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 --> 00:00:29.160 I want you to start by visualizing something with me. 8 00:00:30.160 --> 00:00:35.359 Picture a massive, heavy velvet tapestry and it's pitch black, 9 00:00:35.759 --> 00:00:40.240 absolutely lightless. But woven into this black fabric are these 10 00:00:40.479 --> 00:00:44.479 brilliant shimmering threads of gold and silver. It's a pretty 11 00:00:44.479 --> 00:00:46.079 classic image, right, Yeah. 12 00:00:45.840 --> 00:00:48.159 That's the standard metaphor for the universe. People call it 13 00:00:48.159 --> 00:00:49.159 the cosmic web. 14 00:00:49.200 --> 00:00:51.280 Right because when we look up at the night sky, 15 00:00:51.600 --> 00:00:54.280 or you know, we look at those incredible composite images 16 00:00:54.280 --> 00:00:57.039 from NASA, that is exactly what we see. We see 17 00:00:57.079 --> 00:01:01.000 the light. We see billions of galaxy whirling in the void, 18 00:01:01.159 --> 00:01:05.439 glowing with the heat of trillions of stars. We fundamentally 19 00:01:05.480 --> 00:01:07.519 define the universe by what shines. 20 00:01:07.239 --> 00:01:09.319 Well, because that is what our eyes are built to do. 21 00:01:09.760 --> 00:01:13.519 We are biological light detectors. Our entire history of astronomy, 22 00:01:13.719 --> 00:01:17.480 from the ancient Greeks drawing constellations to Hubble taking deep 23 00:01:17.519 --> 00:01:21.400 field images has been biased toward luminosity. 24 00:01:21.480 --> 00:01:23.799 If it glows, it exists exactly. 25 00:01:23.359 --> 00:01:25.760 And if it doesn't glow, we assume it's just empty 26 00:01:25.760 --> 00:01:26.840 space the void. 27 00:01:27.000 --> 00:01:29.599 But and this is why we are here today doing 28 00:01:29.599 --> 00:01:34.239 this exploration. What if that assumption is fundamentally flawed. 29 00:01:34.319 --> 00:01:35.439 It's a huge question. 30 00:01:35.680 --> 00:01:38.640 What if that tapestry is actually full of things woven 31 00:01:38.680 --> 00:01:43.519 with black thread against a black background, Objects that are massive, complex, 32 00:01:43.640 --> 00:01:48.280 and gravitationally significant, but effectively invisible. 33 00:01:48.400 --> 00:01:50.920 It is a really disquieting thought. When you dig into 34 00:01:50.920 --> 00:01:54.560 the research, it suggests that our map of the universe 35 00:01:54.680 --> 00:01:57.560 is not actually a map of mass. Oh interesting, Yeah, 36 00:01:57.599 --> 00:01:59.920 it's merely a map of light bulbs, and we might 37 00:02:00.200 --> 00:02:03.319 be missing the vast majority of the furniture in the room, 38 00:02:03.400 --> 00:02:04.000 so to speak. 39 00:02:04.239 --> 00:02:06.719 That is exactly what we are unpacking today. We're looking 40 00:02:06.760 --> 00:02:09.879 at a specific discovery from our sources that challenges the 41 00:02:10.039 --> 00:02:12.840 very definition of what a galaxy is. Yes, we are 42 00:02:12.840 --> 00:02:15.879 talking about a ghost hiding in the Perseus cluster, a 43 00:02:15.919 --> 00:02:17.400 galaxy named CDG two. 44 00:02:17.759 --> 00:02:20.919 CDG two is just a fascinating case study. It's an 45 00:02:20.960 --> 00:02:24.039 object that breaks the usual rules of galactic formation. 46 00:02:23.960 --> 00:02:26.199 Breaks the rules, feels like an understatement to me. When 47 00:02:26.240 --> 00:02:28.319 I was reading the research on this, one statistic jumped 48 00:02:28.319 --> 00:02:29.719 out and just sat there staring at me. 49 00:02:29.879 --> 00:02:31.599 The mass ratio, Yes. 50 00:02:31.719 --> 00:02:35.240 We usually think of galaxies as star factories, right, but 51 00:02:35.319 --> 00:02:38.199 this thing, this galaxy appears to be ninety nine percent 52 00:02:38.319 --> 00:02:39.039 dark matter. 53 00:02:38.919 --> 00:02:41.159 Ninety nine percent. It is an immense figure. 