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.