WEBVTT FILE 1 00:00:00.367 --> 00:00:02.969 Black holes are wild. 2 00:00:04.637 --> 00:00:07.374 Yes, they are the most compact things we know of, so dense 3 00:00:07.374 --> 00:00:10.877 that even past a certain point, light cannot escape. 4 00:00:12.112 --> 00:00:14.214 Even though we can't see inside them, 5 00:00:14.214 --> 00:00:15.615 the environments around black holes 6 00:00:15.615 --> 00:00:19.552 are brimming with bizarre activity. 7 00:00:20.587 --> 00:00:22.856 There can be a corona of hot electrons 8 00:00:22.856 --> 00:00:24.924 that occasionally spits out 9 00:00:24.924 --> 00:00:26.359 scattered X-rays. 10 00:00:26.359 --> 00:00:29.062 There's a bright accretion disk of gas and dust 11 00:00:29.062 --> 00:00:31.631 whose light is so warped by gravity 12 00:00:31.765 --> 00:00:35.001 you can see the near and far sides 13 00:00:35.001 --> 00:00:36.136 at the same time. 14 00:00:38.138 --> 00:00:41.141 And I can't even begin to wrap my head around this estimate: 15 00:00:41.408 --> 00:00:44.611 There can be jets 20 million light-years across. 16 00:00:45.111 --> 00:00:47.781 That is 140 Milky Ways 17 00:00:47.781 --> 00:00:49.582 end-to-end. 18 00:00:50.116 --> 00:00:52.852 So if we can't see black holes themselves, 19 00:00:52.852 --> 00:00:55.455 we need other ways of understanding them, 20 00:00:55.455 --> 00:00:57.390 like these extreme surroundings. 21 00:00:57.390 --> 00:00:59.959 That's why NASA continues to create new instruments 22 00:00:59.959 --> 00:01:01.494 to decode the chaos. 23 00:01:02.629 --> 00:01:03.930 So is there anything 24 00:01:03.930 --> 00:01:06.533 common about a black hole environment? 25 00:01:06.533 --> 00:01:08.368 Let's break down what we know it. 26 00:01:08.501 --> 00:01:09.569 How does that process happen? 27 00:01:09.803 --> 00:01:10.670 How we know it? 28 00:01:10.670 --> 00:01:12.305 Where do you start with this? 29 00:01:12.305 --> 00:01:13.506 What am I looking at here? 30 00:01:13.506 --> 00:01:15.642 If you look closely, it's a big mess. 31 00:01:16.810 --> 00:01:19.712 And why we need to keep the questions coming. 32 00:01:19.712 --> 00:01:22.715 This is black hole environments explained. 33 00:01:24.751 --> 00:01:26.352 Not all black holes are the same 34 00:01:26.352 --> 00:01:27.987 or even chaotic. 35 00:01:28.254 --> 00:01:31.257 So scientists currently categorize black holes into four types. 36 00:01:31.458 --> 00:01:33.626 There are the ones that we've theorized exist 37 00:01:33.626 --> 00:01:35.628 like tiny primordial black holes, 38 00:01:35.628 --> 00:01:37.464 which formed shortly after the big bang. 39 00:01:38.364 --> 00:01:40.133 And intermediate-mass black holes 40 00:01:40.133 --> 00:01:42.469 that are sort of missing in the sense 41 00:01:42.469 --> 00:01:43.603 that they should be there 42 00:01:43.603 --> 00:01:45.405 but we haven't confirmed sighting. 43 00:01:45.872 --> 00:01:49.042 We've observed plenty of stellar-mass black holes 44 00:01:49.042 --> 00:01:51.878 that are at least eight times the mass of our Sun, 45 00:01:51.878 --> 00:01:53.947 and the leftovers of supernovae. 46 00:01:54.647 --> 00:01:56.916 The most dramatic by far, 47 00:01:56.916 --> 00:01:58.651 are the supermassive black holes, 48 00:01:58.651 --> 00:02:00.720 which are hundreds of thousands 49 00:02:00.720 --> 00:02:03.056 to billions of times more massive than our Sun. 50 00:02:03.056 --> 00:02:05.725 In fact, they can reach sizes so big 51 00:02:05.892 --> 00:02:07.160 they can span 52 00:02:07.160 --> 00:02:10.530 our entire solar system. 53 00:02:14.000 --> 00:02:16.136 When they're at the centers of galaxies, 54 00:02:16.136 --> 00:02:20.640 these monster black holes can become active galactic nuclei, 55 00:02:20.640 --> 00:02:22.342 or AGN. 56 00:02:22.342 --> 00:02:27.747 They fling a lot of material and they produce a lot of kinds of light. 