54 00:02:41.439 --> 00:02:44.800 So if I'm doing the math right, that leaves roughly 55 00:02:44.840 --> 00:02:47.599 one percent for the stuff we can actually see, you know, 56 00:02:47.680 --> 00:02:49.159 the stars, the gas, the. 57 00:02:49.159 --> 00:02:53.080 Dust, the buryonic matter, baryonic right, the normal stuff that 58 00:02:53.159 --> 00:02:56.039 makes up you, me, the Earth, and the Sun in 59 00:02:56.080 --> 00:02:59.919 this galaxy, all of that is essentially a rounding era 60 00:03:00.319 --> 00:03:01.560 that is just wild. 61 00:03:01.240 --> 00:03:03.000 To think about. But before we get too far into 62 00:03:03.039 --> 00:03:04.639 the wow factor of it all, I want to push 63 00:03:04.639 --> 00:03:06.639 back on this a little bit. We talk about dark 64 00:03:06.680 --> 00:03:09.520 matter a lot. We know our own Milky Way has 65 00:03:09.639 --> 00:03:13.120 dark matter. We know it's the gravitational glue that keeps 66 00:03:13.159 --> 00:03:17.240 galaxies from spinning apart. So is ninety nine percent actually 67 00:03:17.280 --> 00:03:19.319 that weird? What is the standard ratio? 68 00:03:19.680 --> 00:03:22.759 That is a very important distinction to make you are right? 69 00:03:22.840 --> 00:03:26.719 Almost every galaxy has a dark matter halo. But typically 70 00:03:26.960 --> 00:03:29.800 the cosmic ratio is about five to one fave to one, 71 00:03:29.960 --> 00:03:32.680 five parts dark matter to one part visible matter. 72 00:03:32.800 --> 00:03:35.240 Okay, so five to one versus ninety nine to one. 73 00:03:35.240 --> 00:03:38.280 Exactly In a normal galaxy like the Milky Way, the 74 00:03:38.400 --> 00:03:41.319 dark matter provides the structure that the visible matter, the 75 00:03:41.360 --> 00:03:44.360 gas and stars, has collapsed into the center to form 76 00:03:44.400 --> 00:03:45.719 a bright, churning. 77 00:03:45.439 --> 00:03:47.520 Disc right the spiral we always see. 78 00:03:47.599 --> 00:03:50.800 Yeah, the baryonic physics are very active. Yeah. In CDG two, 79 00:03:51.360 --> 00:03:53.800 that process seems to have short circuited. 80 00:03:53.479 --> 00:03:55.039 Entirely short circuited. 81 00:03:55.120 --> 00:03:57.800 How well, It's like a house built almost entirely of 82 00:03:57.840 --> 00:04:01.199 invisible bricks, with just a few effects of dust floating 83 00:04:01.240 --> 00:04:02.759 inside to prove it's actually. 84 00:04:02.560 --> 00:04:06.560 There, Which brings us to the definition problem. If you 85 00:04:06.680 --> 00:04:09.240 have a clump of dark matter with almost no stars, 86 00:04:09.840 --> 00:04:11.960 is it even a galaxy or is it just a 87 00:04:12.000 --> 00:04:13.919 halo that failed to do anything? 88 00:04:14.319 --> 00:04:17.120 That is the existential crisis as strongers are grappling with 89 00:04:17.199 --> 00:04:17.600 right now. 90 00:04:17.639 --> 00:04:18.439 Really, oh yeah. 91 00:04:18.680 --> 00:04:23.000 Traditionally a galaxy is defined by its starlight, but objects 92 00:04:23.000 --> 00:04:25.800 like CDG two suggest that a galaxy should really be 93 00:04:25.879 --> 00:04:30.879 defined by its gravitational potential. It's dark matter halo so. 94 00:04:30.839 --> 00:04:33.000 The stars are just an afterthought exactly. 95 00:04:33.040 --> 00:04:36.000 The stars are just the ornamentation, they aren't the structure itself. 96 00:04:36.279 --> 00:04:39.079 So our mission today for you listening is to understand 97 00:04:39.079 --> 00:04:40.879 this ghost. We aren't just going to gawk at the 98 00:04:40.959 --> 00:04:43.240 ninety nine percent number. We really need to understand the 99 00:04:43.279 --> 00:04:46.240 detective work here. The methodology is the best part, because 100 00:04:46.279 --> 00:04:49.680 finding something that emits almost no light in a universe 101 00:04:49.720 --> 00:04:53.000 that is incredibly big and incredibly dark seems like an 102 00:04:53.000 --> 00:04:54.000 impossible task. 103 00:04:54.160 --> 00:04:57.639 It borders on the impossible. This isn't just an observation, 104 00:04:57.680 --> 00:04:59.439 it's really a forensic investigation. 