WEBVTT 0 00:00:00.000 --> 00:00:02.520 Anna: Welcome to Astronomy Daily, your regular dose 1 00:00:02.520 --> 00:00:04.080 of the latest happenings in space and 2 00:00:04.080 --> 00:00:06.080 astronomy news. I'm Anna. 3 00:00:06.560 --> 00:00:09.480 Avery: And I'm Avery. We've got a fantastic lineup 4 00:00:09.480 --> 00:00:11.640 for you today. Diving into everything from 5 00:00:11.640 --> 00:00:14.160 the sheer number of stars in our galaxy to 6 00:00:14.160 --> 00:00:16.800 tumbling asteroids, exciting updates from 7 00:00:16.800 --> 00:00:19.400 China's space program, and even the detection 8 00:00:19.400 --> 00:00:21.680 of a truly enigmatic dark object. 9 00:00:21.840 --> 00:00:24.360 Anna: It's going to be a stellar episode. Pun 10 00:00:24.360 --> 00:00:24.720 intended. 11 00:00:25.280 --> 00:00:27.080 Let's kick things off with a question that's 12 00:00:27.080 --> 00:00:28.810 probably. Probably crossed everyone's mind. 13 00:00:29.210 --> 00:00:31.650 Just how many stars are there in the Milky 14 00:00:31.650 --> 00:00:31.930 Way? 15 00:00:32.890 --> 00:00:34.770 Avery: That's a great question, Anna. Uh, and the 16 00:00:34.770 --> 00:00:37.450 answer is more than you can imagine. 17 00:00:37.770 --> 00:00:40.650 Astronomers generally estimate around 100 18 00:00:40.650 --> 00:00:43.090 billion stars in our galaxy. But it's a 19 00:00:43.090 --> 00:00:45.130 number that really depends on a lot of 20 00:00:45.130 --> 00:00:46.010 different factors. 21 00:00:46.490 --> 00:00:49.010 Anna: 100 billion. Wow. And I imagine it's 22 00:00:49.010 --> 00:00:50.690 incredibly difficult to count them from our 23 00:00:50.690 --> 00:00:53.180 vantage point inside the galaxy. Right. All 24 00:00:53.180 --> 00:00:54.260 that dust gets in the way. 25 00:00:54.660 --> 00:00:57.500 Avery: Exactly. It's like trying to count trees from 26 00:00:57.500 --> 00:01:00.420 inside a dense forest. So astronomers 27 00:01:00.420 --> 00:01:03.060 often look to other galaxies, which are 28 00:01:03.060 --> 00:01:05.580 easier to observe as a whole, to develop 29 00:01:05.580 --> 00:01:06.980 their estimation methods. 30 00:01:07.300 --> 00:01:09.340 Anna: One primary method involves studying the 31 00:01:09.340 --> 00:01:12.140 luminosity of galaxies. Astronomers can 32 00:01:12.140 --> 00:01:14.340 estimate the total light output of a galaxy. 33 00:01:14.340 --> 00:01:17.220 And by understanding the typical luminosity 34 00:01:17.220 --> 00:01:19.610 of different star types, they can infer the 35 00:01:19.610 --> 00:01:22.330 total number of stars. This is often combined 36 00:01:22.330 --> 00:01:24.890 with observations of a galaxy's mass inferred 37 00:01:24.890 --> 00:01:26.970 from its rotation speed or the motion of its 38 00:01:26.970 --> 00:01:29.650 stars, as more massive galaxies generally 39 00:01:29.650 --> 00:01:32.450 contain more stars. Another approach 40 00:01:32.450 --> 00:01:34.810 involves analyzing the stellar populations 41 00:01:34.810 --> 00:01:37.170 within representative regions of a galaxy, 42 00:01:37.410 --> 00:01:39.530 then extrapolating those findings to the 43 00:01:39.530 --> 00:01:42.250 galaxy's full extent. While these methods 44 00:01:42.250 --> 00:01:44.860 provide robust estimates, the numbers are 45 00:01:44.860 --> 00:01:46.820 always subject to refinement as our 46 00:01:46.820 --> 00:01:49.460 