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00:00Supermassive black holes, the engines that power our universe.
00:11Supermassive black holes are one of the major players in the evolution of galaxies.
00:18With no supermassive black holes, you have no Milky Way galaxy, no sun, no earth, no
00:22you.
00:25They're the driving force at the heart of nearly every galaxy in the cosmos.
00:31They're the most monstrous and scary and bizarre aspects of our world, which just fascinates
00:36me.
00:37Now, a new mystery has emerged about the oldest supermassive black holes.
00:44We see supermassive black holes in the very early universe, and we don't understand how
00:49they grew so large so quickly.
00:52We have clues about their formation, but can we solve the mystery of this supermassive
00:58growth spurt?
01:032017, scientists gazing deep into the distant universe discover something completely unexpected.
01:25A vast supermassive black hole, dating from the earliest days of the universe.
01:32This was 690 million years after the Big Bang.
01:36The universe was about five or six percent of the age that it is now.
01:43Finding a supermassive black hole in the early universe is like finding an NFL defensive
01:48lineman playing in peewee football.
01:52Something that big shouldn't exist that young.
01:56The supermassive black hole wasn't just super early.
02:01It was super big, 800 million times the mass of our sun.
02:07In just a few hundred million years, the universe has somehow been able to collapse nearly a
02:12billion suns worth of material into a giant black hole.
02:16And we honestly just don't know how that's possible.
02:19We measure black holes by the mass of our sun, solar masses.
02:24Regular or stellar black holes are a few to a hundred solar masses.
02:30Supermassive black holes weigh from 100,000 to billions of suns.
02:36And scientists have now found over 100 of these monsters in the early universe.
02:43We were shocked to find even one of them existing so early after the Big Bang.
02:48It was kind of freakish, to be honest.
02:51But then to find that there's whole populations of these things that exist and are well in
02:55place at the earliest times that we can look at was truly shocking.
03:01We believe supermassive black holes might help explain the evolution and the destiny
03:06of the universe.
03:08Astronomers are striving to understand them.
03:12Understanding the origin of supermassive black holes and how they could form so early in
03:17the universe's history is something that would change all of astronomy and astrophysics.
03:25How do you get something that massive to form in such a short amount of time?
03:31It's a big question.
03:33To begin to answer it, we have to start small by asking how regular stellar black holes
03:39form.
03:41Black holes form through the collapse of stars.
03:44Everyone knows that.
03:45You have a big enough star and it'll collapse to form a black hole.
03:51A really massive star dies in a violent supernova explosion, and if they have sufficient mass,
03:57what's left over collapses into a black hole.
04:05The bigger the star was, the bigger the black hole is to start with.
04:10Were the stars of the early universe big enough to collapse into supermassive black holes?
04:17The very early universe was much different than the universe you see around us today.
04:22It was filled entirely with hydrogen and helium gas.
04:27This gas amassed into giant clouds, which collapsed under their own gravity.
04:34Their fusion ignited the dense cores, and the first stars were born.
04:41Now we think that these earliest clouds of gas probably made bigger stars than clouds
04:46of gas do in our local or today's universe.
04:49It was possible to get huge, giant stars that we call population three stars that were just
04:56utterly massive.
04:59Population three stars are the oldest category of star.
05:03Like stellar dinosaurs, they dominated the universe a long time ago.
05:07Now they're extinct.
05:09They'd be weird stars.
05:11They would be incredibly bright in the ultraviolet and have very unique signatures that are very
05:17different from stars today.
05:19But precisely because they're so big and so bright, they would be very short-lived.
05:23These first stars lived fast and died young.
05:31They were born in supernovas, leaving behind black holes.
05:37But were they supermassive black holes?
05:41When a star blows up, when it goes supernova, most of the mass is ejected away.
05:45It just goes flying out, leaving a dense neutron star or perhaps a black hole.
05:51But it won't have much mass because most of that mass was blown away.
05:57Even though population three stars in the infant universe were very large, they weren't
06:02big enough to leave a supermassive black hole behind when they exploded.
