WEBVTT 1 00:00:03.399 --> 00:00:07.719 Welcome to Bedtime Astronomy. Explore the wonders of the cosmos 2 00:00:07.759 --> 00:00:12.279 with our soothing Bedtime Astronomie podcast. Each episode offers a 3 00:00:12.359 --> 00:00:16.320 gentle journey through the stars, planets, and beyond, perfect for 4 00:00:16.399 --> 00:00:20.239 unwinding after a long day. Let's travel through the mysteries 5 00:00:20.239 --> 00:00:22.440 of the universe as you drift off into a peaceful 6 00:00:22.480 --> 00:00:23.800 slumber under the night sky. 7 00:00:26.879 --> 00:00:28.640 So I want you to imagine, just for a second, 8 00:00:28.679 --> 00:00:31.600 that you're standing outside on a clear, dark night in 9 00:00:31.640 --> 00:00:33.359 the Southern Hemisphere. 10 00:00:32.920 --> 00:00:35.079 Right away from all the city lights hopefully. 11 00:00:34.759 --> 00:00:37.320 Yeah, exactly, way out in the middle of nowhere. You 12 00:00:37.359 --> 00:00:40.399 look up, away from the familiar constellations you might know, 13 00:00:40.759 --> 00:00:44.960 and your eyes catch this funny, bright patch of light 14 00:00:45.119 --> 00:00:45.960 in the sky. 15 00:00:46.280 --> 00:00:48.759 Which pretty noticeable even to the naked eye. 16 00:00:48.799 --> 00:00:52.880 It is, and for centuries, basically anyone who looked at 17 00:00:52.880 --> 00:00:55.240 it just assumed it was a star, you know, just 18 00:00:55.320 --> 00:00:58.079 the single, maybe slightly smudged star. 19 00:00:58.280 --> 00:00:59.719 Yeah, bit out of focus maybe. 20 00:01:00.240 --> 00:01:02.320 But if you were to take a powerful telescope and 21 00:01:02.359 --> 00:01:05.519 actually zoom in on that one little patch, you wouldn't 22 00:01:05.519 --> 00:01:10.079 find a star at all. You'd find this chaotic, impossibly 23 00:01:10.159 --> 00:01:14.480 dense swarm of roughly ten million stars all bound together 24 00:01:14.519 --> 00:01:15.159 by gravity. 25 00:01:15.239 --> 00:01:18.079 The sheer scale of that visual shift is just profound. 26 00:01:18.120 --> 00:01:20.439 I mean, what registers to your eye as a solitary 27 00:01:20.439 --> 00:01:24.200 point of light is in reality, this sprawling metropolis of stars. 28 00:01:24.400 --> 00:01:27.319 It's why it really is. It forces a complete recalibration 29 00:01:27.640 --> 00:01:29.840 of how you perceive the nice guy, you know. 30 00:01:30.079 --> 00:01:33.200 And today we're heading right into the heart of that metropolis. 31 00:01:33.519 --> 00:01:37.439 We are exploring a historic astronomical breakthrough from July twenty 32 00:01:37.480 --> 00:01:40.719 twenty six, which is the discovery of an object known 33 00:01:40.760 --> 00:01:43.040 as Omega cat BH two. 34 00:01:43.519 --> 00:01:44.359 Very catchy name. 35 00:01:44.439 --> 00:01:47.079 Oh, astronomers are the best at naming things, right, But 36 00:01:47.159 --> 00:01:51.120 this is actually the very first confirmed stellar mass black 37 00:01:51.159 --> 00:01:56.200 hole inside that massive stellar swarm, which is called Omega Centauri. 38 00:01:56.760 --> 00:02:00.079 Yeah, and the hunt for this particular object represents and 39 00:02:00.200 --> 00:02:04.480 honestly one of the most complex detective stories in modern astrophysics. 40 00:02:04.519 --> 00:02:05.680 Oh, absolutely, because it. 41 00:02:05.640 --> 00:02:09.280 Required astronomers to completely abandon their traditional methods of finding 42 00:02:09.280 --> 00:02:12.960 black holes, and they basically had to invent an entirely new, 43 00:02:13.159 --> 00:02:15.599 incredibly patient way of analyzing the universe. 44 00:02:15.719 --> 00:02:17.919 So the mission for our conversation today is to really 45 00:02:17.919 --> 00:02:20.439 figure out the mechanics of that detective work. We're going 46 00:02:20.479 --> 00:02:23.759 to explore how astronomers finally managed to find an invisible 47 00:02:23.800 --> 00:02:26.479 object that had just been hiding in plain sight for. 48 00:02:26.439 --> 00:02:28.520 Decades, hiding very quietly, too. 49 00:02:28.759 --> 00:02:31.639 Exactly, and more importantly, we're going to break down how 50 00:02:31.879 --> 00:02:36.639 this single, very quiet discovery fundamentally rewrites the physics of 51 00:02:36.639 --> 00:02:41.240 how galaxies evolve, how stars interact, and really how black 52 00:02:41.280 --> 00:02:43.039 holes themselves even come to be. 53 00:02:43.039 --> 00:02:47.120 Because finding a black hole that isn't actively consuming matter, 54 00:02:47.680 --> 00:02:49.400 you know, one that's just sitting there in the dark, 55 00:02:49.599 --> 00:02:53.400 it requires an understanding of orbital dynamics and data analysis 56 00:02:53.439 --> 00:02:55.439 that basically borders on the extreme right. 