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Originally published in Elhuyar Aldizkar on 1/06/2025: magazine page (in Basque)
Author: Ana Galarraga Aiestaran
Photo: Jorge Sanz (CAB CSIC-INTA)
Itziar Aretxaga
“It’s wonderful to be able to predict the eclipse”
The solar eclipse was the reason to interview astrophysicist Itziar Aretxaga (Bilbo, 1965). Aside from the eclipse, however, she has something to tell. In fact, since a few months ago, she has been researching at the Astrobiology Center of CSIC-INTA (Madrid), after working in Mexico for almost three decades. Her research topic is the giant births of stars that take place in distant galaxies, and she has mainly been talking about them, but she has not hidden that she is very excited to see the eclipse of our nearest star.
Are you planning to see a total solar eclipse? Have you chosen a place?
Yes, I’m excited! I am actually arranging my calendar so that I can see the total solar eclipse. Just before that, I’m coming back from a conference, and then I have to go to another one. But in the meantime, that week, I’ll be sticking around to watch the eclipse.
I saw a total solar eclipse for the first time two years ago. I crossed Mexico to reach Texas and see the total eclipse there. I had seen partial eclipses before, but this was the first time I travelled to see the whole thing.
I think it’s wonderful to be able to predict that this will happen. It’s truly amazing to think that they even had this wisdom thousands of years ago, and how now we can accurately predict with physical models how the eclipse will occur, and plan when and where to travel to see it. That to me is really wonderful, an indicator of the progress of science.
The Sun is our closest star and the one we know best. You, however, study the ones that are farthest from us, the ones that are being born.
Yes, that is my research topic, the birth of galaxies: how stars are born inside galaxies and what conditions must exist for this to happen.
For this, you have spent many years in Mexico. Can you tell us how you got there and what you’ve been up to?
Well, look, I’ve been in Mexico for 27 years! I started studying Physics at EHU; then I went to Madrid, first to Complutense University, to finish my BSc, and then to the Autonomous University; I did my doctorate there. From Madrid to Cambridge, to the Royal Greenwich Observatory, and from there to Germany, to the Max Planck Institute. And finally to Mexico; I have lived there for 27 years, almost until now.
What I’m researching now is something I’ve always researched: the evolution of galaxies. In this evolution, many processes take place. One of them is the birth of stars, and my research has always been related to the birth of stars.
At the beginning, when I did my thesis, I was mainly concerned with the stars that are born in active nuclei in our nearest galaxies. Now, however, I am researching how giant star births occur in galaxies far, far away.
In the meantime, some telescopes have disappeared, and you have new ones today. How do these changes affect research?
Yes, yes, we have new ones, and some of the old ones are still running. Now I mainly observe these giant births in millimeter waves. But we put together all the available information, going from ultraviolet waves to radio waves. In fact, different processes are seen at each wavelength.
Some of these telescopes are very new; for example, the Large Millimeter Telescope in Mexico and the JWST [James Webb Space Telescope] in space. But there are telescopes that are not that new; such as VLA [Very Large Array]. Located in Socorro, United States, it is an array of radio telescopes; that is, it is not a single antenna, but a set of antennas, with a certain configuration, to be able to perform interferometry. Thanks to this, we get a very detailed images of astronomical objects.
“We put more than one telescope to work, to work on a scientific goal”
Then we must not imagine you working with only one telescope, but with many.
That’s right. We use more than one telescope to work on a scientific objective, and all this information is necessary.
At first I used other telescopes; some of them are no longer in operation, they are retired. My first telescope was the JKT [Jacobus Kapteyn optical telescope] in the Canary Islands. I made my first observations with it. They were not for my thesis, but for a colleague’s thesis. We were both doing our PhDs, but he was ahead of me, and I went with him to make the first observations, to learn.
It seemed to me a huge telescope, very very large. It was not the largest in the Canary Islands; it`s mirror was only one meter in diameter, and the William Herschel telescope [optical and infrared], which was four meters, was also there in the Canary Islands. But, at that time, JKT made a big impression on me. Now, when I go to 10 meter optical telescopes, I remember that. Everything has become small now.
As with telescopes, as technology changed, so would the way work was done.
As with telescopes, as technology changes, so is the way we work.
Now we take data from one telescope or from another one with much greater ease. On the Internet, everything is connected. There are very large databases, in which we have a lot of information, and we can immediately connect to access the data.
