Well, welcome to the StarCast for the week of September 14th, 2025. I'm your host, Jay Schaefer.

And with me from Denver, Colorado is my co-host, Mike Lewinsky.

How you doing, Mike? Oh, good. A little wet down here this weekend, but I'm doing great, how are you doing, Jay?

It's all good. Let's take a look at some space weather from SpaceWeather.com. Mike, what's up with the sun over the next couple days?

Well, Jay, we have a pretty good chance to see a geomagnetic storm here today. They're calling this a one-two punch. Punch number one being a faint CME, launched a couple days ago from the sun. And punch number 2 would be a stream of solar wind that is flowing from what they're calling the Big Butterfly Corona Hole. Pardon me. If you look at the coronagraph at SpaceWeather.com, you can see it does indeed appear to be a big butterfly, and it is pretty much smack in the middle of the sun, facing us. So, there's a stream of solar wind that is headed towards the Earth, and these two may well combine to give us a G1 class storm, maybe even up to a G2 class storm. So, officially, the forecast says here in mid-latitudes, we have about a 35% chance of an active condition with a 30% chance today and 20% chance tomorrow of a minor geomagnetic storm. Whereas, up at high latitudes, the chance bumps up to a 65% chance of a severe geomagnetic storm in the next 24 hours, or 50% in the next 48 hours. So, there's a good chance tonight that we're gonna see some Northern Lights.

Great, great job.

So, what's in our night sky this week, Jay?

Well, it should be pretty good viewing conditions for a possible aurora, since our last quarter moon occurred here at about 6:33 AM Eastern Daylight Time this morning, so we're looking at a waning moon. And this week is also going to be great for observing the planets. There's a lot of them that are visible. Saturn's approaching its opposition, and the moon and Jupiter will be paired up on Tuesday morning. And then the moon, Venus, and the star Regulus will be close together on Friday before dawn to the east. So, for early morning planetary viewing, it's a great week.

Finally, while it's still very dim at magnitude 14, the comet C24E1 is in the group of stars known as the Corona Borealis or the Northern Crown. So if you've got a bigger telescope, that's a nice comet to take a look at, and it may actually get a little bit brighter as time goes on. So, now let's take a look at some space news. Mike?

Yeah, Jay, speaking of comets, there is a new comet temporarily named SWAN25B, that was discovered on Friday, September 12th, by my Soho spacecraft's SWAN instrument, which is how it got its name. Initially shining at a magnitude of 7.4, it was not visible to the naked eye, but can be spotted with binoculars or a telephoto camera lens. The comet is currently in the constellation Virgo and best viewed by observers in the southern hemisphere, though it is gradually moving into a position that will make it more visible to us here in the Northern Hemisphere. Due to its proximity to the Sun, it can be difficult to spot, but observers have been able to capture images and even see it with binoculars. Now, yesterday, multiple observers in the southern hemisphere did report that it is near magnitude 6, so about 3 times brighter than the day before, and it does appear to be getting brighter. So, this brings up today's topic, where Jay and I are going to discuss comets. What are they? Where do they come from, and how are they named, and how can we best observe them? So, Jay, what is a comet?

