WEBVTT 1 00:00:03.439 --> 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 Astronomy 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 00:00:26.920 --> 00:00:30.239 Welcome back to the show. Today, we are we're going 8 00:00:30.280 --> 00:00:32.679 to fundamentally change the way you look at the sky. 9 00:00:32.920 --> 00:00:36.320 Yeah, literally, the actual physical sky you see every day. 10 00:00:36.200 --> 00:00:37.640 Right, And I don't mean that in you know, some 11 00:00:37.759 --> 00:00:40.600 kind of metaphorical reach for the stars kind of way. 12 00:00:40.640 --> 00:00:43.560 I mean literally, we are talking about the Sun, the. 13 00:00:43.560 --> 00:00:46.119 Sun skull, our local. 14 00:00:45.840 --> 00:00:49.600 Star, right. And I know the immediate reaction might be, Okay, 15 00:00:49.640 --> 00:00:52.520 the Sun. It's big, it's hot, it rises in the east, 16 00:00:52.560 --> 00:00:54.679 sets in the west, and if I stare at it. 17 00:00:54.759 --> 00:00:56.719 I go blind, which you should not do. 18 00:00:56.960 --> 00:00:59.719 No, absolutely do not do that. But we tend to 19 00:00:59.719 --> 00:01:01.679 take it for granted. I think it's just it's the 20 00:01:01.679 --> 00:01:05.239 background lighting for our lives. But in the world of astronomy, 21 00:01:05.280 --> 00:01:08.680 the sun isn't just a light bulb. It is a key, 22 00:01:09.280 --> 00:01:12.400 like a literal skeleton key that unlocks the physics of 23 00:01:12.439 --> 00:01:14.079 the entire universe. It really is. 24 00:01:14.120 --> 00:01:16.599 It's the Rosetta stone of astronomy. That's really the core 25 00:01:16.680 --> 00:01:19.480 concept we are unpacking today for you. It's the only 26 00:01:19.480 --> 00:01:21.959 star in the universe that doesn't look like a dot. 27 00:01:22.120 --> 00:01:24.359 Yeah, and we have a massive stack of research to 28 00:01:24.400 --> 00:01:27.560 get through today. This is primarily centering on a major 29 00:01:27.640 --> 00:01:31.719 review paper by Shintoriomi and his colleagues, and the mission 30 00:01:31.719 --> 00:01:35.120 of this exploration today is to understand how scientists are 31 00:01:35.200 --> 00:01:38.719 using our Sun, the only star we can actually see 32 00:01:38.760 --> 00:01:42.879 in high definition, to decode the blurry, pixelated signals we 33 00:01:42.959 --> 00:01:45.120 get from every other star in the galaxy. 34 00:01:45.400 --> 00:01:48.840 Exactly. It's really about bridging the gap between solar physics, 35 00:01:48.879 --> 00:01:52.359 which is the study of our specific star, and stellar physics, 36 00:01:52.359 --> 00:01:55.519 which is the study of all those other points of light. Historically, 37 00:01:55.560 --> 00:01:58.879 these have been two totally separate fields, but now they 38 00:01:58.879 --> 00:01:59.439 are emerging. 39 00:02:00.040 --> 00:02:01.879 So let's start with the big picture. You mentioned the 40 00:02:02.439 --> 00:02:05.200 problem of distance earlier when we were chatting. I think 41 00:02:05.200 --> 00:02:07.439 we need to really settle into this idea to understand 42 00:02:07.439 --> 00:02:09.080 why this research is so crucial. 43 00:02:09.800 --> 00:02:11.560 Think about this when you look up at the night 44 00:02:11.599 --> 00:02:14.159 sky or even when we use our most powerful tools, 45 00:02:14.199 --> 00:02:16.759 you know the James Web Space Telescope, PUBBLE, those massive 46 00:02:16.759 --> 00:02:20.039 ground based observatories down in Chile. What do we actually 47 00:02:20.080 --> 00:02:21.240 see when we look at a star? 48 00:02:21.479 --> 00:02:23.879 I mean, even with the best zoom lenses in human history, 49 00:02:23.960 --> 00:02:25.080 we basically just see a. 50 00:02:25.039 --> 00:02:28.280 Dot, a pixel precisely, we call it a point source. 51 00:02:28.879 --> 00:02:31.240 We can analyze the light coming from that point. We 52 00:02:31.280 --> 00:02:33.080 can break it into a spectrum to see what it's 53 00:02:33.120 --> 00:02:35.599 made of. We can measure if it gets brighter or 54 00:02:35.599 --> 00:02:38.719 dimmer over time. But we cannot resolve the surface. We 55 00:02:38.759 --> 00:02:40.639 can't see the geography. 