Journeys to the heart of the M87 supermassive black hole, the first and only black hole ever photographed, and explores the mystery of how it grew so large, what lies inside, and how it controls the entire galaxy.
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LearningTranscript
00:00:00We're on a journey to the heart of the supermassive black hole, M87 Star.
00:00:09Our mission? To investigate one of the most mysterious places in the universe.
00:00:15M87 is a great target for us to visit because one, it's close, and two, it's active, it's feeding.
00:00:25Supermassive black holes are the engines that power the universe.
00:00:32Supermassive black holes are a key factor in the birth, life, and eventual death of galaxies.
00:00:40And the more we study them, the more puzzling they become.
00:00:45They're the master key to most of the unsolved mysteries in physics.
00:00:50The physics inside a supermassive black hole are beyond weird.
00:00:55They are the final frontier of our understanding.
00:00:59Your imagination can run wild. Maybe it's even the source of other universes.
00:01:04There's only one way to find out. To go where no one has gone before.
00:01:10And journey to the heart of M87 Star.
00:01:17We speed across M87.
00:01:32A gigantic galaxy 55 million light years from Earth.
00:01:38At its heart lies a supermassive black hole.
00:01:45M87 Star.
00:01:48It is the first and only black hole ever photographed.
00:01:55We want to find out how M87 Star grew so large.
00:02:00What lies inside and how it controls the galaxy.
00:02:095,000 light years out from the supermassive black hole.
00:02:13We get our first sign of the danger ahead.
00:02:16We see giant holes carved out of the galaxy.
00:02:20Starless voids thousands of light years wide.
00:02:25As we approach, we can see that wreckage littered around the vicinity.
00:02:32It's like entering the lair of the dragon and seeing the bones of all the explorers who came before you.
00:02:38What cataclysmic force tore these giant cavities in the galactic gas clouds?
00:02:45As we fly next to a brilliant shaft of energy.
00:02:54Thousands of light years from M87 Star.
00:02:58We get a clue.
00:03:03It's a deadly stream of radiation shooting out across the galaxy.
00:03:08A jet.
00:03:10This jet looks like a searchlight or a beam from a lighthouse.
00:03:17You're seeing this monumental thing.
00:03:19It's screaming out of the black hole, blasting out radiation.
00:03:23When I first saw a photo of a jet, I was like, whoa, am I like misreading the scale of this image?
00:03:31Because there was this crazy Star Trek like beam that's coming out.
00:03:36In 1918, American astronomer Hebert Curtis described the jets as a curious straight ray.
00:03:49A century later, observatory images reveal they pulsate with energy.
00:03:55The images show knots and clumps in these jets.
00:04:00They show that it's just not smooth and nice.
00:04:04That there's been a history of violence inside this jet.
00:04:10This violent energy pushes the knots along the beams.
00:04:15The knots reveal the speed of the jets.
00:04:18It's like looking at a fast-moving train.
00:04:25Rail cars of the same color blur into one continuous image.
00:04:33But different colored cars stand out against the others.
00:04:38It's the same with the knots moving along the jets.
00:04:43So we can figure out how fast the jets are really moving by looking at knots of material coming out from near the black hole.
00:04:50When astronomers measured the speed of two knots, they got a big surprise.
00:04:56One is moving at 2.4 times the speed of light, and the other is moving over six times faster than light.
00:05:04How could this possibly be?
00:05:06As weird as the physics around a black hole is, that's not actually happening, nor is it allowed to happen.
00:05:14Nothing can actually go faster than the speed of light, so obviously we're missing something here.
00:05:21The knots may seem to break the speed of light, but the universe is just playing with us.
00:05:29It's really just a consequence of the fact that a lot of this jet is pointed toward us, pointed partially toward the observer on Earth.
00:05:39That, in a sense, a sort of optical illusion tricks you into thinking it's moving faster.
00:05:44It's a simple trick of the light, a bit like the way a spoon in a glass of water looks bent and distorted.
00:05:53The impossibly fast speed of the jet is just an illusion of perspective.
00:05:59From our perspective, it looks like the whole thing is moving towards us faster than light,
00:06:04but really it's just cruising along very, very fast.
00:06:09The jets aren't actually breaking the laws of physics. They're pushing up against it.
00:06:13They're going at 99.999995% the speed of light.
00:06:18Imagine the energies necessary to accelerate this entire jet to that speed.
00:06:26So, what could produce enough energy to blast jets across the galaxy at close to the speed of light?
00:06:36There is a clue far ahead.
00:06:39The jets shoot out from a tiny, brightly glowing object.
00:06:43This is where things go nuts. This is the center of the action. This is where the real stuff happens.
00:06:52A ring of super hot gas and dust whirls around the supermassive black hole.
00:06:59It's called the accretion disk, and it shines a billion times brighter than the sun.
00:07:06If you had a ringside seat next to M87 star, you would probably be fried very, very fast.
00:07:17But if you were some, you know, magical being and could survive anything, and if you had, you know, million SPF sunscreen and really, really great sunglasses,
00:07:30what you would see is this enormously bright vortex of gas swirling this dark void.
00:07:36This bright vortex spins around the supermassive black hole at over two million miles an hour.
00:07:45So there's a tremendous amount of friction as material moving slower and faster rubs against each other.
00:07:51That's what's heating the disk up, and that's what's causing it to glow.
00:07:54Scientists think that the intense energy of the accretion disk is the source of the jets.
00:08:04The hot swirling gas and dust produces powerful magnetic fields.
00:08:10As the disk spins, it twists up the magnetic fields at the poles of the black hole. Energy builds.
00:08:17Finally, the magnetic fields can't contain the energy any longer.
00:08:24They snap and blast the jets out into the galaxy.
00:08:29Even many light years away on the ship, we can see this violent release of energy.
00:08:36It's like the universe's biggest fireworks display.
00:08:41Two jets streaking out of M87 star's poles.
00:08:45One shooting away into the distance.
00:08:49The other racing past our ship.
00:08:53We're at a safe distance.
00:08:56Other things are not.
00:08:59So when these jets shoot outward from this supermassive black hole, they don't shoot outward into nothing.
00:09:05If a jet hits a gas cloud, it annihilates it. It just punches a hole right through it.
00:09:10It's like a train going down a snowy track, right? The gas is like the snow and the jets are like this freight train plowing across it.
00:09:19But here, a freight train traveling at close to the speed of light, smashing into clouds of gas, lighting our way to M87 star as we follow the trail of destruction.
00:09:40There is evidence of similar destruction across the universe.
00:09:50In the Cygnus A galaxy, supermassive black hole jets have caused damage on a colossal scale.
00:09:56In many ways, Cygnus A is like a cosmic shooting gallery. You see this crime scene, this beautiful mess.
00:10:06So when this jet comes out of the nucleus of Cygnus A, it's going to encounter gas clouds.
00:10:11At that point, shock waves set up. And this jet just rips right through this material, sending shock waves in every direction, creating absolute chaos.
00:10:22It's hard to believe how much devastation these jets can cause.
00:10:27They're punching a hole in the gas 100,000 light years wide. I mean, that's the scale of an entire galaxy.
00:10:33As we head towards the center of the M87 galaxy, we enter hostile territory.
00:10:46The closer to the supermassive black hole we travel, the more dangerous it gets.
