0:00:13 > 0:00:16Nothing is more seductive than the unknown.
0:00:21 > 0:00:23Nothing more compelling than a place of danger
0:00:23 > 0:00:26that lies beyond normal comprehension.
0:00:34 > 0:00:37Of all those places,
0:00:37 > 0:00:40perhaps the strangest of all
0:00:40 > 0:00:41are black holes.
0:00:49 > 0:00:51They are an exit point from the universe.
0:00:56 > 0:01:00Hidden trap doors in the fabric of space-time.
0:01:15 > 0:01:19What would it be like to enter the void
0:01:19 > 0:01:22and succumb to a black hole's dark mysteries?
0:01:34 > 0:01:37Now, for the first time,
0:01:37 > 0:01:41astronomers are set to find out.
0:01:43 > 0:01:48For the first time, the black hole at the centre of our very own galaxy
0:01:48 > 0:01:52is about to yield up its secrets.
0:02:07 > 0:02:12High above your head in the centre of our Milky Way Galaxy
0:02:12 > 0:02:15a violent drama is about to unfold.
0:02:23 > 0:02:28Our supermassive black hole is getting ready to have dinner,
0:02:30 > 0:02:33as a gas cloud three times the size of the Earth
0:02:33 > 0:02:37is caught in its gravitational hold.
0:02:38 > 0:02:43Across the world astronomers are getting ready to discover
0:02:43 > 0:02:47what happens when a black hole gets ready to feed.
0:02:51 > 0:02:56If you could see how something falls into a black hole,
0:02:56 > 0:02:59that would be something we can see for the very first time ever,
0:02:59 > 0:03:01that we see how a black hole starts getting fat.
0:03:01 > 0:03:03That would really be fantastic
0:03:03 > 0:03:06if we, if we can witness that in front of our eyes.
0:03:15 > 0:03:21For astronomers, this year's event is the first time in history
0:03:21 > 0:03:26it will be possible to witness and record the workings
0:03:26 > 0:03:30of one of these great gravitational engines.
0:03:36 > 0:03:37Some of the excitement
0:03:37 > 0:03:39is just childish pleasure
0:03:39 > 0:03:44in seeing something violent about to happen, and anticipating it.
0:03:44 > 0:03:50Scientifically it's very interesting because it's really unprecedented.
0:03:52 > 0:03:56This is the first time really in human history
0:03:56 > 0:04:00that we have not only known an event like this was going to happen
0:04:00 > 0:04:03but that we are prepared with the right sort of technology
0:04:03 > 0:04:06to see the details unfold.
0:04:11 > 0:04:15There's nothing anywhere near as extreme as a black hole.
0:04:18 > 0:04:20The disturbing truth about black holes
0:04:20 > 0:04:24is that they're a boundary between the known universe
0:04:24 > 0:04:29and a place that will forever lie beyond the reach of science.
0:04:31 > 0:04:34They are an anomaly of gravity so strange,
0:04:34 > 0:04:38it is barely possible to comprehend.
0:04:42 > 0:04:45Black holes represent
0:04:45 > 0:04:49the regions where our current theories of physics completely fail.
0:04:50 > 0:04:54What actually happens there, we don't know,
0:04:54 > 0:04:57so it's this very weird situation
0:04:57 > 0:05:03where our understanding kind of predicts its own failure.
0:05:10 > 0:05:11What gravity tells us
0:05:11 > 0:05:15is that everything at the centre of a black hole
0:05:15 > 0:05:18should get smashed together in a region
0:05:18 > 0:05:21smaller than even a proton or an electron
0:05:21 > 0:05:24or any kind of regular part of matter.
0:05:24 > 0:05:30If you were to fall inside what we call the radius of the black hole,
0:05:30 > 0:05:34the event horizon, then nothing could get out of that region.
0:05:36 > 0:05:40Once it's gone, it's gone for ever.
0:05:40 > 0:05:44The great dream for astronomers
0:05:44 > 0:05:46is to see those final moments
0:05:46 > 0:05:51as it falls over the edge into oblivion.
0:05:53 > 0:05:57The kind of ideal situation that we're aiming for
0:05:57 > 0:05:59is to really be able to see what happens
0:05:59 > 0:06:02very close to the event horizon of a black hole.
0:06:03 > 0:06:07This is not something we can do in a laboratory on Earth,
0:06:07 > 0:06:08so the only hope
0:06:08 > 0:06:12is to use observations of black holes in the universe
0:06:12 > 0:06:15to actually see what's happening,
0:06:15 > 0:06:17and that is kind of the Holy Grail
0:06:17 > 0:06:20of astronomical observations of black holes.
0:06:35 > 0:06:38But if watching matter tumble over the edge of a black hole
0:06:38 > 0:06:40might now be possible,
0:06:40 > 0:06:44it is only because of the efforts of a generation of astronomers
0:06:44 > 0:06:48to wrestle these dark dragons of the cosmos
0:06:48 > 0:06:51into the realms of scientific reality.
0:07:05 > 0:07:10As is often the case, it began with a series of observations
0:07:10 > 0:07:13that made no sense to anyone.
0:07:17 > 0:07:22A new generation of radio telescopes had come on stream in the 1950s
0:07:22 > 0:07:25that made it possible to see the universe
0:07:25 > 0:07:26in a completely different way.
0:07:32 > 0:07:37Almost immediately they began to detect a series of strange,
0:07:37 > 0:07:41previously unseen, sources of light.
0:07:43 > 0:07:45Nothing had ever been seen like them.
0:07:52 > 0:07:56These things looked very different, very strange,
0:07:56 > 0:07:59much more powerful, much larger and really different
0:07:59 > 0:08:04than sorts of galaxies and stars in our neighbourhood.
0:08:07 > 0:08:09But that was not the only surprise.
0:08:13 > 0:08:17People began to realise that these tiny star-like things,
0:08:17 > 0:08:18or they looked like stars,
0:08:18 > 0:08:22were actually putting out as much energy as a hundred galaxies
0:08:22 > 0:08:24and yet they didn't look like a galaxy at all.
0:08:26 > 0:08:33The paradox was how something so small could be so bright.
0:08:35 > 0:08:39What could possibly produce such a mind-boggling source of power,
0:08:39 > 0:08:44with some of them pumping out more energy than a trillion suns?
0:08:50 > 0:08:53They were given the name quasars.