57 00:02:55.639 --> 00:02:58.000 But to understand the weight of that achievement, we really 58 00:02:58.000 --> 00:02:59.479 have to start by setting the scene. 59 00:02:59.520 --> 00:03:01.960 I think, Yeah, let's look at the crime scene. 60 00:03:01.719 --> 00:03:05.759 The cosmic crime scene Omega Centauri or NNGC five one 61 00:03:05.719 --> 00:03:08.400 thirty nine if you prefer the catalog name. Let's paint 62 00:03:08.439 --> 00:03:11.560 the picture of this environment because it honestly defies common sense, 63 00:03:11.599 --> 00:03:12.159 it really does. 64 00:03:12.280 --> 00:03:12.360 So. 65 00:03:12.439 --> 00:03:15.439 This object is located about eighteen thousand light years away 66 00:03:15.479 --> 00:03:19.159 from us. It contains roughly ten million stars, which translates 67 00:03:19.199 --> 00:03:22.159 to somewhere between what three point six to four million 68 00:03:22.240 --> 00:03:23.919 times the mass of our own sun. 69 00:03:24.159 --> 00:03:26.800 Yeah, that's the current estimate. It's incredibly heavy. 70 00:03:26.680 --> 00:03:29.280 But all of that mass is packed into a spherical 71 00:03:29.319 --> 00:03:31.520 area just one hundred and fifty light years acros, which 72 00:03:31.560 --> 00:03:32.360 is mind boggling. 73 00:03:32.520 --> 00:03:34.800 Just to put that one hundred and fifty light year 74 00:03:34.840 --> 00:03:38.080 diameter into perspective. You know, the closest star system to 75 00:03:38.159 --> 00:03:40.000 our Sun is Alpha Centauri. 76 00:03:39.879 --> 00:03:43.199 Right, which is about four light years away exactly. 77 00:03:43.319 --> 00:03:46.360 So in our stellar neighborhood, space is mostly just that, 78 00:03:46.479 --> 00:03:50.120 it's empty space. But in the core of Omega Centauri, 79 00:03:50.599 --> 00:03:53.639 the average distance between stars is a tiny fraction of 80 00:03:53.680 --> 00:03:54.199 a light year. 81 00:03:54.919 --> 00:03:56.879 I was actually trying to wrap my head around that density, 82 00:03:56.919 --> 00:03:59.199 and I came up with this analogy. It's basically like 83 00:03:59.280 --> 00:04:01.159 taking the entire population of New. 84 00:04:01.120 --> 00:04:03.560 York City booth is a good one, yeah, all eight 85 00:04:03.599 --> 00:04:07.639 million people, and forcing them to live, work, and just 86 00:04:08.360 --> 00:04:13.000 exist entirely inside the borders of a single tiny rural village. 87 00:04:13.080 --> 00:04:14.400 It's just absolute crowding. 88 00:04:14.479 --> 00:04:16.120 Yeah, the crowding is just absolute. 89 00:04:16.199 --> 00:04:18.839 And that visual works on a gravitational level too. The 90 00:04:18.879 --> 00:04:22.800 sheer proximity of the stellar neighbors basically dictates the physics 91 00:04:22.800 --> 00:04:25.920 of the entire region. I mean, if Earth were somehow 92 00:04:25.959 --> 00:04:29.199 relocated into the core of Omegasentauri. Our night sky wouldn't 93 00:04:29.199 --> 00:04:29.720 even be dark. 94 00:04:29.759 --> 00:04:31.240 Wait, really, it would just be daylight. 95 00:04:31.439 --> 00:04:34.720 Well not daylight, but it would be blazing with thousands 96 00:04:34.800 --> 00:04:38.240 of stars that appear brighter than Venus does to us. Now, 97 00:04:39.160 --> 00:04:41.560 the ambient light would be so intense you could likely 98 00:04:41.600 --> 00:04:43.519 read a book by starlight alone. 99 00:04:43.639 --> 00:04:44.800 Oh wow. 100 00:04:45.000 --> 00:04:48.639 Yeah, you'd be casting distinct shadows at midnight, which. 