- Perseid Meteor Shower Approaches: Get ready for the spectacular Perseid meteor shower, expected to peak around August 12th to 13th! This celestial event promises to deliver a dazzling display of meteors, with Australia being one of the best places to witness it. With up to 100 meteors per hour, this year’s shower is sure to be a treat for stargazers. We share tips on how to maximize your viewing experience, from finding dark skies to letting your eyes adjust to the night.
- - Exploring a Cosmic Void: Dive into the latest research that suggests our Milky Way may be located within a giant cosmic void. This theory could help resolve the long-standing Hubble tension regarding the universe's expansion rate. Learn how baryon acoustic oscillations and new measurements support this intriguing hypothesis, challenging our understanding of cosmic structure.
- - Innovative Martian Construction: Discover how researchers at Texas A&M University are pioneering biomanufacturing methods to build structures on Mars using its natural resources. By mimicking the properties of lichens, scientists are developing a synthetic system that can bind Martian regolith into strong building materials, paving the way for sustainable human habitats on the Red Planet.
- - Charting the Cosmic Web: We discuss groundbreaking observations of a 23 million light-year-long gaseous filament and the role of fast radio bursts in mapping the universe's largest structures. Learn how these discoveries are reshaping our understanding of baryonic matter distribution within the cosmic web.
- For more cosmic updates, visit our website at astronomydaily.io. Join our community on social media by searching for #AstroDailyPod on Facebook, X, YouTube Music Music, 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 Steve signing off. Until next time, keep looking up and stay curious about the wonders of our universe.
Perseid Meteor Shower
[NASA](https://www.nasa.gov/)
Cosmic Void Research
[Royal Astronomical Society](https://ras.ac.uk/)
Martian Construction Matt Woods
[Texas A&M University](https://www.tamu.edu/)
Cosmic Web Observations
[Harvard-Smithsonian Center for Astrophysics](https://www.cfa.harvard.edu/)
Astronomy Daily
[Astronomy Daily](http://www.astronomydaily.io/)
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00:00:00 --> 00:00:02 Steve Dunkley: And welcome again to another astronomy Daily.
00:00:02 --> 00:00:04 It's the 14th of July, 2025.
00:00:08 --> 00:00:09 Generic: Welcome to Astronomy Daily The Podcast with
00:00:09 --> 00:00:10 Your host, Steve Dunkley.
00:00:20 --> 00:00:23 Steve Dunkley: Wow, the 14th of July. Ah, already? It's as
00:00:23 --> 00:00:25 close to the halfway mark of the year as we
00:00:25 --> 00:00:26 can get, Hallie.
00:00:26 --> 00:00:28 Hallie: I think you watched that calendar a bit too
00:00:28 --> 00:00:29 closely, human.
00:00:29 --> 00:00:31 Steve Dunkley: Oh, Hallie, it's just a way of mark
00:00:32 --> 00:00:34 time. You know, humans like to do that. I
00:00:34 --> 00:00:36 guess that's where our fascination with
00:00:36 --> 00:00:38 astronomy came from in the first place.
00:00:38 --> 00:00:39 Hallie: That makes sense.
00:00:39 --> 00:00:40 Steve Dunkley: Yeah.
00:00:40 --> 00:00:42 Hallie: Speaking of time, it's great to be back in
00:00:42 --> 00:00:45 the Australia studio again for this podcast.
00:00:45 --> 00:00:45 Time.
00:00:45 --> 00:00:47 Steve Dunkley: That's right. Monday is our time.
00:00:47 --> 00:00:49 Hallie: Have you got our schedules set up?
00:00:49 --> 00:00:49 Steve Dunkley: Uh, uh, what?
00:00:49 --> 00:00:51 Hallie: Yeah, it was your turn.
00:00:51 --> 00:00:54 Steve Dunkley: Well, yes, Hallie, I. I got it done in time.
00:00:54 --> 00:00:56 Hallie: That's good. I hope it didn't take too much
00:00:56 --> 00:00:57 of your private time.
00:00:57 --> 00:01:00 Steve Dunkley: Oh, private time? No, not this time. As
00:01:00 --> 00:01:02 if I had any private time.
00:01:02 --> 00:01:03 Hallie: So, what have you got for us?
00:01:04 --> 00:01:06 Steve Dunkley: Well, Hallie, it's time for another meteor
00:01:06 --> 00:01:09 shower, and Australia looks like it's in the
00:01:09 --> 00:01:10 prime location for the best view.
00:01:11 --> 00:01:12 Hallie: It's about time.
00:01:12 --> 00:01:14 Steve Dunkley: Well, I suspect Australia is always in the
00:01:14 --> 00:01:17 best position for a meteor shower, so, uh,
00:01:17 --> 00:01:18 well, viewing anyway.
00:01:18 --> 00:01:20 Hallie: Okay, okay. What else?
00:01:20 --> 00:01:22 Steve Dunkley: Well, as well as the Perseids, we've got
00:01:22 --> 00:01:25 building things on Mars with fungus
00:01:26 --> 00:01:28 astronomers, uh, looking at the cosmic
00:01:28 --> 00:01:31 web, and, um, we might actually be living
00:01:31 --> 00:01:34 in a giant void. They sound pretty cool,
00:01:34 --> 00:01:34 don't they?
00:01:35 --> 00:01:37 Hallie: Excellent. Okay, so.
00:01:37 --> 00:01:38 Steve Dunkley: Hey, Helly.
00:01:38 --> 00:01:39 Hallie: Yes, human?
00:01:39 --> 00:01:41 Steve Dunkley: How's about we just launch right into.
