16 minute read
Galaxies everywhere: Purdue's Danny Milisavljevic hopes Webb telescope's discoveries reveal our connection with the universe
BY KEN THOMPSON
PHOTOS BY CHRISTINE PETKOV AND PROVIDED
Dr. Danny Milisavljevic is a Sherlock Holmes in the field of physics and astronomy.
The Purdue University associate professor is always seeking “motivated and enthusiastic” students to join his team of “supernova sleuths” investigating the catastrophic deaths of massive stars.
“I’m trying to understand the fundamental process that makes life in the universe possible,” the Canada native says.
After earning his undergraduate degree from McMaster University in Hamilton, Ontario, Milisavljevic began his career as a self-described “professional” astrophysicist at Harvard University in 2011. He joined the staff at Purdue in 2017.
Recently featured on the CBS news magazine “60 Minutes,” Milisavljevic was described as “starstruck” by correspondent Scott Pelley from the images obtained by the James Webb Space Telescope. Launched into space on Christmas Day 2021, the James Webb Space Telescope uses high-resolution and high-sensitivity instruments to view objects too old, distant or faint for the Hubble Space Telescope.
The photos sent back to Earth and released to the public this past July were a highlight of Milisavljevic’s lifelong obsession with what lies beyond Earth’s atmosphere. He recently sat down with writer Ken Thompson to discuss the impact of the Webb Space Telescope and how it relates to his research.
Q: For my generation, the race to the moon sparked so much interest. When did you become fascinated by what’s out there beyond Earth?
A: I trace it back to when I was given a project in Grade 2. It was on the solar system. I spent time learning about each planet. This was back in the day when you would go to the library and go to the stacks and get out the encyclopedias. I remember spending time for each planet. I had a title page and I still remember the motion of coloring in each planet. I felt a connection to the planet. Then I wrote a description about each, all the way through to Pluto when it was still a planet.
Over the years, the fascination of what’s out there beyond Earth has stuck with me. It’s always been a part of my life in one way or another.
Q: How did you prepare yourself for your life’s work?
A: I kind of have a meandering path. I always had some association with astronomy clubs growing up. I have a lot of thanks for my high school teachers getting me involved in that. They took me to a local astronomy club, where I got to look through telescopes. When I went to college I continued that interest. I actually got summer research opportunities. One of those geeks led to us finding new moons around Uranus and Neptune. I got to name one of the moons.
Q: What was it?
A: Ferdinand (laughs). I can tell you a whole story behind that. I had a short amount of time to come up with a name. In theory, you can name it anything you want. But the names in this particular orbit around Uranus were named after Shakespearean characters from the play “The Tempest.” So I go to the bookstore. They didn’t have any copies of “The Tempest,” so I go to the library and I got the Cliff’s Notes. I got the BBC stage production, the original one, and when I saw Ferdinand – he’s the prince who falls in love at first sight – when I looked at the etymology of Ferdinand, it means “bold adventurer, ready for travels.” I thought that’s perfect.
After my undergrad, I thought I was going to be a philosopher. So I did a master’s at the London School of Economics in philosophy science. But then, after going to a couple of workshops, I saw a bunch of old people arguing past each other without any constructive movement forward in the field. So then I went to graduate school when I moved to the U.S. at Dartmouth College. A professor took me to a professional observatory (with) a big telescope. I’ll never forget the first time an exposure came out, it was like the first time I looked through a microscope. I remember preparing a slide, it was a bee’s wing. I looked at it and I saw all this detail I hadn’t seen before. It was like the microscope was pointed up at the sky. All this structure and things happening I didn’t know was there. I was hooked. That’s when I knew I wanted to make it a career afterward.
Q: The James Webb Space Telescope has had a phenomenal impact on not just your field of study but so many others. How did you first gain knowledge of what was going on?
A: The design and initial discussions go back decades. I was first kind of brought into the loop around 2015. At that point it had already been delayed but was now a couple years out at that point from launch. There were workshops and talks to go to, to learn about the capabilities. People would get together to talk about projects that would benefit from (the telescope). My own team really started to get together around 2017 after we had a meeting at Princeton University. We spent two years developing a project for Webb. Then there was a delay, then another delay and the project in a sense got more refined, better developed. Our scientific priorities were better understood so that when we submitted it, it was compelling enough that it was selected to be among the first targets for James Webb.
Q: I remember when I first saw pictures sent back by the James Webb Space Telescope, to a lay person like myself, I was amazed. What were you experiencing emotionally and intellectually when you first saw those photographs?
