Planetary Radio: Space Exploration, Astronomy and Science - 3I/ATLAS: The third interstellar object ever found

Episode Date: August 6, 2025

Just three interstellar objects have ever been detected in our Solar System, each arriving from the depths of interstellar space. In this episode, we explore the latest: 3I/ATLAS, a newly discovered interstellar comet first spotted on July 1, 2025. Bryce Bolin, research scientist at Eureka Scientific, joins host Sarah Al-Ahmed to share what makes this object special. As one of the few astronomers who has studied all three known interstellar objects—1I/ʻOumuamua, 2I/Borisov, and now 3I/ATLAS—he offers unique insight into how these rare visitors expand our understanding of planetary systems beyond our own. We also check in with Bruce Betts, chief scientist of The Planetary Society, for a look at the upcoming ESA and JAXA’s Comet Interceptor mission, which may one day chase down a future interstellar comet. Discover more at: https://www.planetary.org/planetary-radio/2025-3i-atlasSee omnystudio.com/listener for privacy information.

A rare commentary visitor from beyond our solar system. This week on Planetary Radio. I'm Sarah al-Ahmad of the Planetary Society, with more of the human adventure across our solar system and beyond. We've spotted only three known interstellar objects, commentary bodies passing briefly through our solar system after long journeys between the stars. Bryce Bolin, a research scientist at Eureka Scientific Incorporated, has been part of the scientific teams that have studied all three of these objects.

He joins us to share the story of 3-Ey Atlas, the newest interstellar object, and how studying these fleeting visitors helps us learn about planetary systems beyond our own. Later in the show, Bruce Betts, our chief scientist, drops by for what's up. He'll tell us about Comet Interceptor, a mission from the European Space Agency and the Japanese Aerospace Exploration Agency, designed to wait patiently in space, and then chase down a pristine comet or maybe even one of these interstellar wanderers. If you love planetary radio and want to stay informed about the latest space discoveries,

make sure you hit that subscribe button on your favorite podcasting platform. By subscribing, you'll never miss an episode filled with new and awe-inspiring ways to know the cosmos and our place within it. Before we dive in, I want to take a moment to ask for your help with an upcoming episode of Planetary Radio.

Right now, I'm putting together a show focused on how cuts to grant funding are impacting students, researchers, and faculty in the space science community. While these budget decisions are happening in the United States, their effects are being felt around the world, especially by people that come to the United States to study or conduct research in space science and exploration. If you've been affected by these funding cuts, whether you're facing uncertainty, loss support or you've seen your work disrupted, I'd like to hear your story. You're welcome to share a one-minute audio or video clip describing your experience, which I may share on the show. You can

introduce yourself or stay completely anonymous if you prefer. Just email your clip to planetary radio at planetary.org. Your story matters, and together we can help others understand the real human impact behind these decisions. Now for our main topic of the day, 3i Atlas. For only the third time in history, astronomers have identified a macroscopic object from another star system traveling through our cosmic neighborhood. These rare visitors that are called interstellar objects

aren't born around our sun, but they're flung out of distant planetary systems before finding their way to us. The first one, One-I-O-Mua, arrived in 2017. I will never forget how exciting that was. The second one, to Iborosov, followed in 2019. Now we welcome Three-Eye Atlas. Discovered on July 1st, 2025, by the Asteroid Terrestrial Impact Last Alert System, or Atlas, this new interstellar comet is visibly active, trailing dust as it flies into our solar system.

Its reddish hue and extended coma tell us a complex story, one that hints at how it may differ from its predecessors. 3-Ey Atlas is moving fast and growing more active as it nears the sun, so observers all around the world are trying to get a glimpse of it. To learn more, I spoke with Dr. Bryce Bolin, a research scientist at Eureka Scientific Incorporated, and the lead author on a new study describing the discovery and the physical characteristics of this interstellar comet. Bryce is one of only a few astronomers in the world who have studied all three known interstellar objects. His early work on Omuamua helped characterize its elongated cigar-like shape. He later co-authored papers on Tuai Borazov, including studies on its rotation and chemical composition. Now with Three-Eye Atlas, he and his team are back at the forefront.

Their paper titled Interstellar Comet Three-Eye Atlas, Discovery, and Physical Description, was published on July 18, 2025 in the monthly notices of the Royal Astronomical Society letters. During the conversation, you're going to hear him refer to some of the images that are in that paper. I'm going to link to the images that he references along with the actual paper on this web page for this episode of Planetary Radio. You can find that at planetary.org slash radio. Hey, Bryce. Thanks for joining me. Hey, it's great to be here. Thank you for having me. So you've had this really rare opportunity, which is that you've gotten to observe all three known interstellar objects during your career.

What initially drew you to studying small bodies and then ultimately these interstellar objects? Yeah, it's kind of a strange, I don't know, I guess you could say it's kind of a calling because I originally started out in physics, not wanting to do anything to do with astronomy. I was into high-energy physics, particle physics. At the time when I was finishing up, my undergrad for CERN was starting to pop off with the Large Hadron Collider. And that was like the big excitement thinking, oh, yeah, we're going to see all these crazy new particles with the LHC. And this is relevant for why I got to astronomy.