06:08Perhaps if we can skip the supernova step, that might be one pathway to understanding
06:14how supermassive black holes formed.
06:16Could a dying star's entire mass collapse into a black hole?
06:22A clue may lie in a galaxy nicknamed the Fireworks Galaxy.
06:27The Fireworks Galaxy has that flashy name because when you look at it, there are all
06:32these supernova explosions going off and making quite a show.
06:40Recently, astronomers were keeping an eye on one extremely bright star in the Fireworks
06:48Galaxy.
06:50This star is exactly the kind that we know explodes as a supernova.
06:55Astronomers expected it to explode, but then it did something even weirder.
07:01Astronomy is so wonderful because sometimes you see things right in front of your eyes
07:04that you can't explain.
07:06We saw an entire star just disappear.
07:09In 2007, the star looked like this.
07:13By 2015, it had completely vanished.
07:19There was no flare or debris from a supernova explosion.
07:23So what the heck is going on?
07:27It turns out that not every massive star blows up with all the fireworks of a normal supernova.
07:33You can get what's called a failed supernova.
07:36A supernova fails when the shockwave generated inside a collapsing star can't escape.
07:43In some cases when the star is very massive, the shockwave never has a chance to get all
07:47the way out of the star by the time the star itself collapses into a black hole.
07:52Then you have a failed supernova.
07:55The Fireworks Galaxy star may have been massive enough to smother its own explosion before
08:01collapsing to form a black hole.
08:05Everything collapses into the black hole.
08:07You can actually have a black hole with all the mass of the original star.
08:12Back in the early universe, could the enormous Population III stars have died as failed
08:17supernovas, leaving behind supermassive black holes?
08:23These Population III stars don't seem to me to be a good contender for the precursor to
08:30supermassive black holes.
08:31They just would not have enough mass.
08:34Even the most massive stars are only a couple of hundred times more massive than our sun.
08:39Whereas a supermassive black hole is millions or billions of times the mass of our sun.
08:45Early supermassive black holes can't have formed from collapsing stars.
08:50Even giant stars aren't massive enough.
08:53So is there some other path to being supermassive?
08:57Or stellar black holes?
08:59Cosmic bodybuilders on a fast track bulking program?
09:09How did supermassive black holes in the early universe get so large so quickly?
09:16We ruled out the idea that they were created from the collapse of very large stars.
09:21Eventually they started out as smaller stellar mass black holes and grew to be supermassive
09:28by eating.
09:30Black holes are not fussy eaters.
09:32They'll consume anything that comes in their path, you know, gas, planets, stars, it doesn't
09:37matter.
09:38And everything that they consume adds mass to the black hole.
09:43We've spotted a stellar mass black hole currently eating in our Milky Way galaxy.
09:50Fifteen times the mass of the sun, Cygnus X-1 is steadily feeding off the material that
09:56swirls around it.
09:58Some black holes are fed through things called accretion disks.
10:03It's kind of like the rings around Saturn.
10:06There's this thick or thin disk of material around the black hole that feeds it.
10:12Cygnus X-1's accretion disk gets constant refills from a nearby source.
10:18A vast star, 20 times the mass of the sun, called a blue supergiant.
10:25The black hole has been feeding on gas from this star for about 5 million years.
10:32So if you ask how do black holes eat or consume gas, the answer is gravity.
10:36These are very massive objects and anything that comes within their sphere of influence
10:41can be consumed by the black hole.
10:44The more mass a black hole gains, the greater its gravity and the more food it attracts.
10:51A black hole growing is a little bit like a snowball rolling down a hill.
10:55The bigger the snowball gets, the more snow it can accumulate and so the bigger it gets.
10:59It's a runaway effect.
11:02But even if Cygnus X-1 follows this runaway growth trajectory, it still may never reach
11:08supermassive status.
11:12The black holes of the early universe must have fed at a much faster rate.