0:08:55 > 0:08:59Quasars became a very big and deep mystery
0:08:59 > 0:09:02because they were distant in the universe
0:09:02 > 0:09:05and therefore we were seeing the universe
0:09:05 > 0:09:07as it was billions of years ago
0:09:07 > 0:09:09and they were more potent, more luminous
0:09:09 > 0:09:12than anything else that we'd come across before.
0:09:15 > 0:09:20Solving that mystery turned out to be the crucial step on the journey
0:09:20 > 0:09:25that would eventually lead to us observing the strange behaviour
0:09:25 > 0:09:28of our own feeding black hole.
0:09:31 > 0:09:36So that's twice times Newton's constant,
0:09:36 > 0:09:38onto the mass of the black hole
0:09:38 > 0:09:41and if you divide...
0:09:41 > 0:09:44What was first needed was a maverick insight
0:09:44 > 0:09:47from one of modern science's truly original thinkers.
0:09:49 > 0:09:54I was thinking about that mystery, that's absolutely true,
0:09:54 > 0:09:57and there were a number of different ideas that were put forward
0:09:57 > 0:09:59but none of them was terribly convincing.
0:10:02 > 0:10:06The mystery of what could account for the quasars' extraordinary brightness
0:10:06 > 0:10:10was THE hot topic in astronomy during the 1960s,
0:10:10 > 0:10:15as astronomers began to grapple with the new enigmatic objects
0:10:15 > 0:10:18that had been found by the radio telescopes.
0:10:18 > 0:10:22One astronomer keen to have a crack at the problem
0:10:22 > 0:10:26was a young researcher called Donald Lynden-Bell.
0:10:32 > 0:10:34The sky looked totally different
0:10:34 > 0:10:37in the radio than it looked in the optical,
0:10:37 > 0:10:40and that was a big problem,
0:10:40 > 0:10:45and the question was, what were these things?
0:10:48 > 0:10:51While his colleagues were staring down telescopes,
0:10:51 > 0:10:56Lynden-Bell approached the problem through theory.
0:10:59 > 0:11:03He wanted to find out how something as small as a quasar
0:11:03 > 0:11:06could possibly be so bright.
0:11:08 > 0:11:12This had an enormous quantity of energy coming out of it,
0:11:12 > 0:11:15and it came from a very small size.
0:11:15 > 0:11:18Now, putting those numbers together,
0:11:18 > 0:11:19one could already see
0:11:19 > 0:11:23the mass of the energy required to give the emission
0:11:23 > 0:11:29was, like, ten million times the mass of the sun.
0:11:34 > 0:11:38But the problem was that quasars are tiny in size,
0:11:38 > 0:11:41with nothing like the scale of ten million suns.
0:11:44 > 0:11:48Lynden-Bell realised that there was only one thing
0:11:48 > 0:11:53that could possibly be so small yet have so much mass,
0:11:53 > 0:11:58those mathematical anomalies conjured up by theorists
0:11:58 > 0:12:02that had been predicted but never observed:
0:12:05 > 0:12:07supermassive black holes.
0:12:12 > 0:12:14It suggested a baffling paradox,
0:12:14 > 0:12:18that quasars are really shining black holes
0:12:18 > 0:12:24capable of emitting the energy of entire galaxies.
0:12:27 > 0:12:30But Lynden-Bell then went further.
0:12:32 > 0:12:36I predicted that there would be these massive objects
0:12:36 > 0:12:38found in the nearby galaxies.
0:12:40 > 0:12:43He brought his ideas together with a bold conceptual leap
0:12:43 > 0:12:48about where these supermassive black holes would be found in the cosmos.
0:12:50 > 0:12:55Typically a large galaxy would have a black hole,
0:12:55 > 0:13:02the sort of amount of many millions of solar masses, in mass.
0:13:03 > 0:13:08And that these would typically reside in the middles of large galaxies.
0:13:08 > 0:13:10It was a pretty bold prediction.
0:13:11 > 0:13:14Yeah, well, I come from a military family!
0:13:19 > 0:13:25Lynden-Bell's hypothesis was so radical it seemed far-fetched.
0:13:26 > 0:13:31Inside the centre of every large galaxy in the universe
0:13:31 > 0:13:34lurks a supermassive black hole.
0:13:40 > 0:13:42If Lynden-Bell was right
0:13:42 > 0:13:47and every galaxy has a supermassive black hole at its centre,
0:13:47 > 0:13:50then there should be one right in our own back yard,
0:13:50 > 0:13:54in the middle of the hundreds of billions of stars
0:13:54 > 0:13:56that form our own galaxy, the Milky Way.
0:13:59 > 0:14:04The problem was trying to map our galaxy from the outside
0:14:04 > 0:14:06when we can only view it from within.
0:14:07 > 0:14:09Seeing round that obstacle
0:14:09 > 0:14:13would take ingenuity and some careful observations.
0:14:16 > 0:14:19One of the problems of living inside a galaxy like the Milky Way
0:14:19 > 0:14:21is that because we're inside it,
0:14:21 > 0:14:25it's really difficult for us to see what shape it is,
0:14:25 > 0:14:29how big it is, and where in it we actually live.
0:14:30 > 0:14:32But if you look carefully
0:14:32 > 0:14:37the stars aren't spread smoothly across the whole sky.
0:14:37 > 0:14:39They're gathered together
0:14:39 > 0:14:43into a band that loops around the sky which we call the Milky Way.
0:14:46 > 0:14:48That bright strip across the sky,
0:14:48 > 0:14:53with its extraordinary abundance of stars and clusters,
0:14:53 > 0:14:56was a clue to the nature of our galaxy.
0:14:58 > 0:15:01It was obvious to astronomers for quite a long time
0:15:01 > 0:15:07that most of the stars were gathered together into a flat layer or disc,
0:15:07 > 0:15:10and that we were within that disc.
0:15:12 > 0:15:16But we still don't know whereabouts in the galaxy we are.
0:15:19 > 0:15:21And then in the early 20th century,
0:15:21 > 0:15:23an American astronomer called Harlow Shapley
0:15:23 > 0:15:25hit on a way of trying to find out
0:15:25 > 0:15:27where the centre of the galaxy might be.
0:15:32 > 0:15:34He used objects called globular clusters
0:15:34 > 0:15:38which are actually found all over the sky.
0:15:38 > 0:15:41Bright sources containing thousands of stars,
0:15:41 > 0:15:43globular clusters,
0:15:43 > 0:15:48are spread out in a sphere around the Milky Way's central disc.
0:15:50 > 0:15:54Shapley realised they were in effect signposts
0:15:54 > 0:15:57to where the centre of the galaxy could be found.
