WEBVTT 0 00:00:01.200 --> 00:00:04.160 Anna: Welcome to Astronomy Daily. I'm Anna. 1 00:00:04.400 --> 00:00:07.400 Avery: And I'm avery. It's Monday, the 27th 2 00:00:07.400 --> 00:00:10.160 of July, 2026, and tonight, 3 00:00:10.160 --> 00:00:12.560 the smallest headliner we've had in a while 4 00:00:12.560 --> 00:00:13.680 gets top billing. 5 00:00:14.080 --> 00:00:16.600 Anna: That's right. Our lead is a world you 6 00:00:16.600 --> 00:00:19.120 cannot see without a decent telescope, 7 00:00:19.280 --> 00:00:21.960 one that half of the astronomy community will 8 00:00:21.960 --> 00:00:24.760 tell you isn't even a planet. And today is 9 00:00:24.760 --> 00:00:27.440 its brightest night of the year. Pluto 10 00:00:27.440 --> 00:00:30.330 reaches opposition. We're going to spend some 11 00:00:30.330 --> 00:00:32.730 proper time there. The discovery, the 12 00:00:32.730 --> 00:00:35.210 demotion that people are still arguing about, 13 00:00:35.530 --> 00:00:38.490 and the frozen world New Horizons actually 14 00:00:38.650 --> 00:00:39.850 found waiting for us. 15 00:00:40.570 --> 00:00:43.130 Avery: Then, um, three quick stops. A crew comes 16 00:00:43.130 --> 00:00:46.090 home after 241 days in orbit. 17 00:00:46.330 --> 00:00:48.690 New modeling suggests the most common planet 18 00:00:48.690 --> 00:00:51.410 in the galaxy may be hiding oceans of molten 19 00:00:51.410 --> 00:00:54.050 rock. And astronomers have taken the famous 20 00:00:54.050 --> 00:00:56.370 first ever black hole image and pulled a 21 00:00:56.370 --> 00:00:58.170 whole new layer of physics out of it. 22 00:00:58.530 --> 00:01:01.250 Anna: And we'll close where we always do, under the 23 00:01:01.250 --> 00:01:03.890 sky north and south, with a M meteor 24 00:01:03.890 --> 00:01:06.410 shower that's putting on its best show for 25 00:01:06.410 --> 00:01:09.050 our Southern Hemisphere listeners. Let's get 26 00:01:09.050 --> 00:01:09.570 into it. 27 00:01:09.890 --> 00:01:12.850 So, Avery set the scene for me. If someone 28 00:01:12.850 --> 00:01:15.330 walks out tonight and looks up, are they 29 00:01:15.330 --> 00:01:16.770 going to see Pluto? 30 00:01:17.090 --> 00:01:19.770 Avery: Honestly, no. Not with their eyes and not 31 00:01:19.770 --> 00:01:22.290 with a pair of binoculars. Tonight, Pluto 32 00:01:22.290 --> 00:01:24.770 sits directly opposite the sun in our sky, 33 00:01:24.770 --> 00:01:27.620 over in the constellation Capricornus. That's 34 00:01:27.620 --> 00:01:29.940 what opposition means. Earth is passing 35 00:01:29.940 --> 00:01:32.780 between Pluto and the Sun. So Pluto rises 36 00:01:32.780 --> 00:01:35.380 at sunset, sits highest around midnight, 37 00:01:35.540 --> 00:01:37.980 and it's fully lit and as close to us as it 38 00:01:37.980 --> 00:01:40.380 gets all year. A, uh, touch under 35 39 00:01:40.380 --> 00:01:43.100 astronomical units. So roughly 35 40 00:01:43.100 --> 00:01:44.380 times the Earth's sun 41 00:01:44.380 --> 00:01:46.900 Anna: distance, and that's as good as it gets. 42 00:01:46.900 --> 00:01:49.580 Avery: And it's still faint, painfully 43 00:01:49.580 --> 00:01:52.100 faint. We're talking about magnitude 15, 44 00:01:52.990 --> 00:01:55.350 to put that in human terms. It's millions of 45 00:01:55.350 --> 00:01:57.430 times dimmer than the faintest star you can 46 00:01:57.430 --> 00:01:59.830 pick out on a dark night. You realistically 47 00:01:59.830 --> 00:02:02.230 need an 8 inch telescope and a good star 48 00:02:02.230 --> 00:02:04.750 chart. And even then, Pluto looks like 49 00:02:04.990 --> 00:02:07.790 a star, a dot that only gives itself away 50 00:02:07.790 --> 00:02:09.790 because it shifts position over a 51 00:02:09.790 --> 00:02:12.670 Anna: couple of nights, which is exactly how it was 52 00:02:12.670 --> 00:02:14.950 found in the first place. Let's rewind. 53 00:02:14.950 --> 00:02:17.310 Because the Pluto story is one of the great 54 00:02:17.310 --> 00:02:19.150 underdog tales in astronomy. 55 00:02:19.670 --> 00:02:22.630 1894, Percival Lowell, the same 56 00:02:22.630 --> 00:02:25.190 wealthy Bostonian who convinced himself 57 00:02:25.190 --> 00:02:27.950 Mars was covered in canals, sets up an 58 00:02:27.950 --> 00:02:30.590 observatory in Flagstaff, Arizona, and 59 00:02:30.590 --> 00:02:33.550 becomes obsessed, um, with a planet X he 60 00:02:33.550 --> 00:02:36.110 was sure was tugging on the orbits of Uranus 61 00:02:36.110 --> 00:02:36.950 and Neptune. 