1 00:00:01,769 --> 00:00:03,902 Narrator: Supermassive black holes -- 2 00:00:03,904 --> 00:00:08,374 Gargantuan monsters that lurk at the center of galaxies. 3 00:00:08,376 --> 00:00:11,276 Right now you are traveling at half a million miles an hour 4 00:00:11,278 --> 00:00:13,012 Around a giant black hole 5 00:00:13,014 --> 00:00:15,047 Four million times the mass of the sun. 6 00:00:15,049 --> 00:00:18,083 Narrator: But there's a mystery about these colossal beasts. 7 00:00:18,085 --> 00:00:21,053 We have no idea where they came from. 8 00:00:21,055 --> 00:00:23,822 How did they get so big so quickly? 9 00:00:23,824 --> 00:00:26,625 We know they weren't "born" or created that way. 10 00:00:26,627 --> 00:00:28,227 It doesn't make sense. 11 00:00:28,229 --> 00:00:30,596 Narrator: Today, investigators are seeing 12 00:00:30,598 --> 00:00:35,234 Tantalizing glimpses of an entirely new type of black hole. 13 00:00:36,303 --> 00:00:38,470 This thing essentially jumped at me. 14 00:00:38,472 --> 00:00:40,406 Narrator: Could this new breed of black hole 15 00:00:40,408 --> 00:00:44,309 Be the seeds that built the supermassive monsters? 16 00:00:44,311 --> 00:00:47,646 It is almost a kind of cosmic miracle. 17 00:00:47,648 --> 00:00:49,748 Narrator: And might they even hold a clue 18 00:00:49,750 --> 00:00:52,985 To how the milky way itself formed? 19 00:00:52,987 --> 00:00:55,054 Oluseyi: It sounds crazy and like science fiction, 20 00:00:55,056 --> 00:00:56,688 But it's science reality. 21 00:00:56,690 --> 00:00:59,124 Narrator: The race is on to find the missing link 22 00:00:59,126 --> 00:01:02,394 That will reveal how supermassive black holes 23 00:01:02,396 --> 00:01:04,897 And the galaxies around them were created. 24 00:01:04,899 --> 00:01:08,400 I would say this is the golden age of black hole physics. 25 00:01:08,402 --> 00:01:13,172 Narrator: This is the final chapter in our cosmic creation story. 26 00:01:13,174 --> 00:01:22,114 ♪ 27 00:01:22,116 --> 00:01:25,117 -- Captions by vitac -- www.Vitac.Com 28 00:01:25,119 --> 00:01:28,120 Captions paid for by discovery communications 29 00:01:28,122 --> 00:01:33,759 At the very heart of every large galaxy lurks a monster -- 30 00:01:33,761 --> 00:01:36,595 A supermassive black hole. 31 00:01:36,597 --> 00:01:39,465 These are the undisputed heavyweight champions 32 00:01:39,467 --> 00:01:42,968 Of the cosmos. 33 00:01:42,970 --> 00:01:45,737 There's a trillion galaxies in the observable universe, 34 00:01:45,739 --> 00:01:48,774 And each one has a supermassive black hole in its center. 35 00:01:52,346 --> 00:01:54,480 Narrator: Supermassive black holes can weigh 36 00:01:54,482 --> 00:01:58,450 As much as six billion suns, and all that matter 37 00:01:58,452 --> 00:02:02,020 Is packed into a tiny point in space. 38 00:02:02,022 --> 00:02:05,457 They'll suck in anything that strays too close. 39 00:02:05,459 --> 00:02:10,395 Planets, stars, not even light can escape. 40 00:02:10,397 --> 00:02:12,931 A black hole is a bottomless pit of gravity 41 00:02:12,933 --> 00:02:15,033 That actually draws in material all around it. 42 00:02:16,270 --> 00:02:17,302 Plait: If you get too close, 43 00:02:17,304 --> 00:02:19,605 There is no force in the universe 44 00:02:19,607 --> 00:02:22,074 That you can apply to yourself to get back out. 45 00:02:23,377 --> 00:02:26,678 Narrator: But as well as being the ultimate agents of destruction, 46 00:02:26,680 --> 00:02:31,150 Supermassive black holes bring order to the universe. 47 00:02:31,152 --> 00:02:34,019 Their colossal gravity corrals countless stars 48 00:02:34,021 --> 00:02:38,223 Into orbit around them, forming the hearts of galaxies. 49 00:02:38,225 --> 00:02:40,259 Plait: We think that the galaxy itself 50 00:02:40,261 --> 00:02:44,129 Depends on that supermassive black hole for its structure. 51 00:02:45,332 --> 00:02:47,332 If these things didn't exist, 52 00:02:47,334 --> 00:02:50,636 Galaxies would look completely different. 53 00:02:52,239 --> 00:02:56,308 Narrator: But a big mystery surrounds supermassive black holes. 54 00:02:56,310 --> 00:02:59,678 We have no idea where they came from. 55 00:02:59,680 --> 00:03:04,183 How does the universe compress the mass of six billion stars 56 00:03:04,185 --> 00:03:06,585 Into a single point in space? 57 00:03:06,587 --> 00:03:08,120 The answer won't just tell us 58 00:03:08,122 --> 00:03:10,622 How supermassive black holes form. 59 00:03:10,624 --> 00:03:13,091 It may reveal how the galaxies 60 00:03:13,093 --> 00:03:16,628 That fill the universe came to exist, too. 61 00:03:16,630 --> 00:03:19,865 If we can understand how supermassive black holes grow, 62 00:03:19,867 --> 00:03:21,867 Then that's kind of like the holy grail 63 00:03:21,869 --> 00:03:24,036 Of understanding how galaxies evolve. 64 00:03:25,539 --> 00:03:29,241 Narrator: Maybe the answer to how supermassive black holes formed 65 00:03:29,243 --> 00:03:33,712 Can be found in the life and death of other black holes. 66 00:03:33,714 --> 00:03:37,449 Because we've long known that supermassive black holes 67 00:03:37,451 --> 00:03:39,685 Have a tiny relative -- 68 00:03:39,687 --> 00:03:41,453 Stellar black holes. 69 00:03:41,455 --> 00:03:44,156 And unlike their supermassive cousins, 70 00:03:44,158 --> 00:03:48,961 We do know how these tiny stellar black holes form. 71 00:03:48,963 --> 00:03:52,531 Stellar-mass black holes form when a massive star dies. 72 00:03:54,134 --> 00:03:56,802 The core collapses into this super-dense object 73 00:03:56,804 --> 00:03:58,003 That we call a black hole. 74 00:03:59,907 --> 00:04:01,940 The core might have three or five 75 00:04:01,942 --> 00:04:03,842 Or 10 times the mass of the sun. 76 00:04:03,844 --> 00:04:06,345 And that's why they are stellar-mass black holes. 77 00:04:06,347 --> 00:04:08,113 They have about the mass of a star. 78 00:04:11,118 --> 00:04:17,055 Narrator: When a huge star dies in a dramatic supernova explosion, 79 00:04:17,057 --> 00:04:21,593 All that's left is the dense remnants of the star's core, 80 00:04:21,595 --> 00:04:24,630 Crammed into a minuscule point in space -- 81 00:04:24,632 --> 00:04:26,431 A stellar black hole. 82 00:04:28,035 --> 00:04:30,836 Imagine that a star like the sun 83 00:04:30,838 --> 00:04:33,705 Can shrink down to essentially a pinhead size. 84 00:04:33,707 --> 00:04:36,508 It sounds wild and crazy and like science fiction. 85 00:04:36,510 --> 00:04:38,777 But it's science reality. 86 00:04:38,779 --> 00:04:42,047 Narrator: If collapsing stars form stellar black holes, 87 00:04:42,049 --> 00:04:45,717 Could their supermassive cousins have formed this way, too? 88 00:04:45,719 --> 00:04:48,954 It's a neat idea, but there's a problem. 89 00:04:50,824 --> 00:04:53,458 Stellar black holes may weigh in 90 00:04:53,460 --> 00:04:56,395 At several times the mass of our sun, 91 00:04:56,397 --> 00:04:58,363 But they're a million times smaller. 92 00:04:58,365 --> 00:05:00,365 That means they're dwarfed 93 00:05:00,367 --> 00:05:03,468 By the monstrous supermassive black holes. 94 00:05:06,573 --> 00:05:08,740 Supermassive black holes can be 95 00:05:08,742 --> 00:05:11,043 As big as an entire solar system. 