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 00:00:26.960 --> 00:00:30.559 We are starting today with a pretty cosmic mandate, really 8 00:00:30.760 --> 00:00:34.079 trying to find our closest earthlike neighbors out there. And 9 00:00:34.119 --> 00:00:36.640 for this deep dive, we're looking into the future of 10 00:00:36.679 --> 00:00:40.320 space explorations, specifically at the machine designed to do just that, 11 00:00:40.399 --> 00:00:43.679 the Habitable World's Observatory. You'll hear it called HWO. Now. 12 00:00:43.799 --> 00:00:47.359 HWO is slated to be the next great observatory, you know, 13 00:00:47.439 --> 00:00:50.359 following the footsteps of giants like Hubble and Web. But 14 00:00:50.399 --> 00:00:54.359 it has this incredibly specific central mission. It needs to 15 00:00:54.359 --> 00:00:58.000 analyze the atmospheres of at least twenty five exoplanets earth 16 00:00:58.159 --> 00:01:01.600 like ones, searching for biosignature basically signs of life. For 17 00:01:01.679 --> 00:01:03.920 a long time, the main strategy for HWO has really 18 00:01:04.000 --> 00:01:07.640 hinged on using an extremely powerful coronagraph that's well the 19 00:01:07.640 --> 00:01:10.200 specialized tool designed to block out the overwhelming light of 20 00:01:10.239 --> 00:01:12.640 a star so you can actually see hopefully the faint 21 00:01:12.640 --> 00:01:15.439 little planet orbiting next to it. But here's the snag. 22 00:01:15.599 --> 00:01:18.280 Finding twenty five worlds like that, especially when you don't 23 00:01:18.319 --> 00:01:20.200 even know for sure where most of them are hiding. 24 00:01:20.439 --> 00:01:22.000 That's a massive targeting problem. 25 00:01:22.200 --> 00:01:25.439 It absolutely is. It's an issue of well efficiency and 26 00:01:25.680 --> 00:01:28.920 just sheer astronomical legwork. You could waste so much time 27 00:01:28.959 --> 00:01:32.799 pointing at the wrong places, and that difficulty, that strategic 28 00:01:32.879 --> 00:01:35.599 challenge is exactly what Fibiu Malbad and his colleagues are 29 00:01:35.599 --> 00:01:39.079 tackling in some new research. They're proposing that hw needs 30 00:01:39.120 --> 00:01:42.519 a bit of an upgrade, really a powerful secondary instrument, 31 00:01:42.799 --> 00:01:47.159 one that could frankly revolutionize how HWO picks its targets 32 00:01:47.200 --> 00:01:50.879 for that crucial atmospheric analysis. Yeah, the big idea is 33 00:01:50.920 --> 00:01:54.319 adding a cutting edge, super high precision astrometry instrument to 34 00:01:54.480 --> 00:01:57.239 hwo's toolkit. And this isn't just like a minor tweak. 35 00:01:57.280 --> 00:02:00.400 It's a genuine leap in capability. If they do this, 36 00:02:00.400 --> 00:02:04.120 this instrument could potentially identify confirmed Earth sized planets orbiting 37 00:02:04.200 --> 00:02:06.920 hundreds of nearby stars. Think about that. It would instantly 38 00:02:06.920 --> 00:02:10.199 feed the HWO chronograph. This like perfectly curated list of 39 00:02:10.280 --> 00:02:11.000 prime targets. 40 00:02:11.080 --> 00:02:13.560 Okay, wow, let's unpack that straight away, because I mean 41 00:02:13.800 --> 00:02:16.479 the implications they are pretty stunning. So this add on 42 00:02:16.960 --> 00:02:20.680 dramatically boosts hwo's chances of hitting its main goal finding 43 00:02:20.719 --> 00:02:24.159 those biosignatures, obviously, but you're saying it also gives us 44 00:02:24.199 --> 00:02:28.680 this remarkable, almost separate scientific bonus that this incredibly precise 45 00:02:28.759 --> 00:02:32.240 planet hunter could actually double as a tool for cosmology, 46 00:02:32.599 --> 00:02:35.479 helping us map, maybe even solve, one of the biggest 47 00:02:35.560 --> 00:02:39.360 riddles out there, how cold dark matter CDM is spread 48 00:02:39.360 --> 00:02:40.439 out precisely. 49 00:02:40.479 --> 00:02:43.199 That's the unexpected twist. So for you listening, what we'll 50 00:02:43.240 --> 00:02:45.879 do in this dive is unpack the amazing tech precision 51 00:02:46.280 --> 00:02:48.159 needed for this. We're talking measurements down to half of 52 00:02:48.240 --> 00:02:51.680 micro arc second, just incredibly fine. We'll explore why that 53 00:02:51.759 --> 00:02:55.240 jump in sensitivity so critical, the kind of engineering tricks 54 00:02:55.240 --> 00:02:57.400 that might make it possible, and you know what discovering 55 00:02:57.400 --> 00:02:59.960 all these plans and potentially mapping dark matter could mean 56 00:03:00.159 --> 00:03:02.479 for understanding our place in the cosmos and the universe's 57 00:03:02.479 --> 00:03:03.159 basic structure. 