Galaxy Quenching

Oh wait, you're listening. Okay. Okay. Okay. Okay. Okay. You're listening to Radio Lab. Radio Lab. From WNYC. See? Yep. The place I really want to start is I wonder if you can tell me about all the different ways a galaxy can die. Okay, so a galaxy can die or quench in a variety of different ways. Wait, and I'm already going to stop you because that word quench. Yeah. Does that mean like galaxy dimming, galaxy dying? Yeah, we call death in kind of a way or a dimming of sorts. Yeah. Got it. So I would define it as any process that prevents star formation from happening. Okay. And for stars to form, you need cold dense gas. Hmm. You can think of cold dense gas, mostly hydrogen, as the fuel for star formation. Okay. And so ways that the galaxy quenches is when the stars can't get that fuel? Yeah, exactly. So like what makes that fuel not get there? Well, for example, the supermassive black holes that exist in the center of every massive galaxy. Those supermassive black holes can heat up that gas or the supermassive black holes can have these jets that'll actually expel the gas outside of the galaxy completely into the intergalactic space. Okay. So then the stars just kind of starve? Yeah. And that's a term that actually is used in galaxy quenching. It's called starvation because some of this cold gas can come into the galaxy from what we call the cosmic web. Okay. So if that process gets shut off for some reason, then we call that starvation. So it's like it could get pushed out from the inside or it just stops coming in? Yeah, exactly. Huh. There's starvation, strangulation. Yeah, I'm not sure why these words are so violent. I feel like we could have come up with better ones. The current scientific thinking is that there are at least eight ways that a galaxy can die. That's the theory. The charity Woodrum has spent her career actually looking, trying to observe the physical processes that make them dim and sputter out. I'm Lulia Miller and today on Radio Lab, we have a story of something almost mythic that charity observed in the darkness. Something I didn't know could happen in space, something charity never expected to see. Something that would nudge science forward in its understanding of how galaxies evolve. And something that would end up nudging her forward ever so slightly through an unthinkable loss. How did you get interested in this morbid branch of astrophysics? Should I start with all the way back to how I got involved in astronomy and jazz? How the heck did you end up studying how galaxies die? So I grew up in rural Oregon in a small town called Canyonville. When you grow up in a rural area like that, you get to see the milky way. And so being under the dark night sky certainly affected me and it was certainly a place of peace for me growing up. Was it contrast to like in the house, in the school, anything like that? Yeah, I would definitely say that there was chaos at home. Both of my parents at one time were addicted to some type of drug. My dad, I think one of the words people would use to describe him would be violent. And I think as a distraction, I would go out and look up at the night sky, just be in the backyard, just walking into the grass and laying down in the grass, sometimes with a sleeping bag, you know, under the trees and just looking up at the night sky. Yeah. I was thinking a lot about how big the universe is and how even though I was in my small town that the world was a lot bigger, the universe was a lot bigger and there was just more out there to explore. At a young age, I asked one of my middle school teachers what I could do to work for NASA someday and he laughed at me. Like a cruel, it was like a chuckle. I don't think he was trying to be cruel because at the time it didn't make sense to me. I was the valedictorian of our high school, but you know, looking back, my graduating class only had 17 people and he also knew my family history. Neither of my parents graduated high school and just, you know, we grew up in a very low income area and so I think he was seeing all of that. There were no other scientists in that town. A lot of the jobs would either be logging or going to nursing school, but I had never heard about a scientist before. At the time I was like, okay, I don't know how to do this then. So then what do you end up going on to study? What's the next chapter? So once I graduated high school, my biggest goal I guess was to escape poverty and I became a registered nurse. But once I started working as a nurse, I couldn't handle the emotional toll of it. Seeing human suffering on a daily basis, like an older person not getting visited or even, you know, once a week there would be something absolutely catastrophic that you would see and I found myself just thinking about it all the time and it was really affecting my daily life. So at the time, Jason, what would be my future husband, one of his coping mechanisms was to read books. He