11:18The biggest issue is how do you have enough time in the early universe to go from a small
11:26black hole that's born from a star to something that's supermassive.
11:33GRS-1915 is another stellar mass black hole.
11:39It's a greedy eater, accreting at up to 40 times the rate of Cygnus X-1.
11:46And when something gobbles food that quickly, it can begin to overheat.
11:52The black hole is accreting a lot of material and as it's eating, the accretion disk really
11:57heats up to very high temperatures.
12:00And at those high temperatures, you can get a lot of light coming out of the system.
12:05So the more material that a black hole eats and swallows, the brighter it shines.
12:11This stellar black hole sometimes eats so much, so quickly, it's accretion disk pushes
12:17out radiation almost a million times brighter than our sun.
12:23But this brightness has a serious consequence.
12:27It stops the black hole from eating and growing larger.
12:31If you wanted me to gain as much mass as possible as quickly as possible, you would
12:35just keep feeding me hamburgers nonstop or whatever.
12:40But black holes have a problem that when they eat a lot, they tend to just gobble up a lot
12:46of the food in their neighborhood and then also they start shining out so much stuff
12:50that it pushes away much of the food.
12:53The brightness, or luminosity, gets so intense, it pushes away incoming material, a sort of
13:01safety valve called the Eddington limit.
13:04So in many ways, the Eddington rate could be a kind of a speed limit for the growth
13:08of black holes.
13:09It could be a governor that prevents black holes from growing even faster by just dumping
13:14more and more gas onto it.
13:16Eventually, you're going to hit that Eddington limit and that more gas that you're dumping
13:20on won't actually reach the black hole.
13:24This cosmic method of portion control means that stellar black holes in the early universe
13:30couldn't have gained weight fast enough to become supermassive.
13:36Black holes need time to grow.
13:38They need to feed.
13:39They need to eat.
13:40Maybe you need to skip a few steps.
13:42Maybe you need to start at a medium size or bigger in order to get to supermassive by
13:49the time we observe it.
13:52So was there another type of black hole in the early universe?
13:56Something big enough to grow supermassive in the time available.
14:04In 2017, astronomers studied a dense star cluster called 47 Tucani on the outskirts
14:12of our own galaxy.
14:15They detected 25 pulsars, bodies that spin and emit radiation like cosmic lighthouses.
14:24These pulsars are all orbiting a central object.
14:28And even though we couldn't see the central object itself, we could watch the behavior
14:34in the orbits of all these pulsars around it and we could figure out how big that central
14:40object was.
14:41Well, when you do the math, you come up with something that is about 1,500 to 2,000 times
14:46the mass of the sun.
14:47It's actually hidden in the heart of that globular cluster.
14:51So what is the invisible object?
14:54Whatever is lurking at the center of 47 Tucani has to be big and it has to be black.
15:02Astronomers think it's a large black hole.
15:05At 1,500 times the mass of the sun, the object is much bigger than a regular stellar black
15:12hole, but too small to be supermassive.
15:16Could it be what's known as an intermediate mass black hole?
15:22It's extremely hard to find any of these intermediate mass black holes.
15:28This rare category of black hole ranges between 100 and 100,000 solar masses.
15:35At that size, they may have been large enough to become supermassive very quickly.
15:41Intermediate mass black holes could be what gives supermassive black holes a head start
15:46in life.
15:54Astronomers search for intermediate mass black holes.
15:58They may have been large enough to act as seeds for the first supermassive black holes.
16:04Yet so far, they've escaped discovery.
16:07They're like the missing link.
16:09And I mean that for real.
16:10They're missing.
16:11Imagine you're an alien who's arrived on the planet Earth and you know very little about
16:15the human species.
16:17And when you look around, you only notice tiny, tiny little children and grown adults.
16:22You don't see any adolescents, right?
16:25And intrinsically you know that the tiny little children grow up to be full-size adults, but
16:31you don't see how they got there, right?
16:34You don't see the intermediate stages of growth.
16:36That would be really, really weird, right?
16:38That is the case for supermassive black holes.