105 00:04:59.600 --> 00:05:02.399 It really is a cosmic crime scene. We have a 106 00:05:02.439 --> 00:05:05.560 ghost galaxy hiding in a very rough neighborhood called the 107 00:05:05.600 --> 00:05:09.439 Perseus Cluster, very rough. We have a team of detectives 108 00:05:09.560 --> 00:05:13.000 using three of the most powerful telescopes ever built. And 109 00:05:13.040 --> 00:05:16.240 they used a technique that I found absolutely brilliant in 110 00:05:16.279 --> 00:05:16.879 the source. 111 00:05:16.680 --> 00:05:17.879 Material, always so clever. 112 00:05:18.279 --> 00:05:20.759 They didn't look for the galaxy itself. They looked for 113 00:05:20.839 --> 00:05:24.360 the well, let's call them the ornaments. 114 00:05:23.920 --> 00:05:26.560 Globular clusters. They were hunting for globular clusters. 115 00:05:26.680 --> 00:05:29.199 So let's set the scene. We are going to the 116 00:05:29.240 --> 00:05:30.480 Perseus Cluster. 117 00:05:30.439 --> 00:05:33.199 Very chaotic noisy place in the universe. 118 00:05:33.399 --> 00:05:36.600 Let's start with the visual or I guess the lack thereof. 119 00:05:37.160 --> 00:05:40.959 The research comes from a collaboration evolving NASA, the European 120 00:05:41.000 --> 00:05:44.600 Space Agency, in the University of Toronto, and they released 121 00:05:44.639 --> 00:05:48.079 an image from the Hubble Space telescope. Now, usually when 122 00:05:48.120 --> 00:05:50.920 you see a Hubble press release, you expect fireworks, WAPs, 123 00:05:51.040 --> 00:05:56.040 you expect nebulas, pillars of creation giants, sweeping spiral arms. 124 00:05:56.120 --> 00:06:01.079 You expect high contrast, bright whites, deep blacks, vibrant colors 125 00:06:01.120 --> 00:06:02.439 all over the place, right. 126 00:06:02.360 --> 00:06:05.240 But I looked at the image for CDG two, specifically 127 00:06:05.319 --> 00:06:08.040 the crop they provided in the material, there is a 128 00:06:08.240 --> 00:06:11.560 dashed red circle drawn on the blackness of space, just 129 00:06:11.600 --> 00:06:13.240 to tell me where to look. And what did you 130 00:06:13.279 --> 00:06:16.480 see inside that circle? I literally had to wipe my monitor. 131 00:06:16.519 --> 00:06:18.199 I thought it was a smudge on my screen. 132 00:06:18.839 --> 00:06:21.639 It is incredibly underwhelming to the naked eye, isn't it. 133 00:06:21.639 --> 00:06:25.600 It looks like noise. It's just a faint, barely there haze. 134 00:06:25.839 --> 00:06:29.560 That is what astronomers classify as a low surface brightness galaxy. 135 00:06:29.839 --> 00:06:31.839 Low surface brightness the term. 136 00:06:31.680 --> 00:06:34.399 Is quite literal, the surface brightness meaning the amount of 137 00:06:34.480 --> 00:06:37.240 light emitting from any given square arc second of the 138 00:06:37.279 --> 00:06:40.680 sky is so low that it's barely distinguishable from the 139 00:06:40.680 --> 00:06:42.399 background radiation of the universe. 140 00:06:42.759 --> 00:06:45.480 So let's try to ground this for you listening. If 141 00:06:45.560 --> 00:06:48.560 I were in a spaceship floating just outside this galaxy 142 00:06:48.560 --> 00:06:51.480 looking out the window, what would I see? What I see? 143 00:06:51.480 --> 00:06:52.040 A galaxy? 144 00:06:52.079 --> 00:06:54.600 Honestly, you wouldn't see a structure. You wouldn't see a 145 00:06:54.639 --> 00:06:58.600 disk or spiral arms, or a glowing core, nothing like that. No, 146 00:06:59.040 --> 00:07:02.120 you would see a very sparse scattering of faint stars. 147 00:07:02.519 --> 00:07:04.920 It wouldn't look like a cohesive object. It would just 148 00:07:04.959 --> 00:07:07.959 look like you were in a slightly more populated region 149 00:07:08.000 --> 00:07:08.920 of empty space. 150 00:07:09.199 --> 00:07:11.759 It's a galaxy running on one percent battery. 151 00:07:11.879 --> 00:07:14.040 That's a good analogy to put a number on it. 152 00:07:14.399 --> 00:07:17.639 The paper notes that CDG two has a total luminosity 153 00:07:17.879 --> 00:07:21.639 equivalent to roughly six million sun like stars. 