What Can an Image of a Black Hole Teach Us?

Researchers have rendered the first-ever image of a black hole. Learn how they did it and how it helps prove Einstein right in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of iHeart Radio. Hey, brain Stuff,
Lauren Vogel bomb Here. An event horizon is the point
of no return, a spherical region surrounding the gaping maw
of a black hole, beyond which nothing, not even light
can escape. We have no idea what mysteries lie inside,
but we do know that our universe ends abruptly at

(00:23):
this terrifying boundary into the unknown. Now, after two decades
of international collaboration, some of the world's most powerful radio
telescopes have captured an image of a supermassive black hole's
event horizon. By doing so, they proved that the predictions
arising from Einstein's theory of general relativity are valid even
in the most extreme cosmic environment possible. The black hole

(00:46):
in the image lurks in the center of the massive
elliptical galaxy Messier eighty seven, in the constellation Virgo, some
fifty five million light years distant. The release of the
image was highly anticipated all over the world and published
in several studies appearing in the journal Astro Physical Journal Letters.
Supermassive black holes dictate the evolution of the galaxies they inhabit,

(01:06):
so a direct look at this one's event horizon could
open a new window of understanding into how these behemoths work.
And this monstrous object is quite the specimen. It has
a whopping mass of six point five billion sons, all
crammed into an event horizon measuring nearly half a light
day across. Despite its incredible size and mass, no single

(01:26):
telescope on the planet could capture its portrait. It's simply
too far away to resolve. To remedy this, astronomers used
a method known as very long baseline interferometry to combine
the collective observing power of eight of the world's most
powerful radio telescopes to do the job. The event Horizon
Telescope is a virtual telescope as wide as our planet
and powerful enough to capture the first glimpse of one

(01:48):
of the most massive black holes known to exist. It
took a team of more than two hundred researchers to
accomplish this feat. Although black holes are well black, should
there be any matter close to the event horizon, extreme
friction in the relativistic environment will rip electrons from atoms,
creating a powerful fireworks display, and this is why the
event Horizon Telescope's first image shows a dark circle surrounded

(02:12):
by a bright ring of emissions. These emissions are being
produced just outside the black hole's event horizon, where the
extremely hot gases orbiting it are heated to several billions
of degrees kelvin, with the event horizon itself appearing as
a silhouetted dark disc against a bright background. Features that
confirm what theoretical physicists could only predict up until now.

(02:33):
Surely a dramatic moment for those theorists, this is possibly
the most profound outcome of the event horizon telescopes observation.
All of the theoretical predictions for what the event horizon
telescope might see are based on the framework of Einstein's
general relativity, a theory that has proven robust since its
formulation more than a hundred years ago. On seeing this

(02:54):
first image, physicists remarked on how precisely the reality of
the black hole's event horizon matches the actions of general relativity,
and this first image is just that the first. The
event horizon telescope collaboration will continue observing Messier eighty seven
and a second target, the supermassive black hole in the
center of our galaxy, A four million solar mass object

(03:15):
called Sagittarius A. Counterintuitively, although Sagittarius A is comparatively close
only twenty light years away two thousand times close to
us than Messi A eighty seven, it has a different
set of challenges. One problem is that as Sagittarius A
is smaller, its emissions vary over shorter time scales than
Messier eighty seven's monstrous black hole, making observations more difficult. Also,

(03:39):
as we are embedded inside our galaxy's disc, which contains
a lot of interstellar dust, the event horizon telescope signal
suffers more scattering, making it more challenging to resolve. As
most of the intergalactic space between us and Messier eighty
seven is pretty empty, scattering is less of a problem
when we'll see Sagittarius A. Remains to be seen, But

(04:00):
now that the technology behind the event horizon telescope has
been proven, our understanding of supermassive black holes is sure
to blossom. Today's episode was written by Ian O'Neill and
produced by Tyler Clang. Brain Stuff is a production of
iHeart Radio's How Stuff Works. For more on this and
lots of other supermassive topics, visit our home planet, how

(04:22):
stuff works dot com and for more podcasts. For my
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