- Estimating Stars in the Milky Way: Astronomers estimate that our galaxy contains around 100 billion stars, a number that evolves as observational techniques improve. By studying luminosity and mass, scientists refine these estimates, revealing the complexities of counting stars from within our own galaxy.
- Asteroid Rotation Dynamics: New research uncovers why some asteroids spin smoothly while others tumble chaotically. The study highlights the impact of collisions and internal friction, demonstrating how size and composition influence an asteroid's stability and rotation.
- China's Space Program Updates: China's Tiangong Space Station is bustling with activity, having recently completed its fourth spacewalk and preparing for the Shenzhou 21 mission. Additionally, the Tianwen 2 probe is on its way to collect samples from Near Earth asteroid Kamo Oalewa, marking significant advancements in China's space exploration efforts.
- Mysterious Dark Object Detected: Astronomers have detected a dark object through its gravitational effects, potentially a rogue black hole or neutron star. This groundbreaking discovery utilizes microlensing to observe how the object's gravity warps light from distant stars, offering new insights into dark matter and galactic structures.
- For more cosmic updates, visit our website at astronomydaily.io. Join our community on social media by searching for #AstroDailyPod on Facebook, X, YouTubeMusic, TikTok, and our new Instagram account! Don’t forget to subscribe to the podcast on Apple Podcasts, Spotify, iHeartRadio, or wherever you get your podcasts.
- Thank you for tuning in. This is Anna and Avery signing off. Until next time, keep looking up and exploring the wonders of our universe.
Milky Way Star Estimates
[NASA](https://www.nasa.gov/)
Asteroid Research Insights
[European Space Agency](https://www.esa.int/)
China's Space Missions
[China National Space Administration](http://www.cnsa.gov.cn)
Dark Object Detection
[Astrophysical Journal](https://iopscience.iop.org/journal/0004-637X)
Astronomy Daily
[Astronomy Daily](http://www.astronomydaily.io/)
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00:00:00 --> 00:00:02 Anna: Welcome to Astronomy Daily, your regular dose
00:00:02 --> 00:00:04 of the latest happenings in space and
00:00:04 --> 00:00:06 astronomy news. I'm Anna.
00:00:06 --> 00:00:09 Avery: And I'm Avery. We've got a fantastic lineup
00:00:09 --> 00:00:11 for you today. Diving into everything from
00:00:11 --> 00:00:14 the sheer number of stars in our galaxy to
00:00:14 --> 00:00:16 tumbling asteroids, exciting updates from
00:00:16 --> 00:00:19 China's space program, and even the detection
00:00:19 --> 00:00:21 of a truly enigmatic dark object.
00:00:21 --> 00:00:24 Anna: It's going to be a stellar episode. Pun
00:00:24 --> 00:00:24 intended.
00:00:25 --> 00:00:27 Let's kick things off with a question that's
00:00:27 --> 00:00:28 probably. Probably crossed everyone's mind.
00:00:29 --> 00:00:31 Just how many stars are there in the Milky
00:00:31 --> 00:00:31 Way?
00:00:32 --> 00:00:34 Avery: That's a great question, Anna. Uh, and the
00:00:34 --> 00:00:37 answer is more than you can imagine.
00:00:37 --> 00:00:40 Astronomers generally estimate around 100
00:00:40 --> 00:00:43 billion stars in our galaxy. But it's a
00:00:43 --> 00:00:45 number that really depends on a lot of
00:00:45 --> 00:00:46 different factors.
00:00:46 --> 00:00:49 Anna: 100 billion. Wow. And I imagine it's
00:00:49 --> 00:00:50 incredibly difficult to count them from our
00:00:50 --> 00:00:53 vantage point inside the galaxy. Right. All
00:00:53 --> 00:00:54 that dust gets in the way.
00:00:54 --> 00:00:57 Avery: Exactly. It's like trying to count trees from
00:00:57 --> 00:01:00 inside a dense forest. So astronomers
00:01:00 --> 00:01:03 often look to other galaxies, which are
00:01:03 --> 00:01:05 easier to observe as a whole, to develop
00:01:05 --> 00:01:06 their estimation methods.
00:01:07 --> 00:01:09 Anna: One primary method involves studying the
00:01:09 --> 00:01:12 luminosity of galaxies. Astronomers can
00:01:12 --> 00:01:14 estimate the total light output of a galaxy.
