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00:0026,000 light-years from Earth, shrouded in cosmic dust and gas, is a mysterious region
00:11of space, the center of the Milky Way.
00:17The center of the Milky Way galaxy is one of the strangest, most exotic, and violent
00:25places in our galaxy.
00:30Gas streaming everywhere, radiation blasting out, stars moving willy-nilly.
00:34And at the very heart is the mysterious black hole, four million times the mass of the sun.
00:44Now we're exploring the center of the Milky Way like never before, uncovering powerful
00:51forces that affect us all.
00:56Everything that happens at the center of the Milky Way galaxy really is connected to what's
00:59going on in the rest of the Milky Way.
01:02Understanding the center of our galaxy unlocks secrets of our past, present, and future.
01:21March, 2019.
01:31We focus the XMM-Newton Space Telescope on a region of space around Sagittarius A star,
01:40the supermassive black hole at the heart of our galaxy.
01:47We spot two huge columns of gas glowing in X-ray light.
01:59The columns seem to be coming from Sagittarius A star.
02:06We see giant fountains of gas extending outward from the central region, as though it's like
02:12a wind or a giant expulsion event.
02:17The fountains of gas extend 500 light years above and below the supermassive black hole.
02:27That's over a million times the distance from the sun to Neptune.
02:33It looks like this material is actually leaving the vicinity of the black hole, like it's
02:39burping out these giant hot X-ray chimneys.
02:44So why is Sagittarius A star burping out hot gas?
02:50Typically around a black hole, you have an accretion disk funneling material into the
02:54black hole, but all of it doesn't end up in the black hole.
02:59There is a little bit of gas falling onto it right now, even as I'm speaking, right?
03:05As gas falls toward the supermassive black hole, it becomes superheated, it liberates
03:10an enormous amount of energy, and that energy has to go somewhere.
03:16As gas spirals towards the black hole, some of the material accelerates to near the speed
03:23of light.
03:25It blasts out from the accretion disk, creating chimneys of superheated gas that seem to connect
03:35to two of the largest structures in the galaxy, the Milky Way's Fermi bubbles.
03:42A few years ago, we noticed that in fact there are these giant bubbles coming out of the
03:47very heart of the Milky Way galaxy.
03:49In each direction, there's a bubble 25,000 light years long.
03:55But the gas-filled bubbles dwarf the chimneys.
04:01Scientists wonder if another more powerful force blew the bubbles.
04:06So what could have created all of this superheated gas that actually blew these tremendously
04:10large bubbles?
04:13Black holes in other galaxies might offer clues.
04:18Black holes at the centers of galaxies go through different phases, so they can be either
04:22active or they can be calm.
04:26These black holes at the centers of galaxies go through an active phase.
04:30And when that happens, the black hole is actively feeding on material around it, which means
04:35it's growing, and it also gives off huge jets of radiation.
04:43Calm supermassive black holes release a trickle of hot gas.
04:51And when lots of material falls on them, they can shoot out jets up to millions of
04:57light years long.
05:04At the current time, Sagittarius A star is what we call quiescent.
05:08It's quiet.
05:09There is some material swirling around it, but really not very much.
05:14But we don't think that's always been the case.
05:19The centers of galaxies are busy places.
05:21There are stars there, there's gas there, there's dust there, and sometimes these things
05:27fall into that black hole.
05:32Six million years ago, Sagittarius A star may have had a feeding frenzy, feeding too
05:40much and blasting out the remains in huge jets.
05:49Those jets plow through the galaxy initially at near the speed of light, and as they do
05:56so they can wreak havoc or sculpt the evolution of the galaxy that they're propagating through.
06:04Sagittarius A star's jets blasted gas out of the galaxy, creating the scars we see as
06:12the Fermi bubbles.
06:14Now whatever caused those jets seems to have turned off.
06:17It's not happening anymore, and we're seeing sort of the leftovers of them.
06:23But this is clearly a sign that sometime in the past few million years, the black hole
06:27in the center of our galaxy, Sagittarius A star, was actively feeding on material around
06:32it.