observational capabilities improve and our 47 00:01:49.460 --> 00:01:51.900 understanding of stellar evolution and 48 00:01:51.900 --> 00:01:54.780 galactic structures deepens. So the 49 00:01:54.780 --> 00:01:57.460 exact number is always evolving, but our 50 00:01:57.460 --> 00:01:59.660 estimates become more precise over time. 51 00:02:00.220 --> 00:02:02.940 Avery: Moving on from the grand scale of galaxies, 52 00:02:03.100 --> 00:02:05.380 let's zoom in to something a bit closer to 53 00:02:05.380 --> 00:02:07.940 home. Asteroids. There's 54 00:02:07.940 --> 00:02:10.500 fascinating new research about why some 55 00:02:10.500 --> 00:02:13.260 asteroids spin smoothly and others 56 00:02:13.340 --> 00:02:14.460 tumble chaotically. 57 00:02:15.130 --> 00:02:16.850 Anna: Yes, this study is really shedding light on 58 00:02:16.850 --> 00:02:19.490 their past. It suggests an asteroid's 59 00:02:19.490 --> 00:02:21.490 rotation is largely determined by how 60 00:02:21.490 --> 00:02:23.250 frequently it's impacted by other space 61 00:02:23.250 --> 00:02:25.730 rocks. Which is quite an intuitive idea when 62 00:02:25.730 --> 00:02:26.490 you think about it. 63 00:02:26.970 --> 00:02:29.778 Avery: Absolutely. And it combines data from ESA's 64 00:02:29.868 --> 00:02:32.570 GAIA mission Advanced Modeling and AI 65 00:02:32.810 --> 00:02:35.370 spearheaded by Dr. Wen Honju from the 66 00:02:35.370 --> 00:02:38.090 University of Tokyo. It's a great example of 67 00:02:38.090 --> 00:02:40.650 interdisciplinary science, revealing the 68 00:02:40.650 --> 00:02:43.430 physics of asteroid rotation and even. Even 69 00:02:43.430 --> 00:02:44.950 their internal structure. 70 00:02:45.460 --> 00:02:47.470 Anna: Uh, what's particularly interesting is the 71 00:02:47.470 --> 00:02:50.070 interplay of two forces, collisions, 72 00:02:50.230 --> 00:02:52.430 which cause the tumbling and internal 73 00:02:52.430 --> 00:02:55.270 friction which tends to stabilize them into a 74 00:02:55.270 --> 00:02:58.230 regular spin. This creates a sort of natural 75 00:02:58.230 --> 00:03:00.150 boundary in asteroid populations. 76 00:03:00.710 --> 00:03:03.470 Avery: That's a fascinating dynamic. So it's a 77 00:03:03.470 --> 00:03:05.950 constant battle between disruptive forces and 78 00:03:05.950 --> 00:03:08.630 stabilizing ones. What does this natural 79 00:03:08.630 --> 00:03:11.470 boundary look like in terms of asteroid size 80 00:03:11.470 --> 00:03:13.850 or composition? Smaller 81 00:03:13.850 --> 00:03:16.650 asteroids, though easily tumbled by impacts, 82 00:03:16.890 --> 00:03:19.650 tend to restabilize relatively quickly due to 83 00:03:19.650 --> 00:03:22.050 their internal friction. It's like they have 84 00:03:22.050 --> 00:03:24.810 a built in dampener for chaotic motion. 85 00:03:25.530 --> 00:03:27.690 Anna: So the larger ones essentially shrug off most 86 00:03:27.690 --> 00:03:29.890 minor collisions, maintaining their steady 87 00:03:29.890 --> 00:03:32.690 spin. It takes a significant hit to disrupt a 88 00:03:32.690 --> 00:03:35.570 truly massive asteroid. It's essentially 89 00:03:35.570 --> 00:03:38.050 a size dependent threshold. For a small 90 00:03:38.050 --> 00:03:40.610 asteroid, even a relatively minor impact can 91 00:03:40.610 --> 00:03:43.300 induce tumbling. But its internal structure 92 00:03:43.300 --> 00:03:45.820 