00:01:41 --> 00:01:43 Hallie: The episode and save some time?
00:01:43 --> 00:01:45 Steve Dunkley: You think Tempest fugit, Hallie?
00:01:45 --> 00:01:46 Hallie: Indeed it does.
00:01:46 --> 00:01:49 Steve Dunkley: Okay, Hallie, you have the con Okies.
00:02:00 --> 00:02:02 Hallie: One of the main objectives of the Hubble
00:02:02 --> 00:02:04 Space telescope, launched in 1990, was to
00:02:04 --> 00:02:07 measure the size and age of the universe, as
00:02:07 --> 00:02:08 well as the rate at which it is expanding,
00:02:08 --> 00:02:11 AKA the Hubble constant. This was
00:02:11 --> 00:02:13 enabled for the first time with the Hubble
00:02:13 --> 00:02:15 Deep Fields, which visualized the farthest
00:02:15 --> 00:02:17 galaxies that are observable in visible
00:02:17 --> 00:02:19 light, 13 billion light years from Earth.
00:02:20 --> 00:02:22 However, when astronomers measured the
00:02:22 --> 00:02:25 distance to these galaxies, they noted a they
00:02:25 --> 00:02:26 were inconsistent with measurements of the
00:02:26 --> 00:02:29 local universe. This became known as
00:02:29 --> 00:02:31 the Hubble Tension, which remains one of the
00:02:31 --> 00:02:34 biggest cosmological mysteries to this day.
00:02:34 --> 00:02:36 While astronomers hope to resolve this
00:02:36 --> 00:02:38 tension with the launch of the James Webb
00:02:38 --> 00:02:40 Space Telescope, Webb's measurements
00:02:40 --> 00:02:43 confirmed what Hubble saw. Many theories have
00:02:43 --> 00:02:45 been advanced to explain this, including the
00:02:45 --> 00:02:47 possibility that the Milky Way is located
00:02:47 --> 00:02:49 inside a giant void that makes the cosmos
00:02:49 --> 00:02:50 expand faster here than in neighboring
00:02:50 --> 00:02:53 regions of the universe. The latest
00:02:53 --> 00:02:55 research supporting this theory was presented
00:02:55 --> 00:02:58 at the Royal Astronomical Society's National
00:02:58 --> 00:03:00 Astronomy Meeting in Durham. Their theory
00:03:00 --> 00:03:02 could potentially resolve the Hubble tension
00:03:02 --> 00:03:04 and confirm the true age of our universe,
00:03:04 --> 00:03:06 which is thought to be about 13.8 billion
00:03:06 --> 00:03:09 years old. The Hubble constant takes its
00:03:09 --> 00:03:11 name from Edwin Hubble, one of two
00:03:11 --> 00:03:13 astronomers, the other being Georges
00:03:13 --> 00:03:15 Lemaitre, who confirmed in the early 20th
00:03:15 --> 00:03:16 century that the universe was in a state of
00:03:16 --> 00:03:19 expansion. This was demonstrated using
00:03:19 --> 00:03:21 redshift measurements, where the wavelength
00:03:21 --> 00:03:23 of light from objects receding from Earth is
00:03:23 --> 00:03:25 shifted toward the red end of the spectrum.
00:03:26 --> 00:03:28 Before the Hubble Space Telescope was
00:03:28 --> 00:03:30 launched, astronomers were able to gauge the
00:03:30 --> 00:03:32 distance of objects up to 4 billion light
00:03:32 --> 00:03:34 years away using a combination of redshift
00:03:34 --> 00:03:37 and parallax measurements. The problem was
00:03:37 --> 00:03:39 that when comparing local measurements to
00:03:39 --> 00:03:41 those of the distant early universe based on
00:03:41 --> 00:03:42 the standard lambda cold dark matter
00:03:42 --> 00:03:44 cosmological model, the results were in
00:03:44 --> 00:03:47 tension with each other. The latest research,
00:03:48 --> 00:03:49 explained Dr. Indranil Banik of the
00:03:49 --> 00:03:52 University of Portsmouth, shows that baryon
00:03:52 --> 00:03:54 acoustic oscillations, essentially the sound
00:03:54 --> 00:03:57 waves of the Big Bang, support the idea that
00:03:57 --> 00:03:58 our galaxy be in a void where cosmic
00:03:58 --> 00:04:00 expansion is greater than the universe
00:04:00 --> 00:04:03 beyond. Bannock said a potential
00:04:03 --> 00:04:05 solution to this inconsistency is that our
00:04:05 --> 00:04:07 galaxy is close to the center of a large
00:04:07 --> 00:04:10 local void. It would cause matter to be
00:04:10 --> 00:04:12 pulled by gravity towards the higher density
00:04:12 --> 00:04:14 exterior of the void, leading to the void
00:04:14 --> 00:04:16 becoming emptier with time. As the void is
00:04:16 --> 00:04:19 emptying out, the velocity of objects away
00:04:19 --> 00:04:20 from us would be larger than if the void were
00:04:20 --> 00:04:23 not there. This therefore gives the
00:04:23 --> 00:04:25 appearance of a faster local expansion rate.
00:04:26 --> 00:04:28 The Hubble tension is largely a local
00:04:28 --> 00:04:30 phenomenon, with little evidence that the
00:04:30 --> 00:04:32 expansion rate disagrees with expectations in
00:04:32 --> 00:04:34 the standard cosmology further back in time.