00:10:52As we approach the central core of M87, we start to feel it.
00:10:57But all this energy, all this ferociousness is powered by that black hole.
00:11:04Intense winds start to buffet the ship.
00:11:10They push away vital gas, quenching star birth.
00:11:17Could these winds end up killing the galaxy and M87 star itself?
00:11:22We're on a mission to explore the supermassive black hole M87 star.
00:11:42First, we have to cross the M87 galaxy.
00:11:48It's 120,000 light years across and it looks like a giant puff ball.
00:11:56M87 is an absolute monster.
00:11:59It's a giant elliptical galaxy.
00:12:02And that means that as you go from the edges to the interior, you see a higher and higher density of stars.
00:12:09This vast galaxy contains several trillion stars.
00:12:13What's strange is that almost all of them are the same color.
00:12:21So as you see, your sky is covered with countless red points of light everywhere you look.
00:12:31Most of these points of light are small, long-living stars called red dwarfs.
00:12:37So what happened to the different colored stars that we see in other galaxies?
00:12:42When you create lots of stars, you make lots of blue and red stars, but the blue ones don't last very long.
00:12:50They explode and are gone.
00:12:52The red ones, the ones that are lower mass, those are the ones that live for many, many billions of years.
00:12:57M87 hasn't made stars in so long that its stars are mostly red.
00:13:01We call galaxies with mainly red stars red and dead.
00:13:08So the only stars that are left in these red and dead galaxies are billions of year old populations.
00:13:16And since it's not making new stars, the clock is ticking on M87.
00:13:21Essentially, it's a dead galaxy walking.
00:13:25The M87 galaxy hasn't made any new stars for billions of years.
00:13:31Something had to make that happen.
00:13:34Something had to deplete or heat up or push away the gas in those galaxies that would otherwise go into forming stars.
00:13:43We think that black holes in the centers of galaxies are the ultimate answer to this.
00:13:47So how did M87 star kill off star formation billions of years ago?
00:13:56As we cruise towards the supermassive black hole, we get a clue from the strong winds buffeting the ship.
00:14:04So these winds can be incredibly powerful and really, really fast, right?
00:14:10You think a hurricane on Earth is bad? You should see some of these winds.
00:14:13In space, winds are made up of gas and superheated plasma.
00:14:20The power that generates the winds lies ahead.
00:14:25The bright accretion disk surrounding M87 star.
00:14:29Because it's so incredibly hot, it liberates an enormous amount of light.
00:14:34And that light can drive a wind.
00:14:37And so black holes can power winds.
00:14:39They power winds with light itself.
00:14:43And the more material that's falling into that accretion disk, the bigger and hotter it gets.
00:14:48And the more powerful the wind is that the black hole blows.
00:14:51We understand that light from the accretion disk creates the winds.
00:14:57But that is about all we know.
00:14:59We don't know that much about the wind.
00:15:01Is it expanding in all directions, like a sphere?
00:15:04Or is it aimed in jets, very narrow and only moving in two different directions?
00:15:09Now, measuring the effect of the winds isn't as easy as you might think.
00:15:13It's not like going outside on a windy day and doing one of these.
00:15:16You have to infer what's going on with the winds by studying the light emanating from this object.
00:15:20We wanted to find out if black hole winds expand like a bubble or travel in narrow streams.
00:15:31So we studied how iron dust from the accretion disk blocks the light driving the wind.
00:15:38Astronomers found the answer when they looked in the X-ray light spectrum.
00:15:43And what they detected was iron absorbing those X-rays in every direction they looked around the black hole.
00:15:52That's only possible if the black hole is blowing out a wind in every direction.
00:15:57Which means that it is definitely blowing out a spherical wind which is expanding into that galaxy.
00:16:02And so these black holes can almost literally inflate this growing sphere or bubble of gas
00:16:08that's outward flowing from the heart of the galaxy.
00:16:13These winds push out throughout the entire galaxy of M87.
00:16:19Transporting heat and energy throughout the entire volume of the galaxy.
00:16:26What we found is that it's expanding away from the black hole at a quarter of the speed of light.
00:16:3240,000 miles per second.
00:16:36And for the M87 galaxy, that is bad news.
00:16:39Is bad news.
00:16:40Because hot powerful winds kill off star birth.
00:16:46The winds can push away the gas that would have normally formed stars.
00:16:51So they can effectively quench star formation in a galaxy causing it to gradually die.
00:16:58And it gets worse.
00:17:02In order for a galaxy to produce stars, it needs lots of gas and dust.
00:17:07And that gas and dust needs to be incredibly cold.
00:17:10Hot winds from the black hole heat up gas clouds so they can't collapse into stars.
00:17:15As M87 star has grown, it has slowly shut down star formation.
00:17:25As the black hole in the center of the galaxy grows, it has stronger and stronger winds.
00:17:30And this means it's going to drive out more and more matter.
00:17:33And that's what makes it a galaxy that can no longer support star formation.
00:17:37So a supermassive black hole can determine the star formation happening in the galaxy.
00:17:44It can help to regulate the amount of gas in the galaxy and therefore the number of stars that are formed in a galaxy.
00:17:53Although M87 star is tiny compared to the vast galaxy around it, it still controls its host.
00:17:59When you compare it to the size of the galaxy it's sitting in, it's like comparing a grape to the size of the Earth.
00:18:09So to think that something so relatively small compared to the galaxy could have such a profound effect over effectively all of cosmic history is just this remarkable illustration of how energetic a black hole can be.
00:18:23In the relationship between a supermassive black hole and the material surrounding it, the black hole is in charge.
00:18:33Although M87 star calls the shots, its past, present and future are inextricably linked to its host galaxy.
00:18:44The view from our ship is endless space, calm and unchanging.
00:18:49But the M87 galaxy has a violent past.
00:18:54A history of cannibalism, death and destruction.
00:19:00We've traveled thousands of light years across the M87 galaxy.
00:19:03But its supermassive black hole is still far in the distance.
00:19:06From our current position, M87 star may look small.
00:19:10But it's 6.5 billion times the mass of the sun.
00:19:12We've traveled thousands of light years across the M87 galaxy.
00:19:18But its supermassive black hole is still far in the distance.
00:19:22From our current position, M87 star may look small.
00:19:27But it's 6.5 billion times the mass of the sun.
00:19:34So how did it get so big?
00:19:36One of the big mysteries that we're still trying to understand is what controls how big the giant black holes at the centers of galaxies become.
00:19:44And we know that it's tightly correlated with things like how big the galaxy is.
00:19:50Bigger galaxies have bigger black holes.
00:19:54To understand how M87 star became so big, we have to investigate the history of its galaxy.
00:20:01We need to discover how M87 stars host galaxy grew so large.
00:20:09M87 is huge.
00:20:12It's a big galaxy with a big black hole.
00:20:16It's really, really big.
00:20:18It's what we call a brightest cluster galaxy.
00:20:20And these so-called brightest cluster galaxies are among the most massive galaxies in the known universe.
00:20:25Usually, a galaxy with the mass of M87 is much smaller.
00:20:31But M87 is puffed up hugely.
00:20:34Why?
00:20:36One lead comes from the layout of M87 stars.
