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 --> 00:00:23.839 slumber under the night sky. 7 00:00:26.920 --> 00:00:29.399 Welcome back. We're about to jump into one of the biggest, 8 00:00:30.480 --> 00:00:33.799 uh most frustrating puzzles in astronomy today. 9 00:00:33.880 --> 00:00:35.679 It really is. It's a genuine mystery. 10 00:00:35.799 --> 00:00:38.679 We found what over five thousand planets outside our solar 11 00:00:38.679 --> 00:00:40.039 system something like that. 12 00:00:40.119 --> 00:00:44.320 Thousands, yes, hot Jupiter's super earths, you name it. We're 13 00:00:44.320 --> 00:00:46.320 a getting really good at finding planets. 14 00:00:46.039 --> 00:00:48.320 Especially the big ones, the gas giants. And if you 15 00:00:48.320 --> 00:00:52.240 look at our own solar system, Jupiter Saturn, they're just 16 00:00:52.280 --> 00:00:53.359 swarming with moons. 17 00:00:53.479 --> 00:00:56.000 Absolutely, They're like miniature solar systems in their own right. 18 00:00:56.240 --> 00:00:59.119 So the big question, the one that vexes everyone, is 19 00:00:59.520 --> 00:01:01.000 where are all the exo moons? 20 00:01:01.520 --> 00:01:06.719 Exactly statistically they should be everywhere, billions of them. Yet 21 00:01:06.719 --> 00:01:10.760 as of today, we have zero confirmed exomoons, not a 22 00:01:10.799 --> 00:01:11.519 single one. 23 00:01:11.719 --> 00:01:14.040 An absence of evidence, as they say, but that's not 24 00:01:14.079 --> 00:01:16.280 evidence of absence. It just means we might be looking 25 00:01:16.319 --> 00:01:17.280 for them in the wrong way. 26 00:01:17.359 --> 00:01:19.640 And that's precisely what a new paper we've been digging 27 00:01:19.680 --> 00:01:22.159 into suggests. It's by Thomas Winterholder and his. 28 00:01:22.159 --> 00:01:24.640 Colleagues, right, it's on the ARCSIFF preprint server, so you 29 00:01:24.640 --> 00:01:25.680 can go check it out. 30 00:01:25.799 --> 00:01:31.120 And it lays out this really clear verdict. It basically says, look, 31 00:01:31.200 --> 00:01:34.239 the moons are there. The problem isn't the universe. The 32 00:01:34.280 --> 00:01:39.680 problem is us. Our technology is for this specific task crippled. 33 00:01:40.040 --> 00:01:43.159 So that's our mission today. We're going to unpack why 34 00:01:43.239 --> 00:01:46.319 our current methods are failing us, what some are calling 35 00:01:46.359 --> 00:01:47.280 the transit. 36 00:01:46.920 --> 00:01:49.680 Trap, and then we'll get into the exciting part, the 37 00:01:49.840 --> 00:01:51.400 proposed solution. 38 00:01:51.239 --> 00:01:55.719 A completely new technological path forward. The paper details how 39 00:01:55.719 --> 00:01:58.760 we could build something capable of finding Earth sized moons 40 00:01:59.239 --> 00:02:01.280 up to what was it, two hundred parsecs away? 41 00:02:01.319 --> 00:02:04.239 Two hundred parsex that's about six hundred and fifty light years. 42 00:02:04.400 --> 00:02:07.000 So we're not just talking about our immediate stellar neighborhood. 43 00:02:07.000 --> 00:02:09.599 We're talking about a serious, wide scale survey of our 44 00:02:09.639 --> 00:02:12.199 corner of the galaxy. So okay, let's start at the 45 00:02:12.199 --> 00:02:15.680 beginning the transit trap. Why are our best planet hunting 46 00:02:15.719 --> 00:02:18.039 tools failing so badly at finding moons? 47 00:02:18.520 --> 00:02:21.439 It all comes down to the workhourse of exoplanet detection, 48 00:02:21.719 --> 00:02:24.960 the transit method. It's given us thousands of planets, and. 49 00:02:24.919 --> 00:02:27.520 It's I mean, it's an elegantly simple idea. Right, You 50 00:02:27.560 --> 00:02:28.199 scare at a star. 51 00:02:28.319 --> 00:02:29.719 You stare at a star and you wait for it 52 00:02:29.759 --> 00:02:30.840 to blink exactly. 53 00:02:31.319 --> 00:02:33.960 You watch for a tiny, tiny dip in its brightness, 54 00:02:34.280 --> 00:02:37.719 and if that dip happens regularly, like clockwork. 