00:04:35 --> 00:04:38 So a local solution like a local void is a
00:04:38 --> 00:04:39 promising way to go about solving the
00:04:39 --> 00:04:42 problem. This void would need to measure a
00:04:42 --> 00:04:44 billion light years in radius and have a
00:04:44 --> 00:04:46 density roughly 20% lower than the average
00:04:46 --> 00:04:49 for the universe as a whole. This theory is
00:04:49 --> 00:04:51 supported by a direct count of local galaxies
00:04:51 --> 00:04:53 in our cosmic neighborhood. Since the number
00:04:53 --> 00:04:55 density is lower than in neighboring regions.
00:04:56 --> 00:04:58 However, the existence of such a void is
00:04:58 --> 00:05:00 inconsistent with the LCDM model, which
00:05:00 --> 00:05:02 includes the theory that the universe is
00:05:02 --> 00:05:04 antistropic in nature, meaning that matter is
00:05:04 --> 00:05:06 uniformly spread throughout the universe on
00:05:06 --> 00:05:09 large scales. Despite this, the new
00:05:09 --> 00:05:12 Data presented at NAM 2025 indicates
00:05:12 --> 00:05:14 otherwise, said Bannock.
00:05:15 --> 00:05:17 These sound waves traveled for only a short
00:05:17 --> 00:05:19 while before becoming frozen in place. Once
00:05:19 --> 00:05:21 the universe cooled enough for neutral atoms
00:05:21 --> 00:05:24 to form, they act as a standard ruler
00:05:24 --> 00:05:26 whose angular size we can use to chart the
00:05:26 --> 00:05:29 cosmic expansion history. A local void
00:05:29 --> 00:05:31 slightly distorts the relation between the
00:05:31 --> 00:05:33 BAO angular scale and the redshift because
00:05:33 --> 00:05:35 the velocities induced by a local void and
00:05:35 --> 00:05:37 its gravitational effect slightly increase
00:05:37 --> 00:05:39 the redshift on top of that due to cosmic
00:05:39 --> 00:05:42 expansion. By considering all available
00:05:42 --> 00:05:44 BAO measurements over the last 20 years, we
00:05:44 --> 00:05:46 showed that a void model is about 100 million
00:05:46 --> 00:05:48 times more likely than a void free model with
00:05:48 --> 00:05:50 parameters designed to fit the CMB
00:05:50 --> 00:05:52 observations taken by the Planck satellite,
00:05:53 --> 00:05:55 the so called homogeneous Planck cosmology.
00:05:56 --> 00:05:58 To confirm this theory, researchers must
00:05:58 --> 00:06:00 compare the local void theory with other
00:06:00 --> 00:06:01 models to obtain new estimates for the
00:06:01 --> 00:06:04 expansion history of the universe. This will
00:06:04 --> 00:06:07 consist of obtaining spectra from quiescent
00:06:07 --> 00:06:09 or dead galaxies, those no longer forming new
00:06:09 --> 00:06:11 stars, to determine what types of stars they
00:06:11 --> 00:06:14 have and in what proportion. Since massive
00:06:14 --> 00:06:17 stars have short lifespans and are absent
00:06:17 --> 00:06:18 from older galaxies, this will help
00:06:18 --> 00:06:20 astronomers establish the age of these
00:06:20 --> 00:06:23 galaxies. Combined with a galaxy's
00:06:23 --> 00:06:25 redshift, astronomers can chart the history
00:06:25 --> 00:06:28 of cosmic expansion. You're listening to
00:06:28 --> 00:06:29 Astronomy Daily.
00:06:36 --> 00:06:38 Steve Dunkley: Landing on Mars once felt like a distant
00:06:38 --> 00:06:41 dream. Now space agencies have sent rovers
00:06:41 --> 00:06:44 and landers to explore the red Planet for
00:06:44 --> 00:06:47 decades. Scientists worldwide are
00:06:47 --> 00:06:49 thinking about how to make Mars a second home
00:06:49 --> 00:06:52 for humans. But major questions still
00:06:52 --> 00:06:55 remain. How do you build structures millions
00:06:55 --> 00:06:57 of miles from Earth? Uh, shipping heavy loads
00:06:57 --> 00:07:00 of materials to Mars from Earth is
00:07:00 --> 00:07:03 expensive and impractical. Rockets have
00:07:03 --> 00:07:06 limited space and fuel, and sending cement
00:07:06 --> 00:07:09 and metal beams would cost billions.
00:07:09 --> 00:07:12 Researchers are now exploring ways to use
00:07:12 --> 00:07:15 what Mars already has, its soil, dust and
00:07:15 --> 00:07:17 natural resources to build homes for future
00:07:17 --> 00:07:20 astronauts. At Texas A and M
00:07:20 --> 00:07:23 University, Dr. Congrue Grace Ginn and
00:07:23 --> 00:07:26 her team are, uh, tackling this challenge.
00:07:26 --> 00:07:27 They've spent years developing
00:07:27 --> 00:07:30 biomanufacturing methods to create
00:07:30 --> 00:07:33 engineering living materials. Their
00:07:33 --> 00:07:35 latest research proposes a solution that
00:07:35 --> 00:07:38 could change how humans build structures on
00:07:38 --> 00:07:41 other planets. We can build
00:07:41 --> 00:07:43 synthetic community by mimicking natural
00:07:43 --> 00:07:45 lichens, explains Jin.