16:41So it's like a universe without teenagers.
16:44Or that's how it looked until September 2020.
16:49Scientists studying gravitational waves picked up the signal of an extreme event in the distant
16:55universe.
16:57What researchers are looking for are things called gravitational waves.
17:01They're like ripples in space itself.
17:04Most signals sound a little bit like a chirp.
17:07It's a noise that's very characteristic.
17:10It goes a bit like sort of whoop.
17:14But this particular event was so extreme and so sudden, it just sounded more like a thud.
17:21This faint thud from halfway across the universe is music to the ears of intermediate black
17:28hole hunters.
17:30Because its pitch can mean only one thing.
17:33This could only have been created by two really massive black holes colliding into each other
17:40and producing a combined black hole with a mass that's 142 times the mass of our sun.
17:49So that is, for the first time, getting into this intermediate mass black hole regime.
17:56This is the first confirmed observation of an intermediate black hole.
18:02Finding direct evidence like this for an intermediate mass black hole is absolutely fantastic.
18:09Now that we're certain intermediate black holes exist, could they help explain the origin
18:14of supermassive black holes in the early universe?
18:19These intermediate black holes really could be the first seeds of the supermassive black
18:24holes.
18:25You would need something like that to form really big, really early, to even begin to
18:30explain these very massive supermassive black holes that have formed just a short time after
18:36the Big Bang.
18:38How do intermediate black holes form in the first place?
18:42The recently discovered one came from the collision of two smaller black holes.
18:47They may also form in giant clouds of gas.
18:51It could be that in the earlier universe you can just have large clouds of gas that can
18:58lose enough energy quickly enough to just spontaneously collapse and form a black hole
19:05of this size.
19:07The enormous cloud of gas contracts and gets denser and denser the way it would if it was
19:12starting to form stars.
19:14But it's somehow able to remain coherent and collapse into one giant object that forms
19:19an intermediate mass black hole.
19:23A giant gas cloud undergoing a direct collapse down to an intermediate mass black hole would
19:29be a rare sight.
19:32You'd think it would go giant cloud, slowly collapsing black hole.
19:38But instead it's more like giant cloud, black hole.
19:44So one day you see this massive gas complex and then you blink and it's collapsed and
19:52now you're face to face with a big black hole.
19:55At least that's the theory.
19:58Getting a black hole to form from the direct collapse of a gas cloud is very tricky.
20:05Gas clouds tend to split up and collapse into a multitude of stars.
20:11Collapsing into one object would take unique conditions.
20:16One possible scenario involves two neighboring galaxies.
20:21The first, a young proto-galaxy, a gas cloud yet to form stars.
20:28Next door sits a larger galaxy.
20:32It's forming so many stars, radiation is bursting out all over its young neighbor.
20:38Because they're in close proximity, the energy from the large galaxy prevents the smaller
20:44galaxy from forming its stars.
20:46So that means that it'll continue to collapse in cloud form before moving to star formation.
20:54When a gas cloud becomes large and dense enough, the gravity eventually pulls it in
20:58on itself.
21:01When it can't ignite into stars, the collapse creates an intermediate mass black hole.
21:08I think this idea is very intriguing.
21:11I don't know if it's physically possible.
21:14But then again, there's a lot we don't know about the early universe.
21:18In 2017, scientists simulated another way that intermediate mass black holes might form
21:25in the infant universe, under the influence of dark matter.
21:33Dark matter was absolutely critical for the evolution of structure in the early universe.
21:39Without dark matter, there would be virtually nothing.
21:42Dark matter is mysterious.
21:45We know it has a gravitational pull on ordinary matter.
21:50One idea is that it helped form very large stars in the early universe.
21:56Stars that later collapsed into intermediate mass black holes.
22:01The idea is something like this.
22:03About 100 million years after the Big Bang, dark matter, which dominated the gravitational
22:08early universe, was forming big clumps.