55 00:02:37.560 --> 00:02:40.439 Then you can be pretty sure something a planet is 56 00:02:40.479 --> 00:02:42.080 passing in front of it. From our point of view, 57 00:02:42.360 --> 00:02:44.080 it's blocking a little bit of the starlight. 58 00:02:44.319 --> 00:02:48.800 It's been incredibly successful missions like Kepler Tess. They've used 59 00:02:48.800 --> 00:02:51.159 this to build our entire catalog of worlds. 60 00:02:51.319 --> 00:02:53.759 But when you try to apply that same logic to 61 00:02:54.319 --> 00:02:57.280 finding a moon orbiting that planet, the whole thing just 62 00:02:57.319 --> 00:02:58.000 falls apart. 63 00:02:58.199 --> 00:03:01.319 Why. I mean, a moon would block life too, wouldn't it? 64 00:03:01.319 --> 00:03:04.120 It would? But the problem is alignment. For a planet, 65 00:03:04.159 --> 00:03:07.280 you need three things lined up, the star, the planet, 66 00:03:07.360 --> 00:03:08.639 and us here on Earth. 67 00:03:08.719 --> 00:03:11.240 Okay, that's already a pretty rare alignment it is. 68 00:03:11.439 --> 00:03:13.960 Now for a moon, you need four things to line up. 69 00:03:14.319 --> 00:03:17.400 The star, the planet, the Moon, and us, and not 70 00:03:17.479 --> 00:03:19.639 just lined up, but at the exact moment the Moon 71 00:03:19.759 --> 00:03:21.159 is also transiting the star. 72 00:03:21.719 --> 00:03:23.680 So the Moon has to be in the right place 73 00:03:23.840 --> 00:03:25.879 in its own little orbit around the planet at the 74 00:03:25.919 --> 00:03:28.159 exact same time the planet is in the right place 75 00:03:28.520 --> 00:03:31.400 in its giant orbit around the star precisely. 76 00:03:31.599 --> 00:03:34.520 And the signal you get is incredibly complex. It might 77 00:03:34.560 --> 00:03:38.039 be a tiny dip before or after the main planet's transit. 78 00:03:38.360 --> 00:03:40.599 It might even just subtly change the shape of the 79 00:03:40.599 --> 00:03:41.479 planet's dip. 80 00:03:41.360 --> 00:03:43.879 And you're trying to pick that out from hundreds of 81 00:03:43.960 --> 00:03:44.719 light years away. 82 00:03:45.000 --> 00:03:47.400 You're trying to distinguish that from all the other noise 83 00:03:47.960 --> 00:03:51.000 the star it sell flickers, you have instrument noise. It's 84 00:03:51.039 --> 00:03:55.800 a statistical nightmare. The odds of that perfect celestial choreography 85 00:03:55.800 --> 00:03:57.840 happening are just astronomically low. 86 00:03:58.039 --> 00:04:00.400 But that's not even the real killer, is it. There's 87 00:04:00.439 --> 00:04:03.800 a much deeper, more fundamental problem with using transits. 88 00:04:03.960 --> 00:04:06.199 That's right, and this is the core of the issue. 89 00:04:06.280 --> 00:04:09.479 It's a physics constraint. We need to talk about something 90 00:04:09.479 --> 00:04:10.520 called the hill sphere. 91 00:04:10.719 --> 00:04:12.599 The hillsphere. Okay, break that down for us. 92 00:04:13.080 --> 00:04:16.240 The hill sphere is the best way to think of 93 00:04:16.240 --> 00:04:19.480 it is as a planet's gravitational zone of influence. It's 94 00:04:19.519 --> 00:04:22.000 a bubble of space around the planet where its own 95 00:04:22.079 --> 00:04:23.319 gravity is the boss. 96 00:04:23.519 --> 00:04:26.800 So inside that bubble, the planet's gravity is stronger than 97 00:04:26.839 --> 00:04:28.160 the star's gravity. 98 00:04:27.800 --> 00:04:30.639 Strong enough to hold on to something. Yes, if an 99 00:04:30.639 --> 00:04:33.639 object like a moon is inside the hillsphere, the planet 100 00:04:33.639 --> 00:04:36.319 can keep it in a stable long term orbit, and 101 00:04:36.319 --> 00:04:39.720 if it's outside the stars gravity wins. It'll either rip 102 00:04:39.759 --> 00:04:43.360 the moon away or destabilize its orbit until it's ejected 103 00:04:43.360 --> 00:04:46.360 from the system. So the size of that hillsphere is 104 00:04:46.480 --> 00:04:49.759 absolutely critical. It dictates how much room a planet has 105 00:04:49.800 --> 00:04:50.680 to keep its moons. 106 00:04:50.839 --> 00:04:55.240 Okay, so a bigger hillsphere means more stable moons, or 107 00:04:55.279 --> 00:04:57.600 at least the potential for them exactly. 