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 --> 00:00:29.120 So I want you to just picture looking back to 8 00:00:29.199 --> 00:00:32.520 a time when the universe was well essentially an infant, 9 00:00:32.679 --> 00:00:34.600 like less than a billion years old. 10 00:00:34.399 --> 00:00:36.000 Right right, A very different place than it. 11 00:00:35.960 --> 00:00:39.439 Is today, completely different. The cosmic web is just unbelievably 12 00:00:39.479 --> 00:00:43.200 dense and volatile, and at that incredible distance, specifically at 13 00:00:43.200 --> 00:00:45.640 a redshift of five point seven, we are witnessing this 14 00:00:45.799 --> 00:00:49.759 literal cosmic dance between two of the brightest, most violent 15 00:00:49.799 --> 00:00:50.960 objects and existence. 16 00:00:51.439 --> 00:00:54.000 It really is staggering. We are talking about the system 17 00:00:54.079 --> 00:00:56.920 J twenty three seven four five three seven, which is 18 00:00:56.960 --> 00:00:59.719 a confirmed spatially resolved dual quasar. 19 00:01:00.079 --> 00:01:02.640 Yeah, and that's the whole mission today to unpack what 20 00:01:02.719 --> 00:01:06.799 these colossal engines actually are and how astronomers even prove 21 00:01:06.879 --> 00:01:09.200 they weren't just some cosmic optical illusion, which is a 22 00:01:09.280 --> 00:01:10.519 huge part of this story. 23 00:01:10.599 --> 00:01:13.920 Oh, absolutely, Proving what is actually real in the universe 24 00:01:13.920 --> 00:01:18.359 that is just full of mirages is half the battle. 25 00:01:18.120 --> 00:01:20.840 Exactly because when we talk about peering that far back, 26 00:01:21.079 --> 00:01:23.560 it's not just distant trivia. It's a full on detective 27 00:01:23.599 --> 00:01:26.359 story for you, the listener, about the invisible fabric of 28 00:01:26.359 --> 00:01:28.959 the universe itself. But I just keep getting stuck on 29 00:01:29.000 --> 00:01:30.400 the awe of the sheer distance. 30 00:01:30.799 --> 00:01:33.879 I mean, you have to the improbability hears off the charts. 31 00:01:34.840 --> 00:01:37.680 When we look at quasars at a red shift greater 32 00:01:37.760 --> 00:01:41.599 than five, we are already looking at the rarest most 33 00:01:41.640 --> 00:01:43.760 extreme objects in the early universe. 34 00:01:43.959 --> 00:01:45.599 Just finding one is a big deal exactly. 35 00:01:45.640 --> 00:01:48.680 So finding two of them, separated by just a few 36 00:01:48.760 --> 00:01:54.799 kiloparsex locked in this violent gravitational spiral, it's basically absurd, 37 00:01:55.040 --> 00:01:57.120 it really is. I mean, this is literally one of 38 00:01:57.239 --> 00:02:00.480 only two confirmed quasar pairs we have ever found at 39 00:02:00.480 --> 00:02:04.359 a red shift that high. It forces us to completely 40 00:02:04.359 --> 00:02:07.879 reevaluate our models of how fast these super massive black 41 00:02:07.920 --> 00:02:10.240 holes were growing during the cosmic dawn. 42 00:02:10.759 --> 00:02:14.520 But there's a paradox here, right, because the whole hierarchical 43 00:02:14.560 --> 00:02:17.919 model of cosmology, the idea of how structures assemble. It 44 00:02:17.960 --> 00:02:20.639 basically says galaxy should be slamming together all the time 45 00:02:20.680 --> 00:02:21.479 in the early universe. 46 00:02:21.479 --> 00:02:24.439 That's right. The early universe was crowded, mergers were common. 47 00:02:24.240 --> 00:02:26.520 Right, So if galaxy mergers are happening all the time, 48 00:02:26.759 --> 00:02:30.599 why is finding two blazing quasars in a single system 49 00:02:30.719 --> 00:02:33.919 so extraordinarily rare? I mean, shouldn't the sky be lit 50 00:02:34.000 --> 00:02:34.759 up with these things? 51 00:02:34.960 --> 00:02:38.520 Well, it comes down to a really brutal timing problem. 52 00:02:38.680 --> 00:02:43.879 A galaxy merger is a slow, agonizing process. We're talking 53 00:02:44.280 --> 00:02:48.759 hundreds of millions, sometimes over a billion years to actually complete. 54 00:02:48.360 --> 00:02:50.719 Which is a massive amount of time, even on a 55 00:02:50.759 --> 00:02:52.240 cosmic scale exactly. 56 00:02:53.000 --> 00:02:55.759 But the active quasar phase, the part where the black 57 00:02:55.800 --> 00:02:59.240 hole is actually eating and glowing, that is highly transient. 