96 00:05:13,547 --> 00:05:16,048 No single star could ever be big enough 97 00:05:16,050 --> 00:05:19,351 To collapse into a monster black hole this size. 98 00:05:21,088 --> 00:05:24,022 The challenge for scientists is to figure out 99 00:05:24,024 --> 00:05:26,692 How the universe created black holes 100 00:05:26,694 --> 00:05:30,295 That are billions of times more massive than the sun. 101 00:05:30,297 --> 00:05:31,930 One theory is that 102 00:05:31,932 --> 00:05:36,301 Perhaps supermassive black holes weren't born big. 103 00:05:36,303 --> 00:05:39,271 Instead, they may have grown from smaller black holes 104 00:05:39,273 --> 00:05:41,707 Merging with each other. 105 00:05:42,776 --> 00:05:45,210 Theorists have long predicted that 106 00:05:45,212 --> 00:05:48,046 Black holes should be able to merge. 107 00:05:48,048 --> 00:05:51,616 But astronomers need observations to prove it's true. 108 00:05:53,220 --> 00:05:56,355 In the heart of the idyllic italian countryside 109 00:05:56,357 --> 00:05:58,790 Sits a machine designed to detect 110 00:05:58,792 --> 00:06:01,827 The far-off murmurs of black holes merging. 111 00:06:03,964 --> 00:06:05,931 This is virgo. 112 00:06:07,301 --> 00:06:11,436 Here, scientists monitor the cosmos 24/7, 113 00:06:11,438 --> 00:06:13,438 Hunting for black holes. 114 00:06:15,509 --> 00:06:19,311 Walter del pozzo is a theorist on the team. 115 00:06:19,313 --> 00:06:21,913 Del pozzo: What I do is trying to understand 116 00:06:21,915 --> 00:06:24,483 What black holes are and how they work 117 00:06:24,485 --> 00:06:26,818 And how they grow, how they evolve. 118 00:06:26,820 --> 00:06:29,321 I love the challenge of trying 119 00:06:29,323 --> 00:06:31,623 To understand how the universe work. 120 00:06:33,060 --> 00:06:35,060 Narrator: Walter wants to use virgo 121 00:06:35,062 --> 00:06:37,763 To do something that was once thought impossible. 122 00:06:37,765 --> 00:06:40,766 He hopes to detect black holes growing. 123 00:06:42,236 --> 00:06:46,037 Walter believes that if one black hole merges with another, 124 00:06:46,039 --> 00:06:49,607 The violence of this event should send tell-tale ripples 125 00:06:49,609 --> 00:06:51,943 Out through the fabric of space... 126 00:06:53,514 --> 00:06:55,247 ...Just like the ripples in a pond. 127 00:06:57,151 --> 00:07:00,752 Physicists call these ripples gravitational waves. 128 00:07:02,089 --> 00:07:05,056 It was once thought that they'd be too small to detect. 129 00:07:05,058 --> 00:07:07,626 But then machines like virgo came along. 130 00:07:07,628 --> 00:07:09,961 Virgo consists of not one 131 00:07:09,963 --> 00:07:13,999 But two two-mile-long pipes forming an l shape. 132 00:07:14,001 --> 00:07:16,234 These pipes are the most sensitive 133 00:07:16,236 --> 00:07:18,170 Measuring devices on earth. 134 00:07:19,606 --> 00:07:23,608 A laser is shot along these two right-angle lines. 135 00:07:23,610 --> 00:07:27,112 They travel all the way to the end. 136 00:07:27,114 --> 00:07:28,513 They bounce on a mirror. 137 00:07:28,515 --> 00:07:29,848 They come back. 138 00:07:29,850 --> 00:07:32,417 This makes these two arms 139 00:07:32,419 --> 00:07:35,420 A very, very, very sensitive ruler, 140 00:07:35,422 --> 00:07:39,491 Which we can use to detect tiny changes in the distances. 141 00:07:40,928 --> 00:07:44,095 Narrator: If a gravitational wave from merging black holes 142 00:07:44,097 --> 00:07:46,998 Passes through virgo's two pipes, 143 00:07:47,000 --> 00:07:52,204 It could compress and expand first one pipe then the other -- 144 00:07:52,206 --> 00:07:54,639 Changes in length walter hopes to measure. 145 00:07:57,711 --> 00:08:00,045 Those changes are really, really tiny. 146 00:08:00,047 --> 00:08:05,317 This is why we need those huge, huge rulers -- 147 00:08:05,319 --> 00:08:08,220 To be able to detect those tiny, tiny, tiny changes. 148 00:08:10,858 --> 00:08:11,857 [ alarm blaring ] 149 00:08:11,859 --> 00:08:13,425 Narrator: These lasers can detect 150 00:08:13,427 --> 00:08:16,294 These two-mile-long pipes changing length 151 00:08:16,296 --> 00:08:19,865 By a billionth of the width of a human hair. 152 00:08:19,867 --> 00:08:22,801 And in August 2017, 153 00:08:22,803 --> 00:08:24,903 These super-sensitive instruments 154 00:08:24,905 --> 00:08:29,174 Allow walter and the team to witness something extraordinary. 155 00:08:29,176 --> 00:08:32,244 They detect the unmistakable ripple 156 00:08:32,246 --> 00:08:34,746 Of two black holes merging. 157 00:08:34,748 --> 00:08:37,849 Del pozzo: Virgo has been a great success indeed. 158 00:08:39,553 --> 00:08:45,524 What we are seeing here is the deadly dance of two black holes. 159 00:08:45,526 --> 00:08:47,158 They get closer and closer. 160 00:08:48,362 --> 00:08:50,328 And from here, we can actually tell 161 00:08:50,330 --> 00:08:53,164 That the final object was a black hole. 162 00:08:54,334 --> 00:08:56,768 This whole process that we registered 163 00:08:56,770 --> 00:08:58,904 Lasted a fraction of a second. 164 00:09:02,476 --> 00:09:04,276 Walter's reading is the ripple of an event 165 00:09:04,278 --> 00:09:10,815 That took place one billion years ago in a distant galaxy. 166 00:09:10,817 --> 00:09:14,553 Two black holes approach each other -- 167 00:09:14,555 --> 00:09:18,857 One 25 times more massive than our sun, 168 00:09:18,859 --> 00:09:21,860 The other -- 30. 169 00:09:21,862 --> 00:09:24,396 They enter into a death spiral. 170 00:09:26,633 --> 00:09:28,667 The two black holes accelerate 171 00:09:28,669 --> 00:09:30,802 To almost half the speed of light, 172 00:09:31,905 --> 00:09:36,074 Until finally, they collide, 173 00:09:36,076 --> 00:09:39,945 Leaving behind a single, much heavier black hole. 174 00:09:39,947 --> 00:09:42,847 It takes a billion years for the ripples from this 175 00:09:42,849 --> 00:09:46,484 Black hole merger to reach the virgo detector on earth. 176 00:09:47,988 --> 00:09:50,388 This is a major breakthrough. 177 00:09:50,390 --> 00:09:55,226 Virgo and similar machines in the u.S. Have finally proven 178 00:09:55,228 --> 00:09:59,230 That black holes can grow by merging together. 179 00:09:59,232 --> 00:10:01,099 We were the first ones in history 180 00:10:01,101 --> 00:10:06,104 To be able to see two black holes eating each other 181 00:10:06,106 --> 00:10:09,975 And merging to become a single black hole. 182 00:10:09,977 --> 00:10:12,911 That's incredible, okay. [laughs] 183 00:10:14,281 --> 00:10:16,681 Narrator: And by measuring gravitational waves, 184 00:10:16,683 --> 00:10:18,917 Astronomers get their first taste 185 00:10:18,919 --> 00:10:21,119 Of an immensely powerful new tool 186 00:10:21,121 --> 00:10:24,089 For understanding the cosmos. 187 00:10:24,091 --> 00:10:28,026 Tremblay: Now we have a fundamentally new window in the universe. 188 00:10:28,028 --> 00:10:29,327 That's not collecting light. 189 00:10:29,329 --> 00:10:31,696 That's listening to the music of the cosmos. 190 00:10:31,698 --> 00:10:34,599 And it is an absolutely transformational new way 191 00:10:34,601 --> 00:10:35,900 To look at the universe. 192 00:10:35,902 --> 00:10:38,236 Narrator: So, is it case closed? 193 00:10:38,238 --> 00:10:41,606 Do smaller stellar black holes merge together 194 00:10:41,608 --> 00:10:44,743 To form supermassive black holes? 195 00:10:44,745 --> 00:10:47,579 Unfortunately, it seems unlikely. 196 00:10:47,581 --> 00:10:49,914 And if not, then how did 197 00:10:49,916 --> 00:10:53,051 Supermassive black holes grow so big? 198 00:10:53,053 --> 00:10:57,722 Scientists might be on the verge of an answer. 