Welcome to the StarCast for the week of September 7th, 2025. I'm your host, Jay Shaffer, and with me is my co-host, Mike Lewinski.

Good morning, Mike, how you doing? Ah, just… peaches.

I'm great, how are you, Jay?

We took the week off last week due to you doing a presentation at the Dark Sky Festival in Crestone, Colorado. And I was having technical issues, basically no power at my house, my off-grid house was truly off-grid. So, Mike, how was the festival and your presentation?

I had great fun with my presentation, as I have in previous years. I ended up with about 35 minutes of highlights, heavily weighted toward the first 6 months from August into about January. I have so much good material that once I start combing through it, I fill that timeline really fast, but I started out thinking, "Oh, there wasn't much that happened this year." And I'd forgotten about the kind of Shichu-chan. I had forgotten about the moon occultation of Mars. Of course, the Chinese rocket fuel dump, the lunar eclipse we had back in March. So, there was really a lot more activity, and of course, and I had about 6 instances of aurora that were notable enough that I put them in, so… And we had a great keynote speaker, Professor Shane Burns. He had worked on a team with Saul Perlmutter who were that team. Was given a Nobel Prize for their work in cosmic expansion and determining the fate of the universe, and that was the gist of his presentation, and it was really it was really great, and I got to speak with him for a at length afterwards, and I made a new time-lapse friend. A gentleman who is new professor at Adams State came over and showed me some of his time lapses of Aurora that he took when he was in Southern California before relocating, so… I sent him I gave him some tips on where he could go shoot, and he went out and did some time-lapsing that night after the after the Dark Sky Festival, so… That's always fun.

Okay, great. Hey, speaking of space weather, what's our space weather looking like from SpaceWeather.com this week? Or in the next couple days.

Yeah, so there has been a very strong eruption of plasma, fairly dark plume, so relatively cool and dense, which Space Weather notes is very typical for potent CMEs. And they were predicting that CME today, September 7th, and it does look like their prediction was just about on we hit a KP index of 5 in the last 24 hours, and we're now very quiet at a .67. So, there is a 30% chance of M-Class flares over the next 48 hours. And the probability for a geomagnetic storm here at mid-latitudes is around 35% for the lowest level of storm. We may get to 30% minor probability and 10% severe probability. Of course, if you get up at the higher latitudes severe storm likelihood is upwards of 70%, so it's possible that that CME is not done with us yet. And I'll be looking out there tonight. We're gonna have a little bit clearer weather than we did last night. So, with that said, Jay, what's happening in the night sky this week?

Well, you might have a little bit of trouble seeing the aurora, because today is the full moon, so that actually happened exactly at 2:09 PM Eastern Daylight Time. And the technical term for a full moon is that the moon is in opposition in that it is opposite to the sun. So, if we're looking directly at the moon, just after moonrise, the sun would be directly behind us, although it has just set and is below the horizon, so if you were to draw a straight line through your head between the moon and the sun, that would be it would be in the opposite direction. And so, if you watch tonight's moonrise, Saturn will be visible really close to the Moon, and it will follow it across the sky through the night. And that's no coincidence, because Saturn is just 2 weeks from its own opposition where it will be opposite the sun from our observing point to Saturn. Maybe look for Saturn tonight when you're looking at the big, the nice, beautiful full moonrise. And for our international listeners or listener, however it may be, there is a total eclipse of the moon tonight, and it will occur in easternmost Africa, most of the Middle East and Asia and the Western half of Australia, so if you're in that part of the world, you're gonna get to see a total eclipse of the moon.

I'm jealous.

Now, let's take a look at some space news. Mike?

Yes, Jay. We've got a newly discovered asteroid named 2025PN7, which has been identified as a quasi-moon of Earth. This was found on August 29th by the Pan-STARS Observatory. Object seems to be angular, very elongated, solid rock, about 13 to 33 meters across. It is completing a sort of lopsided orbit, and it goes from as far as 0.4 astronomical units to as close as .03 astronomical units from our planet, and we'll get to talking about AUs in a little bit here. This asteroid has been orbiting the Sun alongside Earth for about 60 years, and is expected to continue doing so at least another 60 years before shifting into a horseshoe orbit. But having such a stable orbit for now makes it a potential target for future low-budget space missions for exploration, or even maybe asteroid mining.