22:11Then there might have been these supersonic streams of regular matter after the Big Bang,
22:15and they were directed into these gravitational cores where dark matter was gathering everything
22:19together.
22:22When scientists simulated this, they found that dark matter's strong gravity could pull
22:27in huge clouds of gas.
22:30You could actually accumulate as much as, say, 34,000 times the mass of the sun into
22:35one gigantic star-like object.
22:38If it's big enough, it would just collapse into a black hole.
22:42A black hole of 34,000 solar masses would sit squarely in the intermediate mass category.
22:50It would be large enough to potentially become a supermassive black hole.
22:55It's possible that dark matter directing streams of gas together about 100 million years after
23:00the Big Bang was the seed for these supermassive black holes.
23:06Whichever way intermediate mass black holes form, they seem like a good way to start explaining
23:12supermassive black holes in the early universe.
23:16The question is then, how do they grow?
23:18How do you start from this seed and end up, you know, with something that's a billion
23:22times the mass of the sun?
23:25Maybe early intermediate mass black holes had enormous appetites, gorging themselves
23:32to a supermassive state, feeding on the biggest meals our universe can serve up.
23:48Astronomers want to know how the earliest supermassive black holes got so big so quickly.
23:56Could they have started as intermediate mass black holes that devoured supersized meals?
24:04It's possible that these intermediate mass black holes could form in an exceptionally
24:09rare environment where it can accrete new material at an enormously high rate.
24:16So far, we only have direct evidence of one intermediate mass black hole, and we can't
24:22yet detect how it eats and grows.
24:26But we could look at much larger black holes for clues.
24:31In 2019, astronomers searched for supermassive black holes that are actively feeding.
24:38They pinpointed 12 quasars from the beginning of the cosmos.
24:43Quasars are among the brightest objects we know of in the universe, and they're what
24:47happens when a supermassive black hole at the center of a galaxy is swallowing up gas
24:53and dust, and that generates a tremendous amount of energy and luminosity that we can
24:57see.
24:58Surrounding these early galaxies are enormous gas reservoirs called hydrogen halos.
25:05This is great because that acts as fuel for those supermassive black holes.
25:10Cold gas can stream into those black holes and feed them.
25:14These huge halos of cold gas are also the building blocks of stars.
25:20These enormous, pristine halos of hydrogen around early galaxies, they're going to be
25:25reservoirs to power star formation.
25:30Star formation is a violent process that can create turbulence in a galaxy.
25:36That turbulence makes the gas fall toward the black hole, and then that makes the black
25:40hole even bigger.
25:43Hydrogen halos might have spoon-fed early supermassive black holes.
25:49This process may have also helped intermediate-mass black holes grow quickly.
25:56Could the largest black holes show us other, more drastic ways to put on weight?
26:04In October 2019, astronomers used telescopes to explore a remarkably clear galaxy called
26:11M77.
26:14Because this galaxy is so near to us, we can study its central engine in really exquisite
26:20detail at very, very fine resolution.
26:23Not only do you see the bright core, the bright nucleus, but you can see spiral arms.
26:28You can see structures in the galaxy.
26:31You can see how the whole galaxy is arranged.
26:35When we examined M77's central supermassive black hole, we saw something extraordinary.
26:41Its food was coming not from one, but two accretion disks spinning in opposite directions.
26:50Normally around a black hole, all of the gas is spinning in roughly the same direction,
26:54and that creates kind of a slow infall of gas and slow feeding.
26:58Here we've got a case where some of it's going one way, the other's going the other way.
27:02This is very unstable and can create opportunities for lots of gas to get gobbled up by that
27:07black hole.
27:10The material in the disks is one enormous, ready-to-eat meal.
27:16But dinner will not be served until the outer disk slows down.
27:20If there's a black hole at the center of a galaxy and you're orbiting around it fast
27:24enough to maintain your orbit, you're never going to fall in.
27:28You're just going to orbit forever and you're just going to spin around, just like the way
27:32the earth is going around the sun.
27:34What needs to happen if you want to fall in is to slow down your speed.