199 00:11:10,370 --> 00:11:15,373 ♪ 200 00:11:15,375 --> 00:11:18,176 Narrator: Scientists are on a mission to discover 201 00:11:18,178 --> 00:11:21,279 How the monstrous supermassive black holes 202 00:11:21,281 --> 00:11:24,416 That lurk in the centers of galaxies formed. 203 00:11:24,418 --> 00:11:27,619 Some of them are ancient, born when the universe 204 00:11:27,621 --> 00:11:30,855 Was just a few hundred-million years old. 205 00:11:30,857 --> 00:11:33,758 That's far too short a time for billions of smaller 206 00:11:33,760 --> 00:11:37,929 Stellar black holes to have formed and then merged together. 207 00:11:37,931 --> 00:11:39,597 If you start with something that has 208 00:11:39,599 --> 00:11:41,099 Five times the mass of the sun, 209 00:11:41,101 --> 00:11:42,333 How long does it take 210 00:11:42,335 --> 00:11:45,270 To get to a billion times the mass of the sun? 211 00:11:45,272 --> 00:11:47,906 And it turns out, yeah, the age of the universe. 212 00:11:47,908 --> 00:11:49,307 It takes billions of years. 213 00:11:50,343 --> 00:11:52,377 The idea that supermassive black holes 214 00:11:52,379 --> 00:11:56,247 Started off as stellar-mass black holes that then grew 215 00:11:56,249 --> 00:11:57,882 Doesn't seem plausible. 216 00:11:57,884 --> 00:12:00,452 Narrator: So, if supermassive black holes 217 00:12:00,454 --> 00:12:03,354 Couldn't have formed from smaller stellar black holes 218 00:12:03,356 --> 00:12:07,025 Merging together, how did they grow so big? 219 00:12:07,027 --> 00:12:09,828 The leading theory is that the early universe 220 00:12:09,830 --> 00:12:13,064 Must have cooked up a third category of black hole 221 00:12:13,066 --> 00:12:16,101 Smaller than today's supermassive beasts, 222 00:12:16,103 --> 00:12:19,504 But still much bigger than the stellar black holes 223 00:12:19,506 --> 00:12:21,673 Formed by collapsing stars. 224 00:12:21,675 --> 00:12:24,042 There must be another kind of black hole 225 00:12:24,044 --> 00:12:25,610 That we haven't found yet, 226 00:12:25,612 --> 00:12:27,345 A black hole that's kind of in the middle, 227 00:12:27,347 --> 00:12:29,347 Something like maybe a couple thousand times 228 00:12:29,349 --> 00:12:30,415 The mass of the sun. 229 00:12:31,418 --> 00:12:33,818 We call these seed black holes. 230 00:12:33,820 --> 00:12:36,321 Narrator: They're called seed black holes 231 00:12:36,323 --> 00:12:38,289 Because scientists believe that 232 00:12:38,291 --> 00:12:41,326 Supermassive black holes grow from them. 233 00:12:42,863 --> 00:12:44,963 These seeds are much bigger than 234 00:12:44,965 --> 00:12:47,766 The black holes formed by collapsing stars. 235 00:12:47,768 --> 00:12:50,168 So it wouldn't take very many of them 236 00:12:50,170 --> 00:12:54,839 Or very long to merge together and grow supermassive. 237 00:12:54,841 --> 00:12:57,275 The underlying logic here is actually really simple. 238 00:12:57,277 --> 00:12:59,244 If you wanna build a really big black hole, 239 00:12:59,246 --> 00:13:01,679 You need bigger building blocks. 240 00:13:01,681 --> 00:13:05,350 Narrator: If the early universe cooked up these seed black holes, 241 00:13:05,352 --> 00:13:08,353 There should be still plenty of them around today -- 242 00:13:08,355 --> 00:13:11,523 Seed black holes that have yet to be swallowed up 243 00:13:11,525 --> 00:13:13,758 By the supermassive black holes. 244 00:13:15,128 --> 00:13:18,263 And that's a problem, because we can't find them. 245 00:13:18,265 --> 00:13:20,465 They're missing. 246 00:13:20,467 --> 00:13:22,433 We've discovered many black holes, 247 00:13:22,435 --> 00:13:25,203 But they come in these two size categories, 248 00:13:25,205 --> 00:13:27,705 One a few times the mass of the sun, 249 00:13:27,707 --> 00:13:29,541 And the other's millions or billions 250 00:13:29,543 --> 00:13:31,209 Of times the mass of the sun. 251 00:13:31,211 --> 00:13:33,645 What about all the ones that should be in between there? 252 00:13:33,647 --> 00:13:35,814 We haven't seen those. 253 00:13:35,816 --> 00:13:37,916 Thaller: One of the holy grails in astronomy right now 254 00:13:37,918 --> 00:13:39,884 Is to find one of these seed black holes. 255 00:13:39,886 --> 00:13:42,320 If they're not out there, we have to reevaluate 256 00:13:42,322 --> 00:13:45,590 Everything we know about the evolution of the universe. 257 00:13:45,592 --> 00:13:50,428 Narrator: Investigators have yet to find a confirmed seed black hole. 258 00:13:50,430 --> 00:13:53,264 But is that about to change? 259 00:13:53,266 --> 00:13:56,968 Mar mezcua is on the hunt for these middleweight monsters. 260 00:13:56,970 --> 00:14:01,739 Finding black holes in the dark of space is no simple task. 261 00:14:03,677 --> 00:14:06,377 Nothing can escape from a black hole, not even light. 262 00:14:06,379 --> 00:14:08,012 Therefore, black holes are black. 263 00:14:08,014 --> 00:14:09,781 They do not emit light. 264 00:14:09,783 --> 00:14:12,383 So how do we detect them? 265 00:14:12,385 --> 00:14:16,487 Narrator: Black hole hunting requires a special kind of telescope. 266 00:14:18,024 --> 00:14:21,826 Mar comes to medicina observatory in northern Italy. 267 00:14:21,828 --> 00:14:25,230 Here, they don't look at the universe in visible light. 268 00:14:25,232 --> 00:14:27,932 They look at radio waves. 269 00:14:27,934 --> 00:14:30,935 One way to observe black holes is to use radio astronomy. 270 00:14:32,038 --> 00:14:35,373 Using radio telescopes, we get a different view of the universe, 271 00:14:35,375 --> 00:14:38,076 A different view of galaxies and black holes. 272 00:14:40,213 --> 00:14:44,716 Narrator: Radio waves are a form of light humans can't see. 273 00:14:44,718 --> 00:14:46,384 But unlike visible light, 274 00:14:46,386 --> 00:14:49,087 Radio waves emitted by objects in space 275 00:14:49,089 --> 00:14:52,891 Can pierce the dust and gas scattered around the universe. 276 00:14:54,261 --> 00:14:57,762 We can even observe radio waves during the day. 277 00:14:58,798 --> 00:15:02,066 This allows mar to see that something odd is going on 278 00:15:02,068 --> 00:15:06,037 In galaxy ngc 2276, 279 00:15:06,039 --> 00:15:09,173 A galaxy 100 million light years from earth. 280 00:15:10,310 --> 00:15:12,844 Could it be home to a seed black hole? 281 00:15:12,846 --> 00:15:16,547 [dramatic orchestral music] 282 00:15:18,652 --> 00:15:22,253 At first glance, the galaxy doesn't look too special. 283 00:15:23,356 --> 00:15:25,256 So, this here is a very nice image 284 00:15:25,258 --> 00:15:27,825 Taken with the hubble space telescope. 285 00:15:27,827 --> 00:15:29,127 That's the galactic center, 286 00:15:29,129 --> 00:15:32,330 Where the supermassive black hole should reside. 287 00:15:32,332 --> 00:15:34,332 And then these are the spiral arms, 288 00:15:34,334 --> 00:15:36,434 Where lots of stars are being formed. 289 00:15:37,570 --> 00:15:39,203 Narrator: But look closer, and there appears 290 00:15:39,205 --> 00:15:43,675 To be a mysterious dark patch in one of the spiral arms. 291 00:15:43,677 --> 00:15:46,544 So we think that in this darker area here, 292 00:15:48,014 --> 00:15:51,482 There's no dust and there's no gas able to create the stars. 293 00:15:51,484 --> 00:15:54,485 And that's why no stars are being formed. 