A: It would be a lot of the same as you. Amazed. Delighted that it was working after all this time and money that had been invested. The payoff for everybody involved was enormous. Two memories come to me. One is when I first saw any image. I had no special privilege like other people. I wasn’t part of the James Webb team so I was only getting data as they were feeding it out to the public. One of the first images was a calibration image and that’s just, “Hey, things are working.” It was pointed at a bright star, which would be boring, but in the background there were galaxies everywhere!
In that “60 Minutes” segment, Matt Mountain said it so perfectly. We’re familiar with stars being everywhere in the night sky relative to Earth but amongst the cosmos in the universe there are galaxies everywhere. But because so many of them are faint and far away, emitting in not optical – what we see – but the infrared light toward longer wavelengths needed the capabilities of Webb to be able to see them. Even though we are looking at a bright, boring object the sky around it is vibrant because there are galaxies everywhere. That was stupendous. If I had been given a homework assignment of how many galaxies would you estimate being in the field of view of any Webb image, I could work out a number, but there’s a different kind of satisfaction, a different kind of excitement when it actually happens. Seeing is believing.
The next thing, of course, was when they released the first real images. That was in July. It went to the White House for the first night and then the next day they released a series of images. That was also amazing. This shows the full power of imaging in different wavelengths, putting it together, making not just beautiful images but powerful science you can do. You are really getting a sense this telescope is revolutionary in its ability to study the universe.
My own program, that’s when I went bonkers. Here’s an astronomical object, this exploded star, the remnants of it we call Cassiopeia A, or Cas A for short. I’ve been looking at this for basically 20 years since my Ph.D. thesis, and now I’ve seen it in a whole new way, opening up all these new opportunities of investigation. It really is mind blowing.
Q: I’m assuming you had hopes or expectations of what you would see from the Webb telescope? Were those hopes/expectations met?
A: Exceeded, I would definitely say. With any new facility like this, you can expect the unexpected. That’s what happened for us. There’s a familiar, kind of circular shape to the exploded star debris. In the middle of it, not seen in the optical, hardly noticeable in any previous image or wavelength was this bright emission. We call it ‘The Green Monster’ because when we made it a color image it just jumped out. It had this kind of streak to it and it was scary.
One of the main goals of our program was to see inside the exploded star as well as possible. To make the science as understandable as possible, the gas we see in the optical light is very hot. The shock has excited it. The stuff in the inside, closest to where that original explosion took place – remember what we are looking at was once a star – the debris is expanding in various directions. It gets excited by shocks and gets really hot. What we’re really interested in is what happened right at that location of the star. The gas there is very cool; it hasn’t been excited by the shock. To be sensitive to those very cool gasses you need to look at longer temperatures. It’s very similar to night vision goggles. You can see people at night, it’s not optical light, but you can see their heat signature. But it’s toward longer wavelengths, the infrared. That’s why Webb was able to see it unlike previous telescopes. To answer your question, we expected the unexpected.
I’ll just say one more thing: the sharpness of the images is amazing. Spectacular. Like it’s high definition. It’s hardly comparable to what we were able to do previously at these wavelengths. I remember the first time I got my pair of glasses and the world looked different. You can see colors differently. In some instances, what Webb was showing us … in hindsight once we saw it in Webb you could see something like that in the previous data, even Hubble. But only the benefit of having a sharp image do you know what it was as a result.
Q: Obviously, we’re going to keep learning more as the images come in. But what else have we learned that will be important for further research?
A: Part of what motivates me to do this research is understanding our origins. The universe started with a lot of hydrogen, helium and some other trace elements. But it’s only through massive stars, stars that are even bigger than the sun — 10 times bigger – they go through this evolution that ends with a dramatic explosion that produces all the raw materials needed for life. The oxygen we breathe, calcium in our bones, the iron in our blood, etc. Part of it also is how much stuff each stellar explosion produces, how much is released into the interstellar environment. So our research is being able to better understand that process.
What’s new with Webb? Webb is allowing us to access the physics of what happened closest to the explosion unlike before. There are many efforts using the world’s fastest computers to simulate what an explosion looks like. It’s so complicated that there are many variables, like knobs they can turn, to make things happen. Our observations provide crucial tests. This is the structure you should try to reproduce. They didn’t have that information before. In a sense, our observations are making it possible for scientists to recreate these explosions in computers.
Q: It’s fascinating to hear all of this.