56 00:02:40.159 --> 00:02:41.800 The actual physical features, right. 57 00:02:41.879 --> 00:02:43.960 We can't see the storms. We can't see the sun 58 00:02:44.000 --> 00:02:46.759 spots or the flares directly. It is just a single 59 00:02:46.800 --> 00:02:50.439 pixel of data that contains all that information just meshed together. 60 00:02:50.840 --> 00:02:53.520 It's like it's like trying to understand the complexity of 61 00:02:53.560 --> 00:02:56.159 New York City by looking at a single light bulb 62 00:02:56.199 --> 00:02:57.960 on the Empire State building from space. 63 00:02:58.319 --> 00:03:00.919 That's great analogy. Now can we hear that to the sun? 64 00:03:01.080 --> 00:03:03.800 The Sun is close, we can see its eyelashes. Practically, 65 00:03:04.039 --> 00:03:06.599 we can see sun spots the size of Earth. We 66 00:03:06.639 --> 00:03:10.560 can see giant loops of magnetic plasma arching over the surface. 67 00:03:10.879 --> 00:03:13.199 We can see solar flares exploding in real time. 68 00:03:13.280 --> 00:03:15.960 It's basically high definition four K video of the Sun's surface. 69 00:03:16.120 --> 00:03:19.280 Yeah, exactly. So the Rosetta Stone analogy here is all about. 70 00:03:19.080 --> 00:03:22.639 Translation, right, because the original Zetta Stone allowed us to 71 00:03:22.719 --> 00:03:27.520 translate Egyptian hieroglyphs, which were a total mystery because we 72 00:03:27.560 --> 00:03:29.919 had the exact same text written in Greek, which we 73 00:03:29.919 --> 00:03:31.280 already understood exactly. 74 00:03:31.360 --> 00:03:34.080 The Sun is our Greek text. We know what the 75 00:03:34.120 --> 00:03:36.599 Sun looks like up close. We understand the physics of 76 00:03:36.639 --> 00:03:39.360 the surface because we can actually see it happening. 77 00:03:39.479 --> 00:03:41.120 And the higherglyphs are the distant stars. 78 00:03:41.439 --> 00:03:44.439 Right. We take the hdview of our Sun and we 79 00:03:44.479 --> 00:03:47.639 mathematically downgrade it. We blur it on purpose. We turn 80 00:03:47.680 --> 00:03:50.199 our Sun into a single pixel to see what it 81 00:03:50.199 --> 00:03:52.599 would look like if it were, you know, fifty light 82 00:03:52.639 --> 00:03:53.159 years away. 83 00:03:53.360 --> 00:03:53.759 Oh wow. 84 00:03:53.960 --> 00:03:57.560 Yeah, And by comparing the HD version, what we absolutely 85 00:03:57.599 --> 00:04:00.120 know is happening with the pixel version the signal we 86 00:04:00.159 --> 00:04:03.039 would receive. We learn how to read the signals from 87 00:04:03.039 --> 00:04:03.639 other stars. 88 00:04:03.919 --> 00:04:07.000 That is incredibly cool. We are basically training ourselves on 89 00:04:07.080 --> 00:04:10.120 the Sun so we can play detective with stars that 90 00:04:10.159 --> 00:04:12.680 are hundreds of light years away. We're building a dictionary 91 00:04:12.680 --> 00:04:13.680 of stellar signals. 92 00:04:13.759 --> 00:04:16.560 That is exactly it. And the primary tool for this 93 00:04:16.639 --> 00:04:20.920 investigation are magnifying glass if you will, is a spacecraft 94 00:04:20.959 --> 00:04:22.680 called the SDO. 95 00:04:22.240 --> 00:04:24.959 NASA's Solar Dynamics Observatory. 96 00:04:24.519 --> 00:04:28.279 Yes, launch back in twenty ten. And before we get 97 00:04:28.319 --> 00:04:30.279 into the actual results, I think we really need to 98 00:04:30.279 --> 00:04:34.480 pause on the SDO itself because calling it a camera feels, well, 99 00:04:34.519 --> 00:04:36.079 it feels like a bit of an insult to the 100 00:04:36.120 --> 00:04:37.000 engineering involved. 101 00:04:37.079 --> 00:04:39.519 I agree completely. Reading the specs on this thing, it's 102 00:04:39.560 --> 00:04:42.920 an absolute beast. It's not just taking snapshots for Instagram. 103 00:04:43.240 --> 00:04:48.480 It's a suite of three very specific, very sophisticated instruments. 104 00:04:48.560 --> 00:04:51.079 It's like having an X ray machine, an MRI, and 105 00:04:51.160 --> 00:04:55.079 a thermal camera all pointed at the exact same patient simultaneously. 