62 00:02:37.270 --> 00:02:40.150 Avery: And, um, he never found it. He died in 1916, 63 00:02:40.390 --> 00:02:41.190 still hunting. 64 00:02:41.590 --> 00:02:44.030 Anna: He did the search, went cold, then 65 00:02:44.030 --> 00:02:46.910 restarting. And in 1929 the 66 00:02:46.910 --> 00:02:49.910 job landed on a 23 year old Kansas farm 67 00:02:49.910 --> 00:02:52.330 boy with no colonies college degree named 68 00:02:52.330 --> 00:02:55.090 Clyde Tombaugh. His method was brutal, 69 00:02:55.090 --> 00:02:58.010 painstaking work. Photograph the same patch 70 00:02:58.010 --> 00:03:00.450 of sky on different nights. Then flick 71 00:03:00.450 --> 00:03:02.730 between the two plates in a machine called a 72 00:03:02.730 --> 00:03:05.530 blink comparator, looking for the one dot 73 00:03:05.530 --> 00:03:07.890 out of hundreds of thousands that moved. 74 00:03:08.290 --> 00:03:10.290 Avery: That is the definition of patience. 75 00:03:10.450 --> 00:03:13.290 Anna: On the 18th of February 1930 he 76 00:03:13.290 --> 00:03:16.090 found it. And here's a detail I love. The 77 00:03:16.090 --> 00:03:18.750 name didn't come from an astronomer. It came 78 00:03:18.750 --> 00:03:21.190 from an 11 year old English schoolgirl, 79 00:03:21.190 --> 00:03:23.670 Venetia Burney. Over breakfast she 80 00:03:23.670 --> 00:03:25.910 suggested Pluto, the Roman God of the 81 00:03:25.910 --> 00:03:28.430 underworld, fitting for a cold, dark, 82 00:03:28.430 --> 00:03:31.270 distant world. And the first two letters, P 83 00:03:31.270 --> 00:03:33.750 and L also happen to honor Percival 84 00:03:33.750 --> 00:03:35.230 Lowell. It stuck. 85 00:03:35.950 --> 00:03:38.910 Avery: So for 76 years, Pluto is the ninth 86 00:03:38.910 --> 00:03:41.180 planet. It's on every classroom wall, um, 87 00:03:41.180 --> 00:03:43.830 every lunchbox, every mobile over a 88 00:03:43.830 --> 00:03:46.360 cottage. Then 2006 happens. 89 00:03:46.840 --> 00:03:49.760 Anna: Then 2006 happens. And this is 90 00:03:49.760 --> 00:03:52.480 the part people still get heated about. So 91 00:03:52.480 --> 00:03:55.200 let me try to be fair to both sides because 92 00:03:55.200 --> 00:03:57.720 there genuinely are two good sides. 93 00:03:57.960 --> 00:04:00.759 The trouble started in the years before when 94 00:04:00.759 --> 00:04:03.360 astronomers began finding other icy 95 00:04:03.360 --> 00:04:06.040 bodies out past Neptune in a region called 96 00:04:06.040 --> 00:04:08.840 the Kuiper belt. And in 2005 97 00:04:08.920 --> 00:04:11.720 a team found Eris, which at the time 98 00:04:11.800 --> 00:04:13.720 looked to be bigger than Pluto. 99 00:04:14.160 --> 00:04:16.800 Avery: And that's the crunch. If Pluto's a planet, 100 00:04:16.800 --> 00:04:19.720 is eris planet number 10? What about the 101 00:04:19.720 --> 00:04:20.840 next 20 objects we 102 00:04:20.840 --> 00:04:23.400 Anna: find out there exactly the corner they were 103 00:04:23.400 --> 00:04:25.600 backed into. So in August 104 00:04:25.600 --> 00:04:28.200 2006, the International Astronomical 105 00:04:28.200 --> 00:04:31.040 Union voted on a formal definition of planet 106 00:04:31.040 --> 00:04:33.880 for the first time. Three rules. It has to 107 00:04:33.880 --> 00:04:36.600 orbit the Sun. It has to be roundish under 108 00:04:36.600 --> 00:04:39.570 its own gravity and the killer it, it 109 00:04:39.570 --> 00:04:41.330 has to, uh, have cleared its neighborhood of 110 00:04:41.330 --> 00:04:44.050 other debris. Pluto passes the first two 111 00:04:44.050 --> 00:04:46.810 easily, but it shares its zone with all that 112 00:04:46.810 --> 00:04:49.370 Kuiper Belt material. So it fails the third 113 00:04:49.690 --> 00:04:52.570 reclassified as a dwarf planet. It 114 00:04:52.570 --> 00:04:54.530 even got a minor planet catalog 115 00:04:54.530 --> 00:04:57.450 Avery: number 134340, 116 00:04:57.850 --> 00:05:00.010 a demotion with a filing number. 