00:20:41As we travel through the galaxy, we see that the stars spread out over an area 100 times larger than expected.
00:20:49So, what scattered the stars?
00:20:53Galaxies aren't static.
00:20:56Every galaxy is moving.
00:20:57And sometimes galaxies get very close and can interact with each other.
00:21:02Interact is a polite way of describing something extremely brutal.
00:21:09Galaxies are colliding with other galaxies.
00:21:12They're cannibalizing smaller galaxies or tearing each other apart.
00:21:15Sometimes they're like drive-bys and they'll warp each other's structures.
00:21:23Sometimes the galaxies have head-on collisions and merge.
00:21:27Merging pulls in new gas and stars.
00:21:31So galaxies grow larger.
00:21:35Galactic cannibalism is common.
00:21:39Maybe the M87 galaxy ate its neighbors.
00:21:48But how can we find out?
00:21:51We could try to identify stars that came from the consumed galaxies.
00:21:57But that's not straightforward.
00:22:00When you're trying to map out a distant galaxy, it turns out using their stars is a really hard thing to do.
00:22:05They smear in with the foreground and the background.
00:22:09It's actually very difficult to see any evidence that that galaxy merger ever happened.
00:22:12It's all smoothed out.
00:22:14It's kind of like throwing a bucket of water into a pond.
00:22:17And then asking after the waves go away to separate which molecules of water came from the pail of water versus which were in the pond.
00:22:24All you see is just mixed pile of water.
00:22:27And it's similar to that with the stars in a galaxy.
00:22:29So how can you spot water from the bucket in the pond water?
00:22:38We need to detect signs of disruption.
00:22:42Like ripples or distinct streaks of sand and mud thrown up by the disturbance.
00:22:49When galaxies merge, they may also leave a leftover that stands out.
00:22:54Like a planetary nebula.
00:22:56Planetary nebulae are these bright beacons that you can pick out and map out the galaxy with great precision.
00:23:03A planetary nebula forms when a dying, mid-sized star blows off its outer layers after running out of fuel.
00:23:12These outer layers of gas expand, forming a nebula often in the shape of a ring or bubble.
00:23:19And you see this beautiful glowing blue-green blob coming away from the star.
00:23:25These are so much bigger than stars you can pick them out very easily.
00:23:29One team went planetary nebula hunting in the M87 galaxy.
00:23:35As they mapped the galaxy, they picked out 300 distinct glowing points.
00:23:40The points are blue-green, confirming their planetary nebulas.
00:23:47Planetary nebulae are great. They really stand out like needles in a planetary haystack.
00:23:54The nebula's movements are distinct from the stars in M87.
00:24:01This shows they formed in a smaller, younger galaxy, not M87.
00:24:07Because we see these planetary nebulae, something must have happened in this old, dead galaxy.
00:24:11What was it? A galaxy collision.
00:24:15The discovery of the planetary nebulas shows that at some point in the last billion years, M87 ate a smaller galaxy.
00:24:26This galaxy strayed too close to the much larger M87.
00:24:31M87's powerful gravity snared the smaller galaxy and dragged it closer and closer.
00:24:44You could actually see this galaxy getting bigger and bigger and bigger in the sky.
00:24:48And it wouldn't stay the same shape.
00:24:50As the galaxy got closer, it would begin to distort.
00:24:53And your galaxy would distort as well, until the sky was filled with rivers of stars.
00:24:58M87 pulled in the small galaxy and swallowed it whole.
00:25:07Can you think of anything more dramatic than the collision of two galaxies?
00:25:13A violent history of mergers explains how the M87 galaxy grew so large.
00:25:20Each event brought in many millions of stars.
00:25:24The collisions also unleashed enormous gravitational forces, scattering the stars like confetti.
00:25:37After a collision like this, the stars are probably ten to a hundred times more spread out than they were before.
00:25:43Some collisions threw stars around. Others changed the shape of the entire galaxy.
00:25:53If that galaxy merger is violent enough, it injects so much energy into the galaxy that the stars basically all move away from the center.
00:26:02And it makes the galaxy much more puffy.
00:26:04Gradually transforming it into the smooth, featureless elliptical shape.
00:26:14Most galaxies have a supermassive black hole at their center, including those galaxies eaten by M87.
00:26:21So what happened to those black holes? Did they merge with M87 star, increasing its size?
00:26:31M87, the fact that it's an elliptical galaxy, also supports the fact that it's had multiple supermassive black hole mergers,
00:26:38which is how M87 star could have gained its sizable mass.
00:26:41Compared to its violent history, the M87 galaxy is now relatively calm.
00:26:48We think that in the past, M87 star grew by gobbling up other supermassive black holes brought in by collisions with other galaxies.
00:26:59What we don't really know, because physics suggests that supermassive black holes can never merge.
00:27:12Instead, they lock together in a cosmic dance for eternity.
00:27:17As we travel closer to the supermassive black hole, we pass the remnants of smaller galaxies eaten over the last 10 billion years.
00:27:39They reveal how the M87 galaxy got so vast.
00:27:43Most of these consumed galaxies probably had a supermassive black hole of their own.
00:27:53If M87 got so large by eating galaxies, did M87 star get supermassive by consuming other supermassive black holes?
00:28:04So when galaxies merge, all their stars and nebulae mix together and then also their supermassive black holes eventually find each other and find their way down to the center of the newly merged galaxy.
00:28:22Just like dropping two stones into a pond, they'll both reach the bottom, they'll both move toward the center and they will start to move ever closer together.
00:28:30But do the supermassive black holes actually collide?
00:28:36We've witnessed the merging of smaller stellar mass black holes.
00:28:41And we've seen supermassive black holes get close together, but we've never observed them merge.
00:28:48When galaxies merge, their central supermassive black holes should merge.
00:28:55The first step in the merger process, they're sinking towards the center of this newly formed galaxy.
00:29:01As they plunge towards the galactic center, the supermassive black holes plow through fields of stars and clouds of gas.
00:29:08They don't just run into each other, they in spiral toward each other, so they're gonna scatter stars everywhere and the closer they get, the more rapidly they will orbit each other so things get even more and more chaotic and crazy.
00:29:25In all the chaos, something strange happens. The supermassive black holes stop moving closer to each other.
00:29:36This is a problem and we call this the final parsec problem.
00:29:40So what's going on? Why do they stall?
00:29:45The final parsec problem happens when two supermassive black holes run out of material to help them to merge.
00:29:53If there's not enough stars or gas that the black holes can interact with, it takes longer than the age of the universe for them to lose enough energy to merge.
00:30:02And so the black holes effectively stall at this final parsec of separation.
00:30:10The two supermassive black holes locked together in an eternal cosmic dance.
00:30:16Close, but forever apart.
00:30:21But some supermassive black holes must have merged.
00:30:25It's highly likely that many of the galaxies M87 swallowed had supermassive black holes.
00:30:34And yet, on our trip, we haven't seen lots of supermassive black holes, just one M87 star.
00:30:43So, mergers take place, but how?
00:30:48In 2019, we got a clue from a galaxy called NGC 6240.
00:30:59This particular galaxy looks like the aftermath of a massive galactic collision.
00:31:08There are lumps and clumps of stars, random groups of random directions and random velocities.
00:31:13It's all mixed up, which is what we think galaxies look like after a massive merger.