I went to grad school, didn't go to grad school for high-energy physics because it was like the height of the financial meltdown of 2008. and it was very hard to get into grad school. I barely got in. But where I wound up was not focused at all in hydrogen physics, which was a disappointment for me. So I went to school in Florida. Florida has this weird rule.

Only one school in the state university system can have an astronomy program. But they had a program that was specialized in planetary science. So I was like, okay, I'm not doing the program. particle physics stuff, but why not try, you know, planets? I didn't even know that was a topic you could study, right? So I kind of was like unofficially working with some of the planetary science faculty there. And through that connection, I got to go to France to a planetary science conference. And it was there that I kind of actually got set up with my first astronomy job. I met someone who was associate with people at where I did my master's who was just

happened to be looking for a research assistant for this new project that they were building in Hawaii called Pan Stars. And Pan Stars is this all-sky survey on Mount Haliakala that looks for asteroids. It was also doing an all-sky survey, kind of like early Reuben Observatory kind of stuff, to look at galaxies and the other stars and other other phenomenon. But the person who I linked up with for this job was specialized in asteroids. And it also turns out, this goes real back to the grad school days, this person who was also a former particle physicist. So it was really the connection with particle physics because I didn't want to do asteroids and comets because I thought they were boring. Like, oh, that rocks, right?

So what got me into it was really this particle physics connection with Robert Jettike at the University of Hawaii, where he came up with a way to parameterize the problem. of using observations of asteroids and calculating the observation selection effects that go into the observations, which gives you an estimate of the inherent population before you have all these observational selection effects go into play. They do that in particle physics, and he found a way to apply this to asteroid observations from ground-based telescopes. And it just, wow, it's so fascinating for me. And I was at the University of Hawaii working for three years. I was actually I was also working with Larry Deneu, who is the guy who discovered the three-eye Atlas, the third

interstellar object. I was working almost every day with Larry Deneu and Robert Jettikey and others at the University of Hawaii doing the discovery of near-earth asteroids, potentially dangerous asteroids, if they were to hit the Earth. So how did you end up becoming parts of the teams that did the first observations on the first two interstellar objects? That's an interesting story. That was also kind of an accident kind of thing. After Hawaii, I went to France, where I did my PhD, which was another three years. And then when I finished that, I wound up at the University of Washington, which is where a lot of the Ruben Observatory work that is being done. The director, Jalko Isovich, is a professor there, the lead of the solar system processing team. Mario

Jurich is also a professor there. And Mario was my supervisor while I was there. And at that time, the idea was that we were going to develop all these interesting tools to study asteroids at the Rubin Observatory, and then when Rubin comes on to use those tools to study the asteroids. But while I was there, there was also an opportunity to use this telescope in Apache Point called the ARC, the Astrophysical Research Consortium 3.5 meter telescope. Just on a side note, Apache Point is also where the Sloan Digital Sky Survey is hosted. And so there's a lot of collaboration between a University of Washington Sloan Digital Sky Survey,

so they have access to this three and a half meter there. And it was right after I started in the fall of 2017 at the University of Washington that, you know, this Umuamua, first interstellar object of us was discovered. And at the time, I'd never really, like I'd worked on survey detections of asteroids, and my PhD was on more dynamics of asteroids than the main belt. I'd never really done like a, you know, a case study, focus on one object study with ground-based telescopes kind of project before. But I had just this weird kind of feeling.

It's like, wow, this is really cool. Like when the announcement of Bumuumu, the discovery Bumu came out, like, I couldn't believe it. Because I discussed interstellar objects with Robert Jeddick, University of why. He was one of the first people to study these things. He did the theoretical calculations to estimate how often you would see one based on actual data from PANSTARs using his expertise and synthesizing survey data to come up with an estimate of what the expected population is. But this is one real bona fide thing, and I could hardly believe it, had eccentricity of 1.17 or 1.19, might have to correct me there. But it was like significantly

above one. And for an asteroid to be bound to the sun, it has to have an eccentricity less than one. And we've seen comets that are kind of weakly bound, just a little bit above, one, like hyperbolic, like 1.01, 1.05, but they usually have an encounter with a gas giant. And so we know they come from our solar system, they were just perturbed, which made them a little bit hyperbolic. But seeing something with 1.2, like 20% higher than one, that was just like mind blowing. It was really startling. And it was like, wow, we talked about these things. And there were some estimates that it would take, you know, like five, 10 years with pan stars and like full power mode to see these things. But now we're actually seeing one. We see one. It's on our doorstep.

