The Hans Sigrist Foundation

Prof. Dr. Ignas Snellen, Leiden University, The Netherlands

An Interview with the 2019 Hans Sigrist Prize Winner

Hans Sigrist Foundation:   Were you surprised to find out that you had been selected as the 2019 Hans Sigrist Prize winner?

Snellen:   Absolutely, yes!  It was a big shock when I got the call that I had won the prize.  It is such great news and a great honor. 

Hans Sigrist Foundation:  Originally, if you look back to the beginning of your study career, what sparked your interest in this field?

Snellen: For my Ph.D., I studied a very different field.  I worked on galaxies, the very large structures within the universe.  After my Ph.D., I did my post-doc in Cambridge, then I moved to Edinburgh, and I was a little bit stuck in my research, not knowing what to study next. I was not even sure whether I wanted to go on with science at that time.  Then, out of the blue, I was asked to organize a workshop on this field, on extra-solar planets, and when I learned about the fantastic things that people were doing, and I felt like this was what I needed to do.  I left my old field behind, and I started something new.  This was around 2000, so about two decades ago already.

Hans Sigrist Foundation:  So, this was when you were doing post doc research? 

Snellen: Yes, when I was a post doc lecturer in Edinburgh.

Hans Sigrist Foundation: What got you interested in this general field as a whole when you were trying to decide what to study during your university years?

Snellen:  As a little kid, I loved this field already.  I had my own telescope in my garden when I was eight.  This is something I wanted to do my whole life.  Of course, later, I had to figure out whether I could do it, because you have to be good in math and physics, etc. 

Hans Sigrist Stiftung:  If we ask you to explain the type of work you do for people who are reading this who are not in the field, could you explain that to us?

Snellen: Yes, the main goal is finding other Earths and seeing whether they may have life.  The idea is that if you think about the universe, we have our sun, and we have the planets around our sun, and the Earth is one of the planets.  Only for the last approximately 20-25 years have we known that other suns also have planets.  First, we only found the big planets, the gas giants, like say, Jupiter-like planets, but now we are honing in on smaller and smaller planets and they are, in many ways, possibly like Earth.  The actual research that I am involved in now is not so much finding those planets but finding out what these planets are actually like, what their atmosphere is, what kind of climate they have, and what kind of gases are present.

Hans Sigrist Foundation:  If you look forward, what do you think the greatest challenges in your research field are? In other words, what still needs to be learned? 

Snellen:  What we can demonstrate so far is that we can learn about the large planets, like Jupiter.  Jupiter is ten times larger than the Earth.  The challenge is to apply all the methods that we have learned to use over the last decade to study larger planets to the smaller planets.  For that, we need new instruments, and we need bigger telescopes.  The challenge for the coming decade is to see whether that will really work.  There are two particular telescopes that are of great interest: the James Webb Space Telescope, which will hopefully be launched about one and a half years from now.  Particularly interesting for my area of research is the Extremely Large Telescope - that is the actual name.  It is a telescope being built now in the north of Chile.  It will have an enormous 39-meter mirror.  That telescope will hopefully be operational in the middle of this decade. The challenge will be to optimally use these new telescopes and to use them for targeting Earth-like planets.

Hans Sigrist Foundation:  What do you think the prize funds will be able to do for you in terms of the research that you are doing?  Are there things that you are already hoping to accomplish with which it will help you?  

Snellen:   Yes, in my group, we are always thinking about new instruments and new ways of actually observing.  I have some ideas on how to use this prize money regarding how to observe.  It would be seed money to try things and buy a few things to test to see how well such a new instrument may work.  For building an instrument itself, we are talking about millions of Euros, so this expenditure will be smaller but will allow us to do early phase research.  It is nice to have this kind of seed money without having to apply for grants.

Hans Sigrist Foundation:  Are there certain areas of research in your field for which it is hard to get funding? 

Snellen:  Well, in the exoplanets, we are blessed, to some extent, that it is relatively easy to get funding.  However, in particular, in this early phase of a project, where ideas are still not polished and you have not proven that it will work, that is the phase where it is the most difficult to get funding.  It is very nice to have this prize to help with this early phase research. 

Hans Sigrist Foundation:  That is our aim, to give the prize and its funds to prize winners at a time in their careers where they can still use it.  So, it is not just a congratulatory award, but instead, another boost to create new work.  What type of work are you and your team working on now? 

Snellen:  What we have done so far is to identify gases in atmospheres, in other words, what type of molecules are present, for example, water vapor or carbon monoxide.  The next step, and that is something we are trying to do now, is to identify isotopes of these molecules, and that is the sort of fingerprint of those molecules.  That is where you have a molecule, a group of atoms which is in one unit.  These atoms have different types, depending on the number of neutrons in the nucleus, and the different types are called isotopes.  The spectroscopic fingerprint for each of these isotopes is slightly different, so in principle, you can measure that, and it is interesting to look at these isotope ratios, so for a certain gas, what is the ratio for one type of isotope or the other.  That can tell you something about the chemical processes or the evolution of the planet over time.  This is something we are working on now, and hopefully, in the next few years, we will get results on that. 