00:31:20The merger aftermath reveals a more complex series of events than a two-galaxy collision.
00:31:27What we find in the center of this galaxy isn't two, but three giant black holes,
00:31:34which suggests that there have been three galaxies colliding in recent history.
00:31:39So, when this new galaxy starts to merge with the galaxy that hosts the stalled pair,
00:31:48it brings in its own third supermassive black hole.
00:31:52Now, this supermassive black hole perturbs the system, and it makes what's at the center highly unstable.
00:31:58The gravity of this third supermassive black hole steals orbital energy from the stalled pair,
00:32:05pushing them closer together.
00:32:06It's almost a thief that comes in and takes away some of that rotational energy from this binary black hole system.
00:32:15As the two supermassive black holes lose orbital energy, they finally come together.
00:32:21The likeliest thing to happen is that the least massive supermassive black hole is ejected,
00:32:26and the remaining two merge very quickly.
00:32:32The high-speed merger will last just milliseconds, but it will trigger a gigantic explosion.
00:32:40When these giant black holes merge, more energy is released in this process than our entire galaxy will emit over the course of billions of years.
00:32:54Perhaps M87 star merged with other supermassive black holes in the same way, a third black hole helping it to overcome the final Parsec problem.
00:33:09It's possible that mergers with other supermassive black holes allowed M87 to reach its sizable mass of six and a half billion solar masses.
00:33:20Supermassive black holes meet their match when they square off against each other.
00:33:27The fallout is cataclysmic, and as we get closer to M87 star, our mission becomes more dangerous.
00:33:38We enter the gravitational kill zone surrounding the supermassive black hole.
00:33:43We know the dangers.
00:33:46Any unwitting stars that get too close are stretched, shredded, and torn apart, creating one of the biggest and brightest light shows in the universe.
00:34:13As we get closer to M87's supermassive black hole, we enter dangerous territory.
00:34:22Not just for us, but also for wandering stars.
00:34:27If the black hole snares them, they are toast.
00:34:33But their death may solve one of the mysteries of supermassive black holes.
00:34:38How fast they spin.
00:34:40It's difficult to calculate just how fast a featureless black object hidden by a bright disc rotates.
00:34:50You need a lot of patience and a little bit of luck.
00:34:54Astronomy is sometimes a pretty opportunistic science.
00:34:57You have to be looking at the right place at the right time to figure out something new that we've never seen before.
00:35:03Recently, astronomers caught a break when they spotted an extremely bright flare in galaxy PGC 043234.
00:35:15It was hard to miss.
00:35:18The flare was 100 billion times brighter than the sun.
00:35:22And the energy output was absolutely ridiculous.
00:35:31If this happened in the center of our galaxy, it would have been so bright we could see it during the daytime.
00:35:36A routine search for supernovas, violent deaths of giant stars, detected the intense flash.
00:35:47Assassin is this network of telescopes designed to look for brief high energy events all around the sky.
00:35:56And primarily supernova.
00:35:57They saw a bright flash and they thought, oh yay, another supernova.
00:36:05If you see a bright flash of light coming from a galaxy, that's kind of your first thought.
00:36:10But it didn't look like a supernova at all.
00:36:12It didn't act like a supernova flash would.
00:36:16It didn't have the right characteristics.
00:36:18It wasn't behaving like a typical supernova.
00:36:20It had to be something else.
00:36:21So they send out an alert to the astronomical community saying, hey, there's something cool happening in this region of space.
00:36:30Once an event is flagged as real, then what happens is other telescopes turn their attention to that event.
00:36:39The data revealed something strange.
00:36:42After the initial flash, there are still smaller flashes that repeat.
00:36:47And if you're going to kill a star and a supernova, there's nothing left to repeat like that.
00:36:56Intriguingly, it flashed on and off about once every 130 seconds.
00:37:03The flashes continued for 450 days.
00:37:08When astronomers looked at this galaxy in detail, they saw that this event happened right at the center.
00:37:13And there's a black hole there with about one million times the sun's mass.
00:37:18And that was, that's it, man.
00:37:19That's the smoking gun.
00:37:21What they observed was an extremely rare phenomenon.
00:37:25A tidal disruption event.
00:37:28Catching one live as it happens is an astronomer's dream.
00:37:33This was our first time catching a black hole in the act of feeding on a star.
00:37:37In galaxy PGC 043234, a star wandered too close to a supermassive black hole.
00:37:47As this unfortunate star got close to the black hole, the black hole is spinning.
00:37:53And the gravity around this monster black hole is so strong that it could pull the star apart.
00:38:06The side of the star closer to the black hole is feeling a much, much stronger gravitational pull toward the black hole than the far side of the star because it's farther away.
00:38:14And what this does is it stretches the star.
00:38:20So it got ripped to shreds, it got shredded, it got pulled out and stretched and whipped around the black hole.
00:38:31And this stretches the star into some giant long arm and that swirls around and is trapped as it orbits the black hole.
00:38:38The accretion disk snares the shredded star.
00:38:42And what this means is that that accretion disk is going to increase its output of radiation, in particular high energy radiation.
00:38:52As the star embeds in the accretion disk, a massive flare of radiation erupts, lighting up the universe.
00:39:01After this initial burst, the spinning star debris sends out a continuous stream of light.
00:39:14Our telescopes only pick up this radiation on each rotation of the disk.
00:39:20It's like seeing the beam from a lighthouse every one hundred and thirty seconds.
00:39:25The flashes are the final pulses of a dying star.
00:39:33And those flashes reveal both the width and the rotation speed of the supermassive black hole.
00:39:41We learned that the central massive black hole is about three hundred times wider than the earth.
00:39:49But it's rotating every two minutes.
00:39:53It's rotating at half the speed of light.
00:39:56That's over three hundred million miles an hour.
00:40:00We don't yet know how fast M87 star is spinning.
00:40:04But we do know the accretion disk rotates at over two million miles an hour.
00:40:10This glowing ring, hundreds of light years wide, now lies directly ahead of our ship.
00:40:17It is one of the most awe-inspiring and deadly places in the universe.
00:40:24And we are heading straight for it.
00:40:26After our long trek across the galaxy, we finally face the mighty supermassive black hole at its center, M87 star.
00:40:51A dazzling glare confronts us.
00:40:53This is the accretion disk.
00:40:57A ring of hot gas and dust spinning at over two million miles an hour.
00:41:03M87 star's accretion disk is so bright, the Event Horizon Telescope photographed it from Earth, 55 million light years away.
00:41:15So I remember exactly where I was when that image was released.
00:41:18I was sitting with a bunch of my colleagues at the Center for Astrophysics,
00:41:20and we were all watching the press conference live and just absolutely slack-jawed when that image hit the screen.
00:41:27I was sitting in the airport when I saw this black hole image, about to take a flight to New York.
00:41:33I got so excited that I actually walked away from my backpack sitting there.
00:41:37Seeing that picture, it really doesn't leave room for doubt. Black holes are real.
00:41:47The Event Horizon Telescope photo is the first picture ever taken of a black hole.
00:41:53The image revealed M87 star spins in a clockwise direction, and it's 23.6 billion miles wide.
00:42:06That's around three million Earths lined up in a row.