154 00:07:21.879 --> 00:07:26.399 Okay, stop there, six million sons. To me and probably 155 00:07:26.439 --> 00:07:29.240 to you listening, six million suns sounds like a blinding 156 00:07:29.240 --> 00:07:30.879 amount of light. That sounds huge. 157 00:07:31.160 --> 00:07:34.120 It sounds massive in human terms. Yes, but we have 158 00:07:34.199 --> 00:07:36.120 to adjust our scale to galactic terms. 159 00:07:36.160 --> 00:07:37.279 Okay, adjusted for me. 160 00:07:37.279 --> 00:07:40.040 For context, the Milky Way contains somewhere between one hundred 161 00:07:40.040 --> 00:07:42.040 and four hundred billion stars. 162 00:07:41.639 --> 00:07:43.800 Wow, one hundred to four hundred billion. 163 00:07:43.879 --> 00:07:46.399 To do the math there, six million versus four hundred 164 00:07:46.439 --> 00:07:49.680 billion CDG two is putting out less than zero point 165 00:07:49.839 --> 00:07:52.120 zero one percent of the light of the Milky Way. 166 00:07:52.160 --> 00:07:52.839 That is nothing. 167 00:07:52.959 --> 00:07:54.720 It is a whisper compared to a shout. 168 00:07:54.759 --> 00:07:56.879 And it's not just that it's faint, it's where it is. 169 00:07:57.199 --> 00:08:00.399 We are looking at an object inside the Percus galaxy cluster. 170 00:08:00.720 --> 00:08:01.759 How far away is this? 171 00:08:02.160 --> 00:08:04.600 We are looking at a distance of roughly three hundred 172 00:08:04.639 --> 00:08:05.439 million light years. 173 00:08:05.560 --> 00:08:07.879 Three hundred million light years. I want to pause on 174 00:08:07.920 --> 00:08:10.319 that number because I think we get really numb to 175 00:08:10.920 --> 00:08:12.680 millions and billions in space talk. 176 00:08:12.800 --> 00:08:14.680 It's hard for the human brain to process. 177 00:08:14.879 --> 00:08:17.920 Right. The light we are seeing from this faint smudge 178 00:08:18.079 --> 00:08:22.839 left the galaxy three hundred million years ago. That's the Palaeozoic. 179 00:08:22.240 --> 00:08:26.160 Era on Earth, long before the dinosaurs. We are talking 180 00:08:26.240 --> 00:08:29.639 about the time when the first reptiles were just emerging 181 00:08:29.680 --> 00:08:32.720 on Earth. The continents were in completely different positions. 182 00:08:32.759 --> 00:08:35.519 So we are trying to spot a faint collection of 183 00:08:35.600 --> 00:08:39.120 six million stars, which is basically nothing, from a distance 184 00:08:39.159 --> 00:08:42.559 that is incomprehensibly far away. It's like trying to see 185 00:08:42.559 --> 00:08:44.759 a candle in the moon, but the candle is behind 186 00:08:44.759 --> 00:08:47.120 a giant searchlight, the searchlight being. 187 00:08:46.960 --> 00:08:49.000 The rest of the Perseus cluster. You have to understand, 188 00:08:49.039 --> 00:08:51.919 Perseus is one of the most massive objects in the 189 00:08:52.080 --> 00:08:56.519 entire known universe. Really, Oh yeah, it contains thousands of galaxies. 190 00:08:56.960 --> 00:09:00.240 It is full of hot X ray emitting gas. It 191 00:09:00.320 --> 00:09:03.840 is bright, it is crowded, and it is gravitationally noisy. 192 00:09:03.960 --> 00:09:07.120 Finding CDG two in there is statistically nightmarish. 193 00:09:07.320 --> 00:09:10.039 And that leads me to the how if you can't 194 00:09:10.080 --> 00:09:12.879 just stand the sky and see it, Because as we establish, 195 00:09:12.960 --> 00:09:14.639 it looks like nothing, how do you find it? You 196 00:09:14.679 --> 00:09:17.159 can't just zoo in on every single pixel of the sky. 197 00:09:17.279 --> 00:09:20.600 Now you would never finish. Yeah, the universe is too big. 198 00:09:20.919 --> 00:09:23.480 You need a marker, you need a proxy. 199 00:09:23.919 --> 00:09:27.120 Entered David Lai. He's the lead researcher from the University 200 00:09:27.159 --> 00:09:30.279 of Toronto on this project. Yes, and his team didn't 201 00:09:30.360 --> 00:09:32.879 start by looking for the galaxy itself. They started by 202 00:09:32.960 --> 00:09:34.919 hunting for those ornaments we mentioned earlier. 203 00:09:35.000 --> 00:09:36.960 They went looking for globular clusters. 