Science Friday - Meet 3I/Atlas, An Object From Another Solar System

Episode Date: September 4, 2025

Earlier this summer, astronomers discovered something strange whizzing past Jupiter: an interstellar object. Scientists named it 3I/ATLAS. It’s only the third interstellar object ever observed, and it’s due to leave the solar system by the end of the year, so the race is on to learn as much as we can about it. Host Flora Lichtman talks with astrochemist Stefanie Milam about what this object could teach us about other solar systems—and ours.And, for the past two years, researchers have been studying samples from the near-Earth asteroid Bennu, trying to tease out details about its origins, and what they tell us about our solar system. Researcher Jessica Barnes describes a new analysis of Bennu samples that found stardust, the residue of ancient exploding stars, older than our solar system.Guests: Dr. Stefanie Milam is an astrochemist at NASA and a project scientist for the James Webb Space Telescope. Dr. Jessica Barnes is an associate professor in the Lunar and Planetary Laboratory at the University of Arizona.Transcripts for each episode are available within 1-3 days at sciencefriday.com.Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hi, I'm Flor Lichtenen, and you are listening to Science Friday. Today in the show, a space bonanza, starting with a strange visitor from another solar system. We put all hands on deck basically to make sure that we were ready to observe this object, pointing every telescope that could possibly detect it as frequently as we possibly can. Attention, Earthlings. Our solar system has a visitor. Earlier this summer, astronomers discovered something odd whizzing past Jupiter, an interstellar object, an object from another solar system. Scientists named it three-eye Atlas. It's only the third interstellar object that we've ever observed, and it's not going to be with us for long. It's due to leave our solar system by the end of the year.

So the race is on to learn as much as we can about it before it leaves us behind. Here to help us get to know Atlas is Dr. Stephanie Milam. She's an astrochemist at NASA and a project scientist for the James Webb Space Telescope. Stephanie, welcome to Science Friday. Thanks so much for having me. Tell us about when you first met this object. When was it spotted? I first met this object in the middle of the summer and I received a whole slew of emails the 4th of July weekend, which nobody was checking.

their email, of course. Of course. From my team. And saying that this new interstellar object had been discovered and we needed to activate our program on the James Webb Space Telescope to do a comprehensive study of what it's made of and hopefully disentangle some of the origins of these objects. Okay. So you got word that there was this interstellar object and basically you were like, it's go time. Right. So the principal investigator of the program, Martin, is a very close colleague in mine I've been working with for goodness 15 years now. And he was completely offline. He was hiking in the middle of the woods.

I believe in Maine. So I'm trying to call him. I'm Facebook messaging him. I'm calling his wife. You know it's desperate when you're Facebook messaging. And nobody could get a hold of them. So we contacted the observatory and we said that we are planning to trigger and we kind of, well, basically went behind his back and pulled the trigger on this. And so he comes back and we put all hands on deck basically to make sure that we were ready to observe this object, pointing every telescope that could possibly detect it and look at it as,

frequently as we possibly can. And so we were coming down to the wire that we were going to have to observe this object with the James Webb Space Telescope now, or it's basically getting in a part of the orbit where we won't be able to access it with any telescopes. Okay, so you're marshalling all these telescopes to look at it. Why is this such a big deal? I mean, I can hear in your voice it's a big deal. Why is it such a big deal? So this is only the third intercellar. object that we are, that we know of that has come into our solar system. The first interstellar object was called a muamua. It was one I. So I means interstellar. The number before the I is the number of objects. So one I, amua muamua was the first intercellar object. We know a muamua on this

show. We've been following the umuamua drama on this on this program. Yeah. Two I, Boria is off was the second one. And it was more comet-looking than a Muamua was. But that was in sort of 2019. The James Webb Space Telescope had not launched. And so we used all the telescopes we possibly could on the ground, but the capability, the sensitivity and the wavelength coverage that we have with the James Webb Space Telescope, we knew it was just going to open up a whole new plethora of information about these kinds of objects. And basically, it's designed to do these kinds of studies. I argue with the galaxy people all the time. I try to convince them that comets and interstellar objects is where JWST needs to focus. Okay, so what is Atlas? So Atlas is what we

believe to be an interstellar comet. And we call it a comet because it's active, which means it's emitting gas and ice and dust so that when you see pictures of it, so the Hubble Space Telescope has imaged it, it's fuzzy. It looks like a comet. It has a tail. And that means it's sublimating or the ice is actually basically vaporizing on this object as it comes closer to our star, the sun. Tell us a little more. What's this comet made of? So we confirmed that there was definitely water, but not a whole lot compared to the amount of carbon monoxide and compared to the amount of carbon dioxide. There was so much of it. This was a huge finding for us.