Okay, and we should probably mention that they've kind of discounted that this has very low possibility of actually impacting the Earth, too, so at .03 AU from our from Earth, it's still quite a distance away. And so, today, we're going to talk about astronomical distances and ask the question, is how far away is it? Or how far is it? So, when we talk about distances in space, we also have to kind of talk about time. And so, kind of the first question is what is a second? Which is our puny human basic measurement of time. And so, if we want to base that measurement in any kind of sort of physical reality, we have to base it upon something that happens, basically, objectively, in the universe. And so, atomic clocks use the natural, extremely stable oscillation of atoms to keep time. And the most common atomic clock, and the one that we use to define the international standard of a second, uses the cesium-133 atom. The oscillation in a cesium atom atomic clock it's not a physical movement, but it's a transition of an electron between two very specific energy states, known as hyperfine levels. This transition is triggered by a precise frequency of microwave radiation, and so they can look at that frequency. And so the cesium-133 atom is kind of defined as having a natural frequency. And the International System of Units, or SI, is defines one second as the duration of exactly 9,192,631,770 oscillations of this transition. And so that's what our second is. So.

And Jay, I'd just like to point out how cool it is that in order to measure space, we have to measure time. That there is no we wouldn't be able to measure space without measurements of time, and that is exceptionally, just very cool.

Yeah, and so, I was approaching this a couple weeks ago, when we did our thing about relativity, we discussed relativity, we've touched on that, and that kind of brought spurred my musing about these distances. And I was just going to limit this discussion to just put everything in terms of light seconds, and so when I kind of went down the rabbit hole, it was like, well, if we talk about the speed of light as a constant, and then we talk about how many seconds that takes to travel, we have to look at time and what a second is, and so it's really kind of a second is an invention. But we'll use that invention for our quantification of distance. And so, another, we just talked earlier about the astronomical unit, and we just talked about that in that quasi-moon story. And so, an astronomical unit is defined as the average distance between the center of Earth and the center of the Sun. And it is a fixed value of exactly 149,597,870.2 kilometers. Or about roughly 93 million miles. And so the AU is used by astronomers to express the vast distance in our solar systems in a more manageable way. And so, we can, we can convert between AUs and light seconds, and so if we took a one astronomical unit is approximately 499.05 light seconds, which is equivalent to about 8 minutes and 19 seconds on a clock. And so that is basically the time that it would take for a photon to travel from the center of the Sun to the center of the Earth, at least in theory. And the distance is slightly different than what we use if we use the average distance between the Sun and the Earth's surface. And the average difference between the surface of the sun is approximately 500 light seconds away. That is because light, which travels at a constant speed of 186,000 miles per second, or 300,000 kilometers, it takes about 8 minutes and 20 seconds to travel the average of that distance between the 93 million miles from the sun to the earth. So that means that we're always seeing the sun as it was 500 seconds ago, or just over 8 minutes ago in the past. And so we're looking over a distance. We're actually looking into the past. So if the sun were suddenly to blink out and suddenly vanish, we wouldn't know it, or we wouldn't know that we were dead for about 8 minutes. So, and so now, if we talk about planets, then we can measure the distances between the planets and our Earth using this this kind of light years, light seconds, or light minutes, or light hours, or light months, or light years, and we're kind of use that as a ruler for kind of the nearer distances, so… For example, the moon is about 1.3 light seconds from Earth on average, so that means light from the moon takes about, well, 1.3 seconds to get to us from the moon. And so, when we're, we're when we had people on the moon in the 1970s, when they were talking over the radio to us, there was about a 1.3 second delay between the time that they spoke on the Moon, and we heard it here on Earth, and so that did make conversation a little bit kind of difficult, so imagine you and I talking back and forth, where we could only we'd have to take 2.6 seconds between each one of our conversational. So, just look at our clock real quick, and so I'll say something, and then 2.6 seconds later, you respond, okay, Mike? So, Mike, how are you today?

Hey, Jay, I'm great! How are you?

I'm fine, too, so you can see how that could be kind of that makes communication a little bit awkward, even when we, we're talking about just that mere 1.3 light seconds from Earth. So, let's talk about some of the other planets, just real briefly. Is that Mercury is varies between 3.2 to 13.9 light minutes away. And Venus, which is probably our closest planet is 2.3 to 14 light minutes away. And of course, everybody so let's talk yeah, you wanted to mention a little something about Venus, and since that's our closest planet.

No.

We use that for measurement, is that correct?

That's right. Historically, transits of Venus in front of the Sun were used to calculate the AU. Once we know the relative ratios of orbits of objects, we can begin to, and then we have a distance to an object, we can begin to calculate the AU and determine exactly what that distance between the center of the Earth and the center of the Sun is. And today, we use radar to determine the distance to Venus from Earth and other nearby planets and asteroids. And by tracking those objects, their orbit, which we know, and other interplanetary spacecrafts in orbits around the Sun, we can calculate the AU very accurately. And this did lead me to wonder, how far can we send radar to measure things in space? And it turns out that this is in the order of billions of kilometers using a space-based radar. So, to get the most accurate measurements of things in our solar system, we can we put radar on satellites and make measurements without degrading the signal in the atmosphere.

