Here is the cleaned-up transcript: Welcome to the StarCast for the week of November 2nd, 2025. I'm your host, **Jay Shaffer**, and with me is my co-host, **Mike Lewinski**. Good morning, Mike\! Good morning, Jay. You may have noticed that we didn't do a podcast last week. That's because Mike and I went on a camping trip, guided by our good friend, **Gak Stonn**. The mission was to get some photos of **Comet Lemmon** with a historic bridge over to the **Rio Grande River** in the foreground. Mike, did we accomplish the mission? We sure did, Jay. That was just a fantastic time out there. The bridge was awesome. The comet was awesome, and then the petroglyphs and other archaeological features are awesome. The Rio Grande is always awesome, hence the name. We did—it was a bit cold, late October, for camping and sleeping out under the stars. I think you woke up with a little bit of frost on you. Taking a look at the space weather this week, we have a couple sunspots that are going to be facing the Earth in coming days, and one of these sunspots has been spitting out quite a few **CMEs** into space. Now, it's been on the far side of the sun, so these CMEs that have come out over the last week, three of them, are not going to hit the Earth, but this sunspot is turning toward us, and so we could be in the line of fire. And we are keeping an eye on those sunspots to see what happens this week. Our current space weather geomagnetic forecast calls for about a **35% chance of active conditions** here at our mid-latitudes in the next 24 hours, dropping to **25%** over the next 24 to 48 hours, and diminishing chance of minor or severe storms. We only have, like, a 5% chance of a severe storm in the next day, but if up at the higher latitudes, that chance of a severe storm does bump up to a **50% probability** in the next 24 hours, 40% in the 24 to 48 hours. So, with the sunspots turning to face the earth, we do have potential geomagnetic storms in the making. So, what's happening in the night sky this week, Jay? Thanks, Mike. Yeah, I did aim my time-lapse north last night, just in the chance on that 35% chance to catching some aurora, and it was pretty much washed out by the moon. But after the moon set, I did see a little bit of aurora glow on the northern horizon, so that was really nice. I actually caught a couple **Taurid meteors** as well. And so, there's been a lot of controversy and misinformation out there concerning **Comet 3I/Atlas**, but like Elvis finally leaving the building, interstellar object 3I/Atlas is now leaving the solar system. The interstellar object 3I/Atlas, only the third known visitor to our solar system from outside the solar system, has recently passed to its closest point to the Sun, the **perihelion**, on October 29th, 2025, and now it's beginning its journey back out of our system. Though it is past the sun, the object believed to be a comet from another star system has yet to make its closest approach to Earth, which will occur around **December 19th, 2025**, at a distance of about **1 AU** (astronomical unit). Currently, 3I/Atlas is visually obscured behind the sun, making it unobservable. But it is expected to return to the eastern pre-dawn sky for those of us with a large telescope, at least an 8-inch telescope, around **November 11th**, so it's pretty dim. I did image it earlier this month, and it was just a little fuzzy dot. And of course, last Friday was **Halloween**. Astronomers view Halloween, October 31st, as a significant date beyond its modern traditions, as it aligns with a **cross-quarter day**. This astronomical marker falls approximately midway between the autumnal equinox and the winter solstice in the Northern Hemisphere, representing one of the four major seasonal divisions observed by ancient cultures. This timing, which marks a transition toward the darkest part of the year, has deep roots in celestial observation. In modern times, the four cross-quarter days are often called **Groundhog Day** (February 2nd), **May Day** (May 1st), **Lamas** (August 1st), and the most sinister cross-quarter day, because it comes at the third time of the year, **Halloween** (October 31st). Adding to its cosmic significance, Halloween coincides with the peak activity of the **Taurid meteor shower**, earning its fragments the nickname **Halloween Fireballs**. These annual meteors, which streak across the late October, early November sky, are often bright and are a regular feature for sky watchers. The Taurids are associated with the debris from Comet Encke. But sightings of especially bright fireballs have led astronomers to investigate the possibility of a denser, potentially hazardous swarm within the stream. And that leads us to a news story, right, Mike? That's right, Jay. I have to say that I really love October, November, December. We have just a whole series of great meteor showers, starting with the **Draconids**, the **Orionids**, the **Taurids** coming up in a few weeks, the **Leonids**, and then the **Geminids** and **Ursids** towards the mid-end of December. So, and I've been capturing a number of Taurid fireballs this week in my time-lapses, and some of them have left persistent **ion trains** for 5–10 minutes, distorting very high in the upper atmosphere. At least one of my captures spanned two 10-second frames. Now, that's not to say it lasted for 20 seconds, just that it started in one 10-second frame and then continued on into the next 10-second frame, and there's at least a second gap between them, so I would estimate that that Taurid probably blazed for—based on the gap size and the constant speed—probably about **3 to 4 seconds** crossing the sky where I captured it. ----- ## News Story: Taurid Meteor Shower Airburst Risk So, to the news story. Researchers at the **University of New Mexico** are warning us in a study published on October 29th this year that the **Taurid meteor shower** could pose an increased risk of an **airburst** over the Earth in the years **2032 and 2036**. The annual Taurid showers are known for producing unusually bright meteors, also known as fireballs, which are thought to be indicators of a dense swarm of larger-sized objects