106 00:04:55.279 --> 00:04:57.079 It sees the Sun in layers. 107 00:04:57.199 --> 00:04:59.560 Okay, let's break down these eyes of the SDO for 108 00:04:59.639 --> 00:05:02.879 beginning who might not be familiar, because understanding how they 109 00:05:02.959 --> 00:05:05.519 see is crucial to understand the data we're going to 110 00:05:05.519 --> 00:05:08.319 discuss later. So the first one is called HMI. 111 00:05:08.319 --> 00:05:11.759 Right, the Helioseismic and Magnetic Imager. This is the heavy lifter. 112 00:05:12.000 --> 00:05:13.720 It's not looking at light in the way your film 113 00:05:13.800 --> 00:05:16.920 camera does. It's specifically measuring the magnetic field at the 114 00:05:16.959 --> 00:05:17.759 solar surface. 115 00:05:18.040 --> 00:05:20.399 Now this brings us to the actual physics of it all. 116 00:05:20.759 --> 00:05:23.319 How do you take a picture of magnetic field? Because 117 00:05:23.319 --> 00:05:25.439 magnetic fields are invisible. 118 00:05:25.079 --> 00:05:27.639 Right, They are invisible to the naked eye, Yes, but 119 00:05:27.720 --> 00:05:30.839 they leave a very specific fingerprint on light. It's called 120 00:05:30.839 --> 00:05:31.720 the Zeman effect. 121 00:05:31.959 --> 00:05:33.920 Zeman effect. Okay, let's unpack that for everyone. 122 00:05:34.000 --> 00:05:36.879 Sure, Imagine you were looking at a specific color of 123 00:05:36.959 --> 00:05:39.839 light emitted by an iron atom on the sun, a 124 00:05:39.879 --> 00:05:43.240 spectral line. If that iron atom is just sitting there 125 00:05:43.399 --> 00:05:47.560 in a calm, quiet region, that line is sharp and singular. 126 00:05:47.639 --> 00:05:50.480 It's just one line, okay. But if you place that 127 00:05:50.560 --> 00:05:53.920 iron atom inside a strong magnetic field, like inside a 128 00:05:53.959 --> 00:05:58.000 sun spot, that single line splits. It literally divides into 129 00:05:58.040 --> 00:05:59.160 three distinct lines. 130 00:05:59.319 --> 00:06:01.120 It actually flits the light itself. 131 00:06:01.199 --> 00:06:03.920 It splits. The energy levels of the electrons in the 132 00:06:03.959 --> 00:06:06.879 atom are physically shifted by the magnetic field, and the 133 00:06:06.959 --> 00:06:09.480 amount of splitting how far apart those new lines are 134 00:06:09.639 --> 00:06:11.639 tells you exactly how strong the magnet is. 135 00:06:11.879 --> 00:06:14.800 So the HMI instrument is scanning the entire face of 136 00:06:14.839 --> 00:06:17.639 the Sun millions of times a day looking for this 137 00:06:17.800 --> 00:06:19.480 tiny microscopic splitting of. 138 00:06:19.560 --> 00:06:22.920 Light exactly, and by mapping that splitting, it creates what 139 00:06:22.959 --> 00:06:26.000 we call a magnetogram. It's basically a topographic map of 140 00:06:26.000 --> 00:06:27.959 the magnetic forces churning on the surface. 141 00:06:28.279 --> 00:06:31.920 That's the engine room. Because as we know, magnetism drives 142 00:06:31.959 --> 00:06:33.279 pretty much everything on the Sun. 143 00:06:33.519 --> 00:06:36.920 It is the puppet master everything interesting, the flares, the spots, 144 00:06:36.920 --> 00:06:40.040 the giant eruptions, It all starts with the magnetic field 145 00:06:40.120 --> 00:06:43.240 twisting and snapping. HMI gives us the map of those 146 00:06:43.240 --> 00:06:43.959 puppet strings. 147 00:06:44.000 --> 00:06:45.800 Okay, so that's the magnetic map. Then we have the 148 00:06:45.800 --> 00:06:48.959 glamour shots. The instrument called AIA. 149 00:06:48.759 --> 00:06:53.160 The atmospheric Imaging assembly. When you see those stunning golden, 150 00:06:53.319 --> 00:06:56.839 swirling videos of the Sun on the news or in documentaries, 151 00:06:57.240 --> 00:06:59.720 the ones that look like a living, breathing. 152 00:06:59.439 --> 00:07:01.839 Ball of yeah, the ones that make you suddenly realize 153 00:07:01.879 --> 00:07:03.639 the Sun is actually a terrifying object. 154 00:07:03.759 --> 00:07:07.560 Yeah, that is AIA data. But again, it's not just 155 00:07:07.600 --> 00:07:11.399 a standard camera taking a color photo. It specifically filters 156 00:07:11.480 --> 00:07:13.600 light to look at extreme temperatures. 