108 00:04:58.000 --> 00:05:01.399 And here is the paradox. Transit method. The one we've 109 00:05:01.439 --> 00:05:04.040 been using works best for planets that are very close 110 00:05:04.079 --> 00:05:04.720 to their star. 111 00:05:05.120 --> 00:05:07.759 Right because they orbit quickly, they transit all the time, 112 00:05:07.959 --> 00:05:09.879 so we get lots of data points and can confirm 113 00:05:09.879 --> 00:05:12.560 them easily the hot Jupiter's precisely. 114 00:05:12.720 --> 00:05:15.240 But what happens when a planet is very close to 115 00:05:15.279 --> 00:05:15.720 its star. 116 00:05:15.959 --> 00:05:18.879 The star's gravity is much much stronger. 117 00:05:18.519 --> 00:05:22.600 There, overwhelmingly strong, and that immense gravitational pull from the 118 00:05:22.600 --> 00:05:25.759 star shrinks the planet's hillsphere down to almost nothing. 119 00:05:25.959 --> 00:05:28.319 So let me get this straight. The planets that are 120 00:05:28.399 --> 00:05:30.759 easiest for us to find with our best method are 121 00:05:30.800 --> 00:05:31.160 in the. 122 00:05:31.199 --> 00:05:34.199 Very region where it's gravitationally hardest for them to hold 123 00:05:34.279 --> 00:05:35.920 onto moons in the first place. 124 00:05:35.759 --> 00:05:38.199 We've been looking in the absolute worst place we have. 125 00:05:38.279 --> 00:05:41.800 We've perfected a tool that is biased towards finding planets 126 00:05:41.800 --> 00:05:44.639 and environments that are actively hostile to the very things 127 00:05:44.680 --> 00:05:47.000 we're looking for. It's a fundamental mismatch. 128 00:05:47.120 --> 00:05:50.480 It makes you wonder, was this a huge oversight? Why 129 00:05:50.519 --> 00:05:53.160 do we spend decades on a method that was doomed 130 00:05:53.240 --> 00:05:54.600 to fail for moon hunting. 131 00:05:55.120 --> 00:05:58.839 It wasn't really an oversight so much as a necessary 132 00:05:59.040 --> 00:06:02.839 first step. We had to prove exoplanets were common first. 133 00:06:03.360 --> 00:06:06.199 The transit method was the fastest, cheapest way to do that. 134 00:06:06.639 --> 00:06:09.160 It gave us the numbers, the low hanging fruit, but 135 00:06:09.240 --> 00:06:10.040 that fruit. 136 00:06:09.800 --> 00:06:12.199 Was growing in a very barren orchard. 137 00:06:12.040 --> 00:06:14.720 So to speak, a barren orchard for moons. Yes, we 138 00:06:14.759 --> 00:06:17.360 had to build the catalog of planets first. But now 139 00:06:17.360 --> 00:06:19.720 that we know they're everywhere. We need a new tool. 140 00:06:20.120 --> 00:06:22.720 We need to shift our focus to planets much much 141 00:06:22.759 --> 00:06:24.120 farther away from their stars. 142 00:06:24.240 --> 00:06:26.480 And there's a really famous example that just drives this 143 00:06:26.519 --> 00:06:29.439 point home right. The whole story with Kepler sixteen twenty. 144 00:06:29.120 --> 00:06:32.319 Five b oh, Yes, the great exomoon candidate that wasn't. 145 00:06:32.839 --> 00:06:34.160 For a moment we thought we had one. 146 00:06:34.199 --> 00:06:37.199 The whole community was buzzing. The initial data from Kepler 147 00:06:37.240 --> 00:06:40.839 showed this gas giant and there was this weird, extra 148 00:06:41.000 --> 00:06:42.759 little dip in the light after the main. 149 00:06:42.600 --> 00:06:45.759 Transit, and the main transit seemed to start a bit early, 150 00:06:46.199 --> 00:06:48.519 which hinted that the planet was being tugged on by 151 00:06:48.560 --> 00:06:51.959 something a wabble. The signs pointed to a big moon, 152 00:06:52.160 --> 00:06:53.399 maybe the size of Neptune. 153 00:06:53.959 --> 00:06:55.680 It felt like we were right on the edge of 154 00:06:55.720 --> 00:06:57.000 a historic discovery. 