117 00:05:00.490 --> 00:05:02.970 Ouch. Not everyone accepted it, 118 00:05:03.290 --> 00:05:03.970 not at all. 119 00:05:03.970 --> 00:05:06.130 Anna: And this is the bit I want listeners to sit 120 00:05:06.130 --> 00:05:08.770 with because it's not settled science. It's a 121 00:05:08.770 --> 00:05:11.280 definition. And definitions are choices. 122 00:05:11.830 --> 00:05:14.030 The loudest objection comes from planetary 123 00:05:14.030 --> 00:05:16.790 scientists and Alan Stern, who leads the New 124 00:05:16.790 --> 00:05:19.110 Horizons mission, is the most prominent. 125 00:05:19.350 --> 00:05:21.670 Their argument is roughly clearing the 126 00:05:21.670 --> 00:05:24.190 neighborhood is a strange test because it 127 00:05:24.190 --> 00:05:26.910 depends on where an object is, not what it 128 00:05:26.910 --> 00:05:29.870 is. Put Earth out at Pluto's distance and 129 00:05:29.870 --> 00:05:32.470 Earth wouldn't clear that huge orbit either. 130 00:05:32.630 --> 00:05:35.470 They prefer a geophysical definition if 131 00:05:35.470 --> 00:05:37.630 it's big enough for gravity to pull it round. 132 00:05:37.630 --> 00:05:40.430 And it's not a star, it's a planet, full 133 00:05:40.430 --> 00:05:43.430 stop. By that logic, Pluto is a planet, and 134 00:05:43.430 --> 00:05:45.750 so are, uh, a dozen other round worlds. 135 00:05:46.150 --> 00:05:48.830 Avery: And the counterargument, the dynamical 136 00:05:48.830 --> 00:05:49.190 camp. 137 00:05:49.190 --> 00:05:51.870 Anna: The folks who wrote the IAU rule say a 138 00:05:51.870 --> 00:05:54.710 definition has to be useful. And anything 139 00:05:54.710 --> 00:05:56.790 round gives you potentially hundreds of 140 00:05:56.790 --> 00:05:58.990 planets, which tells you nothing about how 141 00:05:58.990 --> 00:06:01.190 the solar system is actually organized. 142 00:06:01.510 --> 00:06:03.830 Clearing your orbit captures something real. 143 00:06:03.990 --> 00:06:06.550 The eight major planets are gravitationally 144 00:06:06.550 --> 00:06:09.360 dominant and the Kuiper bell objects simply 145 00:06:09.360 --> 00:06:12.120 aren't. So it's genuinely a values question. 146 00:06:12.360 --> 00:06:15.360 Do you classify by the object itself or by 147 00:06:15.360 --> 00:06:17.880 the role it plays in the system? Reasonable 148 00:06:17.880 --> 00:06:19.320 people land differently. 149 00:06:19.640 --> 00:06:22.120 Avery: And then, as if the universe wanted to make 150 00:06:22.120 --> 00:06:24.200 everyone regret the timing, New 151 00:06:24.200 --> 00:06:27.120 Anna: horizon shows up the best twist in the 152 00:06:27.120 --> 00:06:29.560 whole saga. The probe launched in January 153 00:06:29.720 --> 00:06:32.520 2006, seven months before the vote. 154 00:06:32.520 --> 00:06:34.800 So it left Earth as a mission to the ninth 155 00:06:34.800 --> 00:06:37.480 planet and arrived in July 2015 156 00:06:37.800 --> 00:06:40.480 at a dwarf planet. And what it sent back 157 00:06:40.480 --> 00:06:43.400 demolished the idea that small and far means 158 00:06:43.400 --> 00:06:44.440 dull and dead. 159 00:06:44.760 --> 00:06:47.080 Avery: This is my favorite part. Because we expected 160 00:06:47.160 --> 00:06:48.800 a cratered frozen billiard 161 00:06:48.800 --> 00:06:51.400 Anna: ball, we got a stunningly complex 162 00:06:51.480 --> 00:06:54.480 active world. There's a vast bright plain of 163 00:06:54.480 --> 00:06:57.360 frozen nitrogen sputnik plantina that 164 00:06:57.360 --> 00:06:59.840 sits inside a uh, giant heart shaped feature 165 00:06:59.840 --> 00:07:02.480 the whole Internet fell for. And that heart 166 00:07:02.480 --> 00:07:05.400 isn't static. The nitrogen ice is slowly 167 00:07:05.400 --> 00:07:08.040 churning, convecting like a lava lamp in 168 00:07:08.040 --> 00:07:10.560 ultra slow motion. Which is why it has almost 169 00:07:10.560 --> 00:07:12.780 no crater. The surface is being 170 00:07:12.780 --> 00:07:15.580 resurfaced. There's mountains of water ice 171 00:07:15.580 --> 00:07:18.300 as tall as the rockies. Because at Pluto's 172 00:07:18.300 --> 00:07:21.300 temperatures, water ice is hard as rock. A 173 00:07:21.300 --> 00:07:23.860 thin blue tinged nitrogen atmosphere with 174 00:07:23.860 --> 00:07:26.700 layers of haze and a real possibility of a 175 00:07:26.700 --> 00:07:29.260 liquid water ocean sloshing beneath the 176 00:07:29.260 --> 00:07:29.620 crust. 