Sylvia Ekström
Stars are our mothers
This morning we are with Sylvia Ekström who is an astrophysicist at the Observatory of Geneva. She studies the way massive stars evolve over time. She is also very involved in outreach at the Observatory of Geneva and in the entire region. She will tell us about stars and her atypical career.
Tell us, when and how did you start to be interested in astrophysics?
Well actually, I was attracted to astrophysics very late. I wasn’t into science at all when I was young. For me, it was all too Cartesian and I was rather the literary type. I did the equivalent of the baccalaureate in Greek and Latin, so really far removed from science : I hated physics. I discovered astrophysics much later, long after I started working, since I really discovered astronomy, astrophysics, the joys of this science when I was 33 years old.
If I understand well, your career was not at all linear. What were you doing before started to be interested in astrophysics?
In a way, my career isn’t linear, but at the same time it is very linear. I feel like I followed a single guideline which was the search for our origins : understanding who we are, where we come from, why we are the way we are. With Greek and Latin, I was interested in the origin of our civilization, our greco-latin culture. Then I got interested in our arrival on Earth, so I became a midwife, which was just another way of exploring our origins. Later, I discovered astronomy and I realized that I could study the very possibility of our existence in a much broader way. And that was so awesome, I absolutely needed to know more.
I started out casually. I was a midwife so I just went to conferences. I could read books, look a bit into what other people could tell me. But there always is a point where you’re told “That’s because of the laws of physics”, and the explanation stops because it’s too complicated. You need mathematical equations to understand what comes next. And that was much too frustrating! You can’t tell me stuff like that, it makes me mad! So I said to myself “Well, let’s go see what those equations have to say, let’s delve into this”. So I went on to deepen my understanding. I started first year University classes in physics.
You have a rather inquiring mind. A bunch of my friends are starting to have kids, so I wanted to ask: When you were young, what did your relatives and the other people around you do to stimulate your curiosity and your creativity?
I had the massive opportunity of going to a private school that let us discover things on our own. We had a certain number of things to do in math, French, dictations,… But we could organize our time as we pleased over the course of the week. And we could dedicate the remaining time to trying to discover stuff. Teachers were there to help us dig deeper on the questions we might have. Doing that was just fantastic.
There was a bit of everything. Some students didn’t do squat until the last minute of the last hour, and did all of their French and math exercise sheets on Friday afternoon just before the deadline. And there were people like me who would rather get rid of the exercise sheets on Monday morning, and then spend the rest of the week trying to write things, or finding answers to questions, or doing visits, meeting people. And it was awesome, really awesome.
You specialize in stars. Can you tell us a bit more about your research topic?
Stars. They’re our moms in a way, since they created all the elements we are made of. The carbon, the oxygen, the nitrogen… it all comes from stars. These really are the main elements we are made of and they all were created in the heart of a star. So its a topic that is fascinating to me, just because of that.
A star is essentially a ball of hot gas. That is the simplest definition you can give of a star. Then if you want to be a bit more complex : it is in hydrostatic equilibrium, between its gravitation which tends to pull the matter in, and the motion of the gas, its pressure which tends to make it expand. Stars spends 95% of their lives in this stable hydrostatic equilibrium. Then there are these small phases when the star changes state. All of a sudden, there’s no more hydrostatic equilibrium at all, the core collapses, heats up even more, moves on to a different type of fusion. Or sometimes, it’s the envelope of the star that suddenly expands to become a red super-giant.
By studying the physics of stars, we try to understand:
- Why does a star go from a stable to an unstable state?
- How are chemical elements produced in stellar cores?
- What physical processes could we imagine that would change the way these elements are created?
Here in Geneva, we are specialized in internal mixing processes. More specifically those that are induced by the rotation of the star. As the star spins on itself, different layers of the star are going mix in a way that puts in contact zones that normally don’t touch each other. This slightly modifies the chemistry going on in the star, the way that elements can be produced, the type of elements that are produced and their relative abundances.
In practice, what kind of data do you look at? What type of instrument do you use to collect this data?
So what I do is really numerical data, meaning that I digitize a star. I have a computer program that simulates a star. In this program, we entered all the physics we know of: gravity of course, and nuclear reactions, state equations, the way gas behaves, thermodynamics,… All sorts of physical laws, and also the effect of rotation. Next we create a star and make it evolve. Then we look at what’s happening in its different layers. We try to generate things that are similar to what could be observed in the sky. After that, we compare our models with what can actually be observed and we try to figure out if it fits. If it fits, we’re happy. And if it doesn’t fit, we’re happy too because that means we still have work to do! [Laughs.]