read, you know, hundreds of books a year. Whoa. And yeah, he was like, why don't you pick up some books? Maybe that will get your mind off of it. I started picking up popular science books by, you know, like Carl Sagan and Stephen Hawking and started reading about those. There's a particular image actually itself that's one of the main reasons that I went back to school to study physics. It's called the Hubble Deep Field. Hubble Deep Field. Okay. I encountered it in one of those books and basically this image, how it was made was they found the darkest part of the sky. So as far as we knew, there was nothing there. And Sonos Johnar said, why don't we point the Hubble Space Telescope at this dark patch of sky for 10 days, which was a very kind of bold and crazy move because Hubble Space Telescope time is very precious and expensive. And some people thought nothing would be there. Like why point it in complete darkness? And yeah, they used Hubble to stare at this dark place in the sky for 10 whole days. And then the image that came back had thousands of galaxies in it. Thousands. Thousands? Yes. You can easily pull this image up. Just Google the Hubble Deep Field. It looks like someone threw glitter on a black floor and there's like some bigger pieces that feel closer. And there's all different colors. I see greens and yellows and oranges and blues and whites. And so are each one of those dots a galaxy? If it's very bright and has those spikes around it, it's a star with, you know, a star in between us and those galaxies, but everything else is an entire galaxy. Wow. She said you could also see where the dying ones are. There's some red orb galaxies in there. Oh, there are? Yeah, yeah. Oh, they kind, are they like these orangey ones? Yeah, they're really red. We call them quiescent galaxies when they're red and dead like that. Oh, quiescent like quiet or dormant, like it's there, but it's not making new stuff. Right, exactly. And so I was just sitting there staring at that image. Each of those galaxies has billions of stars and each of those stars we think has at least one planet. Wow. And I don't know, it kind of gave me the feeling that I got as a kid laying under the night sky. And it also just kind of calmed me. I wasn't thinking about that human suffering that I was seeing on a daily basis. I was actually nine months pregnant when I walked into an academic counselor at the University of Oregon and said, hey, I'm a registered nurse, but I want to go back to school for physics. Wow. He looked at me like I was crazy a little bit. But around the time when I was pregnant with my son, I was thinking about what type of person I wanted to be for him because I wanted him to pursue his biggest dreams. And I felt the only way to do that was to pursue mine. And how was that going to work? What was Jason doing? He had a soil company business. He would literally sell dirt to people. He loved soil. That was his big passion because he loved reading about all the bacteria and the soil and how it was alive and all of that. And so we always made the joke that whenever he was looking down, I was looking up. So at first, I have a new baby now and I'm starting my first term. And so I wanted it to be a little bit easier and only be gone away from Woody for an hour or two a day. I didn't want to be away from him for too long. Was Woody short for anything or Woody is given name? Yeah, that was his given name. So, okay, Woody's a little baby. Yeah. So, on the first day of class, I met Dr. Scott Fisher, who was an astrophysicist. And he wasn't Stephen Hawking or Carl Sagan. He was like a normal person that had this job that I... And that was the first time I realized, like, oh, I could actually have a job in this field. You have a job. You got healthcare. You got the salary. Yeah. And you get to think about this stuff. Exactly. I was like, okay, that's what I want to do now. So after taking that first day of class in Dr. Fisher's class, I started bugging him every day and I would just go to his office and ask him if I could join his research group. And he'd be like, you know, my research group is full. Come back later. So I'd be like, okay, come back a week later. A week later? Yeah, I was really annoying. And so he said, you know what? His boss had a research project for a student. And so she asked if he had any students and he was like, well, there's this one girl that won't give up. So let's go with her. And she worked in the field of galaxy evolution. The research group was charity and three other undergrads and they called themselves the cosmic wolf pack. And together they taught themselves how to read the flickers in the sky, how the blue ones were newborns and the red ones were dying. She said they often get yelled at for squealing too loud when some new image came back showing galaxies of beautiful colors or shapes, clusters. Almost every weekend over the summers, I would go up to Pine Mountain Observatory giving