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These are the user uploaded subtitles that are being translated: 1 00:00:02,220 --> 00:00:05,996 26,000 light-years from Earth, 2 00:00:06,020 --> 00:00:10,366 shrouded in cosmic dust and gas 3 00:00:10,390 --> 00:00:13,676 is a mysterious region of space... 4 00:00:13,700 --> 00:00:17,276 the center of the Milky Way. 5 00:00:17,300 --> 00:00:22,446 The center of the Milky Way galaxy is one of the strangest, 6 00:00:22,470 --> 00:00:28,240 most exotic and violent places in our galaxy. 7 00:00:29,580 --> 00:00:30,986 Gas streaming everywhere, 8 00:00:31,010 --> 00:00:33,956 radiation blasting out, 9 00:00:33,980 --> 00:00:36,866 stars moving willy-nilly. 10 00:00:36,890 --> 00:00:39,896 And at the very heart is the mysterious black hole, 11 00:00:39,920 --> 00:00:43,406 4 million times the mass of the sun. 12 00:00:43,430 --> 00:00:46,936 Now we're exploring the center of the Milky Way 13 00:00:46,960 --> 00:00:49,946 like never before, 14 00:00:49,970 --> 00:00:55,616 uncovering powerful forces that affect us all. 15 00:00:55,640 --> 00:00:58,056 Everything that happens at the center of the Milky Way galaxy 16 00:00:58,080 --> 00:00:59,986 really is connected to what's going on 17 00:01:00,010 --> 00:01:02,256 in the rest of the Milky Way. 18 00:01:02,280 --> 00:01:04,926 Understanding the center of our galaxy 19 00:01:04,950 --> 00:01:10,796 unlock secrets of our past, present and future. 20 00:01:10,820 --> 00:01:13,796 21 00:01:13,820 --> 00:01:16,830 captions paid for by discovery communications 22 00:01:27,400 --> 00:01:30,616 March 2019. 23 00:01:30,640 --> 00:01:34,216 We focus the XMM-Newton space telescope 24 00:01:34,240 --> 00:01:39,656 on a region of space around Sagittarius A-star, 25 00:01:39,680 --> 00:01:43,380 the supermassive black hole at the heart of our galaxy. 26 00:01:47,460 --> 00:01:53,030 We spot two huge columns of gas glowing in X-ray light. 27 00:01:59,840 --> 00:02:03,940 The columns seem to be coming from Sagittarius A-star. 28 00:02:06,040 --> 00:02:08,286 We see giant fountains of gas 29 00:02:08,310 --> 00:02:11,556 extending outward from the central region 30 00:02:11,580 --> 00:02:15,520 as though it's like a wind or a giant expulsion event. 31 00:02:17,490 --> 00:02:21,636 The fountains of gas extend 500 light-years above 32 00:02:21,660 --> 00:02:24,830 and below the supermassive black hole. 33 00:02:27,660 --> 00:02:30,206 That's over a million times the distance 34 00:02:30,230 --> 00:02:32,400 from the sun to Neptune. 35 00:02:35,210 --> 00:02:36,486 It looks like this material 36 00:02:36,510 --> 00:02:38,986 is actually leaving the vicinity of the black hole, 37 00:02:39,010 --> 00:02:44,456 like it's burping out these giant, hot X-ray chimneys. 38 00:02:44,480 --> 00:02:48,850 So why is Sagittarius A-star burping out hot gas? 39 00:02:50,390 --> 00:02:53,066 Typically, around a black hole, you have an accretion disk 40 00:02:53,090 --> 00:02:54,936 funneling material into the black hole, 41 00:02:54,960 --> 00:02:57,330 but all of it doesn't end up in the black hole. 42 00:02:59,430 --> 00:03:01,206 There is a little bit of gas 43 00:03:01,230 --> 00:03:03,630 falling onto it right now, even as I'm speaking, right? 44 00:03:05,670 --> 00:03:08,516 As gas falls toward the supermassive black hole, 45 00:03:08,540 --> 00:03:09,846 it becomes super heated. 46 00:03:09,870 --> 00:03:12,556 It liberates an enormous amount of energy 47 00:03:12,580 --> 00:03:16,326 and that energy has to go somewhere. 48 00:03:16,350 --> 00:03:20,026 As gas spirals towards the black hole, 49 00:03:20,050 --> 00:03:25,536 some of the material accelerates to near the speed of light. 50 00:03:25,560 --> 00:03:28,090 It blasts out from the accretion disk... 51 00:03:30,690 --> 00:03:34,136 ...creating chimneys of superheated gas 52 00:03:34,160 --> 00:03:35,706 that seem to connect 53 00:03:35,730 --> 00:03:38,646 to two of the largest structures in the galaxy... 54 00:03:38,670 --> 00:03:42,846 the Milky Way's Fermi bubbles. 55 00:03:42,870 --> 00:03:44,616 A few years ago, we noticed that, in fact, 56 00:03:44,640 --> 00:03:47,716 there are these giant bubbles coming out of the very heart 57 00:03:47,740 --> 00:03:49,426 of the Milky Way galaxy. 58 00:03:49,450 --> 00:03:50,426 In each direction, 59 00:03:50,450 --> 00:03:54,896 there's a bubble 25,000 light-years long. 60 00:03:54,920 --> 00:03:56,766 But the gas-filled bubbles 61 00:03:56,790 --> 00:03:59,866 dwarf the chimneys of superheated gas. 62 00:03:59,890 --> 00:04:04,206 Scientists wonder if another more powerful force 63 00:04:04,230 --> 00:04:06,276 blew the bubbles. 64 00:04:06,300 --> 00:04:09,106 So what could have created all of this superheated gas 65 00:04:09,130 --> 00:04:12,546 that actually blew these tremendously large bubbles? 66 00:04:12,570 --> 00:04:16,046 Supermassive black holes in other galaxies 67 00:04:16,070 --> 00:04:18,116 might offer clues. 68 00:04:18,140 --> 00:04:19,786 Black holes at the centers of galaxies 69 00:04:19,810 --> 00:04:21,116 go through different phases. 70 00:04:21,140 --> 00:04:25,656 So they can be either active or they can be calm. 71 00:04:25,680 --> 00:04:28,026 Sometimes black holes at the centers of galaxies 72 00:04:28,050 --> 00:04:30,426 go through an active phase. 73 00:04:30,450 --> 00:04:32,436 And when that happens, 74 00:04:32,460 --> 00:04:35,406 the black hole is actively feeding on material around it, 75 00:04:35,430 --> 00:04:36,906 which means it's growing 76 00:04:36,930 --> 00:04:40,090 and it also gives off huge jets of radiation. 77 00:04:42,500 --> 00:04:45,176 Calm supermassive black holes 78 00:04:45,200 --> 00:04:47,140 release a trickle of hot gas. 79 00:04:51,170 --> 00:04:55,156 But when lots of material falls on them, 80 00:04:55,180 --> 00:04:59,150 they can shoot out jets up to millions of light-years long. 81 00:05:04,120 --> 00:05:05,336 At the current time, 82 00:05:05,360 --> 00:05:07,936 Sagittarius A-star is what we call quiescent. 83 00:05:07,960 --> 00:05:09,136 It's quiet. 84 00:05:09,160 --> 00:05:11,266 There is some material swirling around it, 85 00:05:11,290 --> 00:05:14,176 but really not very much. 86 00:05:14,200 --> 00:05:16,760 But we don't think that's always been the case. 87 00:05:19,100 --> 00:05:21,816 The centers of galaxies are busy places. 88 00:05:21,840 --> 00:05:24,386 There are stars there. There's gas there. 