CR = Claire Repsholdt, CP = Catherine PilachowskiView podcast page
The Milky Way Transcript
CR: Welcome to A Thing of Beauty. I’m your host, Claire Repsholdt, a senior in the College of Arts and Sciences at Indiana University studying English and History. This podcast is part of Themester, a themed semester brought to you by the College of Arts and Sciences. This fall we are exploring beauty as a core component of human experience. In each episode, we’ll invite faculty to share an object of beauty with us. So, let’s meet our guest.
CR: Welcome to A Thing of Beauty. I’m Claire Repsholdt, and today I’m here with Caty Pilachowski, who is a professor and Kirkwood Chair in the Astronomy Department of Indiana University. Welcome.
CP: It’s good to be here, Claire. Thank you for inviting me.
CR: So today you’ve chosen an object to talk about that is a thing that you find beautiful, and I wonder if you could share with us what that is.
CP: I picked the Milky Way. I don’t know if all of the listeners who are enjoying this podcast, I hope, have ever seen the Milky Way because it’s a phenomenon in the sky that is hard to see unless you’re in a very dark place and with so many people living in cities sometimes they don’t get to see it, but it is one of the most beautiful sights in the night sky, and it’s played a role in cultures around the world.
As an astronomer, I see it from a very different perspective, and, for me, it’s beautiful both because it’s intrinsically beautiful as we look at it--both in the night sky and in images that we can take with telescopes--and because it’s— it’s intellectually beautiful. It’s a challenge for us, sitting here on earth in sort of an out of the way corner of the Milky Way, to understand what it is and how it’s put together, how it was formed, what all of its parts are, and the story of all of that is what really makes it beautiful for me.
CR: And could you describe it a little bit for someone who has never seen it or maybe only seen it in pictures, try to give us some sort of physical understanding of what it looks like.
CP: Yes, so when we are out at a dark site and look up at the night sky, it’s a band of light that crosses the sky. It’s particularly bright in some times of the year when the earth is in the correct position around the sun. It’s laced with dark bands, so it’s— It basically is bazillions of really faint—or they’re bright stars, but they’re far away--and in front of those stars is a band of clouds of gas and dust that produce these dark lanes across the Milky Way, so if someone is located looking at the night sky in a dark site, when the sky is clear, the moon is down, the atmosphere is stable, the Milky Way is just really glorious. The detail that you can see with the naked eye is amazing, and literally you can look at it and imagine the structure of where we live in the universe.
From an astronomer’s perspective, we know that the Milky Way is a galaxy, and it’s a particular kind of galaxy. It’s what we call a spiral galaxy. When we look out at the rest of the universe, beyond the Milky Way, we can see many other galaxies that look like ours. It’s hard for us to see the structure from inside, but when we see these external galaxies we can sort of deduce kind of what our galaxy looks like, and then using that knowledge we can piece out what exactly our galaxy is like.
And so we know our galaxy is a disk of stars. That disk is about a hundred thousand light years across. So it takes light a hundred thousand years to cross from one edge of the galaxy to the other, but in the middle of this disk is a large bulge of stars—we call it the bulge—and it is a huge ball of stars. Those stars are very old. They are sort of the richest stars in the Milky Way.
We still don’t fully understand how that bulge of stars formed.
The disk is a mixture of old and young stars. It’s formed over a long period of time, and the stars are— They lay out a pattern of spiral. So there’re these arms that sort of emerge from the center bulge and spiral—can’t do this without using my hands—that spiral around the Milky Way. There are probably three or four spiral arms. It’s very hard to map them from inside, but we’re making progress on that.
And so what we see is a bright central bulge of stars surrounded by a disk of younger stars. The young stars are still forming. The spiral arms of the galaxy are where stars form and they contain dense clouds of gas and dust that are stellar nurseries; they are where stars form, and these newly forming stars align along the spiral arms. The older stars kind of spread out. They kind of disperse from the spiral arms over time and form a sort of an old, underlying disk that’s a backdrop for the bright young stars that we see.
And so this picture of the Milky Way is one that I find beautiful for so many reasons, but for me it’s beautiful to look at, but it’s the intellectual quest of understanding where we are, how it came to be, what the role of the earth and the sun are in the structure of the Milky Way and the history of the Milky Way, sort of how we fit in that big picture, and then understanding how our own galaxy, the Milky Way, fits into the larger structure and evolution of the universe as a whole. We learn all of that from studying stars in the Milky Way, and, for me, that’s— That’s truly what makes it beautiful.