So you’re the mother of numerical stars
Yes, exactly. So my tool, my instrument is simply my computer.
What’s your favorite part of your job?
Its diversity. The freedom that we have. In fact, the academic world is great because nobody imposes a research topic on me. Of course, we have a certain framework here where we basically study mixing effects. But the type of stars that I am going to look at, or the way that I am going to approach this theme is completely free. Often, we get ideas from conferences where we met people. We heard other people talk about their own research, about some problems they might encounter, or some weird star they observed, and we think “hey, I’m going to take a look at what our own models do. Can we improve things and understand why things don’t click with standard models?". Se we are completely free to explore. That’s the heart of fundamental research: exploring for the sake of exploring.
You also do a lot of outreach, and you are the coauthor of a book called We won’t live on Mars, or anywhere else1. Broadly speaking, it explains why it is unrealistic to imagine that we might be able to live on other planets than Earth. How long did it take to write this book?
I’m going to be very honest, I didn’t write it. What I mean is that we worked on it together, but my husband is the one who actually penned the book. I never would have written it, I don’t have that capacity! [Laughs.] Well, I don’t think I do.
So yeah, it was really a two-person operation, and he wrote the book in a few months. It went really fast. We had this book in us, from our long discussions, all the feedback I get… I do a lot of visits for the Observatory, so I hear people’s questions. And there really is this feeling that “Yeah, Mars is easy. We went to the Moon, Mars is just a bit further out, but that’s OK. It’s basically the same thing”. But it really isn’t the same thing at all. The fact that the distance is so much bigger makes the entire expedition completely different. From talking about these things over and over, we had this book in us. We just needed the opportunity to lay it out on paper, and it went really fast: in under six months, it was done.
As you were researching this book, what did you learn that surprised you the most?
I would say that what really hit me in everything I saw was: we’re not really missing any technical aspects, but rather the physiological, biological, human aspects. The problem is that our bodies aren’t made for stepping out of our bubble. And as soon as we step out of our bubble, we have to create other survival bubbles elsewhere: a spaceship, a spacesuit are small bubbles. If we want to survive for a longer period of time, we need a bigger bubble and the technology becomes very complicated.
Our organisms are so fragile. They were conditioned by our terrestrial evolution to such an extent that they need a certain gravitation, a certain pressure, a certain kind of atmosphere to breathe,… in order to thrive. And as soon as we step out of these conditions, as soon as we go into weightlessness, everything goes haywire. Sometimes its hard to understand because when you look at the astronauts in the ISS, they look like they’re having so much fun, being silly without any gravity. But in fact, they are in a sorry state. Their bodies ache. Thomas Pesquet explained this well, by the way, in La tête au carré2 where he was invited just before going back to the ISS. They are in pain, their bodies ache.
And when you study their physiology in space, you realize that their bones deteriorate, their muscles deteriorate, the entire vascular system is disrupted. There is no up or down, and the entire body is pumping to make fluids go up, so there is an excess in the upper part of the body which leads to brain disorders, vision impairments,… So we aren’t fit for weightlessness, really not. And if we don’t have good systems to compensate this during long trips, it can be detrimental upon arrival. So I think that one of the main things that needs to be developed is a system where we create some artificial gravity during the trip. Otherwise, we’ll have people who are completely beaten up when they arrive on Mars.
What comes to mind is the image of these astronauts who have to be carried out of their capsule when they return to Earth because they can’t walk anymore
Exactly. Some of them are vomiting. They really are in a pitiful state and they need several days to get back onto their feet. And for some functions, they need several months before getting it back. You have to imagine that when they get back from the ISS, they have finished their mission, so they can rest, pamper themselves, try to get back on their feet. On Mars, their mission starts as soon as they get there. So they have to do the hardest part of their mission – installing everything they need to survive, install their dwellings and all the survival systems – when they are at their worst. So in my opinion, it really is a big challenge, and that’s what hit me: how the limiting factor really is humans.
Slight change of topic: What is your favorite celestial object and why?
I think it’s Betelgeuse. It’s a red super-giant in the constellation of Orion that winks at us in the winter. It a splendid star and we know that it is in the final phases of its life, since it’s already a red super-giant. Given its mass, it will probably end like a red super-giant. We don’t know if it will explode next year, in ten years or in a thousand years, but it might be a supernova visible to the unaided eye. And I hope so very much that this supernova will explode before I die!