155 00:06:57.160 --> 00:06:59.879 We were, so they pointed the Hubble Space telescope at 156 00:06:59.920 --> 00:07:02.639 it to get a better look to confirm it, and 157 00:07:02.680 --> 00:07:06.319 the data was messy. It was ambiguous. Some analyses still 158 00:07:06.360 --> 00:07:09.040 saw the moon's signal, others said it was gone. It 159 00:07:09.160 --> 00:07:12.040 just sort of dissolved under closer scrutiny, So. 160 00:07:12.000 --> 00:07:15.079 It's likely just instrument noise or some weird stellar activity 161 00:07:15.079 --> 00:07:15.959 that mimicked the moon. 162 00:07:16.480 --> 00:07:20.199 That's the consensus. Now, yes, yeah, the discovery was essentially debunked, 163 00:07:20.560 --> 00:07:23.680 and the whole saga is the perfect illustration of the problem. 164 00:07:23.959 --> 00:07:26.759 Even in a best case scenario, the transit signal is 165 00:07:26.839 --> 00:07:29.759 so faint, so close to the noise that it's almost 166 00:07:29.759 --> 00:07:30.839 impossible to be sure. 167 00:07:31.199 --> 00:07:33.560 So if the transit method is a bust, we need 168 00:07:33.600 --> 00:07:35.920 a whole new approach. And this is where the new 169 00:07:35.920 --> 00:07:37.120 paper gets really interesting. 170 00:07:37.240 --> 00:07:39.120 This is where we stop looking for a shadow and 171 00:07:39.120 --> 00:07:41.240 we start looking for gravity itself. 172 00:07:41.360 --> 00:07:43.120 The technique is called astrometry. 173 00:07:43.319 --> 00:07:46.439 Astrometry it's one of the oldest branches of astronomy, but 174 00:07:46.480 --> 00:07:48.759 we're now applying it with a level of precision that 175 00:07:48.879 --> 00:07:51.600 is just mind boggling. 176 00:07:51.639 --> 00:07:55.240 So astronometry is basically just measuring the precise position of 177 00:07:55.279 --> 00:07:56.800 things in the sky and their movement. 178 00:07:56.920 --> 00:07:59.800 Yes, when we use it to find a planet, we're 179 00:08:00.079 --> 00:08:02.639 not looking at the planet at all. We're looking at 180 00:08:02.680 --> 00:08:06.639 its star, and we're watching the star wobble Exactly. A 181 00:08:06.680 --> 00:08:09.439 planet's gravity pulls on its star just as the star 182 00:08:09.519 --> 00:08:12.399 pulls on the planet. They both orbit a shared center 183 00:08:12.439 --> 00:08:15.160 of mass, so the star isn't stationary. It makes these 184 00:08:15.199 --> 00:08:18.040 tiny little circles in the sky. If we can measure 185 00:08:18.079 --> 00:08:19.959 that wobble, we know a planet is there. 186 00:08:20.160 --> 00:08:22.680 Okay, so that's for planets. How do we apply that 187 00:08:22.720 --> 00:08:23.240 to moons? 188 00:08:23.480 --> 00:08:26.160 We just shift our focus. Instead of watching the star wobble, 189 00:08:26.480 --> 00:08:27.879 we watch the planet wobble. 190 00:08:28.000 --> 00:08:30.639 Ah, because the moon is pulling on the planet. 191 00:08:30.759 --> 00:08:34.279 Right, The planet and its moon are also orbiting their 192 00:08:34.320 --> 00:08:37.559 own little center of mass, their Berry center. So as 193 00:08:37.600 --> 00:08:40.440 the planet moves through its huge orbit around the star, 194 00:08:40.799 --> 00:08:43.200 it's not tracing a smooth, clean arc. 195 00:08:43.360 --> 00:08:45.840 It's doing a little quarkscrew pattern, tiny wobble on top 196 00:08:45.840 --> 00:08:46.840 of its main orbit. 197 00:08:46.759 --> 00:08:50.240 A tiny subtle dance. And if we can measure that dance, 198 00:08:50.360 --> 00:08:52.200 we've found the moon that's leading it. 199 00:08:52.679 --> 00:08:55.840 Now, this feels like a much better approach, and it 200 00:08:55.919 --> 00:08:58.519 directly solves the Hillsphere problem, doesn't it. 201 00:08:58.519 --> 00:09:02.039 It completely flips the scar. The beautiful thing about astrometry 202 00:09:02.399 --> 00:09:04.559 is that it works best for planets that are far 203 00:09:04.639 --> 00:09:07.879 away from their star. Why is that Well, a more 204 00:09:07.919 --> 00:09:10.840 distant orbit is a longer orbit, which gives you more 205 00:09:10.879 --> 00:09:13.919 time to measure the wabble and separate it from other signals. 