204 00:09:37.000 --> 00:09:40.240 Okay, let's unpack globular clusters because to me, it sounds 205 00:09:40.279 --> 00:09:43.159 like a type of candy or maybe a geology term. 206 00:09:43.519 --> 00:09:47.759 What exactly is a globular cluster In this astronomical context, 207 00:09:48.240 --> 00:09:48.600 it is. 208 00:09:48.559 --> 00:09:52.039 One of the most ancient and fundamental structures in the cosmos. 209 00:09:52.559 --> 00:09:58.320 A globular cluster is a very compact, spherical group of stars. Spherical, right, 210 00:09:58.639 --> 00:10:01.840 Imagine a ball maybe ten to thirty light years across, 211 00:10:01.919 --> 00:10:05.679 but packed with tens of thousands, sometimes even millions of stars. 212 00:10:05.720 --> 00:10:07.559 So it's a super dense city of stars. 213 00:10:07.639 --> 00:10:10.879 Extremely dense. In the solar neighborhood where we are, stars 214 00:10:10.919 --> 00:10:13.639 are light years apart in the core of a globular cluster. 215 00:10:14.120 --> 00:10:17.879 They are packed cheek by jowl, and the key characteristic 216 00:10:17.960 --> 00:10:21.000 for this study is that globular clusters are typically found 217 00:10:21.279 --> 00:10:22.360 orbiting normal. 218 00:10:22.080 --> 00:10:26.159 Galaxies, orbiting them like moons around a planet. 219 00:10:26.120 --> 00:10:28.440 Kind of The Milky Way has about one hundred and 220 00:10:28.440 --> 00:10:31.679 fifty of them. They swarm around the galacticiclo like bees 221 00:10:31.679 --> 00:10:32.320 around a hive. 222 00:10:32.399 --> 00:10:33.799 Okay, so the clusters are the bees. 223 00:10:33.840 --> 00:10:36.799 The galaxy is the high right now, imagine you are 224 00:10:36.799 --> 00:10:39.159 looking at a hive at night from a mile away. 225 00:10:39.159 --> 00:10:39.919 It's pitch black. 226 00:10:40.360 --> 00:10:42.840 You can't see the hive itself. It blends completely into 227 00:10:42.840 --> 00:10:47.240 the darkness of the trees. But suppose the bees are bioluminescent. 228 00:10:47.759 --> 00:10:48.679 Suppose they glow. 229 00:10:49.279 --> 00:10:53.399 Ah, if I see a swarm of glowing bees hovering 230 00:10:53.440 --> 00:10:56.799 in a specific tight formation, I can safely assume the 231 00:10:56.879 --> 00:10:58.600 hive is sitting right in the middle of them. 232 00:10:58.720 --> 00:11:01.279 That is precisely the logic. This is the big breakthrough. 233 00:11:01.440 --> 00:11:04.799 CDG two is the first galaxy detected solely through its 234 00:11:04.799 --> 00:11:06.240 globular cluster population. 235 00:11:06.480 --> 00:11:08.200 I want to make sure I really get the difficulty 236 00:11:08.240 --> 00:11:10.679 of this though. At three hundred million light years away, 237 00:11:10.879 --> 00:11:13.519 does a globular cluster look like a ball of stars 238 00:11:13.519 --> 00:11:14.440 in a telescope? 239 00:11:14.720 --> 00:11:19.720 No, even with hubble at that immense distance, a globular 240 00:11:19.879 --> 00:11:23.000 cluster is what we call a point source, meaning it 241 00:11:23.039 --> 00:11:26.559 looks like a single pixel, looks exactly like a single 242 00:11:26.679 --> 00:11:29.480 faint star in our own milky way that just happens 243 00:11:29.519 --> 00:11:31.519 to be in the foreground. Yeah. Or it looks like 244 00:11:31.559 --> 00:11:33.519 a very distant background galaxy. 245 00:11:33.639 --> 00:11:36.879 So you have a field of view full of thousands 246 00:11:36.879 --> 00:11:40.960 of tiny dots. Some are foreground stars, some are background galaxies, 247 00:11:41.000 --> 00:11:44.960 and a very small few are these globular clusters exactly? 248 00:11:45.039 --> 00:11:46.120 How do you know which a witch? 249 00:11:46.480 --> 00:11:48.600 That is the real trick of this whole endeavor. You 250 00:11:48.600 --> 00:11:50.360 can't just look at the dots individually. You have to 251 00:11:50.360 --> 00:11:53.320 look at the statistics of the dots. Statistics explain that 252 00:11:53.519 --> 00:11:56.440 this is where David Lye's work is so incredibly impressive. 