58 00:03:03.240 --> 00:03:05.719 All right, let's start with HWO itself and its core 59 00:03:05.840 --> 00:03:10.120 job it's a biosignature hunter. Fundamentally, that means it needs 60 00:03:10.159 --> 00:03:13.120 to gather light from a planet potentially dozens of light 61 00:03:13.199 --> 00:03:16.159 years away, break that light down and look for the 62 00:03:16.240 --> 00:03:20.319 chemical fingerprints of things like oxygen, methane, water, vapor, things 63 00:03:20.319 --> 00:03:23.599 that could indicate life. And doing that takes a long time, 64 00:03:24.159 --> 00:03:26.919 hours and hours of telescope time focused on just one 65 00:03:27.000 --> 00:03:30.960 single target. So picking the right targets efficiently, that's everything. 66 00:03:30.719 --> 00:03:33.680 It really is. The coronagraph, as amazing as it is, 67 00:03:34.120 --> 00:03:36.960 needs good intel beforehand. It needs to know exactly where 68 00:03:36.960 --> 00:03:39.639 to point and ideally know the planet's orbit pretty well 69 00:03:39.680 --> 00:03:42.360 so it can track it effectively. And that leads us 70 00:03:42.439 --> 00:03:45.520 right into this, well, this significant gap in what we 71 00:03:45.560 --> 00:03:48.840 currently know about planets right here in our own stellar backyard. 72 00:03:49.199 --> 00:03:51.199 Just think about the stars within say sixty five light 73 00:03:51.280 --> 00:03:54.960 years of Earth. That's our immediate cosmic neighborhood, right These 74 00:03:55.000 --> 00:03:58.840 are prime candidates for HWO to look at. But of 75 00:03:58.919 --> 00:04:02.080 the sun like stars in that local bubble, we currently 76 00:04:02.159 --> 00:04:04.520 only know if planet's orbiting about twelve percent of them. 77 00:04:04.439 --> 00:04:06.400 Only twelve percent, And that low number isn't even the 78 00:04:06.400 --> 00:04:08.919 most critical part of the story, is it, No, not 79 00:04:09.000 --> 00:04:09.400 at all? 80 00:04:09.840 --> 00:04:12.360 The really crucial detail is the kind of planets we've 81 00:04:12.360 --> 00:04:16.000 found so far around those nearby stars. Every single one 82 00:04:16.040 --> 00:04:18.639 of the confirmed planets in that local sixty five light 83 00:04:18.680 --> 00:04:21.639 year zone is a gas giant. We're talking worlds like 84 00:04:21.720 --> 00:04:25.560 Jupiter or even bigger. As of today, we haven't confidently 85 00:04:25.600 --> 00:04:30.120 identified a single rocky Earth sized exoplanet orbiting a nearby 86 00:04:30.160 --> 00:04:30.879 Sun like star. 87 00:04:31.560 --> 00:04:34.120 Not one, right, So let me just make sure I'm 88 00:04:34.120 --> 00:04:37.160 getting the straight for everyone listening. In this huge volume 89 00:04:37.199 --> 00:04:39.920 of space right around us, a space where we assume 90 00:04:39.920 --> 00:04:44.000 there should be plenty of smaller rocky worlds, our best 91 00:04:44.040 --> 00:04:46.399 technology so far just hasn't been able to confirm any. 92 00:04:46.519 --> 00:04:47.720 It almost sounds wrong. 93 00:04:48.079 --> 00:04:51.160 It's purely a function of our instruments limitations, not necessarily 94 00:04:51.160 --> 00:04:53.519 a reflection of what's actually out there. It doesn't mean 95 00:04:53.519 --> 00:04:55.560 those Earth sized worlds aren't there. I mean all our 96 00:04:55.600 --> 00:04:58.439 theories of planet formation suggest they should be pretty common. Actually, 97 00:04:58.720 --> 00:05:00.759 it just means the signals they pretty, whether it's their 98 00:05:00.759 --> 00:05:03.959 reflected light or their gravitational tug, are currently getting drowned 99 00:05:03.959 --> 00:05:05.680 out by the noise. You know, if you're trying to 100 00:05:05.800 --> 00:05:08.560 spot a tiny firefly right next to a giant searchlight, 101 00:05:09.079 --> 00:05:11.759 your camera needs incredible contrast and stability. 