58 00:02:59.280 --> 00:03:00.479 It doesn't last long at all. 59 00:03:00.599 --> 00:03:03.840 No, the supermassive black hole only it creates matter fast 60 00:03:03.960 --> 00:03:07.120 enough to outshine the whole galaxy for a tiny fraction 61 00:03:07.199 --> 00:03:09.560 of that merger timescale. The duty cycle might only be 62 00:03:09.560 --> 00:03:11.680 a few million, maybe tens of millions of years. 63 00:03:11.759 --> 00:03:15.800 So it's kind of like having a spectacularly lazy, picky 64 00:03:15.840 --> 00:03:18.439 eater of a black hole, right. It just sits there, 65 00:03:18.520 --> 00:03:22.400 dormant until a galactic collision forcefully shoves this cosmic buffet 66 00:03:22.520 --> 00:03:23.360 right into its mouth. 67 00:03:23.560 --> 00:03:25.479 That is a very visceral way to put it, but yeah, 68 00:03:25.520 --> 00:03:28.599 it's accurate. In a normal stable disc galaxy, the gas 69 00:03:28.680 --> 00:03:30.960 is just orbiting smoothly. It's supported by its own rotation. 70 00:03:31.039 --> 00:03:32.560 You're not just falling in right. 71 00:03:32.599 --> 00:03:37.080 It will stay in orbit practically forever unless something violently 72 00:03:37.120 --> 00:03:40.000 extracts that rotational energy. And that's what the major merger does. 73 00:03:40.199 --> 00:03:44.120 It provides these extreme gravitational torques. It disrupts everything exactly. 74 00:03:44.159 --> 00:03:48.319 It creates these massive shocks, funnels unimaginable amounts of gas 75 00:03:48.400 --> 00:03:51.319 straight down into the nucleus. But the accretion isn't smooth. 76 00:03:51.759 --> 00:03:55.039 The gas piles up, the quasar ignites, and then the 77 00:03:55.159 --> 00:03:58.840 radiation pressure from the quasar itself creates these massive outflows. 78 00:03:58.919 --> 00:04:01.960 Oh right, the feedback. It basically blows its own food 79 00:04:02.000 --> 00:04:02.599 source away. 80 00:04:02.639 --> 00:04:05.639 Precisely, it chokes off its own shiel. It suffocates itself. 81 00:04:06.080 --> 00:04:08.639 So to catch j two to three seven four or 82 00:04:08.680 --> 00:04:12.680 five three seven with both super massive black holes actively 83 00:04:12.719 --> 00:04:15.439 lit up at the exact same moment from our perspective 84 00:04:15.599 --> 00:04:18.639 twelve point eight billion light years away, it's wise. It's 85 00:04:18.680 --> 00:04:22.040 like catching two separate lightning strikes in the exact same photograph. 86 00:04:21.560 --> 00:04:24.759 And because it's that incredibly rare, the initial reaction from 87 00:04:24.759 --> 00:04:27.560 the scientific community wasn't just you know, popping champagne. It 88 00:04:27.600 --> 00:04:30.120 was profound skepticism. People thought it was a trick. 89 00:04:30.480 --> 00:04:33.920 Oh. The scrutiny was intense because when this was first 90 00:04:33.959 --> 00:04:37.160 reported as a candidate back in twenty twenty one, observers 91 00:04:37.240 --> 00:04:41.759 just saw two identical, incredibly bright dots separated by a 92 00:04:41.800 --> 00:04:44.639 tiny fraction of an arcsecond. And when you see that 93 00:04:44.680 --> 00:04:48.519 at redshift five point seven, the default assumption in astronomy 94 00:04:48.600 --> 00:04:52.120 is absolutely not a binary quasar. The default assumption is 95 00:04:52.120 --> 00:04:55.480 an optical illusion caused by strong gravitational. 96 00:04:54.920 --> 00:04:58.279 Lensing, which we really have to unpack because gravitational lensing 97 00:04:58.360 --> 00:05:02.240 is such a common imposter in deep space observations. It 98 00:05:02.319 --> 00:05:05.360 forces astronomers to second guess their own eyes constantly. 99 00:05:05.519 --> 00:05:08.720 It really does. General relativity tells us that massive four 100 00:05:08.759 --> 00:05:12.480 ground objects like a galaxy cluster literally warp the space 101 00:05:12.519 --> 00:05:13.199 time around them. 102 00:05:13.279 --> 00:05:16.519 Right. It acts quite literally like a massive invisible glass 103 00:05:16.600 --> 00:05:17.319 LEDs exactly. 