0:15:59 > 0:16:01He plotted where the clusters were
0:16:01 > 0:16:04and he found that although they were spread all over the sky,
0:16:04 > 0:16:08they were concentrated in a particular direction.
0:16:11 > 0:16:16And that told us that we weren't at the centre of the galaxy,
0:16:16 > 0:16:19but the centre of the galaxy was in this direction here.
0:16:21 > 0:16:23So at last
0:16:23 > 0:16:27astronomers knew exactly where the centre of the galaxy was,
0:16:27 > 0:16:30and they also knew pretty much how far away it was.
0:16:32 > 0:16:37At last astronomers had a map of our galaxy.
0:16:39 > 0:16:41A panorama of the Milky Way
0:16:41 > 0:16:45it would never be possible to see from planet Earth.
0:16:48 > 0:16:5427,000 light years from our solar system is the centre of our galaxy.
0:16:58 > 0:17:00If we were ever going to have a chance
0:17:00 > 0:17:03of seeing a black hole at close range,
0:17:03 > 0:17:08according to theory, it should be hiding right here.
0:17:23 > 0:17:29Theory is one thing but astronomers work by observation and proof.
0:17:30 > 0:17:35That would mean actually finding the black hole and seeing it at work.
0:17:38 > 0:17:42The good news is that there should be a supermassive black hole
0:17:42 > 0:17:44somewhere at the centre of the Milky Way Galaxy.
0:17:46 > 0:17:50It's not that far from us and we know exactly where to look.
0:17:50 > 0:17:54We know where to point our telescopes.
0:17:54 > 0:17:57The bad news is that the centre of our galaxy
0:17:57 > 0:17:59is an incredibly crowded and busy place.
0:18:03 > 0:18:06Many, many stars... Stars are packed much more densely
0:18:06 > 0:18:09than they are where we live in the Milky Way Galaxy.
0:18:09 > 0:18:13It's this incredibly confusing and noisy environment.
0:18:15 > 0:18:18The stars around the centre of the Milky Way
0:18:18 > 0:18:20are hundreds of times denser than they are
0:18:20 > 0:18:22in the region around our sun.
0:18:24 > 0:18:28Finding an invisible black hole in all that swirling chaos
0:18:28 > 0:18:29would not be easy.
0:18:31 > 0:18:35It's like trying to pick out an individual
0:18:35 > 0:18:37inside the middle of a busy city
0:18:37 > 0:18:40where there are lights and cars
0:18:40 > 0:18:42and things happening all around them.
0:18:45 > 0:18:47But that wasn't the only problem.
0:18:48 > 0:18:52Vast swirling clouds of dust and gas prevent visible light
0:18:52 > 0:18:56from the centre of our galaxy from reaching us,
0:18:56 > 0:19:00making what lies beyond hidden from view.
0:19:00 > 0:19:04It's like putting a blanket over the thing you're trying to look at.
0:19:04 > 0:19:06It's putting a thick fog around that
0:19:06 > 0:19:09and so there's only certain wavelengths of light
0:19:09 > 0:19:11that can penetrate through that.
0:19:15 > 0:19:18Without the means to see through that dust,
0:19:18 > 0:19:21the black hole that theory suggested
0:19:21 > 0:19:25should reside at the centre of our Milky Way
0:19:25 > 0:19:30would remain nothing more than a bold but unproven idea.
0:19:42 > 0:19:45With the quest to find the black hole seemingly blocked,
0:19:45 > 0:19:48there was nevertheless one glimmer of hope.
0:19:50 > 0:19:53Now at least astronomers had some sort of notion
0:19:53 > 0:19:54where one should be hiding.
0:19:56 > 0:19:58To tackle the problem, what would be needed
0:19:58 > 0:20:02was a new generation of telescopes
0:20:02 > 0:20:06and that would take a new generation of astronomers.
0:20:06 > 0:20:10We were just at the point where we had the technology
0:20:10 > 0:20:12to address that question and so
0:20:12 > 0:20:14in some sense it was,
0:20:14 > 0:20:17I had the right hammer and I was looking for the right nail.
0:20:20 > 0:20:22With her Los Angeles group, Andrea Ghez
0:20:22 > 0:20:25began work on a telescope
0:20:25 > 0:20:28that could see through to the hidden centre of our galaxy.
0:20:30 > 0:20:35Just as I arrived at UCLA with my first faculty position,
0:20:35 > 0:20:39everything was falling into place in terms of the ability
0:20:39 > 0:20:41to answer this question at the centre of our galaxy.
0:20:41 > 0:20:44The telescopes were getting bigger
0:20:44 > 0:20:48so you had the ability to see fine details.
0:20:48 > 0:20:51We had an explosion in infra-red technology
0:20:51 > 0:20:57which meant that we could detect the kind of light that the stars emit,
0:20:57 > 0:21:01that you could actually see here on Earth and get through a lot of dust.
0:21:04 > 0:21:07The challenge was developing a telescope
0:21:07 > 0:21:11capable of overcoming the blurring effects of the Earth's atmosphere.
0:21:15 > 0:21:19Using lasers and specially-developed software,
0:21:19 > 0:21:21Ghez developed a telescope
0:21:21 > 0:21:26that made constant adjustments to tune out atmospheric distortion.
0:21:30 > 0:21:32We had a huge amount of scepticism.
0:21:32 > 0:21:34No-one had ever done this,
0:21:34 > 0:21:38but as I told my students, never take no for an answer
0:21:38 > 0:21:40so you find somebody that will help you out,
0:21:40 > 0:21:44loan you some telescope time and let you do a proof of concept
0:21:44 > 0:21:46to show that yes, this technology will work,
0:21:46 > 0:21:52and it's freshman physics that tells you that if the technology works,
0:21:52 > 0:21:55you should be able to see something if there is indeed a black hole.
0:21:58 > 0:22:01With her new telescope, the final obstacle
0:22:01 > 0:22:05to seeing into the centre of our galaxy had been removed.
0:22:08 > 0:22:12It was now possible to see in unprecedented detail
0:22:12 > 0:22:16right into the area where the black hole was believed to be hiding.
0:22:18 > 0:22:20If there is a black hole at the centre of our galaxy,
0:22:20 > 0:22:22that's going to force these objects
0:22:22 > 0:22:24that are really close to the black hole
0:22:24 > 0:22:27to move much faster than they would move if there were no black hole,
0:22:27 > 0:22:28so the first thing you want to see
0:22:28 > 0:22:31is that there are very fast moving objects
0:22:31 > 0:22:33where you think the black hole is.