00:42:09The photo also confirmed M87 star's membership in a very exclusive club, the 1% of supermassive black holes that actively feed.
00:42:24The image from the Event Horizon Telescope tells us that M87 is indeed actively growing and accreting and eating material around it.
00:42:31It shows gas swirling around that black hole on its way to being swallowed.
00:42:37But do all supermassive black holes consume material in the same way that M87 star does?
00:42:44Is it possible that different black holes have different table manners?
00:42:48Well, it turns out that's really true. Some are more delicate eaters.
00:42:51In 2018, we discovered a supermassive black hole, 250 million light years from Earth, that eats on a schedule.
00:43:05Now we have this case of a black hole that looks like it's feeding three times a day.
00:43:12It's having three square meals a day.
00:43:13Intense bursts of energy pulse out from galaxy GSN 069.
00:43:21We see X-ray flares and bursts coming from the center of this galaxy, repeating every nine hours.
00:43:30And each burst is associated with a new feeding event.
00:43:36This supermassive black hole not only eats on a schedule, it has a very healthy appetite.
00:43:41Each one of these meals that this black hole is consuming is the equivalent of four of our moons in a single bite.
00:43:55So what exactly is this supermassive black hole consuming?
00:44:02The most likely contender is the star.
00:44:04We think that the star has been ripped apart and spread throughout an accretion disk.
00:44:13And then slowly over the course of hours, an instability builds up and some material falls in.
00:44:20When the infalling material from the star hit the supermassive black hole, it triggered a burst of X-rays.
00:44:26Then the system stabilized until it sparked up again, creating a nine hour cycle of bursts of energy.
00:44:41Then in 2020, new observations spawned a different theory.
00:44:46The star wasn't caught on the accretion disk.
00:44:51The supermassive black hole had instead pulled it into orbit.
00:44:56Its orbit takes it near that black hole every nine hours.
00:45:01And every time it encounters the black hole, some of its material gets sipped off.
00:45:06Eventually, the GSN-069 supermassive black hole will lose its meal ticket.
00:45:17But it's luckier than many other supermassive black holes.
00:45:22Sometimes black holes just take a little nibble on the surrounding material and just give a little burp of radiation in response.
00:45:30A black hole burp generates strong shock waves that radiate out across the universe.
00:45:39We detected two of these energy outbursts in galaxy J 1354 plus 1327 located 800 million light years away.
00:45:53The huge burps suggested that the supermassive black hole at the core of this galaxy was snacking.
00:46:04It ate a bunch of material one time.
00:46:06That caused a burst of energy flowing outward.
00:46:09Then it feasted again and that caused another burp.
00:46:13What caused these separate outbursts?
00:46:16The belching black hole galaxy has a smaller companion galaxy.
00:46:25A gas stream links the two galaxies supplying an intermittent on-off food supply.
00:46:32There's actually a smaller satellite galaxy going around the bigger galaxy.
00:46:36The black hole in the middle is pulling streams of material off this little galaxy.
00:46:40Clumps of material from the companion galaxy move toward the center of J 1354.
00:46:48Once there, the supermassive black hole grabs them.
00:46:53Some gas streaming from the neighboring galaxy reaches the center of the bigger galaxy when the black hole feeds and then ejects a jet.
00:47:03When supermassive black holes like the one in J 1354 receive an irregular supply of food, a cycle is established.
00:47:14A routine that scientists call feast, burp, nap.
00:47:22The supermassive black hole we're headed towards, M87 star, doesn't do burp and nap.
00:47:33It feasts all the time.
00:47:36Stars come in and get ripped apart maybe once every 10,000 or 100,000 years,
00:47:41whereas M87 has been shining brightly for millions of years.
00:47:45It clearly has a supply of gas other than ripped apart stars that's feeding the accretion disk.
00:47:54This helps explain how M87 star grew to 6.5 billion solar masses.
00:48:04But what about the future?
00:48:05Will this supermassive black hole continue to feast?
00:48:13Or will it starve?
00:48:15To find out, we have to move even closer.
00:48:19Across the accretion disk to discover just how M87 star satisfies its insatiable appetite.
00:48:35Our ship passes over the accretion disk of M87 star.
00:48:48A blazing ring of gas and dust hundreds of light years across.
00:48:54This is the supermassive black holes grocery store.
00:48:59Black holes are known for sucking in everything.
00:49:02But is that really true?
00:49:05Black holes don't really suck.
00:49:06It's a popular misconception.
00:49:08They don't just pull anything in.
00:49:10In fact, if the sun just instantly turned into a black hole today,
00:49:14the Earth would happily continue on in its orbit,
00:49:17because all that gravity cares about is how massive and how far away something is.
00:49:21Supermassive black holes like M87 star are a lot more massive than a regular sun-sized black hole.
00:49:28This means their gravity is greater and extends much farther out into the galaxy,
00:49:35allowing supermassive black holes to attract dust, gas clouds, and stars from billions of miles away.
00:49:43But they don't gulp down everything they pull in.
00:49:47The way black holes eat matter isn't as straightforward as you might imagine.
00:49:53Earth gains mass every day from objects falling to it from space.
00:49:58So you might imagine that matter falling onto a black hole is like meteorites falling onto Earth.
00:50:04They can come in from any direction and land anywhere.
00:50:06That's not the case around a supermassive black hole.
00:50:12The most efficient way for a black hole to consume matter is for it to grow an accretion disk.
00:50:19Accretion disks grow when gas and dust dragged in by the supermassive black hole's gravity spirals inward and piles up in a ring.
00:50:30The ring starts to spin from the combination of gravity and the momentum of the gas and dust.
00:50:38The spinning material flattens into a disk.
00:50:42The material doesn't fall straight in. It orbits its way in.
00:50:47And so it gets accelerated to incredibly fast speeds.
00:50:52Sometimes the matter ends up inside the black hole.
00:50:55Sometimes the matter ends up getting kicked away from the black hole.
00:50:57As we traveled through M87, we witnessed jets and winds from the supermassive black hole blast this material out into the galaxy.
00:51:10But there may be other things that stop food from entering a black hole.
00:51:15The black hole at the center of our Milky Way galaxy, what we call Sagittarius A-star, appears to be swallowing material or eating at an incredibly low rate.
00:51:25To discover what's stopping Sagittarius A-star, or Sag A-star for short, from feeding, scientists studied infrared light moving out from the supermassive black hole.
00:51:39To do that, they needed to fly high in Earth's atmosphere.
00:51:43The problem is, water vapor in our atmosphere prevents infrared light from space from getting down to the ground.
00:51:50SOFIA is an infrared telescope built into the side of an airplane.
00:51:57As bizarre as that is, it's a very stable platform.
00:52:01SOFIA can look at these objects emitting infrared in space and get really good observations of them.
00:52:05SOFIA focuses on the structure of the gas in the strong magnetic fields at the center of the Milky Way.
00:52:16This high resolution telescope can track the finest grains of dust.
00:52:22When all the dust grains in a cloud are aligned by a magnetic field, they scatter the light coming at them in a certain way, and we call this polarized light.
00:52:32The dust grains can actually map out the magnetic field embedded in that dust cloud.
00:52:37The telescope picked out the grains arranged in a spiral pattern and revealed the direction the grains were moving.