It's here. And it's just like, wow, I just couldn't believe it. A body that formed another star system coming into our system. It just just, which absolutely incredible. We didn't know at the time it was there. Is it an asteroid or a comet? You know, is it like a kind of like something we'd see from the outer part of our social system versus something that's formed maybe more closer to the terrestrial planets or their equivalent and exoplanet. system. So we didn't know. It was a huge mystery box. I talked about it with Rob. And I thought, are people looking to study this thing? He's like, yeah, well, they're trying to hop on all the telescopes to look at it. And I was like, all right. So I went home. I remember lying down in the

afternoon to like take a nap and I just like couldn't get it out of my mind. Like, wow, you know, this is an interstellar object. This is, this is pretty incredible. So I wrote to the director or the assistant director of the Apache Point, who was a professor at the University of Washington. and say, hey, you know, do you all have any telescopes that we could use to study this thing? It seems like this would be pretty important to try and study this object. It seems pretty interesting. He was like, yeah, well, you can maybe try to work with Apache Point, three and a half meter. I think we can probably get you some time for that, but you're going to have to work with this team from John Hopkins University. And it turns out one of the members of the team was

the professor I worked with at University of Central Florida. This name is John Fernandez. And the guy was this guy named Casey Liss, who was a longtime collaborator of Beyond Fernandez studying comets. And it was Hal Weaver, senior professor at, I think, Duke University in studying comments. So we collaborated and observed, on observing the first intercellar object with this three-half-meter telescope. And the conditions were pretty good. We got pretty good data. And we were the first ones to assemble a complete light curve of this object. and to see it over its full eight-hour rotation, it had like this very large light curve amplitude

of about two magnitudes. We were able to estimate the rotation period and the parameters of the light curve and it implies this very elongated shape, very large axial ratio. Our calculations were six to one because we came up with a way to kind of correct for geometric effects

and shadowing effects on the asteroid. You would basically, if you assume without those effects, to get like an axial ratio of like 10 to 1, but we were more like 6 to 1 after you do this correction. It was so bizarre that not only was it the first one coming from another stars also had like this some peculiar properties. We put out, we constructed this paper quite nicely. And it was a pretty, I think, well received. So it was my first observational paper and it was not bad. We talked about these things before, but we never thought, oh, it could be real. Like it was so

surreal. But really, though, I mean, we know that these objects must exist and that they must come through our solar system at some point, but we're only now beginning to have the technologies to discover these things. And I think we're about to potentially discover a lot more because of tools like the Vera Rubin Observatory. Just objectively, even someone who has no understanding of what's going on in planetary science, I think this is one of those stories that just lights the imagination on fire, right? This, as you said, is one of our only opportunity. to be able to really observe material coming into our solar system from somewhere else entirely. And I think people are right to be really excited about this.

Yeah, it's just mind-blowing, right? You have like all these theories about how many of these things exist out there and what their properties could be like. But like the difference between theory and what we actually observe can be quite large. So like for umuamua, we think it's most likely a comet because it has large non-gravity perturbation is like a comet. Have you heard the queen song? Don't Stop Me Now. There's like a really great line. There's a lot of astronomical references in that in that song, by the way. Talks in it about like I'm on a rocket ship to Mars or something or on a collision course.

Define the laws of gravity. Yeah. So that that line defying the laws of gravity is very scientifically basically based because astronomers in the 19th century were observing Haley's comet, and they noticed that its predicted position from gravity only was very different from its true position in the sky. When they ran the calculations using Newton's laws and Kepler's laws to figure out where the comet would arrive next, it was off. And they were like, oh, it's defying the laws of gravity. They didn't know why exactly right. But that line defined. the laws of gravity that was in the Queen's song, comes from the study of Haley's Comet, comes from the observation.

Using a model where you only have gravity, only the laws of gravity, is not sufficient to explain the full physics of what's going on with the comet, which results in it having a position very different from where you would predict using only the laws of gravity. So defying the laws of gravity is what Umuamua did as well. And comets defy the laws of gravity. And they emit gases, which has a non-negligible momentum on their impulse on their trajectory. And so, umuamua did this. And so there's some interesting discussion about that.

But that kind of, let's say, ease some tension there because we weren't sure if umu-a-m-m-mua was an asteroid or a comet. And because we think that comets outnumbered the asteroids by quite a lot in our star. system and star systems extra solar we think they should as well you think that you know what's going to be ejecting the space and seen by some other people and star system somewhere else in the galaxy is going to be a comet but we didn't know and so when it uh when umu-o-m-wooa was defying the laws of gravity we kind of gave us a sigh of relief the other two inter-solar objects two-eye borosov three-eye atlas are clearly comets they have very have an active appearance uh a tail and

some peculiar quality you can see with that they're both very different from each other in that respect but they are comets so it seems that so far all the interstellar objects with their comet-like material which kind of checks with our expectations of planet formation what we think the material around other stars should be like but you know we're in exciting times we could see something asteroid at some point and because these are comets they are basically hiding the nuclei of 2i and 3 are hiding inside this envelope of dust. What kinds of things have you been studying during the limited amount of time that we've known about this object? Yeah, so for 3i Atlas, we our first kind of look at it was using broadband colors, getting kind of optical wavelength colors.