people tours of the night sky with one of the bigger telescopes up there and Jason and Woody would camp. And before Woody's bedtime, they would be in the dome with me as I was talking about the night sky. And then they would go sleep in the tent and wait for me to get done, which would be much later, much past Woody's bedtime. The first year I would have to go back to breastfeed him quite often. So I actually would have to shut down the dome and say, I can hear my baby crying in the distance. He's hungry. And so I would go feed him and then come back. In the sleeping bag, just like cozyed up. Yeah. So this must have been when he was around two years old, there had been a lot of cloudy nights all in a row. And we stepped onto the porch one time and it was a clear night sky and he looked at me and he said, oh, thank you, mom. I said, for what? And he said, for turning the stars on. So he thought that when I was giving people tours of the night sky that I was the one that turned the stars on at night, I guess. And I looked at Jason and he was crying. Was it like a battle with Jason? Was Jason like, Woody, look at the soil. And he was like, Woody, look at the stars. And he won. Um, no, I would say it was quite equal because Jason loved vegetable gardening. And so Woody was often in the garden with Jason and they would come inside and to eat lunch and then leave again back to go gardening. And I knew where they sat because there would be four little piles of dirt from where they had sat down. Yeah. Um, yeah. And he was, they were both very sweet. Um, at what point do you learn about rejuvenation in this story? So that happened when I was in my second to third year of graduate school. And can I just ask like for setting in time, is this before or after the worst day? This is after the worst day. So the worst day happened my junior year, um, in the physics program. Um, okay. So I guess for chronology, maybe we, we do this to the degree that you want to, however you want to talk about it, do you want to, do you want to take a break first? Do you want to just plow through? How do you want to go? Let me take a sip of water real quick and then I will. Yeah. We'll be back in a moment. When the economic news gets to be a bit much, listen to the indicator from planet money. We're here for you like your friends trying to figure out all the most confusing parts. One story, one idea every day, all in 10 minutes or less. The indicator from planet money, your friendly economic sidekick from NPR. I guess just, can you say what happened on January 15th, 2017? Yeah. So it was a long weekend and me and my son and husband decided to take a mini vacation to the Oregon coast. Um, and it was especially sunny on the Oregon coast for it being wintertime. And a lot of people that are not from the Pacific Northwest might not know about this, but there's these things called sneaker waves and we were walking along the beach and the water would come up to the same place every single time and I was walking a little bit ahead of them and one of those sneaker waves, you know, hit them and, and, and swept them out to sea. My memory, you know, fades in and out on that day. I eventually found myself in an ambulance and my eyes were closed and I felt a banging on my head and I woke up and realized I was hitting myself in the head saying, you know, wake up. This can't be real. And you know, then I realized it's getting dark outside and I had heard that the Coast Guard was going to call off the search once it got dark. And so then I, I guess I started freaking out because apparently I jumped out of the ambulance door through the back and just started running towards what I thought was the ocean, but I actually didn't see the ocean nearby. I didn't know where I was. I'm barefoot. One of the cops, you know, pulls me back into the ambulance. And I guess I did that a couple of times. Yeah. Eventually they drove me to the hospital and I guess I was just screaming a lot and, you know, couldn't, I was just screaming. And so a nurse came up to me and had a pill in her hand and she said, do you want to just fall asleep? And I took that pill. And I was hospitalized like that for about five days, I believe. I woke up and I realized, you know, it made national news that, you know, Jason and Woody had been, you know, swept out to sea. Is there anything in running through the field? Was it like wanting to find them? Was it wanting to join them? I feel like it was, I was trying to, I realized they weren't going to search for them anymore and I wanted to find them. I think that was my intention. They took that as me being suicidal. I didn't, I didn't think, I didn't think I was, but I've heard people say that they thought that I wanted to join them. So they sent me to a psych ward. But the next morning I had a meeting with the psychiatrist there or the psychologist and I said, I can't be here. There was nothing to do. There was, there were books, but I