WEBVTT - What Can an Image of a Black Hole Teach Us?

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<v Speaker 1>Welcome to brain Stuff production of iHeart Radio. Hey, brain Stuff,

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<v Speaker 1>Lauren Vogel bomb Here. An event horizon is the point

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<v Speaker 1>of no return, a spherical region surrounding the gaping maw

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<v Speaker 1>of a black hole, beyond which nothing, not even light

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<v Speaker 1>can escape. We have no idea what mysteries lie inside,

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<v Speaker 1>but we do know that our universe ends abruptly at

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<v Speaker 1>this terrifying boundary into the unknown. Now, after two decades

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<v Speaker 1>of international collaboration, some of the world's most powerful radio

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<v Speaker 1>telescopes have captured an image of a supermassive black hole's

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<v Speaker 1>event horizon. By doing so, they proved that the predictions

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<v Speaker 1>arising from Einstein's theory of general relativity are valid even

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<v Speaker 1>in the most extreme cosmic environment possible. The black hole

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<v Speaker 1>in the image lurks in the center of the massive

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<v Speaker 1>elliptical galaxy Messier eighty seven, in the constellation Virgo, some

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<v Speaker 1>fifty five million light years distant. The release of the

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<v Speaker 1>image was highly anticipated all over the world and published

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<v Speaker 1>in several studies appearing in the journal Astro Physical Journal Letters.

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<v Speaker 1>Supermassive black holes dictate the evolution of the galaxies they inhabit,

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<v Speaker 1>so a direct look at this one's event horizon could

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<v Speaker 1>open a new window of understanding into how these behemoths work.

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<v Speaker 1>And this monstrous object is quite the specimen. It has

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<v Speaker 1>a whopping mass of six point five billion sons, all

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<v Speaker 1>crammed into an event horizon measuring nearly half a light

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<v Speaker 1>day across. Despite its incredible size and mass, no single

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<v Speaker 1>telescope on the planet could capture its portrait. It's simply

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<v Speaker 1>too far away to resolve. To remedy this, astronomers used

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<v Speaker 1>a method known as very long baseline interferometry to combine

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<v Speaker 1>the collective observing power of eight of the world's most

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<v Speaker 1>powerful radio telescopes to do the job. The event Horizon

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<v Speaker 1>Telescope is a virtual telescope as wide as our planet

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<v Speaker 1>and powerful enough to capture the first glimpse of one

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<v Speaker 1>of the most massive black holes known to exist. It

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<v Speaker 1>took a team of more than two hundred researchers to

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<v Speaker 1>accomplish this feat. Although black holes are well black, should

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<v Speaker 1>there be any matter close to the event horizon, extreme

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<v Speaker 1>friction in the relativistic environment will rip electrons from atoms,

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<v Speaker 1>creating a powerful fireworks display, and this is why the

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<v Speaker 1>event Horizon Telescope's first image shows a dark circle surrounded

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<v Speaker 1>by a bright ring of emissions. These emissions are being

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<v Speaker 1>produced just outside the black hole's event horizon, where the

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<v Speaker 1>extremely hot gases orbiting it are heated to several billions

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<v Speaker 1>of degrees kelvin, with the event horizon itself appearing as

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<v Speaker 1>a silhouetted dark disc against a bright background. Features that

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<v Speaker 1>confirm what theoretical physicists could only predict up until now.

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<v Speaker 1>Surely a dramatic moment for those theorists, this is possibly

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<v Speaker 1>the most profound outcome of the event horizon telescopes observation.

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<v Speaker 1>All of the theoretical predictions for what the event horizon

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<v Speaker 1>telescope might see are based on the framework of Einstein's

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<v Speaker 1>general relativity, a theory that has proven robust since its

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<v Speaker 1>formulation more than a hundred years ago. On seeing this

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<v Speaker 1>first image, physicists remarked on how precisely the reality of

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<v Speaker 1>the black hole's event horizon matches the actions of general relativity,

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<v Speaker 1>and this first image is just that the first. The

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<v Speaker 1>event horizon telescope collaboration will continue observing Messier eighty seven

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<v Speaker 1>and a second target, the supermassive black hole in the

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<v Speaker 1>center of our galaxy, A four million solar mass object

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<v Speaker 1>called Sagittarius A. Counterintuitively, although Sagittarius A is comparatively close

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<v Speaker 1>only twenty light years away two thousand times close to

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<v Speaker 1>us than Messi A eighty seven, it has a different

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<v Speaker 1>set of challenges. One problem is that as Sagittarius A

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<v Speaker 1>is smaller, its emissions vary over shorter time scales than

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<v Speaker 1>Messier eighty seven's monstrous black hole, making observations more difficult. Also,

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<v Speaker 1>as we are embedded inside our galaxy's disc, which contains

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<v Speaker 1>a lot of interstellar dust, the event horizon telescope signal

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<v Speaker 1>suffers more scattering, making it more challenging to resolve. As

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<v Speaker 1>most of the intergalactic space between us and Messier eighty

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<v Speaker 1>seven is pretty empty, scattering is less of a problem

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<v Speaker 1>when we'll see Sagittarius A. Remains to be seen, But

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<v Speaker 1>now that the technology behind the event horizon telescope has

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<v Speaker 1>been proven, our understanding of supermassive black holes is sure

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<v Speaker 1>to blossom. Today's episode was written by Ian O'Neill and

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<v Speaker 1>produced by Tyler Clang. Brain Stuff is a production of

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<v Speaker 1>iHeart Radio's How Stuff Works. For more on this and

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<v Speaker 1>lots of other supermassive topics, visit our home planet, how

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<v Speaker 1>stuff works dot com and for more podcasts. For my

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