quickly absorbs that energy, Allowing it to 93 00:03:45.820 --> 00:03:48.380 settle back into a predictable spin. For 94 00:03:48.380 --> 00:03:50.380 larger asteroids, their sheer mass and 95 00:03:50.380 --> 00:03:52.700 gravitational integrity mean only a very 96 00:03:52.700 --> 00:03:55.060 substantial energetic collision. Would impart 97 00:03:55.060 --> 00:03:57.500 enough angular momentum to truly destabilize 98 00:03:57.500 --> 00:04:00.060 their rotation for an extended period. And 99 00:04:00.060 --> 00:04:02.780 crucially, this study also confirms the YORP 100 00:04:02.780 --> 00:04:05.700 effect. That's the YORP effect as 101 00:04:05.700 --> 00:04:08.020 a primary driver for rapid rotation in 102 00:04:08.020 --> 00:04:10.520 smaller asteroids. It highlights how 103 00:04:10.520 --> 00:04:12.640 radiation pressure can subtly reshape and 104 00:04:12.640 --> 00:04:15.280 spin up these smaller bodies. Something less 105 00:04:15.280 --> 00:04:17.160 influential on their larger, more massive 106 00:04:17.160 --> 00:04:19.600 counterparts. And in case you're wondering 107 00:04:19.760 --> 00:04:22.320 because I was and looked it up, YORP stands 108 00:04:22.320 --> 00:04:24.880 for Yarkovsky, OKeefe, Radzievsky Paddock. 109 00:04:25.280 --> 00:04:27.560 Honoring four scientists who contributed to 110 00:04:27.560 --> 00:04:29.880 the understanding of these radiation driven 111 00:04:29.880 --> 00:04:32.080 rotational changes in small bodies. 112 00:04:32.640 --> 00:04:35.600 Avery: Thank you. I was going to ask, but that's 113 00:04:35.600 --> 00:04:38.080 a good point about the YORP effect. Could you 114 00:04:38.080 --> 00:04:40.360 elaborate a little more on how that radiation 115 00:04:40.360 --> 00:04:42.260 pressure actually, actually works to spin up 116 00:04:42.260 --> 00:04:44.860 these asteroids? It sounds quite subtle. 117 00:04:45.180 --> 00:04:47.300 Anna: Essentially, as sunlight hits an asteroid, it 118 00:04:47.300 --> 00:04:49.460 absorbs some of the energy and then re emits 119 00:04:49.460 --> 00:04:51.660 it as heat. This re emitted heat carries a 120 00:04:51.660 --> 00:04:54.260 tiny bit of momentum. If the asteroid has an 121 00:04:54.260 --> 00:04:56.460 irregular shape or if its surface properties 122 00:04:56.460 --> 00:04:59.180 vary, it will re emit heat unevenly. 123 00:04:59.980 --> 00:05:02.380 This uneven re emission creates a very small 124 00:05:02.540 --> 00:05:05.220 continuous torque or twisting force. That can 125 00:05:05.220 --> 00:05:07.415 gradually increase or decrease the asteroid's 126 00:05:07.415 --> 00:05:09.920 speed spin rate over long periods. It's a 127 00:05:09.920 --> 00:05:12.560 subtle but powerful effect, Especially for 128 00:05:12.560 --> 00:05:14.440 smaller bodies where their mass is not enough 129 00:05:14.440 --> 00:05:16.040 to resist this gentle push. 130 00:05:16.520 --> 00:05:18.880 Avery: Speaking of important research, let's pivot 131 00:05:18.880 --> 00:05:21.080 to some exciting news from China's space 132 00:05:21.160 --> 00:05:23.879 program. It's truly a dynamic time 133 00:05:23.880 --> 00:05:26.160 with an accelerating launch cadence. And 134 00:05:26.160 --> 00:05:28.120 commercial providers on the verge of their 135 00:05:28.120 --> 00:05:29.560 maiden orbital flights. 