A.L.P.O. Jupiter Alert
2002 January 26 / 2002 February 08
A consensus seems to be forming, within the amateur and professional astronomy communities, that south temperate oval BA should be expected to survive its conjunction with the GRS. Although BA may be affected in several ways, it will probably, according to Dr. Reta Beebe, be slowed somewhat then quickly be propelled past the GRS.
The visual appearance of BA being split or piled up on another oval was simply other cloud material circulating around BA, and being compressed between BA and the GRS currents.
Even though BA may not be disrupted, observers must remain alert. Jupiter has surprised us in past apparitions.
It is important to obtain visual observations documented with disk sketches or strip sketches depicting the GRS and BA interaction, CCD images, or visual central meridian transit timings. These kinds of observations should continue well after BA has passed the GRS.
The professional community is especially interested in any CCD images obtained in methane.
CCD images and scanned sketches may be sent to at John W. McAnally. Or mailed USPO to 2124 Wooded Acres, Waco, Texas, USA
76710. We can also provide A.L.P.O. observing forms.
John W. McAnally
The A.L.P.O. Jupiter Section
What's Up in Space -- 29 Jan 2002
Something extraordinary is happening on the planet Jupiter in full view of
amateur astronomers: Two gigantic storms are colliding. One is a "white oval"
-- a 70-year old hurricane nearly the size of Earth. The other is the famous
Great Red Spot -- a centuries-old tempest twice as wide as our planet.
The pair will likely converge during the weeks ahead, but it will not be a head-on collision because the two storms circle the planet at slightly different latitudes. Nevertheless, the encounter should be dynamic and entertaining. Sky watchers with 6" to 10" telescopes can view the action on clear nights with good atmospheric seeing. Consult a table of Great Red Spot transit times to decide when to look.
What's Up in Space -- 1 Jan 2002
NEW YEAR, GIANT PLANET
The giant planet Jupiter and our own planet Earth will have a close encounter on the first day of the New Year. The two worlds will lie just 4.19 astronomical units apart when Jupiter reaches "opposition" -- that is, a point in the sky directly opposite the Sun -- on January 1, 2002. New Year's Eve revelers in the northern hemisphere can easily find the planet. Simply look straight overhead at midnight: there lies Jupiter -- the brightest "star" in the sky.
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Astronomers have known since the early 1900s that the Great Red Spot's longitudinal extent has been decreasing. Late in the 19th century the spot was nearly 35 degrees wide, which corresponds to about 40,000 kilometers, or more than three times Earth's diameter.
By 1979, when Voyagers 1 and 2 swept past, it had shrunk to 21 degrees (about 25,000 km), yet its latitudinal "height" remained essentially unchanged, about 12,000 km from top to bottom.
Simon-Miller has discovered that the contraction seems to have picked up steam since the Voyager visits: at its present rate of shrinkage (0.19 degree in longitude per year), the spot will become the "Great Red Circle" by the year 2040. However a perfectly round shape is unlikely, she explains, because the strong, opposing jet streams that confine the spot's northern and southern boundaries will always distort it into an oval.
No one knows why the not-so-Great Red Spot has shrunk -- or, for that matter, why its color intensifies and fades over time. One clue is that the winds around its circumference are whirling 70 percent faster now (about 700 km per hour) than they were in the Voyager era. Some historical observations suggest that the Red Spot grows and shrinks in a decades-long sequence. "I'm not sure the behavior is really cyclical," Simon-Miller comments, "but I certainly would not be surprised in the least if this shrinking trend slowed or reversed."
One possible explanation is that deep-seated bursts of thunderstorm-like convection periodically energize the overlying cloud layers, causing the spot to bloat in size, then gradually contract as the turbulence subsides. "All of the weather on Jupiter seems to have sporadic increases in activity," she notes, "so whatever feeds the Great Red Spot likely will too."
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ROYAL ASTRONOMICAL SOCIETY
31st March 1998
The giant planet Jupiter is famous for its colourful, swirling clouds. The most notable feature among this ever-changing turbulence is the Great Red Spot, a huge storm system that could swallow up three Earths and is known to have existed for at least three centuries.
One of the instruments on board the Galileo orbiter being used to study the Jovian atmosphere and the Great Red Spot is the Near-Infrared Mapping Spectrometer (NIMS). The capability of NIMS to obtain spatial and spectral information simultaneously is ideal for investigating the composition, vertical layering, optical thickness, and fine structure of Jupiter's mysterious cloud layers. The scientists hope that continued observations with NIMS will help to explain a number of the following mysteries:
1) Although theories abound, it is still not known what gives rise to the bright colorations of the Jovian clouds - for example, the red pigment in the Great Red Spot or the various yellows and browns.
2) The nature of the circulation which gives rise to the east-west, belt-zone cloud structure is controversial.
3) What creates and sustains the various giant weather systems (of which the Great Red Spot is just one example of a whole family of different types of giant eddies).
The analysis of the data is still at a relatively early stage, but several preliminary results will be presented at NAM.
The ammonia clouds are overlain by a thick haze at much higher levels in Jupiter's atmosphere. This appears to be a photochemical smog made up of liquid hydrocarbon droplets. A similar layer blankets Saturn's moon Titan and prevents us from seeing Titan's surface. Although thinner than Titan's, the Jovian haze is unexpectedly substantial, and varies with time and place across the planet.
There is a thicker cloud layer below both the haze and the ammonia cloud. This may be the theoretically-predicted hydrogen sulphide (as NH4SH) cloud at around the one-and-a- half bar level (one and a half times the sea level air pressure on Earth), or a combination of that and an even deeper water cloud. New data is being acquired to try to resolve this point.
Galileo is a $1.5 billion NASA mission to explore the Jupiter system at close quarters over a long period. The orbiter has been returning data on the planet and its four largest moons since 7 December, 1995. A probe was also released into Jupiter's atmosphere which returned unique information on the structure and composition of the planets cloud layers. Although the primary mission is now over, the orbiter and the NIMS experiment are in good health and an extended mission is under way. This is focusing on detailed studies of the icy satellite Europa, which is thought to have a sub-surface ocean.