206 00:09:14.440 --> 00:09:18.200 But more importantly, planets far from their star are free 207 00:09:18.240 --> 00:09:23.279 from the star's intense gravitational mettling, which means they have huge, 208 00:09:23.840 --> 00:09:26.360 stable hill spheres. They have all the room in the 209 00:09:26.399 --> 00:09:28.759 world to capture and hold on to large families of 210 00:09:28.799 --> 00:09:30.320 moons for billions of years. 211 00:09:30.399 --> 00:09:33.639 So astrometry naturally points us to the most promising systems. 212 00:09:33.679 --> 00:09:37.000 It's bias towards the gravitationally friendly neighborhoods exactly. 213 00:09:37.279 --> 00:09:40.559 It resolves the paradox that crippled the transit method. It 214 00:09:40.639 --> 00:09:42.759 lets us finally look in the right place. 215 00:09:42.559 --> 00:09:46.000 Which brings up the obvious question, if the strometry is 216 00:09:46.000 --> 00:09:48.840 so much better, why haven't we been doing this all along? 217 00:09:49.200 --> 00:09:52.679 Ah, because of what the paper calls the technological deficit. 218 00:09:53.000 --> 00:09:56.000 The principle is sound, but the reality of the measurement 219 00:09:56.080 --> 00:09:56.840 is the problem. 220 00:09:57.240 --> 00:09:59.200 The wobble is just too small to see with what 221 00:09:59.240 --> 00:09:59.960 we have now. 222 00:10:00.080 --> 00:10:04.039 Almost infinitesimally small. When you're looking at a planet hundreds 223 00:10:04.039 --> 00:10:08.159 of light years away, the precision required is just staggering. 224 00:10:08.679 --> 00:10:12.600 Let's talk scale. What can our best telescopes do right now? 225 00:10:12.759 --> 00:10:16.639 Our current champion is the very large telescope in our barometer, 226 00:10:16.759 --> 00:10:19.399 the VLTI down in Chile. It's an incredible machine and 227 00:10:19.519 --> 00:10:19.799 that's not. 228 00:10:19.799 --> 00:10:22.639 One telescope, right, It combines the light from multiple one correct. 229 00:10:22.720 --> 00:10:25.399 It links its four main telescopes together to act as 230 00:10:25.480 --> 00:10:29.440 one giant virtual telescope, and with that it can resolve 231 00:10:29.480 --> 00:10:33.080 an angular wobble of about fifty micro arc seconds fifty ens. 232 00:10:33.200 --> 00:10:35.200 Okay, you have to put that number in perspective for us. 233 00:10:35.440 --> 00:10:36.960 What is a micro arc second? 234 00:10:37.000 --> 00:10:40.240 Okay, So imagine a single degree in the sky. Divide 235 00:10:40.240 --> 00:10:43.200 that by three thy six hundred. That's an arcsecond already tiny. 236 00:10:43.240 --> 00:10:45.440 Now divide that arc second by another million, that's a 237 00:10:45.480 --> 00:10:46.879 micro arcsecond one ears. 238 00:10:47.039 --> 00:10:50.159 So fifty micro arc seconds is already measuring a movement 239 00:10:50.240 --> 00:10:54.120 that is just an absurdly small fraction of a degree. 240 00:10:54.200 --> 00:10:56.639 It is. The common analogy is that it's like being 241 00:10:56.679 --> 00:10:59.759 able to spot a single human hair from two miles away. 242 00:11:00.159 --> 00:11:03.120 That's what fifty a's resolution gets you. It's a breath 243 00:11:03.200 --> 00:11:04.720 taking achievement of engineering. 244 00:11:04.919 --> 00:11:05.879 But it's not good enough. 245 00:11:06.039 --> 00:11:09.080 It's not even close. The wobble induced by an Earth 246 00:11:09.159 --> 00:11:12.759 sized moon orbiting a gas giant two hundred parsecs away 247 00:11:13.080 --> 00:11:16.080 is far, far smaller than that fifty a's limit. 248 00:11:15.919 --> 00:11:19.320 And the VLTI gets that resolution by having its telescopes 249 00:11:19.399 --> 00:11:22.240 spread out over a distance a baseline of about two 250 00:11:22.320 --> 00:11:23.279 hundred meters. 251 00:11:23.080 --> 00:11:25.919 Right about the length of two football fields. But to 252 00:11:26.000 --> 00:11:29.039 find these moons we need to bridge a monumental gap. 253 00:11:29.360 --> 00:11:31.240 We're not talking about a small improvement. 