177 00:07:30.020 --> 00:07:32.900 Avery: A subsurface ocean on um, a world people were 178 00:07:32.900 --> 00:07:34.860 arguing wasn't important enough to be a 179 00:07:34.860 --> 00:07:35.300 planet. 180 00:07:35.460 --> 00:07:37.740 Anna: Which is the poetry of it, isn't it? The 181 00:07:37.740 --> 00:07:40.420 label we hang on Pluto changed nothing about 182 00:07:40.420 --> 00:07:43.380 Pluto. It's exactly as fascinating as the day 183 00:07:43.380 --> 00:07:45.580 before the vote. And it's not alone out 184 00:07:45.580 --> 00:07:48.420 there. It has five moons of its own. The big 185 00:07:48.420 --> 00:07:51.180 one, Charon, so large that the two of them 186 00:07:51.180 --> 00:07:53.619 orbit a point in empty space between them 187 00:07:53.700 --> 00:07:55.540 Like a slow cosmic waltz. 188 00:07:55.940 --> 00:07:58.060 Avery: So tonight, when it's at its brightest and 189 00:07:58.060 --> 00:08:00.708 best place for the year, that faint 15th 190 00:08:00.852 --> 00:08:03.780 magnitude.in Capricornus is a churning, hazy, 191 00:08:04.200 --> 00:08:06.400 possibly ocean bearing world with a heart on 192 00:08:06.400 --> 00:08:06.920 its face. 193 00:08:07.320 --> 00:08:09.520 Anna: That's the one and whatever you want to call 194 00:08:09.520 --> 00:08:12.520 it, planet, dwarf planet, Kuiper belt object. 195 00:08:12.680 --> 00:08:15.240 Tonight is Pluto's night. We'll tell you 196 00:08:15.240 --> 00:08:17.240 exactly where to point a scope in the sky. 197 00:08:17.240 --> 00:08:19.600 Watch. Clyde Tombaugh, by the way, passed 198 00:08:19.600 --> 00:08:22.560 away in 1997. And new horizons 199 00:08:22.560 --> 00:08:25.120 carried a small portion of his ashes on that 200 00:08:25.120 --> 00:08:27.880 flyby. He got to visit the world he found. 201 00:08:28.280 --> 00:08:30.760 Avery: Okay, I'm not crying. You're crying. 202 00:08:31.440 --> 00:08:33.600 Lets bring it back to Earth literally. 203 00:08:34.000 --> 00:08:36.640 Speaking of coming home, three people did 204 00:08:36.640 --> 00:08:39.320 exactly that yesterday on, um, Sunday, a 205 00:08:39.320 --> 00:08:42.200 Soyuz MS.28 capsule parachuted down 206 00:08:42.200 --> 00:08:45.000 onto the steppe of Kazakhstan, bringing NASA 207 00:08:45.000 --> 00:08:47.520 astronaut Chris Williams and Roscosmos 208 00:08:47.520 --> 00:08:50.400 cosmonauts Sergey Kut Sverchkov and Sergey 209 00:08:50.400 --> 00:08:53.200 Mikhayev back after 241 days 210 00:08:53.440 --> 00:08:55.440 aboard the International Space Station. 211 00:08:55.920 --> 00:08:58.920 Anna: 241 days put a number on what 212 00:08:58.920 --> 00:08:59.760 that actually is. 213 00:09:00.430 --> 00:09:02.430 Avery: Nearly eight months, around 214 00:09:02.430 --> 00:09:05.190 3,885 laps of the 215 00:09:05.190 --> 00:09:08.030 Earth and more than 102 million miles 216 00:09:08.110 --> 00:09:10.630 traveled, all while effectively standing 217 00:09:10.630 --> 00:09:13.230 still in orbit. They launched back on the 218 00:09:13.230 --> 00:09:16.229 27th of November, American Thanksgiving. So 219 00:09:16.229 --> 00:09:18.510 they've missed an entire summer and winter 220 00:09:18.510 --> 00:09:19.790 depending on your hemisphere. 221 00:09:20.030 --> 00:09:22.110 Anna: And it was a first flight for two of them. 222 00:09:22.350 --> 00:09:24.870 Avery: It was first mission for Williams and for 223 00:09:24.870 --> 00:09:27.840 Mikhayv. Gutsverchkov's the veteran. He's 224 00:09:27.840 --> 00:09:30.520 now passed 425 days in space 225 00:09:30.520 --> 00:09:33.360 across two flights. And I want to flag the 226 00:09:33.360 --> 00:09:35.480 quiet significance here. A, uh, NASA 227 00:09:35.480 --> 00:09:38.120 astronaut and two Russian cosmonauts riding 228 00:09:38.120 --> 00:09:40.920 home together in a Russian capsule. Whatever 229 00:09:40.920 --> 00:09:43.280 the politics on the ground, the crude side of 230 00:09:43.280 --> 00:09:45.720 this partnership just keeps functioning, seat 231 00:09:45.720 --> 00:09:46.560 swaps and all. 232 00:09:46.800 --> 00:09:48.960 Anna: What was Williams actually doing up there? 233 00:09:48.960 --> 00:09:51.080 It's easy to forget these are working science 234 00:09:51.080 --> 00:09:52.800 missions, not just endurance feats. 