101 00:04:48.439 --> 00:04:51.959 Sounds super poetic. But when you think about the gravitational 102 00:04:52.040 --> 00:04:55.920 reality of that, it would be absolute chaos, just millions 103 00:04:55.920 --> 00:04:59.040 of massive objects constantly pulling on each other exactly. And 104 00:04:59.120 --> 00:05:01.759 yet the dense t isn't even the weirdest part about 105 00:05:01.759 --> 00:05:04.959 Omega Centauri? Is it? Because it stands out from basically 106 00:05:05.000 --> 00:05:07.000 every other star cluster in the Milky Way for a 107 00:05:07.040 --> 00:05:07.959 totally different reason. 108 00:05:08.160 --> 00:05:11.199 Yeah, what's fascinating here is the anomaly in its chemical 109 00:05:11.279 --> 00:05:12.720 and kinematic complexity. 110 00:05:12.879 --> 00:05:14.600 Okay, unpack that for me, sure. 111 00:05:14.839 --> 00:05:18.319 So to understand why Omegasentauri breaks the rules, we first 112 00:05:18.360 --> 00:05:20.959 need to look at what a standard globular cluster is 113 00:05:21.000 --> 00:05:25.279 supposed to be. In astrophysics, a normal globular cluster is 114 00:05:25.319 --> 00:05:28.000 considered a simple stellar. 115 00:05:27.680 --> 00:05:30.279 Population, meaning they're all kind of the same right. 116 00:05:31.000 --> 00:05:33.360 The prevailing theory is that all the stars in a 117 00:05:33.399 --> 00:05:38.160 standard cluster formed in a single massive burst of star formation, 118 00:05:38.680 --> 00:05:41.600 all from the exact same giant cloud of molecular gas. 119 00:05:41.800 --> 00:05:43.920 Oh I see, So they're basically like a graduating class 120 00:05:43.920 --> 00:05:46.199 of stars. They were all born at the exact same 121 00:05:46.279 --> 00:05:48.079 time from the exact same material. 122 00:05:48.199 --> 00:05:50.879 That's a perfect way to put it. Therefore, they share 123 00:05:50.920 --> 00:05:54.639 the same age and the same basic chemical composition. When 124 00:05:54.639 --> 00:05:57.920 we look at their light spectra the signatures of elements 125 00:05:58.000 --> 00:06:02.519 like iron or oxygen, they're largely uniform across the whole cluster. 126 00:06:02.279 --> 00:06:04.560 Because they all baked in the same oven exactly. 127 00:06:05.199 --> 00:06:09.439 But when astronomers apply that same spectroscopic analysis to Omega centauri, 128 00:06:10.120 --> 00:06:11.959 the data is just completely fractured. 129 00:06:12.079 --> 00:06:13.279 It doesn't match, not at all. 130 00:06:13.360 --> 00:06:15.759 We see multiple distinct populations of stars in there, the 131 00:06:15.879 --> 00:06:19.920 completely different ages and their chemical makeups very wildly huh. 132 00:06:20.120 --> 00:06:22.480 And furthermore, they don't even move together in a simple 133 00:06:22.560 --> 00:06:26.800 uniform orbit. The kinematics, the actual physical motion of the 134 00:06:26.839 --> 00:06:30.639 stars shows distinct groups moving in completely different ways. 135 00:06:30.920 --> 00:06:33.519 So if it doesn't look or act like a normal 136 00:06:33.720 --> 00:06:37.279 uniform cluster, the obvious deduction is that it didn't form 137 00:06:37.399 --> 00:06:41.000 like one, right, right, So what is the alternative mechanism, like, 138 00:06:41.040 --> 00:06:44.879 what creates a massive chaotic ball of stars with all 139 00:06:44.920 --> 00:06:46.519 these different ages and chemicals. 140 00:06:46.560 --> 00:06:48.800 Well, the leading theory, and really the only one that 141 00:06:48.879 --> 00:06:53.480 successfully accounts for this bizarre data, is that Omega Centauri 142 00:06:53.680 --> 00:06:56.759 is not actually a true globular cluster at all. 143 00:06:56.879 --> 00:06:58.560 Wait, really, then what is it? 144 00:06:58.639 --> 00:07:02.079 The overwhelming consensus now is that it's the stripped remnant 145 00:07:02.120 --> 00:07:04.240 core of an ancient dwarf galaxy. 146 00:07:04.319 --> 00:07:07.120 Oh wow, Meaning it used to be a completely independent 147 00:07:07.160 --> 00:07:09.959 galaxy just floating out in the universe, totally separate from 148 00:07:09.959 --> 00:07:10.600 the Milky Way. 149 00:07:10.680 --> 00:07:14.879 Exactly billions of years ago, this dwarf galaxy ventured a 150 00:07:14.920 --> 00:07:17.199 little too close to the Milky Way, and our galaxy 151 00:07:17.319 --> 00:07:21.160 is vastly more massive, so it's immense gravity just went 152 00:07:21.199 --> 00:07:21.480 to work. 153 00:07:21.560 --> 00:07:22.879 It bullied the smaller galaxy. 