89 00:05:24,410 --> 00:05:25,716 There's dust there, 90 00:05:25,740 --> 00:05:29,210 and sometimes these things fall into that black hole. 91 00:05:32,180 --> 00:05:34,056 6 million years ago, 92 00:05:34,080 --> 00:05:37,750 Sagittarius A-star may have had a feeding frenzy... 93 00:05:40,320 --> 00:05:42,106 ...eating too much 94 00:05:42,130 --> 00:05:45,390 and blasting out the remains in huge jets. 95 00:05:49,500 --> 00:05:51,606 Those jets plow through the galaxy 96 00:05:51,630 --> 00:05:55,746 initially at near the speed of light. 97 00:05:55,770 --> 00:05:57,716 And as they do so, they can wreak havoc 98 00:05:57,740 --> 00:06:00,286 or sculpt the evolution of the galaxy 99 00:06:00,310 --> 00:06:01,710 that they're propagating through. 100 00:06:03,910 --> 00:06:06,296 Sagittarius A-star's jets 101 00:06:06,320 --> 00:06:09,566 blasted gas out of the galaxy, 102 00:06:09,590 --> 00:06:14,596 creating the scars we see as the Fermi bubbles. 103 00:06:14,620 --> 00:06:17,636 Now, whatever caused those jets seems to have turned off. 104 00:06:17,660 --> 00:06:18,976 It's not happening anymore 105 00:06:19,000 --> 00:06:23,046 and we're seeing sort of the leftovers of them. 106 00:06:23,070 --> 00:06:24,306 But this is clearly a sign 107 00:06:24,330 --> 00:06:26,516 that sometime in the past few million years, 108 00:06:26,540 --> 00:06:28,276 the black hole in the center of our galaxy, 109 00:06:28,300 --> 00:06:32,970 Sagittarius A-star, was actively feeding on material around it. 110 00:06:35,410 --> 00:06:39,180 Material was falling into it and blasting out this stuff. 111 00:06:42,090 --> 00:06:45,050 The jets left destruction in their wake. 112 00:06:50,090 --> 00:06:55,476 They may have also affected the growth of our entire galaxy. 113 00:06:55,500 --> 00:06:58,276 These structures at the center of our galaxy are important 114 00:06:58,300 --> 00:07:01,116 because they can either shut off star formation 115 00:07:01,140 --> 00:07:03,340 or they can trigger star formation. 116 00:07:06,240 --> 00:07:09,126 As those jets propagate through the galaxy, 117 00:07:09,150 --> 00:07:10,456 they pile up gas 118 00:07:10,480 --> 00:07:13,150 and that gas can be then triggered into star formation. 119 00:07:16,450 --> 00:07:20,996 But these jets can also impart so much heat or energy feedback 120 00:07:21,020 --> 00:07:23,760 into the environment that they prevent star formation. 121 00:07:27,130 --> 00:07:30,006 So black holes in many ways conduct an orchestra, 122 00:07:30,030 --> 00:07:34,440 instructing or dictating when stars can and cannot form. 123 00:07:43,050 --> 00:07:45,196 In the center of the Milky Way, 124 00:07:45,220 --> 00:07:47,580 star-formation rates seem low. 125 00:07:50,020 --> 00:07:52,750 The jets could be responsible. 126 00:07:54,090 --> 00:07:58,036 But in 2017, the Alma telescope discovered 127 00:07:58,060 --> 00:08:00,700 that change is coming. 128 00:08:02,570 --> 00:08:05,176 So Alma's actually been able to peer in 129 00:08:05,200 --> 00:08:06,546 to the heart of our galaxy 130 00:08:06,570 --> 00:08:10,516 and see that near all this destruction, 131 00:08:10,540 --> 00:08:13,540 there might actually be a new generation of stars forming. 132 00:08:15,680 --> 00:08:18,796 Today, our calm supermassive black hole 133 00:08:18,820 --> 00:08:21,850 could be helping star formation in the core. 134 00:08:24,990 --> 00:08:28,566 But the Fermi bubbles could be evidence of a time 135 00:08:28,590 --> 00:08:34,036 when Sagittarius A-star shut down star formation. 136 00:08:34,060 --> 00:08:35,946 Could the supermassive black hole 137 00:08:35,970 --> 00:08:39,416 roar back to life in the future? 138 00:08:39,440 --> 00:08:41,716 Sagittarius A-star could roar back to life 139 00:08:41,740 --> 00:08:43,916 by just dumping some gas onto it. 140 00:08:43,940 --> 00:08:46,416 And there's a lot of gas at the center of our galaxy 141 00:08:46,440 --> 00:08:48,416 and it could wander into the proximity 142 00:08:48,440 --> 00:08:49,756 of Sagittarius A-star 143 00:08:49,780 --> 00:08:51,896 and ultimately fall onto the event horizon 144 00:08:51,920 --> 00:08:53,550 and that would light it up. 145 00:08:58,090 --> 00:09:01,860 If Sagittarius A-star eats enough gas... 146 00:09:04,690 --> 00:09:07,376 ...it could shut down star formation in the galaxy 147 00:09:07,400 --> 00:09:09,130 for millions of years. 148 00:09:15,000 --> 00:09:18,556 It could also give off X-rays and gamma rays 149 00:09:18,580 --> 00:09:20,210 that may hit the Earth. 150 00:09:23,810 --> 00:09:27,356 Thankfully, our central supermassive black hole 151 00:09:27,380 --> 00:09:30,766 is pretty quiet and massive feeding events, 152 00:09:30,790 --> 00:09:34,020 massive energy events are very, very rare. 153 00:09:35,930 --> 00:09:38,990 We don't necessarily have much to worry about. 154 00:09:41,400 --> 00:09:45,070 Sagittarius A-star has reshaped our galaxy. 155 00:09:49,070 --> 00:09:51,246 If we want to survive in the universe, 156 00:09:51,270 --> 00:09:54,540 we need to know more about this monster black hole. 157 00:09:56,680 --> 00:10:00,926 The Event Horizon Telescope is on a mission to do just that. 158 00:10:00,950 --> 00:10:04,190 Question is can it succeed? 159 00:10:16,700 --> 00:10:18,306 The center of the Milky Way 160 00:10:18,330 --> 00:10:21,176 is home to a supermassive black hole, 161 00:10:21,200 --> 00:10:24,386 Sagittarius A-star. 162 00:10:24,410 --> 00:10:26,340 At least we think it is. 163 00:10:29,050 --> 00:10:30,956 We've never seen the supermassive 164 00:10:30,980 --> 00:10:32,596 black hole directly. 165 00:10:32,620 --> 00:10:36,220 But we have seen stars racing around the core. 166 00:10:37,750 --> 00:10:39,536 The speeds of the stars 167 00:10:39,560 --> 00:10:42,806 zipping around the center of our Milky Way galaxy 168 00:10:42,830 --> 00:10:45,376 indicate that there's something very massive 169 00:10:45,400 --> 00:10:47,436 and very compact there, 170 00:10:47,460 --> 00:10:51,946 indeed, 4 million times as massive as our Sun 171 00:10:51,970 --> 00:10:55,946 in a volume smaller than that of our solar system. 172 00:10:55,970 --> 00:11:00,016 It's got to be a black hole basically. 173 00:11:00,040 --> 00:11:02,326 By measuring the orbits of stars 174 00:11:02,350 --> 00:11:03,610 in our galaxy center... 175 00:11:07,550 --> 00:11:09,966 ...we estimate that Sagittarius A-star 176 00:11:09,990 --> 00:11:12,820 is over a hundred times wider than our sun. 177 00:11:16,030 --> 00:11:19,930 But despite its size, the black hole is hidden. 