294 00:15:54,487 --> 00:15:58,323 So something must have cleared the gas. 295 00:15:58,325 --> 00:16:00,491 Narrator: What strange forces can clear out 296 00:16:00,493 --> 00:16:03,127 A huge patch of dust and stars? 297 00:16:04,331 --> 00:16:07,632 Mar looks at the galaxy in radio waves. 298 00:16:07,634 --> 00:16:09,701 She sees something astonishing. 299 00:16:11,071 --> 00:16:12,770 A radio bright spot. 300 00:16:13,940 --> 00:16:16,474 Mezcua: What we are seeing here is radio emission 301 00:16:16,476 --> 00:16:20,144 From a location in the spiral arm of ngc 2276. 302 00:16:21,247 --> 00:16:22,947 The radio emission that we detect 303 00:16:22,949 --> 00:16:26,584 Is located right here in this dark region. 304 00:16:26,586 --> 00:16:32,490 Narrator: Mar thinks this radio bright spot can only be one thing. 305 00:16:32,492 --> 00:16:34,659 Blasting a hole in the side of the galaxy 306 00:16:34,661 --> 00:16:36,694 Reveals the scale of the void. 307 00:16:38,164 --> 00:16:42,767 It's enormous and almost completely devoid of stars. 308 00:16:42,769 --> 00:16:47,772 The reason lies within -- a jet of intense radiation. 309 00:16:47,774 --> 00:16:49,841 Like a galactic blowtorch, 310 00:16:49,843 --> 00:16:53,144 It's blasted away the star-forming gas. 311 00:16:53,146 --> 00:16:55,780 Traveling six light years along the jet 312 00:16:55,782 --> 00:16:57,782 Leads to the heart of the void 313 00:16:57,784 --> 00:17:00,818 And the ultimate source of the radiation -- 314 00:17:00,820 --> 00:17:05,757 A black hole gorging itself on a vortex of cosmic dust. 315 00:17:05,759 --> 00:17:07,792 As it feeds, the black hole 316 00:17:07,794 --> 00:17:10,895 Whips the dust around it into a frenzy, 317 00:17:10,897 --> 00:17:14,665 Blasting out scorching beams of intense radiation. 318 00:17:14,667 --> 00:17:18,036 But could this just be a small stellar black hole 319 00:17:18,038 --> 00:17:21,139 With a mass of a few times that of our sun? 320 00:17:21,141 --> 00:17:23,074 It seems unlikely. 321 00:17:23,076 --> 00:17:24,842 Because of the size of this dark region, 322 00:17:24,844 --> 00:17:27,545 We know that it cannot be a stellar black hole. 323 00:17:27,547 --> 00:17:29,414 It must be something bigger. 324 00:17:29,416 --> 00:17:32,383 Narrator: And if this were a supermassive black hole 325 00:17:32,385 --> 00:17:36,120 Weighing a few million times the mass of the sun, 326 00:17:36,122 --> 00:17:38,589 It would be at the center of its galaxy, 327 00:17:38,591 --> 00:17:40,691 Not here on the outskirts. 328 00:17:40,693 --> 00:17:43,628 Could this be a seed black hole, 329 00:17:43,630 --> 00:17:46,030 The missing link that can help tell us 330 00:17:46,032 --> 00:17:49,233 How supermassive black holes and galaxies form? 331 00:18:02,849 --> 00:18:07,852 ♪ 332 00:18:07,854 --> 00:18:10,621 Narrator: At the medicina observatory in northern Italy, 333 00:18:10,623 --> 00:18:14,292 Astrophysicist mar mezcua could be on the verge 334 00:18:14,294 --> 00:18:15,760 Of a breakthrough discovery. 335 00:18:15,762 --> 00:18:19,497 Using radio telescopes, she looks at galaxy ngc 2276 336 00:18:21,534 --> 00:18:24,168 And sees something remarkable, 337 00:18:24,170 --> 00:18:26,704 A bright spot of intense radiation 338 00:18:26,706 --> 00:18:31,409 That could only be caused by one thing: A black hole. 339 00:18:31,411 --> 00:18:33,978 Could it be a seed black hole? 340 00:18:33,980 --> 00:18:36,481 We have used radio observations of this black hole, 341 00:18:36,483 --> 00:18:38,483 Together with x-ray measurements, 342 00:18:38,485 --> 00:18:40,218 To estimate the black hole mass. 343 00:18:40,220 --> 00:18:42,854 And we find that this black hole has a mass 344 00:18:42,856 --> 00:18:46,691 Of more than 10,000 times the mass of the sun. 345 00:18:46,693 --> 00:18:48,326 Narrator: That puts this black hole 346 00:18:48,328 --> 00:18:50,862 Firmly in the middleweight division. 347 00:18:50,864 --> 00:18:54,732 It looks like this really is a seed black hole. 348 00:18:57,670 --> 00:18:59,070 This is a source that warrants 349 00:18:59,072 --> 00:19:01,005 Really urgent observational follow-up. 350 00:19:01,007 --> 00:19:04,142 Because it very well may be a seed black hole. 351 00:19:04,144 --> 00:19:05,576 And this is really cool, 352 00:19:05,578 --> 00:19:09,680 Because we don't have really firm evidence of these things. 353 00:19:09,682 --> 00:19:11,215 Narrator: If mar is right, 354 00:19:11,217 --> 00:19:14,152 Seed black holes really do exist. 355 00:19:14,154 --> 00:19:16,587 It's a huge breakthrough in our understanding 356 00:19:16,589 --> 00:19:20,725 Of how supermassive black holes and galaxies grow. 357 00:19:20,727 --> 00:19:23,494 But it's not a confirmed find yet, 358 00:19:23,496 --> 00:19:27,198 And other scientists are hot on her heels. 359 00:19:27,200 --> 00:19:29,901 At mcdonald observatory in texas, 360 00:19:29,903 --> 00:19:31,836 Eva noyola is on the trail 361 00:19:31,838 --> 00:19:33,871 Of another middleweight contender. 362 00:19:35,008 --> 00:19:37,008 Her potential seed black hole 363 00:19:37,010 --> 00:19:39,744 Sits right in our galaxy's backyard. 364 00:19:39,746 --> 00:19:42,680 Eva investigates star clusters. 365 00:19:43,883 --> 00:19:46,150 Star clusters are these collection of stars 366 00:19:46,152 --> 00:19:49,020 That are gravitating around each other independently, 367 00:19:49,022 --> 00:19:50,821 And they tend to orbit around galaxies. 368 00:19:50,823 --> 00:19:55,760 So they can go from 10,000 stars only to millions of stars. 369 00:19:57,330 --> 00:20:01,399 Narrator: Around 200 large star clusters orbit the milky way, 370 00:20:01,401 --> 00:20:05,670 And eva thinks inside them, we may find seed black holes. 371 00:20:06,773 --> 00:20:10,241 Eva has found one cluster, omega centauri, 372 00:20:10,243 --> 00:20:12,877 That behaves particularly strangely. 373 00:20:13,846 --> 00:20:17,682 Omega centauri is the largest star cluster around the galaxy. 374 00:20:17,684 --> 00:20:19,550 It's roughly a spherical shape, 375 00:20:19,552 --> 00:20:22,186 And it's about two million stars. 376 00:20:22,188 --> 00:20:24,355 The density of stars is so high 377 00:20:24,357 --> 00:20:25,990 That compared to our solar neighborhood, 378 00:20:25,992 --> 00:20:28,259 The stars are a thousand times closer. 379 00:20:28,261 --> 00:20:30,094 That's where things are harder to measure, 380 00:20:30,096 --> 00:20:31,963 Because there are so many stars near to each other, 381 00:20:31,965 --> 00:20:34,065 But it's very hard to tell them apart. 382 00:20:35,501 --> 00:20:37,635 Narrator: Eva thinks that a monster lurks 383 00:20:37,637 --> 00:20:40,871 At the heart of this dense cluster of stars. 384 00:20:40,873 --> 00:20:43,474 There's something creating gravitational pull, 385 00:20:43,476 --> 00:20:45,376 But it's not visible. 386 00:20:45,378 --> 00:20:46,844 Right there in the middle. [chuckles] 387 00:20:48,381 --> 00:20:50,248 Narrator: Eva carefully observes 388 00:20:50,250 --> 00:20:54,185 How the stars inside the cluster move through space 389 00:20:54,187 --> 00:20:56,887 And finds something astonishing. 390 00:20:56,889 --> 00:20:59,890 Noyola: The speed of the stars in the very center of the cluster 391 00:20:59,892 --> 00:21:03,094 Is about four times faster than the speed at the outskirts. 