157 00:07:13.759 --> 00:07:16.079 This is the part that fascinated me in the Toriomi paper. 158 00:07:16.279 --> 00:07:18.439 It's not looking at colors like red or blue. 159 00:07:18.560 --> 00:07:21.439 It's looking at ionization, states right, it looks at extreme 160 00:07:21.560 --> 00:07:26.040 ultraviolet light. At these insane temperatures, atoms literally get stripped 161 00:07:26.079 --> 00:07:29.879 of their electrons. We call this ionization. So AIA has 162 00:07:29.920 --> 00:07:32.439 a filter that only lets in light from iron atoms 163 00:07:32.439 --> 00:07:35.079 that have lost say eight electrons. 164 00:07:34.720 --> 00:07:39.000 And that specific loss only happens at a specific temperature exactly. 165 00:07:39.439 --> 00:07:42.800 Iron nine, which is iron that has lost eight electrons, 166 00:07:42.800 --> 00:07:46.399 glows brightest at about six hundred thousand degrees, but iron 167 00:07:46.439 --> 00:07:49.800 eighteen might glow at six million degrees. So by mechanically 168 00:07:49.800 --> 00:07:53.560 switching filters, the AIA can basically peel the onion. It 169 00:07:53.560 --> 00:07:56.560 can say, show me only the gas that is exactly 170 00:07:56.680 --> 00:08:00.319 one million degrees, and suddenly you see specific lou and 171 00:08:00.360 --> 00:08:03.319 structures that are completely invisible at other temperatures. 172 00:08:03.600 --> 00:08:05.879 So we have the magnetic map from HMI and the 173 00:08:05.920 --> 00:08:09.959 temperature sliced atmosphere from AIA. And the third one is EVE, the. 174 00:08:10.000 --> 00:08:14.160 Extreme Ultraviolet Variability Experiment. Unlike the other two, EVE isn't 175 00:08:14.199 --> 00:08:16.560 taking a picture at all. It's an irradiance sensor. It 176 00:08:16.560 --> 00:08:18.160 measures the total energy output. 177 00:08:18.199 --> 00:08:20.160 So it's a giant light meter, a very. 178 00:08:20.079 --> 00:08:22.519 Very fancy light meter. It tells us exactly how much 179 00:08:22.639 --> 00:08:24.920 energy the Sun is screaming out into the Solar system 180 00:08:24.959 --> 00:08:28.439 at any given second across the entire UV spectrum. 181 00:08:28.519 --> 00:08:31.439 So putting it all together for you listening, HMI shows 182 00:08:31.519 --> 00:08:34.440 us the cause, which is magnetism, AIA shows us the 183 00:08:34.440 --> 00:08:37.240 structure of the atmosphere itself, and Eve shows us the output, 184 00:08:37.279 --> 00:08:39.320 the actual energy hitting us correct. 185 00:08:39.519 --> 00:08:42.799 And here is why SDO is the absolute foundation of 186 00:08:42.840 --> 00:08:46.039 this Rosetta Stone project. It has been staring at the 187 00:08:46.039 --> 00:08:49.039 Sun twenty four to seven for well over a decade. 188 00:08:49.120 --> 00:08:50.120 It never blinks. 189 00:08:50.559 --> 00:08:52.559 That is a staggering amount of data. 190 00:08:52.679 --> 00:08:56.200 It's massive, and crucially, it covers a full solar cycle 191 00:08:56.399 --> 00:09:00.200 the Sun breathes. Essentially, it has solar maximum where it 192 00:09:00.240 --> 00:09:03.879 is angry, covered in spots and constantly flaring, and it 193 00:09:03.879 --> 00:09:07.200 has a solar minimum where it is very quiet and 194 00:09:07.360 --> 00:09:11.919 virtually blank. SDO captured the entire transition from quiet to 195 00:09:12.200 --> 00:09:13.759 angry and back again. 196 00:09:13.559 --> 00:09:16.159 So we have a complete baseline. We noted chill star 197 00:09:16.240 --> 00:09:18.679 looks like, and we know what a raging star looks 198 00:09:18.720 --> 00:09:20.080 like in high definition. 199 00:09:19.879 --> 00:09:23.039 Exactly, and that leads us directly to the core methodology 200 00:09:23.039 --> 00:09:25.360 of the paper. They call it the Sun is a star. Experiment. 201 00:09:25.519 --> 00:09:28.080 This is the reverse engineering part. Walk us through how 202 00:09:28.080 --> 00:09:29.799 they actually perform this experiment. 