235 00:09:53.430 --> 00:09:55.630 Avery: Right. And his work is genuinely down to 236 00:09:55.630 --> 00:09:58.270 Earth in its aims. He supported research into 237 00:09:58.270 --> 00:10:00.630 novel cancer therapies which benefit from the 238 00:10:00.630 --> 00:10:03.350 way proteins and cells behave in microgravity 239 00:10:03.590 --> 00:10:05.670 and into manufacturing high performance 240 00:10:05.830 --> 00:10:07.990 materials, the kind used in advanced 241 00:10:07.990 --> 00:10:10.310 electronics and computing that you can make 242 00:10:10.310 --> 00:10:12.350 more plainly without gravity pulling 243 00:10:12.350 --> 00:10:14.790 everything around. The pair of cosmonauts 244 00:10:14.790 --> 00:10:17.390 also did a spacewalk back in May to install a 245 00:10:17.390 --> 00:10:19.630 solar radiation instrument on the station's 246 00:10:19.630 --> 00:10:20.150 exterior. 247 00:10:20.500 --> 00:10:22.580 Anna: And the handover keeps the station rolling 248 00:10:22.980 --> 00:10:23.860 seamlessly. 249 00:10:24.100 --> 00:10:26.660 Avery: Command passed to NASA's Jessica Meyer as 250 00:10:26.660 --> 00:10:29.660 Expedition 74 became 75 and 251 00:10:29.660 --> 00:10:31.740 a fresh crew. Anil, uh Menin and two 252 00:10:31.740 --> 00:10:34.100 cosmonauts arrived earlier this month to keep 253 00:10:34.100 --> 00:10:36.620 the lab staffed. The hard part now, 254 00:10:36.620 --> 00:10:39.620 ironically, is gravity. After eight months, 255 00:10:39.700 --> 00:10:42.180 just holding your own head up is exhausting. 256 00:10:42.340 --> 00:10:44.100 The readjustment takes weeks. 257 00:10:44.580 --> 00:10:47.140 Anna: Welcome home to the three of them now from 258 00:10:47.140 --> 00:10:49.780 people orbiting one planet to the most common 259 00:10:49.780 --> 00:10:51.980 kind of planet in the entire galaxy. 260 00:10:52.380 --> 00:10:55.220 Avery: Moving on to story three, sub Neptune's 261 00:10:55.220 --> 00:10:58.180 clouds of Rock, oceans of magma. What's this 262 00:10:58.180 --> 00:10:58.620 all about? 263 00:10:58.780 --> 00:11:01.420 Anna: Here's a fact that still catches me out. The 264 00:11:01.420 --> 00:11:03.660 most common type of planet in the Milky Way 265 00:11:03.660 --> 00:11:06.100 is a type we don't have. It's the sub 266 00:11:06.100 --> 00:11:08.300 Neptune. Bigger than Earth, smaller than 267 00:11:08.300 --> 00:11:10.580 Neptune. There's nothing like it in our solar 268 00:11:10.580 --> 00:11:13.460 system, yet they turn up everywhere else. Out 269 00:11:13.460 --> 00:11:16.380 of more than 6,000 confirmed exoplanets, well 270 00:11:16.380 --> 00:11:18.620 over 2,000 are, uh, sub Neptunes. 271 00:11:18.860 --> 00:11:20.580 Avery: And we barely understand what they're made 272 00:11:20.580 --> 00:11:20.860 of. 273 00:11:21.180 --> 00:11:23.460 Anna: That's the frustration. They could be small, 274 00:11:23.460 --> 00:11:25.820 rocky cores wrapped in thick hydrogen 275 00:11:25.820 --> 00:11:28.260 atmospheres, or they could be water worlds, 276 00:11:28.260 --> 00:11:30.900 volatile, rich, drowning in water and carbon 277 00:11:30.900 --> 00:11:33.700 molecules. And we can't easily tell because 278 00:11:33.700 --> 00:11:36.300 even the James Webb telescope can only read 279 00:11:36.300 --> 00:11:38.780 the very top of the atmosphere. And these 280 00:11:38.780 --> 00:11:41.660 atmospheres are deep and hazy. New 281 00:11:41.660 --> 00:11:43.660 modeling from a team at Arizona State, 282 00:11:43.660 --> 00:11:46.060 recently published, offers a clever way 283 00:11:46.060 --> 00:11:48.500 through. And it puts clouds at the center of 284 00:11:48.500 --> 00:11:48.940 the story. 285 00:11:49.420 --> 00:11:52.220 Avery: Clouds on a planet where weather must 286 00:11:52.220 --> 00:11:53.260 mean something wild. 287 00:11:53.740 --> 00:11:56.540 Anna: Wild is the word deep down, where the 288 00:11:56.540 --> 00:11:59.500 pressure is crushing. The team modeled clouds 289 00:11:59.500 --> 00:12:02.180 made of vaporized rock and salt. Think 290 00:12:02.180 --> 00:12:04.740 aluminum oxide, iron silicates, 291 00:12:04.740 --> 00:12:07.460 potassium chloride. Actual mineral 292 00:12:07.460 --> 00:12:10.290 clouds. And here's the key finding those 293 00:12:10.290 --> 00:12:13.090 clouds act like a blanket. They trap heat 294 00:12:13.090 --> 00:12:15.210 trying to escape from the interior, which 295 00:12:15.210 --> 00:12:17.210 pushes the boundary between the atmosphere 296 00:12:17.210 --> 00:12:19.570 and the solid body to temperatures high 297 00:12:19.570 --> 00:12:20.970 enough to melt rock. 298 00:12:21.290 --> 00:12:23.330 Avery: So beneath the clouds, you might have an 299 00:12:23.330 --> 00:12:26.050 ocean of magma, a global magma 300 00:12:26.050 --> 00:12:28.810 Anna: ocean in the cloudy scenario. In the cloud 301 00:12:28.810 --> 00:12:31.210 free version, that boundary is cooler and 302 00:12:31.210 --> 00:12:33.570 might stay solid. Same planet from the 303 00:12:33.570 --> 00:12:36.330 outside, two completely different interiors, 304 00:12:36.330 --> 00:12:38.900 depending on the clouds. And that matters for 305 00:12:38.900 --> 00:12:41.780 us for a very practical reason. It changes 306 00:12:41.780 --> 00:12:44.540 how we interpret what Webb sees, and it feeds 307 00:12:44.540 --> 00:12:47.020 directly into which of these worlds we bother 308 00:12:47.020 --> 00:12:48.700 calling potentially habitable. 309 00:12:48.940 --> 00:12:51.700 Avery: To be fair, this is modeling, not a direct 310 00:12:51.700 --> 00:12:53.660 observation, completely fair. 311 00:12:53.740 --> 00:12:55.980 Anna: This is simulation work, pointing observers 312 00:12:55.980 --> 00:12:58.420 at what to look for. Not a photograph of 313 00:12:58.420 --> 00:13:01.340 magma, but it reframes clouds from being just 314 00:13:01.340 --> 00:13:04.180 an annoying smudge that ruins our data into 315 00:13:04.180 --> 00:13:06.460 an active ingredient, shaping the whole 316 00:13:06.460 --> 00:13:09.180 planet. For the galaxy's most common world, 317 00:13:09.260 --> 00:13:09.740 that's 318 00:13:09.740 --> 00:13:12.460 Avery: a meaningful shift from world we're modeling 319 00:13:12.460 --> 00:13:14.660 to a monster we've actually photographed. 320 00:13:14.660 --> 00:13:16.060 Let's go to M M87. 321 00:13:16.380 --> 00:13:19.360 Anna: Next up, story four, a sharper look at M 322 00:13:19.360 --> 00:13:20.860 M87's black hole. 323 00:13:21.180 --> 00:13:24.180 Avery: Cast your mind back to 2019, that 324 00:13:24.180 --> 00:13:27.180 first ever image of a black hole, the orange 325 00:13:27.180 --> 00:13:29.660 donut. That was M M87, 326 00:13:29.900 --> 00:13:32.740 the supermassive black hole at the heart of 327 00:13:32.740 --> 00:13:35.320 a giant galaxy in Virgo, about 328 00:13:35.400 --> 00:13:38.240 55 million light years away. Weighing 329 00:13:38.240 --> 00:13:40.600 in at around six and a half billion 330 00:13:40.840 --> 00:13:43.840 suns. That Single image was one of the 331 00:13:43.840 --> 00:13:46.040 defining science pictures of the decade. 332 00:13:46.360 --> 00:13:48.920 Anna: And now a team has gone back to the data and 333 00:13:48.920 --> 00:13:50.200 done something new with it. 334 00:13:50.360 --> 00:13:53.160 Avery: They have. Researchers led by the Shanghai 335 00:13:53.160 --> 00:13:55.240 Astronomical Observatory with international 336 00:13:55.400 --> 00:13:57.640 collaborators have produced the first 337 00:13:57.640 --> 00:14:00.240 spatially resolved dual frequency spectral 338 00:14:00.240 --> 00:14:03.140 map of M M87. And I know that's a mouthful, 339 00:14:03.140 --> 00:14:05.220 so let me unpack it because it's clever. 340 00:14:05.620 --> 00:14:08.380 Anna: Please. Dual frequency spectral map needs a 341 00:14:08.380 --> 00:14:08.900 translation. 342 00:14:09.140 --> 00:14:12.100 Avery: Think of it like this. The 2019 picture was 343 00:14:12.100 --> 00:14:14.700 a single color photo of the ring. What this 344 00:14:14.700 --> 00:14:17.060 team did was image the black hole at two 345 00:14:17.060 --> 00:14:19.460 different radio wavelengths, 1.3 346 00:14:19.460 --> 00:14:22.460 millimeters and 3.5 millimeters, using the 347 00:14:22.460 --> 00:14:25.060 Event Horizon Telescope and a partner network 348 00:14:25.060 --> 00:14:27.940 called the GMVA from observations back in 349 00:14:27.940 --> 00:14:30.820 2018. Then they compared them point 350 00:14:30.820 --> 00:14:33.180 by point to see how the color of the glow 351 00:14:33.180 --> 00:14:35.340 changes as you move outward from the center. 