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Interview with Dane Späth

  • Could you please introduce yourself?

My name is Dane Späth, I am a PhD student at the Landessternwarte in Heidelberg. I also studied there, but I was born in Ulm.

  • What was your scientific career?

I originally studied physics in Heidelberg. That had always been the thing that inspired me, even in school, but always with a view of going into astronomy. That always interested me most, for example as a child in the planetarium. So I studied physics, but already during my bachelor thesis I got in contact with the exoplanet field, at the Heidelberg observatory. There, I luckily could also do a cool master project, working at a telescope. And after a short break, where I spent a year working, I came back to research. I simply had fun working scientifically and was keen on getting my teeth into exoplanets.

  • What is your research topic?

I am looking for planets around giant stars. Those are very old, evolved stars. Our Sun, for example, is currently in a long-lasting state where it burns hydrogen to helium in its core. After a certain time, in about 5 billion years, the Sun will begin to expand and at some point will start to further burn Helium. So, my goal is to find planets around stars like that. We already know a few of those, but we want to understand how those planetary systems that still exist in that stadium, are influenced by the star’s evolution. That’s the general aim of our research.

  • Which methods do you use?

I have several projects in that area. One is a mix of transit method and radial velocity, looking through TESS-data. That’s a transit satellite observing a big sample of planets at the same time and looking for periodic changes in their brightness, which might be caused by planets. Then, we look for promising candidates, giant stars of course, and follow up on them with radial velocity. There, we look for a shift in the lines in their spectra and that can be used to determine the planet’s mass, while the transit method gives its radius. The same method I use for another project, where we actually work with a telescope at our observatory ourselves, and I am even a little bit involved in the instrumentation. On the other hand, I also use computer models to interpret the measurements we have. So this is a very varied field of work, I would say.

  • Why did you choose this subject?

In principle, I simply find planets exciting. I find super-cool what started at the beginning of my life, the search for exoplanets, and how much we have learned in recent years. That I specifically look for planets around giant stars I find especially exciting, because it tells us a lot about our Solar System. We want to understand: What happens to our planets when the Sun evolves further? That may be a long way off, but the only way to learn about it, apart from simulations, is to understand how systems look around that kind of star. To me, that’s why it is also connected to us. But I have to say, I just find it exciting to find planets under all kinds of varied conditions and around all kinds of stars. You cannot just focus on one small corner and always say “Earth-like planets around Sun-like stars”, you certainly get to search a bit further afield and try to find different things.

  • Where do you see connections between your topic and other fields of research?

We collaborate a lot with modeling, for example dynamic modeling of what happens when a star evolves. In this way, we, looking for planets around a certain kind of star, are quite dependent on people calculating models and simulating the hydrodynamics in the star itself. On the other hand, we depend on scientists designing dynamic orbital models: What happens to a planet close to its star, when that star expands? We have many intersections there. Apart from that, we are in an area, where we do not know much about our planets yet. That’s because of the stars we are studying, they do not want to reveal what’s in them. In this sense we are not yet far enough to work together with geological models. The data doesn’t allow that yet.

  • Are you connected to other SPP projects?

At the moment I don’t have much there. In principle, I think we are a rather small field in the planet community, because we observe a certain kind of star. At the moment, the SPP is more focused on understanding single planets. How can we model that? How does the planet form? et cetera. Just due to the fact our stars do not as easily reveal their properties, we are not quite as good at connecting to those fields. But I hope we will get there in a few years.

  • What SPP offers did you make use of?

Last year and this year, there was a SPP conference each, and those were very exciting events, because you got to look up a bit and see other fields, and you have real experts sitting there, who work in these fields. It is always extremely exciting to get a look at what they do. That may not always be super applicable to your own research, but it is still great to broaden one’s own understanding of this quite complex subject matter. Apart from that, I have of course also visited the SPP webinar regularly, because there are also quite some interesting talks. And of course I occasionally worked with the outreach team, and that is also thrilling to see what we do there to bring the science to the public. For me as still a young student it is very exciting to see what possibilities exist there, and to learn from the experts.

  • Could the SPP support your research?

First of all, to even have the possibility to do this research, that’s great on its own. And then the network you get, where you can ask experts if you have questions about certain subjects. Add to that the possibility to go to these conferences and learn a lot there. Even if you don’t need it for your research directly, this, for me, is another reason to do my PhD, because I have the chance to learn these things. And of course you get to know a lot of nice people, that’s very fun and is highly motivating, to make cool contacts.

  • What might we know about your topic in 10 years?

That is of course always the most difficult question. I hope that through new methods, or through improving methods we already have, I should say, we can improve our picture, and also that we find a lot more planets. Right now, we know only about 140 planets around giant stars; compared to almost 5000 planets around main-sequence stars, this is quite a small sample. We need a lot more to determine parameters statistically, to understand, which parameters influence what, we are still lacking there. I definitely believe that ever-improving telescopes with super-high resolution spectrographs, like Gaia or Espresso for example, will help us to find much, much more and therefore advance the statistical analysis. I think, this will allow us to predict what happens to certain systems when we know the star evolves in a certain way. Which planets will survive? Which might be swallowed? Which stay, where they are? That would be, I think, something to hope for in 10 years.

  • What are your hobbies outside science?

Actually, I play handball in a club, including regular tournaments and such things; that is fun and also a good balance. In general, I like to do sports, I also like to go swimming. And during the Corona break, where a lot was impossible to do, I got the idea to learn the piano and so I bought an e-piano and started teaching it to myself. I am quite satisfied, I would say; of course there’s room for improvement, but that is also a lot of fun for me.

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