178 00:11:22,030 --> 00:11:23,376 One of the immediate challenges 179 00:11:23,400 --> 00:11:24,946 of actually observing black holes 180 00:11:24,970 --> 00:11:29,146 is the fact that they don't emit light and so you can't see them. 181 00:11:29,170 --> 00:11:31,216 Right? So we've never actually seen a black hole. 182 00:11:31,240 --> 00:11:33,286 We've only seen the stuff around a black hole 183 00:11:33,310 --> 00:11:35,956 or we have seen the effects that that black hole 184 00:11:35,980 --> 00:11:38,350 imparts on its ambient surroundings. 185 00:11:40,450 --> 00:11:44,496 That's where the Event Horizon Telescope came in. 186 00:11:44,520 --> 00:11:49,806 Its goal was to photograph Sagittarius A-star, 187 00:11:49,830 --> 00:11:53,460 not the black hole itself, but its shadow. 188 00:11:55,060 --> 00:11:57,876 Around it is this a gas that is moving around the black hole 189 00:11:57,900 --> 00:12:00,376 that's super heated to millions of degrees. 190 00:12:00,400 --> 00:12:01,716 And what the Event Horizon Telescope 191 00:12:01,740 --> 00:12:04,410 is trying to see is the shadow of a black hole. 192 00:12:06,410 --> 00:12:09,986 Light from the hot gas around Sagittarius A-star 193 00:12:10,010 --> 00:12:12,196 frames the giant shadow. 194 00:12:12,220 --> 00:12:17,466 It could be up to 93 million miles across. 195 00:12:17,490 --> 00:12:21,796 Problem is Sagittarius A-star is so far away 196 00:12:21,820 --> 00:12:27,276 that the supermassive black hole is still incredibly hard to see. 197 00:12:27,300 --> 00:12:29,346 Sagittarius A-star is big, 198 00:12:29,370 --> 00:12:32,246 but it's 26,000 light-years away. 199 00:12:32,270 --> 00:12:34,716 A single light-year is 6 trillion miles. 200 00:12:34,740 --> 00:12:36,816 So this is a long, long walk. 201 00:12:36,840 --> 00:12:38,686 And even though it's big, 202 00:12:38,710 --> 00:12:41,316 that distance shrinks its apparent size 203 00:12:41,340 --> 00:12:45,326 to just a tiny little dot on the sky. 204 00:12:45,350 --> 00:12:47,956 To see the tiny dot, 205 00:12:47,980 --> 00:12:51,796 we need a telescope the size of the Earth. 206 00:12:51,820 --> 00:12:52,896 How do you possibly do that? 207 00:12:52,920 --> 00:12:56,466 You can't build that telescope, right? 208 00:12:56,490 --> 00:12:57,566 Well, there's a trick. 209 00:12:57,590 --> 00:12:59,236 You actually get a few different telescopes 210 00:12:59,260 --> 00:13:02,430 and you spread them out over the surface of the Earth. 211 00:13:08,070 --> 00:13:11,516 And when we had all of these sites together, 212 00:13:11,540 --> 00:13:14,616 we wind up being able to take an image of something 213 00:13:14,640 --> 00:13:18,926 that is really, really impossibly small. 214 00:13:18,950 --> 00:13:22,296 To gather enough light to see a target this small, 215 00:13:22,320 --> 00:13:25,096 the team take long-exposure images 216 00:13:25,120 --> 00:13:27,920 of Sagittarius A-star's shadow... 217 00:13:31,730 --> 00:13:34,576 ...but there's a problem. 218 00:13:34,600 --> 00:13:37,376 The accretion disk moves too much for us 219 00:13:37,400 --> 00:13:39,400 to capture a clear image. 220 00:13:42,610 --> 00:13:44,686 When you're taking a long exposure of a person, 221 00:13:44,710 --> 00:13:46,156 right, you need them to be really, 222 00:13:46,180 --> 00:13:47,916 really still, right? 223 00:13:47,940 --> 00:13:49,486 Because if they're moving around a lot, 224 00:13:49,510 --> 00:13:51,356 they're going to blur the image out. 225 00:13:51,380 --> 00:13:52,826 And that kind of thing is happening 226 00:13:52,850 --> 00:13:54,826 when we observe Sagittarius A-star 227 00:13:54,850 --> 00:13:57,226 because it is unwilling to sit still for us. 228 00:13:57,250 --> 00:13:58,936 It is booming and banging and flashing 229 00:13:58,960 --> 00:14:03,166 on the timescale of literally hours. 230 00:14:03,190 --> 00:14:06,306 As glowing material orbits the black hole 231 00:14:06,330 --> 00:14:07,906 at 30% the speed of light, 232 00:14:07,930 --> 00:14:11,430 Sagittarius A-star's shadow blurs. 233 00:14:13,840 --> 00:14:16,116 Future developments may allow us 234 00:14:16,140 --> 00:14:18,810 to see Sagittarius A-star clearly. 235 00:14:21,580 --> 00:14:24,426 For now, we can't capture an accurate image 236 00:14:24,450 --> 00:14:27,280 of our galaxy's supermassive black hole. 237 00:14:30,090 --> 00:14:33,396 But the hunt to see a supermassive black hole 238 00:14:33,420 --> 00:14:34,836 wasn't over. 239 00:14:34,860 --> 00:14:38,666 The Event Horizon Telescope turned to another galaxy 240 00:14:38,690 --> 00:14:43,560 54 million light-years away... M87. 241 00:14:45,000 --> 00:14:48,076 M87 is an absolute beast of a galaxy. 242 00:14:48,100 --> 00:14:50,216 It's the so-called brightest cluster galaxy. 243 00:14:50,240 --> 00:14:53,010 These are among the largest galaxies in the universe. 244 00:14:55,040 --> 00:14:56,886 And M87 is home 245 00:14:56,910 --> 00:14:59,756 to another supermassive black hole... 246 00:14:59,780 --> 00:15:02,820 the giant M87 star. 247 00:15:04,250 --> 00:15:09,606 M87 star is so massive that the gravitational region 248 00:15:09,630 --> 00:15:12,166 that's interesting is actually easier to image 249 00:15:12,190 --> 00:15:14,600 than the black hole in our own galaxy. 250 00:15:17,670 --> 00:15:22,116 M87 star is over a thousand times more massive 251 00:15:22,140 --> 00:15:24,186 than Sagittarius A-star 252 00:15:24,210 --> 00:15:28,156 and has a far larger accretion disk. 253 00:15:28,180 --> 00:15:31,486 When photographing a black hole, size matters, 254 00:15:31,510 --> 00:15:36,026 because big accretion disks project more stable light, 255 00:15:36,050 --> 00:15:39,250 so images of them don't blur as much. 256 00:15:42,260 --> 00:15:44,566 In April of 2019, 257 00:15:44,590 --> 00:15:49,106 the event horizon team unveiled their image. 258 00:15:49,130 --> 00:15:52,716 We have seen what we thought was unseeable. 259 00:15:52,740 --> 00:15:57,400 We have seen and taken a picture of a black hole. 260 00:16:05,250 --> 00:16:06,626 I've been working on this project 261 00:16:06,650 --> 00:16:09,626 for almost six years now, and so, this is something 262 00:16:09,650 --> 00:16:13,966 we've been looking forward to for a really long time. 263 00:16:13,990 --> 00:16:16,606 Capturing this image took decades of work 264 00:16:16,630 --> 00:16:20,490 by hundreds of scientists all over the world. 