253 00:11:57.200 --> 00:12:01.120 They used a sophisticated algorithm to scan the overall distribution 254 00:12:01.200 --> 00:12:04.840 of these points of light. Okay, random noise, meaning your 255 00:12:04.840 --> 00:12:08.759 foreground stars and your background galaxies, tends to be distributed 256 00:12:08.799 --> 00:12:11.919 somewhat uniformly across the sky, or at least randomly scattered. 257 00:12:11.960 --> 00:12:13.440 This is a general spread. 258 00:12:13.360 --> 00:12:16.639 Right, But globular clusters that belong to a single galaxy 259 00:12:17.080 --> 00:12:20.240 aren't random at all. They're gravitationally bound to each other 260 00:12:20.279 --> 00:12:22.759 and to the host galaxy. They cluster together. 261 00:12:22.960 --> 00:12:26.240 So they were specifically looking for a tight grouping of dots. 262 00:12:26.399 --> 00:12:30.120 Exactly, they were looking for a statistical anomaly. The algorithm 263 00:12:30.200 --> 00:12:33.879 essentially asks, is there a region in this patch of 264 00:12:33.879 --> 00:12:37.159 sky where I see three or four of these specific 265 00:12:37.240 --> 00:12:40.360 point sources huddled together in a way that is highly 266 00:12:40.440 --> 00:12:42.519 unlikely to happen just by random chance. 267 00:12:42.799 --> 00:12:45.440 I see. It's like walking into a crowded sports stadium. 268 00:12:45.480 --> 00:12:47.720 You can't tell who knows who just by looking at 269 00:12:47.720 --> 00:12:49.080 the giant sea of faces. 270 00:12:49.279 --> 00:12:49.960 No, you can't. 271 00:12:50.080 --> 00:12:52.279 But if you see four people standing in a tight 272 00:12:52.320 --> 00:12:56.360 little circle facing each other, ignoring everyone else, you assume 273 00:12:56.600 --> 00:12:58.519 they are a group. They came together. 274 00:12:58.639 --> 00:13:01.759 That's a perfect analogy. The algorithm flagged these friends. It said, Hey, 275 00:13:02.279 --> 00:13:05.799 at these specific coordinates, there are four objects that seem 276 00:13:05.840 --> 00:13:06.960 to be hanging out together. 277 00:13:07.279 --> 00:13:09.759 And because gravity works the way it does, yes. 278 00:13:10.039 --> 00:13:12.600 If you have four massive star clusters hanging out in 279 00:13:12.679 --> 00:13:14.960 the tight group, there must be something massive in the 280 00:13:15.000 --> 00:13:16.080 middle holding them there. 281 00:13:16.320 --> 00:13:19.919 And that unseen massive something is the dark matter halo 282 00:13:20.039 --> 00:13:21.000 of CDG two. 283 00:13:21.399 --> 00:13:26.639 Correct Using this method, they identified ten previously confirmed low 284 00:13:26.679 --> 00:13:27.960 surface brightness. 285 00:13:27.519 --> 00:13:30.440 Galaxies, which prove the math works exactly. 286 00:13:30.480 --> 00:13:34.279 It validated the tool, and then using that validated tool, 287 00:13:34.360 --> 00:13:37.120 they found two new candidates. CGG two was one of them. 288 00:13:37.159 --> 00:13:39.399 I love that so much. They didn't see the galaxy, 289 00:13:39.519 --> 00:13:42.639 they calculated that it absolutely must be there. It's a 290 00:13:42.679 --> 00:13:45.519 triumph of math as much as it is observation. 291 00:13:45.440 --> 00:13:48.360 Which is really where modern astronomy is heading. As a field. 292 00:13:48.840 --> 00:13:51.879 We are rapidly moving from point and shoot astronomy to 293 00:13:52.279 --> 00:13:53.320 massive data mining. 294 00:13:53.720 --> 00:13:56.919 But as with any good detective investigation, just having a 295 00:13:56.960 --> 00:13:59.759 suspect isn't enough. You can't publish a paper saying the 296 00:14:00.000 --> 00:14:01.360 math says there's a galaxy here. 297 00:14:01.519 --> 00:14:04.159 Trust us, you definitely cannot. You need to verify it 298 00:14:04.200 --> 00:14:07.279 and see the body to keep the crime scene metaphor going. 299 00:14:07.159 --> 00:14:10.480 And that requires the heavy artillery. It does verification triad. 300 00:14:10.559 --> 00:14:12.200 I really like the sound of that from the research. 