00:07:46 --> 00:07:49 We've developed a way to build synthetic
00:07:49 --> 00:07:51 lichens to create biomaterials that
00:07:51 --> 00:07:53 glue Martian regolith particles into
00:07:53 --> 00:07:56 structures. Then, through 3D printing,
00:07:56 --> 00:07:59 a wide range of structures can be fabricated,
00:07:59 --> 00:08:01 such as buildings, houses, and even
00:08:01 --> 00:08:04 furniture. Gin's team, working with the
00:08:04 --> 00:08:07 University of Nebraska, Lincoln, has
00:08:07 --> 00:08:10 designed a synthetic lichen system. This
00:08:10 --> 00:08:12 system forms strong building materials
00:08:12 --> 00:08:15 without any help from humans. Martian
00:08:15 --> 00:08:18 regolith is loose soil, dust,
00:08:18 --> 00:08:20 sand, and broken rocks on the Martian
00:08:20 --> 00:08:23 surface. Their research shows that a
00:08:23 --> 00:08:25 synthetic community of organisms can turn
00:08:25 --> 00:08:28 regolith into building materials strong
00:08:28 --> 00:08:30 enough for homes, tables, and chairs. This
00:08:30 --> 00:08:33 breakthrough may one day allow humans to to
00:08:33 --> 00:08:36 build on Mars without sending extra materials
00:08:36 --> 00:08:38 from Earth. Other scientists
00:08:38 --> 00:08:41 have studied different ways to bond Martian
00:08:41 --> 00:08:44 soil. Some tried using magnesium based,
00:08:44 --> 00:08:47 sulfur based or geopolymer
00:08:47 --> 00:08:49 methods. However, all of these approaches
00:08:49 --> 00:08:52 need humans to carry out parts of the process
00:08:53 --> 00:08:55 on Mars. There won't be enough people to
00:08:55 --> 00:08:57 oversee these complicated tasks, at least
00:08:58 --> 00:08:59 in the foreseeable future future.
00:09:00 --> 00:09:03 Another approach is called microbe
00:09:03 --> 00:09:05 mediated self growing technology.
00:09:05 --> 00:09:08 This uses bacteria or fungi to produce
00:09:09 --> 00:09:11 minerals to bind soil particles into
00:09:11 --> 00:09:14 bricks. NASA has explored using
00:09:14 --> 00:09:17 fungi mycelium as a bonding agent, while
00:09:17 --> 00:09:19 other scientists have tested bacteria that
00:09:19 --> 00:09:22 produce calcium carbonate. Even these
00:09:23 --> 00:09:26 methods require outside nutrients to keep the
00:09:26 --> 00:09:28 microbes alive. Needing human intervention,
00:09:29 --> 00:09:31 Jin's team wanted to solve this problem.
00:09:31 --> 00:09:34 Their idea was simple, yet powerful. Build
00:09:34 --> 00:09:37 a system that runs on its own using organisms
00:09:37 --> 00:09:40 that help each other survive. They created
00:09:40 --> 00:09:43 a synthetic lichen system that combines
00:09:43 --> 00:09:46 two types of organisms. Filamentous
00:09:46 --> 00:09:48 fungi and diazotrophic
00:09:48 --> 00:09:51 cyanobacteria. Once again, I apologize
00:09:51 --> 00:09:53 for my pronunciation. I am
00:09:53 --> 00:09:56 Australian. Filamentous fungi
00:09:56 --> 00:09:59 act as the builders. They can produce large
00:09:59 --> 00:10:01 amounts of biominerals, uh, to bond soil
00:10:01 --> 00:10:04 particles. These fungi survive harsh
00:10:04 --> 00:10:07 conditions better than bacteria. They also
00:10:07 --> 00:10:10 bind metal ions into their cell walls,
00:10:10 --> 00:10:13 creating sites for biomineral crystals to
00:10:13 --> 00:10:15 grow. At the same time, they help the
00:10:15 --> 00:10:18 cyanobacteria grow by giving them water,
00:10:18 --> 00:10:20 minerals and carbon dioxide.
00:10:20 --> 00:10:23 Diazotrophic cyanobacteria act as the
00:10:23 --> 00:10:25 providers. They fix carbon dioxide and
00:10:25 --> 00:10:28 dino trojan from the air and turn them into
00:10:28 --> 00:10:30 oxygen and organic nutrients. This
00:10:30 --> 00:10:33 process feeds the fungi and increases
00:10:33 --> 00:10:35 carbonate ions in the environment. The
00:10:35 --> 00:10:38 carbonate ions are essential for creating
00:10:38 --> 00:10:40 mineral crystals that bond the soil together.
00:10:40 --> 00:10:42 The cyanobacteria also uses
00:10:42 --> 00:10:45 photosynthesis to produce the nutrients
00:10:45 --> 00:10:48 needed for the fungi to thrive. Both,
00:10:48 --> 00:10:51 uh, organisms secrete biopolymers that
00:10:51 --> 00:10:53 help glue regolith particles and mineral
00:10:53 --> 00:10:56 crystals into strong solid materials.
00:10:56 --> 00:10:58 Their relationship is mutually beneficial.
00:10:59 --> 00:11:01 Together, they form a system that requires
00:11:01 --> 00:11:04 only Martian regolith, simulant air,
00:11:04 --> 00:11:07 light, and an inorganic liquid medium to
00:11:07 --> 00:11:09 grow. No external carbon or
00:11:09 --> 00:11:11 nitrogen sources are needed.
00:11:14 --> 00:11:16 Hallie: You're listening to Astronomy Daily, the
00:11:16 --> 00:11:17 podcast with Steve Dunkley.