57 00:02:28.148 --> 00:02:31.651 AGN are black holes at their wildest. 58 00:02:32.752 --> 00:02:34.787 Jenna Cann researches black holes 59 00:02:34.787 --> 00:02:37.657 and their signatures here at NASA Goddard. 60 00:02:37.657 --> 00:02:41.895 She agrees that AGN are the drama queens of space. 61 00:02:43.496 --> 00:02:45.698 I would call them the divas instead, 62 00:02:45.698 --> 00:02:47.600 but when you have an AGN, they want you 63 00:02:47.600 --> 00:02:49.836 to notice them as much as possible. 64 00:02:49.936 --> 00:02:52.338 They're singing in every single wavelength they can. 65 00:02:56.509 --> 00:02:58.578 But if you're looking at a full galaxy, 66 00:02:58.578 --> 00:03:00.313 do you almost just assume 67 00:03:00.313 --> 00:03:01.681 that there's a black hole there? 68 00:03:06.252 --> 00:03:07.954 When we have a massive galaxy, 69 00:03:07.954 --> 00:03:11.391 something that is like a billion times the mass of our Sun, 70 00:03:11.391 --> 00:03:14.928 we can pretty much safely assume there's going to be a black hole in there. 71 00:03:16.696 --> 00:03:21.034 When you get to the low-mass galaxies, which are the ones that I like studying the most, 72 00:03:21.034 --> 00:03:23.136 we don't know what's going on in them. 73 00:03:23.136 --> 00:03:25.738 But when you have a low-mass AGN, 74 00:03:25.738 --> 00:03:29.242 that light can be easily overshadowed by stars and everything there. 75 00:03:29.242 --> 00:03:32.312 So, you really need some kind of unambiguous 76 00:03:32.312 --> 00:03:35.381 stars can't mess around with this diagnostic. 77 00:03:35.915 --> 00:03:38.084 Where do you start with this? Right. 78 00:03:38.084 --> 00:03:41.688 You get a map of dots. 79 00:03:42.789 --> 00:03:45.658 And these dots mean what? 80 00:03:45.658 --> 00:03:48.361 What we'll do is take a spectra of our galaxy. 81 00:03:48.361 --> 00:03:51.531 and if we see highly ionized high-energy features, 82 00:03:51.531 --> 00:03:54.934 that’s good evidence that there is going to be an AGN there. 83 00:03:55.501 --> 00:03:59.639 Would you say that this is the best indicator of a black hole? 84 00:04:00.073 --> 00:04:01.841 That is very contentious! 85 00:04:02.141 --> 00:04:05.078 There is no one best option, basically. 86 00:04:05.078 --> 00:04:08.581 Every single tool that we have right now is fallible in some way, 87 00:04:08.581 --> 00:04:09.949 doesn't work in some environment. 88 00:04:11.317 --> 00:04:13.920 Enough talking about this environment like it's all uniform. 89 00:04:13.920 --> 00:04:16.656 We need a lesson in AGN anatomy. 90 00:04:20.627 --> 00:04:23.429 An AGN can have several different structures. 91 00:04:23.830 --> 00:04:26.633 The brightest feature is the accretion disk. 92 00:04:32.939 --> 00:04:35.708 In this Event Horizon Telescope radio image, 93 00:04:36.075 --> 00:04:39.212 we see the accretion disk around a supermassive black hole 94 00:04:39.212 --> 00:04:41.547 called M87*. 95 00:04:44.150 --> 00:04:47.253 This plane of gas and dust orbits the black hole 96 00:04:47.253 --> 00:04:51.090 and heats up through gravitational and frictional forces. 97 00:04:51.724 --> 00:04:56.129 It emits light all the way from radio to X-rays. 98 00:04:57.230 --> 00:05:00.933 Above and below the disk an AGN can have a corona. 99 00:05:01.334 --> 00:05:04.637 This superheated plasma of loose electrons 100 00:05:04.637 --> 00:05:06.372 emits a lot of X-rays. 101 00:05:06.673 --> 00:05:08.875 It's way less dense than the accretion disk 102 00:05:08.875 --> 00:05:10.376 but way hotter. 103 00:05:11.210 --> 00:05:13.880 For a long time, scientists wondered how the corona formed, 104 00:05:14.280 --> 00:05:17.016 how it was shaped, how it interacted with the rest of the environment. 