Mm-hmm. Yeah, and so… Yeah, let's go through Mars, for example, we get to Mars any time soon. Is that the communication will be, if Mars is the absolute closest to us, to 22.4 light minutes away. And so, that makes communication very, very difficult, and even in terms of computer communication, they've lost so many of these Mars probes and orbiters simply because a lot of times these commands take so long to to propagate, to get there, is that we can't we don't have any real control. Everything has to be autonomous. And so, having any interactivity, it makes is really difficult. And so if we go a little bit further out, we can go to Jupiter, which is anywhere from 33 to 52 light minutes away. And Saturn, which is the next one out, 67 to 86 light minutes. Uranus, now we're talking into light hours, so it's 2.6 to 2.8 light hours away. So when we image Uranus, we're seeing it basically a couple hours ago. And, of course, Neptune is now what we call the outermost planet, and that is 4.2 to 4.4 light hours away. So, that's kind of our planet, and so now that's we can measure that in light hours. And so the kind of the next echelon of scale is when we go to actually get to our stars. So, Mike, do you want to talk a little bit about the distance to our star our closest stars?

Sure, Jay. So, our the three closest stars to Earth, outside of our Sun, are all part of the Alpha Centauri star system. Closest absolute star is Proxima Centauri, a red dwarf. That is approximately 4.24 light years away, so we would be looking at light that had left that Proxima Centauri back in 202. But that is so faint, it can't be seen with the naked eye. The other two stars in the Office Atari system, Alpha Centauri A and Alpha Centauri B are gravitationally bound pair that orbit each other. And they are located approximately 4.37 light years from Earth. And these are the closest sun-like stars to us. Together, they do appear as a single bright star in the night sky that are most visible from the southern hemisphere. After Alpha Centauri, the next closest star is Barnard Starr, a red dwarf that is about 5.96 light-years away in the constellation Ophiuchis, which is situated on the celestial equator. This position makes it visible for most locations on Earth, including the majority of the Northern Hemisphere. However, this is not visible to the naked eye, despite being the fourth closest star to Earth. After the three stars of the Alpha Centauri system, it's a red dwarf that is dim, apparent magnitude of Plus 9.5, meaning you'd need a small telescope or a pair of powerful binoculars to observe it. The closest star visible to the naked eye from 40 degrees latitude in the northern hemisphere is Sirius. The brightest star in our night sky. Sirius is located in the constellation Canis Major, and is approximately 8.6 light-years away. And now we start to move into some of the well-known naked-eyed deep space objects. The 80s, also known as the Seven Sisters, is an open star cluster in the constellation Taurus, now rising very early in the morning in the east. It's one of the nearest star clusters to Earth and appears as a small, faint grouping of stars. And in the mythology of almost every culture has a story about this cluster. Pleiades are about 444 light-years away. The Orion Nebula, also rising early in the morning, is a stellar nursery in the constellation Orion, where new stars are being born. It is visible as a fuzzy patch in the middle of Orion's sword. The Orion Nebula is the closest region of massive star formation to Earth. And is it a distance of about 1,344 light years. So, that would put us back into, it's 700, 600. Sorry, 800 CE, so… Well, well before the medieval era.

Yeah, so we're seeing that now. And in a dark sky, we can go out and see the Orion Nebula with your naked eye, and definitely can see it with binoculars, and so, like you said, so we're seeing 1344 light years into the past. And and I think it's important to mention that these two things that we've talked about here is the Pleiades and the Orion Nebula is there within our Milky Way galaxy. And so, every star that we see is an individual star is actually within our galaxy, and so within. So when we're talking about in our galaxy, we're talking in the thousands of light years, and sometimes ten thousands of light years, but… So, what's the next echelon in scale there, Mike?