CR: We could describe you as a historian of the Milky Way. Is that correct?
CP: That’s correct, yes.
CR: So when you became interested in that field, was it because you had seen the Milky Way? Or did you become interested in it as a scientific object? I guess, just, was it the sight that got you involved in it? Or was it, the, as you say, the intellectual quest to understand it?
CP: Well I’m a child of an urban environment, and, for me, seeing the full glory of the Milky Way didn’t happen until I went observing on a dark mountain down in Chile, in the Northern part of Chile. They have absolutely beautiful skies down there, very still, very dark. And I was there at a time when the moon was down, and because of the orientation of our earth the central part of our Milky Way, the bulge of our Milky Way, is never directly over head in the Northern Hemisphere, but it is directly overhead in the Southern Hemisphere, so it’s much more striking down there where we see the glow of this bulge, the dark lanes that obscure part of it.
So it was visiting that mountain in Chile to do observations with a large telescope down there where I really got my first crystal clear view of the Milky Way and could see exactly how beautiful it was, and by then I knew lots about the structure of the Milky Way and about the stars that make it up. I was there to study a particular group of stars that are part of our Milky Way.
I study star clusters, and so these are objects that form as a group together. They form in a cloud of gas and dust that produce a ball of stars. These clusters contain a hundred thousand to a few million stars. They’re just huge balls of stars. The Milky Way contains oh, about a hundred and fifty maybe two hundred of these star clusters, and these star clusters formed way back in the very earliest days of our Milky Way formation. So they formed about 12 billion years ago. They formed long before our sun formed, long before the earth was here. They’ve been around a long time.
These star clusters tell us about the history of the Milky Way. We learn that from studying the compositions, what the cluster of stars are made of, and from studying the motions of the clusters around the Milky Way. They orbit, basically, around the Milky Way. By studying their motions and their compositions, we can deduce some of the things that happened 12 billion years ago when these clusters formed, and that tells us about the early history of the Milky Way.
I was down in Chile to make observations of stars in one of these particular star clusters and was able to go outside. Normally, we observe in a control room and there’s a computer (CR: Right). It’s all very technical, but we take breaks and go out and look at the night sky, and I was able to see the Milky Way for the first time--really see the Milky Way--and it was just an extremely moving experience. It’s so beautiful. I wish all of the listeners could go out to a dark site when the Milky Way is up and take a look, see it, see what there is, and even better to see it from the Southern Hemisphere where it’s really true full glory is revealed.
CR: Is there ever a chance to see it in Indiana?
CP: Oh yes, of course, of course there is.
Um, the Milky Way is uh easy to see, um, once the sky is dark on a summer evening here um going outside in a dark area, so get out of town. You have to, y’know, get away from the city, get away from the lights of Bloomington or Indianapolis or wherever a person might be. Go out in the dark countryside away from the city lights, pick a clear night when the moon is not up in the-- in the evening. Wait ‘til it gets good and dark, and get dark-adapted. It takes about twenty minutes for our eyes to really adapt, to see well in the dark, so wait a good twenty minutes, and then it’s very easy to see crossing the sky, and it-- The best part is to look sort of South around the constellation Sagittarius and Scorpius because that’s where the center part of the Milky Way is, and listeners should be able to see the dark lanes and the bright swath of the Milky Way across the sky.
CR: Do you ever try to capture it when you see it? Is that part of your experience of it? Is for you-- I mean, when I say capture, in a photograph or a video or something— Or for you, is capturing studying it in a more scientific way?
CP: I love seeing it with my own eyes. The pictures, the images, allow us to sort of show it more clearly than one can see with a naked eye because the camera will integrate the light over a longer exposure time than our eyes can manage, so we see more structure, more detail when we have an image. But it’s, I think, much more beautiful to see just with my own eyes. So I will go out and look at it, but the work that I do as an astronomer doesn’t involve actually taking pictures of it. It’s just there for me to enjoy when I can see it.
CR: Mhm. And when you’re going back into your lab work--I guess it’s lab work--to study it, is that image always kind of where you’re beginning your inquiry? I guess, is your inquiry into the Milky Way part of the experience of seeing it, or is it a separate thing?