06:35Material was falling into it and blasting out this stuff.
06:41The jets left destruction in their wake.
06:49They may also have affected the growth of our entire galaxy.
06:55These structures at the center of our galaxy are important because they can either shut
06:59off star formation or they can trigger star formation.
07:06As those jets propagate through the galaxy, they pile up gas, and that gas can be then
07:11triggered into star formation.
07:16But these jets can also impart so much heat or energy feedback into the environment that
07:21they prevent star formation.
07:27So black holes in many ways conduct an orchestra, instructing or dictating when stars can and
07:33cannot form.
07:43In the center of the Milky Way, star formation rates seem low.
07:48The jets could be responsible.
07:54But in 2017, the ALMA telescope discovered that change is coming.
08:02So ALMA's actually been able to peer into the heart of our galaxy and see that near
08:07all this destruction, there might actually be a new generation of stars forming.
08:15Today, our calm supermassive black hole could be helping star formation in the core.
08:25But the Fermi bubbles could be evidence of the time when Sagittarius A star shut down
08:31star formation.
08:33Could the supermassive black hole roar back to life in the future?
08:39Sag A star could roar back to life by just dumping some gas onto it.
08:44And there's a lot of gas at the center of our galaxy, and it could wander into the proximity
08:48of Sagittarius A star and ultimately fall onto the event horizon.
08:52And that would light it up.
08:58If Sagittarius A star eats enough gas, it could shut down star formation in the galaxy
09:07for millions of years.
09:14It could also give off x-rays and gamma rays that may hit the Earth.
09:22Thankfully, our central supermassive black hole is pretty quiet and massive feeding events,
09:30massive energy events are very, very rare.
09:35We don't necessarily have much to worry about.
09:41Sagittarius A star has reshaped our galaxy.
09:48If we want to survive in the universe, we need to know more about this monster black
09:53hole.
09:56The event horizon telescope is on a mission to do just that.
10:01The question is, will it succeed?
10:12The center of the Milky Way is home to a supermassive black hole, Sagittarius A star.
10:20At least, we think it is.
10:24We've never seen the supermassive black hole directly, but we have seen stars racing around
10:31the core.
10:33The speeds of the stars zipping around the center of our Milky Way galaxy indicate that
10:39there's something very massive and very compact there.
10:43Indeed, four million times as massive as our sun in a volume smaller than that of our solar
10:50system.
10:51It's got to be a black hole, basically.
10:56By measuring the orbits of stars in our galaxy's center, we estimate that Sagittarius A star
11:04is over 100 times wider than our sun.
11:12But despite its size, the black hole is hidden.
11:17One of the immediate challenges of actually observing black holes is the fact that they
11:21don't emit light, and so you can't see them.
11:25So we've never actually seen a black hole, we've only seen the stuff around a black hole.
11:29We have seen the effects that that black hole imparts on its ambient surroundings.
11:36That's where the Event Horizon Telescope came in.
11:40Its goal was to photograph Sagittarius A star.
11:45Not the black hole itself, but its shadow.
11:51Around it is this gas that is moving around the black hole that's superheated to millions
11:55of degrees, and what the Event Horizon Telescope is trying to see is the shadow of a black
11:59hole.
12:02Light from the hot gas around Sagittarius A star frames the giant shadow.
12:08It could be up to 93 million miles across.
12:13Problem is, Sagittarius A star is so far away, the supermassive black hole is still incredibly
12:20hard to see.
12:23Sagittarius A star is big, but it's 26,000 light years away.
12:27You know, a single light year is 6 trillion miles.
12:30So this is a long, long walk, and even though it's big, that distance shrinks its apparent
12:36size to just a tiny little dot on the sky.
12:41To see the tiny dot, we need a telescope the size of the Earth.
12:47How do you possibly do that?
12:48You can't build that telescope, right?
12:51Well, there's a trick.
12:53You actually get a few different telescopes, and you spread them out over the surface of
12:57the Earth.
13:03And when we add all of these sites together, we wind up being able to take an image of
13:09something that is really, really impossibly small.