Oh yeah, I remember hearing a lot about Betelgeuse last year. Some people thought that it was about to explode because its light had suddenly dimmed.
Exactly. We had so much hope, but no. It just emitted a lot of dust in our direction. It was just an unusual mass loss, unfortunately.
If you had a million Swiss francs to finance astronomical research, how would you spend it?
That’s a good question. [Pause.]
Well I think that I would finance a few positions for people who are just left alone, who have no publication requirements. We really give them time to work undisturbed, trouble-free. I think that the pressure we have to always publish to exist… It’s a good thing because that’s how you get known, but… Typically, if we want to make any progress in cosmology, we really need to find a new kind of physics, some new mathematical formalism. And to do that, we need time. And during that time, we can’t be publishing, because we’re just focusing on building stuff up.
When we try to understand how a star works, among other things, we develop models. Small models like those I’m working on, but we also need gigantic 3D models that can’t model the entire life of a star, but only a small fraction. It takes a lot of time to do this well, and you can’t publish anything while you’re still working on it. And for a lot of issues, if we want to make any real progress, we need to be left alone. And as of today, research isn’t going in that direction. So a million wouldn’t be enough, but it would be something. A few positions could be opened.
One last question: you may have started answering this question at the beginning, but what do you think the knowledge of astrophysics give us as humans, and what does it bring to our civilization?
First of all, I think that astronomy, the stars are something that has always inspired us. It has inspired musicians, poets, all kinds of artists. It’s something that piques our interest. We can’t stay insensitive to a starry night. And when we start to understand how it all works, we realize that it explains who we are and where we come from on one hand, and it can also show the frailness and the uniqueness of our Earth.
In the Solar System, there are no habitable planets other than Earth. So there is no readily accessible Planet B. So some people say “Sure, but we are discovering so many exoplanets, one of them is bound to be habitable”. What you have to realize is that it takes time to get there. Space is really really really really big. When we go to the Moon, it takes three days. When we go to Mars, it takes 9 months.
Imagine we want to go to the star nearest to the Sun. It’s 4.2 light-years away. You might think “OK, well 4.2 light-years can be a 40 year trip if we reach 10% of the speed of light”. But reaching 10% of the speed of light requires an enormous amount of energy! And it requires a very progressive acceleration, because obviously we can’t reach 10% of the speed of light in the blink of an eye: that would completely destroy us. So what that means is that we will never actually travel at 10% of the speed of light. We’ll travel much slower because first, we’ll accelerate, then we’ll decelerate to avoid crashing into the next planet.
Take the fastest probe we have today in the Solar System. That’s Voyager 1. It really is the fastest. It would take 75,000 years to reach the closest star. So when we’re talking about 4.2 light-years, you have to realize that a light-year is really really big. And that’s the closest star to the Sun, where as far as we can tell, there aren’t any habitable planets. So if we want to go to a habitable planet somewhere else, that might mean a 200,000 300,000 or 500,000 year trip. And that’s not just a capsule with a few people in it. It would have to be a generational ship. And for that to work, you need an autonomous system. And we saw that Biosphere 2 collapsed because of a detail. There are small subtle things that make it possible for a biosphere to be in equilibrium or not.
Can you explain in a few words the concept behind Biosphere 2?
Biosphere 2 was an experiment to create a second biosphere, with Biosphere 1 being the Earth. They were trying to make a kind of bubble on Earth that would contain a self-sufficient system in equilibrium. Plants would produce oxygen, people could eat the plants… and everything would be in balance. And that doesn’t work because a biosphere is extremely subtle. It the tiniest element is amiss, everything collapses. And that’s another thing we don’t realize when we talk about living on another planet: we aren’t alone. We are just a tiny part in a vast chain of life, and we need the slightest bacteria. Every worm in the soil is important for us and for the biosphere. And if we neglect any element, the result is not at all in balance.
That’s why I really like the book Aurora by Kim Stanley Robinson. He’s the author who wrote Red Mars, Blue Mars and Green Mars, so he’s known for the colonization of Mars. Well in his latest book, he mentions that Mars is still not autonomous and still relies on shipments from the Earth. He tells the story of a generational ship that takes off towards some star, maybe Epsilon Eridani, and everything goes wrong. They turn around because it doesn’t work. And I find it fascinating that the man who convinced so many people that colonizing Mars was possible, even he came back from that idea.
Thank you for having played along, it was great talking with you!
Thank you.
Interview carried out on July 15, 2021 at the Astronomical Observatory of the University of Geneva.
This interview was carried out in French and translated to English. You can find the original text of the interview at this link.