104 00:05:17.399 --> 00:05:19.959 So if you have a single solitary quasar way in 105 00:05:20.000 --> 00:05:22.199 the background, its light passes through that warped space, time 106 00:05:22.240 --> 00:05:25.720 gets bent, and that geometry can easily produce two or 107 00:05:25.759 --> 00:05:28.480 even four separate images of the exact same quasar. 108 00:05:28.720 --> 00:05:31.079 I always think of it like looking through a distorted 109 00:05:31.160 --> 00:05:34.480 funhouse mirror, or like the curved bottom of a wineglass. 110 00:05:35.199 --> 00:05:38.199 You hold up one candle, but through the glass it 111 00:05:38.240 --> 00:05:39.800 looks like two distinct flames. 112 00:05:40.000 --> 00:05:43.319 That's a perfect analogy. And because it's just a mirage 113 00:05:43.439 --> 00:05:46.639 of the same object, the light from those two dots 114 00:05:46.720 --> 00:05:47.759 will look identical. 115 00:05:47.959 --> 00:05:48.120 Right. 116 00:05:48.199 --> 00:05:50.319 Their spectrum match perfectly. 117 00:05:49.959 --> 00:05:53.519 Exactly, their red shifts, their colors, everything matches, and the 118 00:05:53.639 --> 00:05:57.399 degeneracy there the difficulty in telling them apart is just 119 00:05:57.920 --> 00:05:59.319 notoriously hard to break. 120 00:05:59.519 --> 00:06:01.319 But wait, I want to push back on that a bit. 121 00:06:01.439 --> 00:06:04.079 If you're looking at two identical dots of light from 122 00:06:04.160 --> 00:06:07.920 billions of light years away, and a literal cosmic funhouse 123 00:06:08.000 --> 00:06:10.959 mirror can perfectly fake that image, how can you possibly 124 00:06:11.000 --> 00:06:12.519 prove what you're looking at is real? 125 00:06:12.680 --> 00:06:16.279 Well, in traditional optical astronomy, it's incredibly difficult because the 126 00:06:16.319 --> 00:06:19.680 deflector galaxy, the lens itself might be completely hidden by 127 00:06:19.680 --> 00:06:21.360 the blinding glare of the quasars. 128 00:06:21.439 --> 00:06:22.319 It's buried in the light. 129 00:06:22.600 --> 00:06:24.439 Right, So you look at the optical data. You see 130 00:06:24.480 --> 00:06:29.319 two bright dots. You extract the spectra and their twins photometrically, 131 00:06:29.600 --> 00:06:33.000 a lens system and a real binary look exactly the same. 132 00:06:33.199 --> 00:06:35.279 So if you can't see the lens, you can't map 133 00:06:35.319 --> 00:06:37.360 the distortion. It sounds like a total dead end. 134 00:06:37.600 --> 00:06:39.560 It is a dead end if you only look at 135 00:06:39.560 --> 00:06:43.879 the point sources. The rigorous burden of proof here requires 136 00:06:43.920 --> 00:06:46.519 you to look away from the bright lights. You have 137 00:06:46.560 --> 00:06:49.639 to look at the dark space between the quasars for 138 00:06:49.839 --> 00:06:53.120 physical interactions that a mirage couldn't possibly fake. 139 00:06:53.360 --> 00:06:56.319 You have to find the physical wreckage of the collision precisely. 140 00:06:56.800 --> 00:07:00.360 A gravitational lens will distort the background host galaxy into 141 00:07:00.360 --> 00:07:04.360 smooth arcs or a ring, but it will never create localized, 142 00:07:04.439 --> 00:07:09.079 chaotic asymmetric wreckage between two independent gravity wells. 143 00:07:08.920 --> 00:07:13.040 Because a mirage doesn't leave muddy footprints connecting two houses exactly. 144 00:07:13.319 --> 00:07:15.639 But to see those footprints you have to completely bypass 145 00:07:15.759 --> 00:07:18.560 the brilliant optical light of the quasars. You have to 146 00:07:18.600 --> 00:07:21.680 move to the far infrared and submillimeter wavelengths to see 147 00:07:21.680 --> 00:07:22.360 the cold. 148 00:07:22.120 --> 00:07:25.040 Gas, which brings us right to the smoking gun. This 149 00:07:25.120 --> 00:07:28.639 is where the team led by minghow YU brings in ALELMA. 150 00:07:28.920 --> 00:07:32.120 The Atacoma Large Millimeter Submillimeter Array. 151 00:07:32.199 --> 00:07:35.319 Right, ALMA is the perfect tool for this. It's spatial 152 00:07:35.360 --> 00:07:38.920 resolution at submillimeter wavelengths is just unpreced in it. They 153 00:07:38.920 --> 00:07:41.199 weren't looking at the black holes at all. They were 154 00:07:41.240 --> 00:07:45.240 mapping the cold, neutral gas of the host galaxies. 