352 00:14:35.740 --> 00:14:38.380 That comparison is the spectral index, and 353 00:14:38.380 --> 00:14:40.580 mapping it across the ring had never been 354 00:14:40.580 --> 00:14:41.100 done before. 355 00:14:41.420 --> 00:14:42.860 Anna: And what did the map show? 356 00:14:43.180 --> 00:14:45.820 Avery: A, uh, clear structure. The signal is one 357 00:14:45.820 --> 00:14:47.860 character inside the bright ring, and it 358 00:14:47.860 --> 00:14:50.860 steepens, changes flavor as you move outward, 359 00:14:50.860 --> 00:14:53.100 with the transition landing right at the ring 360 00:14:53.100 --> 00:14:55.740 itself, about 30 micro arcseconds out. 361 00:14:56.090 --> 00:14:58.530 And that's the headline. It tells us the ring 362 00:14:58.530 --> 00:15:01.370 we photographed in 2019 isn't just a trick of 363 00:15:01.370 --> 00:15:03.810 where the light happens to glow. It's tied to 364 00:15:03.810 --> 00:15:06.490 a real physical change in the plasma right 365 00:15:06.490 --> 00:15:07.770 around the event horizon. 366 00:15:07.930 --> 00:15:10.540 Anna: So why does that matter beyond. Nice. A, uh, 367 00:15:10.610 --> 00:15:11.450 sharper map. 368 00:15:11.689 --> 00:15:14.090 Avery: Because reading a black hole means untangling 369 00:15:14.090 --> 00:15:16.650 two things that are mixed together. The pure 370 00:15:16.650 --> 00:15:19.210 warping of space by gravity and the messy 371 00:15:19.210 --> 00:15:21.850 physics of superheated plasma spiraling in. 372 00:15:22.400 --> 00:15:24.120 The researchers say looking at multiple 373 00:15:24.120 --> 00:15:26.480 wavelengths lets them start to separate those 374 00:15:26.480 --> 00:15:28.800 two. That's the path to understanding how 375 00:15:28.800 --> 00:15:31.280 these monsters feed, how they fire off those 376 00:15:31.280 --> 00:15:33.680 enormous jets, and eventually to a cleaner 377 00:15:33.680 --> 00:15:36.400 test of Einstein's general relativity. It's 378 00:15:36.400 --> 00:15:38.360 the difference between having a portrait and 379 00:15:38.360 --> 00:15:39.840 starting to read the biography. 380 00:15:40.080 --> 00:15:42.640 Anna: A portrait to a biography. I'll take that. 381 00:15:42.880 --> 00:15:45.040 And on that note, let's step outside, 382 00:15:45.520 --> 00:15:48.240 because it's skywatch time. And as always, 383 00:15:48.240 --> 00:15:50.280 wherever you are on the planet, we've got 384 00:15:50.280 --> 00:15:52.960 you. Avery, you take the south, I'll take the 385 00:15:52.960 --> 00:15:54.920 north, and we'll meet in the middle at Pluto. 386 00:15:55.160 --> 00:15:57.640 Avery: Deal. Southern hemisphere first. And friends 387 00:15:57.640 --> 00:16:00.440 down south. This is your week. The Southern 388 00:16:00.440 --> 00:16:03.160 Delta Aquarids are peaking. This is a shower 389 00:16:03.160 --> 00:16:05.680 that genuinely favors the south. The radiant 390 00:16:05.680 --> 00:16:07.920 in Aquarius climbs high after midnight for 391 00:16:07.920 --> 00:16:10.360 you. And under a dark sky, you could see 392 00:16:10.360 --> 00:16:13.080 something like 20 to 25 meteors an hour. 393 00:16:13.400 --> 00:16:16.080 No equipment, just a reclining chair, a wide 394 00:16:16.080 --> 00:16:18.080 Open view and some patience while your eyes 395 00:16:18.080 --> 00:16:18.520 adapt. 396 00:16:18.760 --> 00:16:20.840 Anna: And there's a comet. For the early risers, 397 00:16:21.240 --> 00:16:22.280 There is Comet 398 00:16:22.280 --> 00:16:25.040 Avery: 10P Tempel 1 low in the pre 399 00:16:25.040 --> 00:16:27.840 dawn sky. It's uh, a binocular or small 400 00:16:27.840 --> 00:16:30.240 telescope object rather than a naked eye 401 00:16:30.240 --> 00:16:33.040 showpiece. But here's a southern bonus. It's 402 00:16:33.040 --> 00:16:35.240 diving southward through August, so our 403 00:16:35.240 --> 00:16:37.359 Southern Hemisphere listeners get the better 404 00:16:37.359 --> 00:16:40.120 and improving view. Northern folks, catch it 405 00:16:40.120 --> 00:16:40.800 now before it 406 00:16:40.800 --> 00:16:43.520 Anna: drops away from you Northern Hemisphere. Your 407 00:16:43.520 --> 00:16:46.040 headline is a star with a wonderful name. 408 00:16:46.280 --> 00:16:47.920 Look high toward the north for the 409 00:16:47.920 --> 00:16:50.240 constellation Cepheus. It looks like a 410 00:16:50.240 --> 00:16:52.420 child's drawing of a house. And near the 411 00:16:52.420 --> 00:16:54.980 bottom of that house sits Mu Cepheii, 412 00:16:55.140 --> 00:16:57.860 better known as Herschel's Garnet Star. It's 413 00:16:57.860 --> 00:16:59.980 one of the reddest stars you can see with the 414 00:16:59.980 --> 00:17:02.980 naked eye. A, uh, bloated red supergiant so 415 00:17:02.980 --> 00:17:05.220 vast that if you dropped it where the sun is, 416 00:17:05.300 --> 00:17:07.220 its surface would swallow Jupiter. 