0:22:33 > 0:22:37So, with our pictures that we took,
0:22:37 > 0:22:41what you can measure is how these stars move on the plane of the sky.
0:22:41 > 0:22:42You take one picture,
0:22:42 > 0:22:43you come back a year later,
0:22:43 > 0:22:47you take another picture and you see where they have moved to
0:22:47 > 0:22:48and what we see in this box
0:22:48 > 0:22:51are that there are stars that are moving incredibly quickly.
0:22:53 > 0:22:57That was the first evidence for the black hole.
0:23:00 > 0:23:03Once everything had been plotted out,
0:23:03 > 0:23:06this is the map of the galactic centre they were able to produce.
0:23:08 > 0:23:14It showed that stars were hurtling around in very fast and tight orbits
0:23:14 > 0:23:20but what Ghez was interested in was what they were circling around.
0:23:24 > 0:23:25If there's a black hole,
0:23:25 > 0:23:27there is a further prediction you can make
0:23:27 > 0:23:30about what these stars are going to do.
0:23:30 > 0:23:35They are going to move around the black hole on very short periods.
0:23:35 > 0:23:37In other words you're going to be able to see them
0:23:37 > 0:23:38move on more than just straight lines.
0:23:38 > 0:23:42As part of their travel around the black hole,
0:23:42 > 0:23:44these stars are going to move around the black hole
0:23:44 > 0:23:47because of the gravity just like planets move around the sun.
0:23:49 > 0:23:52There's only one thing that has the sheer force of gravity
0:23:52 > 0:23:58to compel such huge stars to veer round on such tight trajectories.
0:24:01 > 0:24:05So what we see is that indeed you can see these stars whip around.
0:24:05 > 0:24:07In fact from these images
0:24:07 > 0:24:09you can actually tell where the black hole is.
0:24:09 > 0:24:13The black hole is at the centre of the focus of these orbits.
0:24:17 > 0:24:19It was a stunning discovery.
0:24:24 > 0:24:27After a quest lasting decades,
0:24:27 > 0:24:30Donald Lynden-Bell had been proved right.
0:24:31 > 0:24:35Here indeed, just where he had predicted,
0:24:35 > 0:24:37was a supermassive black hole.
0:24:42 > 0:24:46But in the last year, the quest to find and understand black holes
0:24:46 > 0:24:48has suddenly become even more exciting.
0:24:50 > 0:24:52That's because out there in space
0:24:52 > 0:24:55something is about to happen
0:24:55 > 0:24:59that really is going to drag black holes out of the shadows
0:24:59 > 0:25:01to reveal them as they really are.
0:25:09 > 0:25:12The reason for the excitement
0:25:12 > 0:25:15is all because of a discovery made in Munich.
0:25:19 > 0:25:24Here a group working with the European Space Observatory
0:25:24 > 0:25:26had shared credit for discovering the black hole
0:25:26 > 0:25:28at the heart of the Milky Way.
0:25:33 > 0:25:38In late 2011, they made an almost accidental discovery,
0:25:38 > 0:25:43a discovery that's triggered this year's rush of excitement.
0:25:45 > 0:25:47It was while reviewing some data
0:25:47 > 0:25:50which had previously been dismissed as second rate
0:25:50 > 0:25:53that they noticed something unusual.
0:25:59 > 0:26:00We decided in 2011
0:26:00 > 0:26:04we should look at our data which is B-rated, so to say,
0:26:04 > 0:26:08data which is of somewhat lower quality because the resolution
0:26:08 > 0:26:12is not as good as you would get it under the best weather conditions.
0:26:12 > 0:26:15And then, boom, there was all of a sudden one source
0:26:15 > 0:26:17which was very close to the black hole.
0:26:21 > 0:26:24The object didn't appear to have the profile of a star.
0:26:27 > 0:26:30Instead it seemed to be a gas cloud
0:26:30 > 0:26:35moving at huge speeds right in the direction of the black hole.
0:26:38 > 0:26:42But what really rang alarm bells was the way it had changed shape.
0:26:43 > 0:26:46We see that this gas cloud as it moves
0:26:46 > 0:26:50closer and closer to the black hole is getting spaghetti-fied,
0:26:50 > 0:26:52like you see it in school books,
0:26:52 > 0:26:55according to the tidal shear, as we say,
0:26:55 > 0:26:57the tidal disruption by the black hole.
0:26:58 > 0:27:00It was moving quite fast
0:27:00 > 0:27:03and it's not moving in a straight line but it's a curved line,
0:27:03 > 0:27:06and that's a very, very bad sign
0:27:06 > 0:27:09because it tells you, well, there's something acting on it.
0:27:09 > 0:27:12It tells you, well, gravity is pulling on that object.
0:27:13 > 0:27:16It's pretty much directly head-on
0:27:16 > 0:27:19moving towards the centre of gravity, the black hole.
0:27:21 > 0:27:26The team's observations suggest the object is a gas cloud
0:27:26 > 0:27:28around three times the mass of the Earth.
0:27:30 > 0:27:33It seems they have discovered what is the great Holy Grail
0:27:33 > 0:27:35for black hole scientists.
0:27:37 > 0:27:39It almost goes straight in.
0:27:39 > 0:27:42Who aims that well, we don't know. It's remarkable.
0:27:42 > 0:27:46It's almost straight in, not quite but pretty much,
0:27:46 > 0:27:50and so that means it will go deep, deep into the centre of potential
0:27:50 > 0:27:53and therefore be sort of, if you like, a test, a test particle
0:27:53 > 0:27:57for us to probe the environment of the black hole.
0:28:13 > 0:28:18The gas cloud is advancing at speeds of over 2,000 kilometres per second.
0:28:27 > 0:28:30The team are cautiously optimistic the gas cloud
0:28:30 > 0:28:33will continue to be shredded
0:28:33 > 0:28:36by the extreme gravity surrounding the black hole,
0:28:36 > 0:28:40with every possibility that some of it will eventually be swallowed.
0:28:45 > 0:28:49It's clear that it will come very close to the black hole,
0:28:49 > 0:28:50might even hit the black hole.
0:28:53 > 0:28:56So maybe we actually are feeding the black hole here.
0:28:56 > 0:29:00Now exactly how much and how fast and all this is completely unknown
0:29:00 > 0:29:04and that's the excitement about it because we will learn about it.
0:29:04 > 0:29:06We have basically a test experiment.