254 00:11:31.440 --> 00:11:34.080 We're talking about a leap, and the paper by winter 255 00:11:34.159 --> 00:11:37.240 Holder is very specific about how big that leap needs 256 00:11:37.240 --> 00:11:37.440 to be. 257 00:11:37.639 --> 00:11:40.279 It is. It calculates that to find what they call 258 00:11:40.360 --> 00:11:43.720 a reasonable number of Earth sized exomoons out to that 259 00:11:43.759 --> 00:11:47.240 two hundred parsec distance, you need a resolution of around 260 00:11:47.279 --> 00:11:49.679 one micro arc second one as. 261 00:11:49.360 --> 00:11:52.080 So from fifty down to one, that's a fiftyfold increase 262 00:11:52.080 --> 00:11:52.639 in precision. 263 00:11:52.720 --> 00:11:56.000 A fiftyfold jump. That's not an incremental upgrade. That requires 264 00:11:56.039 --> 00:11:58.759 a fundamental rethinking of how we build an observatory. 265 00:11:59.120 --> 00:12:02.919 Soans is seeing a hair from two miles away. What's 266 00:12:02.960 --> 00:12:04.320 the analogy for one curation? 267 00:12:04.559 --> 00:12:07.159 The one I've heard is it's the equivalent of measuring 268 00:12:07.200 --> 00:12:10.440 the width of a small coin, say a nickel. If 269 00:12:10.440 --> 00:12:12.320 that coin we're sitting on the surface of the Moon. 270 00:12:12.799 --> 00:12:14.679 You're trying to measure the width of a nickel on 271 00:12:14.720 --> 00:12:16.159 the Moon from Earth. 272 00:12:16.320 --> 00:12:19.159 That's the angular scale we're aiming for. It's measuring a 273 00:12:19.279 --> 00:12:22.519 tiny movement of an object that is itself more than 274 00:12:22.559 --> 00:12:25.120 a million times farther away than the moon. This is 275 00:12:25.159 --> 00:12:26.519 an immense challenge. 276 00:12:26.200 --> 00:12:27.399 Jo, How do you do it? How do you get 277 00:12:27.399 --> 00:12:29.399 a fifty fold increase in resolution? 278 00:12:29.679 --> 00:12:32.759 You have to go back to the basic physics of interferometry. 279 00:12:33.360 --> 00:12:37.240 There's a simple equation. Your resolution is equal to the 280 00:12:37.279 --> 00:12:41.399 wavelength of the light you're observing, divided by your baseline. 281 00:12:41.480 --> 00:12:44.320 Okay, so resolution equals wavelength over baseline. 282 00:12:44.399 --> 00:12:47.240 Right, we can't really change the wavelength. That's just the 283 00:12:47.240 --> 00:12:49.360 starlight we're looking at. So if you want to increase 284 00:12:49.360 --> 00:12:50.320 your resolution by a. 285 00:12:50.279 --> 00:12:52.799 Factor of fifty, you have to increase your baseline by 286 00:12:52.840 --> 00:12:53.679 a factor of fifty. 287 00:12:53.879 --> 00:12:57.480 Exactly, if the vlti is two hundred meters baseline gets 288 00:12:57.559 --> 00:13:00.519 you fifty coins, then to get to one oins, you 289 00:13:00.559 --> 00:13:02.399 need a baseline that's fifty times longer. 290 00:13:02.600 --> 00:13:08.759 Two hundred meters times fifty is ten thousand meters, ten kilometers. 291 00:13:08.200 --> 00:13:11.159 Several kilometers. Yes, this is the heart of the proposal. 292 00:13:11.200 --> 00:13:13.320 We have to stop thinking in terms of hundreds of 293 00:13:13.399 --> 00:13:16.440 meters and start thinking in terms of kilometers. This is 294 00:13:16.440 --> 00:13:19.440 why they call it a kilometric baseline interferometer. 295 00:13:19.600 --> 00:13:21.960 So you're not building one giant telescope, you're building an 296 00:13:22.120 --> 00:13:25.519 array of smaller telescopes spread out over an entire valley. 297 00:13:25.559 --> 00:13:29.159 Maybe that's the concept. A whole network of light collecting 298 00:13:29.159 --> 00:13:32.879 stations spread out over kilometers, all linked together optically with 299 00:13:32.960 --> 00:13:35.879 a precision that is almost hard to comprehend. They have 300 00:13:35.960 --> 00:13:38.679 to act as a single coherent instrument. 301 00:13:38.840 --> 00:13:41.600 How is that even possible? Keeping the light from mirrors 302 00:13:41.720 --> 00:13:43.879 kilometers apart perfectly in sync. 303 00:13:44.320 --> 00:13:47.480 That's the insane engineering challenge. It involves a thing called 304 00:13:47.559 --> 00:13:51.679 optical delay lines, basically long vacuum tunnels with mirrors that 305 00:13:51.720 --> 00:13:54.519 can move to precisely adjust the path length of the 306 00:13:54.639 --> 00:13:55.879 light from each station. 