by Neel V. Patel / illustration by Alessandro Rustighisupermassive black hole. The
behemoth in question sits 55 mil-
lion light-years away in the M 87
galaxy in the constellation Virgo.
This big reveal could help answer
some of our heftiest questions
about the universe.
Astrophysicists coined the
term “black hole” in 1967, and
there’s a reason the elusive beasts
have fascinated us for the decades
since. Each has a colossally dense
center—the one inside M87 is
6.5 billion times the sun’s mass.
That creates immense gravita-
tional pull, sucking up practically
everything nearby. Around the
center, though, is a visible point
of no return called the event hori-
zon, where gas and debris create a
glowing silhouette. One problem:
In the vastness of the universe,
black holes are tiny (their density
is akin to squeezing a star larger
than the sun into New York City).
Making out M87’s signature is
similar to spotting a quarter on the
moon from your backyard.
The EHT is up to the task be-
cause it’s not actually a telescope.
It’s eight of them. The interna-
tional network of ground- basedstarin
g
intoa (^) cosm
ic
abyss
radio instruments utilizes a technique called
Very Long Baseline Interferometry, in which
an army of atomic clocks synchronizes the ar-
ray to observe a shared target. Combined, the
individual devices become a single scope—
the EHT. They pick up waves emitted by the
event horizon, and large computers convert
the signals into data that visually represents
the object, which humans then clean up and
piece together into an image.
Over four days in April 2017, the EHT
aimed its contingent toward M87 and peered
at the galaxy’s supermassive black hole,
capturing these signals with unprecedented
sensitivity. More than 200 scientists around
the world spent two years translating the
data into a luminescent-orange snapshot. (It
looks like a blurry, misshapen doughnut, so
we made our own version above.) “We hit the
daily double—we had everything work out
perfectly for us,” Doeleman says.
There’s no environment in the universe like
a black hole. Being able to see such an object
gives us a “natural laboratory,” Doeleman
says. We can test long-standing theories
about how objects move through space—like
Einstein’s general relativity—by watching
gravity-driven warps in spacetime impact
how light travels. We can also study how
black holes help shape the universe by suck-
ing up matter. In Doeleman’s words, “Nature
is providing us with a sandbox.”
IT’S HARD TO SNEAK A PEEK OF A BLACK HOLE.
Not even light—the fastest known thing
in the universe—can escape its gargan-
tuan gravitational pull. “You’ve got
something that is just designed not to
give up its secrets,” says Shep Doele-
man, senior research fellow at Harvard
University and director of the Event
Horizon Telescope (EHT) at the Harvard-
Smithsonian Center for Astrophysics.
In April 2019, Doeleman and his colleagues spilled
the beans, revealing to the world the first image of a
DEEPER
CUT
EVENT HORIZON
Black holes don’t pose a risk unless you get
up in their business, but each has a point
of no return. Whatever makes it past this
perimeter is toast, even if it’s moving as fast
as light—which no matter can manage.
PHOTON SPHERE
Just outside the gate to oblivion sits a
glowing border town. Falling matter emits
photons that are just speedy enough to
whoosh into orbit instead of continuing to
the event horizon around the giant.
ACCRETION DISK
Gas and dust from unlucky celestial
bodies form a spiraling pancake as they’re
drawn in. The black hole’s gravity keeps this
material flying so fast that it sends out
glowing radiation due to constant collisions.
SINGULARITY
It’s like a heart—or a stomach. Gravity
pulls all available matter into the exact
center of the black hole. This spot is so tiny
and so packed with ever-more matter
that its density is seemingly infinite.
POPSCI.COM•FALL 2019 13
The Inside Scoop