0:29:06 > 0:29:09We know we have thrown, so to speak, at this black hole now
0:29:09 > 0:29:12a certain amount of mass which we roughly know.
0:29:12 > 0:29:13We know when it is and how close it comes
0:29:13 > 0:29:17and we can test over time how much happened.
0:29:22 > 0:29:26It's that chance to see a black hole feed at close range
0:29:26 > 0:29:29that has shaken the community of astronomers
0:29:29 > 0:29:33into an uncharacteristic fervour of excitement.
0:29:35 > 0:29:37We are facing here a very unusual situation in astronomy,
0:29:37 > 0:29:39namely that things are getting urgent.
0:29:39 > 0:29:41I mean, we only have half a year left or so,
0:29:41 > 0:29:43then you really want to observe it.
0:29:43 > 0:29:46Most of the objects we observe in astronomy
0:29:46 > 0:29:49are not evolving on the timescale of human life.
0:29:49 > 0:29:51That means mostly
0:29:51 > 0:29:53they look the same regardless if I look
0:29:53 > 0:29:58or if my grandson would look or whatever, it would be the same.
0:29:58 > 0:30:00But here we have an unusual case
0:30:00 > 0:30:03that the situation will change dramatically and quickly
0:30:03 > 0:30:05within a few years.
0:30:05 > 0:30:08That gas cloud was a compact object in 2004
0:30:08 > 0:30:11and probably it will be completely shredded in 2013.
0:30:14 > 0:30:17No-one knows for sure what will happen.
0:30:19 > 0:30:23An uncertainty that only adds to the sense of anticipation.
0:30:23 > 0:30:27Is it a cloud or is it a star?
0:30:27 > 0:30:31And I guess I'm of the opinion that this is a star,
0:30:31 > 0:30:36a star that has material around it
0:30:36 > 0:30:40but we know of other stars in this region that has material around it
0:30:40 > 0:30:43so that wouldn't make it unusual.
0:30:43 > 0:30:47If it's a star, the black hole might not get a bite at it.
0:30:47 > 0:30:50As of now, no-one can be certain.
0:30:50 > 0:30:52This is what makes science interesting
0:30:52 > 0:30:55because it's a point where you get to gamble.
0:30:55 > 0:30:57You get to make a bet. What is this?
0:30:57 > 0:30:59What should happen next?
0:31:13 > 0:31:18To stare into the void of a black hole,
0:31:18 > 0:31:22to tumble through space before disappearing forever within it,
0:31:22 > 0:31:27it's the prospect of catching that unique moment
0:31:27 > 0:31:30that explains the excitement of this year's events.
0:31:32 > 0:31:38What happens to matter once it's been swallowed, we will never know.
0:31:55 > 0:31:58But it's what a black hole does as it feeds
0:31:58 > 0:32:00that holds the true surprise.
0:32:04 > 0:32:07It would prove to be key to revealing what black holes really are,
0:32:11 > 0:32:15and their hidden role at the heart of galaxies.
0:32:34 > 0:32:37That picture that matter gets sucked into a black hole,
0:32:37 > 0:32:43that's one of the biggest confusions about black holes that's out there,
0:32:43 > 0:32:49partially because of science fiction like Star Trek and things like that,
0:32:49 > 0:32:51so for matter that's far away from a black hole,
0:32:51 > 0:32:53it actually doesn't get sucked in.
0:32:53 > 0:32:56It's very much like the planets in the solar system
0:32:56 > 0:32:58going around the sun.
0:32:58 > 0:33:01Things just go around and around and around and around.
0:33:12 > 0:33:16The difference is that when you have a lot of gas,
0:33:16 > 0:33:20a lot of stuff orbiting around the black hole,
0:33:20 > 0:33:22there is a little bit of friction
0:33:22 > 0:33:27that causes matter to slowly spiral in towards the black hole.
0:33:32 > 0:33:36As gas continues to spiral in towards the event horizon,
0:33:36 > 0:33:41gravity climbs to staggering extremes.
0:33:43 > 0:33:47Gas molecules are forced into a whirlpool
0:33:47 > 0:33:51as they queue up to be devoured by the black hole.
0:33:54 > 0:33:59Friction between gas particles in this cosmic waiting line
0:33:59 > 0:34:05produces the densest, hottest most electrically-charged environment
0:34:05 > 0:34:09to be found anywhere in the universe.
0:34:11 > 0:34:15Friction between different parts of the gas cause it to heat up
0:34:15 > 0:34:17and it's very much like
0:34:17 > 0:34:20when the Apollo rockets returned to the Earth
0:34:20 > 0:34:22and travelled through the Earth's atmosphere.
0:34:28 > 0:34:31As they ploughed through the Earth's atmosphere they heat up
0:34:31 > 0:34:33because of the friction between the satellite
0:34:33 > 0:34:35and the atmosphere of the Earth.
0:34:42 > 0:34:44What we know is that the hotter something gets,
0:34:44 > 0:34:47the brighter it gets, the more light it emits.
0:34:51 > 0:34:54Under the intense gravitational fields
0:34:54 > 0:34:56at the entrance to the black hole,
0:34:56 > 0:35:00the dense super-heated disc of matter waiting to be swallowed
0:35:00 > 0:35:07begins to shine like a sun, but a sun like no other.
0:35:23 > 0:35:27Here then is the strange paradox of black holes,
0:35:29 > 0:35:34that a feeding black hole is anything but black.
0:35:41 > 0:35:45Just how greedy and bright a black hole can get is revealed by
0:35:45 > 0:35:49an outwardly very ordinary-looking galaxy called Cygnus A,
0:35:49 > 0:35:53some 650 million light years away.
0:35:55 > 0:35:57If we look at it with visible light,
0:35:57 > 0:36:00we see that the inner parts of that galaxy,
0:36:00 > 0:36:03maybe a few 10,000 light years across,
0:36:03 > 0:36:05is kind of ordinary.
0:36:05 > 0:36:07There are stars, there's gas, there's dust.
0:36:07 > 0:36:10It's a sort of indiscriminately messy place
0:36:10 > 0:36:12but it's not that special.
0:36:14 > 0:36:16Now if we look in different wavelengths,
0:36:16 > 0:36:20for example in radio waves, we see something completely different.
0:36:22 > 0:36:25Cygnus A transforms into something else entirely.
0:36:27 > 0:36:31What we see is no longer the galaxy with its stars
0:36:31 > 0:36:34but instead we see an extreme structure
0:36:34 > 0:36:39spread across intergalactic space and this structure is enormous.