105 00:05:17.317 --> 00:05:19.952 So a recent study with NASA's IXPE telescope 106 00:05:19.952 --> 00:05:21.721 shows that the observed coronas 107 00:05:21.721 --> 00:05:25.224 likely extend in a plane like the accretion disk 108 00:05:25.224 --> 00:05:28.361 and possibly are a lot larger than we previously thought. 109 00:05:29.962 --> 00:05:33.032 One of the best methods to learning more about these systems 110 00:05:33.032 --> 00:05:35.802 is through analyzing something we call coronal lines. 111 00:05:35.968 --> 00:05:41.074 Now Jenna uses spectroscopy to investigate coronal lines in AGN spectra. 112 00:05:41.507 --> 00:05:43.910 Yes, they look like squiggly graphs, 113 00:05:43.910 --> 00:05:46.179 but they tell us what elements are present 114 00:05:46.779 --> 00:05:49.749 and more importantly, what isn't present. 115 00:05:50.416 --> 00:05:52.785 So, a lot of the elements are ionized 116 00:05:52.885 --> 00:05:55.955 and are missing their electrons. 117 00:05:56.322 --> 00:06:00.560 So these are highly ionized emission lines. 118 00:06:01.294 --> 00:06:04.297 Six electrons have been removed from that ion. 119 00:06:04.864 --> 00:06:07.667 It's very, very bright in the center, which makes sense. 120 00:06:07.667 --> 00:06:09.902 That's the nucleus, that’s going to be the brightest there. 121 00:06:09.902 --> 00:06:12.205 And then it gets dimmer and dimmer as you go farther out. 122 00:06:12.205 --> 00:06:15.942 And they're pretty good evidence to there being an accreting black hole in there. 123 00:06:16.142 --> 00:06:19.145 Because it takes a lot of energy to even produce the ions 124 00:06:19.145 --> 00:06:20.646 that produce this emission. 125 00:06:22.315 --> 00:06:25.885 Despite AGN being some of the brightest objects in the universe, 126 00:06:25.885 --> 00:06:28.588 they can also sometimes hide behind 127 00:06:28.588 --> 00:06:29.555 a dusty torus. 128 00:06:30.189 --> 00:06:33.760 Now a torus is a thick, bagel-shaped structure 129 00:06:33.760 --> 00:06:36.629 that is so dense we can't see the AGN 130 00:06:36.662 --> 00:06:40.566 unless the bagel’s hole is facing one of our telescopes 131 00:06:41.300 --> 00:06:44.670 or you seek the energetic X-ray signals. 132 00:06:46.005 --> 00:06:50.076 Now, scientists using NASA's NuStar mission, another X-ray telescope, 133 00:06:50.076 --> 00:06:55.715 think that as many as 50% of black holes are obscured by a torus. 134 00:06:57.150 --> 00:06:58.518 These dusty cloaks 135 00:06:58.518 --> 00:07:01.521 can even impact a developing galaxy. 136 00:07:02.355 --> 00:07:06.459 A lot of that thick debris will make its way towards the black hole. 137 00:07:07.093 --> 00:07:10.029 And if too much of the dust falls towards it at once, 138 00:07:10.029 --> 00:07:13.032 it can cause the black hole to sort of cough or burp 139 00:07:13.032 --> 00:07:14.500 and a bunch of material 140 00:07:14.500 --> 00:07:17.370 comes out, and a hiccup that is big enough 141 00:07:17.370 --> 00:07:20.373 can even slow the rate of star formation. 142 00:07:20.640 --> 00:07:22.308 All of that is nothing 143 00:07:22.909 --> 00:07:24.710 compared to the achievements 144 00:07:24.710 --> 00:07:25.745 of a jet. 145 00:07:27.346 --> 00:07:29.215 So remember M87? 146 00:07:29.215 --> 00:07:32.084 Here's another image of it taken by our Hubble telescope. 147 00:07:32.718 --> 00:07:33.986 See that? 148 00:07:34.554 --> 00:07:37.190 That bright line is a black hole 149 00:07:37.190 --> 00:07:39.826 throwing a huge jet of particles 150 00:07:39.826 --> 00:07:42.829 moving at nearly the speed of light. 