13:14To gather enough light to see this small target, the team takes long exposure images
13:20of Sagittarius A star's shadow.
13:27But there's a problem.
13:30The accretion disk moves too much for us to capture a clear image of Sagittarius A star's
13:36shadow.
13:37When you're taking a long exposure of a person, right, you need them to be really, really
13:42still, right?
13:43Because if they're moving around a lot, they're going to blur the image out.
13:47And that kind of thing is happening when we observe Sagittarius A star, because it is
13:51unwilling to sit still for us.
13:53It is booming and banging and flashing on the time scale of literally hours.
13:59As glowing material orbits the black hole at 30% the speed of light, Sagittarius A star's
14:05shadow blurs.
14:09Future developments may allow us to see Sagittarius A star clearly.
14:17For now, we can't capture an accurate image of our galaxy's supermassive black hole.
14:26But the hunt to see a supermassive black hole wasn't over.
14:30The Event Horizon Telescope turned to another galaxy 54 million light years away, M87.
14:39M87 is an absolute beast of a galaxy.
14:43It's a so-called brightest cluster galaxy.
14:46These are among the largest galaxies in the universe.
14:51And M87 is home to another supermassive black hole, the giant M87 star.
15:00M87 star is so massive that the gravitational region that's interesting is actually easier
15:07to image than the black hole in our own galaxy.
15:12M87 star is over a thousand times more massive than Sagittarius A star and has a far larger
15:21accretion disk.
15:24When photographing a black hole, size matters because big accretion disks project more stable
15:31light so images of them don't blur as much.
15:38In April 2019, the Event Horizon team unveiled their image.
15:44We have seen what we thought was unseeable.
15:48We have seen and taken a picture of a black hole.
16:00I've been working on this project for almost six years now and so this is something we've
16:05been looking forward to for a really long time.
16:09Capturing this image took decades of work by hundreds of scientists from all over the
16:15world.
16:19I was really stunned.
16:21Suddenly when you say that's the real thing, that's amazing.
16:25It really affected me.
16:27This is something six and a half billion times the mass of the sun, 55 million light years
16:34away, and we're looking at it?
16:37So when you look at the image, it's totally fine.
16:40You're totally forgiven for thinking, eh, it looks a little blurry.
16:44But I cannot reiterate enough how profound this image actually is.
16:51We are seeing just a hair's width away from a discontinuity in the fabric of spacetime
16:56itself.
16:57Actually seeing so close to an actual Event Horizon, a discontinuity in the fabric of
17:02spacetime never seemed possible.
17:07This image of the heart of a distant galaxy helps us understand supermassive black holes
17:13like never before.
17:17When we observe supermassive black holes in other galaxies, including the one in M87,
17:22we're able to learn more about the big picture of how these massive black holes form and
17:26evolve over time.
17:28And that in turn helps us understand how our Milky Way galaxy and its supermassive black
17:32hole has formed.
17:36By studying, not just making images of black holes, but making videos of black holes and
17:40seeing as that gas is spinning around it, we can try to map around a black hole more
17:45precisely and learn about its dynamics.
17:49An image of Sagittarius A star remains out of reach.
17:53But in 2018, it shows a deadly side to its character.
18:00The supermassive black hole's accretion disk releases huge, powerful flares.
18:06And they could be pointed right at us.
18:13In 2018, astronomers were studying a special star.
18:19The star is called S2, and it passes close to Sagittarius A star every 16 years.
18:28By studying the star's flyby, we hope to learn more about Sagittarius A star.
18:35We think that S2 may be the very closest star to the supermassive black hole in the center
18:39of our galaxy.
18:41At closest approach to Sag A star, S2 comes within 17 light hours or so of the surface.
18:51The supermassive black hole's powerful gravity accelerates the star to 17 million
18:56miles an hour.
18:58That's fast enough to travel from New York to L.A. in half a second.
19:04But it's not the star's speed that excites scientists.
19:10This is a great star because it's on an elliptical orbit that takes it fairly far
19:14from the black hole, but every few years it passes right above the supermassive black
19:19hole.