0:36:39 > 0:36:45It stretches 500,000 light years across
0:36:45 > 0:36:50and it consists of these enormous lobes of brightness,
0:36:50 > 0:36:53linked together by what looks like a thread of light
0:36:53 > 0:36:58leading to a tiny bright point at the very centre of the Cygnus A galaxy.
0:37:02 > 0:37:04This structure is enormously luminous
0:37:04 > 0:37:06and there's also a huge amount of energy
0:37:06 > 0:37:08just in the particles themselves
0:37:08 > 0:37:11because they've been accelerated to close to the speed of light,
0:37:11 > 0:37:14so if you add up all the energy in this great structure
0:37:14 > 0:37:18it's probably at least a trillion times the amount of energy
0:37:18 > 0:37:20that our sun puts out on a regular basis.
0:37:32 > 0:37:38We now know this light is produced by the rotating disc of matter,
0:37:38 > 0:37:40spinning round the edge of the black hole
0:37:40 > 0:37:46at the heart of the Cygnus A galaxy waiting to be devoured.
0:37:49 > 0:37:53It means that against all popular expectations,
0:37:53 > 0:37:56the brightest sources of light in the universe
0:37:56 > 0:37:59are actually black holes.
0:38:06 > 0:38:12That fundamental fact is one of the great surprises about black holes.
0:38:12 > 0:38:13You know, by their very name
0:38:13 > 0:38:17you would think that black holes would be these dark objects
0:38:17 > 0:38:20that wouldn't produce any light, and that's true.
0:38:20 > 0:38:24If you just have a black hole sitting by itself, alone,
0:38:24 > 0:38:26it doesn't produce any light
0:38:26 > 0:38:29but in nature we have gas spiralling into black holes
0:38:29 > 0:38:34and that turns out to produce the most efficient sources of light
0:38:34 > 0:38:38and the brightest sources of light that we know of in the universe.
0:38:40 > 0:38:45So here then was the answer to the great quasar mystery.
0:38:47 > 0:38:52Quasars are nothing less than feeding supermassive black holes.
0:38:55 > 0:39:00It was exactly what Donald Lynden-Bell had first predicted.
0:39:04 > 0:39:08Behind every quasar is a black hole
0:39:08 > 0:39:12and it took a long time for even astronomers to accept this
0:39:12 > 0:39:14because it's quite a concept,
0:39:14 > 0:39:17that there are these engines out there
0:39:17 > 0:39:20that fit a variety of different situations
0:39:20 > 0:39:23and produce some of the most energetic phenomena
0:39:23 > 0:39:24we see in the universe.
0:39:29 > 0:39:34Today the black hole at the centre of our galaxy is dark.
0:39:35 > 0:39:40The super bright quasar phase having ended many billions of years ago
0:39:40 > 0:39:45when the fuel that fires violent emissions was completely consumed.
0:39:55 > 0:39:58But now, with the approaching gas cloud
0:39:58 > 0:40:02and the prospect of feeding,
0:40:02 > 0:40:05the black hole should get brighter.
0:40:09 > 0:40:12Exactly how much it's pretty hard to tell.
0:40:12 > 0:40:14We know roughly the amount of mass.
0:40:14 > 0:40:17If you dump that amount of mass very quickly onto the black hole,
0:40:17 > 0:40:18it will be a huge event.
0:40:18 > 0:40:21I mean, the galactic centre of the black hole
0:40:21 > 0:40:23would flare up by orders of magnitude.
0:40:23 > 0:40:28A feeding binge on this scale is considered a low probability.
0:40:29 > 0:40:34What astronomers consider to be more probable is that the black hole
0:40:34 > 0:40:38will take snack-size nibbles out of the gas cloud.
0:40:38 > 0:40:42It probably will take quite a while, so let's say ten years,
0:40:42 > 0:40:44and so this whole event will then be stretched out
0:40:44 > 0:40:47and therefore at any given time a little less spectacular,
0:40:47 > 0:40:50but we will see, I think we probably will see these effects.
0:40:54 > 0:40:57And so this summer the world's most powerful telescopes
0:40:57 > 0:41:01will be keenly trained on our galactic centre
0:41:01 > 0:41:05as the predictions of astronomers are put to the test
0:41:05 > 0:41:09in the fiery ordeal of actual events.
0:41:22 > 0:41:24With the new understanding of the behaviour
0:41:24 > 0:41:28of feeding black holes at the heart of galaxies,
0:41:28 > 0:41:31an unexpected new story is now emerging,
0:41:31 > 0:41:36a story that reaches right out to our own solar system
0:41:36 > 0:41:41and surprisingly touches us, here on planet Earth.
0:41:46 > 0:41:49Far from being violent agents of destruction,
0:41:49 > 0:41:53it seems instead black holes might actually
0:41:53 > 0:41:56be benign architects which have played a part
0:41:56 > 0:42:02in the creation of galaxies, stars, and even of life itself.
0:42:11 > 0:42:13One of the first scientists
0:42:13 > 0:42:18to begin to see black holes in this different way was Dr John Magorrian.
0:42:22 > 0:42:25He was fascinated by the mysterious relationship
0:42:25 > 0:42:29between supermassive black holes and the galaxies around them.
0:42:43 > 0:42:44The key breakthrough in his work
0:42:44 > 0:42:50came with the availability of detailed images of remote galaxies,
0:42:50 > 0:42:53produced by the new Hubble Space Telescope.
0:43:00 > 0:43:01One way of thinking about this
0:43:01 > 0:43:06is to imagine that galaxies are like miniature light bulbs out in space,
0:43:06 > 0:43:08and so with earlier telescopes
0:43:08 > 0:43:10you could see that there was a light bulb there
0:43:10 > 0:43:13but then with newer telescopes such as the Hubble,
0:43:13 > 0:43:16then we're able to look in more detail
0:43:16 > 0:43:18at exactly what was going on inside the light bulb
0:43:18 > 0:43:22so you maybe could make out details of the filaments,
0:43:22 > 0:43:24of the wires inside and so on.
0:43:26 > 0:43:28With these high-resolution images,
0:43:28 > 0:43:32astronomers could compare the size of galaxies
0:43:32 > 0:43:36to the size of the black hole at their centres.
0:43:40 > 0:43:43Was there any connection between the two?
0:43:46 > 0:43:50What Magorrian discovered was completely unexpected.
0:43:52 > 0:43:54The relationship that we found
0:43:54 > 0:43:56was essentially that the bigger the galaxy,
0:43:56 > 0:43:57the bigger the black hole.