found that I couldn't even read. I would try to read and I couldn't even read. Meaning you couldn't make sense of the words or you just, it felt too flat. Like it didn't, it felt like I, I was reading the words, but I wasn't processing them if that makes sense. It's, I've never tried to describe that before, but yeah, I couldn't read the books. And I was afraid to watch any TV because if a scene of the ocean would come up, I would have a panic attack. And so that's what the first week looked like basically. So after being released from the hospital and, and the psych ward, there's no way I could have walked back into the house that I shared with Woody and Jason. I went and stayed with close family. And those first few weeks, I, I didn't leave the couch really. I would just lay there and laying on that couch. I really felt like I could feel the life going out of me because there was nothing left for me I felt like. Where do you go? Yeah. Um, so I knew I had to do something and I knew that laying on that couch wasn't going to get me that desire to live back. And I remember people close to me, they apparently had this group chat and they always made sure that one of them was at my house with me at any given time for those first few weeks. And they knew that as a kid, I loved school and thought it would be a good distraction for me, I think. And so they said, why don't you go back to school? And actually when I told Dr. Fisher that I wanted to go back to school during that meeting, he was crying and he said, you know, your life is turned completely upside down. Nothing's the same. So if you want to come back to the research group, the research group would be exactly the way it was before. This can be the one spot that never changed. Hearing him say that was a huge reason I was able to go back. But when I went back to school, when people would see me for the first time, their eyes would kind of look like a deer in headlights, like, oh no, what do I say to her? And also I looked very different. I normally wear a lot of bright colors, but I was wearing the same black hoodie and black leggings every day. And I was 15 pounds lighter. And I think I wanted people to see that I was different now. I wasn't the same person I was. But at the same time, seeing their reaction, that was hard. So she looked up. I'm an extra galactic astronomer, so I study galaxies outside of our own. To do that, to find those distant galaxies, what you have to do is exactly what they did with the Hubble Deep Field. You have to find the darkest part of the sky and look at it. And that's literally what I do, is just look in the darkest places and try to find light there. She graduates college, starts grad school, and keeps looking into the dark day after day. And when she'd see a faraway sprinkle of galaxies, she'd focus in on the red orbs. The dying ones. The dimming ones. And she'd perform autopsies, trying to figure out whether it had been something from the outside or the inside, which caused it to lose its light. Day after day. Galaxy after galaxy. And then one day, 1,639 days after the worst day. She saw something odd. She was looking at this one group of 8 dimming galaxies. They were massive, quiescent galaxies. Quiescent, which means they were not making new stars, so they're that kind of like holding pattern red, slowly dying, but still emitting light. Bybe. Uh-huh. And getting the data back, the first scientists that looked at these galaxies found that four of the massive quiescent galaxies had cold gas reservoirs, and four of them did not. Yeah, we do know that cold gas reservoirs are the fuel for star formation. And so was that at first puzzling? Because you're like, the whole thing about why they die is like, it's pushed out, or it's heated up, or it's ejected, or it's, and you're like, but the food is right there. It's there. Yeah, exactly. So why do some of them have the cold gas reservoirs and some of them don't? So she started measuring everything she could think of, sort of taking the vitals of those galaxies with cold gas reservoirs. She looked at their metal composition, their growth charts, how they had grown in stars and mass over time. One of the things that I was able to measure was what's called the star formation history of the galaxy. So think of that as on the y-axis, there would be the star formation rate. So how many stars these galaxies are forming per year? And on the x-axis, you have time. And so their early star formation histories, when they were younger galaxies, those all looked quite similar. However, in the last billion years, all of the galaxies that had the cold gas reservoirs in the last billion years of the galaxy's life, there was a bump in their star formation. There was this significant amount of what we called secondary star formation episodes, or rejuvenation. Wait, so meaning like these dying, dimming galaxies, the ones that had the gas were making new stars from a place of