27:39The outer accretion disk will gradually slow down and orbit more tightly against the inner
27:44disk.
27:46Dangerous collisions of the counter-rotating material will start to occur.
27:51The double accretion disk is like drinking from two soda fountains at the same time.
27:56It's great while it lasts, but you're building up some serious gas that is just going to
28:00blow the whole thing away.
28:02In just a few hundred thousand years, the double disks will catastrophically collide
28:08and their entire contents will fall into the central supermassive black hole.
28:14That will devour everything in one gulp, generating a colossal cosmic burp.
28:27In February of 2020, in the Ophiuchus Galaxy Cluster, we saw the damage a cosmic burp can do.
28:37The Ophiuchus Galaxy Cluster is a collection of a huge number of galaxies all bound together
28:43by gravity.
28:44And there's gas in between these galaxies.
28:47And when astronomers looked at that gas in detail, what they found was a huge arcing
28:51structure in it that they realized was the edge of a cavity.
28:58There is a massive hole in the gas that is over 15 times bigger than the entire Milky
29:05Way Galaxy.
29:08Something frightening had to happen to carve this void out.
29:13The size of this bubble is kind of stomping my brain.
29:18We are talking about a hole in this gas that is over a million light years wide.
29:25The burp that created this cavity must have been astoundingly powerful.
29:30There are a lot of ideas about this, but there's only one that really can explain it.
29:35And that's a supermassive black hole.
29:38A supermassive black hole that suddenly got very greedy.
29:43In order to drive an energetic event like this, the black hole needs to eat.
29:49Not just one meal, it needs to eat thousands of meals at the exact same time.
29:56It needs to go to an all-you-can-eat intergalactic buffet.
30:01Sometime in the distant past, this black hole must have had a huge episode of just gorging
30:08on material falling in.
30:10It got super hot, blew out a tremendous amount of material in jets, beams that shot out from
30:16the poles of the disk.
30:18And that's what basically pushed its way out of that gas, forming this enormous cavity.
30:25The colossal cosmic burp pushed food far away from the supermassive black hole, ending its
30:31all-you-can-eat binge and stopping its growth.
30:35If an intermediate-mass black hole was this greedy, it would come to a similar end.
30:42It's no way to gain weight and become supermassive.
30:46This is probably not the way the earliest supermassive black holes grew to such enormous
30:51size.
30:52Is there another way supermassive black holes could have formed in the early universe without
30:57having to overeat?
31:00Maybe black holes smashed their way to being giant-sized.
31:17November 2018.
31:20Astronomers scanning hundreds of nearby galaxies in infrared light spot something extraordinary.
31:30Some galaxies had not one supermassive black hole, but two.
31:37Are these pairs a clue to how supermassive black holes in the infant universe got so
31:42big so fast?
31:46Seeing these infrared images showing pairs of supermassive black holes at the centers
31:51of galaxies and showing that this could be very common just is mind-blowing to me.
31:59The reason we see pairs of supermassive black holes is because two galaxies merge together.
32:06In our picture of how the universe works, galaxies start off as smaller galaxies and
32:12grow by merging with other galaxies.
32:15So they'll be whooshing around each other and tearing each other up.
32:20It's actually quite violent.
32:22When galaxies merge, we think their central supermassive black holes also merge, smashing
32:29into each other and combining to build a larger black hole.
32:34Galaxy scale mergers can be one of the most efficient growth mechanisms for supermassive
32:38black holes.
32:41Maybe in the early universe, black holes of stellar or intermediate mass merged repeatedly,
32:48getting heavier and heavier until they became supermassive.
32:55We don't really know how common supermassive black hole mergers were in the early universe,
33:00but we think they were more common than they are today because galaxies were closer together.
33:06It would have taken millions of mergers to build up the largest supermassive black holes
33:11we see today, which could have been a tall order.
33:21There's another problem too.
33:23We've never witnessed a supermassive black hole merger in the act.