265 00:16:23,370 --> 00:16:25,776 I was really stunned. 266 00:16:25,800 --> 00:16:29,716 Suddenly, when you say that's the real thing, that's amazing. 267 00:16:29,740 --> 00:16:31,486 It really affected me. 268 00:16:31,510 --> 00:16:34,516 This is something 6 1/2 billion times 269 00:16:34,540 --> 00:16:36,186 the mass of the Sun, 270 00:16:36,210 --> 00:16:41,596 55 million light-years away and we're looking at it. 271 00:16:41,620 --> 00:16:44,526 So when you look at the image, it's totally fine. 272 00:16:44,550 --> 00:16:46,066 You're totally forgiven for thinking, 273 00:16:46,090 --> 00:16:48,596 "ah, it looks a little blurry." 274 00:16:48,620 --> 00:16:52,066 But I cannot reiterate enough 275 00:16:52,090 --> 00:16:55,176 how profound this image actually is. 276 00:16:55,200 --> 00:16:59,276 We are seeing just a hair's width away from a discontinuity 277 00:16:59,300 --> 00:17:01,646 in the fabric of space-time itself. 278 00:17:01,670 --> 00:17:05,516 Actually seeing so close to an actual event horizon, 279 00:17:05,540 --> 00:17:07,956 a discontinuity in the fabric of space-time, 280 00:17:07,980 --> 00:17:11,386 never seemed possible. 281 00:17:11,410 --> 00:17:14,956 This image of the heart of a distant galaxy 282 00:17:14,980 --> 00:17:19,590 helps us understand supermassive black holes like never before. 283 00:17:21,760 --> 00:17:24,336 When we observe supermassive black holes 284 00:17:24,360 --> 00:17:26,706 in other galaxies, including the one in m87, 285 00:17:26,730 --> 00:17:28,936 we're able to learn more about the big picture 286 00:17:28,960 --> 00:17:32,676 of how these massive black holes form and evolve over time. 287 00:17:32,700 --> 00:17:34,416 And that in turn, helps us understand 288 00:17:34,440 --> 00:17:35,746 how our Milky Way galaxy 289 00:17:35,770 --> 00:17:38,270 and its super massive black hole has formed. 290 00:17:40,440 --> 00:17:42,786 By studying, not just making images of black holes, 291 00:17:42,810 --> 00:17:44,686 but making videos of black holes, 292 00:17:44,710 --> 00:17:47,796 and seeing as that gas is spinning around it, 293 00:17:47,820 --> 00:17:50,896 we can try to map around a black hole more precisely 294 00:17:50,920 --> 00:17:52,890 and learn about its dynamics. 295 00:17:54,990 --> 00:17:57,366 An image of Sagittarius A-star 296 00:17:57,390 --> 00:17:58,766 remains out of reach, 297 00:17:58,790 --> 00:18:02,930 but in 2018, it shows a deadly side to its character. 298 00:18:04,700 --> 00:18:07,316 The supermassive black hole's accretion disk 299 00:18:07,340 --> 00:18:10,116 releases huge, powerful flares, 300 00:18:10,140 --> 00:18:13,810 and they could be pointed right at us. 301 00:18:22,020 --> 00:18:26,566 In 2018, astronomers were studying a special star 302 00:18:26,590 --> 00:18:29,806 orbiting our galaxy's supermassive black hole. 303 00:18:29,830 --> 00:18:33,206 The star passes close to Sagittarius A-star... 304 00:18:33,230 --> 00:18:35,636 every 16 years. 305 00:18:35,660 --> 00:18:40,276 It's called S2, and by studying this star's fly-by, 306 00:18:40,300 --> 00:18:44,040 we hope to learn more about Sagittarius A-star. 307 00:18:45,370 --> 00:18:48,216 We think that S2 may be the very closest star 308 00:18:48,240 --> 00:18:51,656 to the supermassive black hole in the center of our galaxy. 309 00:18:51,680 --> 00:18:53,756 At closest approach to sag A-star, 310 00:18:53,780 --> 00:18:58,390 S2 comes within 17 light hours or so of the surface. 311 00:19:00,920 --> 00:19:04,136 The supermassive black hole's powerful gravity 312 00:19:04,160 --> 00:19:09,176 accelerates the star to 17 million miles an hour. 313 00:19:09,200 --> 00:19:12,516 That's fast enough to travel from New York to L.A. 314 00:19:12,540 --> 00:19:15,616 In half a second, 315 00:19:15,640 --> 00:19:19,370 but it's not the star's speed that excites scientists. 316 00:19:20,410 --> 00:19:23,186 This is a great star, because it's on an elliptical orbit 317 00:19:23,210 --> 00:19:25,756 that takes it fairly far from the black hole, 318 00:19:25,780 --> 00:19:27,056 but every few years, 319 00:19:27,080 --> 00:19:30,650 it passes right above the supermassive black hole. 320 00:19:32,720 --> 00:19:36,936 As we tracked S2's swing around Sagittarius A-star, 321 00:19:36,960 --> 00:19:40,506 we detected powerful bursts of infrared light 322 00:19:40,530 --> 00:19:44,200 coming from the direction of the supermassive black hole. 323 00:19:46,670 --> 00:19:48,316 There's a blob of gas 324 00:19:48,340 --> 00:19:51,016 that is orbiting very close to the black hole, 325 00:19:51,040 --> 00:19:53,556 and it was flaring as it went around. 326 00:19:53,580 --> 00:19:55,716 There were three separate flares of light 327 00:19:55,740 --> 00:19:59,056 that they were able to detect. 328 00:19:59,080 --> 00:20:00,956 The flares didn't come directly 329 00:20:00,980 --> 00:20:04,426 from the supermassive black hole, 330 00:20:04,450 --> 00:20:07,690 they came from the material around it. 331 00:20:10,230 --> 00:20:12,776 The flares that were discovered are thought to originate 332 00:20:12,800 --> 00:20:14,276 from magnetic storms 333 00:20:14,300 --> 00:20:18,500 in this very, very hot turbulent gas around the black hole. 334 00:20:20,900 --> 00:20:23,246 The extreme heat in the accretion disk 335 00:20:23,270 --> 00:20:26,386 strips electrons from atoms of gas. 336 00:20:26,410 --> 00:20:30,256 The stripped electrons and hot gas form a plasma, 337 00:20:30,280 --> 00:20:32,956 which creates powerful magnetic fields 338 00:20:32,980 --> 00:20:35,280 when accelerated to high speeds. 339 00:20:37,250 --> 00:20:39,496 Because some super massive black holes 340 00:20:39,520 --> 00:20:40,796 have these superheated, 341 00:20:40,820 --> 00:20:44,166 rapidly spinning vortices of gas swirling around them, 342 00:20:44,190 --> 00:20:46,206 you get these very, very powerful, 343 00:20:46,230 --> 00:20:48,560 very tightly wound magnetic fields. 344 00:20:50,630 --> 00:20:52,746 And there's energy stored in that magnetic field. 345 00:20:52,770 --> 00:20:55,676 It's like a bunch of piano wires all tangled up. 346 00:20:55,700 --> 00:20:58,586 And if these things interact with each other, they can snap, 347 00:20:58,610 --> 00:21:01,240 and when they snap, that energy is released. 