154 00:07:23.000 --> 00:07:25.759 Yeah, through a process called tidal stripping, the Milky Way 155 00:07:25.839 --> 00:07:29.560 essentially cannibalized it. The gravitational tides literally ripped away all 156 00:07:29.560 --> 00:07:32.319 the outer layers of stars, all the loose gas that. 157 00:07:32.399 --> 00:07:34.040 Dust keeled it like an onion. 158 00:07:33.920 --> 00:07:36.560 Right, stretched them out into these long streams and pulled 159 00:07:36.600 --> 00:07:38.639 them into our galaxy's own halo. 160 00:07:38.959 --> 00:07:42.279 So the Milky Way basically ate the outer layers, and 161 00:07:42.439 --> 00:07:45.759 Omegasentory is just the dense pit left over after the 162 00:07:45.759 --> 00:07:47.079 peach was devoured. 163 00:07:46.879 --> 00:07:51.000 A very massive, extremely old pit. Yes, we are looking 164 00:07:51.040 --> 00:07:53.680 at a core that is roughly twelve billion years old. 165 00:07:53.800 --> 00:07:56.160 Twelve billion that is, I mean the universe itself is 166 00:07:56.199 --> 00:07:58.959 only about thirteen point eight billion years old, right exactly. 167 00:07:58.600 --> 00:07:59.240 So it's ancient. 168 00:07:59.439 --> 00:07:59.839 Yeah. 169 00:08:00.120 --> 00:08:03.480 And because of this extreme age and this intense gravitational crowning, 170 00:08:03.879 --> 00:08:08.120 Amegasentury serves as this perfect natural laboratory. It allows us 171 00:08:08.120 --> 00:08:11.720 to observe stellar evolution pushed to its absolute limits. 172 00:08:11.759 --> 00:08:14.040 Because we're seeing the endgame, right, we. 173 00:08:14.000 --> 00:08:16.160 Can see what happens when stars are forced to live 174 00:08:16.199 --> 00:08:18.680 out their entire life cycles from birth to death in 175 00:08:18.720 --> 00:08:22.079 an environment where they are just constantly interacting with their neighbors. 176 00:08:21.680 --> 00:08:24.600 Which sets up the central mystery of this entire deep dive. 177 00:08:25.160 --> 00:08:27.959 Because of that twelve billion year age and the sheer 178 00:08:28.079 --> 00:08:31.519 number of massive stars that must have existed there, physicists 179 00:08:31.519 --> 00:08:34.480 looked at a Megasinaury and realize it should be an 180 00:08:34.600 --> 00:08:37.799 absolute graveyard of massive dead stars. 181 00:08:38.240 --> 00:08:41.720 It absolutely should be. The absence of those dead stars 182 00:08:42.399 --> 00:08:46.000 was one of the most glaring discrepancies in stellar astrophysics 183 00:08:46.039 --> 00:08:46.799 for decades. 184 00:08:47.039 --> 00:08:49.600 The math didn't match the reality, not even close. 185 00:08:50.120 --> 00:08:54.720 The observational data fundamentally contradicted the established mathematical. 186 00:08:54.159 --> 00:08:56.600 Models, and this became known as the Great black hole 187 00:08:56.759 --> 00:09:00.000 draught of omegasentaury, the drought. Yes, so let's break down 188 00:09:00.080 --> 00:09:02.519 on the mechanics of this drought, because the physics of 189 00:09:02.639 --> 00:09:05.960 stellar death basically guarantees they should be there, right, Like, 190 00:09:06.039 --> 00:09:08.639 we know that the most massive stars burn through their 191 00:09:08.720 --> 00:09:11.399 nuclear fuel incredibly. 192 00:09:10.720 --> 00:09:12.440 Fast, live fast, die young. 193 00:09:12.679 --> 00:09:15.480 Right, They live for maybe a few million years, exhaust 194 00:09:15.559 --> 00:09:20.320 their energy, and die in these massive supernova explosions, and 195 00:09:20.399 --> 00:09:23.960 the crushed cores they leave behind become stellar mass black hole. 196 00:09:24.080 --> 00:09:27.039 Yeah, these are black holes with masses ranging from a 197 00:09:27.039 --> 00:09:29.840 few times that of our Sun to perhaps a few 198 00:09:29.919 --> 00:09:32.679 tens of solar masses. And when you take a starting 199 00:09:32.720 --> 00:09:35.480 population of ten million stars and you let the clock 200 00:09:35.600 --> 00:09:37.480 run for twelve billion years. 201 00:09:37.320 --> 00:09:39.799 That's a lot of supernovas, a huge amount. 202 00:09:39.960 --> 00:09:43.159 You can actually calculate what we call the initial mass function, 203 00:09:43.559 --> 00:09:47.440 which is basically the statistical distribution of how many stars 204 00:09:47.639 --> 00:09:49.879 of each size were born in that cluster. 