102 00:05:12.040 --> 00:05:14.680 Same idea here, and that brings us squarely to this 103 00:05:14.800 --> 00:05:18.399 precision problem and the limits of our current best tool 104 00:05:18.519 --> 00:05:22.079 for this kind of work. The Gaya Space Observatory. Guy's 105 00:05:22.120 --> 00:05:25.360 been amazing for mapping stars in the Milky Way, absolutely revolutionary, 106 00:05:25.399 --> 00:05:29.199 but for finding these tiny earth like worlds nearby, it 107 00:05:29.319 --> 00:05:30.839 kind of hits a sensitivity wall. 108 00:05:31.120 --> 00:05:34.720 Guya really is the gold standard for current astrometry. It 109 00:05:34.720 --> 00:05:38.120 measures the positions and movements of stars with phenomenal accuracy, 110 00:05:38.560 --> 00:05:42.120 but its absolute best precision, its limit is around twenty 111 00:05:42.160 --> 00:05:44.720 to thirty micro arc seconds. We usually write that as ice. 112 00:05:44.920 --> 00:05:47.800 Okay, twenty or thirty micro arc seconds. That sounds incredibly 113 00:05:47.839 --> 00:05:50.399 tiny already. Why does that still fall short for finding 114 00:05:50.399 --> 00:05:53.279 an Earth? Twin? What's the physical scale here that we're missing? 115 00:05:53.519 --> 00:05:55.759 Well, to grasp the challenge, you need to visualize the 116 00:05:55.800 --> 00:05:59.639 star's actual movement. It's wobble. See when a planet orbits 117 00:05:59.639 --> 00:06:02.519 a star, they both actually orbit a common center of mass. 118 00:06:02.519 --> 00:06:05.959 It's called the Barry center. Now, a really massive planet 119 00:06:06.000 --> 00:06:08.759 like Jupiter makes our Sun move quite a bit, pulls 120 00:06:08.800 --> 00:06:10.680 the Sun around and a loop that's what about two 121 00:06:10.720 --> 00:06:14.399 million kilometers across even from sixty five light years away. 122 00:06:14.439 --> 00:06:17.879 That's a relatively large angular displacement on the sky. It's 123 00:06:17.879 --> 00:06:20.079 something Guy that can measure, and that's why Guy is 124 00:06:20.079 --> 00:06:23.800 great at finding gas giants. Okay, but now picture an 125 00:06:23.800 --> 00:06:26.600 Earth mass planet orbiting a sun like star. That tiny 126 00:06:26.639 --> 00:06:29.199 planet only makes it star wobble by maybe a few 127 00:06:29.199 --> 00:06:31.680 thousand kilometers let's say enter ten thousand kilometers over its 128 00:06:31.680 --> 00:06:34.959 whole orbit. Now translate that tiny physical movement into an 129 00:06:35.000 --> 00:06:37.360 angle on the sky as seen from sixty five light 130 00:06:37.439 --> 00:06:40.439 years away. That angular shift, the wobble we need to 131 00:06:40.439 --> 00:06:43.079 detect it works out to be less than one micro second. 132 00:06:43.240 --> 00:06:46.560 Ah. Okay, So Guya's best measurement twenty to thirty onens 133 00:06:46.639 --> 00:06:49.240 is just way too coarse. It's like trying to measure 134 00:06:49.519 --> 00:06:52.920 something a millimeter wide with a ruler marked only in centimeters. 135 00:06:53.120 --> 00:06:55.519 We're hunting for a wiggle that might be, say, thirty 136 00:06:55.560 --> 00:06:59.360 times smaller than the inherent error the noise level in 137 00:06:59.439 --> 00:07:00.519 our current best. 138 00:07:00.279 --> 00:07:03.720 Instruments exactly that twenty to thirty on's level is effectively 139 00:07:03.759 --> 00:07:06.800 the noise floor of today's technology for this specific task. 140 00:07:07.160 --> 00:07:10.720 And hiding beneath that noise floor we think are potentially 141 00:07:10.879 --> 00:07:14.360 hundreds of habitable Earth sized worlds right next door. So 142 00:07:14.720 --> 00:07:18.000 the only way to really enable hwo's primary mission to 143 00:07:18.000 --> 00:07:21.480 give it those targets is to dramatically, drastically lower that 144 00:07:21.600 --> 00:07:22.120 noise floor. 145 00:07:22.319 --> 00:07:24.879 Right. So, if the coronagraph is the tool for the 146 00:07:24.920 --> 00:07:29.079 deep dive, the detailed atmospheric sniffing, then astrometry, this wobble 147 00:07:29.120 --> 00:07:31.959 measuring technique sounds like the perfect tool for the initial 148 00:07:32.000 --> 00:07:34.839 survey for finding the worlds and figuring out their basic properties. First, 149 00:07:34.879 --> 00:07:37.279 can you give us a quick, clear definition of astrometry 150 00:07:37.279 --> 00:07:40.480 against specifically how it helps us find exoplanet sure? 151 00:07:40.720 --> 00:07:43.519 At its heart, astrometry is simply the science of measuring 152 00:07:43.560 --> 00:07:47.240 the precise positions and motions of stars over time very accurately. 153 00:07:47.920 --> 00:07:50.920 When we apply it to finding exoplanets, we're looking for 154 00:07:50.959 --> 00:07:54.959 that tiny, repetitive periodic shift in a star's parent position 155 00:07:55.040 --> 00:07:57.720 on the sky. That shift is caused by the gravitational 156 00:07:57.759 --> 00:08:00.480 pull of an orbiting planet tugging the star back and 157 00:08:00.519 --> 00:08:03.079 forth as they both orbit that common center of mass, 158 00:08:03.120 --> 00:08:06.120 the Barry Center. We're basically tracking the star's side of 159 00:08:06.120 --> 00:08:06.920 that orbital. 