00:52:46This movement reveals why Sag A-star is starving.
00:52:52The magnetic field is channeling them into orbit around the black hole instead of allowing them to fall in.
00:53:00So it's literally keeping those dust grains away from the black hole.
00:53:03The magnetic fields also pushed clouds of gas, Sag A-star's food source, away from the supermassive black hole.
00:53:13This is the situation now, but that's not necessarily the way things are always going to be.
00:53:20Because magnetic fields can switch directions.
00:53:24There's a lot of other junk out there, dust and gas and other stars, that as they get close they can change the magnetic field
00:53:30and that might allow that dust to fall into the black hole.
00:53:34Magnetic fields changing direction offers hope for Sag A-star.
00:53:41And magnetic fields could help M87-star feed.
00:53:48Our mission continues, following this material plunging down into the supermassive black hole.
00:53:56We set a course towards the event horizon, the boundary between the known and the unknown universe, where the laws of physics no longer apply.
00:54:14Our ship crosses the accretion disk.
00:54:28Ahead, the absolute darkness of the supermassive black hole, M87-star.
00:54:35According to black hole legend, this is where we meet our end, torn to shreds by gravity.
00:54:48We have so much wonderful imagery of what would happen if you were to fall into a black hole from science fiction.
00:54:55One idea that has caught popular attention is the notion that you get spaghettified when you fall into a black hole.
00:55:02This is me, this is a black hole, which is pulling stronger on my feet than on my head.
00:55:10And if this black hole is a little bit heavier than our sun, this difference in pull is so strong that I would actually get spaghettified, torn apart.
00:55:20So, will M87-star spaghettify us?
00:55:31The answer depends on the black hole's mass and volume ratio.
00:55:35A stellar mass black hole with the mass of 14 suns is just 26 miles across.
00:55:40That's about the size of Oklahoma City.
00:55:45Such an enormous mass and a small volume creates a very sharp increase in gravitational tidal forces as you approach the black hole.
00:55:54With a small black hole, the strength of gravity changes so rapidly with distance that your feet could be pulled a million times harder than your head.
00:56:03But with supermassive black holes, that doesn't happen.
00:56:08The mass of a stellar mass black hole is concentrated in a small area.
00:56:13A supermassive black hole's mass spreads much wider, over an area a billion times larger.
00:56:19So, its gravity increases gently as you get closer.
00:56:22This means approaching a supermassive black hole feels more like walking down a slope rather than jumping off a cliff.
00:56:31So, it won't rip you to shreds.
00:56:34Supermassive black holes have a bad reputation.
00:56:38That bad reputation firmly belongs to stellar mass black holes that rips things to shreds.
00:56:44The nice thing about supermassive black holes is these so-called tidal forces are much weaker.
00:56:48So, I would actually be just fine and be able to take in this really bizarre scenery around a black hole with light from distant objects being bent out of shape.
00:56:59So, we can approach M87 star safely.
00:57:03Once there, we are faced with an awe-inspiring sight.
00:57:08The supermassive black hole distorts the light around it.
00:57:14Far away from the black hole, that warping isn't very strong.
00:57:18But the closer the light gets to the black hole, the more severely its path is distorted.
00:57:24And the starlight around the black hole becomes really bizarre.
00:57:28They get stretched into rings and arcs.
00:57:31We can even see things hidden behind the supermassive black hole.
00:57:35I would see, for example, the galaxy behind here looking completely warped out of shape because light is bent around the black hole.
00:57:44Black holes can even bend light.
00:57:47So, it comes from my face, goes around, and comes back on the other side.
00:57:52So, I could in principle use a black hole, you know, as a mirror when shaving.
00:57:55To really understand what's happening around a black hole, we need to understand gravity and the language of gravity is the language of space-time.
00:58:09Space-time binds the whole universe together.
00:58:12If we could put on special space-time glasses, we'd see stars, planets, and galaxies floating on a grid of space-time.
00:58:23These objects have mass, and mass distorts and curves space-time.
00:58:29Imagine a trapeze artist with a flat net underneath them.
00:58:34When they fall from the trapeze onto that net, the net distorts.
00:58:37It forms a dimple right where that trapeze artist is.
00:58:41The trapeze artist is like a black hole.
00:58:44The net is like the fabric of space and time, distorting because of the mass in it.
00:58:50This distortion of the space-time net by objects with mass is called gravity.
00:58:57The more massive you are, the more gravity you have because the more you bend and stretch space-time.
00:59:04So one trapeze artist may bend the net a little bit, but a hundred trapeze artists will bend that net a lot.
00:59:12And good luck trying to walk across it.
00:59:17M87 star's immense gravity bends space, forcing light to travel along the curves.
00:59:23But what does it do to the other half of the equation?
00:59:30Time.
00:59:32Einstein realized that time actually runs slower near a black hole than back on Earth.
00:59:37It's a process called gravitational time dilation.
00:59:43Viewed from a distance, our ship appears to move in slow motion.
00:59:48But what do we see on board the craft as we approach M87 star?
00:59:54You would perceive time to proceed on normally.
00:59:58You'd look at your watch and that second hand would be going around the dial just like normal.
01:00:02But to an outside observer, that apparent one minute on your watch could take millions to even billions of years.
01:00:09If I'm having a Zoom conversation with mommy back home, even though I'm feeling I'm speaking normally,
01:00:14she would hear me go, hi, mommy.
01:00:20And this is not some sort of illusion.
01:00:22My time really is going slower.
01:00:24So when I come home, she'd be like, hey, Max, you look so good.
01:00:26You look so youthful.
01:00:28And I would actually have aged less because time ran slower over there.
01:00:35On our final approach into M87 star, we reach a crucial milestone.
01:00:41We are now at the innermost stable orbit.
01:00:44We go any further, we're not getting out ever.
01:00:47You have two choices.
01:00:48You either escape to safety or you fall into the black hole.
01:00:57Well, that's easy.
01:00:59We detach the probe to approach the black hole alone.
01:01:07You can think of the event horizon as being the surface of a black hole,
01:01:10but that's a little bit of a misconception.
01:01:12There's not actually anything there.
01:01:13That's just the distance from the center where the escape velocity is the speed of light.
01:01:21Because nothing can travel faster than light, nothing can escape a black hole.
01:01:27Think of the event horizon as a waterfall.
01:01:30If you imagine the flow of water over a waterfall, if you're a fish, you can swim up close to that edge and still escape.
01:01:40But if you go too far, you hit the point of no return and you're going over.
01:01:44At the event horizon, the water moves faster than the fish can swim or our probe can orbit.
01:01:54So the waterfall, or gravity, carries them over and into the black hole.
01:02:00But what about the light around them?
01:02:02Imagine that fish that's going over the waterfall is carrying a flashlight.
01:02:09Say it's an alien fish.
01:02:11At a black hole, if that fish goes over that event horizon, not only does the fish and the flashlight get sucked in,
01:02:19but the light of the flashlight gets sucked in.
01:02:21There's nothing that can turn around.
01:02:25Light, matter, cows, elephants, that passes through the event horizon can never come back out.
01:02:31It is a one-way ticket.
01:02:33A one-way ticket through the event horizon.
01:02:37Back on the ship, though, we don't see the probe enter the supermassive black hole.