205 00:09:50.080 --> 00:09:51.240 And what did the model say? 206 00:09:51.399 --> 00:09:55.519 The computer models were completely unambiguous. They calculated that roughly 207 00:09:55.600 --> 00:09:59.279 ten thousand stellar mass black holes should be left. 208 00:09:59.080 --> 00:10:02.799 Over lurking inside this one cluster. 209 00:10:02.639 --> 00:10:05.759 Ten thousand black holes. And the models actually went further 210 00:10:05.840 --> 00:10:08.879 than just predicting their existence too, they predicted their exact 211 00:10:08.919 --> 00:10:09.759 location because. 212 00:10:09.519 --> 00:10:11.840 They wouldn't just stay where they died, right exactly. 213 00:10:12.279 --> 00:10:16.440 In a dense environment like a globular cluster, objects don't 214 00:10:16.480 --> 00:10:19.279 just stay where they're born. They're subject to a process 215 00:10:19.320 --> 00:10:20.639 known as dynamical friction. 216 00:10:20.879 --> 00:10:23.039 Okay, I want to pause on dynamical friction for a second, 217 00:10:23.080 --> 00:10:27.440 because friction in the vacuum of space sounds totally counterintuitive. 218 00:10:27.559 --> 00:10:28.399 It does sound a bit weird. 219 00:10:28.480 --> 00:10:31.440 Yeah, Like there's no air, there's no physical surface to 220 00:10:31.519 --> 00:10:35.240 rub against. How does a black hole experience friction? 221 00:10:35.879 --> 00:10:39.519 Well, the term is slightly metaphorical, but the physical effect 222 00:10:39.559 --> 00:10:43.080 is identical to friction. It's entirely gravitational. Picture a very 223 00:10:43.159 --> 00:10:45.799 heavy object like one of these stellar mass black holes, 224 00:10:46.240 --> 00:10:49.679 and it's moving through a dense sea of much lighter objects, 225 00:10:49.759 --> 00:10:53.399 which would be the normal main sequence stars. As the 226 00:10:53.399 --> 00:10:57.200 black hole moves, its strong gravity pulls slightly on all 227 00:10:57.240 --> 00:10:58.759 the lighter stars it passes by. 228 00:10:58.960 --> 00:11:02.000 Oh so it alters the trajectories, pulling them inward toward 229 00:11:02.000 --> 00:11:02.960 its own path. 230 00:11:02.919 --> 00:11:06.559 Exactly, and as those lighter stars are pulled inward, they 231 00:11:06.600 --> 00:11:09.200 form a region of higher density behind the black hole. 232 00:11:09.720 --> 00:11:12.879 It's effectively a gravitational wake, much like the wake of 233 00:11:12.960 --> 00:11:14.679 boat leaves as it moves through water. 234 00:11:14.799 --> 00:11:18.039 Okay, that makes sense. And that wake of clustered stars 235 00:11:18.080 --> 00:11:21.480 obviously has mass, which means it has a collective gravitational 236 00:11:21.480 --> 00:11:22.159 pull of its own. 237 00:11:22.200 --> 00:11:24.840 You've got it. So that backward pull from the wake 238 00:11:25.440 --> 00:11:27.919 actually SAPs the black hole's kinetic energy. 239 00:11:27.960 --> 00:11:30.639 So the black hole creates a cluster of stars behind it, 240 00:11:30.759 --> 00:11:33.879 and then the gravity of that cluster pulls backward on 241 00:11:33.960 --> 00:11:35.799 the black hole itself, slowing it down. 242 00:11:35.919 --> 00:11:39.519 Yes, it loses momentum. And in the orbital mechanics of 243 00:11:39.559 --> 00:11:42.759 a star cluster, when a massive object loses kinetic energy, 244 00:11:43.000 --> 00:11:46.960 its orbit shrinks. It essentially falls deeper into the gravitational well. 245 00:11:47.120 --> 00:11:49.360 It sinks toward the very center of the cluster. 246 00:11:49.840 --> 00:11:53.399 Precisely, and because of the conservation of energy, the lighter 247 00:11:53.440 --> 00:11:56.480 stars that made up that wake, they must be gaining 248 00:11:56.519 --> 00:11:58.679 the kinetic energy that the black hole lost. 249 00:11:58.879 --> 00:12:00.960 Oh, so they get pushed outward. 250 00:12:00.720 --> 00:12:03.960 Right the heavy objects sink to the core and the 251 00:12:04.039 --> 00:12:08.200 lighter objects puff outward. When you apply this process of 252 00:12:08.279 --> 00:12:11.879 dynamical friction over a span of twelve billion years, the 253 00:12:11.919 --> 00:12:16.240 physics dictates that virtually all of those ten thousand predicted 254 00:12:16.279 --> 00:12:19.960 black holes should have plummeted straight into the densely packed 255 00:12:20.000 --> 00:12:21.720 core of omegasentauri. 