25 Interviews for the FNP’s 25th Anniversary: an interview with Prof. Grzegorz Pietrzyński, astronomer, by Anna Mateja

Dodano: :: Kategorie: 25 years Foundation for Polish Science
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The Foundation for Polish Science (FNP) celebrates its 25th anniversary this year. To mark the occasion, we have invited 25 beneficiaries of our programmes to tell us about how they “practise” science. What fascinates them? What is so exciting, compelling and important in their particular field that they have decided to devote a major part of their lives to it? How does one achieve success?

The interviewees are researchers representing many very different fields, at different stages of their scientific careers, with diverse experience. But they have one thing in common: they practise science of the highest world standard, they have impressive achievements to their credit and different kinds of FNP support in their extensive CVs. We are launching the publication of our cycle; successive interviews will appear regularly on the FNP website.

Pleasant reading!

Clear sky over Cerro Paranal

An interview with Prof. Grzegorz Pietrzyński, astronomer, by Anna Mateja


Photo: Prof. Grzegorz Pietrzyński, photo by fot. Magdalena Wiśniewska-Krasińska

ANNA MATEJA: Why can’t you pursue astronomy all by yourself?

GRZEGORZ PIETRZYŃSKI: You can, and works by an individual author are still sometimes published, or concepts are realized from beginning to end by one scientist. But when state-of-the-art instruments made it possible to survey vast regions of the sky, observing millions of stars every night, teams naturally began to form. In the case of our research, over the course of 15 years conducting measurements of distances in the Universe we have obtained observing time on nearly 30 different telescopes in several observatories on different continents. In total, my colleagues and I have worked 2,000 nights. Would a single virtuoso be capable of that, however well-organized and ambitious? People are also needed to sift through the vast resources of data for the most interesting objects, which then undergo further complex study. It is also the policy of institutions financing research to foster the pursuit of science in teams. These institutions invest a lot of money and expect to see results in the form of publications and citations. By the nature of things, a team has greater penetrating force than an individual. Even though the era of virtuosos is ending, personality still has a decisive importance for the practice of science: passion, perspicacity, perseverance in striving for goals, skill at posing the right questions.

And establishing cooperation.

Right. Success also depends on reaching the right people, giving them room to show what they can do, and controlling the entirety enough, without limiting anyone, to create a smoothly running team. That’s how I try to run my own team of colleagues, while ensuring each of them autonomy. I don’t impose the topics. Each one chooses what he cares about the most. Thus some handle pulsating stars, for example, which are used to measure distances in the cosmos, while others examine eclipsing star systems. On the other hand, we still work together, because our research has common elements: we share our experiences, make joint observations, and analyze data together. This team concept seems to work, as my colleagues are defending their doctoral dissertations, completing their postdoctoral degrees, and working their way up the scientific ladder. But first and foremost they are independent, which enables them to grow within their own fields. And I have to say that some of them have already become world-class experts.

How do the advantages of having a team carry over to measuring distances in the Universe?

First it should be pointed out that a precise measurement makes it possible to determine the distance to a selected object and also its properties (such as the quantity of energy it emits), and in some cases also the nature of the object. This is the basis for all astronomical research, including development of 3D maps of the sky for examining the evolution of the Universe. Because there is no one single method of measuring distance in the cosmos, various cosmic yardsticks are developed. Some are more precise than others, but they are all important because we want to measure the same distances using different yardsticks—this allows us to check for mistakes. And with a research team, we can carefully study the many different methods to identify the most precise ones. Also, calculating distances to the farthest objects works in a team because this type of operation is so complex and labour-intensive that it must be performed in several steps. First we measure the distance to nearby galaxies, where we seek objects with constant brightness, known as “standard candles,” and we establish their brightness. Then, observing them from afar, we use them to measure distance. Thus, painstakingly, rung by rung, we create a “cosmic distance ladder.” It’s just the same as if we tried to measure the distance from Zakopane to Gdańsk using a 20-cm ruler. We lay down the ruler 10 times to create a 2-m measure, then use that to create longer and longer measures, until finally we establish the distance between the two cities. Astronomers do the same thing, but on the scale of cosmic objects.