01:02:41Instead, from our perspective, the probe just gets slower and slower and slower and slower.
01:02:54Until it appears that time simply stops for the probe, frozen by the enormous gravity of M87 star.
01:03:05The probe appears stuck, glued to the surface.
01:03:08But that's just our perspective.
01:03:11In reality, the probe has already crossed the event horizon and is inside the black hole.
01:03:20If only it was that simple.
01:03:22The two major theories that explain how the universe works don't work at the event horizon.
01:03:29General relativity says the probe enters the black hole.
01:03:33But quantum mechanics throws up some major hurdles.
01:03:38According to some ideas rooted in quantum mechanics, there may be something called a firewall.
01:03:45A wall of quantum energies that prevents material from actually reaching through the event horizon.
01:03:51The question of what happens to anything attempting to cross the event horizon has challenged some of the greatest minds in physics.
01:04:02Will our probe enter the supermassive black hole?
01:04:07Or will it be burnt to a crisp in a wall of fire?
01:04:10Or will it be burnt to a crisp in a wall of fire?
01:04:14Our probe is approaching the event horizon of M87 star.
01:04:15But there's a problem.
01:04:16The two major theories that explain how the universe works don't agree about what happens next.
01:04:17The two major theories that explain how the universe works don't agree about what happens next.
01:04:18One says the probe passes through unscathed.
01:04:19The two major theories that explain how the universe works don't agree about what happens next.
01:04:21One says the probe passes through unscathed.
01:04:22The other theory says that it's impossible.
01:04:27It's a big problem.
01:04:29The two major theories that explain how the universe works don't agree about what happens next.
01:04:33One says the probe passes through unscathed.
01:04:35The other theory says that's impossible.
01:04:41It suggests that the probe passes through unscathed.
01:04:44The other theory says that it's impossible.
01:04:46unscathed. The other theory says that's impossible. It suggests the probe hits an
01:04:53impenetrable barrier called a firewall. How can the same event have two different outcomes?
01:05:02There's a really interesting puzzle right now, which is where general relativity and quantum
01:05:07mechanics meet, and it's called the black hole information paradox. What we have is this very
01:05:13schizophrenic situation in physics, where we have two theories that just don't get along.
01:05:19Einstein's theory of gravity explains all the big stuff. Quantum field theory explains all the small
01:05:25stuff. So which one is right and which one is wrong? This is the mystery. General relativity says in
01:05:34theory, crossing the event horizon is no big deal. If you're passing through the event horizon,
01:05:40you wouldn't notice anything different. You can in fact cross the event horizon of a black hole like
01:05:49M87 star in your spaceship without even knowing that you have. Nothing would change. You just
01:05:55peacefully drift inside. According to general relativity, our probe crosses the event horizon
01:06:04and enters the black hole. Quantum mechanics sees it differently. When it looks at the probe,
01:06:12it doesn't see a robotic spacecraft. It sees information. Everything at a quantum mechanical
01:06:20level has information. You can think of things like a particle having a charge. Particles have spin,
01:06:25angular momentum. And that information, as far as we understand, can't be destroyed.
01:06:30What do we mean by destroyed? Well, think of burning a book. The words are information. As each page
01:06:42burns, the words disappear. The information's gone, but not really. If you could track every single
01:06:50thing that was happening, track each smoke particle, put everything back together again,
01:06:55in principle, that information is still there. Because information can't be destroyed. The probe's
01:07:03information, even if mangled, should be inside the supermassive black hole. If the information
01:07:11that fell into a black hole just stayed locked inside of a black hole, that'd be fine. That doesn't
01:07:16violate any physics. But Stephen Hawking threw a wrench in the works when he theorized that over time,
01:07:24black holes evaporate. Slowly shrinking, particle by particle, emitting heat, known as Hawking radiation.
01:07:36Hawking radiation itself doesn't carry any information out. And Hawking radiation eventually destroys a black
01:07:44hole. Eventually the black hole evaporates and disappears.
01:07:47As the black hole vanishes, so too does information about the probe. This is a big problem for quantum
01:07:56mechanics. Can black holes really destroy information, even though quantum physics suggests you cannot?
01:08:06So is the foundation of quantum mechanics wrong? This is the quantum information paradox.
01:08:13To try to prevent this impossible situation, scientists came up with a workaround. Something
01:08:21that prevents the probe's information from ever entering the black hole. The firewall.
01:08:27Quantum mechanics says that there's this quantum fuzz causing there to be ridiculously high temperatures
01:08:37literally burning you up as soon as you enter. If the firewall incinerates the probe, then its
01:08:44information will stay in the ashes of the ship. Just like the words from the burning book.
01:08:54So which theory is right? Does the probe safely enter the black hole? Or does the probe burn up?
01:09:02I've actually spent an afternoon at Caltech arguing with people about whether anything falls into a
01:09:09black hole or not. And the answer is we don't really know.
01:09:14To find an answer, scientists have come up with some crazy ideas.
01:09:21One called quantum entanglement suggests that the probe is both inside and outside the black hole.
01:09:28It's information carried by particles constantly popping up on either side of the event horizon.
01:09:38And Stephen Hawking, whose original idea that black holes lose information through heat, also came up with a solution.
01:09:46He suggested that black holes have soft hair. Traditional black hole science says they're bald.
01:09:54By which we mean that they have no features at all except their mass and their charge and their spin that you can measure from outside.
01:10:03Hawking's updated theory says that black hole hair is made from ghostly quantum particles which store information.
01:10:13Thermal radiation from the evaporating black hole carries this information away from the event horizon.
01:10:19If Hawking is right, the probe's information will eventually escape into the universe.
01:10:29The concept of black hole hair would solve the black hole information paradox if it exists.
01:10:37But we don't know if black holes have hair or if they're, you know, bald.
01:10:41Until we can unite quantum mechanics and general relativity at the event horizon,
01:10:50the information paradox will remain a problem for physicists.
01:10:56It's one of the most embarrassing problems in physics which is still unsolved.
01:11:00I hope one of you who watches this will become a physicist
01:11:04and solve it for us because physics is far from done.
01:11:13The failure to solve the black hole information paradox
01:11:17throws up a major obstacle to our understanding of how our universe works.
01:11:24This is the point where physics hits a wall.
01:11:27While a search for a solution continues, let's assume our probe dodges its way past the information paradox.
01:11:38It sails across the event horizon towards one of the most violent places in the universe,
01:11:44the core of M87 star.
01:11:47It's called the singularity.
01:11:53And there are no rules.
01:11:55Nothing makes sense.
01:11:58And nothing escapes.
01:12:00Our probe has crossed the event horizon.
01:12:17It's on a one-way trip to the heart of the supermassive black hole M87 star.
01:12:25Anything that crosses the event horizon is not coming out.
01:12:29It's like Vegas.
01:12:30What goes in a black hole stays in a black hole.
01:12:34The probe leaves the physics we understand and enters the world of physics we do not.
01:12:43This probe is now moving faster than light or being carried by space itself faster than light.
01:12:49Once you cross the event horizon of a black hole,
01:12:53your future lies on the singularity in the center of the black hole.
01:12:57There's no escaping the fact that you will eventually join the singularity.
01:13:03The space inside of a black hole is like a 3D spinning vortex.
01:13:08The space in there is always moving.