256 00:12:21.879 --> 00:12:24.320 Okay, but if I'm an astronomer looking at this model, 257 00:12:24.399 --> 00:12:28.000 I immediately see a massive logical problem, which is, well, 258 00:12:28.080 --> 00:12:30.600 if you take ten thousand black holes and you force 259 00:12:30.639 --> 00:12:33.279 them all to sink into the exact same, tiny, crowded 260 00:12:33.279 --> 00:12:36.320 central core, shouldn't they be causing absolute havoc? 261 00:12:36.559 --> 00:12:37.759 You would think so, right. 262 00:12:37.639 --> 00:12:39.879 Like they should be colliding with each other, gobbling up 263 00:12:39.919 --> 00:12:41.720 all the normal stars that are packed in there, and 264 00:12:41.759 --> 00:12:44.519 setting off these massive, bright flares of radiation that we 265 00:12:44.519 --> 00:12:47.519 can easily see from Earth. How do you just lose 266 00:12:47.639 --> 00:12:49.720 ten thousand black holes in a crowded room. 267 00:12:49.840 --> 00:12:53.240 It's a great question, But the assumption that they should 268 00:12:53.240 --> 00:12:56.679 be setting off flares is exactly where traditional observation hits 269 00:12:56.679 --> 00:13:00.240 its limit. To really understand the drought, we have to 270 00:13:00.279 --> 00:13:03.519 examine the limitations of our own technology. 271 00:13:02.960 --> 00:13:05.519 Because we don't actually see black holes exactly. 272 00:13:05.720 --> 00:13:09.000 We don't see them. We detect the radiation generated by 273 00:13:09.360 --> 00:13:11.360 the material they are actively consuming. 274 00:13:11.559 --> 00:13:15.080 Right, the classic accretion disc model, the black hole's gravity 275 00:13:15.159 --> 00:13:18.360 pulls in gas from a nearby companion star or maybe 276 00:13:18.399 --> 00:13:21.480 a passing cloud, Yes, and then that gas swirls around 277 00:13:21.519 --> 00:13:24.720 the black hole, accelerating to a significant fraction of the 278 00:13:24.759 --> 00:13:28.840 speed of light. The friction within that swirling gas superheats 279 00:13:28.840 --> 00:13:32.559 it to millions of degrees, causing it to blast out 280 00:13:32.679 --> 00:13:36.000 high energy X rays or radio waves right before it 281 00:13:36.039 --> 00:13:37.320 crosses the event horizon. 282 00:13:37.480 --> 00:13:40.080 And that mechanism is how we confirm the existence of 283 00:13:40.120 --> 00:13:43.720 early candidates like signets X one for example. Right, But 284 00:13:43.799 --> 00:13:46.799 the generation of those X rays is entirely dependent on 285 00:13:46.879 --> 00:13:51.159 an active, plentiful food supply. The black hole literally needs 286 00:13:51.279 --> 00:13:55.360 loose interstellar gas or a companion star positioned perfectly to 287 00:13:55.399 --> 00:13:55.919 be siphoned. 288 00:13:55.960 --> 00:13:58.399 And you're saying omegasentry is lacking that food supply. 289 00:13:58.600 --> 00:14:01.080 It is entirely of loose gas. 290 00:14:01.720 --> 00:14:04.120 How is that possible with ten million stars? 291 00:14:04.200 --> 00:14:07.159 Well, consider the history of the cluster. Over the first 292 00:14:07.200 --> 00:14:10.960 few hundred million years of its twelve billion year life, 293 00:14:11.000 --> 00:14:13.279 thousands of massive stars went supernova. 294 00:14:13.519 --> 00:14:15.480 Right, The early fast burning ones. 295 00:14:15.240 --> 00:14:19.039 Exactly, and the sheer kinetic force of those explosions, combined 296 00:14:19.080 --> 00:14:22.480 with the intense radiation pressure from millions of other stars, 297 00:14:22.840 --> 00:14:25.200 it all acted as a giant cosmic broom. 298 00:14:25.399 --> 00:14:28.279 Oh so the energy blasted all the loose gas and 299 00:14:28.360 --> 00:14:30.919 dust completely out of the cluster's gravitational hole. 300 00:14:30.840 --> 00:14:34.480 Billions of years ago. Yeah, the pantry was swept completely clean. Therefore, 301 00:14:34.519 --> 00:14:37.080 the vast majority of these black holes have absolutely nothing 302 00:14:37.080 --> 00:14:37.600 to consume. 