A: It’s fun (laughs)! I really enjoy my work. I think I have one of the best jobs in the universe. I like to think sometimes I’m a reporter for the universe. Sometimes I get to see things other people haven’t seen, and it’s my job as an astronomer to help convey that message. So I’m actually grateful for opportunities like this to help share this for a wider audience.
Q: You are on the campus where men such as Gus Grissom, Neil Armstrong, Eugene Cernan and Jerry Ross laid the groundwork for their careers. Do you feel like you are continuing Purdue’s tradition of discovery?
A: Oh gosh, I wouldn’t put my name up against people like that. It would be nice to think my work is contributing to the overall effort of the next giant leaps. Making breakthrough discoveries of moving into uncharted frontiers and space exploration, that really motivates me in my research.
Q: What are you hoping that we as a society learn about what's out there in the universe?
A: If you go walking in a forest, sometimes there's this Japanese aesthetic called Yugen. If I can paraphrase the meaning, it's that feeling you get when you walk in that forest and you have this kind of awestruck. It's that indescribable feeling of how tremendous the cosmos is. That’s you on Earth. It’s you being in close proximity to this big tree in a huge forest. I hope the work that I do can provide those kinds of experiences on grander scales. Not limited to just walking here on Earth but to be able to visit at least virtually distant worlds. Locations elsewhere in our galaxy or ultimately out into the distant cosmos. To provide enough of the context. A tree is relatable. We see them all the time. We don’t always see them so big or so many of them. The same with these kind of astronomical images. They can be a little bit hard to understand about context but I hope to be able to provide the background information, the scientific setting as it were, to provide them with what’s needed to have this connection with the universe that’s indescribable. That helps us formulate a little bit of meaning for it all.
We are part of a great, vast cosmos. It’s incredible to think we provide a way for the universe to have a consciousness. For a way for the universe to know itself. Otherwise, it’s just a bunch of cold gasses and exploding stars. I hope observations with the James Webb Telescope are a catalyst for people to have these connections.
Q: The topic of UFOs and what does our government know has become a hot topic again. Are we being conceited to think we are the only life in the universe?
A: Conceited is not the word I would use. If you ask me to put money on it, I would stake a non-negligible amount favoring somewhere in the universe there’s going to be life. The thing is, I’m sure nobody would be able to cash in on that bet. I don’t know how soon it’s going to be that we’ll find life. Given that we have so much rich life on this one planet, among all the stars in their own galaxies, among all the galaxies in the universe it seems like life should be able to pop up somewhere else. But intelligent life seems to be very hard, not impossible but very hard. Given the rarity and the vast distances of the universe it’s unlikely where we’re going to have “Star Trek,” where we’re communicating with it.
I read a biography of Carl Sagan, who was very interested in this question. He had such a sadness when they first pointed the radio telescope looking for great communications from intelligent beings in the nearest galaxy, the Andromeda Galaxy. Nothing. There’s a whole other galaxy with all these stars and no clear signs of intelligent life. It will be very hard to be able to do so.
Q: What do you like about being at Purdue and living in Greater Lafayette?
A: I love it here! It’s been so good to me. I moved here from Harvard University. Here at Purdue I’ve had much more of a sense of community amongst the entire campus. I’ve had much more of a sense of community from Greater Lafayette. The day we moved in, our neighbors came by to say hello, introduced themselves. We ended up doing more things here than we ever did in the Boston area because we don’t have to worry about traffic. The cost of living is much lower. My wife, who moved her business here, has also felt the same way. The small business community here is very tight, very supportive. A new business opens up and all the other small businesses go to support and purchase from each other. There was that real feeling of community here on campus and in the Greater Lafayette area that immediately reverberated with me.
Purdue just has been very good about enabling research for me. They’ve provided opportunities to build up my research portfolio, provided me computing access. This whole other side thing I do with virtual reality, to recreate the stellar debris fields in three-dimensional reconstructions that you put on a headset. We can take virtual trips. All this, there’s no other institution that can reproduce this.
Q: You mentioned your wife’s wildly popular business French Knot, which sells wool apparel and gift items. What do you do for relaxation?
A: Number one is our dog, Wilbur. I spend a lot of time with him, taking him for walks. We’ll go explore certain places, go for hikes. I like reading. I like collecting old books. Sorry to say I’m boring, but a lot of them are older astronomy text books. Von’s is a great bookstore. The basement of Von’s is the best! Whether it’s a hobby or a necessity of life, projects around the house. We like repurposing furniture. My wife likes antiques, so sometimes they need a little work. ★