151 00:07:43.629 --> 00:07:45.164 It does make you wonder 152 00:07:45.164 --> 00:07:47.834 if black holes gather everything that comes too close, 153 00:07:48.901 --> 00:07:51.337 how does it propel particle jets? 154 00:07:51.604 --> 00:07:55.441 Cecilia Chirenti, an expert in math, physics, 155 00:07:55.441 --> 00:07:56.976 and the wonders of black holes, 156 00:07:56.976 --> 00:07:58.544 has some ideas how. 157 00:07:59.812 --> 00:08:00.980 So what is going on? 158 00:08:00.980 --> 00:08:03.916 Why are they ejecting a lot of things when it seems like 159 00:08:04.217 --> 00:08:06.819 what we know is that they suck things up? 160 00:08:07.053 --> 00:08:09.622 If you look closely, it's a big mess. 161 00:08:10.923 --> 00:08:13.426 If you haven't ever seen it before, 162 00:08:13.593 --> 00:08:16.329 you have to imagine that the black hole is in the center, 163 00:08:16.329 --> 00:08:18.931 the accretion disk is around it. 164 00:08:18.931 --> 00:08:20.500 Kind of think about, you know, the 165 00:08:20.500 --> 00:08:22.768 the rings of Saturn that are around the planet. 166 00:08:22.768 --> 00:08:25.771 You have this big accretion disk around a black hole 167 00:08:25.972 --> 00:08:28.741 and the jet is coming out like that. 168 00:08:28.741 --> 00:08:31.711 So you can think of a garden hose, you know, when it's 169 00:08:31.711 --> 00:08:36.048 spraying out there in the cosmic distances, right? 170 00:08:36.048 --> 00:08:37.783 Like really big. 171 00:08:37.783 --> 00:08:41.521 The matter in the jet has to be coming from somewhere. 172 00:08:41.521 --> 00:08:43.389 So it's coming from the disk. 173 00:08:43.389 --> 00:08:45.291 And the question is: 174 00:08:45.291 --> 00:08:47.693 How do the particles on the disk, 175 00:08:48.027 --> 00:08:50.763 how do they get accelerated, pulled out 176 00:08:50.796 --> 00:08:52.298 from the disk 177 00:08:52.298 --> 00:08:54.300 and directed outwards on the jet? 178 00:08:54.734 --> 00:08:58.104 So that is the mechanism that people try to study, 179 00:08:58.104 --> 00:09:01.040 and we have some ideas of how that works. 180 00:09:01.040 --> 00:09:03.109 Because if the black hole is spinning, 181 00:09:03.109 --> 00:09:04.010 you can 182 00:09:04.010 --> 00:09:07.947 steal a little bit of that rotational energy of the black hole 183 00:09:07.947 --> 00:09:09.982 and give it to something else. 184 00:09:10.550 --> 00:09:13.653 Cecilia went on to explain that these jets 185 00:09:13.653 --> 00:09:17.089 also form because of a black hole's magnetic fields. 186 00:09:19.759 --> 00:09:21.127 With the magnetic fields, 187 00:09:21.127 --> 00:09:22.395 what happens is that 188 00:09:22.395 --> 00:09:25.464 they are stealing a little bit of the energy, 189 00:09:25.464 --> 00:09:27.033 the rotational energy from the black hole. 190 00:09:27.033 --> 00:09:32.572 This extra energy in the magnetic fields is what is accelerating the particles 191 00:09:32.572 --> 00:09:35.207 in the disk to form a jet. 192 00:09:35.207 --> 00:09:38.844 That is kind of like the particle accelerators on Earth 193 00:09:38.844 --> 00:09:43.082 where we use magnetic fields for accelerating particles. 194 00:09:47.520 --> 00:09:49.355 Well beyond the black hole, 195 00:09:49.355 --> 00:09:53.993 the jet, the ionized and the energized particles, the X-rays and such, 196 00:09:53.993 --> 00:09:57.129 the gases just continue to spread. 197 00:09:59.932 --> 00:10:01.500 Because of their very nature, 198 00:10:01.500 --> 00:10:04.937 we will never see beyond a black hole's event horizon. 199 00:10:05.538 --> 00:10:08.941 We are doomed to see only the light that surrounds them. 200 00:10:10.142 --> 00:10:13.145 But there's still so many questions we can answer with that light. 201 00:10:14.113 --> 00:10:16.349 And with each new telescope we build, 202 00:10:16.349 --> 00:10:19.452 whether it peers through our atmosphere from the ground, 203 00:10:19.552 --> 00:10:22.488 or studies the cosmos from space, 204 00:10:22.488 --> 00:10:24.924 they give us more clues as to how 205 00:10:24.924 --> 00:10:28.327 and why black hole environments behave as they do.