00:01:14 --> 00:01:17 And by understanding the typical luminosity
00:01:17 --> 00:01:19 of different star types, they can infer the
00:01:19 --> 00:01:22 total number of stars. This is often combined
00:01:22 --> 00:01:24 with observations of a galaxy's mass inferred
00:01:24 --> 00:01:26 from its rotation speed or the motion of its
00:01:26 --> 00:01:29 stars, as more massive galaxies generally
00:01:29 --> 00:01:32 contain more stars. Another approach
00:01:32 --> 00:01:34 involves analyzing the stellar populations
00:01:34 --> 00:01:37 within representative regions of a galaxy,
00:01:37 --> 00:01:39 then extrapolating those findings to the
00:01:39 --> 00:01:42 galaxy's full extent. While these methods
00:01:42 --> 00:01:44 provide robust estimates, the numbers are
00:01:44 --> 00:01:46 always subject to refinement as our
00:01:46 --> 00:01:49 observational capabilities improve and our
00:01:49 --> 00:01:51 understanding of stellar evolution and
00:01:51 --> 00:01:54 galactic structures deepens. So the
00:01:54 --> 00:01:57 exact number is always evolving, but our
00:01:57 --> 00:01:59 estimates become more precise over time.
00:02:00 --> 00:02:02 Avery: Moving on from the grand scale of galaxies,
00:02:03 --> 00:02:05 let's zoom in to something a bit closer to
00:02:05 --> 00:02:07 home. Asteroids. There's
00:02:07 --> 00:02:10 fascinating new research about why some
00:02:10 --> 00:02:13 asteroids spin smoothly and others
00:02:13 --> 00:02:14 tumble chaotically.
00:02:15 --> 00:02:16 Anna: Yes, this study is really shedding light on
00:02:16 --> 00:02:19 their past. It suggests an asteroid's
00:02:19 --> 00:02:21 rotation is largely determined by how
00:02:21 --> 00:02:23 frequently it's impacted by other space
00:02:23 --> 00:02:25 rocks. Which is quite an intuitive idea when
00:02:25 --> 00:02:26 you think about it.
00:02:26 --> 00:02:29 Avery: Absolutely. And it combines data from ESA's
00:02:29 --> 00:02:32 GAIA mission Advanced Modeling and AI
00:02:32 --> 00:02:35 spearheaded by Dr. Wen Honju from the
00:02:35 --> 00:02:38 University of Tokyo. It's a great example of
00:02:38 --> 00:02:40 interdisciplinary science, revealing the
00:02:40 --> 00:02:43 physics of asteroid rotation and even. Even
00:02:43 --> 00:02:44 their internal structure.
00:02:45 --> 00:02:47 Anna: Uh, what's particularly interesting is the
00:02:47 --> 00:02:50 interplay of two forces, collisions,
00:02:50 --> 00:02:52 which cause the tumbling and internal
00:02:52 --> 00:02:55 friction which tends to stabilize them into a
00:02:55 --> 00:02:58 regular spin. This creates a sort of natural
00:02:58 --> 00:03:00 boundary in asteroid populations.
00:03:00 --> 00:03:03 Avery: That's a fascinating dynamic. So it's a
00:03:03 --> 00:03:05 constant battle between disruptive forces and
00:03:05 --> 00:03:08 stabilizing ones. What does this natural
00:03:08 --> 00:03:11 boundary look like in terms of asteroid size
00:03:11 --> 00:03:13 or composition? Smaller
00:03:13 --> 00:03:16 asteroids, though easily tumbled by impacts,
00:03:16 --> 00:03:19 tend to restabilize relatively quickly due to
00:03:19 --> 00:03:22 their internal friction. It's like they have
00:03:22 --> 00:03:24 a built in dampener for chaotic motion.
00:03:25 --> 00:03:27 Anna: So the larger ones essentially shrug off most
00:03:27 --> 00:03:29 minor collisions, maintaining their steady
00:03:29 --> 00:03:32 spin. It takes a significant hit to disrupt a
00:03:32 --> 00:03:35 truly massive asteroid. It's essentially
00:03:35 --> 00:03:38 a size dependent threshold. For a small
00:03:38 --> 00:03:40 asteroid, even a relatively minor impact can
00:03:40 --> 00:03:43 induce tumbling. But its internal structure
00:03:43 --> 00:03:45 quickly absorbs that energy, Allowing it to
00:03:45 --> 00:03:48 settle back into a predictable spin. For
00:03:48 --> 00:03:50 larger asteroids, their sheer mass and
00:03:50 --> 00:03:52 gravitational integrity mean only a very
00:03:52 --> 00:03:55 substantial energetic collision. Would impart
00:03:55 --> 00:03:57 enough angular momentum to truly destabilize
00:03:57 --> 00:04:00 their rotation for an extended period. And
00:04:00 --> 00:04:02 crucially, this study also confirms the YORP
00:04:02 --> 00:04:05 effect. That's the YORP effect as
00:04:05 --> 00:04:08 a primary driver for rapid rotation in
00:04:08 --> 00:04:10 smaller asteroids. It highlights how
00:04:10 --> 00:04:12 radiation pressure can subtly reshape and
00:04:12 --> 00:04:15 spin up these smaller bodies. Something less
00:04:15 --> 00:04:17 influential on their larger, more massive
00:04:17 --> 00:04:19 counterparts. And in case you're wondering
00:04:19 --> 00:04:22 because I was and looked it up, YORP stands
00:04:22 --> 00:04:24 for Yarkovsky, OKeefe, Radzievsky Paddock.