33:27We've seen supermassive black holes on their way to merging, and we've seen ones that we
33:31think had gone through mergers, but we haven't caught one in the moment.
33:36As supermassive black holes start merging, they spiral around each other, getting faster
33:42and faster the closer they get.
33:46But for them to finally merge together into a single black hole, they need to lose what
33:52astronomers call orbital energy.
33:56The merger of supermassive black holes means that their orbits have to decay for them to
34:01get closer and closer together.
34:03So in order for an orbit to decay, that orbital energy has to go somewhere.
34:09To lose energy, the merging supermassive black holes start disrupting the orbits of nearby
34:15stars, throwing them off their paths.
34:19So something small and puny that weighs just one sun, like our own star, will often get
34:25in the path of these two and just get rocketed out, potentially unbound and flung out of
34:30the galaxy entirely.
34:33Each time the supermassive black holes fling out a star, they lose more orbital energy.
34:39They get closer and closer.
34:42But eventually they kicked out all the stars.
34:43There's nothing left.
34:45The merger stalls.
34:48Like two sweethearts at a high school prom, the supermassive black holes dance as close
34:54as they can, but physical contact is not allowed.
34:59So these two black holes could end up spiraling around each other for billions and billions
35:05of years.
35:06This is called the final parsec problem.
35:10In 1980, there was a famous paper which addressed this issue that supermassive black holes can
35:18only get to within about one parsec, or three light years of each other, before they can't
35:25merge or they stall.
35:28We believe that supermassive black holes must merge.
35:31We know that galaxies merge.
35:32And so if the black holes didn't merge, we'd see lots of black holes floating around.
35:36And we don't.
35:37There's always one in the middle.
35:38So how do they merge?
35:40In 2019, we found something that appears to solve the final parsec problem, a galaxy in
35:49the middle of a merger that contains not two supermassive black holes, but three.
35:56Three supermassive black holes.
35:58Now that's really cool.
35:59Sometimes you can have three galaxies that are merging together in a galaxy cluster.
36:05Then you have three supermassive black holes.
36:08At this point, it's virtually impossible for there to be a final parsec problem.
36:13Here's how a third black hole solves the final parsec problem.
36:18Two of the black holes orbit closer and closer, ejecting stars to lose energy.
36:25Black hole number three joins the action.
36:28Its gravitational pull takes even more energy from the orbiting pair.
36:34Eventually, they lose enough orbital energy to collide.
36:39That third supermassive black hole is just what's needed to transfer energy away from
36:45the two merging black holes so that they can now merge into one single supermassive black
36:50hole.
36:52Triple black hole events may explain how the earliest supermassive black holes grew to
36:58such enormous size.
37:00We've suspected that three black holes may be necessary in order to get black holes to
37:07merge, but we've never had any evidence for it.
37:11But now, this might provide a direct picture of three black holes caught in the act itself.
37:19If we have a picture of this happening now, then it certainly happened in the early universe
37:26and might explain how the biggest black holes got so big so quickly.
37:33Final proof will come when we witness a merger being completed.
37:39But tracking mergers as they happen is challenging.
37:43Supermassive black hole mergers can take billions of years, and therefore it's impossible to
37:48witness a supermassive black hole merger in action.
37:54Mergers may take an incredibly long time, but the actual moment the black holes join
37:59is very fast.
38:02Compared to the billions of years the black holes take to spiral together, they might
38:06merge together in a matter of minutes or hours.
38:10That means if we want to witness a merger happening, we have to watch the skies very
38:14carefully.
38:16No one has ever seen a supermassive black hole merger, but I imagine it would be an
38:22absolutely spectacular event.
38:26It's also possible that the merger is dark, that there's no fireworks, that there's nothing
38:32really special that happens in terms of light being emitted from the system.
38:37It could be a dark merger.
38:40Whether dark or bright, finally seeing a merger will help answer how the very first supermassive
38:46black holes got so big so quickly.
38:51We think that mergers of supermassive black holes in the early universe are one key way
38:56that galaxies and their black holes could have grown in the early universe.