155 00:07:44.879 --> 00:07:49.160 And specifically, they were mapping the emission lines of ionized carbon, 156 00:07:49.319 --> 00:07:52.319 which is noted as C two. I really want to 157 00:07:52.319 --> 00:07:56.160 dig into this because why map ionized carbon specifically? What 158 00:07:56.279 --> 00:08:00.160 makes this exact element the perfect cosmic fingerprint here? 159 00:08:00.720 --> 00:08:03.879 It really is a phenomenal diagnostic tool. It's tied directly 160 00:08:03.959 --> 00:08:07.800 to how galaxies form stars. See in a galaxy, gas 161 00:08:07.800 --> 00:08:10.160 has to cool down before it can collapse under gravity 162 00:08:10.319 --> 00:08:11.000 to form a star. 163 00:08:11.120 --> 00:08:13.240 Right if it's too hot, it just expands. 164 00:08:12.879 --> 00:08:16.480 Exactly And when young massive stars are born, they blast 165 00:08:16.519 --> 00:08:19.720 the surrounding area with ultraviolet radiation. That UV light hits 166 00:08:19.800 --> 00:08:22.800 dust grains, ejects electrons, and those electrons bounce around and 167 00:08:22.839 --> 00:08:23.639 heat up the gas. 168 00:08:23.839 --> 00:08:26.160 So the star formation is heating the gas, which should 169 00:08:26.240 --> 00:08:28.839 stop more stars from forming. It needs a release valve. 170 00:08:29.199 --> 00:08:32.799 It absolutely needs a release valve to radiate that energy away, 171 00:08:33.039 --> 00:08:35.240 and carbon is perfect for this because it has a 172 00:08:35.360 --> 00:08:39.320 very low ionization potential. Even in cold clouds, carbon gets 173 00:08:39.399 --> 00:08:43.000 ionized easily by starlight, So those bouncing electrons hit the 174 00:08:43.039 --> 00:08:46.399 ionized carbon atoms, exciting them. When the carbon atom drops 175 00:08:46.440 --> 00:08:49.279 back down to its normal state, it releases a photon 176 00:08:49.399 --> 00:08:52.279 at a very specific wavelength one hundred and fifty eight 177 00:08:52.399 --> 00:08:53.519 micrometers ah. 178 00:08:53.639 --> 00:08:58.080 So that specific flash of light is the cooling process happening. 179 00:08:57.720 --> 00:08:59.919 Right By mapping that one hundred and fifty eight my 180 00:09:00.039 --> 00:09:03.960 chrometer emission, you are literally mapping the cold gas reservoir 181 00:09:04.240 --> 00:09:06.399 that fuels the whole galaxy. And the best part is 182 00:09:06.759 --> 00:09:09.720 at that wavelength, the light punches right through the dust 183 00:09:09.879 --> 00:09:11.559 that blocks our optical telescopes. 184 00:09:11.679 --> 00:09:14.320 It cuts right through the glare. So they point Alma 185 00:09:14.399 --> 00:09:17.000 at the system, they look for that specific carbon signal, 186 00:09:17.039 --> 00:09:18.919 and they find an absolute mess. 187 00:09:19.120 --> 00:09:21.919 They found a massive tidle bridge. It wasn't just two 188 00:09:22.000 --> 00:09:24.519 neat pools of gas around the black holes. There was 189 00:09:24.559 --> 00:09:29.519 a physical, contiguous stream of cold interstellar gas stretched across 190 00:09:29.559 --> 00:09:30.639 the space between. 191 00:09:30.320 --> 00:09:33.720 Them, ripped out by sheer gravitational violence. But let me 192 00:09:33.759 --> 00:09:37.240 play devil's advocate for a second. Couldn't a skeptic to say, well, 193 00:09:37.360 --> 00:09:40.679 maybe the lens is incredibly complex, maybe a weird four 194 00:09:40.720 --> 00:09:43.919 ground cluster is magnifying a background spiral arm to just 195 00:09:44.000 --> 00:09:45.039 look like a bridge. 196 00:09:45.120 --> 00:09:47.879 That is exactly the kind of rigor of the community demands. 197 00:09:48.200 --> 00:09:50.759 But LMA didn't just give us a static picture. It 198 00:09:50.759 --> 00:09:54.000 gave us kinematics. It showed us exactly how fast the 199 00:09:54.000 --> 00:09:55.639 gas in that bridge was moving. 200 00:09:55.440 --> 00:09:56.720 Because of the Doppler shift. 201 00:09:56.879 --> 00:10:01.039 Exactly. They mapped the velocity field and they found co plex, chaotic, 202 00:10:01.399 --> 00:10:05.000 non circular motions. A lensed spiral arm would still look 203 00:10:05.039 --> 00:10:07.320 like a spinning disc, just distorted. 204 00:10:06.840 --> 00:10:09.080 We'd have a neat orderly rotation. 