Yeah, we go out now to M31, the Andromeda Galaxy, which is the closest major galaxy to our Milky Way. And it has about a 50% chance of colliding with the Milky Way in the next a few hundred million years. It is the farthest object that most people can see with the naked eye, and it was first documented by Persian astronomer in about a thousand years ago. From a dark sky, it looks like a faint, elongated cloud. The light that we see from Andromeda left the galaxy about 2.5 million light years ago, long before early humans even existed on Earth. The hominids who were sort of notable in the fossil record at the time are the Homo habilis, and they were they were starting to make primitive tools in Africa 2.5 million light years ago. From there, the farthest object detected by humans is a galaxy named Jades-gs dash 7 Z13-0, discovered by the James Webb Space Telescope. The light from this galaxy has traveled for an estimated 13.6 billion years to reach us. This means we're seeing the galaxy as it was just 320 million years after the Big Bang, offering a glimpse into the very early universe. The first stars didn't form for a couple hundred thousand years, I believe? Need to double-check myself on that. Due to expansion of space, this galaxy is now estimated to be around 33.6 billion light-years away from us. This distance is a good example of how the light travel distance and the proper distance of an object can be very different due to the expansion of the universe. And we've been talking about light years, but I want to just point out that astronomers tend to use different scales. Parsec is actually the scale that most astronomers are measuring very large distances with. Parsec is a word that is shortened from the parallel parallax of one second. And parallax would be the distance between two measurements made of the same distant object. So we would note the position of an object in the night sky, and then 6 months later, we would note that position again, and here, we are actually using the astronomical unit as part of the measurement of a parsec, because a parsec is the distance at which one AU subtends an angle of 1 arcsecond. So, objects which are nearer to Earth are going to have greater parallax distance. And objects which are further are going to have a smaller one. And from this, from the parsec, we start to build on additional ways to make long-distance measurements. But I will just say that the Andromeda Galaxy is approximately 700,000 parsecs from Earth. And so, we we start to get into something that's called the cosmic distance ladder, or extragalactic distance ladder, and every unit within this starts to build on the previous one, which is why it's a ladder. You use the first direct measurements, such as with radar, where there is no assumptions required to make a measurement, and we eventually get to that astronomical unit. And from there, we can use Parsecs as our next measure. And everything on the extragalactic distance ladder does sort of trend along a scale of Parsects, kiloparsecs, and megaparsecs. But at different scales, you need different methods to measure them. And I think it's just super interesting that we start to talk about standard candles, and taking a class of object with a known brightness, and comparing the luminosity to an object's observed brightness, and using the inverse square law to calculate distances. This was a term the standard candle was coined by Henrietta Swan, and she was important, and she was mentioned in Professor Shane Byrne's talk last weekend, in relation to Cepheid variable measurements, which were important for determining expansion rates of the universe. From standard candles, we move up the ladder, and we start looking at actually, the next the next part of this is what we call a standard siren, which I think is an exceptionally cool term. And standard sirens…

Say that again?

A standard siren. And a standard siren is measured using gravitational waves originating from compact binary systems, such as neutron stars or black holes that are emitting gravitational radiation. And shrinking their orbits, which is observable by the increase in frequency of emitted gravitational waves. And so, the standard siren are also calculated using inverse square law to determine the distance of the source. And from there, we'll, they talk about standard rulers and measuring galaxy diameters. And then in galactic distance indicators, we get into things like dynamical parallax, eclipsing binaries, variables, Lyra variables. There's there's a whole the rabbit hole goes really deep here. So I'm not gonna I'm not gonna go through this whole chart, because it would to really cover how all of this works, I think, would take us an hour, and I know we have we have some other pressing issues today. So, I just want to just want to note that as we get farther and farther out to estimate distances, we're starting to use some very different tools and math in order to gauge. Once we're well outside of the Milky Way, and we want to look at very distant objects, we're using estimates of brightness and of the ringing of gravitational radiation, to estimate how far things are.

Mm-hmm. Yeah, and so that's fairly recent. We haven't actually gravity waves are a recent discovery, and so using them as a measurement is also fairly recent, so it'll be kind of let the listeners know that. And of course, when you were talking about parsecs, all I could think about is doing the Kessel Run from Star Wars, and they were.

Right.

Where all the scientists cringed when they heard that line, because they knew that parsecs was a measurement of distance, not speed, necessarily. And so that was that was so we we did touch on parsecs, and we did mention the Kessel Run when we were talking about that. And so, just to kind of wrap up, I just wanted to, when I approached this subject, I was just wanting to give people an idea of the scale that they can see. And with a small telescope, like, like, for example, that CSAR S50, which is just a 50mm, a little smart telescope. You can see several, many actual galaxies, and you can see way, way into the past. I mean, millions, millions of light years into the past, and so that's just kind of amazing that we can sit here, go out in the night sky and look that far in the past and see actual objects that are that far away.

It really is.

So, yeah, it's awe-inspiring, you know? Well, let's go ahead and wrap this up, and we want to thank all of our listeners for checking out this podcast. And be sure to comment, like, and subscribe, and let us know what you'd like to hear more about, if you'd like us to go more in depth, or less in-depth, you know. If we're getting too geeky, let us know. And you can also check out our individual websites, Wildernessvagabonds.com for Mike's website. And Skylapser.com, which is my website. And if you'd like to help us out, you can buy us a coffee at buymeacoffee.com slash skylapser. The intro of music is fanfare for Space by Kevin McLeod. From their YouTube audio library. From the deep sage 9 Observatory, this is Jay Schaefer and…

Mike Lewinsky.

Wishing you all clear skies.