348 00:21:05,450 --> 00:21:07,696 You'll get this enormous release of energy 349 00:21:07,720 --> 00:21:11,266 as these coils of magnetic fields effectively snap. 350 00:21:11,290 --> 00:21:15,896 And when they do so, just like on the surface of our sun, 351 00:21:15,920 --> 00:21:18,560 they release an enormous flare of gas. 352 00:21:22,160 --> 00:21:27,376 These powerful flares can be millions of miles wide 353 00:21:27,400 --> 00:21:31,640 and come packed with superheated gas and plasma. 354 00:21:35,210 --> 00:21:37,986 Solar flares release as much energy 355 00:21:38,010 --> 00:21:40,710 as 10 million volcanic explosions. 356 00:21:45,590 --> 00:21:50,506 Flares from Sagittarius A-star's accretion disk 357 00:21:50,530 --> 00:21:55,600 are like millions of solar flares all going off at once. 358 00:21:58,330 --> 00:22:02,000 It's kind of like comparing a nuclear weapon to a firecracker. 359 00:22:04,140 --> 00:22:06,856 Sagittarius A-star's flares 360 00:22:06,880 --> 00:22:09,526 release intense blasts of radiation, 361 00:22:09,550 --> 00:22:12,556 but by watching the flares from Earth, 362 00:22:12,580 --> 00:22:14,526 we can learn about the orientation 363 00:22:14,550 --> 00:22:17,620 of the supermassive black hole's accretion disk. 364 00:22:19,390 --> 00:22:21,466 This gas that's in this accretion disk 365 00:22:21,490 --> 00:22:25,236 around the black hole is like a friendly helper 366 00:22:25,260 --> 00:22:27,376 shining a flashlight back toward Earth. 367 00:22:27,400 --> 00:22:29,776 And we can watch the orbit of these flashlights 368 00:22:29,800 --> 00:22:32,106 and help understand the orientation of gas 369 00:22:32,130 --> 00:22:33,900 that swirls around the black hole. 370 00:22:37,470 --> 00:22:39,416 We think we're getting a bird's-eye view of it. 371 00:22:39,440 --> 00:22:41,086 And looking down the barrel, 372 00:22:41,110 --> 00:22:45,586 we're looking at the accretion disk basically face-on. 373 00:22:45,610 --> 00:22:48,126 That means that any material that gets blasted away 374 00:22:48,150 --> 00:22:50,980 from the black hole could be aimed right at us. 375 00:22:53,990 --> 00:22:57,490 Should we be worried about the flares reaching Earth? 376 00:22:59,090 --> 00:23:01,236 It sounds worrisome, this blob of gas 377 00:23:01,260 --> 00:23:03,476 emitting these huge flares of light, 378 00:23:03,500 --> 00:23:07,246 but you've got to realize, this is 26,000 light-years away. 379 00:23:07,270 --> 00:23:08,546 That is a long way. 380 00:23:08,570 --> 00:23:11,116 It took an extremely sensitive detector 381 00:23:11,140 --> 00:23:13,816 on one of the largest telescopes on Earth 382 00:23:13,840 --> 00:23:16,726 to be able to see this at all. 383 00:23:16,750 --> 00:23:18,986 Earth is safe for now, 384 00:23:19,010 --> 00:23:22,196 but the more we learn about the galaxy center, 385 00:23:22,220 --> 00:23:25,126 the more terrifying it becomes. 386 00:23:25,150 --> 00:23:27,236 We know of Sagittarius A-star, 387 00:23:27,260 --> 00:23:29,196 the central supermassive black hole, 388 00:23:29,220 --> 00:23:31,006 but now we're beginning to suspect 389 00:23:31,030 --> 00:23:33,590 that it might not be alone. 390 00:23:35,230 --> 00:23:37,806 A dangerous swarm of black holes 391 00:23:37,830 --> 00:23:41,716 could be racing around the center of the Milky Way. 392 00:23:41,740 --> 00:23:44,940 Thousands more may be hiding from sight. 393 00:23:53,720 --> 00:23:57,596 The supermassive black hole, Sagittarius A-star, 394 00:23:57,620 --> 00:24:00,090 dominates the center of the Milky Way... 395 00:24:02,120 --> 00:24:04,060 ...affecting star formation... 396 00:24:06,230 --> 00:24:09,400 ...and carving out vast gas bubbles in space. 397 00:24:11,770 --> 00:24:16,546 But Sagittarius A-star might not be the only black hole in town, 398 00:24:16,570 --> 00:24:19,440 or even the most dangerous. 399 00:24:21,840 --> 00:24:23,026 We've known for a long time 400 00:24:23,050 --> 00:24:24,456 that there's a supermassive black hole 401 00:24:24,480 --> 00:24:26,356 in the very heart of our galaxy, 402 00:24:26,380 --> 00:24:29,526 but there may be an angry swarm of smaller black holes, 403 00:24:29,550 --> 00:24:32,296 buzzing all around it. 404 00:24:32,320 --> 00:24:34,596 In April of 2018, 405 00:24:34,620 --> 00:24:37,306 astronomers led by Columbia university 406 00:24:37,330 --> 00:24:39,836 revealed the results of a hunting mission 407 00:24:39,860 --> 00:24:42,006 in the center of the galaxy. 408 00:24:42,030 --> 00:24:45,776 They'd used 12 years of Chandra observatory data 409 00:24:45,800 --> 00:24:49,986 to seek out stellar mass black holes. 410 00:24:50,010 --> 00:24:52,586 Black holes that are made from the death of stars, 411 00:24:52,610 --> 00:24:54,216 from supernova explosions, 412 00:24:54,240 --> 00:24:56,940 are called stellar mass black holes. 413 00:25:02,120 --> 00:25:04,066 And these are made from stars 414 00:25:04,090 --> 00:25:06,890 that were many times the mass of the sun. 415 00:25:09,730 --> 00:25:14,336 Finding stellar mass black holes is tough. 416 00:25:14,360 --> 00:25:17,376 Light can't escape a black hole's gravity, 417 00:25:17,400 --> 00:25:19,400 so we can't see them directly. 418 00:25:22,700 --> 00:25:26,916 And stellar mass black holes are only tens of miles wide, 419 00:25:26,940 --> 00:25:30,040 making them almost impossible to detect. 420 00:25:32,280 --> 00:25:34,696 So astronomers look for a special type 421 00:25:34,720 --> 00:25:36,680 of stellar mass black hole. 422 00:25:40,360 --> 00:25:44,266 One of the ways that we look for stellar mass black holes, 423 00:25:44,290 --> 00:25:50,060 is that they often are vampires eating a companion star. 424 00:25:53,800 --> 00:25:58,186 These vampires are part of a binary pair, 425 00:25:58,210 --> 00:26:02,556 a stellar mass black hole in orbit with a living star, 426 00:26:02,580 --> 00:26:05,950 the black hole feasting on its partner. 427 00:26:07,380 --> 00:26:08,726 That black hole 428 00:26:08,750 --> 00:26:11,466 is like a very, very deadly parasite for that star. 429 00:26:11,490 --> 00:26:14,266 It is ripping mass off the surface of that star, 430 00:26:14,290 --> 00:26:17,660 and that matter is raining down toward the black hole itself. 431 00:26:21,000 --> 00:26:23,046 And that material lights up, 432 00:26:23,070 --> 00:26:25,606 so this allows us to hunt for black holes, 433 00:26:25,630 --> 00:26:28,676 not through taking pictures of black holes directly, 434 00:26:28,700 --> 00:26:32,986 but through seeing the material falling to its doom. 435 00:26:33,010 --> 00:26:35,056 The problem is, 436 00:26:35,080 --> 00:26:37,386 gas and dust spread throughout the galaxy 437 00:26:37,410 --> 00:26:41,596 stops visible light from the binary pair reaching Earth. 