160 00:08:06.720 --> 00:08:08.879 Dance, and the beauty of it is the size of 161 00:08:08.879 --> 00:08:11.959 that wobble directly relates to the mass of the planet 162 00:08:12.000 --> 00:08:14.879 doing the tugging right, bigger wobble, bigger planet. 163 00:08:14.519 --> 00:08:17.800 Mass exactly right. And that's the huge advantage of astrometry 164 00:08:18.000 --> 00:08:21.600 because that gravitational relationship is so well understood based on physics. 165 00:08:22.160 --> 00:08:24.879 If you can measure that wobble with extremely high precision, 166 00:08:25.120 --> 00:08:29.199 you can calculate the exoplanet's entire orbital solution, its orbital period, 167 00:08:29.480 --> 00:08:31.959 how far it is from the star on average, a 168 00:08:32.039 --> 00:08:35.120 semi major axis, even how elliptical its orbit is. You 169 00:08:35.159 --> 00:08:37.440 basically get a complete map of its path, which tells 170 00:08:37.519 --> 00:08:39.919 you exactly where that planet will be at any given time. 171 00:08:40.159 --> 00:08:42.799 And that's absolutely critical for pointing the coronograph later on. 172 00:08:43.039 --> 00:08:46.000 Okay, so that's the practical benefit better targeting knowing where 173 00:08:46.000 --> 00:08:49.799 to look makes sense. But you also mention a fundamental 174 00:08:49.840 --> 00:08:53.840 scientific advantage, something that other main planet finding methods like 175 00:08:53.919 --> 00:08:57.480 the transit method or radial velocity can't quite deliver with 176 00:08:57.519 --> 00:08:58.320 the same certainty. 177 00:08:58.440 --> 00:09:02.080 Yes, and this is key. Astrometry allows you to determine 178 00:09:02.080 --> 00:09:04.840 the exo planet's absolute mass, not just a minimum mass, 179 00:09:04.879 --> 00:09:07.559 but it's actual mass. See the radio velocity method, which 180 00:09:07.559 --> 00:09:10.360 measures the stars wobble towards and away from us only 181 00:09:10.360 --> 00:09:12.840 gives you a minimum possible mass for the planet. That's 182 00:09:12.879 --> 00:09:15.159 because the signal depends on the tilt of the planet's 183 00:09:15.240 --> 00:09:17.759 orbit relative to our line of sight, and usually we 184 00:09:17.919 --> 00:09:22.120 don't know that tilt precisely. Astrometry, though, measures the side 185 00:09:22.159 --> 00:09:25.120 to side wobble on the sky. That measurement directly gives 186 00:09:25.120 --> 00:09:28.799 you the true, unambiguous mass of the planet. And why 187 00:09:28.919 --> 00:09:31.480 is knowing the true mass so important? We'll think about 188 00:09:31.600 --> 00:09:35.559 Hwo's goal finding life. To assess if a planet could 189 00:09:35.600 --> 00:09:38.159 host life, we first need to know if it's even rocky. Right. 190 00:09:38.480 --> 00:09:41.080 If you can combine that absolute mass from astrometry with 191 00:09:41.120 --> 00:09:43.639 the planet's radius, which you might get if you're lucky 192 00:09:43.639 --> 00:09:45.759 and the planet also happens to transit passing in front 193 00:09:45.759 --> 00:09:48.480 of it star from our view, then mass plus radius 194 00:09:48.519 --> 00:09:51.360 gives you density. And density is the killer metric. It's 195 00:09:51.399 --> 00:09:53.440 what fundamentally tells you if you're looking at a dense, 196 00:09:53.720 --> 00:09:56.840 rocky world like Earth or Venus, or a puffy, low 197 00:09:56.879 --> 00:10:00.639 density gas or ice giant like Jupiter or Neptune, which are, 198 00:10:00.799 --> 00:10:03.080 let's face it, much less likely places to find life 199 00:10:03.120 --> 00:10:06.919 as we know it. So astramistry provides that foundational piece 200 00:10:06.960 --> 00:10:08.600 of the puzzle for figuring out if the planet is 201 00:10:08.639 --> 00:10:10.559 even potentially habitable in the first place. 202 00:10:10.720 --> 00:10:12.720 Okay, so it all comes back to the main challenge 203 00:10:12.879 --> 00:10:16.159 getting sensitive enough to measure that incredibly tiny wobble from 204 00:10:16.159 --> 00:10:19.799 an Earth mass planet Gia. Our current best is stuck 205 00:10:19.840 --> 00:10:22.559 at around twenty thirty oins. What's the leap in precision 206 00:10:22.600 --> 00:10:25.279 that doctor Malbat's proposal is calling for. How much better 207 00:10:25.279 --> 00:10:26.000 do we need to be? 208 00:10:26.360 --> 00:10:29.720 The instrument they're suggesting aims for an operational precision of 209 00:10:30.960 --> 00:10:34.159 I get this zero point five micro arc seconds. 