392 00:21:03,096 --> 00:21:04,662 So it's a pretty big increase. 393 00:21:05,732 --> 00:21:09,066 Narrator: Something small but with a huge amount of gravity 394 00:21:09,068 --> 00:21:12,370 Seems to be whipping the stars in the cluster's center 395 00:21:12,372 --> 00:21:13,971 Into a frenzy. 396 00:21:13,973 --> 00:21:16,374 But no matter how hard eva looks, 397 00:21:16,376 --> 00:21:18,709 She can't see this object. 398 00:21:18,711 --> 00:21:21,112 Noyola: You have a very massive, very compact object 399 00:21:21,114 --> 00:21:23,080 That does not give off light. 400 00:21:23,082 --> 00:21:27,118 This thing essentially jumped at me. 401 00:21:27,120 --> 00:21:30,021 Narrator: If eva's right, for billions of years, 402 00:21:30,023 --> 00:21:33,724 Omega centauri has been hiding a dark secret. 403 00:21:34,827 --> 00:21:39,163 Deep inside, stars hurdle through space on overdrive, 404 00:21:39,165 --> 00:21:41,999 Many times faster than they should. 405 00:21:42,001 --> 00:21:44,769 Only a dense object with immense gravity 406 00:21:44,771 --> 00:21:48,272 Can pull stars into orbits like this -- 407 00:21:48,274 --> 00:21:50,408 A black hole. 408 00:21:50,410 --> 00:21:54,945 And judging by the sheer speeds of the stars in its grasp, 409 00:21:54,947 --> 00:21:58,382 This is no small stellar black hole. 410 00:21:58,384 --> 00:22:01,285 It's a seed black hole. 411 00:22:01,287 --> 00:22:02,753 My heart rate just elevated 412 00:22:02,755 --> 00:22:04,522 Because it was so exciting to see. 413 00:22:04,524 --> 00:22:07,358 It was very clear that there was something very interesting there. 414 00:22:07,360 --> 00:22:09,393 Narrator: This seed isn't feeding, 415 00:22:09,395 --> 00:22:13,030 So it's not producing radio waves. 416 00:22:13,032 --> 00:22:16,901 But by measuring the speeds of the stars orbiting around it, 417 00:22:16,903 --> 00:22:20,037 Eva can still calculate how big it is. 418 00:22:20,039 --> 00:22:22,740 Noyola: The size of the black hole that is the best fit 419 00:22:22,742 --> 00:22:26,310 Is 50,000 times the mass of the sun. 420 00:22:26,312 --> 00:22:29,313 It is right between the little stellar-mass black holes, 421 00:22:29,315 --> 00:22:30,848 Which are a lot smaller, 422 00:22:30,850 --> 00:22:32,083 And the supermassive black holes, 423 00:22:32,085 --> 00:22:33,918 Which are much, much bigger. 424 00:22:33,920 --> 00:22:34,919 The fact that it's in the middle 425 00:22:34,921 --> 00:22:37,355 Is what makes it a seed black hole. 426 00:22:37,357 --> 00:22:41,125 Narrator: Weighing in at 50,000 times the mass of the sun, 427 00:22:41,127 --> 00:22:42,893 This is five times heavier 428 00:22:42,895 --> 00:22:45,162 Than mar mezcua's black hole 429 00:22:45,164 --> 00:22:49,433 But still firmly within the seed black hole weight division. 430 00:22:49,435 --> 00:22:52,636 But what makes eva's seed even more intriguing 431 00:22:52,638 --> 00:22:55,473 Is the cluster of stars that hang around it 432 00:22:55,475 --> 00:22:57,208 Like moths around a flame. 433 00:22:58,978 --> 00:23:02,613 Could this entourage of stars be a clue to how galaxies 434 00:23:02,615 --> 00:23:06,317 Like the milky way first formed in the early universe? 435 00:23:06,319 --> 00:23:10,221 And can this strange glow from the galactic center 436 00:23:10,223 --> 00:23:13,591 Reveal that our own supermassive black hole 437 00:23:13,593 --> 00:23:17,328 Is still growing fat on a diet of these seeds? 438 00:23:17,330 --> 00:23:21,565 Oluseyi: These seed black holes may exist in our galaxy today. 439 00:23:21,567 --> 00:23:24,435 Maybe they're in our own cosmic backyard. 440 00:23:24,437 --> 00:23:32,042 ♪ 441 00:23:38,518 --> 00:23:44,755 ♪ 442 00:23:44,757 --> 00:23:48,025 Narrator: Astronomers are on the verge of a breakthrough. 443 00:23:48,027 --> 00:23:50,027 They've found evidence that middleweight 444 00:23:50,029 --> 00:23:53,931 Seed black holes really do exist. 445 00:23:53,933 --> 00:23:56,400 And one seed black hole in particular 446 00:23:56,402 --> 00:24:00,137 Has astronomers excited, because clustered around it 447 00:24:00,139 --> 00:24:02,907 Is a bunch of stars, like a mini galaxy. 448 00:24:04,744 --> 00:24:08,579 It hints at an astonishing history for these middleweights. 449 00:24:08,581 --> 00:24:10,714 Seed black holes and the stars they drag with them 450 00:24:10,716 --> 00:24:12,883 Could have helped build 451 00:24:12,885 --> 00:24:16,320 The vast collections of stars we call galaxies. 452 00:24:19,559 --> 00:24:21,892 A clue to their galaxy-building role 453 00:24:21,894 --> 00:24:25,095 Lies inside the central bulge of the milky way. 454 00:24:26,265 --> 00:24:28,032 The stars inside the bulge 455 00:24:28,034 --> 00:24:30,568 Resemble those in the star clusters 456 00:24:30,570 --> 00:24:33,471 Thought to be home to seed black holes. 457 00:24:33,473 --> 00:24:35,473 Noyola: The population at the center of galaxies 458 00:24:35,475 --> 00:24:37,741 In galactic bulges really matches 459 00:24:37,743 --> 00:24:40,778 Very well the population of the star clusters. 460 00:24:40,780 --> 00:24:44,014 So we know that a lot of the bulge is made of those stars. 461 00:24:45,017 --> 00:24:46,450 Narrator: If the centers of galaxies 462 00:24:46,452 --> 00:24:49,119 Are largely built from these star clusters, 463 00:24:49,121 --> 00:24:53,357 This suggests an extraordinary role for seed black holes. 464 00:24:54,861 --> 00:24:56,460 13 billion years ago, 465 00:24:56,462 --> 00:24:59,430 The universe didn't have large spiral galaxies 466 00:24:59,432 --> 00:25:00,764 Like the milky way. 467 00:25:00,766 --> 00:25:04,869 Instead, it may have been filled with seed black holes, 468 00:25:04,871 --> 00:25:07,938 Each with a disorganized mass of stars around it. 469 00:25:09,442 --> 00:25:13,744 It's from these ingredients that scientists think galaxies grew. 470 00:25:15,014 --> 00:25:17,381 Seed black holes could act as anchors 471 00:25:17,383 --> 00:25:19,950 For the stars that swarm around them, 472 00:25:19,952 --> 00:25:23,487 And those anchors could find one another in the void of space 473 00:25:23,489 --> 00:25:25,689 And coalesce to form a larger galaxy. 474 00:25:27,793 --> 00:25:30,227 Narrator: With seed black holes as the catalyst, 475 00:25:30,229 --> 00:25:32,830 We can imagine how the milky way formed. 476 00:25:35,101 --> 00:25:37,434 Two star clusters collide. 477 00:25:37,436 --> 00:25:42,706 Their stars are pulled out of orbit and chaotically mix. 478 00:25:42,708 --> 00:25:47,044 In the thick of the action, two seed black holes face off, 479 00:25:47,046 --> 00:25:50,180 Circling each other in a deadly dance. 480 00:25:52,552 --> 00:25:58,155 They finally fuse to form a bigger black hole. 481 00:25:58,157 --> 00:26:00,958 The increased gravity sucks in more material 482 00:26:00,960 --> 00:26:03,494 And pulls more star clusters into the fray, 483 00:26:03,496 --> 00:26:06,697 Until eventually the seeds had ballooned... 484 00:26:09,602 --> 00:26:11,802 ...Into a supermassive black hole. 485 00:26:13,673 --> 00:26:17,174 And around this monster, the stars from those clusters 486 00:26:17,176 --> 00:26:20,177 Helped to form our galaxy, the milky way. 487 00:26:24,317 --> 00:26:26,684 I find it amazing that these little star clusters 488 00:26:26,686 --> 00:26:28,786 That are old and tiny 489 00:26:28,788 --> 00:26:31,522 End up being these fantastic archeological objects 490 00:26:31,524 --> 00:26:33,290 That end up being the building blocks 491 00:26:33,292 --> 00:26:36,393 Of the galaxies that we observe everywhere in the universe. 