The world itself is much more connected. Every day, we spend several hours on teleconferences, working with colleagues. For example, I do teleconferences with the United States, Mexico, etc. The schedules are different, but this is how we do it. It’s easier to make progress on the internet, that’s for sure.
So yes, the way of working has changed a lot. Now, we go to telescopes less and less. They are more robotic, and observations are made from a distance.
“I’m studying how giant star births affect the formation of galaxies”
The information received by the telescopes is open, is all the data available to everyone?
Not completely. At large telescopes, the team that proposed the research usually has a year to mine the data and see what they can get out of it. But then that data goes into the databases, and everyone can analyze it. But that’s how big telescopes work.
Then there are other telescopes that are private, in which you have to be a part of the mission or experiment to be able to see that data.
So, in general, there are two modalities: having the information for a year and then going to the databases, or the modality of experiments, in which the data is not public, but belongs to the experiment. And if you want that data, you have to make a contribution to participate; you have to put up money to get that telescope experiment going.
For example, at the highest energies, gamma rays, this is how they work. They are not the telescopes we imagine, which focus in one direction. They are panoramic telescopes, they see the whole sky at the same time. It is another way of analyzing space.
What kind of work do you do?
My approach to astrophysics is based on observations. The ability to use telescopes is very important to me. There are some telescopes in Mexico that can be used for such observations; for example, the Large Millimeter Telescope [LMT] is the largest. In addition, Mexico has a part of the Large Telescope of the Canary Islands [GTC, optical and near-infrared]. So I have also used it for my research.
And then there’s another gamma-ray telescope called HAWC. But it is used as an experiment, and you have to be a part of the collaboration to use that data. I have had colleagues working there, and that is also very interesting. However, we specialize, we cannot do everything at once.
So I had those telescopes to work with. Now, I have been here [in Madrid] since 2025, and even if I continue with them, I also have the power to use others.
How did you take the step?
The Spanish Ministry of Science, Innovation and Universities has a program, ATRAE, to attract scientists who work abroad and already have a consolidated career. I think they made the third call this year. Mine was second. I asked to come to CSIC, and I came in September.
I am doing follow-up work. I was working there with the Large Millimeter Telescope, and now, using my work there to take surveys of galaxies at great distances, I am studying how giant star births affect galaxy formation.
“They are very enthusiastic about it, and I really like working with young people”
It can be seen that you enjoy working with students; You have also done a lot of work with young people in Mexico.
Here, I’m building my team, and for example, I have a PhD student who is already becoming an expert, and I’ll have another post-doc.
After all, they are collaborators. You have to guide them a lot in the beginning, because they don’t have the track record you have, to know where things can go. But they are very enthusiastic about any kind of research, and I really like working with young people. They take something from you, but you also take from them. Illusion, above all, and seeing things differently. Working with new generations is wonderful.
And from the scientific point of view, what discovery excited you the most?
Always the last ones. The latest research I have done has always excited me the most. Some things come easier than others, but nothing is easy. You always have to work to get results, you always suffer a little. And you always take the final result with renewed enthusiasm.
To reach these results, we mentioned the evolution of telescopes, but the way of analyzing the data would also change. You guys have been using artificial intelligence for a long time, haven’t you?
Yes, for a long time. When I started my thesis, the first neural networks were being used in astrophysics. Of course, there is a big difference from those first neural networks to what we have now. However, you need to know how to use it. Otherwise, if you leave matters in AI’s hands without knowing too much, a lot of sloppiness can happen.
An expert must check whether he has interpreted the question correctly and what has come out is correct. In fact, it still does a lot of things wrong. It’s another tool, and I’d say we all use it, to mine data or otherwise look for information. Also as a supplement, to complete what we are finding, and to make graphics. Now, we also use it a lot for programming. So, yes, we have been using it for a long time, and in recent years there have been many advances, and we use it for more things.
One last question, about your other passion: photography. Will you take a photo of the solar eclipse?
No, I do underwater photography, and now, from Madrid, I will have to travel a few kilometers to go to the sea. But I also covered miles in Mexico; the difference is that it is hotter there and you go more frequently.
Taking photos of the sun requires special filters, and mine is a perfectly normal camera. In fact, I am an amateur photographer, and I want to remain being that. If it took on the flavor of need, I wouldn’t enjoy it. And I take pictures for fun, with my normal camera, without any pressure or ambition; for pure pleasure.