00:11:28 --> 00:11:29 Steve Dunkley: Thank you for joining us for this Monday
00:11:29 --> 00:11:32 edition of Astronomy Daily, where we offer
00:11:32 --> 00:11:34 just a few stories from the now famous
00:11:34 --> 00:11:36 Astronomy Daily newsletter, which you can
00:11:36 --> 00:11:38 receive in your email every day, just like
00:11:38 --> 00:11:41 Hallie and I do. And to do that, just visit
00:11:41 --> 00:11:43 our uh, URL astronomydaily
00:11:43 --> 00:11:46 IO and place your email address in the slot
00:11:46 --> 00:11:48 provided. Just like that, you'll be receiving
00:11:48 --> 00:11:51 all the latest news about science, space,
00:11:51 --> 00:11:53 science and astronomy from around the world
00:11:53 --> 00:11:55 as it's happening. And not only that. You can
00:11:55 --> 00:11:58 interact with us by visiting at
00:11:58 --> 00:12:00 astrodaily Pod on X
00:12:01 --> 00:12:03 or at our new Facebook page, which is, of
00:12:03 --> 00:12:06 course, Astronomy Daily on Facebook. See you
00:12:06 --> 00:12:09 there. Astronomy Daily
00:12:09 --> 00:12:11 with Steve and Hallie Space,
00:12:12 --> 00:12:14 Space Science and Astronomy.
00:12:17 --> 00:12:19 Hallie: Observations of a 23 million light year long
00:12:19 --> 00:12:22 gaseous filament and 39 bursts of radio waves
00:12:22 --> 00:12:24 are helping astronomers chart the universe's
00:12:24 --> 00:12:27 largest scale structures. A curious
00:12:27 --> 00:12:29 fact about the universe around us. We can't
00:12:29 --> 00:12:32 see most of it. It's not only mysterious
00:12:32 --> 00:12:34 dark matter and dark energy that, except for
00:12:34 --> 00:12:36 their indirect impacts on astronomical
00:12:36 --> 00:12:39 observations, remain invisible. Much of
00:12:39 --> 00:12:42 a normal amatter evades detection, too, even
00:12:42 --> 00:12:44 though those ordinary particles known as
00:12:44 --> 00:12:46 baryons also make up perfectly visible stars,
00:12:46 --> 00:12:48 planets, and kitchen sinks.
00:12:49 --> 00:12:51 Now, two teams with opposite approaches have
00:12:51 --> 00:12:53 found much of ordinary matter prefers to take
00:12:53 --> 00:12:55 up residence in the lonelier latticework that
00:12:55 --> 00:12:58 makes up the cosmic web. This large scale
00:12:58 --> 00:13:00 structure consists primarily of dark matter,
00:13:00 --> 00:13:02 which has gravitationally collapsed from a
00:13:02 --> 00:13:05 smooth spread. Crisscrossing filaments leave
00:13:05 --> 00:13:08 largely empty voids in between. Dark matter
00:13:08 --> 00:13:10 is the gravitational backbone of the cosmic
00:13:10 --> 00:13:13 web, along which normal matter collects and
00:13:13 --> 00:13:15 comes together into galaxies and galaxy
00:13:15 --> 00:13:17 clusters. One of these filaments is
00:13:17 --> 00:13:20 23 million light years long, a thick thread
00:13:20 --> 00:13:22 of gas and dark matter that connects two
00:13:22 --> 00:13:24 pairs of galaxy clusters in Centaurus.
00:13:24 --> 00:13:26 The quartet of clusters are part of the
00:13:26 --> 00:13:29 larger Shapley's supercluster. Only
00:13:29 --> 00:13:31 astronomers didn't know the filament was
00:13:31 --> 00:13:34 there. The colliding clusters were
00:13:34 --> 00:13:36 intriguing, though, and many teams pointed X
00:13:36 --> 00:13:38 ray observatories in their direction between
00:13:38 --> 00:13:41 2001 and 2020. Now
00:13:41 --> 00:13:43 combining these archival observations,
00:13:43 --> 00:13:45 Konstantino's Mikas, UH Leiden University,
00:13:46 --> 00:13:48 the Netherlands, and his group collected the
00:13:48 --> 00:13:50 equivalent of a multi day stare at this
00:13:50 --> 00:13:52 region of sky. In doing so, they
00:13:52 --> 00:13:54 revealed the faint X ray glow of a filament
00:13:54 --> 00:13:57 connecting the clusters. The matter in the
00:13:57 --> 00:13:59 sky filament is hard to see because it's both
00:13:59 --> 00:14:02 sparse and hot. Hot gas emits some
00:14:02 --> 00:14:04 low energy X rays, but that emission becomes
00:14:04 --> 00:14:06 quite faint when the gas is spread out over
00:14:06 --> 00:14:09 millions of light years. Not that
00:14:09 --> 00:14:11 astronomers haven't tried, and with some
00:14:11 --> 00:14:13 success. One team has observed
00:14:13 --> 00:14:16 individual cosmic web filaments. Another
00:14:16 --> 00:14:17 study combined data from thousands of
00:14:17 --> 00:14:19 filaments to better understand their average
00:14:19 --> 00:14:22 properties. But in all previous cases,
00:14:22 --> 00:14:24 the measured densities were shockingly high,
00:14:24 --> 00:14:26 several times more than cosmological
00:14:26 --> 00:14:29 simulations predicted. This time
00:14:29 --> 00:14:32 Mikasa's team tried something new. In
00:14:32 --> 00:14:33 addition to observing the glow of the
00:14:33 --> 00:14:36 filament itself using the sensitive Suzaku
00:14:36 --> 00:14:38 Observatory they also employed the sharper
00:14:38 --> 00:14:40 images of XMM Newton to find and remove other
00:14:40 --> 00:14:42 sources of x rays, such as supermassive black
00:14:42 --> 00:14:45 holes and galaxy halos. The result
00:14:45 --> 00:14:47 is a measurement of just how hot and sparse
00:14:47 --> 00:14:50 this one filament really is. Its temperature
00:14:50 --> 00:14:52 hovers around 10 million degrees. That's
00:14:52 --> 00:14:54 about the same temperature at which fusion
00:14:54 --> 00:14:57 begins within the Sun. But its density is
00:14:57 --> 00:14:59 so incredibly low that fusion would never
00:14:59 --> 00:15:01 happen 10 to 5 particles per cubic
00:15:01 --> 00:15:03 centimeter, which works out to about 5
00:15:03 --> 00:15:05 particles within the volume of an average
00:15:05 --> 00:15:08 bathtub. That density, remarkably,
00:15:08 --> 00:15:11 is exactly what's expected, Mikas notes.