We've never seen so much carbon dioxide compared to water. So there's a lot of carbon dioxide. As this object comes closer to the sun, it's going to start sublimating more and more. And so whenever we get to observe this object again later on this year, it might change that abundance ratio in ways that we don't know yet. So we're anxious and excited to see how that changes. Is what it's made of, does that relate to its journey or where it comes from? Yeah, well, that's what we're trying to find out. What we believe of small bodies, both in our solar system, as well as in other,

planetary systems. And small bodies include everything from asteroids and meteors to comets to trans-Neptunian objects. We think these are sort of the cookie crumbs left of when planets form in a given planetary system. And so it tells us about the conditions that our solar system formed from, the chemistry, and how much of that is actually preserved versus totally cooked. Are we seeing, you know, burnt cookie crumbs? Are we seeing fresh chocolate chips? What do we got? So getting access to these interstellar objects tells us something about how another planetary system formed. And that's what's really cool, because we want to see if they look like the same cookie crumbs as our solar systems. That's fascinating.

Yeah. And if so, that means that that planetary system potentially had the same candy crumbs. chemistry that formed its planets that we had here forming our planets, meaning the organic chemistry or prebiotic chemistry might be ubiquitous in other stellar systems. And does it look like the objects in our solar system or is it too soon to tell? That's the hard part. So the only way we see these kinds of carbon dioxide to water ratios and other planetary systems is when these objects would form. way, way, far away from their star in an area where there's hardly any exposure to radiation. So it's mostly just dust grains that are just collecting any gas in its vicinity and creating

these icy grains, comets. Yeah, it's like a peephole into, you know, another place in time, it seems like. Exactly. Do we know how long this comet has been traveling for? Well, we don't really know how long that we expect. the object to be anywhere from 3 to 11 billion years old, which is a considerable age. And they expect that it's actually from the thick disk of our Milky Way. So sort of closer in towards the center of our galaxy. And when does it leave? How much more time do you have with it? So we don't have a lot of

time. But that's okay. We're used to this. Comets come and go as well. So we're used to these sort of shorter time spans of a couple of months to really focus on the object and get as much much information as we possibly can. So I guess no sleep till 2026. No vacations for Martin. And yeah. Stephanie, thank you so much for joining me today. Thank you so much for having me. And I'm really looking forward to what we figure out about this object in the future. Dr. Stephanie Milam, an astrochemist at NASA, and a project scientist for the James Webb Space Telescope. Up next, Banu. The Near Earth, Earth, asteroid we all know in love, also seems to have some family ties to a solar system far, far away.

What we're talking about here is what were the baby photos like, right? And now we're starting to piece together what's happened since then to sort of adulthood, which is where we are now. Back in 2018, the spacecraft Osiris Rex rendezvoused with Beno and after a long journey brought samples of dust and rock from the asteroid back to Earth. For the past two years or so, researchers have been analyzing those space pebbles trying to tease out details about Benu's origins and what it tells us about our solar system. And it turns out that Benu may have some secrets to share from outside our solar system too because findings just published indicate that the samples contain bits of stardust that are older than the solar system itself. Joining me now to talk about that is Dr. Jessica Barnes, an associate professor in the lunar and planetary laboratory at the University of Arizona. Jess, welcome to Science Friday.

Thanks for having me. So what did you find? Yeah, so we looked at a range of different samples from the returned material. And some of the investigators were studying or specifically looking for stardust. We know from meteorites that are analogous to Benu and other carbonaceous asteroids. we know that those materials are likely to contain star dust. And when you say star dust, are we talking about bits of exploded stars? Exactly.

So either stars that prior to our solar system went supernova, so exploded, or other grains that were formed in kind of star outflows. And believe it or not, once you know what you're looking for, they're pretty easy to spot in samples like these. they really pop out like a sore thumb. They're very what we call isotopically anomalous. And so they look isotopically very different to anything from our solar system. And when you say they're isotopically anomalous, is there a way to explain what that means? Yes. So what we mean by that is different elements can have multiple isotopes of themselves. So the element is the same, but the number of neutrons

in the nucleus is different. And so we end up with different isotopes. As an example, oxygen has three stable isotopes, oxygen 16, 17, and 18. And when we're looking at these stardust grains or looking for them, we're really looking for ratios of one of these isotopes over one of the other isotopes, an example being oxygen 18 over oxygen 16. We're looking at that ratio, and that ratio is very different to anything we see in our solar system. So we literally map the sample to look for these. little hotspots that indicate where we have these pre-solar materials.