203 00:09:29.960 --> 00:09:33.360 It's a brilliant synthesis of data. They take those incredible 204 00:09:33.399 --> 00:09:35.960 high resolution images from SDO where you can see the 205 00:09:35.960 --> 00:09:39.000 sun spots and the loops perfectly clearly, and they deliberately 206 00:09:39.080 --> 00:09:39.559 ruin them. 207 00:09:39.600 --> 00:09:41.039 They ruin them like blur them out. 208 00:09:41.159 --> 00:09:43.879 They integrate them. They sum up all the light from 209 00:09:43.919 --> 00:09:47.639 the entire disc into a single data point. They simulate 210 00:09:47.759 --> 00:09:49.639 what the Sun would look like if it were a 211 00:09:49.639 --> 00:09:51.919 pinpoint of light fifty light years away. 212 00:09:52.120 --> 00:09:54.360 I see. They force the Sun to look like a 213 00:09:54.399 --> 00:09:57.720 distant star to match the data we get from telescope. Right. 214 00:09:58.159 --> 00:10:01.399 But and here's the absolute key. They keep the original 215 00:10:01.519 --> 00:10:04.039 HD footage. So now they have a direct link. They 216 00:10:04.080 --> 00:10:06.240 can look at the fake star data and say, okay, 217 00:10:06.279 --> 00:10:08.200 look at this little dip in the light curve, what 218 00:10:08.320 --> 00:10:10.840 caused that. Then they look at the HD map from 219 00:10:10.879 --> 00:10:14.399 the same exact moment and say, aha, that dip was 220 00:10:14.480 --> 00:10:18.159 caused by this specific group of sunspots rotating across the center. 221 00:10:18.279 --> 00:10:21.039 That is genius. It totally eliminates the guesswork. Instead of 222 00:10:21.080 --> 00:10:23.720 just theorizing about what a blip on a distant star 223 00:10:23.879 --> 00:10:26.480 means we have an actual catalog of blips from our 224 00:10:26.519 --> 00:10:28.440 own sun to compare it to exactly. 225 00:10:28.480 --> 00:10:31.679 It's building a dictionary, and as we move into decoding 226 00:10:31.679 --> 00:10:34.320 the light, we find that the translation isn't always as 227 00:10:34.360 --> 00:10:37.639 straightforward as we might hope. It turns out stars can 228 00:10:37.639 --> 00:10:38.759 be incredibly tricky. 229 00:10:39.080 --> 00:10:41.600 Right, So the paper discusses a specific study by Torrio 230 00:10:41.679 --> 00:10:44.480 me and his team where they watch transit events. Now, 231 00:10:44.759 --> 00:10:47.240 for the beginners out there, a transit event just means 232 00:10:47.440 --> 00:10:50.480 something moving across the face of the star as it rotates. Right. 233 00:10:50.639 --> 00:10:54.200 Yes, the sun rotates roughly once every twenty seven days, 234 00:10:54.440 --> 00:10:56.759 so if a some spot forms on the left side, 235 00:10:56.919 --> 00:10:59.720 it will slowly march across the face to the right 236 00:10:59.759 --> 00:11:01.559 side over the course of about two weeks. 237 00:11:01.759 --> 00:11:04.360 Let's look at the first case study here, the sun spot. 238 00:11:04.840 --> 00:11:07.200 In my head, this is simple. A sunspot is a 239 00:11:07.279 --> 00:11:09.799 dark patch on the surface. It's like a dimmer switch. 240 00:11:10.200 --> 00:11:12.399 So if a dark patch moves in front of the camera, 241 00:11:13.039 --> 00:11:15.279 the total light we receive should drop. 242 00:11:15.200 --> 00:11:18.200 And invisible light the normal light our eyes can see. 243 00:11:18.480 --> 00:11:21.639 That is exactly what happens when a big sunspot group 244 00:11:21.759 --> 00:11:25.000 rotates into view. The total brightness of the sun drops 245 00:11:25.120 --> 00:11:27.440 it creates a measurable dip in the light curve. 246 00:11:27.799 --> 00:11:30.879 Simple physics, you block the light, it gets darker. But 247 00:11:30.919 --> 00:11:34.200 the notes say there's a twist here, involving something called foculae. 248 00:11:34.240 --> 00:11:37.480 There is always a twist in astrophysics. Faculae it's Latin 249 00:11:37.559 --> 00:11:38.200 for little. 250 00:11:37.919 --> 00:11:40.759 Torches, little torches. That actually sounds quite poetic. It is. 251 00:11:41.080 --> 00:11:45.759 Faculae are these bright magnetic regions that usually cluster around sunspots. 