Short Wave - An Interstellar Wanderer Is Coming Our Way

Episode Date: December 3, 2019

Comet 2I/Borisov will reach its closest approach to the sun on December 8, 2019. We talk to planetary astronomer Michele Bannister about where the heck this comet came from, and what it tells us about our galaxy. Follow Maddie on Twitter — she's @maddie_sofia. And email the show at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Hey, Maddie here. So here's the deal. The team here at Shortwave, we work really hard to bring you these episodes every weekday. Each day we come into work and try to bring you fascinating stories told by new and diverse voices in a way that's not just informative, but is honestly fun to listen to. It's work that we love doing and we want to keep doing it, but in order to make that possible, we need your help. The good news is helping out's pretty easy. Just go to donate.mpr.org slash short to find and support your local public radio station. That support keeps this podcast coming to you. Again, donate.mpr.org slash short. And thanks. Okay, let's go. You're listening to Shortwave from NPR. This Sunday, December 8th, an interstellar traveler, an object from outside our solar system, known as the comet two-eye, borisov, will make its closest approach to the sun. It's only the second

interstellar object we've ever detected, hence two-eye. And the comet was discovered by a man in Crimea named Ganadi Barisov. Now, Ganadi's actually discovered several comets already. I had seven discoveries of the comets. And then back in August, just around sunrise, he was looking through his telescope, peering into space, and just in the corner of his field of view. I looked moving object, a little different direction from the asteroids. At first he thought it was just a regular, smegler comet from inside our solar system.

But it wasn't. Ganadi Borisov had discovered an interstellar comet. The comet is new and have new name, Borisov. The Hubble Telescope even published an image with his name on it. I very happy that Hubble's telescope take images this comet and I see on the photo my name. But sometimes fame can be exhausting. After discovers, I have many, many telephone, many video, TV, comment,

and I want to rest. Understand me? While Ganadi gets some well-earned rest, we'll get the lowdown on 2i, Borisov, from Michelle Bannister. She's a planetary astronomer at Queen's University Belfast. So today we're talking to Michelle Bannister. She's a planetary astronomer at Queen's University Belfast, and she's actually studying the comet.

All right, Michelle, let's start off with one that I'm pretty comfortable that you're going to know. What is a comet? You can think of it as either a dusty ice ball or an icy dust ball. So it's one of the first building blocks that forms in a planetary system. in the dust and gas that's orbiting around a newly forming star and condensing into new little worlds. And some of these will be tiny.

Some of them will be the size of a city block. And some of them will be really big. They'll be the size of an island or a continent. And so a comet is at the end of the continuum between really rocky things, which we term asteroids, and more icy things, which we term comets. So how do they form? I wish we knew.

Seriously, this is one of the biggest problems and really most exciting research questions that we have in planetary science at the moment. So you have to go from dust that's the size of micrometers, right? Smaller than the diameter of dust that you find under your sofa. And you have to collect that together and make dust bunnies. And then you have to form it into things that are about a meter or so in size. And then you have to get those to stick together in a way that you end up with what we might think of as asteroids or commons. It's hard. Yeah.

And I feel like from time to time a comet kind of shows up, you know, like I think Haley's comment is one. Then there was the Halebop, that sort of thing. Where did those comets come from? These are comets from our own solar system. So there's a number of different reservoirs of small bodies, of little minor planets in our solar system. The big one for comets is called the Ord Cloud.

And the Orch Cloud is out between 30 and 50,000 times. further from the sun than we orbit the sun here on Earth. Cool, cool, cool, cool. So the comment we're talking about today, 2i or Borisov, is different, right? That it doesn't come from within our own solar system. It came from another star. It's forward a really long way away.

Yeah. I mean, this is so much fun. Like, just when in astronomy do you actually get to have something come close, right? We're talking about, normally we look into the sky and we're looking back in time. We're seeing stars as they were a very, very long time ago. The light has taken millions of years or longer to travel to us. But with this, we're dealing with a comet from another star that has traveled to us.