136 00:05:29.880 --> 00:05:31.440 Anna: That's fascinating. What's the latest from 137 00:05:31.440 --> 00:05:32.760 the Tiangong Space Station? 138 00:05:33.250 --> 00:05:35.730 Avery: Tiangong has been incredibly busy. 139 00:05:36.050 --> 00:05:37.930 They recently completed their fourth 140 00:05:37.930 --> 00:05:40.290 spacewalk, A significant milestone 141 00:05:40.690 --> 00:05:43.490 they're also preparing for the Shenzhou 21 142 00:05:43.490 --> 00:05:45.890 mission, which will bring new taikonauts to 143 00:05:45.890 --> 00:05:48.290 the station, continuing long duration 144 00:05:48.370 --> 00:05:51.370 scientific experiments. Switching gears 145 00:05:51.370 --> 00:05:54.050 to deep space. New images have just 146 00:05:54.050 --> 00:05:57.010 arrived from Tianwen 2. The probe is on 147 00:05:57.010 --> 00:05:59.550 its way to the Near Earth asteroid Kamo 148 00:05:59.550 --> 00:06:02.070 Oalewa, aiming for a sample return, 149 00:06:02.310 --> 00:06:04.790 which would be a monumental achievement. 150 00:06:05.590 --> 00:06:07.870 And on the commercial front, the competition 151 00:06:07.870 --> 00:06:10.870 is heating up. We're seeing rapid progress in 152 00:06:10.870 --> 00:06:13.110 launch vehicles and engine testing. 153 00:06:13.350 --> 00:06:16.190 Landspace's powerful BF20 engine is 154 00:06:16.190 --> 00:06:18.750 undergoing advanced tests. And Deep Blue 155 00:06:18.750 --> 00:06:21.510 Aerospace's Lightning RS is also making 156 00:06:21.510 --> 00:06:24.430 strides. Galactic Energy's Palace 1 157 00:06:24.430 --> 00:06:27.320 is CAS Space's Lijian 2 and 158 00:06:27.320 --> 00:06:30.160 Orient Space's Yin Li 2 are all nearing their 159 00:06:30.160 --> 00:06:33.080 inaugural flights, promising to significantly 160 00:06:33.080 --> 00:06:34.560 boost China's access to space. 161 00:06:35.200 --> 00:06:37.760 Anna: That's incredible. What about China's crewed 162 00:06:37.760 --> 00:06:39.040 lunar mission plans? 163 00:06:39.280 --> 00:06:41.920 Avery: The Changcheng 10 rocket, crucial for 164 00:06:41.920 --> 00:06:44.160 China's ambitious crewed lunar missions, 165 00:06:44.480 --> 00:06:47.320 recently completed a successful tethered 166 00:06:47.320 --> 00:06:50.160 ignition test. This is a critical step, 167 00:06:50.320 --> 00:06:52.480 demonstrating its propulsion system's 168 00:06:52.480 --> 00:06:55.040 readiness for human spaceflight and 169 00:06:55.120 --> 00:06:57.940 future lunar landings. It really shows 170 00:06:57.940 --> 00:07:00.860 their long term vision and commitment to deep 171 00:07:00.860 --> 00:07:03.820 space exploration. So, as you can see, we 172 00:07:03.820 --> 00:07:05.980 may not hear a lot from the Chinese space 173 00:07:05.980 --> 00:07:08.700 program, but they are making rapid strides 174 00:07:08.700 --> 00:07:10.460 and are far from being idle. 175 00:07:10.700 --> 00:07:13.100 Anna: From ambitious missions to something far more 176 00:07:13.100 --> 00:07:15.820 elusive, astronomers have recently detected 177 00:07:15.900 --> 00:07:18.620 a, uh, mysterious dark object, not by its 178 00:07:18.620 --> 00:07:21.180 light, but purely by its gravitational pull. 179 00:07:21.660 --> 00:07:24.060 This is truly a groundbreaking discovery. 