438 00:26:41,620 --> 00:26:44,696 But the binary pair release another type of light 439 00:26:44,720 --> 00:26:48,796 that passes through the gas and dust more easily... 440 00:26:48,820 --> 00:26:50,736 X-rays. 441 00:26:50,760 --> 00:26:53,276 The system itself is emitting X-rays, 442 00:26:53,300 --> 00:26:55,276 so they're called X-ray binaries. 443 00:26:55,300 --> 00:26:57,946 So these are useful, because the X-ray emission 444 00:26:57,970 --> 00:26:59,446 can be very powerful 445 00:26:59,470 --> 00:27:02,146 and can be potentially seen from the Earth, 446 00:27:02,170 --> 00:27:04,216 even though the binary is very far away, 447 00:27:04,240 --> 00:27:06,040 say, at the galactic center. 448 00:27:08,640 --> 00:27:12,386 The glowing disks of material in X-ray binary systems 449 00:27:12,410 --> 00:27:15,996 are almost a million times smaller than the accretion disk 450 00:27:16,020 --> 00:27:19,326 surrounding Sagittarius A-star, too small 451 00:27:19,350 --> 00:27:23,560 for us to see the material swirling around them in detail. 452 00:27:25,060 --> 00:27:30,460 So, we see the X-ray binaries as pinpricks of X-ray light. 453 00:27:33,200 --> 00:27:36,786 Astronomers detect 12 of these X-ray binaries 454 00:27:36,810 --> 00:27:40,356 in a small 3-light-year-wide patch of space 455 00:27:40,380 --> 00:27:42,186 at the galactic center. 456 00:27:42,210 --> 00:27:44,756 And that means that there could be a much larger collection 457 00:27:44,780 --> 00:27:47,756 of these relatively tiny stellar mass black holes 458 00:27:47,780 --> 00:27:51,266 in the heart of our galaxy. 459 00:27:51,290 --> 00:27:53,666 If black holes form the way we think they do, 460 00:27:53,690 --> 00:27:56,436 there very likely may be swarms of black holes 461 00:27:56,460 --> 00:27:58,560 racing around Sagittarius A-star. 462 00:28:01,500 --> 00:28:04,446 But X-ray binaries that are powerful enough for us 463 00:28:04,470 --> 00:28:08,846 to detect are incredibly rare. 464 00:28:08,870 --> 00:28:13,586 So we estimate that for the dozen X-ray binaries discovered, 465 00:28:13,610 --> 00:28:15,540 there could be up to a thousand more. 466 00:28:20,820 --> 00:28:25,526 In total, there could be 20,000 stellar mass black holes 467 00:28:25,550 --> 00:28:28,690 in this 3-light-year region of space. 468 00:28:38,070 --> 00:28:41,846 Why are these black holes swarming in the galaxy center? 469 00:28:41,870 --> 00:28:45,810 It appears they've migrated from the rest of the Milky Way. 470 00:28:47,340 --> 00:28:49,356 Through a process called dynamical friction, 471 00:28:49,380 --> 00:28:51,856 black holes can actually sink to the centers of galaxies 472 00:28:51,880 --> 00:28:55,926 very, very rapidly, like dropping a stone into a pond. 473 00:28:55,950 --> 00:28:58,096 What that means is that an errant, 474 00:28:58,120 --> 00:28:59,996 wandering black hole might eventually 475 00:29:00,020 --> 00:29:02,596 find its way toward the center of our own galaxy, 476 00:29:02,620 --> 00:29:06,576 where Sagittarius A-star resides. 477 00:29:06,600 --> 00:29:10,606 As stellar mass black holes orbit the galaxy, 478 00:29:10,630 --> 00:29:12,676 they interact gravitationally 479 00:29:12,700 --> 00:29:15,600 with stars and clouds of gas and dust. 480 00:29:17,410 --> 00:29:20,516 These interactions push the black holes 481 00:29:20,540 --> 00:29:23,826 towards the center of the galaxy, 482 00:29:23,850 --> 00:29:25,450 where the black holes swarm. 483 00:29:30,390 --> 00:29:34,466 A swarm of stellar mass black holes sounds deadly, 484 00:29:34,490 --> 00:29:37,006 but it may not be the most lethal thing 485 00:29:37,030 --> 00:29:38,860 in the center of the Milky Way. 486 00:29:41,330 --> 00:29:45,376 A surprising observation indicates that there is a lot 487 00:29:45,400 --> 00:29:49,376 of antimatter in the center of our galaxy. 488 00:29:49,400 --> 00:29:52,516 And when antimatter meets matter, 489 00:29:52,540 --> 00:29:55,240 the results are explosive. 490 00:30:05,620 --> 00:30:07,436 In 2017, 491 00:30:07,460 --> 00:30:11,890 astronomers tried to solve a decades-old cosmic mystery... 492 00:30:14,830 --> 00:30:17,746 ...unexplained high-energy radiation 493 00:30:17,770 --> 00:30:19,700 streaming through our galaxy. 494 00:30:23,440 --> 00:30:25,940 At first, we didn't know where it was from. 495 00:30:28,440 --> 00:30:31,226 But we discovered it was gamma radiation 496 00:30:31,250 --> 00:30:34,950 coming from somewhere in the center of the Milky Way. 497 00:30:37,550 --> 00:30:40,236 The question is, what's making these gamma rays? 498 00:30:40,260 --> 00:30:41,966 That's hard to do. 499 00:30:41,990 --> 00:30:43,506 It's not like you can rub your hands together 500 00:30:43,530 --> 00:30:46,906 and generate gamma rays. 501 00:30:46,930 --> 00:30:48,976 When we took a closer look at the gamma rays, 502 00:30:49,000 --> 00:30:52,776 we discovered the signature of the most explosive substance 503 00:30:52,800 --> 00:30:55,440 in the universe... antimatter. 504 00:30:59,270 --> 00:31:02,556 Antimatter is like normal matter 505 00:31:02,580 --> 00:31:04,556 but with opposite charge. 506 00:31:04,580 --> 00:31:07,050 That's it. It's matter's evil twin. 507 00:31:09,150 --> 00:31:11,926 When evil twin meets good twin, 508 00:31:11,950 --> 00:31:14,420 it is not a happy reunion. 509 00:31:17,330 --> 00:31:18,736 Antimatter is scary. 510 00:31:18,760 --> 00:31:21,436 It's not like you want to have some in your kitchen. 511 00:31:21,460 --> 00:31:23,646 This stuff is very, very explosive, 512 00:31:23,670 --> 00:31:25,746 if you want to think of it that way. 513 00:31:25,770 --> 00:31:27,476 If it touches normal matter, 514 00:31:27,500 --> 00:31:29,800 it releases a huge amount of energy. 515 00:31:31,740 --> 00:31:33,756 When matter and antimatter combine, 516 00:31:33,780 --> 00:31:36,156 they annihilate each other and transform 517 00:31:36,180 --> 00:31:39,656 into high-energy radiation, just like the gamma rays 518 00:31:39,680 --> 00:31:42,780 seen streaming out of the center of the Milky Way. 519 00:31:44,620 --> 00:31:47,536 We see antimatter throughout the galaxy, 520 00:31:47,560 --> 00:31:49,966 but strangely, the galactic center 521 00:31:49,990 --> 00:31:54,530 seemed to have 40% more antimatter than anywhere else. 522 00:31:56,830 --> 00:31:58,646 Right now in the heart of our galaxy, 523 00:31:58,670 --> 00:32:01,676 we actually observe fountains of antimatter 524 00:32:01,700 --> 00:32:04,646 that are producing 10 trillion tons 525 00:32:04,670 --> 00:32:07,816 of antimatter every second. 