In 2013 the team you head announced in the journal Nature the distance from Earth to the Large Magellanic Cloud to an accuracy of within about 2%. Why is this galaxy near Earth so significant for measuring cosmic distances?

Ever since 1929, when Edwin Hubble linked the distance of galaxies with “recessional velocities,” and thus proved that the Universe was expanding, measuring Hubble’s Constant describing the speed of expansion has been regarded as one of the most important tasks of astrophysics. After decades of tests and calculations seeking to state the precise value of Hubble’s Constant (which is necessary to predict the fate of the Universe and to identify the nature of the dark energy that makes up 75% of its mass), it was determined that we are three steps away from achieving this. Step one: calculating the distance to the Large Magellanic Cloud (which my team succeeded in making more accurate). Knowing the distance to that galaxy, we can estimate the brightness of the numerous cepheids found there—pulsating stars that are excellent indicators of distance. It’s like observing light bulbs of unknown luminance from a certain distance: if we know the distance, we can use that to determine the luminance. Step two: by observing cepheids in other galaxies, we can measure the distance to farther and farther objects, extending as far as galaxies where we have observed explosions of type Ia supernovae. Step three: knowing the distance to several supernovae, we can determine the power of these splendid cosmic light bulbs, and use that to determine distances on a cosmological scale, and the Hubble Constant.

As we can see, precise and accurate measurement of the distance that separates us from the Large Magellanic Cloud is the most important measurement for building the cosmic scale of distances, because it is the first one. And the hardest. It’s the first rung on the cosmic distance ladder. Construction of the ladder begins with determining the distance to the closest objects, so that can be used as the basis for estimating secondary distance indicators. Those in turn should lead us to measuring the distances to the farther parts of the Universe. The enormity of this challenge is evident from the over 500 estimates of the distance to the Large Magellanic Cloud, the most accurate of which were precise to about the nearest 10% and often required additional assumptions, which further impeded their verification. Our research improved the accuracy of the measurement by 5-fold.

Determining the precise value of the Hubble Constant will also allow us to study the nature of dark energy in the cosmos. Why do want to know what that is?

Dark energy is just one of many examples of revolutionary changes that have been made in astronomy thanks to measurement of distances. What is dark energy? It’s the main ingredient of the Universe, making up nearly 75% of its contents, with dark matter accounting for a further 20%. This means that we have knowledge of only about 5% of the sky observed through telescopes.

The millions of stars viewed every night are just 5%?

Yes, so we can really say that we do not understand the Universe. We don’t know what dark energy is or what it is made of. One of the methods for studying it is to precisely measure the value of the Hubble Constant at various stages of evolution of the Universe.

When did you travel to Chile for the first time to observe this 95% unknown through the best telescope in the world?

In 1996, and if I added up all the time I have spent there it would come out to at least 7 years. Every year I spend about 30% of my time in Chile—including many nights at Cerro Paranal, or at Las Campanas, in the Andes of northern Chile, in the Atacama Desert. If you work out the connections you can get there via Paris and Santiago in 24 hours. I have flown over 2 million miles on various airlines!

But the observatories in the Atacama Desert have undeniable advantages for astronomers: at least 300 cloudless nights per year, dry air (total annual precipitation not exceeding 100 mm), and the right altitude (about 2,500 m above sea level).

The climate and the altitude where optical observatories (the kind we use) are built enable avoidance of convective clouds, which usually don’t rise that high. Sometimes in the morning you can see an ocean of clouds spreading out hundreds of metres below the observatories. It is so beautiful that sometimes I don’t go to sleep even though I’m exhausted from watching the sky all night—just to see those clouds again. And if I had just a little more strength, I’d drive down the mountain to dive into the clouds and feel a little moisture.

You have to apply for the right to work on these telescopes, just like applying for a research grant.

And it’s not easy. In the case of the big telescopes, like the ones in Chile, South Africa, or the Canary Islands, there are often 10 applications for every spot in the competitions held twice per year.