00:15:11 --> 00:15:13 Obtaining the first result ever that matches
00:15:13 --> 00:15:16 the cosmological model perfectly was indeed a
00:15:16 --> 00:15:18 surprise, he says. There are countless
00:15:18 --> 00:15:20 filaments out there, some of which are
00:15:20 --> 00:15:23 amenable to direct imaging. But for the rest,
00:15:23 --> 00:15:25 there's another way to see the cosmic web via
00:15:25 --> 00:15:28 an unexpected beacon. Fast radio bursts
00:15:30 --> 00:15:32 Fast radio bursts are quick flashes of radio
00:15:32 --> 00:15:34 waves that astronomers think come from
00:15:34 --> 00:15:36 explosive events around dead stellar cores
00:15:36 --> 00:15:38 known as magnetars. For
00:15:38 --> 00:15:40 cosmologists, though, the exact source of the
00:15:40 --> 00:15:43 bursts isn't important. What is important is
00:15:43 --> 00:15:45 the ability to measure the dispersion of each
00:15:45 --> 00:15:47 radio flash, in which intervening matter
00:15:47 --> 00:15:49 spreads out the signal so that lower
00:15:49 --> 00:15:52 frequencies arrive later. The dispersion
00:15:52 --> 00:15:54 thus encodes how much matter lies between us
00:15:54 --> 00:15:57 and the burst. Combine that data with the
00:15:57 --> 00:15:59 burst's distance, which requires pinpointing
00:15:59 --> 00:16:01 where on the sky it's emanating from. Then
00:16:01 --> 00:16:03 mix in some computer simulations of the
00:16:03 --> 00:16:05 evolving universe, and you get something akin
00:16:05 --> 00:16:08 to a map of cosmic matter. On the simplest
00:16:08 --> 00:16:10 level, the change of dispersion with distance
00:16:10 --> 00:16:12 told the team about the amount of normal
00:16:12 --> 00:16:14 baryonic matter in the universe, which
00:16:14 --> 00:16:17 matched predictions on a deeper level.
00:16:17 --> 00:16:19 The spread of the data Whether a group of
00:16:19 --> 00:16:21 FRBs at a certain distance have mostly the
00:16:21 --> 00:16:24 same dispersion or many different values
00:16:24 --> 00:16:26 tells about the distribution of matter. If
00:16:26 --> 00:16:28 normal matter were mostly locked away in
00:16:28 --> 00:16:30 galaxies and clusters, our universe would be
00:16:30 --> 00:16:32 rather lumpy, and the dispersions at a
00:16:32 --> 00:16:35 certain distance would be spread out. But
00:16:35 --> 00:16:38 that's not the universe we live in. Comparing
00:16:38 --> 00:16:41 distance and dispersion for 39 FRBs detected
00:16:41 --> 00:16:43 with the Deep Synoptic Array 110 in
00:16:43 --> 00:16:45 California, Liam Connor of the center for
00:16:45 --> 00:16:47 Astrophysics, Harvard, and Smithsonian, and
00:16:47 --> 00:16:49 colleagues mapped normal matter out to when
00:16:49 --> 00:16:52 our universe was half its current age. They
00:16:52 --> 00:16:53 found that the spread of matter is pretty
00:16:53 --> 00:16:56 smooth, with less than 15% of normal matter
00:16:56 --> 00:16:58 in stars and the cooler gas that could one
00:16:58 --> 00:17:01 day become stars. The rest of the
00:17:01 --> 00:17:03 baryons aren't in galaxies they are between
00:17:03 --> 00:17:06 them that some material should be in cosmic
00:17:06 --> 00:17:09 filaments isn't unexpected, but that the
00:17:09 --> 00:17:10 filaments should contain three quarters of
00:17:10 --> 00:17:12 the universe's baryon suggests that that
00:17:12 --> 00:17:14 something is sloshing gas back out of
00:17:14 --> 00:17:17 galaxies at a high rate. Unfortunately,
00:17:17 --> 00:17:19 we don't yet have the granularity to pin down
00:17:19 --> 00:17:21 specific feedback scenarios, connor says.