526 00:32:07,840 --> 00:32:09,516 One of the big questions that we've wondered about 527 00:32:09,540 --> 00:32:12,450 for a very long time, is what's the origin of this stuff? 528 00:32:15,820 --> 00:32:19,396 Initially, there were several suspects. 529 00:32:19,420 --> 00:32:21,166 One possible source of antimatter 530 00:32:21,190 --> 00:32:24,806 is the central black hole, Sagittarius A-star. 531 00:32:24,830 --> 00:32:26,436 Matter can be swirling around this 532 00:32:26,460 --> 00:32:28,176 and it can have such high energy 533 00:32:28,200 --> 00:32:29,960 that it can create antimatter. 534 00:32:33,230 --> 00:32:34,916 But the antimatter 535 00:32:34,940 --> 00:32:37,046 isn't coming from a single point, 536 00:32:37,070 --> 00:32:41,556 it's spread across thousands of light-years of space. 537 00:32:41,580 --> 00:32:43,216 So Sagittarius A-star 538 00:32:43,240 --> 00:32:46,750 can't be the source of the gamma-ray stream. 539 00:32:49,680 --> 00:32:52,590 Another suspect was dark matter. 540 00:32:55,060 --> 00:32:56,566 One of the biggest mysteries in the universe 541 00:32:56,590 --> 00:32:58,636 right now is dark matter. 542 00:32:58,660 --> 00:33:01,506 We know that the majority of mass in the universe 543 00:33:01,530 --> 00:33:03,136 is not in the same form that we are. 544 00:33:03,160 --> 00:33:04,906 It's not made of atoms, 545 00:33:04,930 --> 00:33:07,446 but whatever sort of particle it is or may be, 546 00:33:07,470 --> 00:33:10,846 if these things collide, they can produce antimatter, 547 00:33:10,870 --> 00:33:12,586 and that will produce the gamma rays. 548 00:33:12,610 --> 00:33:15,216 So it's possible that as we look into the heart of the galaxy 549 00:33:15,240 --> 00:33:17,026 and see these extra gamma rays, 550 00:33:17,050 --> 00:33:19,650 that's the signal that dark matter is there. 551 00:33:23,690 --> 00:33:26,736 But the gamma ray stream we detected is too weak 552 00:33:26,760 --> 00:33:29,160 to have been created by dark matter. 553 00:33:31,830 --> 00:33:35,676 Then we had a breakthrough. 554 00:33:35,700 --> 00:33:40,316 We discovered that a special metal called titanium-44 555 00:33:40,340 --> 00:33:43,500 could be responsible for the gamma-ray stream. 556 00:33:47,340 --> 00:33:50,526 Titanium-44 is a highly radioactive element. 557 00:33:50,550 --> 00:33:52,226 That means that it wants to decay 558 00:33:52,250 --> 00:33:54,080 into other types of nuclei. 559 00:33:57,090 --> 00:33:59,626 When titanium-44 decays, 560 00:33:59,650 --> 00:34:01,436 it gives off antimatter. 561 00:34:01,460 --> 00:34:05,666 But to produce the antimatter seen in the galaxy's core, 562 00:34:05,690 --> 00:34:09,106 you would need a lot of titanium-44. 563 00:34:09,130 --> 00:34:14,216 It could be created in rare energetic events, 564 00:34:14,240 --> 00:34:18,670 in the collision of two dead stars... white dwarfs. 565 00:34:20,580 --> 00:34:23,386 A white dwarf star is a star that didn't have enough mass 566 00:34:23,410 --> 00:34:25,986 when it died to actually become a supernova. 567 00:34:26,010 --> 00:34:28,656 It just sort of cools off as a dead little cinder. 568 00:34:28,680 --> 00:34:30,326 But what if you have two white dwarfs 569 00:34:30,350 --> 00:34:32,126 that are orbiting around each other, 570 00:34:32,150 --> 00:34:34,936 and as they come closer and closer and collide, 571 00:34:34,960 --> 00:34:36,906 all of a sudden now, you have enough mass 572 00:34:36,930 --> 00:34:39,290 to actually kick a supernova explosion off. 573 00:34:44,370 --> 00:34:46,176 These particular kinds of supernovae 574 00:34:46,200 --> 00:34:49,070 are very good at producing titanium-44. 575 00:34:50,870 --> 00:34:53,656 So these kinds of supernovas are very, very good 576 00:34:53,680 --> 00:34:55,310 at making antimatter. 577 00:34:57,880 --> 00:35:00,856 These supernovas erupt in the core of the galaxy 578 00:35:00,880 --> 00:35:03,220 once every 2,000 years. 579 00:35:06,220 --> 00:35:09,136 But outside of the core in the disk of the galaxy 580 00:35:09,160 --> 00:35:11,390 where our solar system orbits... 581 00:35:13,530 --> 00:35:16,760 ...these supernovas happen three times as often. 582 00:35:18,330 --> 00:35:22,146 So the gamma ray observations were wrong. 583 00:35:22,170 --> 00:35:25,846 There isn't more antimatter in the heart of the galaxy. 584 00:35:25,870 --> 00:35:28,086 It's our region of the galaxy 585 00:35:28,110 --> 00:35:31,210 that contains the most antimatter. 586 00:35:33,380 --> 00:35:36,150 Question is, are we in danger? 587 00:35:38,590 --> 00:35:39,766 If you take an ounce of matter 588 00:35:39,790 --> 00:35:41,736 and an ounce of antimatter and collide them, 589 00:35:41,760 --> 00:35:45,166 you're generating a megaton of energy, 590 00:35:45,190 --> 00:35:49,776 the equivalent of a million tons of TNT exploding. 591 00:35:49,800 --> 00:35:51,746 So you don't need much antimatter to generate 592 00:35:51,770 --> 00:35:54,676 a vast amount of energy. 593 00:35:54,700 --> 00:35:56,886 But the thing you have to remember is we live 594 00:35:56,910 --> 00:35:59,146 in this wonderful, dramatic environment 595 00:35:59,170 --> 00:36:00,356 of a larger universe. 596 00:36:00,380 --> 00:36:01,716 It's not dangerous. 597 00:36:01,740 --> 00:36:04,780 It's very far away from us, and it's fascinating. 598 00:36:07,250 --> 00:36:10,566 But all of this antimatter is being produced in our galaxy, 599 00:36:10,590 --> 00:36:13,620 so just sit back and enjoy the fireworks. 600 00:36:15,890 --> 00:36:18,366 The center of the Milky Way 601 00:36:18,390 --> 00:36:19,866 is violent and extreme, 602 00:36:19,890 --> 00:36:22,830 but things could get a whole lot worse. 603 00:36:24,700 --> 00:36:26,846 Rogue supermassive black holes 604 00:36:26,870 --> 00:36:30,046 could be lurking near our galaxy, 605 00:36:30,070 --> 00:36:34,040 and they have the power to end life as we know it. 606 00:36:45,220 --> 00:36:49,436 The Milky Way is around 100,000 light-years across, 607 00:36:49,460 --> 00:36:54,506 and it's home to at least 200 billion stars, 608 00:36:54,530 --> 00:36:58,046 but it hasn't always been this large. 