210 00:10:33.840 --> 00:10:36.240 Half of microrost. Wow. Okay, just comparing that to Gaya, 211 00:10:36.279 --> 00:10:38.240 which is already state of the area. You're talking about 212 00:10:38.440 --> 00:10:41.120 making this new instrument on EAHWO something like four hundred 213 00:10:41.159 --> 00:10:44.360 to six hundred times more sensitive than Guya. That's that's 214 00:10:44.360 --> 00:10:46.440 not just like the next step up. That's like skipping 215 00:10:46.480 --> 00:10:49.639 two whole generations of technology. It completely changes the game 216 00:10:49.679 --> 00:10:50.799 for hwo's mission. 217 00:10:51.159 --> 00:10:53.360 It really does. Just to give you a sense of scale, 218 00:10:53.399 --> 00:10:57.159 foer point five targets, that's roughly the angular size of 219 00:10:57.200 --> 00:11:00.639 a single human hair viewed from about five hundred miles away. 220 00:11:01.039 --> 00:11:04.000 It's an unbelievably fine measurement we're talking about making from 221 00:11:04.000 --> 00:11:07.320 space and achieving that level of sensitivity that point five 222 00:11:07.399 --> 00:11:11.440 tarrets is the absolute key. It's what unlocks potentially hundreds 223 00:11:11.480 --> 00:11:14.480 of new Exo Earth candidates right in our solar neighborhood. 224 00:11:14.840 --> 00:11:18.440 It means hwo's giant coronagraph doesn't have to waste precious 225 00:11:18.480 --> 00:11:22.200 time searching blindly or inefficiently. Instead, it gets handed this 226 00:11:22.360 --> 00:11:26.360 highly optimized, pre vetted list of confirmed targets, complete with 227 00:11:26.399 --> 00:11:29.480 their masses and orbital details, making it much much easier 228 00:11:29.480 --> 00:11:32.320 to efficiently tick off that primary mission goal finding those 229 00:11:32.360 --> 00:11:33.679 twenty five biosignatures. 230 00:11:33.879 --> 00:11:36.840 Okay, boosting precision by a factor of say four hundred 231 00:11:36.919 --> 00:11:38.600 or six hundred, that obviously means you have to overcome 232 00:11:38.639 --> 00:11:41.960 some equally huge technical challenges. If doing astronotry at point 233 00:11:42.000 --> 00:11:44.480 five highs was easy, presumably we'd have done it by now. 234 00:11:45.039 --> 00:11:47.799 So what's the main weakness? What makes these astrometers so 235 00:11:47.840 --> 00:11:49.320 prone to error that we need to fix? 236 00:11:49.600 --> 00:11:53.080 Well, even out in the relative stability of space, astronomers 237 00:11:53.080 --> 00:11:56.399 are inherently susceptible to what we call systematic errors. You're 238 00:11:56.440 --> 00:11:58.840 trying to measure an angular shift on the sky. That's 239 00:11:58.879 --> 00:12:02.240 smaller than the width of a virus. Right, So, every 240 00:12:02.399 --> 00:12:06.200 tiny physical imperfection in the instrument itself, whether it's in 241 00:12:06.240 --> 00:12:09.360 the detector chip, tiny misalignments in the mirrors, slight changes 242 00:12:09.440 --> 00:12:12.120 do to temperature, all these things can combine and create 243 00:12:12.200 --> 00:12:15.080 noise that swamps the signal you're looking for. The main 244 00:12:15.120 --> 00:12:19.000 offenders are usually imperfections in the detector and just thermal instability. 245 00:12:19.559 --> 00:12:22.679 The sensor, typically a CMOS chip like in your phone camera, 246 00:12:22.720 --> 00:12:27.000 but much more advanced, isn't mathematically perfect. The pixels aren't 247 00:12:27.000 --> 00:12:30.320 all identical squares. They have tiny variations and how sensitive 248 00:12:30.320 --> 00:12:33.440 they are, their exact size, their electrical behavior. That's due 249 00:12:33.480 --> 00:12:37.320 to the manufacturing process, and it's called fixed pattern noise. Now, 250 00:12:37.399 --> 00:12:41.399 if that sensor shifts even minutely relative to the incoming starlight, 251 00:12:41.840 --> 00:12:44.559 or if it's temperature fluctuates by even a tiny fraction 252 00:12:44.600 --> 00:12:47.919 of a degree, those built in imperfections create errors in 253 00:12:47.960 --> 00:12:51.279 your position measurement, and those errors very quickly add up 254 00:12:51.279 --> 00:12:54.559 and overwhelm the sub microarc second signal you're