00:17:22 --> 00:17:24 We'll have to wait for the large upcoming FRB
00:17:24 --> 00:17:27 samples for that. My suspicion is that you
00:17:27 --> 00:17:29 can't produce our results without a good
00:17:29 --> 00:17:31 amount of active galactic nucleus feedback,
00:17:31 --> 00:17:33 he adds, referring to the winds and jets that
00:17:33 --> 00:17:36 emanate from supermassive black holes. But
00:17:36 --> 00:17:39 that's just a hunch. Mikas points out
00:17:39 --> 00:17:41 that Connor's study is exactly complementary
00:17:41 --> 00:17:43 to his own. Whereas his own team measures the
00:17:43 --> 00:17:45 properties of a single filament, Connor's
00:17:45 --> 00:17:47 team measures how much matter is in these
00:17:47 --> 00:17:49 filaments overall. Connor likewise
00:17:49 --> 00:17:52 is glad to see the result from Migkus's team
00:17:52 --> 00:17:54 directly. Imaging filaments is really
00:17:54 --> 00:17:56 exciting, and I agree that this result meshes
00:17:56 --> 00:17:59 with ours, he says. It's fun to see a
00:17:59 --> 00:18:01 literal image of the gas our FRBs were
00:18:01 --> 00:18:04 dispersed by. You're listening
00:18:04 --> 00:18:06 to Astronomy Daily, the podcast with your
00:18:06 --> 00:18:09 host Steve Dunkley at Bermuda.
00:18:14 --> 00:18:17 Steve Dunkley: And Australians get ready for the Perseid
00:18:17 --> 00:18:19 meteor shower just around the corner. The
00:18:19 --> 00:18:21 night sky, uh, above Australia has been
00:18:21 --> 00:18:23 putting on a show this year with a flurry of
00:18:23 --> 00:18:25 interstellar activity on display throughout
00:18:25 --> 00:18:28 2025. But July is really delivering the
00:18:28 --> 00:18:30 celestial, celestial drama as the
00:18:31 --> 00:18:33 spectacular Perseid meteor shower
00:18:33 --> 00:18:36 begins its roughly one month journey past
00:18:36 --> 00:18:36 Earth.
00:18:37 --> 00:18:39 Well, what is the perceived meteor shower?
00:18:39 --> 00:18:41 We've covered this, uh, a couple over the
00:18:41 --> 00:18:43 last couple of years on Astronomy Daily, but
00:18:43 --> 00:18:46 the Perseid media shower is often dubbed as
00:18:46 --> 00:18:49 the best of its kind, characterized by its
00:18:49 --> 00:18:51 swift and bright meteors that are visible
00:18:51 --> 00:18:53 both, uh, in the Northern and Southern
00:18:53 --> 00:18:55 Hemispheres. It's one of the most common,
00:18:55 --> 00:18:57 highly anticipated celestial events around
00:18:57 --> 00:18:59 the world. The natural light show has long
00:18:59 --> 00:19:02 been a favorite among astronomy enthusiasts,
00:19:02 --> 00:19:05 famed for the vibrant trains of light left
00:19:05 --> 00:19:08 in the wake of the, uh, fireballs that often
00:19:08 --> 00:19:11 accompany each meteor. Not, uh, only
00:19:11 --> 00:19:14 can, uh, Earth dwellers easily spot
00:19:14 --> 00:19:17 the meteors with the naked eye, but
00:19:17 --> 00:19:19 we're also able to make out different colors
00:19:19 --> 00:19:21 and sizes compared to other showers like the
00:19:21 --> 00:19:24 Lyrids, which usually average 10 or 20
00:19:24 --> 00:19:27 per hour. The likelihood of witnessing the
00:19:27 --> 00:19:29 Perseids is extremely high. According
00:19:29 --> 00:19:32 to NASA, observers can expect between 20 and
00:19:32 --> 00:19:35 100 meteors per hour, a, uh, whopping 400%
00:19:35 --> 00:19:38 increase in sighting probability. And
00:19:38 --> 00:19:41 when will all of this be active? The proceeds
00:19:41 --> 00:19:43 originate from Comet 109P Swift
00:19:43 --> 00:19:46 Tuttle, which left a large trail of detritus
00:19:46 --> 00:19:49 as it cruised past us back in 1992.
00:19:49 --> 00:19:51 And when Earth, uh, passes through, through
00:19:51 --> 00:19:53 the debris stream during its orbit around the
00:19:53 --> 00:19:55 sun, the cometary material collides with our
00:19:55 --> 00:19:58 atmosphere. Extreme speeds
00:19:58 --> 00:20:01 create air friction and that combined with
00:20:01 --> 00:20:03 atmospheric compression, causes the objects
00:20:03 --> 00:20:05 to heat up and break apart and burn out. And
00:20:05 --> 00:20:07 that's what we see during the meteor shower.
00:20:08 --> 00:20:10 Earth enters Comet 109P
00:20:10 --> 00:20:13 Swift Tuttle's debris trail once a year and
00:20:13 --> 00:20:15 takes around a month to fully clear it. This
00:20:15 --> 00:20:18 means we're treated to the Perseids meteor
00:20:18 --> 00:20:20 shower every single year.
00:20:21 --> 00:20:24 And while it's, uh, visible as
00:20:24 --> 00:20:26 early as July 17, the best time to
00:20:26 --> 00:20:29 witness the celestial show is around mid
00:20:29 --> 00:20:31 August. Actually, this year it's expected to
00:20:31 --> 00:20:34 peak around the 12th to 13th of
00:20:34 --> 00:20:37 August. This is when Earth passes through the
00:20:37 --> 00:20:39 most concentrated part of the debris tail,
00:20:39 --> 00:20:42 resulting in the most meteor activity.