609 00:36:58,070 --> 00:37:01,416 We know that our Milky Way galaxy grew to the size 610 00:37:01,440 --> 00:37:06,746 it is now, which is huge, by eating other galaxies. 611 00:37:06,770 --> 00:37:09,056 And some of these galaxies would've had 612 00:37:09,080 --> 00:37:11,580 supermassive black holes in their centers. 613 00:37:14,220 --> 00:37:16,856 When the Milky Way's gravity 614 00:37:16,880 --> 00:37:18,666 pulled in smaller galaxies, 615 00:37:18,690 --> 00:37:23,806 most of their material merged with the Milky Way, 616 00:37:23,830 --> 00:37:25,966 but some material like stars, 617 00:37:25,990 --> 00:37:29,436 could've been slung tens of thousands of light-years 618 00:37:29,460 --> 00:37:31,100 out of the Milky Way. 619 00:37:33,400 --> 00:37:36,876 This could've happened to a smaller galaxy's 620 00:37:36,900 --> 00:37:39,786 super massive black hole. 621 00:37:39,810 --> 00:37:41,456 It is entirely possible 622 00:37:41,480 --> 00:37:43,516 there are supermassive black holes 623 00:37:43,540 --> 00:37:46,980 wandering around out there, not in the center. 624 00:37:49,420 --> 00:37:51,196 So how could it be possible that there's actually 625 00:37:51,220 --> 00:37:53,966 a supermassive black hole close to us wandering around, 626 00:37:53,990 --> 00:37:55,736 but we never even see it? 627 00:37:55,760 --> 00:37:59,206 Well, remember black hole means it's really, really black. 628 00:37:59,230 --> 00:38:02,036 It actually absorbs radiation and any energy. 629 00:38:02,060 --> 00:38:04,476 So unless something is falling into a black hole 630 00:38:04,500 --> 00:38:08,376 or orbiting around it, you're not going to see it. 631 00:38:08,400 --> 00:38:09,946 And so, if this supermassive black hole 632 00:38:09,970 --> 00:38:13,246 were hypothetically wandering the outskirts of our galaxy, 633 00:38:13,270 --> 00:38:15,216 well, there's a lot less gas there 634 00:38:15,240 --> 00:38:16,916 for that black hole to run into. 635 00:38:16,940 --> 00:38:18,126 And if there's no gas around 636 00:38:18,150 --> 00:38:20,550 that black hole, we will not see it. 637 00:38:22,680 --> 00:38:26,096 The rogue supermassive black hole may not stay 638 00:38:26,120 --> 00:38:28,996 in the outskirts of the galaxy forever. 639 00:38:29,020 --> 00:38:32,636 Gravitational interactions slowly pull it back 640 00:38:32,660 --> 00:38:34,636 into the Milky Way. 641 00:38:34,660 --> 00:38:36,436 Billions of years later, 642 00:38:36,460 --> 00:38:41,230 the supermassive black hole could arrive in the center. 643 00:38:45,570 --> 00:38:48,686 When this rogue supermassive black hole meets up with 644 00:38:48,710 --> 00:38:53,550 Sagittarius A-star, the fuse is lit. 645 00:38:55,180 --> 00:38:57,650 The pair spiral towards each other... 646 00:39:00,920 --> 00:39:02,866 ...spinning faster and faster, 647 00:39:02,890 --> 00:39:05,460 reaching up to half the speed of light. 648 00:39:10,700 --> 00:39:14,530 Finally, the two black holes merge. 649 00:39:20,810 --> 00:39:21,986 You would have 650 00:39:22,010 --> 00:39:24,156 an enormously energetic event on your hands. 651 00:39:24,180 --> 00:39:26,656 Those supermassive black holes could, in principle, 652 00:39:26,680 --> 00:39:30,526 merge together, create a huge blast of gravitational waves, 653 00:39:30,550 --> 00:39:34,366 accompanied by a profoundly energetic flash of light 654 00:39:34,390 --> 00:39:37,060 that could, in principle, endanger all life on Earth. 655 00:39:43,160 --> 00:39:45,646 It's literally a stretching 656 00:39:45,670 --> 00:39:47,816 and contracting of space itself. 657 00:39:47,840 --> 00:39:50,046 It's like grabbing the framework of space 658 00:39:50,070 --> 00:39:51,916 and it's shaking it really hard. 659 00:39:51,940 --> 00:39:53,886 And if this happens in our galaxy, 660 00:39:53,910 --> 00:39:59,040 the amount of energy emitted, that would be bad. 661 00:40:01,120 --> 00:40:03,296 When the black holes collide, 662 00:40:03,320 --> 00:40:04,626 they release more energy 663 00:40:04,650 --> 00:40:08,690 than all the stars in the galaxy combined. 664 00:40:15,500 --> 00:40:17,846 Should we be panicked about this? 665 00:40:17,870 --> 00:40:19,246 And the answer is no. 666 00:40:19,270 --> 00:40:21,176 The Earth has been orbiting the sun 667 00:40:21,200 --> 00:40:23,886 for 4 1/2 billion years without any incident, right? 668 00:40:23,910 --> 00:40:26,516 We're pretty safe from them. 669 00:40:26,540 --> 00:40:30,656 If we were around to see the two black holes collide, 670 00:40:30,680 --> 00:40:33,386 we'd witness the most destructive light show 671 00:40:33,410 --> 00:40:35,350 in the history of the galaxy. 672 00:40:38,020 --> 00:40:43,336 But for now, the center of our galaxy is relatively quiet, 673 00:40:43,360 --> 00:40:46,390 but it's still a terrible place to be. 674 00:40:49,930 --> 00:40:53,046 The center of our Milky Way is not a friendly place. 675 00:40:53,070 --> 00:40:56,816 It's nowhere you want to be. It's a bad neighborhood. 676 00:40:56,840 --> 00:41:00,916 You've got tons of stars, tons of radiation, 677 00:41:00,940 --> 00:41:05,026 and stars are being born and dying and exploding. 678 00:41:05,050 --> 00:41:06,886 You've got the central supermassive black hole. 679 00:41:06,910 --> 00:41:09,556 You've got a potential swarm of black holes. 680 00:41:09,580 --> 00:41:11,996 You've got accretion disks. You've got flares. 681 00:41:12,020 --> 00:41:16,096 You've got magnetic outbursts. You've got jets. 682 00:41:16,120 --> 00:41:18,690 Let's just stay out here in the suburbs, all right? 683 00:41:20,830 --> 00:41:22,136 The center of our galaxy 684 00:41:22,160 --> 00:41:25,830 is one of the most nightmarish places in the cosmos. 685 00:41:28,640 --> 00:41:32,016 It's also home to some of the most incredible forces 686 00:41:32,040 --> 00:41:33,740 the universe has to offer. 687 00:41:36,540 --> 00:41:39,210 Whatever the future holds for our galaxy... 688 00:41:41,620 --> 00:41:46,866 ...the core of the Milky Way will be at the center of it all. 689 00:41:46,890 --> 00:41:50,396 Our home galaxy, the Milky Way, is our safe harbor, 690 00:41:50,420 --> 00:41:53,766 our island in this vast, cosmic ocean. 691 00:41:53,790 --> 00:41:56,776 And so to understand the heart of our galaxy, 692 00:41:56,800 --> 00:42:00,530 is to understand our home in this cosmic void. 693 00:42:00,580 --> 00:42:05,130 Repair and Synchronization by Easy Subtitles Synchronizer 1.0.0.0 55645

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