Where does all the competition come from?

Luckily there is competition! It is thanks to competition that only the best projects are carried out. The number of applicants shouldn’t come as a surprise. The astronomy community is fairly numerous, but there are just a few powerful telescopes, expensive to maintain, with well-equipped instrumentation. The observatory at Cerro Paranal, where a night of work on the telescope can cost as much as EUR 100,000, was built by the European Southern Observatory thanks to funding from numerous European countries (including Poland), and it is maintained by them. Clearly, telescope time is one thing, but first you have to obtain a grant to finance the research.

So astronomers are doubly at risk.

Triply, because you have to add the good fortune to have a cloudless night—otherwise the time is wasted and you have to compete again. We applied twice for telescope time at an excellent observatory in Hawaii, located at the peak of a volcano. Each time we were successful, although it is a tough competition to win. The first time there was a hurricane and the second time an earthquake, and the portion of the project requiring observations from the telescope there has still yet to be realized.

Generally the difficulties are on a different scale, that is, they can be overcome, as I have seen for myself more than once. In 1999 one of the first optical afterglows around gamma-ray bursts occurred. It was a mysterious phenomenon, and no one knew what it was because the distance from which it was visible was unknown. I observed one of them, performing my everyday telescope reduction and then sketching the curve of the changes in the flash. When the night was ending, and along with it the possibility of observation, I dispatched telegrams to colleagues in other parts of the world so they could observe the afterglow further. Afterwards several papers were written on this topic, some of them published in prestigious journals.

Your scientific CV mentions several articles in Nature—a rarity among Polish scientists. When was the first time you published in Nature?

In the late 1990s, when I was nearly 30. If I’m not mistaken, there have been 8 articles there so far (and three in Science). In the case of three of the works, which are the main thrust of our project, I was the lead author, in the others a co-author. Polish astronomy is practised at an excellent level and is a force to be reckoned with in global science. When I announced that we were recruiting for a research team after winning funding in the TEAM programme of the Foundation for Polish Science, out of nearly 30 submissions only three or four came from Poland. The rest of the candidates were from nearly the entire world: the US, Germany, France, China, India, Japan. Some of them even offered to work for free, just to have the chance to participate in this research with us. I understand this degree of commitment, and I wrote my own doctoral dissertation pretty rapidly. It took me three years to write the dissertation, which involved star clusters in the Large Magellanic Cloud, also used to determine distance in the cosmos (for example, the location of Earth in our galaxy was determined thanks to observations of star clusters).

What drove you forward then?

Curiosity. Passion. The deeper you hike into the forest the more trees there are.

Or stars in this case.

We seek the answer to one question, and when we finally find it, it turns out that it generates more questions, and then others. It draws you in more and more. To this day I like to make all observations personally, even though I could order some of them from the observatory staff by providing them with the technical details.

Why is your own eye better than the eye of the staff?

You need to know how the observation was conducted, because this enables a more skilful analysis of the data. Besides, every astronomer thinks that he knows best how to make an observation. I have that too! Whenever I find myself under a telescope, it always seems to me that I do it more precisely than others: because I shift the telescope a half-second earlier or later, and that surely has some influence on the result. But more seriously, there is something in this, because we have reached such a level of complexity in the subject that you can’t allow yourself any carelessness or over-generalization.

Why is it that in your home village of Pomiechówek, near Nowy Dwór Mazowiecki, astronomy seemed the most interesting to you? After all, there are lots of attractive career paths open to people with excellent grades in physics and mathematics.

So many fields I was interested in! I wanted to be a biologist, then a sportsman. As a teenager I played volleyball, and because I attended a sports school I spent most of my time on the playing field, not over the books. I quickly realized that playing professional sports was not a good recipe for life, and I had decided on physics. Then two of the girls in my class said that they were applying for astronomy. So I began to wonder: maybe it really would be better to choose that course of study, because there a knowledge of physics would help discover something new? And you could also wrestle with the philosophical questions that arise in the context of the natural sciences: Where does life come from? What is mankind’s place in the Universe? Where are we headed? Finally the girls did not take astronomy, but I passed the exam. Many of my fellow students were winners of astronomy olympiads or had already made their first observations. I had no concept of anything but began my studies to learn something.