Hans Sigrist Foundation:  How does one actually identify the isotypes from so far away? Is it observational? 

Snellen:  Yes, the information that we get from a planet is pure spectra, so we see how much light we get from the planet, which is a function of the color of the light.  When you have an atom or a molecule, they absorb the light at very exact wavelengths, in other words, colors.  We can identify which molecules are present that way.  It is like a fingerprint.

Hans Sigrist Foundation:   So, by capturing photos of the planet, you can tell which molecules are present?   

Snellen:  Yes, in principle, from the color of the light, even here in the room, you can actually identify what the gas inside the lightbulb is, for example.  It tells you about the chemical substance within the lamp.  Sodium lamps, for example, glow yellow.  So, if you just look at color, that is very rough, but we look at the wavelength very, very accurately.  You can then actually identify the different molecules and even see different isotopes. The wavelength is like a bar code, if your data is good enough, the bar code for different isotopes is unique. 

Hans Sigrist Foundation:   So, are scientists in your field searching for a planet that looks like it could support carbon-based life?

Snellen:  This is a more difficult question - how would you see that there is life on a planet?  Again, we can only measure gases.  What we see from Earth is that life on Earth here changes substances that we have in our own atmosphere.  So, molecular oxygen is only here because of the plant life, so if there were no life on Earth, there would be no oxygen.  So, we hope when we would study planets like the Earth and we would identify oxygen on such a planet, that would mean that there is actually life that is making this oxygen.  Otherwise, one would not expect oxygen there.  This is one example, because there are different ways of making oxygen.  So, we have to learn a lot more about the planets, measure other gases, and understand the history of the planets, to really answer the question of whether oxygen on one planet is probably because of life, while oxygen on another planet may be there due to another chemical process.  That will be difficult, but the first goal is to be able to measure oxygen, because at least then, we can start asking the question of whether the oxygen is due to life or not. 

Hans Sigrist Foundation:  Has oxygen been found?

Snellen:  No, Earth-like planets are still difficult to observe, so we have not been able to do that with the current instrumentation.  We have to wait for the Extremely Large Telescope (ELT), so that will be another seven years or so from now.  However, in principle, with such a telescope, we will be able to see it, on some of the easiest stars to observe.  The other question is how common is life?  If it is very rare, then maybe oxygen will only be present on a very distant star somewhere, and then it will be very difficult to find. 

Hans Sigrist Foundation: It seems like an exciting time, when you know that these new tools are going to be available.

Snellen: Yes, it is very exciting.  A lot of what is happening in our field is because the instruments are really getting better and driving the field.  It takes a long time for these instruments to be built, and therefore, we can already know what we will be able to do a decade from now when those instruments are ready.  

Hans Sigrist Foundation: Are you collaborating on any project at the moment with the Center for Space and Habitability (CSH) here at the University of Bern?

Snellen:  Not directly.  There has been exchange in the sense that people who have worked here sometimes come to Leiden, or the other way around.

Hans Sigrist Foundation:  Having spent a few days here now, can I ask you what your impressions are of the University of Bern and the CSH?

Snellen:  Well, I am very jealous of the CSH, because it has scientists from different disciplines working in this field together. In science, it is difficult at many other universities, because at many universities, all the science is done in little boxes, and there is not much interaction between the boxes.  At those schools, there is, for example, an astronomy box, there is a physics box, a biology box, a chemistry box, but for this quest that we have, searching for life, you need to bring all these disciplines into one room, because they all have input.  We all need that to be able to go forward and to be able to identify these bio-marker gases that may identify life.  So, you need to have these centers where you bring all the different disciplines under one roof, and that is what is happening at the University of Bern's CSH.  We are trying to set this up in Holland as well.  It is difficult - we have a virtual institute now, but this will still be a long road.  At Uni Bern’s CSH, it is already happening and shows how effective that approach can be. 

Hans Sigrist Foundation:  Do you have advice for young people who are interested in this field, both at the secondary school and early university level, if they want to work in your field?

Snellen:  I often give advice at open-house days for students who are choosing their university major, and I say that you should follow your heart.  Follow the course that you think is most interesting.  Do not let yourself be too influenced by those around you who are worried about what kind of job you may get later.  In the sciences, even if you do not become an academic scientist, you will still find a job.  For example, at Leiden, we have 100 Master's students in Astrophysics alone, and they get jobs everywhere in the industry.  There is no reason not to choose a field like this.