Sky and Telescope - January 2017 - 16

NEWS NOTES
MISSIONS

NASA's Juno Makes
First Science Pass
ON AUGUST 27TH, Juno made the

first of its 36 planned flybys of Jupiter,
zooming through perijove just 4,200
km (2,600 miles) above the cloudtops.
For comparison, geostationary satellites
orbit almost nine times farther than
that from Earth. No other spacecraft
has come so close to the gas giant,
except to plunge into its atmosphere.
Juno will probe Jupiter's composition
and measure its magnetic and gravitational fields (S&T: July 2016, p. 18).
To carry out its mission, the craft must
thread the intense radiation belts surrounding the planet on successive polar
passes. All instruments came through
this first pass unscathed, though Juno is
t A composite image of Jupiter's north pole,
assembled from JunoCam images by S&T
Equipment Editor Sean Walker.

expected to suffer from some radiation
degradation on each consecutive flyby.
The stunning, visible-light images
from JunoCam (used to make the
composite at left) provide scientists'
first glimpse of Jupiter's north pole,
which "looks like nothing we have seen
or imagined," says principal investigator Scott Bolton (Southwest Research
Institute, San Antonio). The poles
are dappled with swirling storms and
depressions, and unlike at Saturn,
there's no polar hexagon.
Juno has also given researchers the
first-ever view of Jupiter's southern aurorae. The observations, made at 3.3 to 3.6
microns, reveal a flurry of hydrogen ions
energized by charged particles cascading in from the planet's magnetosphere.
In addition, the craft made the closest
recordings of Jupiter's radio outbursts.
■ DAVID DICKINSON
See more images from the flyby at
https://is.gd/junofirstpass.

MILKY WAY

AN INTERGALACTIC CLOUD has
slammed into the Milky Way Galaxy
and left a big hole in its gas.
Galaxies like ours are full of gas, but
it's clumpy and cavity-ridden. Among
the largest cavities are supershells. These
structures are huge bubbles in a galaxy's
gas, easily 2,000 light-years wide. It
takes a whole lot of energy to inflate
that kind of bubble: the equivalent of at
least 30 supernovae, planted like little
vicious bombs at the cavity's center.
Yet oddly, most of the supershells we
know of don't have aging star clusters
at their centers. Instead, astronomers
suspect that some of them were created by high-velocity clouds (HVC). These
clouds shower the Milky Way from space
in a steady drizzle, helping to fuel star
formation. If such a cloud rammed into
a galaxy, it could blast out a big bubble.
Geumsook Park (Seoul National
University, South Korea) and colleagues

16

J A N U A R Y 2 0 1 7 * SK Y & TELESCOPE

have now found the first solid example
of an HVC doing just that. As part of the
I-GALFA survey with the Arecibo radio
telescope, the team discovered a supershell surrounding a compact cloud called
HVC 040+01-282. The shell is a whopping 3,000 light-years wide, with spokelike structures inside it. Smack-dab in its
center sits HVC 040+01-282. The team
estimates in the August 20th Astrophysical Journal Letters that, if the cloud collided with its maximum possible velocity,
it would have had more than enough
energy to blow out the supershell.
■ CAMILLE M. CARLISLE

IN BRIEF
Solar Flare Momentarily
Heated Cold War
A May 1967 solar flare was nearly
responsible for conflict breaking out
between the United States and the
Soviet Union. On May 23rd that year, all
three American ballistic missile earlywarning radars were simultaneously
jammed. The Air Force, believing the
Soviet Union was to blame, authorized
aircraft with nuclear-strike capabilities
to take to the skies. But space-weather
forecasters realized the culprit was
a powerful solar flare and convinced
decision-makers to forego military
action. Delores Knipp (University of
Colorado, Boulder) collaborated with
retired U.S. Air Force officers involved
in forecasting and analyzing the storm
to bring this story to light. The study
appears September 5th in the journal
Space Weather.
■ CHRIS STUBENRAUCH

Supershell around HVC 040+01-282

Read more at https:/is.gd/1967flare.

MISSIONS: N ASA / JPL / SWRI / MSSS / S. WA LK ER; MILK Y WAY: G EU MSOOK
PA RK A ND BON- CHUL KOO / SEOUL N ATION A L UNIV ERSIT Y

Cloud Punches Hole
in Our Galaxy


https://www.is.gd/junofirstpass http://https:/is.gd/1967/flare

Sky and Telescope - January 2017

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