How did you know that this was exactly the thing you wanted to devote your life to?

It’s not something you know, you have to feel it. I was in an exceptional class, because usually there were one or two people finishing astronomy studies per year, but in my year there were three astronomy graduates. Now we have several PhD students, but when I worked for over a decade at the University of Warsaw, apart from pursuing research I taught students, and that was a thrill. I got to know highly talented young people who passed their exams with flying colours. But not all of them could step beyond repeating the existing knowledge, and they had difficulty approaching independent work. While every discipline requires full commitment, as well as determination and character, astronomical research is something you have to enjoy, or even find amusing, because it is hard and the career is particularly gruelling, so it’s easy to break away from it at various stages.

I have no doubt you are entertained by your work. But what causes difficulties?

I will say this. In 2007, thanks to a grant from the FOCUS programme of the Foundation for Polish Science, I created my first research team. I had just returned from a postdoctoral fellowship at Universidad de Concepción in Chile, which I continue to cooperate with, and I was already working on cosmic distances, so it was high time. In this sense it was that grant that was one of the most important I have ever received, because it allowed me to catch the wind in my sails. The TEAM grant awarded three years later allowed my team to expand, but more importantly to continue. The reality is that scientific institutions do not finance the creation of research teams, so scientists treat raising the funds for their activity as their own obligation. Grants are usually given for three years, or larger ones for five years. If I don’t raise funds in time, my group, which now numbers 10 people, will fall apart. And because I feel responsible for their careers, it seems natural to me that I have to write grant applications and observatory applications, accounting settlements and reports. I have at most 20% of my time left over for scientific work, and that is the difficulty you were asking about.

When do you have the awareness that you are peering into the workings of the Universe?

During a long exposure, when the telescope observes and records one object for an hour, say, and I can go outside and gaze at the sky with my naked eye, without all that fantastic equipment—paradoxically, that is the most wonderful.

And when I have more free time, I head to the southern Andes and often visit the Mapuche Indians, who have inhabited these lands since pre-Columbian times. This nomadic tribe survived the Spanish conquest probably only because they had not created any social structure. They have no chief and don’t build cities. The society functions on the basis of the family. I don’t talks about the stars or the expansion of the Universe with them, although I have learned their language. But when I told them that we named the project of studying distances in the universe “Araucaria”—from the name of the tree whose seeds are the basis of their sustenance—they were moved that foreigners could appreciate what is sacred to them.

Is that how you gain some distance from your arduous research?

Regardless of the scale, distance is always prized. Particularly in astronomy, where we are not always dealing with great discoveries, but there is no lack of fascinating discoveries, such as describing the accelerated expansion of the Universe. But most of our work is solid research that only prepares the way to great discoveries.

And is there still room in science for great discoveries?

Certainly! When the concierge at the hotel in Concepción where I stayed on my last visit to Chile learned that I am an astronomer, he asked, “Have any revolutionary discoveries been made in theoretical physics since the 1920s?” I answered honestly, “No.” We are waiting for them—the quantum theory of gravity at the least. But in the meantime we are making a number of very interesting discoveries for which scientists are winning Nobel prizes, such as the Higgs boson—the next elementary particle—or registration of the existence of gravitational waves. But as I said, every discovery brings more questions than answers. We are still waiting for a discovery that would allow us to say what the Universe is like—what is dark energy and dark matter—so that we can finally go beyond the 5% that we already know.

PROF. GRZEGORZ PIETRZYŃSKI (born 1971 in Nowy Dwór Mazowiecki) works at the Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences in Warsaw. He is a winner of the FNP programmes FOCUS (2007), TEAM (2010) and MENTORING (2012). In March 2016 he received a EUR 2.4 million grant from the European Research Council for advanced researchers to pursue the next phase of his research seeking to determine the speed of expansion of the Universe (“A sub-percent distance scale from binaries and Cepheids”).