19:22As we tracked S2's swing around Sagittarius A star, we detected powerful bursts of infrared
19:29light coming from the direction of the supermassive black hole.
19:34There's a blob of gas that is orbiting very close to the black hole, and it was flaring
19:42as it went around.
19:43There were three separate flares of light that they were able to detect.
19:48The flares didn't come directly from the supermassive black hole.
19:54They came from material around it.
20:00The flares that were discovered are thought to originate from magnetic storms and this
20:04very, very hot turbulent gas around the black hole.
20:10The extreme heat in the accretion disk strips electrons from atoms of gas.
20:16The stripped electrons and hot gas form a plasma, which creates powerful magnetic fields
20:22when accelerated to high speeds.
20:27Because some supermassive black holes have these superheated, rapidly spinning vortices
20:32of gas swirling around them, you get these very, very powerful, very tightly wound magnetic
20:37fields.
20:40And there's energy stored in that magnetic field.
20:42It's like a bunch of piano wires all tangled up.
20:45And if these things interact with each other, they can snap.
20:48And when they snap, that energy is released.
20:52You get this enormous release of energy as these coils of magnetic fields effectively
21:00snap.
21:01And when they do so, just like on the surface of our sun, they release an enormous flare
21:07of gas.
21:12These powerful flares can be millions of miles wide and come packed with superheated gas
21:20and plasma.
21:25Solar flares release as much energy as 10 million volcanic explosions.
21:36Flares from Sagittarius A star's accretion disk are like millions of solar flares all
21:43going off at once.
21:48It's kind of like comparing a nuclear weapon to a firecracker.
21:54Sagittarius A star's flares release intense blasts of radiation.
21:59But by watching the flares from Earth, we can learn about the orientation of the supermassive
22:04black hole's accretion disk.
22:09This gas that's in this accretion disk around the black hole is like a friendly helper shining
22:15a flashlight back toward Earth.
22:17We can watch the orbit of these flashlights and help understand the orientation of gas
22:22that swirls around the black hole.
22:27We think we're getting a bird's eye view of it and looking down the barrel or looking
22:31at the accretion disk basically face on.
22:35That means that any material that gets blasted away from the black hole could be aimed right
22:39at us.
22:43Should we be worried about the flares reaching Earth?
22:49It sounds worrisome, this blob of gas emitting these huge flares of light.
22:53But you've got to realize, this is 26,000 light years away.
22:57That is a long way.
22:58It took an extremely sensitive detector on one of the largest telescopes on Earth to
23:03be able to see this at all.
23:06Earth is safe, for now.
23:08But the more we learn about the galaxy's center, the more terrifying it becomes.
23:15We know of Sagittarius A star, the central supermassive black hole.
23:19But now we're beginning to suspect that it might not be alone.
23:25A dangerous swarm of black holes could be racing around the center of the Milky Way.
23:32Thousands more may be hiding from sight.
23:39The supermassive black hole, Sagittarius A star, dominates the center of the Milky Way,
23:48blocking star formation and carving out vast gas bubbles in space.
23:58But Sagittarius A star may not be the only black hole in town, or even the most dangerous.
24:05We've known for a long time that there's a supermassive black hole in the very heart
24:11of our galaxy.
24:12But there may be an angry swarm of smaller black holes buzzing all around it.
24:18In April 2018, astronomers led by Columbia University revealed the results of a hunting
24:25mission in the center of the galaxy.
24:27They'd used 12 years of Chandra Observatory data to seek out stellar-mass black holes.
24:36Black holes that are made from the death of stars from supernova explosions are called
24:41stellar-mass black holes.
24:48And these are made from stars that were many times the mass of the sun.
24:56Finding stellar-mass black holes is tough.
25:00Light can escape a black hole's gravity, so we can't see them directly.
25:09And stellar-mass black holes are only tens of miles wide, making them almost impossible
25:14to detect.
25:18So astronomers look for a special type of stellar-mass black hole.
25:26One of the ways that we look for stellar-mass black holes is that they often are vampires
25:33eating a companion star.