desperately trying 255 00:12:54.600 --> 00:12:58.159 to detect. That inherent instrumental noise floor is basically why 256 00:12:58.159 --> 00:13:00.440 we've been stuck around that twenty thirty oin limit for 257 00:13:00.480 --> 00:13:00.840 so long. 258 00:13:01.000 --> 00:13:03.360 Okay, So to break through that barrier and actually hit 259 00:13:03.559 --> 00:13:07.480 zero point five noise, Malvot's team is proposing a kind 260 00:13:07.519 --> 00:13:10.480 of two pronged attack, right, a strategy to cancel out 261 00:13:10.519 --> 00:13:14.639 both those predictable systematic errors from the hardware itself and 262 00:13:14.720 --> 00:13:19.559 also the unpredictable random noise from the environment. Let's start 263 00:13:19.559 --> 00:13:22.240 with the first part, the clever bit of technology, the 264 00:13:22.240 --> 00:13:25.080 detector calibration unit or DCU. What does that do? 265 00:13:25.440 --> 00:13:28.080 The DCU is a really neat piece of engineering. It's 266 00:13:28.120 --> 00:13:31.600 designed specifically to tackle that fixed pattern noise problem on 267 00:13:31.679 --> 00:13:34.679 the CMOS sensor head on. So you've got your sensor, 268 00:13:34.759 --> 00:13:37.759 which is basically this grid of millions of tiny light 269 00:13:37.840 --> 00:13:41.600 collecting pixels. The DCU generates a set of extremely precise, 270 00:13:41.840 --> 00:13:44.120 stable reference patterns, think of them like light and dark 271 00:13:44.159 --> 00:13:47.559 interference fringes, or a super high resolution grid pattern, and 272 00:13:47.639 --> 00:13:50.200 it projects these known patterns directly onto the face of 273 00:13:50.200 --> 00:13:52.639 the CMO sensor itself while you're observing. 274 00:13:52.720 --> 00:13:56.320 Ah. Okay, so it's like shining a perfect unchanging calibration 275 00:13:56.480 --> 00:13:58.799 ruler directly onto the detector every time you take a 276 00:13:58.799 --> 00:13:59.720 picture exactly. 277 00:13:59.799 --> 00:14:02.720 That's a great analogy the DCU allows the system to 278 00:14:02.759 --> 00:14:06.679 isolate and map the precise physical location and the specific 279 00:14:06.759 --> 00:14:10.559 response characteristics of every single pixel in that detector array. 280 00:14:11.200 --> 00:14:14.000 And this calibration isn't just done once. It's done constantly 281 00:14:14.159 --> 00:14:17.480 or very frequently. It effectively corrects for all those tiny 282 00:14:17.480 --> 00:14:21.559 pixel to pixel variations, any slight geometric distortions introduced by 283 00:14:21.600 --> 00:14:25.159 the telescope's optics, and even tiny changes in the detector's 284 00:14:25.159 --> 00:14:28.840 own internal shape or geometry caused by minute thermal expansions 285 00:14:28.919 --> 00:14:32.399 or vibrations. What it does basically is create a perfectly 286 00:14:32.440 --> 00:14:36.159 stable internal coordinate system right on the detector itself, so 287 00:14:36.200 --> 00:14:38.279 when the light from the target star hits that sensor, 288 00:14:38.559 --> 00:14:41.480 the DCU calibration ensures that any measured shift in the 289 00:14:41.480 --> 00:14:44.519 star's apparent position is a real angular movement due to 290 00:14:44.519 --> 00:14:48.000 its gravitational wobble, and not just some artifact caused by 291 00:14:48.039 --> 00:14:50.039 the telescope hardware warming up by a thousandth of a 292 00:14:50.080 --> 00:14:52.840 degree or a pixel behaving slightly differently than its neighbor. 293 00:14:53.240 --> 00:14:56.039 It aims to drive that systematic air contribution down to 294 00:14:56.120 --> 00:14:56.960 almost zero. 295 00:14:57.159 --> 00:14:59.840 Okay, that sounds like it tackles the predictable flaws in 296 00:14:59.840 --> 00:15:03.360 the hardware pretty effectively. But even with a perfect DCU, 297 00:15:03.440 --> 00:15:06.600 you're still going to have some residual fuzziness, right, random 298 00:15:06.720 --> 00:15:09.840 errors from things like stray background light, maybe a cosmic 299 00:15:09.919 --> 00:15:13.639 ray hitting the detector, tiny thermal jitters. So this requires 300 00:15:13.720 --> 00:15:17.799 the second ingredient in the recipe, basically statistical brute force. 