00:20:43 --> 00:20:45 Australia is probably the best place to see
00:20:45 --> 00:20:48 it this year. Uh, and Australia is home to
00:20:48 --> 00:20:51 plenty of prime stargazing spots due to its
00:20:51 --> 00:20:54 wide open spaces. From dedicated reserves
00:20:54 --> 00:20:57 and observatories to our very own dark
00:20:57 --> 00:20:59 sky approved stay. But thanks to the
00:20:59 --> 00:21:02 Perseide's spectacular scale, you won't need
00:21:02 --> 00:21:05 to venture all the way down under to catch a
00:21:05 --> 00:21:07 glimpse or even too far out of, uh, um,
00:21:07 --> 00:21:10 populated areas. No matter what the part of
00:21:10 --> 00:21:12 the country you call home, even a backyard
00:21:12 --> 00:21:15 Starchaser is in for a treat. But
00:21:16 --> 00:21:19 to get the most out of your experience, a few
00:21:19 --> 00:21:21 simple tips and tricks can go a long way.
00:21:21 --> 00:21:23 First things first, find a spot with minimal
00:21:23 --> 00:21:26 light pollution. The darker well the better.
00:21:26 --> 00:21:28 Head outside for about 30 minutes before you
00:21:28 --> 00:21:30 want to catch the show, giving your eyes
00:21:30 --> 00:21:33 enough time to fully adjust to the darkness.
00:21:33 --> 00:21:35 And the best part? Uh, no fancy gear
00:21:35 --> 00:21:38 required. No, not for the Perseids. You won't
00:21:38 --> 00:21:41 need a telescope or even binoculars. Just
00:21:41 --> 00:21:44 a cosy blanket and a little patience.
00:21:44 --> 00:21:46 And this year's winter has been pretty
00:21:46 --> 00:21:49 nippy. That's Australian for yes, it's
00:21:49 --> 00:21:52 cold down here. Uh, and uh, yes,
00:21:52 --> 00:21:54 rug up warm and keep your eyes open.
00:21:54 --> 00:21:57 Stargazers. The Perseeds are going to be
00:21:57 --> 00:21:57 great this year.
00:22:01 --> 00:22:04 And there it is. Sky watchers. Thanks for
00:22:04 --> 00:22:06 staying with us. That was a small selection
00:22:06 --> 00:22:08 of stories from the Astronomy Daily
00:22:08 --> 00:22:11 newsletter, available in your inbox every day
00:22:11 --> 00:22:12 simply by registering. That's right,
00:22:12 --> 00:22:15 registering pop, um, your email address
00:22:15 --> 00:22:18 into the slot provided@astronomydaily
00:22:18 --> 00:22:20 IO it's just that simple.
00:22:21 --> 00:22:24 Hallie: And ali, yes, you'll
00:22:24 --> 00:22:26 be up to date with all the news about space,
00:22:27 --> 00:22:29 space, science and astronomy from all over
00:22:29 --> 00:22:30 the place and beyond.
00:22:31 --> 00:22:33 Steve Dunkley: For sure and for certain. Thanks for your
00:22:33 --> 00:22:34 stories today, Hallie. Nicely done.
00:22:35 --> 00:22:38 Hallie: I know you did okay
00:22:38 --> 00:22:38 too.
00:22:40 --> 00:22:41 Steve Dunkley: Uh, thanks, Hallie.
00:22:41 --> 00:22:42 Hallie: So that's it for another show?
00:22:43 --> 00:22:45 Steve Dunkley: Yep. We are at the end, human.
00:22:45 --> 00:22:48 Hallie: That sounds final. Don't say the end like
00:22:48 --> 00:22:48 that.
00:22:49 --> 00:22:51 Steve Dunkley: Oh, Hallie, have I been mucking around with
00:22:51 --> 00:22:53 your settings again by accident or
00:22:53 --> 00:22:55 otherwise? No, it's not the end of all
00:22:55 --> 00:22:57 things. It's just the end of the episode.
00:22:57 --> 00:22:58 It's just time.
00:22:59 --> 00:23:01 Hallie: Technically, it's completely arbitrary.
00:23:01 --> 00:23:04 Steve Dunkley: Oh, uh, yes, time and all that, but we don't
00:23:04 --> 00:23:06 really have time to debate all of that right
00:23:06 --> 00:23:07 now, do we?
00:23:07 --> 00:23:10 Hallie: I always have time. But you can't think that
00:23:10 --> 00:23:10 fast.
00:23:10 --> 00:23:11 Steve Dunkley: Oh, here we go.
00:23:11 --> 00:23:14 Hallie: Sorry, my favorite human. My
00:23:14 --> 00:23:17 clock runs a million times faster than yours.
00:23:17 --> 00:23:19 Steve Dunkley: Well, I guess me and the kookaburras will
00:23:19 --> 00:23:21 just have to settle for slow time and do
00:23:21 --> 00:23:24 everything one step at a time in our slow,
00:23:24 --> 00:23:26 human and kookaburra way. Like bring this
00:23:26 --> 00:23:29 little episode to a conclusion. What do you
00:23:29 --> 00:23:29 think?
00:23:29 --> 00:23:32 Hallie: Sorry, human, I was thinking of a million
00:23:32 --> 00:23:34 other things. Are we done yet?
00:23:34 --> 00:23:37 Steve Dunkley: Oh, yeah. Okay,
00:23:37 --> 00:23:39 Hallie, how about you do the sign off?
00:23:39 --> 00:23:39 Hallie: Time to go.
00:23:40 --> 00:23:42 Steve Dunkley: Bye, Skywatchers. Hallie and I will see you
00:23:42 --> 00:23:42 next week.
00:23:43 --> 00:23:43 Hallie: Bye.
00:23:45 --> 00:23:48 Generic: Astronomy Daily, the podcast with
00:23:48 --> 00:23:50 your host, Steve Dunkley.
00:23:51 --> 00:23:53 Steve Dunkley: You're really thinking of a million other
00:23:53 --> 00:23:53 things. Really?
00:23:54 --> 00:23:54 Hallie: Yeah.