Can you tell which stars they came from or which areas of the universe they came from? I mean, that would be amazing. At the moment, no, not really. What we can do, though, is we have observations of stars. We have models that tell us what to expect from different star types, so big, small, whether they go through a supernova event where they explode, they will encode in the dust that forms during those events, they will encode different signatures. And so what we do is we piece together what we see in the sample with what we know from those models and observations

to say what types of stars they might have come from, those grains. We can't tell you exactly which star these bits of star dust came from. Does this revise or expand our thinking about Benu's birth? It contributes to it. We were expecting to see these materials in Benu. I think one of the biggest surprises was the abundance of other types of these original components. So these would be the building blocks to Benu's parent asteroid or its ancestor, if you like. Because Benu right now is a near-ear earth asteroid, but it didn't always look like it does today.

It was once part of a much larger object. And that object accreted or assembled from what we now know are pieces of solid material from all across our solar system. So that's one of the big surprises that we find is that some of these original components are in much higher abundances in Benu than we previously expected. And so we find much more or higher abundances of material that we think formed close to our sun and also material that we think organic material that we think formed very far out in our solar system or even formed in interstellar space. That was one of the big key takeaways from our paper is that we think Benu's parent body formed

in the outer parts of our solar system. Hmm. What a long life, Benu has had. Oh, yes. Very complex. And we're just starting to tease out all the history. It's like going through someone's life record, right? What we're talking about here is what were the baby photos like, right?

And now we're starting to piece together, you know, what's happened since then to sort of adulthood, which is where we are now. Benu baby photos. I love that. I mean, it seems like you're finding out things that you can only find out with actual samples. Do you see this as an argument for going there? Absolutely. Some of the things that we find, most notably earlier this year, there were reports, a new report of salts from asteroid Benu. I mean, those types of measurements or findings can't be done on meteorite samples. Yes, we're finding here. and there evidence of some of those minerals in the meteorite record, but it's not, it's been affected by terrestrial alteration because just of the nature of meteorites. They have to fall through Earth's atmosphere to be recovered. And so some of the findings we're making are only possible because we've been there. And further to that, we're able to put what we're finding in the laboratory across multiple

labs across the world. We're able to put that in context because we've been to the asteroid. We've seen what the asteroid itself looks like. And that really helps us to put into context our measurements. What's next for you? For me, we're going to keep looking at these samples. We have a lot of work left to do. One of the things I'm most excited about the team, hopefully soon, submitting and then

later on showing off to the world is, you know, in the studies that have just been published, we're kind of giving you a snapshot of, you know, what did Benner? his parent body look like, what are those baby photos? What was its adolescence like? That's the aqueous or hydrothermal alteration story of how fluids were operating on the parent asteroid. And then how Benu's surface has been affected by being in space. It's exposure to cosmic rays and high energetic particles. Like, when did all of these things happen? So this is like Benu's full astronomical ancestry is what you're trying to figure out. Exactly. From from its birth at the beginning of our solar system.

You know, it's one of these bodies that was forming right at the beginning of our solar system, accreting and assembling from the original materials in our solar system, some materials from outside of our solar system. It's recording dynamic transport throughout the solar system to the edges where we think its parent body was forming all the way through to, you know, material being delivered to its surface today by, interaction with the solar wind. And it's whole entire history, which is a history we just can't get, like on Earth, we can't even get our initial history of Earth's surface because the crust has been destroyed over billions of years, that initial crust. So this is a huge lifespan that we're able to look at by looking at these samples. I am here for this intergenerational family drama.

Thank you, Jess. Please come back and tell us. when you find out. We'll do. Thank you. Dr. Jessica Barnes is an associate professor in the lunar and planetary laboratory at the University of Arizona. Thanks for listening. Don't forget to rate and review us wherever you listen. It really does help us get the word out and get the show in front of new listeners. Today's episode was produced by Rasha Aredi and Charles Bergquist. I'm Flora Lichtman. Thanks for listening.