205 00:10:08.919 --> 00:10:13.639 Right, But this was total kinematic chaos. Yeah, definitively the 206 00:10:13.720 --> 00:10:17.000 signature of two massive gravity wells tearing each other apart. 207 00:10:17.279 --> 00:10:19.679 The optical illusion theory was officially dead. 208 00:10:19.840 --> 00:10:23.279 Wow. So we are genuinely looking at two immense galaxies 209 00:10:23.279 --> 00:10:25.799 and a death spiral and finding this bridge of star 210 00:10:25.919 --> 00:10:29.080 forming gas just naturally leads us to the realization that 211 00:10:29.120 --> 00:10:32.480 these black holes aren't just destroying things. Far from it, right, 212 00:10:32.519 --> 00:10:36.240 They are residing in galaxies that are frantically creating new stars. 213 00:10:36.679 --> 00:10:40.919 These are literal star forming factories. The ALMA data showed 214 00:10:40.960 --> 00:10:43.399 that these host galaxies are incredibly massive. 215 00:10:43.480 --> 00:10:47.399 Oh, they're behemoths. The dynamical mass calculations show that each 216 00:10:47.440 --> 00:10:51.639 of these merging components is at least ten billion solar masses. 217 00:10:51.360 --> 00:10:55.879 Ten billion at redshift five point seven. That is highly evolved. 218 00:10:56.159 --> 00:10:59.399 We aren't talking about tiny dwarf galaxies bumping into each other. 219 00:10:59.480 --> 00:11:02.080 No, these are assive systems. But the number that really 220 00:11:02.159 --> 00:11:05.039 jumps out is the star formation rate. The data suggests 221 00:11:05.039 --> 00:11:07.679 they are churning out over five hundred solar masses of 222 00:11:07.759 --> 00:11:09.600 new stars every single year. 223 00:11:09.759 --> 00:11:11.600 Five hundred a year. I mean, just to ground that 224 00:11:11.759 --> 00:11:14.200 our own Milky Way produces what maybe one or two 225 00:11:14.279 --> 00:11:15.360 solar masses a year. 226 00:11:15.279 --> 00:11:17.399 Yeah, about one to two. So J twenty thirty seven 227 00:11:17.399 --> 00:11:20.519 four five three seven is operating in an overdrive that 228 00:11:20.639 --> 00:11:23.279 is hundreds of times more intense than our own galaxy. 229 00:11:23.399 --> 00:11:26.360 It's like an assembly line running at a dangerous frantic pace. 230 00:11:26.480 --> 00:11:28.120 If you were floating in the halo of one of 231 00:11:28.159 --> 00:11:30.639 these galaxies, the sky would just be a chaotic mess 232 00:11:30.639 --> 00:11:34.559 of ultraviolet light from massive young stars blowing up in supernovae. 233 00:11:34.720 --> 00:11:36.639 It'd be an incredibly violent engine of creation. 234 00:11:36.759 --> 00:11:38.480 Yeah, But I do want to push back on that 235 00:11:38.519 --> 00:11:42.360 five hundred number for a second, because the researchers explicitly 236 00:11:42.440 --> 00:11:47.799 mention systematic uncertainties regarding dust temperatures. If our calculations rely 237 00:11:48.000 --> 00:11:51.639 on assuming the temperature of invisible dust billions of light 238 00:11:51.720 --> 00:11:54.679 years away, how wildly could these numbers swing. 239 00:11:55.240 --> 00:11:58.120 That is a fantastic question, and it's a critical caveat 240 00:11:58.799 --> 00:12:02.200 When we measure starform rates with alma in this way, 241 00:12:02.559 --> 00:12:05.240 we are actually measuring the thermal glow of the dust, right. 242 00:12:05.279 --> 00:12:08.399 The dust absorbs the starlight and glows in the infrared exactly. 243 00:12:08.759 --> 00:12:11.480 And to calculate the total mass of that dust and 244 00:12:11.519 --> 00:12:14.519 therefore the star formation, we have to assume a dust 245 00:12:14.519 --> 00:12:18.600 temperature usually around forty five kelvin for these early galaxies. 246 00:12:18.639 --> 00:12:20.799 But it's an underdetermined system, right. We don't have enough 247 00:12:20.840 --> 00:12:22.039 data points to know for sure. 248 00:12:22.200 --> 00:12:24.519 Right, we only have a few data points on the spectrum. 249 00:12:24.639 --> 00:12:28.320 So what if the incredible radiation from the quasars and 250 00:12:28.399 --> 00:12:31.639 the sheer violence of the starburst has heated that dust 251 00:12:31.840 --> 00:12:34.399 up to say sixty five kelvin instead? 252 00:12:34.600 --> 00:12:37.279 Oh, because of the stuff and Boltzman law, hotter things 253 00:12:37.360 --> 00:12:39.399 radiate way more energy exactly. 