Sky and Telescope - March 2016 - 21

NTrZ

February 2012

NTB
NEB

EZ
GRS

SEB
STrZ
STB

"Red Spot Jr."

First, the storm has gotten smaller not just in its longitudinal width but also in its north-south extent. In addition, it occasionally moves slightly northward or southward, affecting which wind jet it deflects more. HST's
2014 measurements show the spot located near its normal
central latitude (22°° south), but both its north and south
edges contracted centerward as the entire system shrunk.
The westward jet still experiences significant deflection around the GRS's northern edge, though perhaps
slightly less than previously. However, the eastward jet is
now barely deflected southward by the GRS. This means
that any entrained eddies in this region are not interacting closely enough to be caught in the spot's flow.
We now strongly suspect that these jet interactions are
affecting not only the color but also possibly the size of
the Great Red Spot. In time, our computer modeling of
the GRS's interaction with the nearby wind jets should
help us understand the energy exchange between them.

The Future
So what does the future hold for the most famous storm
in the solar system? That's difficult to predict, as sudden
outbreaks could always alter the energy balance and
wind flow near and within the GRS and change our view
completely. Atmospheric specialists describe the shape
of Jupiter's anticyclonic storms (high-pressure systems
like the GRS) by the ratio of their length to width, and
it's not unusual for this key aspect ratio to decrease in
such storms, particularly right after they form.
For example, the white ovals just south of the GRS
first appeared in the late 1930s not as discrete spots but
rather as high-altitude clouds and haze that suddenly
inundated their latitude band, probably related to a large
convective event. The brightened zone then coalesced
into three distinct, oblong white storms, which observers designated BC, DE, and FA. By the Voyager flybys in
1979, each had an aspect ratio of about 2. They continued

ALTERED BY
UPHEAVAL
Compare how Jupiter looked in 2010
(left) - with its dark
South Equatorial Belt
"missing" and its
GRS intensely colored
- with the view two
years later, after the
high-altitude clouds
obscuring the SEB had
dissipated and the GRS
had become paler.

DAMIAN PEACH

September 2010

to shrink until merging into a single oval in 2000, with
the new, combined oval BA having an aspect ratio of
1.25. In 2005, it turned red - earning the moniker "Red
Spot Jr." - and by 2015 its aspect ratio was 1.3. Meanwhile, the GRS's aspect ratio has changed from about 3
during the Voyager flybys in 1979 to the 1.4 it has now.
Computer models suggest that Jupiter's anticyclonic
vortices should exhibit preferred aspect ratios, but those
depend somewhat on interactions with adjacent wind
jets, especially for a large storm that can deflect the jets.
So the GRS might eventually reach a shape that is "just
right," allowing it to stabilize.
Studies of its internal dynamics will help us to model
its fate, so we continue to make yearly Hubble observations. And amateurs' observations are critical for
monitoring the GRS. Their regular reports help us to fill
in the gaps between studies with HST and professional
telescopes. They can also alert us to new happenings
that require rapid follow-up.
All things considered, we expect that the Great Red
Spot will continue to shrink for some time to come. We
don't expect it to disappear completely - but for now
what happens in the years ahead is anyone's guess. ✦
Amy Simon, an atmospheric dynamicist at NASA's Goddard Space Flight Center, leads the observing team for HST's
Outer Planet Atmospheres Legacy monitoring program.

G E T T O KN OW J U PITE R
For more information about the study of Jupiter's cloud
features and the Great Red Spot in particular, see The
Giant Planet Jupiter (Cambridge University Press, 1995),
authored by John Rogers of the British Astronomical Association. Also see page 48 for a general guide to observing
Jupiter and page 50 for a list of times when the GRS is
positioned best for telecopic viewing.