303 00:14:37.960 --> 00:14:40.600 And a starving black hole is a silent black. 304 00:14:40.360 --> 00:14:44.480 Hole, perfectly silent without an accretion disc generating X rays. 305 00:14:44.480 --> 00:14:47.480 It is just a completely dark sphere of extreme gravity 306 00:14:47.720 --> 00:14:51.480 sitting against the black backdrop of space. X ray observatories 307 00:14:51.480 --> 00:14:54.200 could stare at the core of omegasentaury for years and 308 00:14:54.200 --> 00:14:57.200 see basically nothing but the faint signatures of a few 309 00:14:57.320 --> 00:14:58.759 normal stellar binaries. 310 00:14:59.000 --> 00:15:02.159 Okay, that perfectly explains the lack of X rays. But 311 00:15:02.639 --> 00:15:05.039 X rays aren't the only tool in the astronomer's box, 312 00:15:05.120 --> 00:15:10.240 right What about radial velocity? Ah, radial velocity, because that's 313 00:15:10.279 --> 00:15:13.279 the technique astronomers use to find exo planets all the time. 314 00:15:13.879 --> 00:15:16.679 You look for the physical wobble of a star, like 315 00:15:16.759 --> 00:15:19.679 if a visible star is orbiting an invisible black hole. 316 00:15:20.120 --> 00:15:22.200 The gravity of the black hole will yank the star 317 00:15:22.240 --> 00:15:25.320 in a circle correct So from Earth we would see 318 00:15:25.320 --> 00:15:28.039 the star being pulled slightly toward us and then pushed 319 00:15:28.120 --> 00:15:29.360 slightly away from us. 320 00:15:29.279 --> 00:15:32.559 A Doppler shift. As the star moves towards us, its 321 00:15:32.679 --> 00:15:35.320 light waves get compressed, shifting toward the blue end of 322 00:15:35.320 --> 00:15:38.840 the spectrum, and as it moves away, the waves stretch out, 323 00:15:39.120 --> 00:15:40.279 shifting toward the red end. 324 00:15:40.480 --> 00:15:43.360 Exactly. So why didn't astronomers just look for stars in 325 00:15:43.399 --> 00:15:46.279 the core of omegasonry that were shifting red and blue. 326 00:15:46.879 --> 00:15:49.679 The black holes might be invisible, but their gravity would 327 00:15:49.720 --> 00:15:52.039 be throwing the visible stars around like rag dolls. 328 00:15:52.559 --> 00:15:55.919 Well, the physics of the Doppler shift works perfectly, but 329 00:15:56.000 --> 00:15:59.960 the application of radial velocity requires an environment that omegasonri 330 00:16:00.360 --> 00:16:02.240 simply refuses to provide. 331 00:16:02.440 --> 00:16:03.320 It's too crowded. 332 00:16:03.480 --> 00:16:06.519 It's way too crowded. To measure that subtle red and 333 00:16:06.519 --> 00:16:09.720 blue shift, an astronomer must capture the light from one 334 00:16:09.879 --> 00:16:14.039 single specific star and feed it into a spectrograph. 335 00:16:14.120 --> 00:16:15.799 Right the prism that breaks the light apart. 336 00:16:16.000 --> 00:16:19.279 Yes, the spectrograph spreads the light out into a rainbow, 337 00:16:19.600 --> 00:16:22.440 revealing the dark absorption lines created by elements in the 338 00:16:22.440 --> 00:16:25.360 star's atmosphere, and the shifting of those lines is what 339 00:16:25.440 --> 00:16:26.519 tells you the velocity. 340 00:16:26.879 --> 00:16:29.600 So you have to strictly isolate the light, and. 341 00:16:29.519 --> 00:16:33.440 In the core of omegasentaury, isolating light is nearly impossible. 342 00:16:34.000 --> 00:16:37.279 The crowding is so severe that the light from thousands 343 00:16:37.320 --> 00:16:41.200 of faint stars just bleeds together. On our telescope sensors, it. 344 00:16:41.159 --> 00:16:42.120 All just washes out. 345 00:16:42.240 --> 00:16:45.000 It creates a blended wall of illumination. If you try 346 00:16:45.039 --> 00:16:47.200 to take a spectrum, you're getting the mashed up light 347 00:16:47.279 --> 00:16:50.480 of fifty different stars at once. You just cannot isolate 348 00:16:50.519 --> 00:16:53.679 the absorption lines of one specific star well enough to 349 00:16:53.720 --> 00:16:57.120 measure the tiny, subtle wabble caused by a quiescent black hole. 350 00:16:57.240 --> 00:17:00.720 Wow. So traditional astronomy basically hit a brick wall. The 351 00:17:00.759 --> 00:17:03.919 mathematical models demanded the black holes be there, but the 352 00:17:03.960 --> 00:17:07.240 two primary methods of finding them were completely useless. 