301 00:15:17.840 --> 00:15:19.240 You need lots and lots of data. 302 00:15:19.279 --> 00:15:21.279 You need a massive amount of data. The estimate they 303 00:15:21.279 --> 00:15:24.519 provide to the paper suggests that to really nail down 304 00:15:24.559 --> 00:15:27.679 the conformation of an Earth mass planet and to average 305 00:15:27.720 --> 00:15:31.120 down all those random errors to achieve that overall zero 306 00:15:31.120 --> 00:15:35.159 point five arrow precision goal, HWO would probably need to 307 00:15:35.159 --> 00:15:38.519 collect over one hundred separate high precision measurements of that 308 00:15:38.559 --> 00:15:39.759 particular star system. 309 00:15:39.799 --> 00:15:42.519 And these aren't just one hundred snapshots taken one after another. 310 00:15:42.559 --> 00:15:44.480 I assume you need to spread them out over time 311 00:15:44.559 --> 00:15:46.799 to actually see the orbit absolutely correct. 312 00:15:47.039 --> 00:15:50.200 These hundred plus measurements would need to be distributed over 313 00:15:50.240 --> 00:15:54.240 the course of hwo's planned operational lifetime, which is typically 314 00:15:54.279 --> 00:15:57.600 expected to be around three to four years. You need 315 00:15:57.600 --> 00:16:00.480 that longtime baseline to actually track this are through a 316 00:16:00.519 --> 00:16:03.759 significant portion, ideally more than one full cycle of its 317 00:16:03.799 --> 00:16:07.240 gravitational wobble caused by the planet. That's how you confirm 318 00:16:07.279 --> 00:16:10.200 the orbital period accurately, and the reason for needing so 319 00:16:10.200 --> 00:16:13.840 many images. The statistics part is pretty straightforward. Even the 320 00:16:13.879 --> 00:16:18.159 brilliant DCU can't stop every single random, unpredictable error. A 321 00:16:18.240 --> 00:16:22.240 stray photon here, a tiny vibration there. These are stochastic events. 322 00:16:22.679 --> 00:16:24.399 But the magic happens when you take a hundred or 323 00:16:24.440 --> 00:16:27.159 maybe one hundred and fifty of these individual measurements. The 324 00:16:27.200 --> 00:16:29.879 central limit theorem from statistics starts to work in your favor. 325 00:16:30.279 --> 00:16:34.279 Random errors are by definition random. They scatter. So if 326 00:16:34.279 --> 00:16:36.519 what measurement happens to have a random error that nudges 327 00:16:36.559 --> 00:16:39.639 the stars measure positions slightly to the north, it's likely 328 00:16:39.679 --> 00:16:42.200 that another measurement taken later will have a roughly equal 329 00:16:42.240 --> 00:16:45.120 and opposite random error that nudges the position slightly to 330 00:16:45.159 --> 00:16:46.000 the south right. 331 00:16:46.080 --> 00:16:49.639 So by combining and averaging all those hundreds of measurements together, 332 00:16:50.159 --> 00:16:53.240 you effectively force those random plus and minus errors to 333 00:16:53.279 --> 00:16:56.840 statistically cancel each other out over the long run, leaving 334 00:16:56.840 --> 00:17:02.240 behind only the consistent underlying signal that tiny, stable, repeatable 335 00:17:02.279 --> 00:17:05.200 gravitational wobble of the star caused by the planet. 336 00:17:05.359 --> 00:17:09.000 That's exactly the rationale. It's this combination, this marriage of 337 00:17:09.160 --> 00:17:13.920 highly sophisticated real time technical calibration that's the DCU with 338 00:17:14.000 --> 00:17:17.359 the sheer power of statistical averaging from taking lots and 339 00:17:17.400 --> 00:17:20.599 lots of pictures that gives us confidence we can actually 340 00:17:20.599 --> 00:17:24.680 stabilize the final result down to that incredibly demanding zero 341 00:17:24.680 --> 00:17:28.079 point five a's of precision level. It transforms a mission 342 00:17:28.160 --> 00:17:32.119 initially conceived around just a coronagraph into potentially the definitive 343 00:17:32.119 --> 00:17:34.440 surveyor of nearby planetary masses as well. 344 00:17:34.480 --> 00:17:36.599 Okay, now we pivot to the part that for me, 345 00:17:36.799 --> 00:17:39.440 really elevates this whole proposal. It goes beyond just making 346 00:17:39.559 --> 00:17:42.240 HWO better at its main job. The idea that an 347 00:17:42.279 --> 00:17:44.880 instrument fine tuned to measure a star wobbling by just 348 00:17:44.880 --> 00:17:47.519 a few thousand kilometers could also give us real leverage 349 00:17:47.559 --> 00:17:50.680 on one of the universe's biggest mysteries, cold dark matter. 350 00:17:50.799 --> 00:17:51.680 That's pretty amazing. 351 00:17:51.960 --> 00:17:55.000 It is a truly remarkable example of how pushing the 352 00:17:55.039 --> 00:17:59.599 technological envelope in one area of science can suddenly unexpectedly 353 00:17:59.759 --> 00:18:02.960 on block brand new capabilities in a completely different field. 