0:43:57 > 0:43:59That's in its broadest terms.
0:43:59 > 0:44:01If you want to be a bit more precise about it,
0:44:01 > 0:44:05we found that the mass of the black hole
0:44:05 > 0:44:07was very strongly related
0:44:07 > 0:44:09to the mass of the surrounding galaxy.
0:44:09 > 0:44:12There is a nice linear relationship between these two
0:44:12 > 0:44:14with the mass of the black hole
0:44:14 > 0:44:19being around about 0.5% of the mass of the host galaxy.
0:44:22 > 0:44:26The relationship Magorrian had discovered between galaxies
0:44:26 > 0:44:28and the tiny black holes at their centre
0:44:28 > 0:44:30seemed so strange and odd
0:44:30 > 0:44:34that Magorrian and his colleagues thought that they'd made a mistake.
0:44:36 > 0:44:40It was like suggesting that something as tiny as a coin
0:44:40 > 0:44:43could control something as massive as the Earth.
0:44:49 > 0:44:50When we discovered this correlation
0:44:50 > 0:44:54between black hole mass and galaxy mass, we were surprised.
0:44:54 > 0:44:57Then that was immediately followed by nervousness.
0:44:59 > 0:45:03The nervousness then started to give way to possible mild elation
0:45:03 > 0:45:06that we'd discovered something new and fundamental.
0:45:08 > 0:45:13That correlation became known as the Magorrian relationship,
0:45:13 > 0:45:16and it did indeed point to something profound.
0:45:18 > 0:45:20This is incredibly important
0:45:20 > 0:45:22because it really meant
0:45:22 > 0:45:28that there was something linking these tiny supermassive black holes
0:45:28 > 0:45:32in the centre of galaxies with the whole galaxy itself.
0:45:32 > 0:45:36It meant that somehow their whole history had been intertwined,
0:45:36 > 0:45:38that the growth of the galaxies
0:45:38 > 0:45:42and the growth of the black holes was somehow related.
0:45:48 > 0:45:51There was now a pressing challenge
0:45:51 > 0:45:53to understand how black holes
0:45:53 > 0:45:55and their surrounding galaxies
0:45:55 > 0:45:58could be so intertwined.
0:46:03 > 0:46:06Professor Andy Fabian of Cambridge University
0:46:06 > 0:46:08is one astronomer who began to look.
0:46:14 > 0:46:17Like the ripples that travel out from his paddles,
0:46:17 > 0:46:21it's the extreme radiation pulsing out of black holes
0:46:21 > 0:46:23that Fabian turned to for clues.
0:46:28 > 0:46:30To see that radiation clearly,
0:46:30 > 0:46:33you need to look beyond the ordinary light of the stars
0:46:33 > 0:46:35at one kind of emission
0:46:35 > 0:46:40that's the fiery signature of feeding black holes.
0:46:49 > 0:46:50Stars and everything are beautiful,
0:46:50 > 0:46:52make galaxies and that,
0:46:52 > 0:46:54but there's a lot of other things going on out there,
0:46:54 > 0:46:57and enormous amounts of energy being released
0:46:57 > 0:47:01which we can only be aware of if we look with X-ray eyes.
0:47:06 > 0:47:10One cluster of galaxies in particular, Perseus,
0:47:10 > 0:47:13is a long-standing object of fascination.
0:47:15 > 0:47:17250 million light years away,
0:47:17 > 0:47:20Fabian has spent over 40 years
0:47:20 > 0:47:22studying this fascinating piece of the sky.
0:47:22 > 0:47:27What's intriguing is this thing here.
0:47:27 > 0:47:31This is the central galaxy in the Perseus cluster
0:47:31 > 0:47:35and the fact that it's got all this red and blue stuff going around it
0:47:35 > 0:47:37means there's something going on.
0:47:43 > 0:47:46The fiery monster hiding at the heart of Perseus
0:47:46 > 0:47:50was only revealed when Fabian was able to look at the cluster
0:47:50 > 0:47:53in the X-ray part of the spectrum.
0:48:01 > 0:48:04What we could see was unexpected.
0:48:08 > 0:48:09The X-ray image revealed
0:48:09 > 0:48:12how the black hole at the heart of the galaxy
0:48:12 > 0:48:18was firing unimaginable amounts of radiation into surrounding space,
0:48:18 > 0:48:20and with extraordinary consequences.
0:48:26 > 0:48:29We could see what was going on at the centre
0:48:29 > 0:48:33and we could start to understand how the black hole
0:48:33 > 0:48:38was feeding energy out into all the surrounding gas.
0:48:40 > 0:48:43What the image had captured was the mechanism by which
0:48:43 > 0:48:48a feeding black hole can dominate everything around it.
0:48:50 > 0:48:55What it's doing is blowing bubbles at the centre of the cluster,
0:48:55 > 0:49:00and those bubbles are then expanding and growing
0:49:00 > 0:49:04like a pair of bubbles might be formed in a fish tank aerator.
0:49:08 > 0:49:09The dark areas in the image
0:49:09 > 0:49:12represent bubbles of super-heated gas,
0:49:12 > 0:49:17showing how the black hole blasts away matter from the centre.
0:49:19 > 0:49:23With each bubble almost the size of our own Milky Way,
0:49:23 > 0:49:27it is doing so across extraordinary distances.
0:49:31 > 0:49:33So this is showing you the scale.
0:49:33 > 0:49:37We're seeing the black hole at the centre
0:49:37 > 0:49:41having a galaxy-wide effect on the surroundings.
0:49:41 > 0:49:42It's obvious in this image.
0:49:42 > 0:49:45I don't need to tell you any more because you can see it.
0:49:48 > 0:49:50What the image points to
0:49:50 > 0:49:53is an explanation for the strange correlation
0:49:53 > 0:49:54between the mass of a black hole
0:49:54 > 0:49:57and the mass of its surrounding galaxy.
0:50:02 > 0:50:06Galaxies could, in a way, be much bigger than they currently are.
0:50:06 > 0:50:09Something is stopping them growing larger,
0:50:09 > 0:50:13and that something is the black hole at the centre.
0:50:13 > 0:50:14Now this is bizarre
0:50:14 > 0:50:18because the ratio of the size of the black hole
0:50:18 > 0:50:20to the size of the galaxy
0:50:20 > 0:50:23is the same as the ratio between a grape,
0:50:23 > 0:50:26or something this big, and the size of the Earth.