353 00:17:07.359 --> 00:17:09.960 Yeah, X rays failed because there was no gas to eat, 354 00:17:10.400 --> 00:17:13.759 and radio velocity failed because the cluster was just a 355 00:17:13.799 --> 00:17:15.319 blinding wall of blended light. 356 00:17:15.640 --> 00:17:17.359 The ghosts were hiding in the noise. 357 00:17:17.480 --> 00:17:19.319 That's a very poetic way to say it, but yes, 358 00:17:19.720 --> 00:17:24.400 overcoming that barrier required a fundamental shift in strategy. Instead 359 00:17:24.440 --> 00:17:27.160 of looking for radiation or looking for the shifting color 360 00:17:27.200 --> 00:17:30.880 of light, astronomers had to invent a completely different game 361 00:17:30.920 --> 00:17:32.720 of cosmic hide and seek, and. 362 00:17:32.640 --> 00:17:35.839 They turned to a technique that requires, frankly, an almost 363 00:17:35.920 --> 00:17:41.039 unfathomable level of patience, data management, and precision, absolute precision, 364 00:17:41.119 --> 00:17:44.000 which takes us to the actual detective work. Jumping ahead 365 00:17:44.039 --> 00:17:46.640 to July twenty twenty six, a team of researchers led 366 00:17:46.680 --> 00:17:49.680 by Matthew Whitaker at the University of Utah finally cracked 367 00:17:49.680 --> 00:17:50.079 the case. 368 00:17:50.319 --> 00:17:53.920 Yes, they bypassed X rays and radio velocity entirely and 369 00:17:54.079 --> 00:17:57.000 utilize a technique called high precision astrometry. 370 00:17:57.039 --> 00:17:59.440 Okay, let's unpack this. What exactly is astrometry. 371 00:17:59.519 --> 00:18:04.240 Astronomer is, historically speaking, the oldest branch of astronomy. At 372 00:18:04.279 --> 00:18:07.960 its core, it's the painstaking measurement of a star's physical 373 00:18:08.039 --> 00:18:11.000 geometric position on the sky and then tracking how that 374 00:18:11.039 --> 00:18:12.400 position changes over time. 375 00:18:12.599 --> 00:18:17.440 Okay, so the distinction here is crucial. Radial velocity measures 376 00:18:17.480 --> 00:18:20.720 how a star moves toward or away from us along 377 00:18:20.759 --> 00:18:23.480 our line of sight. By analyzing the color of light, 378 00:18:24.319 --> 00:18:26.480 astrometry completely ignores. 379 00:18:26.079 --> 00:18:28.079 The color exactly it ignores the spectrum. 380 00:18:28.119 --> 00:18:31.240 It's measuring how a star moves side to side, vertically 381 00:18:31.279 --> 00:18:34.240 and horizontally across the two dimensional canvas of the sky. 382 00:18:34.480 --> 00:18:37.640 Yes, astronomers refer to this side to side movement as 383 00:18:37.839 --> 00:18:41.839 proper motion. Every star in Omega Centaury is in motion, 384 00:18:42.359 --> 00:18:45.319 naturally orbiting the center of mass of the cluster, So 385 00:18:45.400 --> 00:18:47.640 if you watch a star over a long enough period, 386 00:18:47.880 --> 00:18:49.279 you can just map its trajectory. 387 00:18:49.559 --> 00:18:53.319 But the distances we're talking about make this sound technologically impossible. 388 00:18:53.559 --> 00:18:57.319 Like Omega Centauri is eighteen thousand light years away. A 389 00:18:57.319 --> 00:18:59.599 star moving side to side at that distance, trying to 390 00:18:59.599 --> 00:19:01.000 track them from Earth. 391 00:19:00.759 --> 00:19:02.200 It's incredibly difficult. 392 00:19:02.279 --> 00:19:04.400 It sounds like trying to track the physical flight path 393 00:19:04.480 --> 00:19:06.960 of a single specific firefly in the middle of a 394 00:19:07.000 --> 00:19:10.319 blinding blizzard from hundreds of miles away, just to see 395 00:19:10.319 --> 00:19:12.839 if its flight path is being pulled slightly off course 396 00:19:12.880 --> 00:19:13.880 by an invisible string. 397 00:19:14.079 --> 00:19:18.079 That is very accurate analogy. The scale is completely daunting 398 00:19:18.799 --> 00:19:21.799 from our perspective on Earth. The physical movement of a 399 00:19:21.839 --> 00:19:27.160 star in Omegasentaury across the sky is microscopically small. We 400 00:19:27.240 --> 00:19:29.759 measure this movement in fractions of a milliarc second. 401 00:19:29.839 --> 00:19:32.200