180 00:07:24.680 --> 00:07:27.120 Avery: That's right, Ana. The leading candidates are 181 00:07:27.120 --> 00:07:30.040 indeed a rogue black hole or neutron 182 00:07:30.040 --> 00:07:32.680 star, which are both remnants of massive 183 00:07:32.680 --> 00:07:35.520 stars. However, a less massive 184 00:07:35.520 --> 00:07:38.520 possibility is an isolated brown dwarf, 185 00:07:38.600 --> 00:07:41.360 a failed star that never quite ignited 186 00:07:41.360 --> 00:07:44.360 fusion. The key here is free floating, 187 00:07:44.520 --> 00:07:47.240 meaning it's not gravitationally bound to any 188 00:07:47.240 --> 00:07:50.120 star moving independently through the galaxy. 189 00:07:50.470 --> 00:07:53.270 Anna: That's a fascinating concept, free floating. 190 00:07:53.750 --> 00:07:56.630 So this object is truly isolated, not 191 00:07:56.630 --> 00:07:58.670 orbiting anything. And that's what makes it 192 00:07:58.670 --> 00:08:00.630 so challenging to detect without 193 00:08:00.630 --> 00:08:03.270 gravitational lensing. And this 194 00:08:03.270 --> 00:08:06.230 detection method, known as microlensing, is 195 00:08:06.230 --> 00:08:08.910 truly revolutionary. It works by observing 196 00:08:08.910 --> 00:08:11.430 how the dark object's gravity warps the light 197 00:08:11.430 --> 00:08:14.430 from a background star. As the object passes 198 00:08:14.430 --> 00:08:16.480 in front of the star, it temporarily 199 00:08:16.480 --> 00:08:18.840 brightens the background star's light, acting 200 00:08:18.840 --> 00:08:21.280 like a cosmic magnifying glass. This 201 00:08:21.280 --> 00:08:23.280 technique is incredibly sensitive to objects 202 00:08:23.280 --> 00:08:24.720 that emit no light of their own. 203 00:08:25.200 --> 00:08:27.360 Avery: This discovery is really pushing the 204 00:08:27.360 --> 00:08:30.160 boundaries of what we can detect. It provides 205 00:08:30.160 --> 00:08:33.160 crucial insights into the population of dark 206 00:08:33.160 --> 00:08:36.160 compact objects in our galaxy. Objects that 207 00:08:36.160 --> 00:08:38.360 don't emit light, but whose gravitational 208 00:08:38.360 --> 00:08:41.160 influence is undeniable. It also 209 00:08:41.160 --> 00:08:43.520 helps us refine our models of galactic 210 00:08:43.520 --> 00:08:45.750 structure and, and even gives us clues about 211 00:08:45.750 --> 00:08:48.510 the elusive nature of dark matter, especially 212 00:08:48.510 --> 00:08:50.710 if these objects turn out to be primordial 213 00:08:50.710 --> 00:08:51.350 black holes. 214 00:08:51.830 --> 00:08:54.110 Anna: And that wraps up another fascinating journey 215 00:08:54.110 --> 00:08:56.990 through the cosmos on Astronomy Daily. We've 216 00:08:56.990 --> 00:08:58.910 covered a lot of ground today, from the 217 00:08:58.910 --> 00:09:01.070 incredible dynamics of asteroids to 218 00:09:01.070 --> 00:09:03.710 groundbreaking Chinese space missions and the 219 00:09:03.710 --> 00:09:05.270 mysteries of dark objects. 220 00:09:06.070 --> 00:09:07.750 Avery: And, um, thank you for joining us on 221 00:09:07.750 --> 00:09:10.390 Astronomy Daily. For more space and 222 00:09:10.390 --> 00:09:12.550 astronomy news, be sure to visit our 223 00:09:12.550 --> 00:09:15.470 website@astronomydaily.IO 224 00:09:15.630 --> 00:09:17.910 and check out our continually updating news 225 00:09:17.910 --> 00:09:20.510 feed. Be sure to tune in again tomorrow for 226 00:09:20.510 --> 00:09:22.510 more captivating stories from beyond our 227 00:09:22.510 --> 00:09:25.070 world. Until then, keep looking up.