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

FLORA LICHTMAN: Hi, I’m Flora Lichtman, and you are listening to Science Friday. Today in the show, a space bonanza, starting with a strange visitor from another solar system.

STEFANIE MILAM: 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.

FLORA LICHTMAN: 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 3I/ATLAS. It’s only the third interstellar object that we have 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. Stefanie Milam. She’s an astrochemist at NASA and a project scientist for the James Webb Space Telescope. Stefanie, welcome to Science Friday.

STEFANIE MILAM: Thanks so much for having me.

FLORA LICHTMAN: Tell us about when you first met this object. When was it spotted?

STEFANIE MILAM: 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–

FLORA LICHTMAN: Of course.

STEFANIE MILAM: –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.

FLORA LICHTMAN: OK, so you got word that there was this interstellar object, and basically you were like, it’s go time.

STEFANIE MILAM: Right. So the principal investigator of the program, Martin, is a very close colleague of 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.

FLORA LICHTMAN: You know it’s desperate when you’re Facebook messaging.

STEFANIE MILAM: And nobody could get a hold of him. So we contacted the observatory, and we said that we were 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.

FLORA LICHTMAN: OK, so you’re marshaling 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?

STEFANIE MILAM: So this is only the third interstellar object that we know of that has come into our solar system. The first interstellar object was called Oumuamua. It was 1I. So “I” means interstellar. The number before the I is the number of objects. So 1I Oumuamua was the first interstellar object.

FLORA LICHTMAN: We know Oumuamua on this show. We’ve been following the Oumuamua drama on this program.

STEFANIE MILAM: Right.

FLORA LICHTMAN: Yeah.

STEFANIE MILAM: 2I Borisov was the second one. And it was more comet-looking than Oumuamua was. But that was in 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 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 can try to convince them that comets and interstellar objects is where JWST needs to focus.

FLORA LICHTMAN: OK, so what is Atlas?

STEFANIE MILAM: 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.

FLORA LICHTMAN: Tell us a little more. What’s this comet made of?

STEFANIE MILAM: 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.

FLORA LICHTMAN: Is what it’s made of, does that relate to its journey or where it comes from?

STEFANIE MILAM: 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 burnt cookie crumbs? Are we seeing fresh chocolate chips? What have 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 system’s.

FLORA LICHTMAN: That’s fascinating.

STEFANIE MILAM: Yeah. And if so, that means that that planetary system potentially had the same 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.

FLORA LICHTMAN: And does it look like the objects in our solar system, or is it too soon to tell?

STEFANIE MILAM: That’s the hard part. So the only way we see these kinds of carbon dioxide-to-water ratios in other planetary systems is when these objects would form way, 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.

FLORA LICHTMAN: Yeah, it’s like a peephole into another place and time, it seems like.

STEFANIE MILAM: Exactly.

FLORA LICHTMAN: Do we know how long this comet has been traveling for?

STEFANIE MILAM: Well, we don’t really know how long, but 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.

FLORA LICHTMAN: And when does it leave? How much more time do you have with it?

STEFANIE MILAM: So we don’t have a lot of time. But that’s OK, 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 information as we possibly can.

FLORA LICHTMAN: So I guess no sleep till 2026.

STEFANIE MILAM: No vacations for Martin. And– yeah.

FLORA LICHTMAN: Stefanie, thank you so much for joining me today.

STEFANIE MILAM: Thank you so much for having me. And I’m really looking forward to what we figure out about this object in the future.

FLORA LICHTMAN: Dr. Stefanie Milam, an astrochemist at NASA and a project scientist for the James Webb Space Telescope.

Up next, Bennu, the near-Earth asteroid we all know and love, also seems to have some family ties to a solar system far, far away.

JESSICA BARNES: 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 adulthood, which is where we are now.

FLORA LICHTMAN: Back in 2018, the spacecraft OSIRIS-REx rendezvoused with Bennu 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 Bennu’s origins and what it tells us about our solar system. And it turns out that Bennu 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.

JESSICA BARNES: Thanks for having me.

FLORA LICHTMAN: So, what did you find?

JESSICA BARNES: 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 from meteorites that are analogous to Bennu and other carbonaceous asteroids, we know that those materials are likely to contain stardust.

FLORA LICHTMAN: And when you say stardust, are we talking about bits of exploded stars?

JESSICA BARNES: Exactly. So either stars that prior to our solar system went supernova, so exploded, or other grains that were formed in 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.

FLORA LICHTMAN: And when you say they’re isotopically anomalous, is there a way to explain what that means?

JESSICA BARNES: 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.

FLORA LICHTMAN: Can you tell which stars they came from or which areas of the universe they came from?

JESSICA BARNES: 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 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 stardust came from.

FLORA LICHTMAN: Does this revise or expand our thinking about Bennu’s birth?

JESSICA BARNES: It contributes to it. We were expecting to see these materials in Bennu.

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 Bennu’s parent asteroid, or its ancestor, if you like, because Bennu right now is a near-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 Bennu than we previously expected. And so we find much higher abundances of material that we think formed close to our sun, and also 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 Bennu’s parent body formed in the outer parts of our solar system.

FLORA LICHTMAN: What a long life Bennu has had.

JESSICA BARNES: Oh, yes, very complex. And we’re just starting to tease out all the history. It’s like going through someone’s life record. 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 adulthood, which is where we are now.

FLORA LICHTMAN: Bennu 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?

JESSICA BARNES: Absolutely. Some of the things that we find, most notably earlier this year, there were reports, a new report of salts from asteroid Bennu. 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 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.

FLORA LICHTMAN: What’s next for you?

JESSICA BARNES: 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 giving you a snapshot of, what did Bennu’s 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 Bennu’s surface has been affected by being in space, its exposure to cosmic rays and high energetic particles. Like, when did all of these things happen?

FLORA LICHTMAN: So this is Bennu’s full astronomical ancestry, is what you’re trying to figure out.

JESSICA BARNES: Exactly; from its birth at the beginning of our solar system. 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 material being delivered to its surface today by interaction with the solar wind.

And its 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.

FLORA LICHTMAN: I am here for this intergenerational family drama.

JESSICA BARNES: [LAUGHS]

FLORA LICHTMAN: Thank you, Jess. Please come back and tell us when you find out.

JESSICA BARNES: Will do. Thank you.

FLORA LICHTMAN: Dr. Jessica Barnes is an associate professor in the Lunar and Planetary Laboratory at the University of Arizona.

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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 Aridi and Charles Bergquist. I’m Flora Lichtman. Thanks for listening.

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