307 00:13:56.200 --> 00:13:58.720 So the light from a faraway mirror has to travel further, 308 00:13:59.120 --> 00:14:01.840 and these tunnels come for that. So all the light 309 00:14:01.879 --> 00:14:04.360 waves arrive at the central hub at the exact same 310 00:14:04.440 --> 00:14:05.759 instant to be combined to. 311 00:14:05.919 --> 00:14:08.960 Within a fraction of a wavelength of light. Yes, you 312 00:14:09.000 --> 00:14:14.639 have to compensate for everything, thermal expansion, seismic vibrations, atmospheric turbulence. 313 00:14:15.039 --> 00:14:17.200 It pushes engineering to its absolute limit. 314 00:14:17.960 --> 00:14:21.480 You mentioned LGO before the gravitational wave detector that's also 315 00:14:21.519 --> 00:14:23.759 on a kilometer scale. How is this different. 316 00:14:24.559 --> 00:14:27.120 It's a great comparison for the scale, but the function 317 00:14:27.360 --> 00:14:31.000 is totally different. LAGO isn't a telescope. It uses lasers 318 00:14:31.039 --> 00:14:34.200 inside its tunnels to measure the stretching of space time itself. 319 00:14:34.279 --> 00:14:36.519 It's detecting ripples in the fabric of the universe. 320 00:14:36.679 --> 00:14:40.879 Right this proposed interferometer would be a true telescope. It 321 00:14:40.879 --> 00:14:44.080 would be collecting faint starlight from distant objects using these 322 00:14:44.080 --> 00:14:47.399 separated mirrors. Its goal is to measure the position and 323 00:14:47.519 --> 00:14:51.240 movement of a physical object, not a distortion in space time. 324 00:14:51.480 --> 00:14:54.879 In an instrument this precise can't just scan the sky randomly. 325 00:14:55.080 --> 00:14:57.600 It would be incredibly inefficient. It needs a target. 326 00:14:57.320 --> 00:14:59.720 List, yes, and this is where the synergy with other 327 00:14:59.759 --> 00:15:03.759 p become so important. This interferometer isn't a discovery tool, 328 00:15:03.840 --> 00:15:06.480 it's a measurement tool. It needs a partner, and. 329 00:15:06.360 --> 00:15:09.559 That partner is the extremely large telescope, the ELT. 330 00:15:10.120 --> 00:15:12.919 The ELT it's under construction right now in Chile, set 331 00:15:12.919 --> 00:15:15.399 for completion around twenty twenty eight. It's going to have 332 00:15:15.440 --> 00:15:18.440 a thirty nine meters primary mirror, the biggest eye on 333 00:15:18.480 --> 00:15:19.879 the sky we've ever built, and. 334 00:15:19.840 --> 00:15:22.200 Its job is different. Its job is just to collect 335 00:15:22.240 --> 00:15:23.639 as much light as possible. 336 00:15:23.799 --> 00:15:26.240 Its job is to take the first direct pictures of 337 00:15:26.279 --> 00:15:30.080 these very faint, very distant gas giants, the ones orbiting 338 00:15:30.120 --> 00:15:32.000 far from their stars, the ones with the big hill 339 00:15:32.039 --> 00:15:34.960 spheres that we think are the best candidates for hosting moons. 340 00:15:35.279 --> 00:15:38.840 So the ELT finds the planets. It does the heavy 341 00:15:38.879 --> 00:15:41.559 lifting of identifying the targets. It says, okay, look over there, 342 00:15:41.600 --> 00:15:43.000 there's a promising gas giant. 343 00:15:43.440 --> 00:15:47.279 Precisely, and once the ELT gives us a target, this 344 00:15:47.519 --> 00:15:50.919 kilomer scale interferometer can then stare at that one planet. 345 00:15:51.200 --> 00:15:53.639 It doesn't waste time searching. It just locks on and 346 00:15:53.720 --> 00:15:55.759 monitors its position over months and. 347 00:15:55.759 --> 00:15:59.440 Years, watching for that tiny one micro arc second wobble. 348 00:15:59.600 --> 00:16:02.600 That's the tag team. The ELT is the spotter, the 349 00:16:02.600 --> 00:16:06.240 interferometer is the sniper. It's an incredibly efficient way to 350 00:16:06.279 --> 00:16:07.200 tackle the problem. 