252 00:11:46.200 --> 00:11:48.960 They are like a glowing network of magnetic cracks in 253 00:11:49.000 --> 00:11:52.679 the surface. Now Here is where the geometry gets weird. 254 00:11:53.639 --> 00:11:55.879 When a sunspot is right in the middle of the 255 00:11:55.919 --> 00:12:00.279 sun looking straight at us, the dark spot wins the 256 00:12:00.320 --> 00:12:04.120 total light dips. But when that sun spot group is 257 00:12:04.159 --> 00:12:06.200 near the edge of the stone what we call the limb, 258 00:12:07.039 --> 00:12:08.600 the faculae actually take over. 259 00:12:09.000 --> 00:12:12.000 Why what does the physical position on the sphere matter. 260 00:12:12.240 --> 00:12:14.240 It has to do with something called the hot wall effect. 261 00:12:14.600 --> 00:12:16.840 The hot wall effect. Okay, break that down for us. 262 00:12:16.960 --> 00:12:19.679 Imagine a facula is like a physical depression in the 263 00:12:19.679 --> 00:12:21.480 Sun's surface, like a magnetic pothole. 264 00:12:21.559 --> 00:12:23.200 Okay, I'm picturing a pothole in the street. 265 00:12:23.399 --> 00:12:25.840 The floor of that pothole is cooler and darker than 266 00:12:25.840 --> 00:12:28.639 the surrounding area. But the vertical walls of the pothole 267 00:12:28.679 --> 00:12:30.159 are very hot and very bright. 268 00:12:30.320 --> 00:12:30.720 Got it. 269 00:12:30.879 --> 00:12:33.759 If you look straight down into the pothole from when 270 00:12:33.759 --> 00:12:36.120 it's perfectly in the center of the sun facing Earth, 271 00:12:36.600 --> 00:12:38.799 you mostly just see the cool, dark floor, so it 272 00:12:38.840 --> 00:12:39.840 doesn't look very bright to you. 273 00:12:40.000 --> 00:12:41.879 But if I look at it from a severe angle. 274 00:12:41.919 --> 00:12:44.799 Exactly as it rotates to the edge of the sun, 275 00:12:45.039 --> 00:12:48.639 your viewing angle changes drastically. You can no longer see 276 00:12:48.639 --> 00:12:51.600 the dark floor of the pothole at all. Your line 277 00:12:51.639 --> 00:12:55.159 of sight hits the vertical, glowing, hot wall of the canyon. 278 00:12:55.799 --> 00:12:59.679 So suddenly this thing that looked faint or dark becomes 279 00:12:59.679 --> 00:13:00.720 in predibly bright. 280 00:13:01.320 --> 00:13:05.200 That is wild. So depending entirely on where the sunspot 281 00:13:05.240 --> 00:13:08.120 is located on the sphere, the star as a whole 282 00:13:08.200 --> 00:13:09.279 might look dimmer. 283 00:13:09.039 --> 00:13:12.360 Or brighter exactly when the active region is on the edge. 284 00:13:12.600 --> 00:13:16.159 Those faculty a can actually boost the total brightness so 285 00:13:16.360 --> 00:13:19.919 much that they completely cancel out the darkness of the sunspot. 286 00:13:20.279 --> 00:13:22.960 So a sunspot signal isn't just a simple dip. It's 287 00:13:22.960 --> 00:13:25.600 a very complex dance of dipping and brightening depending on 288 00:13:25.639 --> 00:13:26.360 the viewing angle. 289 00:13:26.480 --> 00:13:29.639 That definitely complicates things for astronomers looking at other stars. 290 00:13:29.720 --> 00:13:31.519 If you don't know about the hot wall effect, you 291 00:13:31.600 --> 00:13:34.440 might completely misinterpret the light data you're receiving. 292 00:13:34.600 --> 00:13:37.440 You absolutely would, You'd think the star was behaving erratically. 293 00:13:37.840 --> 00:13:40.360 And it gets even trickier with the second case study, 294 00:13:40.600 --> 00:13:41.840 the spotless. 295 00:13:41.279 --> 00:13:44.759 Pledge pledge p lage. That's French for b Trech. 296 00:13:45.080 --> 00:13:48.679 Yes it is. In solar physics, a plage is basically 297 00:13:48.720 --> 00:13:52.000 a huge region of magnetic activity, very much like a 298 00:13:52.000 --> 00:13:55.080 sunspot group, but without the actual dark spot in the middle. 