354 00:18:04.079 --> 00:18:07.920 Hwo's proposed astrometer if built to this point five and 355 00:18:08.160 --> 00:18:12.599 spec could provide crucial observational data to directly test the 356 00:18:12.640 --> 00:18:16.119 standard model of cold dark matter. Specifically, it could help 357 00:18:16.160 --> 00:18:18.720 resolve a long standing puzzle about how dark matter is 358 00:18:18.759 --> 00:18:21.200 actually distributed right in the centers of galaxies. 359 00:18:21.440 --> 00:18:24.559 Right, and this gets into the famous cusp versus core debate, 360 00:18:24.599 --> 00:18:27.240 doesn't it? If dark matter is cold, meaning it moves 361 00:18:27.279 --> 00:18:30.880 slowly and mostly non interacting except through gravity, which is 362 00:18:30.920 --> 00:18:34.200 the standard CDM picture, what should happen to it near 363 00:18:34.240 --> 00:18:36.960 the super dense center of a galaxy? What does theory predict? 364 00:18:37.079 --> 00:18:39.960 The standard CDM theory is pretty unequivocal on this. It 365 00:18:39.960 --> 00:18:43.200 should form a cusp because dark matter particles in this 366 00:18:43.319 --> 00:18:46.160 model only really feel gravity. They should just keep getting 367 00:18:46.160 --> 00:18:49.799 pulled deeper and deeper into the galaxies gravitational Well, this 368 00:18:49.880 --> 00:18:52.799 process should cause the density of dark matter to continuously 369 00:18:52.839 --> 00:18:55.759 increase the closer you get to the very center, creating 370 00:18:55.759 --> 00:18:58.960 a really steep, sharp spike in density right at the core, 371 00:18:59.279 --> 00:19:00.000 like a pointy cut. 372 00:19:00.519 --> 00:19:04.440 Okay, so theory predicts this sharp density peak, But what 373 00:19:04.559 --> 00:19:08.240 do our observations actually show us, Especially when we look 374 00:19:08.279 --> 00:19:11.079 at smaller dwarf galaxies where the dark matter signal is 375 00:19:11.119 --> 00:19:13.839 often clearer, less mixed up with normal matter. 376 00:19:14.000 --> 00:19:18.319 Well, that's where the tension arises. Observations, particularly from studying 377 00:19:18.359 --> 00:19:21.400 how stars orbit in the outer parts of galaxies, and 378 00:19:21.519 --> 00:19:26.440 especially in these smaller dwarf galaxies, they frequently suggest something different. 379 00:19:27.079 --> 00:19:30.200 The data often indicates that the dark matter density profile 380 00:19:30.279 --> 00:19:33.240 tends to flatten out in the very center. Instead of 381 00:19:33.240 --> 00:19:36.519 that sharp cusp, we seem to see a core, basically 382 00:19:36.720 --> 00:19:39.279 a region where the dark matter density is more or 383 00:19:39.359 --> 00:19:42.119 less constant, or at least doesn't spike up dramatically right 384 00:19:42.119 --> 00:19:43.000 at the galactic heart. 385 00:19:43.640 --> 00:19:46.839 So theory predicts a steep point. Observation suggests more of 386 00:19:46.880 --> 00:19:49.799 a flat plateau in the middle. That's a pretty significant disagreement, 387 00:19:50.319 --> 00:19:53.160 and the existence of these apparent cores implies something's going 388 00:19:53.200 --> 00:19:55.799 on that isn't in the simplest CDM model right. Either 389 00:19:55.839 --> 00:19:58.559 are assumptions about dark matter or wrong, or something else 390 00:19:58.640 --> 00:20:00.839 is messing with its distribution exactly. 391 00:20:01.240 --> 00:20:04.119 These cores are real and common. It means something must 392 00:20:04.160 --> 00:20:06.400 be acting to sort of smooth out or push that 393 00:20:06.519 --> 00:20:09.799 dark matter away from the very center. What could it be, Well, 394 00:20:09.839 --> 00:20:13.599 one possibility is astrophysical feedback from normal matter things like 395 00:20:13.960 --> 00:20:18.279 massive bursts of star formation and powerful supernova explosions. These 396 00:20:18.279 --> 00:20:21.960 events can violently expel gas and energy, potentially pushing the 397 00:20:22.000 --> 00:20:25.559 dark matter outwards too, dynamically creating a core over time. 398 00:20:26.240 --> 00:20:29.279 Or maybe point to something fundamental about the dark matter 399 00:20:29.319 --> 00:20:33.720 particles themselves. Perhaps dark matter isn't completely non interacting. Maybe 400 00:20:33.720 --> 00:20:37.400 it's self interacting dark matter or SIDM, where dark matter 401 00:20:37.440 --> 00:20:40.480