhat like terrestrial thunderstorms. This is why we usually say that the GWS “erupts” in the planet. Accordingly, the storm clouds in the head resulted from hot, moist gas rising rapidly from Saturn’s deeper atmosphere. On Earth, the air is a mixture of nitrogen and oxygen, with water providing moisture. In contrast, Saturn’s drier atmosphere consists mainly of hydrogen and helium, with ammonia and water providing most of the moisture. Based on models of moist convection in Saturn’s atmosphere, we think that within the storm head, water-moist gas ascended from a depth of about 250 km below Saturn’s upper clouds at speeds of 150 meters per second (335 mph), about three times faster than the velocities typical of severe thunderstorms on Earth. High-resolution Cassini images of the GWS head showed abundant clusters of cumulonimbus (tall, vertical) clouds that appeared as a single compact bright spot in unresolved ground-based images. This observation supports our thunderstorm model. Another important conclusion from our models is that Saturn’s water abundance must have been high where the GWS erupted, about five times or more than the amount we expected from the Sun’s abundance of oxygen, which is taken as a reference for the giant planets because they
24 May 2012 sky & telescope
Depth (kilometers)
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)
https://www.nxtbook.com/nxtbooks/test_scenarios/20120304_clone_2
https://www.nxtbook.com/nxtbooks/test_scenarios/20120304_clone
https://www.nxtbook.com/nxtbooks/test_scenarios/archaeology/20120304
https://www.nxtbook.com/nxtbooks/test_scenarios/ft_201205
https://www.nxtbook.com/nxtbooks/test_scenarios/newtrack/loq_20120304
https://www.nxtbook.com/nxtbooks/test_scenarios/newtrack/st_201205
https://www.nxtbook.com/nxtbooks/test_scenarios/journalpubs/northcarolina_2012travelguide_v2
https://www.nxtbook.com/nxtbooks/test_scenarios/binghamton/researchmag_2012springsummer
https://www.nxtbook.com/nxtbooks/test_scenarios/wj_april2012
https://www.nxtbookmedia.com