254 00:12:39.440 --> 00:12:42.440 It scales to the fourth power of the temperature. So 255 00:12:42.480 --> 00:12:45.840 if the dust is hotter, you need significantly less dust 256 00:12:45.919 --> 00:12:48.519 mass to produce the bright glow we see. 257 00:12:49.320 --> 00:12:51.360 And if there's less dust, there's less gas, and your 258 00:12:51.440 --> 00:12:54.679 five hundred solar mass figure might be a massive overestimate. 259 00:12:54.759 --> 00:12:56.240 It could be off by a factor of two or 260 00:12:56.240 --> 00:12:59.519 three easily. On the flip side, if the dust has 261 00:12:59.519 --> 00:13:02.840 a different mmical composition, maybe more silicates in the early universe, 262 00:13:03.600 --> 00:13:05.080 the real rate could be even higher. 263 00:13:05.440 --> 00:13:08.320 Are we looking at a conservative baseline or could we 264 00:13:08.399 --> 00:13:10.840 be drastically overestimating the chaos. 265 00:13:11.000 --> 00:13:13.799 We won't know the exact number without follow up observations, 266 00:13:13.840 --> 00:13:16.720 maybe using the James Web Space telescope combined with deeper 267 00:13:16.960 --> 00:13:19.919 Ala maps. But honestly, even if the rate is three 268 00:13:20.000 --> 00:13:23.080 hundred instead of five hundred, the physical reality is the same. 269 00:13:23.200 --> 00:13:25.960 It's still an extreme starburst system exactly. 270 00:13:26.000 --> 00:13:29.519 The merger is violently compressing the gas, fueling the quasars, 271 00:13:29.720 --> 00:13:33.039 and sparking a massive, rapid assembly of stars all at 272 00:13:33.080 --> 00:13:33.559 the same time. 273 00:13:33.679 --> 00:13:36.759 It's just spectacular. So we've established the massive scale the 274 00:13:36.840 --> 00:13:39.679 violent waltz they're locked in. But this dance has a 275 00:13:39.679 --> 00:13:42.480 grand finale, right, a finale that won't happen for a. 276 00:13:42.519 --> 00:13:45.399 Very very long time, a very long time right now, 277 00:13:45.440 --> 00:13:47.200 at the moment we observe them at rench of five 278 00:13:47.240 --> 00:13:50.759 point seven, these supermassive black holes are still separated by 279 00:13:50.799 --> 00:13:54.200 thousands of late years. They aren't a true binary system. 280 00:13:54.320 --> 00:13:58.080 Yet they still have to navigate this incredibly chaotic, turbulent 281 00:13:58.279 --> 00:14:01.679 soup of gas and star just to get to each other. 282 00:14:02.080 --> 00:14:03.919 How do they actually close that gap? 283 00:14:04.200 --> 00:14:06.600 The main driver at these large scales is something called 284 00:14:06.679 --> 00:14:10.039 dynamical friction. As the black hole plows through the dense 285 00:14:10.080 --> 00:14:12.960 background of the galaxy, it's gravity pulls on the stars 286 00:14:12.960 --> 00:14:13.799 and gas around it. 287 00:14:13.799 --> 00:14:15.399 It deflects their orbits. 288 00:14:15.120 --> 00:14:17.600 Right, and as the black hole moves forward, it leads 289 00:14:17.639 --> 00:14:20.519 to behind a localized cluster a wake of all that 290 00:14:20.559 --> 00:14:21.600 material is just pulled on. 291 00:14:21.759 --> 00:14:24.360 Oh so it's literally dragging a heavy tail of stars 292 00:14:24.399 --> 00:14:25.000 behind it. 293 00:14:24.960 --> 00:14:28.480 Exactly, and the gravitational pull of that trailing wake acts 294 00:14:28.480 --> 00:14:32.360 as a constant break. It SAPs the black hole's kinetic energy, 295 00:14:32.360 --> 00:14:34.919 forcing it to slowly, relentlessly spiral inward. 296 00:14:35.200 --> 00:14:37.840 And the models say this dynamical friction process is going 297 00:14:37.879 --> 00:14:40.320 to take a staggering amount of time. For j twenty 298 00:14:40.320 --> 00:14:42.919 three h thirty seven four five thirty seven, something like 299 00:14:42.960 --> 00:14:44.440 two point one billion years. 