492 00:26:36,395 --> 00:26:38,529 Narrator: The theory that seed black holes 493 00:26:38,531 --> 00:26:41,465 Helped build the milky way is an exciting one. 494 00:26:41,467 --> 00:26:44,768 But where's the proof? 495 00:26:44,770 --> 00:26:47,738 Scientists scour the hearts of galaxies 496 00:26:47,740 --> 00:26:50,341 For evidence of seed black holes. 497 00:26:50,343 --> 00:26:54,478 The holy grail is now to find stray seed black holes 498 00:26:54,480 --> 00:26:57,081 That are still in the process of merging. 499 00:27:00,152 --> 00:27:04,021 In southern arizona sits a unique set of telescopes. 500 00:27:05,958 --> 00:27:07,124 This is veritas. 501 00:27:10,696 --> 00:27:13,297 Veritas is made up of four dishes, 502 00:27:13,299 --> 00:27:18,102 Each 40 feet across with 350 hexagonal mirrors apiece. 503 00:27:20,006 --> 00:27:21,905 These bizarre-looking instruments 504 00:27:21,907 --> 00:27:24,074 Are designed to look for a special form 505 00:27:24,076 --> 00:27:27,244 Of intense, high-energy light called gamma rays. 506 00:27:29,448 --> 00:27:32,750 John quinn believes gamma ray telescopes like these 507 00:27:32,752 --> 00:27:36,787 Could offer up a brand-new way to hunt for seed black holes. 508 00:27:39,625 --> 00:27:43,293 Veritas is a ground-based gamma ray observatory. 509 00:27:43,295 --> 00:27:46,363 It lets us study sources of what are known 510 00:27:46,365 --> 00:27:48,232 As very high-energy gamma rays, 511 00:27:48,234 --> 00:27:51,535 Gamma rays a million-million times more energetic than light, 512 00:27:51,537 --> 00:27:53,604 Way higher than anything we can produce 513 00:27:53,606 --> 00:27:56,106 In any laboratory on earth. 514 00:27:56,108 --> 00:27:57,541 It leaves a very sharp image 515 00:27:57,543 --> 00:27:58,876 Of the gamma rays when they come in. 516 00:28:01,180 --> 00:28:03,981 Narrator: Gamma rays are light waves on steroids 517 00:28:03,983 --> 00:28:10,354 Created by the most extreme objects in the cosmos -- 518 00:28:10,356 --> 00:28:12,656 Violently spinning pulsars... 519 00:28:14,193 --> 00:28:16,093 ...Exploding supernovae... 520 00:28:20,032 --> 00:28:23,834 ...And enormous quasars... 521 00:28:23,836 --> 00:28:25,069 All fire out gamma rays. 522 00:28:27,506 --> 00:28:29,940 And when these high-energy waves hit earth, 523 00:28:31,544 --> 00:28:33,510 They tear through the atmosphere, 524 00:28:33,512 --> 00:28:35,713 Creating bursts of blue light. 525 00:28:37,416 --> 00:28:40,250 These bursts are normally invisible, 526 00:28:40,252 --> 00:28:42,286 But veritas can see them. 527 00:28:45,224 --> 00:28:47,257 Here, we're seeing various events. 528 00:28:48,661 --> 00:28:52,763 Each change you see is 2,000 millionths of a second. 529 00:28:52,765 --> 00:28:54,665 We have to use specialized detectors, 530 00:28:54,667 --> 00:28:57,801 High-speed electronics to detect these. 531 00:28:57,803 --> 00:28:59,236 Narrator: And gamma ray astronomy 532 00:28:59,238 --> 00:29:03,707 Has thrown scientists a stunning curve ball, 533 00:29:03,709 --> 00:29:05,642 One that could provide the proof 534 00:29:05,644 --> 00:29:09,747 That seed black holes helped build the galaxy. 535 00:29:09,749 --> 00:29:13,283 Investigators discovered that the center of our galaxy 536 00:29:13,285 --> 00:29:16,220 Emits an unexplained gamma ray glow. 537 00:29:17,857 --> 00:29:20,858 This is the entire gamma ray sky. 538 00:29:20,860 --> 00:29:23,627 The plane of the galaxy is along the center, 539 00:29:23,629 --> 00:29:26,697 And we can see the center of the galaxy here. 540 00:29:26,699 --> 00:29:28,766 Narrator: This central region fires out 541 00:29:28,768 --> 00:29:30,934 Many more gamma rays than it should. 542 00:29:33,806 --> 00:29:36,807 And we currently don't understand what is causing this. 543 00:29:37,910 --> 00:29:40,744 Plait: Gamma rays are a form of light that's pretty hard to produce. 544 00:29:40,746 --> 00:29:43,747 You need to have a huge energetic source to make them. 545 00:29:43,749 --> 00:29:45,716 So we expected to see some coming 546 00:29:45,718 --> 00:29:46,917 From the center of the galaxy. 547 00:29:46,919 --> 00:29:49,286 That's a lot of activity going on there. 548 00:29:49,288 --> 00:29:52,222 The problem is we're seeing too many. 549 00:29:52,224 --> 00:29:54,458 Our milky way is overproducing. 550 00:29:54,460 --> 00:29:57,461 There's an excess of gamma rays coming from there. 551 00:29:57,463 --> 00:29:58,328 Why? 552 00:30:01,033 --> 00:30:03,100 Narrator: Could thousands of seed black holes 553 00:30:03,102 --> 00:30:05,102 Orbit the supermassive black hole 554 00:30:05,104 --> 00:30:06,770 At the heart of the milky way, 555 00:30:06,772 --> 00:30:10,007 Emitting gamma rays as they circle the galactic center? 556 00:30:11,243 --> 00:30:14,678 Quinn: It is possible that some of the gamma ray events 557 00:30:14,680 --> 00:30:18,549 That we're seeing are produced from seed black holes 558 00:30:18,551 --> 00:30:20,484 In the vicinity of the galactic center. 559 00:30:21,587 --> 00:30:24,421 Narrator: But how can black holes produce radiation 560 00:30:24,423 --> 00:30:27,558 If nothing ever escapes their gravitational pull, 561 00:30:27,560 --> 00:30:29,927 Not even light? 562 00:30:29,929 --> 00:30:34,298 The answer could lie in the cosmic debris that they feed on. 563 00:30:34,300 --> 00:30:37,134 Matter is attracted towards the seed black hole 564 00:30:37,136 --> 00:30:38,969 By its enormous gravity, 565 00:30:38,971 --> 00:30:40,838 And as the black hole spins, 566 00:30:40,840 --> 00:30:43,740 Its gravity whips the matter into a frenzy, 567 00:30:43,742 --> 00:30:46,143 Generating huge amounts of energy, 568 00:30:46,145 --> 00:30:49,746 Which blasts out from the area around the black hole 569 00:30:49,748 --> 00:30:51,982 In a bright beacon of radiation 570 00:30:51,984 --> 00:30:54,685 And perhaps even gamma rays. 571 00:30:54,687 --> 00:30:58,455 Could this be the explanation for the mysterious glow 572 00:30:58,457 --> 00:31:01,491 Coming from the heart of the milky way? 573 00:31:01,493 --> 00:31:04,061 Could it be seed black holes? 574 00:31:04,063 --> 00:31:06,830 Gamma rays could be the observable beacons 575 00:31:06,832 --> 00:31:09,066 For otherwise unobservable seed black holes. 576 00:31:09,068 --> 00:31:12,536 And that would be an absolutely transformational discovery. 577 00:31:12,538 --> 00:31:17,741 ♪ 578 00:31:24,350 --> 00:31:29,253 ♪ 579 00:31:29,255 --> 00:31:32,055 Narrator: If the mysteriously glowing galactic center 580 00:31:32,057 --> 00:31:36,393 At the heart of our milky way is thanks to seed black holes, 581 00:31:36,395 --> 00:31:39,029 It would be an astonishing discovery. 582 00:31:39,031 --> 00:31:40,097 It would tell us 583 00:31:40,099 --> 00:31:43,233 Our supermassive black hole isn't alone. 584 00:31:43,235 --> 00:31:46,169 There could be seed black holes orbiting it -- 585 00:31:46,171 --> 00:31:48,238 Seeds that, billions of years ago, 586 00:31:48,240 --> 00:31:51,541 Delivered the stars that helped build the milky way. 587 00:31:51,543 --> 00:31:53,911 That would really help fill in the story 588 00:31:53,913 --> 00:31:56,847 Fill in the puzzle of how structure in the universe forms. 