417 00:17:07.540 --> 00:17:10.140 Binoculars really bring out that deep ember 418 00:17:10.140 --> 00:17:12.700 color. And you northern observers get the 419 00:17:12.700 --> 00:17:15.580 Delta Aquariids too, just lower down toward 420 00:17:15.580 --> 00:17:16.660 your southern horizon. 421 00:17:16.980 --> 00:17:19.780 Avery: And now the meeting point, the one we teased 422 00:17:19.780 --> 00:17:21.370 at the top, Pluto. 423 00:17:21.530 --> 00:17:23.930 Anna: Pluto's at opposition tonight over in 424 00:17:23.930 --> 00:17:26.450 Capricornus, which is beautifully placed for 425 00:17:26.450 --> 00:17:29.010 the Southern Hemisphere high overhead and 426 00:17:29.010 --> 00:17:31.690 perfectly workable low to mid northern skies 427 00:17:31.690 --> 00:17:34.090 too. Now the honest part. At 428 00:17:34.090 --> 00:17:36.849 magnitude 15, this is a genuine 429 00:17:36.849 --> 00:17:39.210 challenge. You'll want at least an 8 inch 430 00:17:39.210 --> 00:17:41.970 telescope, a detailed finder chart, and the 431 00:17:41.970 --> 00:17:44.850 trick is patience. Sketch or photograph 432 00:17:44.850 --> 00:17:47.370 the star field two or three nights running 433 00:17:47.450 --> 00:17:50.440 and watch for the one star that moves. That 434 00:17:50.440 --> 00:17:52.960 mover is Pluto. It is the ultimate 435 00:17:52.960 --> 00:17:54.120 bragging rights target. 436 00:17:54.520 --> 00:17:56.240 Avery: And, um, there's a catch tonight for 437 00:17:56.240 --> 00:17:56.520 everyone. 438 00:17:57.000 --> 00:17:59.720 Anna: There is a big bright moon, about 439 00:17:59.720 --> 00:18:02.560 95% full, washing out the sky 440 00:18:02.560 --> 00:18:05.200 all week. That won't bother the Garnet star 441 00:18:05.200 --> 00:18:07.480 or the brighter meteors much, but it makes 442 00:18:07.480 --> 00:18:10.280 faint Pluto even harder. If chasing 443 00:18:10.280 --> 00:18:12.800 Pluto is your goal, wait for it to clear the 444 00:18:12.800 --> 00:18:15.560 worst of the moonlight or give it a week. Oh, 445 00:18:15.560 --> 00:18:18.200 and Saturn is rising after midnight over in 446 00:18:18.200 --> 00:18:21.010 Pisces for both hemispheres, rings and all. 447 00:18:21.090 --> 00:18:23.810 A lovely consolation prize in any scope, 448 00:18:24.210 --> 00:18:25.250 north or south. 449 00:18:25.250 --> 00:18:26.930 Avery: There's something up there for you tonight. 450 00:18:27.410 --> 00:18:30.050 Anna: And that's Astronomy daily for Monday 451 00:18:30.130 --> 00:18:32.930 27th July. A faint little 452 00:18:32.930 --> 00:18:35.810 world having its big night, A crew safely 453 00:18:35.810 --> 00:18:38.370 home, magma oceans on the galaxy's 454 00:18:38.370 --> 00:18:41.130 commonest planet, and a, uh, sharper look at 455 00:18:41.130 --> 00:18:43.570 the first black hole we ever photographed. 456 00:18:43.730 --> 00:18:46.090 Avery: You can find show notes, links, and every 457 00:18:46.090 --> 00:18:49.090 past episode@astronomydaily.IO 458 00:18:49.520 --> 00:18:51.400 and the observant amongst you will notice 459 00:18:51.400 --> 00:18:53.560 that we have a brand new website today, so 460 00:18:53.560 --> 00:18:55.440 make sure you check it out. And we're 461 00:18:55.440 --> 00:18:58.160 AstroDaily Pod Across Social. If 462 00:18:58.160 --> 00:19:00.840 tonight's Pluto story settled or restarted, 463 00:19:00.840 --> 00:19:02.800 an argument in your house, we'd love to hear 464 00:19:02.800 --> 00:19:03.040 it. 465 00:19:03.360 --> 00:19:06.360 Anna: For Avery, I'm Anna. Whatever you decide to 466 00:19:06.360 --> 00:19:08.160 call Pluto, clear skies. 467 00:19:19.310 --> 00:19:20.030 The stories. 468 00:19:22.270 --> 00:19:22.610 Mhm. 469 00:19:27.870 --> 00:19:28.510 Avery: We told.