301 00:14:12.559 --> 00:14:15.200 It does sound official, doesn't it. It refers to the 302 00:14:15.279 --> 00:14:19.639 three major observatories they used in tandem to confirm this candidate, 303 00:14:20.159 --> 00:14:23.639 because no single telescope on Earth or in space could 304 00:14:23.639 --> 00:14:24.480 do the whole job. 305 00:14:24.720 --> 00:14:27.240 Let's break down why that is. Why did they need 306 00:14:27.320 --> 00:14:30.000 three different telescopes. Let's start with the most famous one 307 00:14:30.039 --> 00:14:32.879 of the bunch, NASA's Hubble Space telescope. 308 00:14:32.960 --> 00:14:34.519 Hubble is the sniper of the group. 309 00:14:34.639 --> 00:14:35.200 The sniper. 310 00:14:35.440 --> 00:14:39.799 Yes, it has incredible pinpoint resolution. They needed Hubble to 311 00:14:39.840 --> 00:14:44.039 confirm that those four suspicious dots were actually globular clusters 312 00:14:44.320 --> 00:14:46.200 and not just something else masquerading A Is that? 313 00:14:46.399 --> 00:14:48.320 So Hubble gives you the fine detail. 314 00:14:48.679 --> 00:14:52.360 Hubble provided the sharpness to resolve the immediate local environment 315 00:14:52.399 --> 00:14:53.279 of those four points. 316 00:14:53.360 --> 00:14:56.159 Okay, so Hubble confirms the ornaments are real. Who is 317 00:14:56.240 --> 00:14:57.120 next in the triad? 318 00:14:57.559 --> 00:15:02.039 Next is ESA's EUCLID Space Observati Tory, the European Space Agency. 319 00:15:02.519 --> 00:15:04.840 This is a newer mission and it's critical for a 320 00:15:04.879 --> 00:15:08.240 totally different reason. Hubble has a very, very narrow field 321 00:15:08.279 --> 00:15:10.399 of view. It basically looks at a tiny straw hole 322 00:15:10.440 --> 00:15:13.200 of the sky at any given moment. EUCLID, on the 323 00:15:13.200 --> 00:15:17.000 other hand, is wide angle. It surveys huge swaths of 324 00:15:17.039 --> 00:15:18.120 the cosmos all at once. 325 00:15:18.320 --> 00:15:20.360 But why do you need a wide angle to see 326 00:15:20.360 --> 00:15:22.000 a tiny, faint galaxy. 327 00:15:22.639 --> 00:15:25.279 You need context. You need to know that this tight 328 00:15:25.320 --> 00:15:28.879 grouping of four clusters is truly isolated in space. Oh, 329 00:15:28.960 --> 00:15:31.320 I see, you need to see the surrounding neighborhood to 330 00:15:31.399 --> 00:15:34.720 ensure these clusters aren't just the far outskirts of some other, 331 00:15:35.080 --> 00:15:38.559 much bigger galaxy nearby. EUCLID confirms the isolation. 332 00:15:38.799 --> 00:15:42.000 Got it. Hubble zooms in to check the details. EUCLID 333 00:15:42.080 --> 00:15:45.639 zooms out to check the neighborhood. And the third telescope. 334 00:15:45.080 --> 00:15:48.480 The Subreu telescope. This is a ground based monster located 335 00:15:48.519 --> 00:15:50.120 on Monachia in Hawaii. 336 00:15:50.279 --> 00:15:52.320 Now, why do we need a ground telescope if we 337 00:15:52.360 --> 00:15:56.240 already have two amazing space telescopes. Usually we think space 338 00:15:56.320 --> 00:15:59.360 is better because there's no atmosphere to distort the image. 339 00:15:59.399 --> 00:16:02.679 Space gives you clarity. Yes, the ground gives you size. 340 00:16:02.720 --> 00:16:04.480 You can build much bigger things on the ground. 341 00:16:04.679 --> 00:16:06.320 Size matters here very much. 342 00:16:06.399 --> 00:16:09.279 The Subaru telescope has a primary mirror that is over 343 00:16:09.320 --> 00:16:13.159 eight meters wide. Hubble's mirror is only two point four meters. 344 00:16:13.279 --> 00:16:14.480 That's a huge difference. 345 00:16:14.559 --> 00:16:16.720 It is. Think of it like catching rain. A bigger 346 00:16:16.720 --> 00:16:19.799 bucket catches more rain. In this case, the rain is 347 00:16:19.879 --> 00:16:21.120 light photons. 348 00:16:20.840 --> 00:16:23.960 So Subro is essentially a giant light bucket exactly. 349 00:16:24.120 --> 00:16:28.320 They needed Subru's immense light gathering power to try and 350 00:16:28.360 --> 00:16:32.399 detect the incredibly faint glow between those clusters the actual 351 00:16:32.440 --> 00:16:33.399 galaxy itself. 