Sky and Telescope - November 2017 - 53

2016 Nov. 1-3 (Pic du Midi)
J.-L. Dauvergne & F. Colas

2016 Dec. 9
Christopher Go

2017 Jan. 10
Phil Miles

2017 Feb. 19
Damian Peach

2017 Apr. 9
Clyde Foster

2017 May 30
Christopher Go
+60°
+40°

NNTB
NTB(N)
NTB(S)
NTrZ
NEB

+20°
0°

EZ
SEB

-20°
STrZ
SSTB

-40°
-60°
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IM AG E SEQ UENCE: M A RCO V EDOVATO & JOHN ROG ERS;
JUNO IM AG E: N ASA / SWRI / MSSS / G ER A LD EICHSTÄ DT / JOHN ROG ERS

p These reprojected images show changes in Jupiter's main belts and zones that occurred from November 2016 to May 2017. Initially, the North
Temperate Belt (NTB) is in the throes of a violent outbreak of turbulence; from December onward, the belt "revives" with an orange southern component and dark gray northern component. Meanwhile, outbreaks of white "rifts" tear through the North Equatorial Belt (NEB) from January onward. The
South Equatorial Belt (SEB) exhibits a new, bright rift in January's view and especially in May's.

NTB(S). These outbreaks sometimes
occur at 5-year intervals, as they did in
in 2007 and again in 2012.
This past year, given that the belt had
faded again and the jet stream accelerated, observers anticipated another
outbreak in late 2016 or early 2017. And
it did occur - but when Jupiter was hidden from Earth during solar conjunction in late September. Glenn Orton
(Jet Propulsion Laboratory) discovered
the outburst in infrared images taken
from Hawai'i on October 19, 2016, during Juno's second perijove. Although the
spacecraft made no observations at that
time, we could still identify and track
the outbreak's four plumes in distant,
low-resolution JunoCam images taken
through October 14th.
Several amateurs immediately
started imaging as well and successfully
tracked the progress of the outbreak.
Over the subsequent months, the
orange NTB(S) appeared as expected -
it's known as the "Big Red Stripe" on
JunoCam's public website (missionjuno.
swri.edu/junocam) - and the camera's
dramatic images taken at successive
perijoves showed the detailed cloud textures as the reviving belt matured.
Cycles of activity in the North
Equatorial Belt are quite different.
They're marked by rapid broadening of
the dark belt to the north, accompanied
by outbreaks of convective white clouds
known as "rifts." This sequence tends to

occur at intervals of 3 to 5 years - the
latest began in 2015 but ﬁ zzled out in
early 2016, when it extended only halfway round the planet.
However, late last year, as the intense
turbulence of the NTB outbreak spread
southward, new rifts began to appear in
the NEB. As seen in the sequence above,
these proliferated to a remarkable
extent and, in 2017, induced a full-scale
broadening of the belt to the north.
These cyclic changes typically cause
new features to develop in the expanded
belt, and in fact we've observed both
cyclonic brown ovals and anticyclonic
white ovals. JunoCam has taken closeups of the belt throughout all this activity, including recent snapshots of two of
the newly formed vortices.

NTB(N)

NTB(S)

Making Waves
During these recent disturbances in the
NEB, amateur observers have noted a
series of large diffuse waves in the haze
over the belt, which become visible in
images recorded at near-infrared wavelengths sensitive to absorption by methane. Only once before, in 2000, have
u In this close-up of Jupiter as seen by NASA's
Juno spacecraft near perijove, the cloud
features are distorted by the extreme wideangle view. The NTB has a dual personality: a
turbulent northern half, designated NTB(N), and
a calmer but strongly colored southern half,
NTB(S). The very bright rift in NTB(N) is studded with tiny bright clouds casting shadows.

NTrZ

Vortex

NEB

s k y a n d t e l e s c o p e . c o m * N O V E M B E R 2 0 17

http://www.missionjuno.swri.edu/junocam http://www.missionjuno.swri.edu/junocam http://www.skyandtelescope.com

Sky and Telescope - November 2017

Table of Contents for the Digital Edition of Sky and Telescope - November 2017