Sk yandTelescope.com March 2016

21


http://www.SkyandTelescope.com

Sky and Telescope - March 2016

Table of Contents for the Digital Edition of Sky and Telescope - March 2016

Contents
Sky and Telescope - March 2016 - Cover1
Sky and Telescope - March 2016 - Cover2
Sky and Telescope - March 2016 - 1
Sky and Telescope - March 2016 - Contents
Sky and Telescope - March 2016 - 3
Sky and Telescope - March 2016 - A
Sky and Telescope - March 2016 - B
Sky and Telescope - March 2016 - 4
Sky and Telescope - March 2016 - 5
Sky and Telescope - March 2016 - 6
Sky and Telescope - March 2016 - 7
Sky and Telescope - March 2016 - 8
Sky and Telescope - March 2016 - 9
Sky and Telescope - March 2016 - 10
Sky and Telescope - March 2016 - 11
Sky and Telescope - March 2016 - 12
Sky and Telescope - March 2016 - 13
Sky and Telescope - March 2016 - 14
Sky and Telescope - March 2016 - 15
Sky and Telescope - March 2016 - 16
Sky and Telescope - March 2016 - 17
Sky and Telescope - March 2016 - 18
Sky and Telescope - March 2016 - 19
Sky and Telescope - March 2016 - 20
Sky and Telescope - March 2016 - 21
Sky and Telescope - March 2016 - 22
Sky and Telescope - March 2016 - 23
Sky and Telescope - March 2016 - 24
Sky and Telescope - March 2016 - 25
Sky and Telescope - March 2016 - 26
Sky and Telescope - March 2016 - 27
Sky and Telescope - March 2016 - 28
Sky and Telescope - March 2016 - 29
Sky and Telescope - March 2016 - 30
Sky and Telescope - March 2016 - 31
Sky and Telescope - March 2016 - 32
Sky and Telescope - March 2016 - 33
Sky and Telescope - March 2016 - 34
Sky and Telescope - March 2016 - 35
Sky and Telescope - March 2016 - 36
Sky and Telescope - March 2016 - 37
Sky and Telescope - March 2016 - 38
Sky and Telescope - March 2016 - 39
Sky and Telescope - March 2016 - 40
Sky and Telescope - March 2016 - 41
Sky and Telescope - March 2016 - 42
Sky and Telescope - March 2016 - 43
Sky and Telescope - March 2016 - 44
Sky and Telescope - March 2016 - 45
Sky and Telescope - March 2016 - 46
Sky and Telescope - March 2016 - 47
Sky and Telescope - March 2016 - 48
Sky and Telescope - March 2016 - 49
Sky and Telescope - March 2016 - 50
Sky and Telescope - March 2016 - 51
Sky and Telescope - March 2016 - 52
Sky and Telescope - March 2016 - 53
Sky and Telescope - March 2016 - 54
Sky and Telescope - March 2016 - 55
Sky and Telescope - March 2016 - 56
Sky and Telescope - March 2016 - 57
Sky and Telescope - March 2016 - 58
Sky and Telescope - March 2016 - 59
Sky and Telescope - March 2016 - 60
Sky and Telescope - March 2016 - 61
Sky and Telescope - March 2016 - 62
Sky and Telescope - March 2016 - 63
Sky and Telescope - March 2016 - 64
Sky and Telescope - March 2016 - 65
Sky and Telescope - March 2016 - 66
Sky and Telescope - March 2016 - 67
Sky and Telescope - March 2016 - 68
Sky and Telescope - March 2016 - 69
Sky and Telescope - March 2016 - 70
Sky and Telescope - March 2016 - 71
Sky and Telescope - March 2016 - 72
Sky and Telescope - March 2016 - 73
Sky and Telescope - March 2016 - 74
Sky and Telescope - March 2016 - 75
Sky and Telescope - March 2016 - 76
Sky and Telescope - March 2016 - 77
Sky and Telescope - March 2016 - 78
Sky and Telescope - March 2016 - 79
Sky and Telescope - March 2016 - 80
Sky and Telescope - March 2016 - 81
Sky and Telescope - March 2016 - 82
Sky and Telescope - March 2016 - 83
Sky and Telescope - March 2016 - 84
Sky and Telescope - March 2016 - Cover3
Sky and Telescope - March 2016 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/newtrack/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com