Also observed it with KACC telescope, we got near infrared colors and near infrared spectra. we want to understand the surface properties, well, not really a surface product, because we've seen the coma, but like kind of the bulk, like scattering cross-section properties as a function of wavelength. And that tells us a number of things. We can see possibly the emission of cometary gases. In the visible in the near UV, you emit gases like cyanogen and carbon, diatomic carbon, triatomic carbon. And this can be indicative of the, the volatilization of the comet. You are producing these molecules that are first originating as ices in the comet and then their heat from the sun is causing the ices to sublimate. And then they are undergoing

these complex reactions while they're in the coma of the comet and breaking down one of those products can be synogen as well as the triatomic carbon. We're going to be getting some James Webb observations of these objects. I'm not formally a part of that team, but James Webb is going to be able to observe the comet in wavelengths well beyond the visible near infrared. They go into the wavelengths into the 3 to 5 micron range, where we can start to see the emission of cometary gases directly from the baltic species that we see are most common among comets in our solar systems, such as water, carbon dioxide, and carbon monoxide.

And so we can do the direct detection of these gases using the James Webb. With Borosov, the second interstellar object, we saw we did detect carbon monoxide using, ground-based alma observations, as well as with the Hubble Space Telescope using the near UV instrumentation on the Hubble Space Telescope. But now we have James Webb. With Borosov and Uw-Wu, we did not have James Webb, but now we have the James Webb, and it has this great capability to study the Volusosos of Comet. So that's going to be potentially pretty huge. And they should be happening in a few days. We'll see, we'll see if they get the comet.

as with anything that's like moving within our solar system it's always tricky at a distance to try to like actually capture that thing but i mean those observations are going to be really wild i mean i don't know what the images themselves are going to look like but the spectra of this object from a completely different system it could could be pivotal especially given that we don't know where this thing came from but some of the other things i've seen online suggest that this object could be much older than even things in our own solar system. What do we know about kind of where this object came from and potentially its origins based on that? Well, this is a very interesting topic and something that I've thought a bit about. What people are doing with intercellar objects, one eye, two eye, three eyes, they're basically estimating their kinematic ages in the galaxy, basically how, let's say, heated up or exceeding cited the orbits of these objects are and the time scale in which it takes for them to get to this

level of excitation. And they're saying that that can occur. It would take billions of years for that to occur. If they were more recent ejection from the star systems, they would have orbits that aren't as heated up with respect to the galaxy. But my understanding is that this is actually pretty difficult to do. I mean, I'm not a galactic dynamics expert. With the discovery of I became an open question. Okay, we're studying hyperbolic orbit with respect to the sun, but what is this thing doing out there in the galaxy? And it turns out that the galaxy is, well, I think everyone knows this,

is quite complicated. It's a lot more difficult problem than asteroids orbiting our sun in the sense that it's not like you have all the stars in the galaxy orbiting Sagittarius A-star or the supermassive black hole. I mean, they do in a way. but there's the gravitational potential is quite variable in the galaxy because it's huge. And it can vary quite a bit because you have irregularities. You have molecular clouds.

You have spiral arms. We have stellar clusters. And so the way that this affects the orbits of stars and interstellar objects that they float around the galaxy is quite difficult to understand. So when you're talking about things that are old, I think I saw things, saw some papers, some results saying, oh, these are billions of years old objects. But one orbit of the galaxy is like, what, 500,000 years for the sun. And so just in that time period, you can encounter spiral arms and all sorts of things

that can really throw off your trajectory of the galaxy. And so I think it's really hard to say anything more than that past maybe one or two galactic orbits. So I think like people who are trying to backwards integrate these orbits to see, okay, when they were close to some star, and they must have come from some star. And it's a good idea. It's, you know, it's a like first order of curiosity thing to try and do. But it turns out the dynamics in the galaxy kind of prevent you from doing this accurately. Yeah, everything's moving out there and everything's moving inside our solar system. I do want to say to people, though, who might be worried about this, that this new object, three-eye Atlas, is not going to come close enough to Earth that we have to worry about it hitting us, even though it was discovered by Atlas, which predominantly looks for these kinds of things that might be a danger to us.

Do we have a general idea of the way that this thing might be passing through our solar system? Yeah. So I have a picture of the orbit of this object. So this is our paper that was published in the monthly notices of the Royal Astronomical Society, where we just, describe the orbit of this object. Now, so this is not the best orbital diagram in the world. I'm sure there is much more fancy ones out there that are animated and so on. But this is showing the orbits of planets in our solar system. The orbit of Atlas is this is a black line right here. And Jupiter is this kind of khaki green line and Mars is red and the Earth is green and Venus is blue and Mercury is pink. So this was at the time the object was discovered on July 1st of this year.

So the Earth is going to be rotating counterclockwise like this, whereas 3-I Atlas is going to be going along this trajectory in this kind of bottom-to-top direction right here. So what's going to happen is 3-A Atlas is going this direction, but the Earth is going to be rotating around this direction right here. So as you can see, it's actually three-alice is actually going to get quite close to the orbit of Mars. So it could actually pass pretty close to Mars, which could be an interesting opportunity

for spacecraft and Mars to try and observe this thing. I'm a fan of it. I think they should give it a try. 3-A Atlas will be observable up until the end of August, early September-ish, and then it goes into solar conjunction because as it's getting closer to the sun, the Earth is going to be rotating around the sun, and the sun's at the center of this plot right here. The sun is going to be blocking the view of 3A Atlas from the Earth. So when it passes through perihelion, it will kind of be, it's what we call solar conjunction.