death? Yeah. What? Yeah, and people had seen rejuvenation before, but I don't know that anyone had seen cold gas reservoirs in massive quiescent galaxies and saw that they also had rejuvenation episodes. You saw the physical matter of what it takes to come back to life for a galaxy. Yeah, exactly. Then does it still sputter out, or could it ever get back into real star formation? Could it ever keep going and get alive again? Yeah, definitely. Oh, it could. Yeah, just like with the physical processes that can make a galaxy quench, there's physical processes that can make a galaxy rejuvenate as well. Broadly speaking, there are four main ways that a galaxy can come back to life. One, it can happen from within. The black hole at its center surges with an unexpected burst of energy that allows new stars to form. The rest of the ways happen from without a sudden inflow of gas, a huge collision. Two galaxies collide and eventually form one galaxy together. Or wildest to me, and what Charity believes caused rejuvenation in the galaxies she was looking at, just a little boop. If two galaxies even interact with each other and do a fly by, where they just fly by each other, that little interaction can cause bursts of star formation as well. No. And can bring it back to life just like a drive by encounter? Yeah, just like seeing a friend and it lifts your mood. My childhood best friends, they're the biggest reasons I was able to survive and make it to where I am today. When I was laying on that couch, the people coming over and helping me had no reason to do other than that they loved me. And I don't think a lot of people get to know who those people would be in your life, and I know who they are. There was her brother. He sat me down and told me, you know, me and his wife Gina and the artist Claire wrote a song for you and we want to play it for you. They weren't afraid to talk to me about what happened. They just wanted to be there. There was the Cosmic Wolf Pack. You know, they just, yeah, they were exactly what I needed. And even random strangers. A woman online saw my story and she said, hey, I don't know how to help you, but I think my friend Lynn can because she's been through something just as tragic. And so Lynn offered to meet up with me and we had dinner. She had lost three daughters and a husband. And so I felt like just being around her felt like it was the first person that could understand what I was going through. And we would be at dinner publicly crying and talking to each other about our grief. And then she would invite me to events and at these events she would be laughing and full of life to the point where everyone in the room wanted to be around her because of it. You know, she's like, come bike riding with me, come to the opera with me. It was just the first time that I could see that you can carry the heavy grief with you, but you can also still have happiness again and maybe even hope. She had something that dimmed her light just as much as mine did, but she was able to come back again. And then I would think about the field of galaxy evolution in general and how when galaxies interact, actually the gas can flow between them. And so gas could flow from a star forming galaxy to a quenched galaxy and ignite star formation in that way. After meeting Lynn, I decided, you know, I needed to find things that gave me joy again and that I can do astronomy and astrophysics for myself as well as for Woody and Jason. And I could, you know, I could be happy again and it would actually honor them because early on in grief, you feel like you have to be sad all the time or something, but that's not going to honor them. And I think Lynn showed me that. I did find out recently that a colleague lost a loved one in her life and I reached out to her and said, you know, hey, the kindness of strangers once helped me through my early days of grief. And we went on a hike actually a couple of days ago. Yeah. What was it like to be the the Lynn to her charity? I mean, it was it was rewarding and and yeah, we're going to go biking together. So we're doing I just kind of was like, okay, what did Lynn do for me? We went on walks. We went on biking trips. And so we're just doing that together. And I'm just trying to listen. And I don't think I'll be as good as Lynn was to me, but maybe it'll help her in some way. I look for things that where I can shine bright for somebody else or, you know, honor the people who shine so bright for me. And that brings me a lot of meaning. And I also think I now have my dream job, you know, I work at NASA now. And wait, so I'm thinking of the teacher who chuckled like what, how did that come to be? And what do you do at NASA? I'm working with the James Webb Space Telescope. Right now I'm studying galaxies in the early universe and I'm studying the stardust in galaxies in the early universe with the James Webb Space Telescope. And guess what? They're in or near the Hubble Deep Field. So this