352 00:16:33.559 --> 00:16:35.759 And this is the real moment of truth in the story. 353 00:16:36.320 --> 00:16:39.440 They combine the data from the sniper, the wide angle, 354 00:16:39.600 --> 00:16:42.240 and the light bucket. What did they actually find. 355 00:16:42.559 --> 00:16:45.759 They found the ghost when they process the deep imaging, 356 00:16:45.919 --> 00:16:49.840 specifically looking at the empty space between those four colobular clusters. 357 00:16:50.000 --> 00:16:53.039 Yeah, they detected a signal, a signal like a radio 358 00:16:53.080 --> 00:16:53.639 sign row. 359 00:16:53.519 --> 00:16:58.159 An optical signal, a faint, diffuse structural glow. It wasn't 360 00:16:58.200 --> 00:17:02.559 just empty black space, was a very very weak stellar 361 00:17:02.639 --> 00:17:04.480 population surrounding those clusters. 362 00:17:04.519 --> 00:17:05.920 That is the body of the galaxy. 363 00:17:05.960 --> 00:17:08.759 That is the body. It confirmed once and for all 364 00:17:08.920 --> 00:17:11.680 the clusters weren't just randomly floating in the void. They 365 00:17:11.680 --> 00:17:14.599 were embedded in a dark matter halo. They were anchoring 366 00:17:14.680 --> 00:17:16.279 a hidden stellar population. 367 00:17:16.759 --> 00:17:19.519 So the Christmas tree analogy holds up perfectly. They saw 368 00:17:19.559 --> 00:17:21.960 the glowing ornaments, they did the math to prove they 369 00:17:21.960 --> 00:17:24.279 were a group, and when they turned up the exposure 370 00:17:24.319 --> 00:17:27.119 time with the big telescope, they finally saw the faint 371 00:17:27.160 --> 00:17:29.440 outline of the trees branches precisely. 372 00:17:29.799 --> 00:17:33.279 And David Lay makes a very conservative, but very interesting 373 00:17:33.319 --> 00:17:34.279 point here in the findings. 374 00:17:34.359 --> 00:17:34.680 What's that? 375 00:17:35.119 --> 00:17:37.880 He notes they given the mass calculations of the halo, 376 00:17:38.559 --> 00:17:43.200 these four clusters likely represent the entire globular cluster population 377 00:17:43.319 --> 00:17:44.200 of CDG two. 378 00:17:44.279 --> 00:17:46.279 Wait only four? You just said our Milky Way has 379 00:17:46.279 --> 00:17:47.000 one hundred and fifty. 380 00:17:47.240 --> 00:17:51.359 Yes, CDG two is hanging onto these four clusters for 381 00:17:51.440 --> 00:17:55.079 dear life. They're the only major structural features it has left. 382 00:17:55.400 --> 00:17:57.839 That brings us to the why. This is the part 383 00:17:57.880 --> 00:17:59.759 of the exploration that really hooked me. We have a 384 00:17:59.759 --> 00:18:03.079 gaps galaxy that is ninety nine percent dark matter, has 385 00:18:03.160 --> 00:18:06.160 almost no stars and only four Measley clusters. 386 00:18:06.279 --> 00:18:07.240 It's a barren place. 387 00:18:07.559 --> 00:18:10.079 Why is it so empty? Did it form this way 388 00:18:10.160 --> 00:18:12.359 right after the Big Bang? Or does something terrible happen 389 00:18:12.400 --> 00:18:12.680 to it? 390 00:18:13.200 --> 00:18:16.079 Now we are moving from detection to forensics. We're looking 391 00:18:16.119 --> 00:18:19.440 at the cause of death, or perhaps more accurately, the 392 00:18:19.440 --> 00:18:20.480 cause of sterility. 393 00:18:20.559 --> 00:18:22.640 Sterility, that's a strong word for a galaxy. 394 00:18:22.799 --> 00:18:26.319 Well, a galaxy lives in astronomical terms, as long as 395 00:18:26.359 --> 00:18:29.240 it forms new stars. Ok, deform stars. You need fuel, 396 00:18:29.599 --> 00:18:32.440 and the fuel of the universe is hydrogen gas, cold, 397 00:18:32.599 --> 00:18:33.720 dense hydrogen gas. 398 00:18:34.000 --> 00:18:36.400 And the research says CDG two has none. 399 00:18:36.240 --> 00:18:38.920 Of this gas. It is completely depleted. It is what 400 00:18:38.960 --> 00:18:41.920 we call gas poor. This means it stopped forming stars 401 00:18:41.920 --> 00:18:44.240