But when the Earth gets around the other side of the sun, 3A Atlas will be going here. So we'll be able to see it again after it goes through perihelian. And for people who are listening to this, since you can't see the plot, I will be sharing the paper and an image of this plot on the web page for this episode at planetary.org slash radio so you can see. But it is very clear by looking at this diagram that this thing is on a wild trajectory that it's just going to careen right out of the solar system. But also, I think what you've pointed out about the fact that we are limited in our ability in time to see this object from Earth is really interesting. And I love the idea of some spacecraft around Mars or maybe even, I don't know, or the Juice mission or other ones that are out there right now, maybe even Psyche, to maybe if

they can turn their cameras on this thing and see if they can get a look at it during the times that we can't observe. That would be really interesting. And since there's so much stuff coming out of this, it's got to be hard to figure out exactly what size the nucleus is on this thing. Do we have any size estimates? So there's two ways of doing that. So at the present brightness of the comet, it's about 18th magnitude, 17th magnitude.

and located about three or four astronomical units from the sun, kind of can give us an estimate of the nucleus, where we can compare that to other interstellar objects when they were observed at the same time. They're not really the same because they have different amounts of dust and the proximity of the sun, but at the similar distance from the sun,

two-eye Borsov had a brightness that was a couple of magnitudes fainter. And we didn't detect them in nucleus of Borisovus. It was too small, but we think it's somewhere in the order of 500 meters, a few hundred meters. So when you have two orders of magnitude difference, that implies a size of about a kilometer for three-eye Atlas. The other way of doing this is with high-resolution imaging. So David Jewett at the University of California, Los Angeles, observed this object with the Hubble Space. telescope. The great thing about Hubble is that you have near diffraction limited observations from space that aren't affected by the smearing of the Earth's atmosphere. So from the ground,

typical seeing is about one arc second. But in space from Hubble, the resolution is about 0.04 arc seconds. So we're talking much, much finer resolution there. The reason why that's important for comets is because comets are resolved objects. So a point source viewed from the ground with an arc second to resolution is going to be one arc second. When viewed from space, it's going to be the size is going to be 0.04 arc seconds. But for comets, because of their extended sources, the angular size from the ground for this case of 3i Atlas is about two arc seconds wide. And in space, it's also two arc seconds wide. Key difference. is in the nucleus region because the nucleus is unresolved. The tail and the coma of the comet are

resolved, but the nucleus is unresolved. So when you look at the comet from the ground, you're seeing a mishmash of the nucleus and the unresolved nucleus with the resolved tail. So they're combined on top of each other. And the scale of the mishmash for the comet nucleus is about an arc second wide. But in space, the tail is two arc seconds wide. It's just because it's a resolved objects, but the mishmash with the nucleus is much, much smaller. And the cross-sectional area difference between 0.04 and 0.04 arc seconds from space versus one arc second from the ground is a factor of 600. So what that lets you do is let you observe much closer in the nucleus to the comet by a factor of about 600.

And the reason why that's important is because you can basically measure the light from the nucleus with much less contamination from the dust. And it's a factor of 600 difference level in contamination. When you're looking at a comet, it's kind of like, it's kind of like looking at a fuzzy cat. Have you ever seen a big fluffy cat after it goes to the groomer and it gets like a buzz cut? So it's kind of a similar thing with comets. When I was a kid, we had a Persian cat, and my mom had allergies, so he would have to get a haircut. This big fluffy cat, and you get the lion cut, and it's got a buzz cut, it's a lot smaller.

It's way smaller in procession. And so using the Hubble Space Telescope to estimate the size of the cat or the comet versus the ground base, it's like a difference between just getting like a light, it's a haircut, like removing just a little bit of the fur from the gravity, like the ground observation. You just give the cat a little bit of a trim here. But when you use the Hubble Space Telescope, you're getting the bus cut. You're removing a lot of the hair. So you can get a much better estimate of the size of the cat. You need that higher resolution to shave most of the fur off and get a much accurate estimate of the size. I'm just never going to think of a Hubble Space

telescope the same way ever again now. Thank you. Yeah, yeah. It's really, it's like the cat rumor of space for cat comets. It's the ultimate face-space grooming tool. We'll be right back with the rest of my interview with Bryce Bolin after the short break. This October, NASA needs you. Hi, I'm Jack Corelli, Director of Government Relations at the Planetary Society. In response to unprecedented proposed budget cuts to NASA's science programs, the Planetary Society and a coalition of our

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Washington. Well, there's a lot of complexity to the way that comet tales behave. What's going on with the tail or tails on this object? The 3-I Atlas is quite interesting in the sense that the tail is kind of going in a strange direction. So here is the Hubble data of 2i Borisov, and it kind of has this extended tail that goes in the anti-solar direction. So in this plot, I show the direction of the sun as well as the direction of the comet in its orbit.