is like a perfect full circle moment for me. Some of the galaxies I'm studying are actually in the Hubble Deep Field, but the data comes from the James Webb Space Telescope. So the newer generation of stars form out of the ashes of the old generations of stars. And so I'm actually studying that, that dust, that stardust or that the ashes, if you will, in those early, early galaxies. Yeah, I'm a NASA postdoctoral fellow there. Cool. With a badge? Yeah, with a badge. It's been what, seven years, eight years? Yeah, over eight years. Yeah, and obviously when you talk about it, like, I can hear the distance, like, or the shield or whatever it is that you have to erect to get through your day and your life. Yeah. At first grief is like crushing, I would say, and you're learning to carry it, but it crushes you. And as time goes on, you're able to carry it better. I have less, you know, random tearfulness episodes, but they still happen. Sometimes it'll happen when I'm driving or doing dishes for no apparent reason. Sometimes it'll happen and I'll come home and my house is clean. There's not four piles of dirt on the couch. Yeah. Or, you know, seeing a class of kids that are Woody's age, what he would be now, things like that, I still get tearful about and it can still happen, but I'm just better at carrying it, I guess. Do you have, like, a memorial place, a special spot? Well, Woody was never found, but Jason was found. And that was actually on Valentine's Day of 2017. So Jason was cremated. So for the longest time, I had his ashes in an urn, but I felt like the right thing to do would be to return them to the ocean to be with Woody. Jason really loved rivers and the forest. And so I was able to find this river near the ocean, right by the ocean, so I could hear the waves, but I couldn't see them. And it was just this very peaceful place and I poured his ashes in the river and they flowed out into the ocean near where it happened. Oh my god, what a beautiful way to... Yeah, my childhood best friends were there that day. And afterwards, they said, you know, that that was magical because right as we pulled up and sat down, you couldn't even see anything. It was just all fog. And then suddenly this, like, wind came through and cleared out all the fog and you could see the sun and it was just this very beautiful moment. I mean, you study ashes to ashes, dust to dust. Like, you study that poetic idea. Yeah. Returning to the stars, being made of the stars. And do you think about your evolution as a family? Like, the metals and matter of you? Yeah, I mean, well, like, I'm studying these clouds of gas and dust that are from exploding stars and so eventually we'll be part of the same cloud of gas and dust again and maybe we'll forge inside the same star again. The thing that led me to you actually was a tweet that you put out and it said crying while writing my PhD dissertation about galaxy quenching and then you wrote, which will be dedicated to my late son and late husband. And then you kind of screenshoted the dedication. Can you read that? Yeah. For Woody and Jason Thomas, from the local universe to the first galaxies, the brightest moments in space and time occurred during our brief epoch together. That light is unquenchable. Is it still true for you that the brightest moments in space and time for you were with them? Yeah, definitely. I don't think that will ever change. You know, being Woody's mom, is the best thing I've ever done. Huge thanks to charity for sharing her story with us. There is a beautiful new documentary about charity's journey. Just came out and it's winning all kinds of awards. It's called Space Hope and Charity. To check it out, schedule a screening and learn more. Visit spacehopecharityfilm.com. This episode was produced by Jessica Young, was sound designed by Dylan Keefe, and fact checked by Diane Kelly. Special thanks to Jad Abumrad and Megan Steelestra. Finally, a big special thanks to charity's brother Michael Woodrum, her sister-in-law Gina Vivona, and the singer Claire Riley Rowe, who together wrote charity that song while she was creeping. It's called Sky Full of Ghosts and I listened to it easily a hundred times or so while working on this piece and I wanted to end today by playing it here. Hi, I'm Greta and I'm from Santa Rosa, California. And here are the staff credits. Radio Lab was created by Jad Abumrad and is edited by Soren Wheeler, Lulu Miller and Lotte of Nasser, our alcohol host. Dylan Keefe is our director of sound design. Our staff includes Simon Adler, Jeremy Bloom, Becca Brestler, W. Harry Fortuna, David Gable, Maria Paz Gutierrez, Sindhu Njana Sanambam, Matt Kilti, Annie McEwen, Alex Neeson, Sarah Kari, Sarah Sandbach, Anissa Vica, Ariane Wack, Pat Walters, Molly Webster, Jessica Young, with help from Rebecca Rand, our fact checkers are Diane Kelly, Emily Krieger, Anna Pujol-Mazzini and Natalie Middleton. 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