WWW.ASTRONOMY.COM 25In 2011, physicists with the ALPHA
experiment at Europe’s CERN laboratory
were able to create and trap antihydrogen
— consisting of an antiproton and a posi-
tron — for 16 minutes, long enough to
study the material. And in December
2016, that same group announced it had
measured the glow of antihydrogen for the
first time.
Every chemical element — whether it’s
hydrogen, carbon, or copper — glows at
specific colors when energized. Each spe-
cific color corresponds to the amount of
energy that an electron needs to absorb to
jump to another energy level within an
atom. Conversely, if the electron is at one of
those higher energy levels and falls down,
it releases that same color of light. (For
example, the red color of hydrogen-alpha
radiation, commonly observed by astrono-
mers, corresponds to an electron in a
hydrogen atom moving between the third
and second energy levels.) Understanding
the colors each element glows at is crucial
to identifying the material and learning
about its physics. Scientists know every
color that a hydrogen atom gives off. Does
antihydrogen differ? And if it does, what
does it mean about the reason our universe
picked matter over antimatter?The ALPHA group is working on
detecting all the different colors at which
antihydrogen glows. In December 2016,
they announced they’ve observed one. The
light the atom emits when its positron
bounces between two specific energy levels
is the same as the light emitted from a reg-
ular hydrogen atom, meaning so far, matter
and antimatter appear to give off identical
colors. This agreement shows that antimat-
ter does indeed appear to be matter’s exact
but opposite twin, confirming predictions
made by the current Standard Model of
particle physics — and special relativity
— so far.On May 19, Juno
zipped past Jupiter.
The spacecraft’s
two-hour close
approach is captured
in this sequence of
14 color-enhanced
JunoCam images,
beginning with the
planet’s north pole
(left), then crossing
the equator (middle
images), and ending
with the south pole
(right). NASA/SWRI/MSSS/
GERALD EICHSTÄDT/SEÁN DORANJuno achieved
another first when
JunoCam snapped
the closest-ever
pictures of the
planet’s turbulent
Great Red Spot
from a distance of
6,130 miles (nearly
9,900 kilometers)
July 10. NASA/SWRI/MSSS/
GERALD EICHSTÄDT/SEÁN DORAN