But the really important one is the direction of the sun. So the sun is going this southeast direction, and the comet tails in the opposite direction of that. It goes out in the space into kind of the northwest. So that's kind of the key idea is that comet dust when it gets ejected in space is blown in the direction opposite from the sun due to solar radiation pressure. But curiously, this is not what we see for 3i Atlas. So I'll show you my data here. There's much better data taken from the Hubble Space Telescope, but this is with a palomar 200-inch over here. The key thing here is the sun, the sun direction,

is going off into the northwest direction. Curiously, the tail of this comet, it's blobby and it's kind of preferentially going into the direction of the sun. It's going in the solar direction. So I discussed this in my paper. The interpretation is that you have large dust particles that are being ejected in the space,

and they could be larger, large-ish. They could be, say, hundreds of microns across. They're too heavy due to their size, or too heavy to be blown in the opposite direction from solar radiation pressure. So I think what's happening is that the sun-facing side of the comet is heating up, and that is where the ball throws are coming off.

And the solar wind is blowing in the opposite direction. But the dust particles, they're leaving the comet nucleus they're going into space towards the direction of the sun, but the acceleration pressure isn't strong enough to blow them around and go into the opposite direction again. So it's kind of giving the comet a little bit of a distended directionality towards the sun's direction. And the Hubble data show this really well because the Hubble data are really, really nicely resolved. And based on this information, in my paper, we think that thus is leaving the comet at very slow speed, about a meter per second, very, very, very low velocity.

It seems to suggest that maybe the comet is kind of weakly active right now. It's a little bit further from the sun. It's starting to become active. It's starting to become more active. It's kind of a, it's not something like, whoa, like, you know, unexplainable. But it's just not the typical thing that we see for a comet. And all the more reason why we need to get as many observations of this thing while we can, before it goes behind the sun from our perspective,

do you have any recommendations for people who might want to pull out their telescopes or maybe if they're asteroid hunters, what can they do to try and help in the effort to understand this object? Yeah, so I would recommend that they try to observe the comets in the morning hours before it goes into the solar conjunction, it would be available in the evening around end of August, as well as when it comes out of solar conjunction, early December or mid-November,

it's predicted to be quite bright around 12 magnitude. So that's within the range of smaller telescopes. It might be difficult to see with the human eye, like if you're looking through an eye piece, but if you have like a CCD camera or CMO's camera, I think it should be quite doable. I'm looking for ways to collaborate with the community. We're kind of putting together an observing campaign for this.

Some people contacted me. who have interest in working and studying this object. So if any listeners or people out there want to get involved, don't be shy. You can reach out to me and let me know. We can see what we can do. Yeah, we only have limited time on this one, but they seemingly happen to come through our solar system on enough of a regular cadence that we're getting these opportunities every few years.

And now with the Rubin Observatory and its ability to find objects, I was speaking with with Stephanie Deppa from their communications team just a few weeks ago. And we were having this conversation literally days before this object was found. So I think people are going to have way more opportunities. But I mean, what does that feel like to you as someone who's kind of stumbled or random walked your way into a career full of these objects? Yeah. So I think we're living in some really exciting times here. And it's interesting that 3i Ellis was discovered.

by a half-meter telescope in Chile, not more than 10 miles away from where Rubin Observatory is. So I think it's a pretty interesting sign here that things are accelerating towards more discovery of these types of objects. We had a little bit of a weight there, because between the first interstellar object and second interstellar object,

we only had a two-year period. And we had to wait six, seven years for this other one right here, almost. And I think with Rubin Observatory, we can expect to find more, increase the search volume for these things. And it's going to be a wild time because we have to figure out, you know, how we're going to study these things in the Rubin era, because Rubin is going to be detecting them much fainter. So 3-I Atlas is very bright.

It's a 70 to 80th magnitude is found by a half-meter telescope, by the Atlas Telescope. But Rubin is a 6-meter equivalent telescope and detecting things much fainter than that, that I can think is 23, 24th magnitude. That is going to be well outside the range of most telescopes. So far, with this telescope, I've characterized it with, I use Keck Telescope, which is 10-meter telescope. But a lot of the characterization so far has come from smaller telescopes. Even for 8-meter telescope, 23-24th magnitude object is going to be difficult to characterize. They will require photometry. Spectroscopy will be basically almost impossible. I think the

majority will have to be getting photometry from the ground and then relying on space-based telescopes like James Webb to get the spectra, which is going to make James Webb more in demand for studying these types of objects. There'll be very interesting times. I think we'll see more discoveries, and I hope that the astronomical community will respond by accommodating more requests for the characterization of these objects. And I mean, looking very far to the future with the ELTs, like the extremely large telescope. Ruben is projected to have a 10-year operational lifetime. But if there's some overlap between the extremely large telescopes and Rubin,

those will be great for the characterization of these objects. Between ELT and the Magellan telescope, we spoke about a few weeks ago, there's so many cool opportunities that are coming up. And I love that you've gotten to be at the crux of this new form of discovery. These objects are so cool and can teach us so much. And potentially someday, we'll be able to rendezvous with these and learn even more. But that's even further in the future. That's the dream.