Well, a comet is probably the easiest definition is to say that it's a bright object with an apparent tail. And that's kind of what separates it from asteroids, which are also small bodies in space. And so those two things are comets and asteroids, and so the difference between comets and asteroids are where they come from and what they are made up of. And so, a comet is, we think in most cases, is made up of mostly ice, and a little bit of dust and small rocks, and so it's basically a dirty snowball is how we describe it. And so, and comets come from the outer limits of our solar system, and for the most part, they're in the Kuiper Belt and further out from the Oort cloud, and so they are that's the apogee of their orbits, and then they come in to our solar system, and the perigee of their orbits is usually fairly close to the Sun. And the difference between those and asteroids, or asteroids, are bodies of about the same size as comets, but they are generally rocky, and so they're made up of types of rock, and they mostly orbit between the orbit of Mars and Jupiter. And they were once thought to be a planet that had broken apart due to Jupiter's gravity. However, that has been discounted, and it's basically a planet that has never actually formed out of the rocks due to, again, Jupiter's gravity keeping them from actually forming into a solid planet. They, and that's what we call the asteroid belt, and that's between Mars and Jupiter. And so comets come from much further out, and they orbit into our solar system. And also, we kind of name comets for, even though they are not maybe made of the ice or ice and dust, or dirty snowballs, sometimes we'll get interstellar objects, like we have now, we have 3i Atlas that we're not actually sure of the composition of, and we also kind of classified those as comets. And there's also some exceptions within the actual asteroid belt, there are some icy balls, dirty snowballs that we call main belt comets, and so those are NBCs, and those are there's a few of those that are in orbit around in basically what the asteroid belt is. And so that's what comets are made of and where they come from. And how they get their tails is that as they get closer to the sun and they're exposed to the solar wind and solar radiation, whether it's infrared or other radiation, is that they're the ice that the comet is made of starts to ablate or turn to gas. And so that goes directly from a solid to a gas, and that gas that is formed streams out away from the sun from the comet. And a common misconception is that the tail of a comet is following the comet's direction of movement. And that's not the case. It's actually a comet can be moving outward, out of the solar system, and its tail would be facing outward, out of the solar system, or away from the sun. So, the tail might actually be in the direction of travel of the comet instead of trailing behind the comet. So, Mike, tell us a little bit about how comets are discovered, and how they're named, and how we have gotten to know a little bit more about comets.

Sure, Jay. Two things before I dive into that. The dirty snowballs is sometimes also paired with snowy dirt balls, and so comet astronomers will divide comments into classes depending on how much ice there appears to be versus actual solid material. And also, just to note that sublimation is the process of having the ice turn directly into gas, bypassing the liquid phase, I should say. So, as far as how comets are discovered and named, we today use a combination of, although in most cases, it's going to be photography, whether it's photography from a satellite or probe, or from a ground-based telescope. And kind of one of the more famous comets of our lifetime was Shoemaker Levy 9. And this comet was so famous and so dramatic because it impacted Jupiter in 1993. And sorry, 1994. And I remember this event very well. I had an 8-inch Mead Newtonian at the time, and I remember setting it up that evening and sitting in the front yard of a friend's house trying to trying to spot the impact. That telescope was really not up to the task, but it was nonetheless exciting to see the photographs that were on the news at the time. So, Shoemaker Levy 9 was discovered by a trio of astronomers, Carolyn and Eugene Shoemaker and David Levy in 1993. And it was located by a photograph taken from a 18-inch Schmidt telescope at the Palomar Observatory in California. And that was the first active comet observed to be orbiting a planet. So, the photograph method, we would take a photograph and compare it with a photograph taken, say, the day before. And from that process, if something has appeared or moved against the background, we can infer that this is not a star and not a known planet, because we know and can track where the planet should be. So, when a new object appears, we can guess that this is most likely a comet, or maybe an asteroid, and then go on from there. And I want to just kind of mention a little bit about the people who discovered it, in particular, Carolyn Shoemaker. She was and very famous for her time, had discovered 32 comets and more than 500 asteroids, so she held the record for the most comets discovered by an individual at the time. And she did not start her career in astronomy until she was 51, and she kept it up until she was in her 80s. Her and her husband were visiting an impact crater in Australia and were involved in a tragic car accident that killed Eugene Shoemaker. She was injured but survived and continued her work up until in her 80s, until around 2002. And so, the naming of the comets is often credited to the observers, hence the shoemakers and David Levy were the origin of the Shoemaker-Levey9 name. Sometimes, as with the comet this week, Swan 25B, we have named for the instrument that discovers, or that first observes the comet. And that can be useful in a case where you have a large team of people who are all working together to operate and even governments that are basically maintaining the instrument, so that's the sort of the lowdown. I did want to also mention that in ancient times, or even let's say medieval times, the comets were not well understood. It was believed that they were omens, that they would signify great disasters coming. In fact, there was one emperor who, observing a comet, had all of his competitors executed summarily because he felt that the comet was porting his ball from his throne, and so the way to stay on the throne was just to kill anybody who might challenge it. But Tico O'Briay is sort of well-known as an astronomer who in 1577 made very detailed measurements of a comet that's now designated C1577B1. And Tico Obrahe helped to establish knowledge of what the comets were. There was a period of time where it was believed that comets were in the Earth's atmosphere, and he, with his measurements, demonstrated very well that that was not the case. And his measurements also contributed to his protege Johannes Kepler's laws of planetary motion, those measurements were very useful for demonstrating that planets moved in elliptical orbits. Now, we still had a heliocentric view of the universe in 1577, so not some of what was documented then was based on a fundamental misconception about how the universe worked, that the sun was the center of the universe.