589 00:31:58,150 --> 00:31:59,716 Narrator: It would be the final proof 590 00:31:59,718 --> 00:32:03,487 That seed black holes helped build our galaxy. 591 00:32:03,489 --> 00:32:05,856 We may even be lucky enough to find that 592 00:32:05,858 --> 00:32:11,261 Our supermassive black hole is still merging with these seeds. 593 00:32:11,263 --> 00:32:15,132 There could be see black holes still in our galaxy today. 594 00:32:15,134 --> 00:32:19,469 Our supermassive black hole may still be feeding on them. 595 00:32:19,471 --> 00:32:21,538 Narrator: And with each collision, 596 00:32:21,540 --> 00:32:25,275 Our supermassive black hole becomes even more massive. 597 00:32:25,277 --> 00:32:33,583 ♪ 598 00:32:33,585 --> 00:32:35,953 Seed black holes could turn out to be 599 00:32:35,955 --> 00:32:39,356 The most important objects in the universe -- 600 00:32:39,358 --> 00:32:41,191 A cosmic game changer. 601 00:32:43,796 --> 00:32:46,797 But one mystery remains unsolved. 602 00:32:48,434 --> 00:32:51,301 If these seed black holes are so important 603 00:32:51,303 --> 00:32:53,971 To the story of our universe, 604 00:32:53,973 --> 00:32:55,772 Where did they come from? 605 00:32:59,611 --> 00:33:04,014 In austin, texas, volker bromm knows how difficult it is 606 00:33:04,016 --> 00:33:05,615 To make seed black holes. 607 00:33:06,685 --> 00:33:11,321 That's because volker tries to make his own seed black holes 608 00:33:11,323 --> 00:33:14,825 Inside this vast supercomputer, stampede. 609 00:33:16,095 --> 00:33:18,662 What we see here is one of the most powerful 610 00:33:18,664 --> 00:33:21,264 Supercomputers on planet earth. 611 00:33:21,266 --> 00:33:25,035 Supercomputers like this allow us to basically take 612 00:33:25,037 --> 00:33:28,305 The laws of nature and create a sophisticated computer code 613 00:33:28,307 --> 00:33:31,708 And then let the computer advance the universe 614 00:33:31,710 --> 00:33:34,978 Over billions of years in time. 615 00:33:34,980 --> 00:33:38,015 Narrator: In short, volker is creating a simulation 616 00:33:38,017 --> 00:33:41,651 Of the early universe inside a computer. 617 00:33:41,653 --> 00:33:43,153 He wants to investigate 618 00:33:43,155 --> 00:33:47,691 How nature could've cooked up these crucial seed black holes. 619 00:33:47,693 --> 00:33:49,860 A few million years after the big bang, 620 00:33:49,862 --> 00:33:52,329 We had a very boring universe. 621 00:33:52,331 --> 00:33:54,698 What cosmologists call the dark ages. 622 00:33:56,101 --> 00:33:59,503 In the dark ages, there were no sources of light -- 623 00:33:59,505 --> 00:34:02,839 No stars, no galaxies, no black holes. 624 00:34:02,841 --> 00:34:07,244 Narrator: The early universe contained simple clouds of gas. 625 00:34:07,246 --> 00:34:10,614 Volker suspects these giant clouds collapsed 626 00:34:10,616 --> 00:34:15,352 To form the biggest stars the universe has ever seen, 627 00:34:15,354 --> 00:34:20,257 Perhaps hundreds of thousands of times more massive than our sun. 628 00:34:20,259 --> 00:34:23,193 These supergiant stars quickly collapsed 629 00:34:23,195 --> 00:34:26,730 To form seed black holes, 630 00:34:26,732 --> 00:34:28,899 But volker's early simulations 631 00:34:28,901 --> 00:34:30,767 Reveal a problem with the theory. 632 00:34:30,769 --> 00:34:33,603 His virtual stars always explode 633 00:34:33,605 --> 00:34:36,473 Before they grow big enough to form a seed black hole. 634 00:34:40,612 --> 00:34:43,980 So here we see a massive star dying, exploding, 635 00:34:43,982 --> 00:34:47,384 Putting in a bubble of high-energy radiation. 636 00:34:48,787 --> 00:34:51,455 This energy input basically drives the gas out again. 637 00:34:52,791 --> 00:34:55,992 And this limits the ability of the gas to collapse 638 00:34:55,994 --> 00:34:59,262 And eventually to end up in a black hole. 639 00:34:59,264 --> 00:35:02,966 Narrator: The virtual stars run out of fuel too quickly and explode. 640 00:35:04,803 --> 00:35:07,237 Bromm: Stars are producers of energy. 641 00:35:07,239 --> 00:35:09,005 They eventually explode, 642 00:35:09,007 --> 00:35:12,742 And they create outward-acting pressure. 643 00:35:12,744 --> 00:35:17,080 Narrator: The explosions stop the gas cloud collapsing further, 644 00:35:17,082 --> 00:35:19,950 And although the dying stars in the simulation 645 00:35:19,952 --> 00:35:21,852 Do form black holes, 646 00:35:21,854 --> 00:35:24,321 They're much smaller than the seed black holes 647 00:35:24,323 --> 00:35:26,857 That helped build the galaxies we see today. 648 00:35:28,494 --> 00:35:30,360 Volker needs a new recipe, 649 00:35:30,362 --> 00:35:32,896 One that'll make an enormous cloud of gas 650 00:35:32,898 --> 00:35:35,599 Collapse to form a single massive star, 651 00:35:35,601 --> 00:35:37,634 Not thousands of smaller ones. 652 00:35:40,205 --> 00:35:41,872 It's possible that in the early universe 653 00:35:41,874 --> 00:35:44,841 Conditions were very different. 654 00:35:44,843 --> 00:35:48,044 Instead of clouds forming beautiful little star clusters, 655 00:35:48,046 --> 00:35:53,250 Giant clouds of dust and gas all collapsed at once. 656 00:35:53,252 --> 00:35:55,952 If conditions are just right, that gas can collapse 657 00:35:55,954 --> 00:35:58,722 All the way down into a very massive seed. 658 00:35:58,724 --> 00:36:01,324 Narrator: But what are these conditions? 659 00:36:01,326 --> 00:36:04,861 Volker realizes that there is a magic ingredient 660 00:36:04,863 --> 00:36:07,764 That could allow seed black holes to form. 661 00:36:07,766 --> 00:36:13,770 ♪ 662 00:36:20,245 --> 00:36:26,316 ♪ 663 00:36:26,318 --> 00:36:29,719 Narrator: Cosmologists believe the galaxies we see today 664 00:36:29,721 --> 00:36:32,556 And the supermassive black holes at their hearts 665 00:36:32,558 --> 00:36:34,791 Were formed in the early universe 666 00:36:34,793 --> 00:36:38,094 By middleweight seed black holes merging together, 667 00:36:38,096 --> 00:36:40,997 But how did these seed black holes form? 668 00:36:40,999 --> 00:36:43,500 It might come down to one ingredient. 669 00:36:43,502 --> 00:36:46,636 The mysterious substance -- dark matter. 670 00:36:46,638 --> 00:36:49,239 We now understand that galaxies are really dominated 671 00:36:49,241 --> 00:36:51,274 By a form of matter we can't see. 672 00:36:51,276 --> 00:36:52,876 We know it's there by its gravity, 673 00:36:52,878 --> 00:36:54,544 But there's no other signal from it at all. 674 00:36:54,546 --> 00:36:56,079 It's what we call dark matter. 675 00:36:58,350 --> 00:37:01,151 Narrator: Dark matter, despite being invisible, 676 00:37:01,153 --> 00:37:04,654 Could allow seed black holes to form 677 00:37:04,656 --> 00:37:07,257 Because one thing we do know about dark matter 678 00:37:07,259 --> 00:37:09,659 Is that it has a gravitational pull. 679 00:37:09,661 --> 00:37:10,994 The really interesting spots 680 00:37:10,996 --> 00:37:14,397 Are where we have these bright patches. 681 00:37:14,399 --> 00:37:17,167 This is where dark matter has assembled, 682 00:37:17,169 --> 00:37:19,936 And the dark matter then provides gravity. 683 00:37:19,938 --> 00:37:24,140 And this gravity is able to attract gas that is quite hot. 684 00:37:26,745 --> 00:37:28,845 Narrator: Volker runs new simulations. 