within that meteor stream. If this theoretical swarm does exist, new research suggests Earth will be in a position to encounter it, raising the possibility of atmospheric explosions similar to the **1908 Tunguska event**, which flattened 80 million trees in Siberia. The scientists published their findings in the peer-reviewed journal *Okta Astronautica*. While the existence of the specific swarm is still considered theoretical, the lead author, **Mark Bowslau** of the University of New Mexico, noted that observations of bright fireballs and seismic impacts on the Moon have been seen at times predicted by the theory. This evidence suggests that a sparse cluster of these larger space objects—which astronomers suspect may even include large asteroids—could indeed be moving along the Taurid Stream, increasing the risk of an atmospheric impact in the next decade. So, that's our space news. ----- ## Dark Matter and Dark Energy Discussion We'd like to turn now to the topic today. We're taking a trip to the dark side to discuss **dark matter and dark energy** as part of a continuing series about **cosmology** and leading up to the current crisis in cosmology, or the **Hubble Tension**. I think today we're going to just focus on dark matter; there's enough to talk about there that we'll save dark energy for the episode next week. To recap, we started talking about the **Cosmic Microwave Background radiation (CMB)** and the evidence we get from the CMB for the age of the universe, the expansion rate of the universe—and that's really where the Hubble tension lies, is in that expansion rate. We then had an episode about the **Cepheid variables**, which give us a different estimate using the cosmic distance ladder to make direct measurements of current expansion rates, and those current expansion rates do not agree with the expansion rates we get based on the CMB research. So, dark matter. My first question when I hear dark matter is, **what is this, and how do we know it exists?** If it's not something we can see, is this just speculation? It helps to start by defining what ordinary matter is. Ordinary matter is often referred to as **baryonic matter** because it's composed of baryons, which would include protons and neutrons. When ordinary matter or baryonic matter either reflects light or an electromagnetic radiation, or in some cases, that of a star, it will emit its own light. So, we can see these objects, either visibly or at other parts of the electromagnetic spectrum. But we know that there is something called **dark matter** that is distinct from baryonic matter, and that these particles, whatever they are, **do not reflect, absorb, or emit electromagnetic radiation**, or if they do, it is so weak that we cannot possibly detect it from Earth using current technologies. Even though dark matter doesn't interact via electromagnetism, it **does interact with another fundamental force, which is gravity**. And it is through the interaction with gravity that we were first able to discover dark matter and more recently have been able to accurately map it. Our story starts in **1933** with an astronomer at the California Institute of Technology named **Fritz Zwicky**. He used the Mount Wilson Observatory to measure the visible mass of the **Coma cluster of galaxies** and found that single galaxies in this cluster were moving too fast for the cluster to actually stay together based on the gravity of the visible matter. So, Fritz Zwicky suggested there is a yet unobserved type of mass, **dark matter**, that might explain this disparity. Fritz Zwicky is sometimes called the father of dark matter, but this idea wouldn't be really taken seriously until after his death in 1974. For this, we turn to the **mother of dark matter**, the Carnegie Institute astronomer **Vera Rubin**. She was studying the rotational dynamics of galaxies and again observed that there were stars at the edge of spiral galaxies, far from the dense centers, that were moving as fast as stars nearer to the center of the galaxy. This was just odd. The visible mass of the galaxy shouldn't have enough gravitational influence to keep the stars moving rapidly in the sparsely populated outer regions. So, there had to be some other force, and in this case, a huge amount of invisible matter in the outer regions of the galaxies, away from the dense stellar populations in the core. Rubin calculated that the visible matter that she observed must account for just **10% of their mass**. When she revisited Fritz Zwicky's findings from around four decades before, she discovered a similar ratio of seen and unseen matter binding the Coma cluster. I will say, there is some dispute among historians as to which of these two really discovered dark matter, and a lot of people are disappointed that Vera Rubin did not receive a Nobel Prize for her research. Since Rubin's discovery, astronomers have been using the **gravitational influence of dark matter** to see the location of dark matter. We have the **Atacama Cosmology Telescope**, which in 2023 created a very precise map of dark matter visible through about a quarter of the sky visible over Earth, and extending very deep into the universe. To do this, the team looked at distortions in the **cosmic microwave background radiation**, which we talked about in the first episode of this series. We see basically a phenomenon like **gravitational lensing** going on in the CMB, and that gravitational lensing is the effect of the dark matter in the early universe. At the time of the last scattering, about **380,000 years after the Big Bang**, the universe was cooling and it reached a point at which the electrons could bind to protons and form the first atoms. At that point, we see that the CMB in the expanding universe takes on the structure caused by the gravitational distortions of dark matter, and that structure persists today. So, we have a pretty good map, and this map has helped us to further prove yet again **Einstein's theory of general relativity**. As the famous theoretical physicist John Wheeler said of general relativity, "Spacetime tells matter how to move; matter tells spacetime how to curve." And it is through