25:40These vampires are part of a binary pair, a stellar-mass black hole in orbit with a
25:47living star, the black hole feasting on its partner.
25:53That black hole is like a very, very deadly parasite for that star.
25:57It is ripping mass off the surface of that star, and that matter is raining down toward
26:02the black hole itself, and that material lights up.
26:09So this allows us to hunt for black holes, not through taking pictures of black holes
26:13directly, but through seeing the material falling to its doom.
26:20Problem is, gas and dust spread throughout the galaxy stops visible light from the binary
26:26pair reaching Earth.
26:28But the binary pair releases another type of light that passes through the gas and dust
26:33more easily, X-rays.
26:36The system itself is emitting X-rays, so they're called X-ray binaries.
26:41So these are useful because the X-ray emission can be very powerful and can be potentially
26:46seen from the Earth, even though the binary is very far away, say at the galactic center.
26:54The glowing disks of material in X-ray binary systems are almost a million times smaller
27:00than the accretion disks surrounding Sagittarius A star, too small for us to see the material
27:07swirling around them in detail.
27:11So we see the X-ray binaries as pinpricks of X-ray light.
27:19Astronomers detect 12 of these X-ray binaries in a small three light year wide patch of
27:25space at the galactic center.
27:28And that means that there could be a much larger collection of these relatively tiny
27:32stellar mass black holes in the heart of our galaxy.
27:37If black holes form the way we think they do, there very likely may be swarms of black
27:42holes racing around Sagittarius A star.
27:47But X-ray binaries that are powerful enough for us to detect are incredibly rare.
27:55We estimate that for the dozen X-ray binaries discovered, there could be up to 1,000 more.
28:07In total, there could be 20,000 stellar mass black holes in this three light year region
28:13of space.
28:23They may be small, but they're dangerous.
28:27Stellar mass black holes are by far deadlier than supermassive black holes.
28:33Stellar mass black holes are more likely to tear things apart when they get too close.
28:39These stellar mass black holes are only tens of miles wide, but are several times the mass
28:45of the sun.
28:47And that makes their gravitational pull increase rapidly as you get close to one.
28:53Even a hundred miles from the event horizon, the gravitational pull can be thousands of
28:57times stronger just a single yard closer to the black hole.
29:04Strong enough to tear you or your spaceship apart.
29:17Supermassive black holes like Sagittarius A star are different.
29:22It's over 4 million times the mass of the sun.
29:25And its event horizon is so large that the gravitational forces increase much more slowly
29:32as you get near.
29:35The event horizon extends for so far that you can be sucked in without knowing it.
29:40And you're lost, but you're not ripped apart as you pass through the event horizon.
29:46You can be trapped forever, but not realize it yet.
29:51Why are these black holes swarming in the galaxy's center?
29:55It appears they've migrated from the rest of the Milky Way.
30:01Through a process called dynamical friction, black holes can actually sink to the centers
30:05of galaxies very, very rapidly, like dropping a stone into a pond.
30:09What that means is that an errant, wandering black hole might eventually find its way toward
30:14the center of our own galaxy where Sagittarius A star resides.
30:20As stellar mass black holes orbit the galaxy, they interact gravitationally with stars and
30:27clouds of gas and dust.
30:31These interactions push the black holes towards the center of the galaxy, where the black
30:37holes swarm.
30:44A swarm of stellar mass black holes sounds deadly, but it may not be the most lethal
30:50thing in the center of the Milky Way.
30:55A surprising observation indicates that there is a lot of antimatter in the center of our
31:01galaxy.
31:04In 2017, astronomers tried to solve a decades-old cosmic mystery.
31:13Unexplained high-energy radiation streaming through our galaxy.
31:22At first, we didn't know where it came from, but we discovered it was gamma radiation coming
31:30from somewhere in the center of the Milky Way.
31:36The question is, what's making these gamma rays?
31:39That's hard to do.
31:40It's not like you can rub your hands together and generate gamma rays.
31:44When we took a closer look at the gamma rays, we discovered the signature of the most explosive
31:51substance in the universe, antimatter.