300 00:14:44.600 --> 00:14:47.799 Right, It will take over two billion years for them 301 00:14:47.840 --> 00:14:51.440 to finally become a gravitationally bound binary, which would happen 302 00:14:51.440 --> 00:14:52.360 around redshift two. 303 00:14:52.720 --> 00:14:54.720 But just getting to the center isn't the end of 304 00:14:54.759 --> 00:14:58.080 the story. Once they get really close, like within a 305 00:14:58.120 --> 00:15:01.799 parsec of each other, that friction stops working, doesn't it. 306 00:15:01.799 --> 00:15:05.320 It does. It's called the final parsec problem. The volume 307 00:15:05.360 --> 00:15:08.559 of space gets too small to hold enough background stars 308 00:15:08.799 --> 00:15:09.960 to create that drag. 309 00:15:10.360 --> 00:15:12.399 So how do they keep falling inward? Do they just 310 00:15:12.519 --> 00:15:13.120 stall out? 311 00:15:13.440 --> 00:15:16.440 If it were a dry merger without gas, they might stall, 312 00:15:17.080 --> 00:15:20.360 But here they enter the hardening phase. The binary acts 313 00:15:20.399 --> 00:15:23.879 like a giant gravitational baseball bat. Any star that wanders 314 00:15:23.879 --> 00:15:26.559 too close gets violently ejected from the galactic center. 315 00:15:26.639 --> 00:15:29.039 Oh wow, it just slingshots stars away. 316 00:15:29.000 --> 00:15:32.039 Exactly, and the energy to kick that star out comes 317 00:15:32.039 --> 00:15:34.799 from the black hole's orbit. So they step slightly closer together, 318 00:15:35.320 --> 00:15:37.440 but eventually they kick away all the stars in the center. 319 00:15:37.519 --> 00:15:38.759 They run out amo. 320 00:15:38.600 --> 00:15:40.799 Right, they clear out the whole core. So what bridge 321 00:15:40.799 --> 00:15:41.759 is that final gap? 322 00:15:42.120 --> 00:15:45.679 The gas? Because this is a very wet, gas rich merger. 323 00:15:46.360 --> 00:15:50.000 The black holes are swimming in a massive circumbinary accretion disc. 324 00:15:50.600 --> 00:15:54.200 The sheer viscous friction of that gas provides the drag 325 00:15:54.320 --> 00:15:57.279 needed to push them down to milliparsec scales. 326 00:15:57.399 --> 00:16:00.200 And once they get that close, separated by mirror light 327 00:16:00.240 --> 00:16:02.480 months and moving at a huge fraction of the speed 328 00:16:02.480 --> 00:16:07.360 of light, physics fundamentally shifts. General relativity totally takes over. 329 00:16:07.600 --> 00:16:11.279 Absolutely at that point. The dominant way they lose energy 330 00:16:11.399 --> 00:16:13.759 is by radiating gravitational waves. 331 00:16:13.559 --> 00:16:16.639 Ripples in the literal fabric of space time, and this 332 00:16:16.639 --> 00:16:20.879 connects our ancient red shift five point seven quasars directly 333 00:16:20.960 --> 00:16:23.519 to the most cutting edge physics happening right now on Earth. 334 00:16:23.559 --> 00:16:26.200 Because these aren't the quick, high frequency chirps we hear 335 00:16:26.200 --> 00:16:28.159 from small black holes with ligo right. 336 00:16:28.120 --> 00:16:31.399 No, not at all. A supermassive black hole binary takes 337 00:16:31.480 --> 00:16:34.799 millions of years to inspiral. The gravitational waves they produce 338 00:16:34.799 --> 00:16:38.600 have incredibly long wavelengths. We're talking nanohurtz frequencies. 339 00:16:38.200 --> 00:16:40.759 So the wave takes years just to complete a single oscillation. 340 00:16:40.840 --> 00:16:42.960 You can't catch that in a laboratory. 341 00:16:42.519 --> 00:16:45.279 No, you need a detector the size of a galaxy. 342 00:16:44.960 --> 00:16:48.399 Which is exactly what pulsar timing arrays are it's brilliant. 343 00:16:48.919 --> 00:16:52.720 We use millisecond pulsars, these rapidly spinning dead stars that 344 00:16:52.720 --> 00:16:56.720 shoot radio beams at Earth with perfect precision, like cosmic clocks. 345 00:16:56.960 --> 00:16:59.360 They are staggeringly precise. 346 00:16:59.039 --> 00:17:02.639 And if a massive of nanohertz gravitational wave rolls through 347 00:17:02.639 --> 00:17:06.160 the Milky Way, it actually stretches and squeezes the space 348 00:17:06.240 --> 00:17:08.160 between Earth and those pulsars. 349 00:17:08.240 --> 00:17:12.119 Right the distance the radio pulse has to travel physically changes, which. 350 00:17:11.880 --> 00:17:14.640 Means the pulse arrives just a tiny fraction of a 351 00:17:14.680 --> 00:17:18.960 microsecond early or late. And by monitoring dozens of these pulsars, 352 00:17:19.240 --> 00:17:22.640 scientists act like a giant cosmic seismograph, listening for that 353 00:17:22.799 --> 00:17:23.799 rumble exactly. 