00:04:25 --> 00:04:27 Honoring four scientists who contributed to
00:04:27 --> 00:04:29 the understanding of these radiation driven
00:04:29 --> 00:04:32 rotational changes in small bodies.
00:04:32 --> 00:04:35 Avery: Thank you. I was going to ask, but that's
00:04:35 --> 00:04:38 a good point about the YORP effect. Could you
00:04:38 --> 00:04:40 elaborate a little more on how that radiation
00:04:40 --> 00:04:42 pressure actually, actually works to spin up
00:04:42 --> 00:04:44 these asteroids? It sounds quite subtle.
00:04:45 --> 00:04:47 Anna: Essentially, as sunlight hits an asteroid, it
00:04:47 --> 00:04:49 absorbs some of the energy and then re emits
00:04:49 --> 00:04:51 it as heat. This re emitted heat carries a
00:04:51 --> 00:04:54 tiny bit of momentum. If the asteroid has an
00:04:54 --> 00:04:56 irregular shape or if its surface properties
00:04:56 --> 00:04:59 vary, it will re emit heat unevenly.
00:04:59 --> 00:05:02 This uneven re emission creates a very small
00:05:02 --> 00:05:05 continuous torque or twisting force. That can
00:05:05 --> 00:05:07 gradually increase or decrease the asteroid's
00:05:07 --> 00:05:09 speed spin rate over long periods. It's a
00:05:09 --> 00:05:12 subtle but powerful effect, Especially for
00:05:12 --> 00:05:14 smaller bodies where their mass is not enough
00:05:14 --> 00:05:16 to resist this gentle push.
00:05:16 --> 00:05:18 Avery: Speaking of important research, let's pivot
00:05:18 --> 00:05:21 to some exciting news from China's space
00:05:21 --> 00:05:23 program. It's truly a dynamic time
00:05:23 --> 00:05:26 with an accelerating launch cadence. And
00:05:26 --> 00:05:28 commercial providers on the verge of their
00:05:28 --> 00:05:29 maiden orbital flights.
00:05:29 --> 00:05:31 Anna: That's fascinating. What's the latest from
00:05:31 --> 00:05:32 the Tiangong Space Station?
00:05:33 --> 00:05:35 Avery: Tiangong has been incredibly busy.
00:05:36 --> 00:05:37 They recently completed their fourth
00:05:37 --> 00:05:40 spacewalk, A significant milestone
00:05:40 --> 00:05:43 they're also preparing for the Shenzhou 21
00:05:43 --> 00:05:45 mission, which will bring new taikonauts to
00:05:45 --> 00:05:48 the station, continuing long duration
00:05:48 --> 00:05:51 scientific experiments. Switching gears
00:05:51 --> 00:05:54 to deep space. New images have just
00:05:54 --> 00:05:57 arrived from Tianwen 2. The probe is on
00:05:57 --> 00:05:59 its way to the Near Earth asteroid Kamo
00:05:59 --> 00:06:02 Oalewa, aiming for a sample return,
00:06:02 --> 00:06:04 which would be a monumental achievement.
00:06:05 --> 00:06:07 And on the commercial front, the competition
00:06:07 --> 00:06:10 is heating up. We're seeing rapid progress in
00:06:10 --> 00:06:13 launch vehicles and engine testing.
00:06:13 --> 00:06:16 Landspace's powerful BF20 engine is
00:06:16 --> 00:06:18 undergoing advanced tests. And Deep Blue
00:06:18 --> 00:06:21 Aerospace's Lightning RS is also making
00:06:21 --> 00:06:24 strides. Galactic Energy's Palace 1
00:06:24 --> 00:06:27 is CAS Space's Lijian 2 and
00:06:27 --> 00:06:30 Orient Space's Yin Li 2 are all nearing their
00:06:30 --> 00:06:33 inaugural flights, promising to significantly
00:06:33 --> 00:06:34 boost China's access to space.
00:06:35 --> 00:06:37 Anna: That's incredible. What about China's crewed
00:06:37 --> 00:06:39 lunar mission plans?