31:58Antimatter is like normal matter, but with opposite charge.
32:03That's it.
32:04It's matter's evil twin.
32:08When evil twin meets good twin, it's not a happy reunion.
32:16Antimatter is scary.
32:17It's not like you want to have some in your kitchen.
32:20This stuff is very, very explosive if you want to think of it that way.
32:24If it touches normal matter, it releases a huge amount of energy.
32:29When matter and antimatter combine, they annihilate each other and transform into high-energy
32:36radiation, just like the gamma rays seen streaming out of the center of the Milky Way.
32:44We see antimatter throughout the galaxy, but strangely, the galactic center seemed to have
32:5040% more antimatter than anywhere else.
32:55Right now in the heart of our galaxy, we actually observe fountains of antimatter that are producing
33:0010 trillion tons of antimatter every second.
33:06One of the big questions that we've wondered about for a very long time is, what's the
33:09origin of this stuff?
33:14Initially, there were several suspects.
33:18One possible source of antimatter is the central supermassive black hole, Sagittarius
33:22A star.
33:23Matter can be swirling around this, and it can have such high energy that it can create
33:27antimatter.
33:32But the antimatter isn't coming from a single point.
33:35It's spread across thousands of light years of space, so Sagittarius A star can't be the
33:43source of the gamma ray stream.
33:48Another suspect was dark matter.
33:53One of the biggest mysteries in the universe right now is dark matter.
33:57We know that the majority of mass in the universe is not in the same form that we are.
34:01It's not made of atoms.
34:03But whatever sort of particle it is or may be, if these things collide, they can produce
34:08antimatter, and that will produce the gamma rays.
34:11So it's possible that as we look into the heart of the galaxy and see these extra gamma
34:15rays, that's the signal that dark matter is there.
34:21But the gamma ray stream we detected is too weak to have been created by dark matter.
34:31Then we had a breakthrough.
34:34We discovered that a special metal called titanium-44 could be responsible for the gamma
34:40ray stream.
34:46Titanium-44 is a highly radioactive element.
34:49That means that it wants to decay into other types of nuclei.
34:56When titanium-44 decays, it gives off antimatter.
35:00But to produce the antimatter seen in the galaxy's core, you need a lot of titanium-44.
35:08Titanium-44 could be created in rare energetic events.
35:13In the collision of two dead stars, white dwarfs.
35:19A white dwarf star is a star that didn't have enough mass when it died to actually become
35:23a supernova.
35:24It just sort of cools off as a dead little cinder.
35:27But what if you have two white dwarfs that are orbiting around each other?
35:30And as they come closer and closer and collide, all of a sudden now you have enough mass to
35:35actually kick a supernova explosion off.
35:43These particular kinds of supernovae are very good at producing titanium-44.
35:49So these kinds of supernovas are very, very good at making antimatter.
35:56These supernovas erupt in the core of the galaxy once every 2,000 years.
36:05But outside of the core, in the disk of the galaxy where our solar system orbits, these
36:12supernovas happen three times as often.
36:17So the gamma-ray observations were wrong.
36:20There isn't more antimatter in the heart of the galaxy.
36:24It's our region of the galaxy that contains the most antimatter.
36:32The question is, are we in danger?
36:37If you take an ounce of matter and an ounce of antimatter and collide them, you're generating
36:41a megaton of energy, the equivalent of a million tons of TNT exploding.
36:48So you don't need much antimatter to generate a vast amount of energy.
36:53But the thing you have to remember is we live in this wonderful, dramatic environment of
36:58the larger universe.
36:59It's not dangerous.
37:00It's very far away from us, and it's fascinating that all of this antimatter is being produced
37:07in our galaxy.
37:09So just sit back and enjoy the fireworks.
37:19The Milky Way is around 100,000 light-years across, and it's home to at least 200 billion
37:26stars.
37:27But it hasn't always been this large.
37:31We know that our Milky Way galaxy grew to the size it is now, which is huge, by eating
37:38other galaxies.
37:40And some of these galaxies would have had supermassive black holes in their centers.