685 00:37:29,948 --> 00:37:31,581 He fine tunes the conditions 686 00:37:31,583 --> 00:37:35,285 To produce a new virtual universe, 687 00:37:35,287 --> 00:37:38,521 And inside this universe, the pull of dark matter 688 00:37:38,523 --> 00:37:42,325 Overcomes the energy that had previously prevented collapse. 689 00:37:43,395 --> 00:37:45,562 Here we see primordial gas 690 00:37:45,564 --> 00:37:50,867 Falling into the center of the dark matter structure, 691 00:37:50,869 --> 00:37:52,869 And the gravity of the dark matter is so strong 692 00:37:52,871 --> 00:37:55,739 That it can overcome all opposing forces. 693 00:37:57,809 --> 00:38:00,343 Narrator: As more and more gas rushes in, 694 00:38:00,345 --> 00:38:05,982 Volker's simulation produces a huge spinning cosmic tornado. 695 00:38:05,984 --> 00:38:09,019 And this motion allows the gas to be funneled, 696 00:38:09,021 --> 00:38:11,621 To be concentrated in the center. 697 00:38:11,623 --> 00:38:14,324 Narrator: And over time, the tornado grows. 698 00:38:15,894 --> 00:38:17,827 We start with 10 times the mass of the sun. 699 00:38:17,829 --> 00:38:20,597 Eventually it goes to 100 times, a 1,000 times, 700 00:38:20,599 --> 00:38:23,333 100,000 times the mass of the sun. 701 00:38:24,670 --> 00:38:26,269 It was not clear that this would be possible 702 00:38:26,271 --> 00:38:29,839 And we was rather, in awe if you like. 703 00:38:29,841 --> 00:38:31,107 In a way, it's so beautiful 704 00:38:31,109 --> 00:38:33,810 That you almost are tempted to fall in love with it. 705 00:38:33,812 --> 00:38:37,213 Narrator: When so much gas funnels into one point in space, 706 00:38:37,215 --> 00:38:41,084 You can create a star like nothing we've ever seen before. 707 00:38:42,421 --> 00:38:45,322 If the simulation is right, in the early universe 708 00:38:45,324 --> 00:38:50,493 Dark matter filaments draw cosmic gas into colossal clouds 709 00:38:50,495 --> 00:38:52,962 Bigger than a galaxy. 710 00:38:52,964 --> 00:38:56,232 Inside the clouds, the temperature's rocket 711 00:38:56,234 --> 00:38:59,369 Until conditions are so extreme 712 00:38:59,371 --> 00:39:02,172 That in the center, colossal blue stars 713 00:39:02,174 --> 00:39:05,875 Maybe 100,000 times bigger than the sun 714 00:39:05,877 --> 00:39:08,345 Burst into life. 715 00:39:08,347 --> 00:39:11,548 But they consume fuel at hellish speeds, 716 00:39:11,550 --> 00:39:13,817 And their cores begin to collapse. 717 00:39:15,053 --> 00:39:17,053 A colossal quantity of material 718 00:39:17,055 --> 00:39:21,858 Crushes down to a point in space... 719 00:39:21,860 --> 00:39:25,395 Creating an enormous seed black hole. 720 00:39:26,965 --> 00:39:31,034 If we have a lot of gas that's in the right configuration 721 00:39:31,036 --> 00:39:34,371 Allowing it to all fall together in just the right way 722 00:39:34,373 --> 00:39:37,474 That it gets small enough, then it would turn into 723 00:39:37,476 --> 00:39:40,443 A black hole of absolutely any size that you want. 724 00:39:40,445 --> 00:39:43,179 So the black hole is instead of being born an infant 725 00:39:43,181 --> 00:39:45,081 It's like being born an adolescent. 726 00:39:45,083 --> 00:39:47,117 It's already very massive. 727 00:39:47,119 --> 00:39:51,421 This can put into place a black hole in one go 728 00:39:51,423 --> 00:39:54,391 Already with a mass of about a 100,000 times 729 00:39:54,393 --> 00:39:56,159 The mass of the sun, maybe up to a million. 730 00:39:57,295 --> 00:40:00,830 Those conditions were really very rare. 731 00:40:00,832 --> 00:40:05,135 And they only happened in select regions in the universe. 732 00:40:05,137 --> 00:40:09,139 And it's almost, you could say, a kind of cosmic miracle. 733 00:40:09,141 --> 00:40:10,607 Narrator: If volker's right, 734 00:40:10,609 --> 00:40:12,976 The seed black holes we find today 735 00:40:12,978 --> 00:40:16,179 Are almost as old as the universe itself -- 736 00:40:16,181 --> 00:40:20,817 The last remaining survivors of an ancient breed of objects. 737 00:40:23,855 --> 00:40:26,489 Tremblay: They could be relics of a very, very, very, 738 00:40:26,491 --> 00:40:29,159 Narrow window of time in the very early universe, 739 00:40:29,161 --> 00:40:31,327 Which means they would be very old, right? 740 00:40:31,329 --> 00:40:32,762 Way older than we think. 741 00:40:33,932 --> 00:40:35,799 Narrator: And their brothers and sisters merge 742 00:40:35,801 --> 00:40:40,303 To help build the supermassive black holes we see today, 743 00:40:40,305 --> 00:40:43,473 Helping create the galaxy we call home 744 00:40:43,475 --> 00:40:47,477 And bringing structure to the universe. 745 00:40:47,479 --> 00:40:50,814 With this formation theory for seed black holes, 746 00:40:50,816 --> 00:40:53,183 The story is complete. 747 00:40:54,719 --> 00:40:58,254 The huge seed black holes that form from the gas clouds 748 00:40:58,256 --> 00:41:02,025 In the early universe gather stars around them. 749 00:41:02,027 --> 00:41:05,428 These giant seeds merge and feed 750 00:41:05,430 --> 00:41:09,165 To grow into the monstrous supermassive black holes 751 00:41:09,167 --> 00:41:12,268 That hold billions of stars in orbit, 752 00:41:12,270 --> 00:41:15,138 Ultimately giving us giant galaxies 753 00:41:15,140 --> 00:41:17,307 Like our home, the milky way. 754 00:41:19,311 --> 00:41:22,212 In a way, the only reason you're sitting here right now 755 00:41:22,214 --> 00:41:24,614 Is that seed black holes, a long time ago, 756 00:41:24,616 --> 00:41:26,015 Gathered the material 757 00:41:26,017 --> 00:41:28,418 To make galaxy and star formation possible. 758 00:41:28,420 --> 00:41:31,321 Narrator: We may not have a confirmed seed yet, 759 00:41:31,323 --> 00:41:33,490 But scientists are close. 760 00:41:33,492 --> 00:41:37,227 There's gonna come a time when we have sort of the smoking gun. 761 00:41:37,229 --> 00:41:39,863 And it's like, "here it is. Here is a seed black hole." 762 00:41:39,865 --> 00:41:42,499 And when we do that, that's fantastic, 763 00:41:42,501 --> 00:41:44,000 Because that is a puzzle piece 764 00:41:44,002 --> 00:41:47,604 That goes into the jigsaw puzzle of the universe 765 00:41:47,606 --> 00:41:49,639 And makes a more complete picture 766 00:41:49,641 --> 00:41:51,407 Of what we know is out there. 767 00:41:51,409 --> 00:41:52,575 That's pretty exciting. 768 00:41:55,113 --> 00:41:56,446 Think about how much a breakthrough 769 00:41:56,448 --> 00:41:57,780 That moment will be. 770 00:41:57,782 --> 00:41:59,549 We have based our entire idea 771 00:41:59,551 --> 00:42:01,951 About how galaxies form, how stars form, 772 00:42:01,953 --> 00:42:04,921 Eventually how planets and you and I form on the idea that 773 00:42:04,923 --> 00:42:07,824 Seed black holes were there in the distant past, 774 00:42:07,826 --> 00:42:10,527 Beginning to grow galaxies themselves. 775 00:42:10,529 --> 00:42:13,396 I think it's some of the most exciting times right now 776 00:42:13,398 --> 00:42:15,198 In black hole astrophysics, 777 00:42:15,200 --> 00:42:17,567 And we just can't wait to see what's next. 778 00:42:17,569 --> 00:42:21,337 Narrator: And once we know for sure seed black holes are out there, 779 00:42:21,339 --> 00:42:23,139 We'll have the final chapter 780 00:42:23,141 --> 00:42:26,409 In the story of how the universe we see today 781 00:42:26,411 --> 00:42:27,677 Came to be.