Misconception.

But that's how our science proceeds is, little or moderate discoveries and measurements lead to revisions, lead to revisions, lead to, suddenly, the realization that, no, the sun is not the center of the universe. So, that was an important step along the way.

Yeah, we might note that that implies that comets are visible to the naked eye, and so of the comets, on average, we can have a naked-eye comet visible every year, it seems that on average, there's a comet that is bright enough that it can be seen with the naked eye every year. So, and of course, there's the reoccurring comments that everybody looks forward to, like Haley's Comet. And so, and what are some other comments that we see on a regular basis? Do you know of any of that, Mike?

Well, yeah, Haley's comment being very famous. I'm thinking a lot about the one that we had last fall, Sichu-chan, which was in October of last year, and very and it was not a periodic, not one that we're going to see again in our lifetimes. So, you got me there with that question. I have to and I also want to go back and just correct that Tico Brahe was operating off of a geocentric view of the solar system, not a heliocentric one, so that was my mistake.

Mm-hmm. Yeah, and so, for our average viewer and listener, how can we best observe and photograph comets? And so, that question, I'm kind of asking it rhetorically, and right now, there's conceivably three or four comets that are visible with a telescope and camera. And, so, how do we best capture, and what's the best time to catch a comet?

Yeah, we often see them right after sunset or before sunrise, because they're brightest when they are closest to the sun. So, it's not uncommon to be out and with binoculars. I find that starting at a point early in sunset, and probably days before it's going to be naked eye visible, with binoculars, searching in, or sunrise, searching in Western sky at sunset, or eastern sky at sunrise, attempting to get a fix with binoculars on the faint object. So that I get a better idea the next day where to look. And and of course, I'll have cameras out doing time lapse in that same vicinity, and I'll be periodically reviewing the frames in case the object does show up in photographs, but it was harder to spot with binoculars. And I find that getting a fix on, where, roughly, from my position, I'm going to see it on the horizon, from what night to night, it starts to get easier and easier to spot. And because it's gonna appear in roughly the same point along the horizon, maybe a little bit earlier the next night, or a little bit later if it's at sunset, a little bit, be visible a little bit later. So, I do like to track over several nights, and with the most dramatic comments, I'll have two cameras, one wide field, one telephoto. I'll have the C star pointed there. Maybe even my other telescope and pair of binoculars, and be scrutinizing the horizon. You never know what's going to happen and how if the weather's gonna prevent me from seeing it the next night. So, I'll take every opportunity I get to start hunting early, so that when it starts to become a more impressive site, I am well prepared for capturing it from, if possible, before twilight, right up until it sets.

Yeah, and so, of course, with SWAN 25B, which is, and this was totally undiscovered until it appeared basically next to the sun, and they were able to people that were observing the sun, said, oh my gosh, here's a new comet that we haven't seen before. And this one is going to be, probably gonna be visible here really soon for most of our viewers and listeners. And one of the things about it's a challenge with doing astronomy or astrophotography of comets is because their movement is not like star movement. And so, in other words, if you have a telescope that has the inside reel tracking to track the stars so that they don't so they don't blur, is if it were to try to track a comet and then had a stable vision of the stars, the comet would appear to be blurred or it'd be kind of blurry and not well-defined. However, if you concentrate on the comet and track the comet with your telescope, then the stars that are around it, because they're not moving in the same direction relative to the comet, is they appear as streaks. So, often when you see photographs of comets, you will see that the stars are actually kind of a streaky. And one of the things that's really cool about, well, first of all, the planetarium software that is out there is constantly updated, and so that if you go to your favorite planetarium software, and they will often update it with a comment when it appears, so that I noticed it in for the C-Star and their star databases, they just added SWAN 25B to the database, so now you can actually take a smart telescope like the Seastar and say, target SWAN 25B. And it's gonna go to that and actually track the comment instead of actually tracking just with stars around it. So that's pretty cool, huh, Mike?