CP: It’s part of the experience. So because I really am interested in how the Milky Way came to be, what it is today every time I study a star or a star cluster. I have an intrinsic awareness of where that object is, where that star is now in space and time. Where is it in the galaxy? How old is it? How long has it been orbiting?
We know that at the distance of our sun from the center of the Milky Way--and the center of the Milky Way is about 26,000 light years from us, approximately--we know that our sun takes about 200 to 250 million years to make a complete orbit around the Milky Way. Our sun orbits around the Milky Way, and our sun was born about 4.5 billion years ago. So, fifteen or twenty times, our sun has made a journey completely around the Milky Way. Stars that are closer to the center orbit around faster. Stars that are further out orbit around more slowly.
We know in some cases that stars mix. They don’t always stay at the same distance from the center. That they may move inward, or they move outward. Our sun’s orbit is mostly circular, around the Milky Way. There’s a population of stars that sort of surround the Milky Way--not in a disk but around the full sphere--surrounding the Milky Way, and those stars have very eccentric orbits. That means that they-- They sort of dive into the center and then swing back out rather than being sort of circular around the Milky Way, staying at constant distance.
We know that those are the oldest stars in the Milky Way. They may even pre-date the formation of the star clusters that I study, and I study those stars as well. Studying stars of these different ages allows us to understand the characteristics of the Milky Way at different times in the past.
So when I say, “Yes, I study the history of the Milky Way.” I really do. I’m really looking at how has the Milky Way has changed over time; how has its chemical composition changed? How are the structures that are within it? How have they changed over time? How are they proceeding in the Milky Way? Is it growing still? What is its future?
We know that in about 3 billion years, that seems like a long time from now, but in astronomer-speak that’s not so far away, there’s another large spiral galaxy nearby called the Andromeda galaxy. It’s in the direction of the constellation Andromeda, and we know that the Milky Way and Andromeda will collide in about 3 billion years. They’re headed towards each other. It will take 3 billion years for them to get close enough, and as they do they will make kind of a beautiful dance of swinging around each other several times and finally merging together to make one larger galaxy.
The whole story of our Milky Way is just such a beautiful thing, and there’s so much we can understand about its past, its future: how the sun plays a role where it is and why it is the way it is, how it relates to the other stars, why the sun has the composition it does, why the earth has the composition it does, where the materials that we’re made of, the carbon and the iron and the oxygen, where those materials were formed. They were formed in stars in the Milky Way. How did they get into our earth? How did they get to form the sun? That whole story is part of the beauty that I see in the Milky Way.
CR: And so much of what you’re talking about I’m fascinated because of the way when you’re describing the movement of stars and the way that you study them, how much it sounds like people. It’s so personified, and you talking as a historian, it doesn’t sound very much different from the way that people study empires, except for the fact that these stars are exactly the things that we’re made of, the light and carbon as you say. So, at every moment when you’re studying, is the beauty that you’re seeing in it coming back to a human understanding of beauty. Or is it separate in some kind of impossible and cosmic way?
CP: I would say it does come back to a human understanding of beauty--that understanding the beauty that I see comes from understanding the Milky Way in detail and understanding not just as a visual artifact but as a changing sculpture in time and space, that it’s in constant evolution, constant motion. The motion is very slow. In my lifetime we will never see it. In the lifetime of human beings we will not see it.
But it’s nonetheless--over the long lifetime of the universe--it is changing and evolving and in constant motion, and it’s that balance of all of the forces of nature of the beginning and the ending, the balance of light and dark, the balance of all the different kinds of matter that make up the Milky Way, the dark matter, the light, the ordinary matter that we’re made of, all of these aspects: the fact that our Milky Way is basically a cannibal. It eats other galaxies. Right now it’s in the process of ripping apart a small galaxy called Sagittarius that was discovered about twenty years ago.
That galaxy has been shredded into a ring of stars that surrounds the Milky Way, and over time those stars will merge into our own galaxy and become basically indistinguishable from the rest of the stars of the Milky Way. That process of growing and changing and interacting with its environment-- All of those things together are combined to make this a beautiful thing for me, and understanding the complexity of our Milky Way is what makes it beautiful.
CR: And in your journey as a scholar learning about the complexity of the Milky Way and this pantheon of motion going on, has it changed your understanding of beauty as a person? Like, when you’re talking about beauty and it’s so involved in these enormous laws of time and these gigantic interactions, does that change the way that you encounter beauty in other places?