39:00They're probably not the only way.
39:02There are other ways that black holes could grow as well.
39:06Scientists are also investigating invisible forces at the beginning of the universe.
39:11Did something we can't see boost the size of the first supermassive black holes?
39:18There's still so much we don't know about the early universe.
39:22The further out we look in the universe, the less familiar the universe becomes.
39:27And so the more and more interesting and new physics you need to involve in order to explain
39:36these very strange observations.
39:40The puzzle of fast-growing supermassive black holes in the infant universe now takes physicists
39:46somewhere new, to the little understood realm of magnetic fields.
39:52The thing about magnetic fields is they're hard.
39:55They're hard to calculate.
39:56They're hard to understand.
39:57They're sort of the elephant in the room for astronomers.
40:00We know they're there, but we'd really rather not talk about them.
40:04It's only recently that people are incorporating magnetic fields into their models of galaxy
40:09formation and therefore maybe it's under the influence of these fields that somehow these
40:15supermassive black holes are formed.
40:18To investigate how magnetic fields influenced early supermassive black holes, we must look
40:24back at the very beginning.
40:27Soon after the Big Bang, the first particles form, cool, and become electrically charged.
40:35Things were very different, radically different than they are now.
40:38Particles were whizzing by each other.
40:40Everything was charged.
40:41It was just a very different landscape.
40:43There are no stars yet, not even atoms.
40:47But some scientists think moving, charged particles created the first magnetic fields.
40:54Magnetic fields were essentially everywhere in the early universe.
40:57Those magnetic fields would have extended extremely large distances, like a very finely
41:02spun web all through the early universe.
41:07Gradually, atoms form and gather into clouds of gas.
41:12These will become the first galaxies and their supermassive black holes.
41:19During this time, magnetic fields change.
41:22They bunch together around the forming galaxies, but we don't know how.
41:28The thing with magnetic fields is they're extremely hard to predict and you need to
41:32do really hard calculations that even now we're only just starting to do.
41:38In 2017, scientists design a groundbreaking computer model that simulates patterns of
41:44magnetism developing over time.
41:48The images show lines of magnetic force getting stronger and more focused across a vast region
41:55of space.
41:56Some astronomers think these emerging magnetic field lines help shape early galaxies and
42:02the supermassive black holes at their cores.
42:07Magnetic fields have this ability to push material around, so one possibility is they
42:12could actually help push or funnel material in towards a growing black hole and help it
42:18grow faster than it would do otherwise.
42:21In today's universe, we know magnetic fields around planets can deflect dust particles.
42:29On much larger scales, matter may also have been channeled into the centers of galaxies
42:34of the early universe.
42:36With the magnetic fields of these early galaxies, it's a conduit that you could get matter dumped
42:40more and more into the middle and maybe build up a really big black hole.
42:46Scientists are just starting to figure out the effects of magnetism at the beginning
42:50of the universe, but it could have been one of several mechanisms that influenced the
42:55size of early supermassive black holes.
43:00We have lots of ideas for how you might be able to form supermassive black holes, but
43:05until we see actual mechanisms in action, we just can't really say which of them are
43:10the most important routes.
43:13Maybe some other mechanism we haven't even thought of explains how the early supermassive
43:18black holes got so big so fast.
43:22Hopefully, one day, these monsters of the cosmos will reveal their secrets to us.
43:30Supermassive black hole research is utterly mind-blowing to me.
43:33I mean, this is so cool.
43:35It's important to explain how these early supermassive black holes formed in order to
43:40have a really concrete understanding of how the universe works.
43:47Supermassive black holes are the great engines of cosmic change.
43:50They're enormous points of matter, and because they're just so massive, they can sculpt the
43:56evolution of galaxies.
43:58They're the master key to most of the unsolved mysteries in physics.
44:03We have a chance here to understand supermassive black holes so that we can understand the
44:08formation of galaxies, the generation of stars like our sun, and maybe even the appearance
44:13of life.