It is, and Jay, you've reminded me of a couple things I wanted to add into our discussion here. One is that one of the reasons why Carolyn Shoemaker had as many discoveries that she did, is that she was she had very good stereoscopic vision, and this is helpful for detecting nearer objects. One way you can do this is to take two photos taken from different times, and put them together into a viewer that will project them both, so that you can see both of them superimposed, and she was very adept at picking out objects that had some apparent motion in that stereoscopic view. Also, we kind of skipped, or we made some reference to the origins in the original nebula of the solar system. And we would be remiss in not talking a little bit about the Rosetta mission. Rosetta was a probe that was launched to study a comment. It has a Russian name, and I've now lost my link here, but Rosetta sent it was the first probe to actually land on a comment. And really helped us understand more about the origins of comets. So, there was some debate. Were these really, truly just the accretion of gas and dust from the early nebula that our sun formed out of, or did some of what they call, trans-Neptunian objects, or TNOs, did some of these larger objects collide and fragment and create comets? And what Rosetta and the lander fillet determined really helped us to understand, at least with a particular 67P, it was Teremov, Garasomenko, 67P was the comment that the fillet lander took observations of. And we found that that this was a the comment has sort of lobes. You have these smaller objects that have accreted together, and it's fairly loosely accreted. There is not evidence that substantial thermonuclear decay, a radioactive decay has changed or transformed the comment. And all of all of our planets have undergone substantial changes because of gravity, and radioactive decay, their chemical composition has been substantially changed over their lifetimes, whereas the comets being these loose aggregations of material that are very, very cold, very, very far from the sun for most of their existence are apparently, you know, pretty, we can think of them as nebula fossils, almost. They show us what the very early solar system, even before we had much sun, looked like. Or was composed of. So, there's a lot we can learn by studying comets and their compositions.

Yeah, and so, when you say very cold, we're talking near absolute zero, so things happen very slowly at those temperatures.

That's right, that's right. I also wanted to add, Jay, that this SWAN25B, discovered by the SOHO Solar and Heliospheric Observatory, has been a mission that has discovered more than 5,000 comets. And because it is a solar and heliospheric observatory, it is well-positioned to detect comets that are just passing the sun that were too dim until they started to heat up, so more than 5,000 comments discovered by SOHO, which was European Space Agency spacecraft. Launched in 1995. It's been making observations since 1996, and it continues to operate after 29 years in space. Our mission is extended until the end of this year and subject to review, so how much longer we're going to have this instrument is still to be determined.

Yeah, and the SOHO is also has given us great pictures of the sun's corona, and and because it has that the solar mask on it, where it just basically blacks out and makes kind of its own eclipse. And it's images, and that's how we get a lot of the coronal imaging of the sun, just to side note on that particular on SOHO. So, do we so do we expect any visible what naked eye visibles comets this year?

I think SWAN is probably our greatest chance, but we can get surprised. These things do tend to kind of sneak up on us, because until they start heating, we just don't know that they're there. And suddenly, there's a little bit of a tail forming, and enough reflection off of that tale. These tails can grow to millions and millions of miles in length, so they're they can be impressively large. And, and then, of course, we did mention the 3I Atlas, um, interplanetary comet. I don't have any idea whether that composition is gonna turn it into a naked eye visible, I would be ecstatic if we could actually get some viewing for an interstellar comet, that would that would be spectacular, and I'm hoping, very hoping.

Yeah, and the comment I mentioned earlier that's actually in the Corona Borealis right now, Weir shows, or C2024. E1 Weir shows. They're saying that that one is going to brighten up in December, and they're anticipating it to be in the magnitude 6 range in December, so that may be naked eye visible as well.

It'll be very exciting.

Yeah, and it's funny that we can name some of the comments that we've seen over our lifetime, and I remember Hale Bop, I remember Shoemaker Levy. And I remember NeoWise, and what are some of the more memorable comments that you can remember?