There's a mission called the Comet Interceptor, which has that as a goal. I don't know exactly when they're going to go in space, when they're going to launch, but I think it's within three to four years. But I'm thinking it's going to accelerate because of the discovery of 3i. I think it's going to accelerate that process. And I think there will be overlap between comet interceptor and Rubin Observatory. So I think you can expect, no guarantees, of course, but I think it's very realistic that we will have a common interceptor rendezvous with the intercellar object within the lifetime of Rubin. I think that's very viable.

Well, sometime, when I bring you back on to talk about the next interstellar object you're studying, we'll see whether or not that's true. We'll play this clip and see what happens. It could be very soon. It could be, you know, two months from now. You never know. It could be a year from now. It could be five years from now. But I think we can expect, for I, the fourth intercellar object, to be in the not too distant future.

I would say within a year or so. Well, I want to thank you for taking the time to do this. I know that you're currently at a Ruben workshop doing a bunch of work. But also, I understand that after this object was detected, you spent something like 35 hours straight working on this. Oh, yeah. And that is some dedication. Like, I've had some long observing nights, but that is a long time. Yeah, yeah.

Oh, my gosh. Yeah, that was wild. And nerd alert here, I was, yeah, I was playing Magic of Gathering when I saw in the email that this was starting to come out. And so I was already organizing, making phone calls to try in an observing effort to get time, to get the telescope time on this thing. So we got time on it very quickly, July 2nd. When we got time on it, it was discovered July 1st. We got it on July 2nd with the Kodomia telescope near Cairo.

And July 3rd, we observed with a palomar 200 inch. And July 6, we observed it with the Apache Point, the 3.5 meter. A day later, we submitted our paper. And so, yeah, we... We were working around the clock on this. And not only my paper is about photometry, but there's a student I worked with at Caltech by the name of Matthew Beliacob. He was doing the spectroscopy.

So we got photometry from imaging as well as spectroscopy. And so I was working on the photometry. He was working on the spectroscopy and he has a paper, well, it's a research noted that the American Astronomical Society is working on a peer review publication in WAS journals to be submitted. minute soon. But we were, yeah, that was a very intense, you know, a few days there. We were, I was at one point sleeping for just a few hours on like some chair in the office there. But yeah, it was, it was a race. In these cases, it is with interstellar objects. The Umuamua was a was a mad dash as well. We, when the discovery was made, it was around

Halloween of 2017, and we jumped on it and tried to, you know, got observations of it in early November and submitted our paper like a week later, like the second week of November and posted it on the archive. And yeah, it's just every astronomer in the world who studies Astros and Comps is going to want to look at this thing. There's going to be big telescopes, Grand Telescope Canaria says one, this 10 meter telescope in the Canary Islands. You have the Keck Telescope. You have Gemini North, Gemini South, these eight meter telescopes. So you have the VLT. And, you know, there's a lot of really good observers out there who, want to jump, pounce on these things immediately. And so if you want to survive in this kind of

environment, you have to be very quick. Seriously, you know, may the coffee and the magic the gathering be with you as you do all of this work. I think a lot of people sometimes think that astronomy is really chill, very long scales between discoveries, you know, especially in planetary science. It can be a long time before you can go back to another world and get a whole new set of data. But there are realms of planetary science and astronomy that are really, you make a discovery and everyone's on it in a hot second

and you are right at the crux of that. So I appreciate you putting in all the work because I know how tiring that can be. But here we are learning all these amazing things about the third interstellar object we've ever discovered ever. It's crazy that we can even say that. Yeah, well, it's just really exciting.

And, you know, it's like, yeah, it's tiring, right? But, you know, it's the excitement and the adrenaline rush, you know, it just keeps you going. And a lot of excitement to be out there and try to be the first one to publish something on this. It's like, I don't know. I just couldn't stop until just kind of like for the first intercellar object I was telling you about how I wanted to take a nap, but I couldn't. And, you know, until I did something about it.

It's kind of similar. For me, I just want to like figure it out. And it's more exciting if you're the first person. For a just brief moment there, you and the people on your team and the people observing this object around the world were the only people to know something deeper about an object that may have been traveling. through our galaxy for ages. It's a fascinating thing to think about in a special place to be and that you have a really cool career and I really appreciate you taking the time to come on and share more about this. And seriously, when four-eye happens, I'm calling you. Oh, sure thing. Well, thanks so much, Bryce.

Yeah, well, thank you. Now it's time for What's Up with Dr. Bruce Betts, our chief scientist at the Planetary Society. Hey, Bruce. Hey there, Sarah. Right into the nerdy element. Hey, I'm ready to go. Let's do a show. Okay, I'm done. Nerd adjacent.

So I was talking with our guest this week, Bryce, and he told me that the moment that he learned that this new interstellar common existed, he was literally in the middle of a game of Magic, the Gathering. I love that so much. What action did he take? Who knows? I mean, I'm sure, like, as soon as he found out, he just flipped the table. Yeah, it flip the table.

