January/February 2019^ DISCOVER^49
FROM TOP: SVEN LIDSTROM/ICECUBE/NSF; JAMIE YANG/ICECUBE; DESY SCIENCE COMMUNICATION LAB
likelihood is that the black hole
spewed out both the gamma rays
and massive amounts of neutrinos,
including the one IceCube caught.
It’s the irst time scientists have
identiied the origins of a high-
energy neutrino, and, in another
irst, learned that black holes can
create them — though
they still don’t know
exactly how.
“The ield of neutrino
astronomy has become
a reality. For decades
it has been a dream
of many to harness
high-energy neutrinos
as one of nature’s
ideal astronomical
messengers,” says
University of Alberta
astroparticle physicist Darren
Grant, study co-author andIceCube spokesman. “This
detection has opened for us a
new window with which to view
the universe, much the same as
the discovery of gravitational
waves did recently” at the Laser
Interferometer Gravitational-wave
Observatory (LIGO).
And with the upgrade
known as IceCube-Gen2
hopefully coming online
in the next few years,
along with an upgraded
LIGO in 2019, scientists
are excited for a combined
measurement of neutrinos,
gravity waves and light.
“Bringing all of the
information from these
messengers together,
each contributing unique
elements, holds enormous potential
for what we may learn,” says Grant.Staring Down the Barrel of a Black Hole
So, what is a blazar, anyway?
At the center of most galaxies — including our own Milky
Way — lie gargantuan black holes millions or even billions
of times as massive as our sun. In some galaxies, a swirling
disk of trapped gas, dust and stellar debris collects around
these supermassive black holes.
While you probably
imagine a black hole as a
dark vacuum in space, when
material in the disk falls
toward the black hole, it
produces energy that can
turn into light, making the
centers of these galaxies
actually very bright. Some of
these bright spots also eject
colossal jets of particles that
travel close to the speed of
light. Scientists often refer
to these black holes, jets and
all, as quasars.
But when such a galaxy
happens to be oriented
so one of the jets points
toward Earth — so we’re
basically staring it in theface — it’s called a blazar. It’s the same thing as a quasar,
just pointed at a different angle. Those jets can produce
high-energy neutrinos like the one detected by IceCube.
The word blazar, by the way, is a mashup of a term
derived from the first known example (BL Lacertae) and
quasar. — ERIKA K. CARLSONThe IceCube facility (top) in Antarctica
found a ghostly neutrino particle last
summer, thanks to detectors spread within
a cubic kilometer of ice (above).