01:13:10This is the nightmare version of the carousel ride.
01:13:14The whirling probe hurdles downwards until it hits an even more bizarre region of the black hole.
01:13:25The inner event horizon.
01:13:27You thought the firewall was bad, but that's peanuts compared to the inner event horizon.
01:13:33Theoretical physicist Andrew Hamilton believes that all light and matter that's fallen into a black hole
01:13:39piles up in a tremendous collision at this location.
01:13:42The inner event horizon would be infinitely violent because it's like the meeting point between two universes.
01:13:50This meeting point is like water falling and smashing into spray, shooting back up from the rocks at the base of the falls.
01:14:03Inside the supermassive black hole, space races in and crashes into rebounding space at the inner event horizon.
01:14:11This would be a place of infinite energy.
01:14:15It's a place where in-falling material into the black hole meets out-flowing material.
01:14:21Everything falling into M87 star smashes together in a monumental release of energy.
01:14:30This energy has got to go somewhere.
01:14:34It's possible that this inner event horizon is so energetic that brand new universes could be born in this space.
01:14:45But the question is, how do you actually sort of birth a new baby universe?
01:14:49The energy created at the inner event horizon could compress down into one tiny speck which suddenly ignites.
01:15:03Sparking baby universes into life.
01:15:08In their very own big bangs.
01:15:13We know that a long time ago our own universe was very small, very hot and very dense.
01:15:20It's possible that it could have been born in the inner event horizon of a spinning black hole.
01:15:27This is such a tantalizing and very hypothetical idea.
01:15:33But if it's correct, it gives us insights into the origins of our universe itself.
01:15:39Do we have strong evidence that black holes create baby universes?
01:15:45No.
01:15:46Do we have strong evidence that they don't?
01:15:49No.
01:15:52If the probe survives the inner event horizon, it then heads towards the strangest place in the universe.
01:15:59As the probe gets closer and closer to the singularity, the probe gets further and further away from known physics.
01:16:14We don't know what the probe will encounter when it reaches the singularity.
01:16:20We don't know what it will find.
01:16:21We don't know what it will experience.
01:16:24We don't know.
01:16:25In other words, there's a lot we don't know.
01:16:31Like, what exactly is the singularity?
01:16:35It's a hard question to answer.
01:16:37Traditional science says it's an infinitely tiny point.
01:16:42But that's not the case with M87 star.
01:16:46What's interesting is that if your black hole is spinning, the singularity is not a point, but it's in fact a ring.
01:16:53Physics says the singularity is infinitely dense.
01:16:59A point of space and time that is collapsed as far as it will go.
01:17:02It basically has infinite density in zero size.
01:17:07For many scientists, that's a big problem.
01:17:11I do not like singularities.
01:17:16I feel that they sound really unphysical.
01:17:22The word singularity sounds so intimidating and scientific, but it's honestly just our physicists'
01:17:28code word for, uh, we have no clue what we're talking about.
01:17:32Where else in nature do we find infinities?
01:17:36We're talking about a region that would have infinite density and infinitely small volume.
01:17:43Basically zero volume.
01:17:45How could that exist?
01:17:46I just don't see it.
01:17:47We just don't know.
01:17:48And frankly, we will never know for sure.
01:17:50Perhaps the probe breaks up and joins material consumed by M87 star over billions of years.
01:18:02Compressed down, not just to atoms, but to a sea of energy.
01:18:07Or there could be another possibility.
01:18:21Maybe the singularity doesn't destroy the probe at all.
01:18:26Maybe the probe travels straight on through and passes into another universe.
01:18:44Or there could be another one.
01:18:46Our voyage to the heart of M87 star has been a wild ride.
01:18:53We crossed the event horizon and fell towards the singularity.
01:18:57The core of the supermassive black hole.
01:19:03Is this the end of our journey or just the beginning?
01:19:08It could be that the singularity isn't the end point of the probe's journey.
01:19:13It could be that the probe passes through the singularity and enters into a new universe.
01:19:22Our probe has another option.
01:19:25An escape route out of M87 star.
01:19:30In our universe, we have black holes.
01:19:32Objects where if you enter, you can't escape.
01:19:36It's also theoretically possible for there to be white holes.
01:19:40Objects that you can't enter, you can only escape from.
01:19:45A white hole is basically a black hole running backwards.
01:19:51Some physicists have theorized that white holes may link to the singularities of black holes.
01:19:57Connected by something called a wormhole.
01:20:03There have been interesting papers written suggesting that you could have a wormhole where
01:20:07something that falls into a black hole here comes out of a white hole somewhere else.
01:20:13It sounds like a great way for the probe to escape certain death.
01:20:17Theoretically.
01:20:19A wormhole is the bridge in space-time between those two things.
01:20:23It's easy to create in mathematics.
01:20:25It very well might not exist in real life and will almost certainly live out on our entire civilization and never know about it.
01:20:34That's because constructing a bridge between a black hole and a white hole creates a few issues.
01:20:40A, we don't know how to build them for sure.
01:20:43B, they might be unstable and collapse on themselves immediately unless you have some new weird sort of matter that can support them.
01:20:50The problem is that it's hard to maintain this bridge open.
01:20:55It's not likely that they would ever have any practical use because they're just not stable.
01:21:00But if M87 star does have a stable wormhole linked to its singularity, where might our probe end up?
01:21:13It could be that this probe's journey doesn't end at the singularity.
01:21:18And all the information that it carries with it could be deposited in some distant corner of our own universe.
01:21:26Or perhaps in a different universe.
01:21:31One idea that sounded like science fiction decades ago is actually now considered potential reality.
01:21:38And that's the idea of parallel universes.
01:21:42If parallel universes exist, then some surmise that a black hole could be a gateway to a parallel universe.
01:21:50If there are parallel universes, who knows which one our probe may end up in?
01:21:57This universe may be just like our own, or it might be something completely different.
01:22:05We'll never get to find out unless we follow in after it.
01:22:11It could all work out just fine and that probe just sails on through and gets to explore new adventures.
01:22:19We don't know, only the probe knows.
01:22:27Supermassive black holes are some of the strangest and most fascinating objects in the universe.
01:22:34Ever since Einstein's theory of relativity predicted black holes a century ago,
01:22:40we've been trying to understand how they work.
01:22:43The photograph of M87 star confirmed many theories.
01:22:49But there's still much to learn about the birth, life, and death of these remarkable objects.
01:22:58And even more to leave us fascinated.
01:23:02This is the ultimate unknown.
01:23:03This is the real wild west.
01:23:05This is the frontier of human knowledge.
01:23:11I care about supermassive black holes first and foremost because they are awesome.
01:23:17They stimulate my childhood imagination and fascination.
01:23:23Supermassive black holes offer us a truly unique window into how the laws of physics work,
01:23:29especially the laws of gravity, in extreme regimes far beyond anything that we can possibly imagine here on Earth.
01:23:36Supermassive black holes lurk at the heart of almost every large galaxy that we know of.
01:23:42So in some way, we're just sort of all along for the ride with the supermassive black holes.
01:23:47If I could make a request for one special favor I would get before I die,
01:23:56what I would like to do is to just spend a few hours orbiting the monster black hole in the middle of the galaxy.
01:24:04What a way to go.