351 00:16:07.399 --> 00:16:09.200 So what does this all mean. We're talking about a 352 00:16:09.320 --> 00:16:14.080 multi billion dollar project, a decade of engineering to build 353 00:16:14.120 --> 00:16:19.600 this planetary wobble detector. Why yeah, White chase moons so 354 00:16:19.679 --> 00:16:21.159 hard when we have thousands of. 355 00:16:21.159 --> 00:16:25.159 Planets because exomoons might fundamentally change our search for life 356 00:16:25.159 --> 00:16:25.840 in the universe. 357 00:16:25.960 --> 00:16:27.799 It's about habitability, It's. 358 00:16:27.759 --> 00:16:32.360 About redefining what habitable even means it gives us a 359 00:16:32.399 --> 00:16:34.720 pathway to life that has almost nothing to do with 360 00:16:34.759 --> 00:16:36.360 the traditional Goldilocks zone. 361 00:16:36.440 --> 00:16:39.360 Okay, the Goldilock zone being that narrow band around a 362 00:16:39.399 --> 00:16:41.720 star where it's not too hot not too cold for 363 00:16:41.840 --> 00:16:43.919 liquid water to exist on a planet's surface. 364 00:16:44.080 --> 00:16:46.519 Right, it's all based on energy from the star. But 365 00:16:46.639 --> 00:16:50.039 for moons orbiting a gas giant, the star is almost irrelevant. 366 00:16:50.159 --> 00:16:52.639 They can be far outside the Goldilocks zone, in the 367 00:16:52.679 --> 00:16:55.639 frozen depths of their Solar system and still be habitable. 368 00:16:55.759 --> 00:16:57.200 And this is because of tidal heating. 369 00:16:57.279 --> 00:16:59.440 Tidle heating. It's the real game changer, and we see 370 00:16:59.480 --> 00:17:00.840 it right here in our own backyard. 371 00:17:00.960 --> 00:17:02.720 Europa and Enceladus our. 372 00:17:02.639 --> 00:17:06.000 Two most promising candidates for life beyond Earth. Europa at 373 00:17:06.079 --> 00:17:09.720 Jupiter and Seladus at Saturn. They are both ice worlds, 374 00:17:10.079 --> 00:17:13.720 far from the Sun's warmth. They should be frozen solid. 375 00:17:13.599 --> 00:17:16.720 But they're not. We're pretty sure they both have huge 376 00:17:16.920 --> 00:17:19.720 liquid water oceans beneath their ice shells. 377 00:17:19.319 --> 00:17:21.559 And that liquid water is kept warm not by the 378 00:17:21.559 --> 00:17:24.480 Sun but by the immense gravity of the planets they orbit. 379 00:17:24.599 --> 00:17:26.000 It's just gravity doing the heating. 380 00:17:26.119 --> 00:17:29.640 Think about the sheer mass of Jupiter as Europa orbits it, 381 00:17:29.759 --> 00:17:33.039 Jupiter's gravity is constantly pulling and stretching the little Moon. 382 00:17:33.759 --> 00:17:37.039 The side of Europa closest to Jupiter is pulled much harder. 383 00:17:36.799 --> 00:17:39.200 Than the far side, so the Moon is being flexed 384 00:17:39.279 --> 00:17:42.200 like squeezing a stress ball, over and over exactly. 385 00:17:42.839 --> 00:17:46.200 And that constant flexing and friction in its rocky core 386 00:17:46.720 --> 00:17:50.000 generates a tremendous amount of heat. It's like a planetary 387 00:17:50.039 --> 00:17:53.480 scale engine churning away in the Moon's interior, and that. 388 00:17:53.559 --> 00:17:56.920 Heat is what keeps those subsurface oceans liquid. 389 00:17:56.680 --> 00:17:59.279 For billions of years. It's a much more stable and 390 00:17:59.440 --> 00:18:02.680 long last energy source than the light from a distant star. 391 00:18:02.960 --> 00:18:06.759 It creates this tiny local habitable zone right around the 392 00:18:06.759 --> 00:18:07.759 gas giant itself. 393 00:18:07.880 --> 00:18:09.680 So if we find a big moon around a big 394 00:18:09.720 --> 00:18:12.519 exit planet, it could have liquid water, even if the 395 00:18:12.559 --> 00:18:14.519 whole system is in a deep freeze. 396 00:18:14.599 --> 00:18:17.440 It dramatically expands the amount of real estate in the 397 00:18:17.440 --> 00:18:20.039 galaxy where life could get a foothold. It tells us 398 00:18:20.039 --> 00:18:23.000 we should maybe stop looking for warm stars and start 399 00:18:23.039 --> 00:18:26.279 looking for massive, gravitationally active planets. 400 00:18:26.720 --> 00:18:29.480 Now, the paper is careful to include a reality check here. 401 00:18:30.000 --> 00:18:33.160