299 00:13:55.200 --> 00:13:58.480 It's just the bright magnetic network spread out over an area, so. 300 00:13:58.440 --> 00:14:01.799 It's basically a sunspot ghost. It has all the underlying magnetism, 301 00:14:01.840 --> 00:14:02.919 but none of the dark core. 302 00:14:03.320 --> 00:14:06.720 In a way, yes, now here is the kicker. If 303 00:14:06.759 --> 00:14:09.320 you look at a plage in visible light, you barely 304 00:14:09.360 --> 00:14:12.000 see it at all because there is no dark spot 305 00:14:12.039 --> 00:14:15.159 to block the light, and that bright magnetic network is 306 00:14:15.279 --> 00:14:18.360 just too faint to show up against the overwhelming glare 307 00:14:18.399 --> 00:14:20.759 of the rest of the Sun, so the visible light 308 00:14:20.799 --> 00:14:22.000 curve just stays flat. 309 00:14:22.080 --> 00:14:24.279 So if I'm an alien astronomer looking at our Sun 310 00:14:24.360 --> 00:14:27.879 with a regular visible light telescope and a massive plage 311 00:14:27.960 --> 00:14:31.399 rotates by, I just think the Sun is completely quiet. 312 00:14:31.120 --> 00:14:33.080 You'd think it was fast asleep. You'd write in your 313 00:14:33.120 --> 00:14:36.279 log no activity today. But if you switch your telescope 314 00:14:36.320 --> 00:14:40.279 to look an ultraviolet light, that exact same plage lights 315 00:14:40.360 --> 00:14:41.399 up like a Christmas tree. 316 00:14:41.480 --> 00:14:42.639 It suddenly becomes visible. 317 00:14:42.799 --> 00:14:45.799 It totally dominates the view. In UV, the plage is 318 00:14:45.919 --> 00:14:49.320 screaming with activity. This is one of the most important 319 00:14:49.399 --> 00:14:52.840 lessons we've learned from the SDEO data. Visible light is 320 00:14:52.879 --> 00:14:56.879 a terrible, terrible way to measure the true magnetic activity 321 00:14:56.919 --> 00:14:59.480 of a star. You might look at a star invisible 322 00:14:59.559 --> 00:15:02.000 light and thing it's boring and safe, But if you 323 00:15:02.039 --> 00:15:05.799 switch to UV, you realize it's actually raging with massive 324 00:15:05.879 --> 00:15:07.039 magnetic storms. 325 00:15:07.279 --> 00:15:09.639 That feels like a very important distinction, especially if we're 326 00:15:09.679 --> 00:15:12.840 looking for habitable planets around these stars. We'll definitely get 327 00:15:12.879 --> 00:15:15.639 to the habitability question later, but this idea that a 328 00:15:15.679 --> 00:15:18.240 star can hide its aggression so to speak, in the 329 00:15:18.360 --> 00:15:21.080 UV spectrum is a bit unsettling. 330 00:15:21.240 --> 00:15:24.559 It completely changes how we interpret so called quiet stars 331 00:15:24.559 --> 00:15:25.399 in our galaxy. 332 00:15:25.639 --> 00:15:28.279 I want to talk about another geometric puzzle mentioned in 333 00:15:28.320 --> 00:15:32.240 the research, the time lags. This connects back to the 334 00:15:32.279 --> 00:15:33.879 three dimensional structure of the Sun. 335 00:15:34.120 --> 00:15:37.000 This is one of my favorite visualizations from the Toriumi paper. 336 00:15:37.360 --> 00:15:40.759 It's about fundamentally understanding that the Sun isn't a flat 337 00:15:40.799 --> 00:15:43.840 disk painted on the sky. It's a sphere, and it 338 00:15:43.879 --> 00:15:46.159 has an atmosphere that extends far upwards. 339 00:15:46.240 --> 00:15:48.759 The notes used a skyscraper analogy for this. Walk me 340 00:15:48.759 --> 00:15:49.159 through it. 341 00:15:49.360 --> 00:15:53.799 Okay, imagine a giant skyscraper built right on the equator 342 00:15:53.840 --> 00:15:55.879 of the Earth, and the Earth is rotating. 343 00:15:55.960 --> 00:15:59.840 Okay, I'm picturing it a massive skyscraper rotating toward me 344 00:16:00.120 --> 00:16:00.919 over the horizon. 345 00:16:01.120 --> 00:16:04.200 As that skyscraper rotates over the horizon, coming toward you, 346 00:16:04.600 --> 00:16:06.440 what part of the building do you see? First? 347 00:16:06.600 --> 00:16:09.200 I see the top of the tower, first, the antenna 348 00:16:09.279 --> 00:16:10.559 on the roof right. 349 00:16:10.320 --> 00:16:12.559 And then a little while later, as it keeps rotating, 350 00:16:12.559 --> 00:16:14.799 you see the middle floors, and finally you see the 351 00:16:14.799 --> 00:16:16.080 lobby down at ground level. 