CP: I hadn’t thought about that. I don’t know. Beauty is such a personal thing and we all see it in different ways. I think, though, that the beauty of the Milky Way has to be something that not only every person, but every sentient being must be able to appreciate.
I cannot believe we’re alone in the Milky Way, and it seems to me that every culture that could exist in the Milky Way would understand its beauty. To me, I think that means that there must be some shared understanding of what is beautiful and that it crosses cultural boundaries, that it crosses personal boundaries, and I think it probably crosses planetary boundaries in some significant way. We may never meet E.T. out there in the universe, but if E.T. is out there, I’m sure she or he would feel the same way about the Milky Way that I do.
CR: So do you think, then, it’s not too much to say that beauty is an absolute experience or an absolute truth of some kind?
CP: I think it must be. I think this appreciation of the aesthetics, whether it’s visual or oral or musical, intellectual, emotional, there are many ways that beauty can be experienced. I’m not sure everything that I might think is beautiful you might think is beautiful. There are some things we might agree on, but I’m not sure beauty is experienced in the same way by everyone, everything. I think a significant part of that must be personal experience, but I think that there are some things like the Milky Way that probably everyone could agree on.
CR: I think that is an interesting part of the Milky Way that really nothing else can quite match is that you’re in it and yet you’re observing it, and it’s so incomprehensibly large. I think I always imagine being inside the Milky Way somewhere, whirling around, but I very rarely think and realize that it’s something that I can also just look at, as a more or less static part of the sky, and so that must be interesting, too, that you’re not only appreciating it as an external object of beauty, but something that you make up.
CP: Yes. I create this image in my head, structure, interaction, evolution, so it in a very real sense it is an intellectual beauty that I appreciate, and yet it’s a very real intellectual beauty. The Milky Way is an artifact. It’s a thing that’s complex, that’s ever-changing, but it is a thing. It’s an artifact.
It’s the case that our sun is located about two-thirds of the way out form the center, in the disk, so when we look toward the center of the Milky Way we’re really seeing most of it with our eyes. One of the things that I find, I don’t know, sort of disturbing is this image of what I would love to be able to do--and why I find it disturbing is because I know this is not possible--but to be able to get in a spaceship and travel faster than light and fly out above the Milky Way and look down to see its whole structure from above rather than being inside the disk, and that’s frustrating for two reasons:
One is that we don’t have faster than light travel, so we can’t actually do that. But the second reason is that, because of the way light works, the way it brightens and dims as a function of how far away we are from it and the way the size of an object appears as we get further or closer to it--so as we get closer to the Milky Way the stars are brighter, but they’re more spread out, so the actual visual brightness that we see doesn’t change as a function of distance.
So, if I could get in my spaceship and go out and look at the Milky Way from above. It wouldn’t look any brighter than it does from where I’m sitting on the mountain on a dark night. I would love to think I could fly out and see it as we do in photographs, which are long exposures, to reveal the-- (C: Layers) to allow us to see the faint light, but, in fact, visually it doesn’t get any brighter, which is very frustrating.
CR: That’s a fascinating part of it is that from even inside of it it’s almost the same as outside of it, (CP: Yes) which makes it all the more astonishing, maybe.
CP: Yes, yes. And I think that the true beauty of the Milky Way-- It is beautiful in the night sky, but this beautiful image that astronomers can produce of the Milky Way is not something people will see with their naked eye, just basically because of physics. And so it’s a thing that astronomers can contribute to our culture, to help people share the beauty, using the technology that we have developed over hundreds of years. That technology allows us to really appreciate the depth of the beauty of the Milky Way. I don’t think that takes away from the beauty that we see with our eyes. I think they’re very complimentary, and allowing us to understand it and study it I think helps us understand and appreciate the beauty that we see with our eyes. I think they really compliment each other.
CR: And is that something that most astronomers talk about? Are most astronomers thinking that they’re contributing to a human understanding or a human experience of beauty, or is that kind of a separate goal of your own?
CP: I certainly feel that way myself. I couldn’t say that most astronomers do. (C: Right) It is the case that people everywhere are interested in astronomy. When we’re riding on an airplane sitting next to somebody and they ask, “So what do you do?,” and we say we’re an astronomer, if I were to tell somebody, “yeah I’m an astronomer,” I know what’ll happen for the rest of the flight. I’ll be bombarded with questions about black holes and the origin of the universe and how far away things are, where stars come from and all of those things.