Yeah, Hia Kitake was another comment that was in the 90s, it was like we had Hail Bop, and then we had Hiyo Kitaki. I don't recall the exact order that those happen, but a comment here at Kitaki was discovered in January of 1996 and was prominent that year, whereas Hail Bob, that was the one that we had our death cult, right? That was the one that the Heaven's Gate folks were believe that there was a ufo that was going to take them away. Yeah, Hillbop was discovered in 95, so we had sort of back-to-back years of very spectacular comments. I want to also mention I had an experience one night, living up in Nederland, outside of Boulder. And I was outside late. I happened to have my telescope out. It was not actively observing with the telescope at the moment, but suddenly, I saw this thing appear on in the sky that looked like a comet. But I was absolutely dumbfounded, because it was visibly moving through the night sky, and comets being where they are do not appear to move against the background of the stars. In short duration, from night to night. You can, or over the course of a night, you can see a small very small amount of motion, apparent motion. But this this traversed the night sky in about 3 minutes, directly across the night sky, and it looked like by every indication, it was a comet. And I remember that neighborhood dogs started barking at the sight of this. This was not just something that I saw in my friends who were with me observing saw, but the dog saw it, too, and I managed to get my telescope, and it was hard to track with an 8-inch, but I was able to very briefly observe it through the telescope as it was as it was moving, and I had to manually track. And the telescope did not answer for me what this was, but I knew I knew that this couldn't possibly be a comet, and I was just mystified, and so this would have been in the era of Haleb and Hiya Kotake. Probably about 97, 98. And so I went to Usenet, which was a forum or a series of forums that almost it really predated the World Wide Web, but it was an internet resource, and I went to a astronomy. Part of Usenet, and I posted a question. What was this that I saw? And this was still in the early era of the internet, and I got answers, and some of the answers were way out there. But I got several people who concurred that with each other, that what I witnessed was the space shuttle executing a water dump, or flushing their toilets. And so the apparent tale was, in fact, the water that was being ejected from the space shuttle. Looked just like a comet, and I knew enough to know that this couldn't possibly be a comet.
### Cleaned-up Transcript

Jay Shaffer: Yeah, and that goes to… remember earlier this year that we both observed the… it was called the Great Streak, and that was exactly that sort of thing, which was a Chinese satellite.

Mike L.: Yes.

Jay Shaffer: Or Chinese spacecraft. Venting fuel, right?

Mike L.: Right, right. And I will say that there was much less volume coming out of the space shuttle, so it was a much shorter tail. There's still a distinct tail, but it was not nearly as long as our Chinese rocket propellant vent, and I think it just had to do with probably both volume and altitude and speed that created such a very long tail from the… I think it was May that we saw that.

Jay Shaffer: Uh-huh. Yeah, and so, when you're… so if you're out observing, and you think you see a comet, but it's moving fairly quickly, chances are that it is not a comet. A comet you would kind of observe the movement over several days. And so, especially with all the SpaceX launches out of Vandenberg and also on the East Coast, out of Cape Canaveral, is that we're seeing a lot of these rocket launches, or staging, or fuel dumps, that sort of thing, that actually kind of appear to be comets, because they're kind of short-lived phenomena.

Mike L.: That's right, that's right.

Jay Shaffer: And of course, and the big difference between a comet and an asteroid is when a… asteroid hits our atmosphere and becomes a meteor is it can have a tail as well, but again, that is a very short, short duration event. And it may be 3 or 4 seconds would be a long fireball event, and again, it would be an object with a tail, but it would not be a comet.

Mike L.: That's right.

Jay Shaffer: And then, finally, I wanted to… we also both photographed a re-entry of a spacecraft, the trunk from the… which was the SpaceX. Yeah, that Crew Dragon trunk, we… both Mike and I photographed the re-entry of that, and that was almost the… it was fairly long duration, it was over… it was like 3 minutes duration with a fireball, with a huge burning tail.

Mike L.: Yeah, that was really once-in-a-lifetime event, I think.

Jay Shaffer: Yeah, well, let's kind of hope so. We get too many of those re-entries that might be a bad thing for our atmosphere and other things. All right, so that's kind of our take on comets today, and I want to thank all of our listeners for checking out this podcast.

Mike L.: Agreed.

Jay Shaffer: 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 individual websites, Mike's is wildernessVagabonds.com and mine is Skylapser.com. And if you'd like to help us out, you can buy us a coffee at buymeacoffee.com slash Skylapser. The intro music is Fanfare for Space by Kevin McCloud from the YouTube Audio Library. And from the Deep Sage 9 Observatory, this is Jay Schaefer, and…

Mike L.: Mike Lewinsky.

Jay Shaffer: Wishing you all clear skies.