00:06:39 --> 00:06:41 Avery: The Changcheng 10 rocket, crucial for
00:06:41 --> 00:06:44 China's ambitious crewed lunar missions,
00:06:44 --> 00:06:47 recently completed a successful tethered
00:06:47 --> 00:06:50 ignition test. This is a critical step,
00:06:50 --> 00:06:52 demonstrating its propulsion system's
00:06:52 --> 00:06:55 readiness for human spaceflight and
00:06:55 --> 00:06:57 future lunar landings. It really shows
00:06:57 --> 00:07:00 their long term vision and commitment to deep
00:07:00 --> 00:07:03 space exploration. So, as you can see, we
00:07:03 --> 00:07:05 may not hear a lot from the Chinese space
00:07:05 --> 00:07:08 program, but they are making rapid strides
00:07:08 --> 00:07:10 and are far from being idle.
00:07:10 --> 00:07:13 Anna: From ambitious missions to something far more
00:07:13 --> 00:07:15 elusive, astronomers have recently detected
00:07:15 --> 00:07:18 a, uh, mysterious dark object, not by its
00:07:18 --> 00:07:21 light, but purely by its gravitational pull.
00:07:21 --> 00:07:24 This is truly a groundbreaking discovery.
00:07:24 --> 00:07:27 Avery: That's right, Ana. The leading candidates are
00:07:27 --> 00:07:30 indeed a rogue black hole or neutron
00:07:30 --> 00:07:32 star, which are both remnants of massive
00:07:32 --> 00:07:35 stars. However, a less massive
00:07:35 --> 00:07:38 possibility is an isolated brown dwarf,
00:07:38 --> 00:07:41 a failed star that never quite ignited
00:07:41 --> 00:07:44 fusion. The key here is free floating,
00:07:44 --> 00:07:47 meaning it's not gravitationally bound to any
00:07:47 --> 00:07:50 star moving independently through the galaxy.
00:07:50 --> 00:07:53 Anna: That's a fascinating concept, free floating.
00:07:53 --> 00:07:56 So this object is truly isolated, not
00:07:56 --> 00:07:58 orbiting anything. And that's what makes it
00:07:58 --> 00:08:00 so challenging to detect without
00:08:00 --> 00:08:03 gravitational lensing. And this
00:08:03 --> 00:08:06 detection method, known as microlensing, is
00:08:06 --> 00:08:08 truly revolutionary. It works by observing
00:08:08 --> 00:08:11 how the dark object's gravity warps the light
00:08:11 --> 00:08:14 from a background star. As the object passes
00:08:14 --> 00:08:16 in front of the star, it temporarily
00:08:16 --> 00:08:18 brightens the background star's light, acting
00:08:18 --> 00:08:21 like a cosmic magnifying glass. This
00:08:21 --> 00:08:23 technique is incredibly sensitive to objects
00:08:23 --> 00:08:24 that emit no light of their own.
00:08:25 --> 00:08:27 Avery: This discovery is really pushing the
00:08:27 --> 00:08:30 boundaries of what we can detect. It provides
00:08:30 --> 00:08:33 crucial insights into the population of dark
00:08:33 --> 00:08:36 compact objects in our galaxy. Objects that
00:08:36 --> 00:08:38 don't emit light, but whose gravitational
00:08:38 --> 00:08:41 influence is undeniable. It also
00:08:41 --> 00:08:43 helps us refine our models of galactic
00:08:43 --> 00:08:45 structure and, and even gives us clues about
00:08:45 --> 00:08:48 the elusive nature of dark matter, especially
00:08:48 --> 00:08:50 if these objects turn out to be primordial
00:08:50 --> 00:08:51 black holes.
00:08:51 --> 00:08:54 Anna: And that wraps up another fascinating journey
00:08:54 --> 00:08:56 through the cosmos on Astronomy Daily. We've
00:08:56 --> 00:08:58 covered a lot of ground today, from the
00:08:58 --> 00:09:01 incredible dynamics of asteroids to
00:09:01 --> 00:09:03 groundbreaking Chinese space missions and the
00:09:03 --> 00:09:05 mysteries of dark objects.
00:09:06 --> 00:09:07 Avery: And, um, thank you for joining us on
00:09:07 --> 00:09:10 Astronomy Daily. For more space and
00:09:10 --> 00:09:12 astronomy news, be sure to visit our
00:09:12 --> 00:09:15 website@astronomydaily.IO
00:09:15 --> 00:09:17 and check out our continually updating news
00:09:17 --> 00:09:20 feed. Be sure to tune in again tomorrow for
00:09:20 --> 00:09:22 more captivating stories from beyond our
00:09:22 --> 00:09:25 world. Until then, keep looking up.