CR: So this interview is pretty normal for you—
CP: It’s pretty normal. Right. And this is a shared experience, I think, with all astronomers, we all-- We all love to talk about astronomy. It’s a part of our disciplinary culture that we love to share our research and our knowledge which is just about everybody and it— It’s often not discussed in the context of beauty, but I think that the reason that people are interested in astronomy in the first place is because it truly is so beautiful.
It’s not just the Milky Way. The Hubble Space Telescope has done a fantastic job of sharing with the public some incredibly beautiful images. As I prepared to speak with you, I went through a bunch of my favorite images and thought about, “Well how about this one” or “How ‘bout that one?” They’re all amazingly gorgeous, and I’m sure people have seen them.
It’s the beauty of those images that I think pulls people into astronomy and brings up questions: So what does this picture mean? What am I looking at? How far away is it? How did it get to be this way? It’s that beauty that pulls people in. It is just a beautiful, beautiful subject.
Basically, yes: I think that the beauty is an important part of it, even though when we interact with the public or we’re working on our own in our labs trying to do the work of astronomy, it’s not the foremost thing in our minds, but I don’t know anyone who works at a telescope that doesn’t go outside and look at the sky and say, “Wow it’s a beautiful night, isn’t it?” We go out and look at the sunset because it’s so beautiful, and so it fundamentally is part of our experience but not one we discuss in a sort of intellectual way.
CR: It sounds like it’s grounded in awe, kind of.
CP: It very much is, yes.
CR: You can’t-- You become able to talk about these things and study them from that awe of smallness or of complicitness in the Milky Way.
CP: Yes, that’s a big piece of it. It’s also the fact that human beings are small creatures on a small, small earth around a pretty ordinary star way out in the outer suburbs of the galaxy. and the intellectual accomplishment of understanding something that is so much bigger than we are in space and time, I think, is phenomenal, and my love of the Milky Way is a part of that. As one basic, simple human being, that I could comprehend this beauty and understand how it arose, what it’s all about; that’s an amazing accomplishment. And the… Oh… The ability of human beings to achieve that is what really, really is astounding I think.
CR: Why does beauty matter? Does it matter? And why?
CP: It inspires us. It’s what— It’s part of our appreciation of everything. The aesthetic, the-- For me, it’s not just the picture. It’s the entire knowledge together with the image that inspires me.
That’s because I’m an astronomer, and that’s why I became an astronomer. For a student, a passenger on an airplane, the beauty of the pictures is probably enough. They’re just lovely, but it’s that whole breadth of knowledge that goes together with the picture that I find most inspiring, and it’s the beauty part that makes it all work.
CR: Well, thank you very much for speaking to me about the Milky Way. I like to end our interviews by asking each interviewee to share a beauty tip with the listeners, so, for somebody who isn’t able to go to a mountaintop in Chile, something that they could do on this campus in this moment to find beauty.
CP: Every Wednesday evening Kirkwood Observatory is open to the public, and we have a 12-inch refracting telescope. It was built in 1901, so it’s historic, and we are able to use the telescope to look at planets and star clusters, beautiful things in the night sky, so I would encourage people to visit Kirkwood Observatory Wednesday evenings. There are schedules on our department website. Cloudy weather doesn’t work so much, but if it’s clear on a Wednesday night, come on over to the observatory, and take a look at the beauty of the universe.
CR: Great. Thank you very much I’m sure we’ll all be there the next clear Wednesday night.
CP: Whenever that is.
CR: Is there anything going on in our night sky, in our universe, that we should know about to look for in the next year or so?
CP: Oh yes, next summer, Summer of 2017 in August, there will be a total eclipse of the sun. It won’t quite be total here in Bloomington. It’ll just be partial, but down in Kentucky, it’s not very far away, that eclipse will be total. I once saw a solar eclipse. I guess it was around 1979 in Washington state, and it was the most amazing experience an absolutely wonderful thing. Everybody should see one.
So please please please everyone should put on their calendar, next August, to plan to go down to Kentucky to see this solar eclipse. We’ll have to hope for clear weather, hope that it’s visible but a total solar eclipse is an amazing even and I very much encourage listeners to plan to go see that eclipse next August.