People love it when you do that. But it was the perfect opportunity. I've been playing that game since high school. And it was funny to me because on the day that we were having that conversation, it was literally the release of the first fully space set of Magic, the Gathering, Edge of Eternities, excluding Unfinity and all of the commander decks that are space-themed. So we got to have a fun nerdy conversation about that. And I wanted to ask, have you ever played Magic the Gathering before?

I did. But it was many, many years ago with my sons when they were not adults. And we did play and it was fun. But I haven't stuck with it like you have, obviously. Wow, that's a really great way to teach math skills to the younglings. I mean, there's a lot of math there, man. The number of counters and tokens and, like, Like, compounding factors.

Ooh, magic the gathering with compounding interest. But if you are a fan of space games and you haven't played that card game before, I just want to shout out the beautiful space art on those cards. It's absolutely phenomenal. But another thing that came up in my conversation with Bryce was the European Space Agency's Comet Interceptor Mission, and we didn't get to talk a whole lot about it in our conversation. Clearly, it's not launched yet. it's launching in 2029.

But since I have you here, can you tell us a little bit about their mission? Sure, it's a really cool concept because they're basically going to try in 2029 to launch a mission that will go out and just hang out until a comet's coming in that hasn't been to the inter-solar system before. So it's coming from way out in the or-or-d-or-d-cloud.

And they have a spacecraft ready to go. And then when they find one that they can reach with the fuel they've got, they go after it. So they put it at Earth Sun L2, so a million and a half kilometers away from Earth from the sun. And it hangs out there in some type of halo orbit probably. And then it goes off to try to encounter either a long period comet or one of our interstellar visitors, which would be even trickier since there are fewer of them. but that would be, either would be super cool and super different since even the long period comets have never presumably been altered by coming by the sun yet, so it gives a new opportunity.

So it's a neat mission, and they actually even have three spacecraft, although they all travel is one until they get closer to the object. They've got a couple others besides the main one to do observations from other angles, and they will be like visiting something new, whether it's from outside. the solar system or just way out into the solar system. And it should say it's ESIN collaboration with Chaxa, the Japanese Space Agency, and is providing portions of it as well. So they basically have a good flyby type spacecraft, and they have the wherewithal to put it

out there without an active target when they launch. And that actually will be very beneficial for trying to get to one of these things that there's no way we could just, well, there's no way, but there's no way. but there's no current technology easily done way to go hunt them once they come flying through and you've found them. Also, we find things farther out now as the telescopes and the search gets better. So there's more time to go after these things, either type of object than there ever was before. Okay, let's, shall we move into a real space act?

Let's do it. Lunar football. One, a very amusing concept for a game that would be impossible to organize. Two, a nickname for the Apollo Lunar Rock 61016, which also has the nickname Big Muley, which oddly enough is the more official nickname. And Big Muley is the largest single rock and most massive single rock returned by the Apollo astronauts. And it is roughly the size of an NFL football. Wow.

Lunar football, it is 11.7 kilograms, which on Earth is 26 pounds and one sixth of that on the moon. It's a thing. I'll also mention the next two in size. We've got Great Scott and Big Bertha. Great Scott. Great Scott. Which presumably I assume was named after Dave Scott, the Apollo 15 astronaut. Big Bertha is just a thing. Oh, I should say Muley, it was named after someone with a long. or name, abbreviated to that, who is leading some of the geology activities on Apollo 16 and 17. Muley is hanging out with most of the lunar rocks in the curatorial facility at NASA Johnson Space Center, being kept all happy and pristine, I mean, as much as you can, so that researchers can keep applying new technologies to studying these things. I've seen some smaller moon rocks, but just being that close to, a piece of the moon. I mean, I know we get little pieces of the moon every now again coming in as like lunar meteorites and things like that, but it hits different when you're right

next to one of those Apollo rocks. Yeah, it's pretty trippy. A little known fact. I did infrared spectroscopy of some lunar regalith in the way back in the past. So I was hanging out with lunar dust. That's what made me so crazy. All right. Everybody go out there, look at the nice to the sky and think about gel cats, whatever that is. Thank you and good night. We've reached the end of this week's episode of Planetary Radio, but we'll be back next week with even more space science and exploration. If you love the show, you can get planetary radio t-shirts at planetary.org slash shop, along with lots of other cool spacey merchandise. Help others discover the passion, beauty, and joy of space science and exploration by leaving a review or a rating on platforms like Apple Podcasts and Spotify.

Your feedback not only brightens our day, but helps other curious minds find their place in space through Planetary Radio. You can also send us your space thoughts, questions, and poetry at our email. Planetary Radio at planetary.org. Or if you're a planetary society member, leave a comment in the planetary radio space in our member community app. Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by our members. You can join us, as we work together to support the space science community around the world at planetary.org slash join. Mark Hilverta and Ray Paletta are our associate producers. Casey Dreyer is the host of our monthly space policy edition, and Matt Kaplan hosts our monthly book club edition.

Andrew Lucas is our audio editor. Josh Doyle composed our theme, which is our first. is arranged and performed by Peter Schlosser. My name is Sarah Al-Ahmed, the host and producer of Planetary Radio. And until next week, Ad Astra.