Yeah, that's really exciting. So do we know where the comet came from? We don't. So planetary systems, I was saying earlier, you form comets and asteroids and other little worlds. as part of how planetary systems form. But planetary systems make trillions on trillions of these little worlds. And so every planetary system that forms around a star in our galaxy will produce trillions of worlds

and scatter them throughout the galaxy as it forms and evolves. So in many ways, planetary systems are not just good at making planets, like our own Earth. They're really good at making interstellar objects. And these just wander between the stars. So they can encounter other stars. They can encounter, you know, all the things in the galaxy, black holes, you name it. And that will change the direction that they're traveling through the galaxy.

Right. Even when we have that information, it's very hard to trace back the path of a particular interstellar object and say, ah, that's its home star. Because what we might be seeing is just its last port of call. So the next planetary system that sees it, they'll think it came from us. Right, right. So because it's affected by different stars and that kind of stuff, and those change its trajectory, we can't really tell exactly where it came from. Exactly.

But what we can do is look at the populations. As we discover more of these with upcoming observatories like the large synoptic survey telescope, which is under construction in Chile, that should discover on the order of an interstellar object every year in the coming decade. So we're going to have lots of these to start to work with. Right. And you actually have been studying Borisov yourself. a little bit, right? What are some of the observations that have been made so far from you and others? Well, I actually was just helping observe Borisov right before I walked in here to chat.

Oh, just no big deal I was studying the comet before I came in this morning. It's been a really busy time of it, yeah. So what have we actually learned about 2i or Borisov about what makes it up so far? What we know so far is Borisov is a comet very like what we have. in our own solar system. Huh. It could be a regular or cloud comet. Whatever star it formed at could be nearby,

could be halfway across the galaxy. That star, that planetary system it was forming, it's a lot like our own. Right. Because planetary architectures, you know, this is one of the great findings of the last decade in astronomy has been that planetary systems all across the galaxy,

everywhere we look, are incredibly varied. Yeah. Right? We see huge planets close to their star. We see planets strung out like a string of beads and a neat little ratio all the way out from their star. We see incredible variety. But the chemistry that's going on in at least one star, somewhere in the night sky, in our galaxy, is like what we have here at home. That's kind of awesome, isn't it?

I think it's pretty profound. And this is something that ties in very deeply to how we understand and study the universe. because one of the fundamental things that we have to do is say what we can see here, the physical properties we can measure here, the laws of physics we can measure here, that those extrapolate, that they make sense to understand the universe that we see as a distance. Yeah. And this is a test of that. We have measured the things here in great detail, the comets and asteroids in our own system,

and then we have a test. We have a piece of another one from somewhere else that's come to us. and it's the same. I love it. That's so cool. It's telling us we have a great commonality across the galaxy. And it's like a little bit of, especially these ones that come from outside of our solar system, it's like a little sneak peek into planetary systems other than ours. That's why I'm so jazzed about them.

It's great. Yeah, we really have these little samples where we can start to take a deep look into how things form. elsewhere and how they form here and see where they're similar and where they differ. Yeah. What's the most, I mean, is that the most exciting part for you? To me, the most exciting part is that this is, in a much larger sense, changing the way that we think about the formation and evolution of planets through the history of the galaxy. And I think this is something that's really going to start to pick up over the next couple of years as we have more interstellar objects and as the people who do theoretical astronomy really

start getting their teeth into this kind of question. Right. Wow. Okay, well, this is really great. What a time to be alive. Am I right, Dr. Bannister? It's absolutely wonderful. I mean, at the moment, right, myself and my colleagues around the world, we're trying to figure out how to observe this with all different telescopes. We're writing emails to each other all through the day and each morning going, how did you're observing, go, oh, I got this. Look, we have this new molecule. Oh, that gas species is starting to become visible. You know, it's great. It's just, it's so exciting and it's a lot of fun working together on this. Well, I appreciate you and I appreciate your time. This was really fun. Thank you. This is great.

This episode was produced by Rebecca Ramirez and barely edited by Jeff Brumfield. Stacey Abbott made us sound better, literally. Plus, we had so much engineering help from Zach Coleman. I'm Comet enthusiast Maddie Safaya. This is NPR shortwave. We'll see you next time.