352 00:16:16.159 --> 00:16:18.519 Right. Because the Earth is curved, the top of the 353 00:16:18.559 --> 00:16:21.519 tower peaks over the horizon before the base does exactly. 354 00:16:21.879 --> 00:16:25.240 Now apply that exact same logic to the Sun. A 355 00:16:25.320 --> 00:16:28.840 sunspot is at the ground level the surface or photosphere, 356 00:16:29.480 --> 00:16:32.320 but above that sunspot, extending high up into the solar 357 00:16:32.360 --> 00:16:36.919 atmosphere are giant loops of glowing magnetic plasma that's the 358 00:16:36.960 --> 00:16:39.000 top of the skyscraper the corona. 359 00:16:39.159 --> 00:16:41.600 So as the sun rotates, we should logically see the 360 00:16:41.639 --> 00:16:44.840 loops in the atmosphere before we see the actual spot 361 00:16:44.840 --> 00:16:45.120 on the. 362 00:16:45.080 --> 00:16:49.440 Surface precisely, and that is exactly what the sdo instruments see. 363 00:16:49.480 --> 00:16:52.440 We see the ultraviolet signal, which represents the high loops 364 00:16:52.919 --> 00:16:55.879 rise in intensity, before we see the visible light signal 365 00:16:56.039 --> 00:16:59.840 the spot dip. There is a clearly measurable time lag 366 00:16:59.840 --> 00:17:01.000 between the two signals. 367 00:17:01.039 --> 00:17:04.440 That is fascinating. We are literally measuring the rotation of 368 00:17:04.480 --> 00:17:05.960 a three dimensional structure. 369 00:17:06.119 --> 00:17:08.680 And here is why it matters so much for distant stars. 370 00:17:08.960 --> 00:17:11.480 When we look at a star one hundred light years away, 371 00:17:11.519 --> 00:17:13.680 we can't see the loops. We can't see the spot. 372 00:17:13.759 --> 00:17:16.200 We just see lines on a graph. But if we 373 00:17:16.279 --> 00:17:18.759 observe that the UV light from that star gets bright 374 00:17:18.920 --> 00:17:21.839 a few hours before the visible light dims. 375 00:17:21.559 --> 00:17:23.559 We can calculate how tall the skyscraper is. 376 00:17:23.680 --> 00:17:26.720 Bingo, we can estimate the physical height of the magnetic 377 00:17:26.799 --> 00:17:28.839 loops on a star we can't even resolve into a 378 00:17:28.839 --> 00:17:32.039 picture just by measuring the time lag between the different 379 00:17:32.119 --> 00:17:34.240 colors of light arriving at our telescopes. 380 00:17:34.359 --> 00:17:37.200 That is incredible. It's like hearing a thunderclap and counting 381 00:17:37.200 --> 00:17:39.759 the seconds to estimate the distance of the storm. But 382 00:17:39.799 --> 00:17:42.440 we're doing it for stellar architecture across the galaxy. 383 00:17:42.640 --> 00:17:45.680 That is a perfect analogy. We are decoding the three 384 00:17:45.720 --> 00:17:48.839 D structure of a star from a flat one D signal. 385 00:17:49.160 --> 00:17:51.519 Okay, let's move to the mystery of the dimming light. 386 00:17:52.039 --> 00:17:55.160 Because usually when we talk about activity on the sun 387 00:17:55.240 --> 00:17:59.240 flares heating magnetism, we talk about things getting brighter. More 388 00:17:59.319 --> 00:18:02.480 energy means more light, right, but the data should something 389 00:18:02.559 --> 00:18:05.000 really counterintuitive in a specific wavelength. 390 00:18:05.160 --> 00:18:07.599 Yes, this was a real puzzle for a while. It 391 00:18:07.640 --> 00:18:11.720 happened specifically in the AIA one seventy one angstrom channel. 392 00:18:12.000 --> 00:18:14.279 Remind us again what one hundred and seventy one angstroms 393 00:18:14.319 --> 00:18:16.279 represents in this context. 394 00:18:15.960 --> 00:18:19.880 It corresponds to iron nine iron atoms that have lost 395 00:18:19.920 --> 00:18:23.599 eight of their electrons. This specific stay happens when the 396 00:18:23.640 --> 00:18:27.480 gas is at a temperature of about one million degrees kelvin. 397 00:18:27.240 --> 00:18:31.240 A million degrees, which, shockingly in solar physics is considered 398 00:18:31.279 --> 00:18:31.799 just warm. 399 00:18:31.960 --> 00:18:35.279 Correct, it's the warm corona. Now, you would naturally expect 400 00:18:35.480 --> 00:18:38.359 that when a new magnetic active region appears, it would 401 00:18:38.359 --> 00:18:40.720