37:48When the Milky Way's gravity pulled in smaller galaxies, most of their material merged with
37:54the Milky Way.
37:57But some material, like stars, could have been slung tens of thousands of light-years
38:03out of the Milky Way.
38:07This could even have happened to a smaller galaxy's supermassive black hole.
38:12It is entirely possible there are supermassive black holes wandering around out there, not
38:19in the center.
38:23So how could it be possible that there's actually a supermassive black hole close to
38:26us wandering around, but we never even see it?
38:29Well, remember, black hole means it's really, really black.
38:32It actually absorbs radiation in any energy.
38:35So unless something is falling into a black hole or orbiting around it, you're not going
38:39to see it.
38:41And so if this supermassive black hole were hypothetically wandering the outskirts of
38:45our galaxy, well, there's a lot less gas there for that black hole to run into.
38:50And if there's no gas around that black hole, we will not see it.
38:56The rogue supermassive black hole may not stay in the outskirts of the galaxy forever.
39:03Gravitational interactions slowly pull it back into the Milky Way.
39:08Billions of years later, the supermassive black hole arrives in the center.
39:18On the way in, it could cause havoc for solar systems like our own.
39:24If a solar system is disturbed by a wandering black hole, then the nice, ordered architecture
39:36of the orbits of its planets are completely disrupted.
39:42In our solar system, the orbits of the planets are perfectly ordered.
39:49If a black hole came even a little too close, its gravity could throw the planets into chaos.
39:58Some planets might be flung out of our solar system.
40:01Others might be plunged down into the nuclear furnace of the sun.
40:12Some planets could face the ultimate destruction, being eaten by the rogue black hole.
40:23If we can't see them, could one be about to wander through our solar system?
40:34So hypothetically, a wandering black hole could, yes, impact our solar system.
40:41But I can't overstate how profoundly unlikely that is to happen.
40:45Galaxies are mostly empty space.
40:46We are just this speck in this cosmic vortex that is our galaxy.
40:50And so our solar system is a really, really, really small target.
40:58When this rogue, supermassive black hole meets up with Sagittarius A star, the fuse is lit.
41:07The pair spiral towards each other, spinning faster and faster, reaching up to half the
41:16speed of light.
41:20Finally, the two black holes merge.
41:33You would have an enormously energetic event on your hands.
41:37Those supermassive black holes could, in principle, merge together, create a huge blast of gravitational
41:42waves, accompanied by a profoundly energetic flash of light that could, in principle, endanger
41:48all life on Earth.
41:56It's literally a stretching and contracting of space itself.
42:00It's like grabbing the framework of space and shaking it really hard.
42:04And if this happens in our galaxy, the amount of energy emitted, that would be, that would
42:10be bad.
42:14When the black holes collide, they release more energy than all of the stars in the universe
42:19combined.
42:28Should we be panicked about this?
42:30And the answer is no.
42:32The Earth has been orbiting the sun for four and a half billion years without any incident,
42:36right?
42:37We're pretty safe from them.
42:39If we were around to see the two black holes collide, we'd witness the most destructive
42:45light show in history.
42:50But for now, the center of our galaxy is relatively quiet.
42:55But it's still a terrible place to be.
43:02The center of our Milky Way is not a friendly place.
43:05It's nowhere you want to be.
43:08It's a bad neighborhood.
43:09You've got tons of stars, tons of radiation.
43:14Stars are being born and dying and exploding.
43:17You've got the central supermassive black hole.
43:19You've got a potential swarm of black holes.
43:22You've got accretion disks.
43:23You've got flares.
43:24You've got magnetic outbursts.
43:26You've got jets.
43:28Let's just stay out here in the suburbs, all right?
43:32The center of our galaxy is one of the most nightmarish places in the cosmos.
43:41It's also home to some of the most incredible forces the universe has to offer.
43:49Whatever the future holds for our galaxy, the core of the Milky Way will be at the center
43:57of it all.
43:59Our home galaxy, the Milky Way, is our safe harbor, our island in this vast cosmic ocean.
44:06And so to understand the heart of our galaxy is to understand our home in this cosmic void.