0:50:26 > 0:50:31Now you might think that it's impossible for something that small
0:50:31 > 0:50:35to control something that large but that's what appears to be happening.
0:50:39 > 0:50:43As the black hole begins to devour matter,
0:50:43 > 0:50:45so it starts to pour out energy.
0:50:47 > 0:50:50Like a cosmic brew,
0:50:50 > 0:50:54that energy sweeps matter back out from the centre of the galaxy,
0:50:54 > 0:50:57preventing it from clumping together to form new stars.
0:51:01 > 0:51:04The conclusion of this is that the total number of stars
0:51:04 > 0:51:08that form in a galaxy appears to be stopped, truncated
0:51:08 > 0:51:11by the power of the black hole at the centre.
0:51:16 > 0:51:19The discovery of that relationship
0:51:19 > 0:51:20has turned every preconception
0:51:20 > 0:51:23about the nature of black holes on its head.
0:51:25 > 0:51:29Instead of being strange, cosmic aberrations,
0:51:29 > 0:51:32black holes have moved to the very centre
0:51:32 > 0:51:35of the story of galaxies and stars,
0:51:35 > 0:51:39a story that must include our own solar system.
0:51:41 > 0:51:45And that must mean that in some way
0:51:45 > 0:51:49our own black hole must have played a part
0:51:49 > 0:51:52in what is perhaps the greatest mystery of all.
0:52:09 > 0:52:11To walk here on Earth,
0:52:11 > 0:52:13to be alive,
0:52:13 > 0:52:16is thanks to a long chain of cause and effect
0:52:16 > 0:52:22written deep into the structure of the universe,
0:52:22 > 0:52:26a primordial process so long and so ancient
0:52:26 > 0:52:32that on the scale of a human life, it seems almost incomprehensible.
0:52:37 > 0:52:40One of the most amazing things in our universe
0:52:40 > 0:52:42is that we are made of stars.
0:52:43 > 0:52:47The heavy elements in our bodies, the carbon and the oxygen
0:52:47 > 0:52:51and the nitrogen used to be millions of miles down inside stars.
0:52:54 > 0:52:57So our existence here on this planet
0:52:57 > 0:53:01relies on a deep history of stars being born,
0:53:01 > 0:53:04creating new elements,
0:53:04 > 0:53:06and then spitting those elements back out into the cosmos
0:53:06 > 0:53:09where they're in turn recycled many, many times.
0:53:13 > 0:53:18Over and over again, for almost 14 billion years,
0:53:18 > 0:53:20ever since the beginning of the universe
0:53:20 > 0:53:23and the formation of the first stars,
0:53:23 > 0:53:28black holes have influenced this cosmic recycling process.
0:53:30 > 0:53:33And since the elements forged in those stars
0:53:33 > 0:53:35ended up inside planets like our own,
0:53:35 > 0:53:41it means our black hole must have created the conditions
0:53:41 > 0:53:46to make it just right for life to emerge here on Earth.
0:53:51 > 0:53:53We're very lucky
0:53:53 > 0:53:56we're not close by enough to one that's in a feeding frenzy,
0:53:56 > 0:53:59that we get washed across by this destructive radiation
0:53:59 > 0:54:01that will tear apart our molecules and our atmosphere,
0:54:01 > 0:54:05and basically leave us in a barren place.
0:54:07 > 0:54:11And then there's the other extreme where things are extremely quiet
0:54:11 > 0:54:15and cold and maybe there haven't been that many stars formed ever,
0:54:15 > 0:54:19because nothing stirred it up and nothing really got processes going
0:54:19 > 0:54:21that would make all the elements
0:54:21 > 0:54:23and make new generations of planets and so on.
0:54:27 > 0:54:30It means our black hole must have left its fingerprints
0:54:30 > 0:54:33on the unique chemistry that made possible
0:54:33 > 0:54:36the first stirrings of life here on Earth.
0:54:41 > 0:54:44If you look at the Milky Way Galaxy,
0:54:44 > 0:54:46it's this interesting balance point,
0:54:46 > 0:54:49it's this place where there's just enough wash from the black hole
0:54:49 > 0:54:51to keep things interesting,
0:54:51 > 0:54:54to possibly make the environment that allows us to exist here.
0:55:07 > 0:55:11- NEWSREADER:- 'Astronomers are eagerly awaiting
0:55:11 > 0:55:13'a spectacular fireworks display
0:55:13 > 0:55:16'as a supermassive black hole at the centre of our galaxy... '
0:55:16 > 0:55:19For the coming months across the world,
0:55:19 > 0:55:21astronomers will be turning their telescopes
0:55:21 > 0:55:24towards the centre of the Milky Way
0:55:24 > 0:55:26ready to be awed by this historic chance
0:55:26 > 0:55:30to witness a black hole sitting down to feed.
0:55:31 > 0:55:34'..a vast cloud of interstellar dust and gas.'
0:55:38 > 0:55:40It's the culmination of a 40-year journey
0:55:40 > 0:55:43to get closer to that tantalising edge
0:55:43 > 0:55:48between the universe that we can see and understand,
0:55:48 > 0:55:56and that place of extremes that will forever be unseen and unknowable.
0:56:10 > 0:56:11We tend to think of black holes
0:56:11 > 0:56:15as these incredibly destructive, chaotic objects
0:56:15 > 0:56:19but now we understand that they're actually an integral part
0:56:19 > 0:56:21of why galaxies are the way they are.
0:56:26 > 0:56:2720 years ago
0:56:27 > 0:56:30black holes were seen as a possible ornament
0:56:30 > 0:56:32in the middle of a galaxy.
0:56:32 > 0:56:36Now we know that they may be the absolute machine,
0:56:36 > 0:56:39the driving force for the eventual size
0:56:39 > 0:56:43and possibly the shape of the galaxy.
0:56:46 > 0:56:50The story of black holes that began as just this idea,
0:56:50 > 0:56:54this thing that sprung out of pure human thought and mathematics,
0:56:54 > 0:56:57and at first was seen too outrageous to be possible,
0:56:57 > 0:57:01and over time we've learnt that not only are these things out there,
0:57:01 > 0:57:06but they play this vital, important role that we're still learning about,
0:57:06 > 0:57:09we're still discovering almost every day something new
0:57:09 > 0:57:12about supermassive black holes and what they do in the universe.
0:57:14 > 0:57:17Who knows what we're actually going to ultimately find out about them!
0:57:37 > 0:57:42Subtitles by Red Bee Media Ltd