354 00:17:24.240 --> 00:17:27.559 Groups like Nanograph have actually found compelling evidence for this recently, 355 00:17:27.880 --> 00:17:32.079 a stochastic gravitational wave background. It's a constant, low frequency 356 00:17:32.160 --> 00:17:34.079 hum vibrating through the universe. 357 00:17:34.119 --> 00:17:37.319 It's the combine noise of millions of supermassive black holes 358 00:17:37.319 --> 00:17:40.480 slowly spiraling together across all of cosmic time, like the 359 00:17:40.559 --> 00:17:43.240 low rumble of distant traffic in a busy city. 360 00:17:43.359 --> 00:17:45.640 That's exactly what it is. But here is the kicker. 361 00:17:46.200 --> 00:17:48.880 The background hum they detected is actually stronger than our 362 00:17:48.920 --> 00:17:50.240 baseline models predicted. 363 00:17:50.440 --> 00:17:53.359 Wait, really, so if it's louder than expected, does that 364 00:17:53.440 --> 00:17:56.160 mean our fundamental ideas about how crowded and violent the 365 00:17:56.240 --> 00:17:58.680 early universe was have just been too conservative. 366 00:17:59.000 --> 00:18:02.079 That is the leading thing right now. A louder hum 367 00:18:02.359 --> 00:18:06.400 means there are either more supermassive binaries out there, or 368 00:18:06.640 --> 00:18:08.680 they're much more massive than we thought. 369 00:18:08.839 --> 00:18:10.839 And that brings us right back to j twenty three 370 00:18:11.000 --> 00:18:13.200 seven four five three seven exactly. 371 00:18:13.799 --> 00:18:17.599 If massive chaotic dust and shrouded early mergers like this 372 00:18:17.720 --> 00:18:21.039 are more common than we realized, which optal surveys missed 373 00:18:21.039 --> 00:18:23.319 because of the dust, then they could be the exact 374 00:18:23.359 --> 00:18:25.039 source of that extra gravitational noise. 375 00:18:25.119 --> 00:18:28.400 Wow, it's a perfect loop. We use the submillimeter ALMA 376 00:18:28.519 --> 00:18:30.920 data to prove the quasar pair exists and cut through 377 00:18:30.920 --> 00:18:34.880 the optical illusion, and that proves these massive early mergers happen, 378 00:18:34.960 --> 00:18:39.079 which perfectly explains the invisible gravitational hum vibrating through our detectors. 379 00:18:39.240 --> 00:18:41.799 Right now, it links the entire history of the cosmos 380 00:18:41.880 --> 00:18:43.519 into one mechanical framework. 381 00:18:43.920 --> 00:18:46.319 It really does. I mean, we started with a suspicious, 382 00:18:46.400 --> 00:18:49.799 tiny dot at the edge of the observable universe. We 383 00:18:49.920 --> 00:18:53.559 unpack the invisible ionized carbon, mapped the tidal wreckage of 384 00:18:53.559 --> 00:18:57.000 galaxies churning out five hundred stars a year, and tracked 385 00:18:57.039 --> 00:19:00.640 their brutal two point one billion year or decay. 386 00:19:00.680 --> 00:19:04.200 And the timeline of that decay is just it's fundamentally 387 00:19:04.240 --> 00:19:05.240 hard to wrap your head around. 388 00:19:05.279 --> 00:19:08.240 It is because we are observing them at redshift five 389 00:19:08.279 --> 00:19:11.400 point seven. The light we just analyzed has been traveling 390 00:19:11.440 --> 00:19:15.680 through expanding space for nearly thirteen billion years. But the 391 00:19:15.720 --> 00:19:18.440 actual physics we just talked about, the friction, the scattering, 392 00:19:18.480 --> 00:19:22.480 the final merger only takes two point one billion years, right, 393 00:19:22.759 --> 00:19:25.920 which means from an objective standpoint, the future of these 394 00:19:25.920 --> 00:19:29.359 black holes is already ancient history. They merged over ten 395 00:19:29.480 --> 00:19:30.400 billion years ago. 396 00:19:30.640 --> 00:19:34.079 That grand finale happened before our Solar system even existed exactly. 397 00:19:34.440 --> 00:19:37.519 The immense burst of gravitational waves from their final collision 398 00:19:37.720 --> 00:19:40.559 was injected into space time billions of years before the 399 00:19:40.640 --> 00:19:43.480 Earth formed. Yet, because those ripples travel at the speed 400 00:19:43.480 --> 00:19:46.640 of light just like the photons, those exact shockwaves are 401 00:19:46.680 --> 00:19:48.000