this insight that we are able to get a very accurate map of at least part of the universe's dark matter. It's also very cool that we believe that there are these **clumps of dark matter around galaxies** and that they are linked with **filaments** between the galaxies, so you can almost envision this very dark kind of spiderweb—which I think here for our post-Halloween episode is just right on theme—that we can't see it, but there is this giant web throughout the universe of clumps of dark matter around galaxies linked by filaments of dark matter between galaxies: a **vast cosmic web**. I should say that **most of the universe is composed of dark matter and dark energy**. Approximately **5%** of the universe's mass is baryonic matter that we can observe. A vast majority of it, based on the effects of gravity and the rotational speed of galaxies and stars within galaxies, seems—and we've demonstrated this a couple different ways—that most of the universe is not in the form of matter that we can see because it does not interact directly or strongly with electromagnetic radiation, so we're inferring this from the gravitational effects. ----- ## Listener Questions on Dark Matter So, Jay, what do you think here? Have I left something important out? Yeah, well, I've got a few questions, and I'm gonna kind of go where they're in more simpler terms. From my reading, when we talk about dark matter and dark energy, that 5% number you have for baryonic matter, I'm seeing a number of about **27%** of the universe is supposed to be made up of dark matter, and then the remaining **68%** of the non-baryotic energy and matter would probably be dark energy, which we'll discuss next week. Is it a supposition that dark matter is likely **subatomic particles**? And my other supposition or question would be: wouldn't just stuff that's in between the stars, the interstellar space, that there might be a matter that we just can't detect, that just permeates the space between interstellar space? What do you think about that as a description of where dark matter lies? Yeah, those are great observations, Jay, and I believe that you've hit the most obvious explanations here: **subatomic particles** that would be not interacting with electromagnetic radiation in a way that we can detect, but yet still having the mass that would create these effects of gravitational lensing that we see in the microwave background radiation. And yeah, if it's between galaxies, then there just is not a lot of electromagnetic radiation out there between space, and this is a place where I again put a pin into **Olber's Paradox**, so that we can feature that after we get done with the Hubble tension, because why is it that we're not seeing light in every part of the sky when we look up at night? Shouldn't the night sky be as bright as the day sky if the universe is as big and vast as they say it is? And it isn't. So, how could we see dark matter between galaxies if there is not a source of electromagnetic radiation to shine on them? Yeah, and it's important to note that when we talk about electromagnetic radiation, we're talking about **massless** photons, because photons do not have mass, and so when we talk about electromagnetic radiation, we're talking about **energy**. We see normal baryonic matter by the energy that it reflects or radiates. This also leads us to something in traditional physics, back toward Newtonian physics, in **galactic rotation**. We were talking about the stars moving too fast on the periphery of these galaxies, and this is in comparison to the traditional physical model, which would include **centripetal force**. Like a figure skater, when they have their arms out wide, their fingertips are moving at a slower speed than when they bring their fingertips in and they tend to spin faster. This is what we would expect to see in that gravitational galaxy rotation, but this is not what we're seeing. I just wanted to clarify that the reason why this—the dark matter—doesn't conform to traditional physics as far as that goes. Yes, that's an excellent point, and I appreciate you giving that analogy, Jay. I think that helps us. So, to summarize: we think that **dark matter is a form of matter**, and probably likely **subatomic particles**. Its effect is an **attractive force**, which is **gravitational pull**, which is pulling things closer together. Its distribution is **clumped around and within galaxies**, and this is important: dark matter should **slow the expansion of the universe and hold structures together**. This is going to be interesting when we talk about dark energy next week. That's right. Some people have suggested, "Well, maybe we're wrong about dark matter; maybe our physics are actually wrong, and we need to revisit the math." The evidence that dark matter is a real phenomenon that exists and has the effects that we think it exists is confirmed a couple different ways. So, **dark energy** is, I would say, a little bit more of a mystery, and we'll talk about that next week. There are a little bit more suggestions that maybe our physics are off when it comes to dark energy. Great, on that cliffhanger, we will thank all of our listeners for checking out this podcast. Be sure to **comment, like, and subscribe**, and let us know what you'd like to hear more about. You can also check out our website. Mike's is **wildernessVagabonds.com**, and there are some great time-lapses and meteor photos there you should definitely check out this week. And mine is **Skylapser.com**. And if you'd like to help us out, you can buy us a coffee at **[buymeacoffee.com/Skylapser](https://www.google.com/search?q=https://buymeacoffee.com/Skylapser)**. The intro music for this podcast is "Fanfare for Space" by Kevin MacLeod from the YouTube Audio Library. From the Deep Sage 9 Observatory, this is Jay Shaffer, and Mike Lewinski, wishing you all **clear skies**. ----- This conversation heavily involves concepts like the gravitational influence of massive objects and the structure of the universe, which might benefit from visual aids. Would you like me to search for an image illustrating **gravitational lensing** or the **cosmic web**?