Between the magic of the stars and the complexity of science – El Diario Parana

Despite being among a select group of researchers whose work has received more than a thousand citations in the Web of Science, which indexes articles and research from more than 34,000 scientific journals and publications, Argentine astronomer Julio Navarro expresses that he is still in love with the sky. That captivated him as a boy, on hot nights in his native Santiago del Estero.

Julio Navarro, the famous Argentine astronomer who has lived in Canada for more than 25 years and who was a nominee for the Nobel Prize in Physics, stressed that “everything we have been able to know and study reliably in the laboratory until today cannot be compared.” It constitutes more than 4% of the energy and matter in the universe.” The scientist made statements during his visit to Argentina, where he participated in the Fourth Regional Meeting for Extragalactic Astronomy, which was held in Cordoba.

Born in Santiago del Estero in 1962, Navarro studied astronomy at the National University of Cordoba where he later earned a doctorate. Directed by José Luis Sircech, the Argentine who led the first “atlas” of galaxies in the Southern Hemisphere and whose research led to its appearance. The man from Santiago explained that Sircek’s law is “a quantitative explanation of how stars are distributed in many galaxies, which is still in use.”


Once he received his doctorate, he went to the United States, where he worked at Harvard University as a research associate at the Astrophysical Observatory Center; His professional career continued in the United Kingdom (Universities of Cambridge and Durham), then he returned to the United States (Universities of Arizona and Massachusetts) and has settled since 1998 in Canada, where he works as a professor at the University of Victoria.

The Argentine was included in 2020 in the list prepared by Citation Laureates as a possible winner of the Nobel Prize in Physics, and during these years he investigated the formation and evolution of galaxies and so-called dark matter.

A few days ago, the scientist was visiting the country to participate in the Fourth Regional Meeting for Extragalactic Astronomy, a meeting that Sirceć first organized in 1975 to bring together all areas of extragalactic research, both from the point of view of observation and modeling, and which is being held for the fourth time in Argentina (in addition to… The first edition was held in 1987 and 1996).

In love with the sky ever since the nights he slept in his courtyard in Santiago, Navarro made time in his busy schedule to discuss its history as well as the great mysteries of the universe.

– I start with a basic question, what is extragalactic astronomy?

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– When you go out on a dark night and look at the sky, what you see with the naked eye are the stars, planets, and the moon. All these things we see belong to a galaxy, the Milky Way; Where are we.

Extragalactic astronomy refers to the study of other galaxies, those that cannot be seen with the naked eye, and for which we need a telescope and other means, such as satellites.


– How many galaxies do we know?

-Many, it is not worth counting them; Suppose that at some point this question ceased to be interesting, and today what we ask ourselves is how many galaxies have this or that property, for example, a certain amount of stars, gas, etc.

-Your field is mainly the study of dark matter, what is it?

– The matter that we know, which forms the bodies that we know, such as the sun, the Earth, and others, consists of the elements that make up the periodic table (helium, carbon, iron, etc.) and groups of these elements. Atoms are what make up the known structures.

What we know from astronomical observations is that this matter represents a minority within the total matter that makes up the universe. Our Milky Way Galaxy is made almost entirely of dark matter.

But we know that there is another matter, which we call dark matter, because it has gravitational effects; In fact, if it were not for that dark matter, the sun and stars would have flown away, that is, the Milky Way would not have existed, because what hinders everything is dark matter. Now, what is this dark matter? We do not know.


-What do we know about that dark matter?

-We know where it is and what its effects are, but we do not know what it is, whether it is a fluid, an elementary particle, etc.

The same thing happens with dark energy. The energy we know, which is light, we thought at one time that it was the majority, but today we know that it is not the energy that controls the universe. Rather, there is another type of energy that controls how the universe expands, which is what we call power.dark.

We know about dark energy, how it interacts between galaxies, how it controls the expansion of the universe at this moment, and what has happened before, but not much else.

-Is this one of the major challenges of knowledge today?

-Without a doubt. There are many fundamental questions to which we still do not have answers: for example, the origin of life, whether there is another planet like Earth, etc. In my specialty, cosmology, we also have two fundamental questions that accurately indicate the total stock of matter and energy in the universe.

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From what we observe, dark matter and dark energy make up 96% of the universe, so everything we have been able to reliably know and study in the laboratory to date is only 4% of what exists.

This is the intellectual challenge of our time; Just as the challenge in the Middle Ages was to know how planets move, when eclipses occur, etc., the challenge now is to know what that energy and dark matter is. The day we understand this, fundamental physics will be revolutionized.

Today, when we do science at this level, instead of answers, what we do is open up new, more relevant, more interesting questions.

-I heard him say that he fell in love with the sky in his native Santiago del Estero…

-That’s right, when I was a kid we used to sleep in the yard because it was very hot in Santiago at night, and besides, the electricity went out often. Then when the light of the city disappeared, I remember feeling my eyes starting to get used to the darkness, and I saw more and more stars, as if the sky was becoming brighter and brighter.

I began to realize that if it happened at one time I saw some stars, and if it happened at another time I saw other stars; That there were some constellations that were always observed, and that sometimes the moon was present and sometimes it was not.

The night sky, especially in the southern hemisphere, is beautiful. I fell in love then and still today when I see the sky I feel that deep love.


Everything that is not ordinary matter is called dark matter. They make up about 25% of the universe’s stock of matter and energy and do not appear to interact with ordinary matter in any way other than gravitationally. It was proposed in 1933 by F. Zwicky due to the presence of “invisible mass”, and was later confirmed in the 1970s by measurements of the rotation speed of spiral galaxies.

When you look at galaxies, you imagine them as millions of stars orbiting in a disk, but in reality they are immersed within a huge halo of dark matter.

In the case of the Milky Way, where our solar system is located, this halo is 30 times larger than the galaxy itself. “The Milky Way is just a drop of light within a sea of ​​dark matter,” Navarro says.

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Navarro, Frink and White’s discovery lies in a computer-simulated model that explains how dark matter is distributed in these galactic halos.

This explains the proportion of dark matter present in the galaxy, different interaction relationships (why when the mass of a galaxy increases, the speed of star accretion also increases) and many phenomena that were not fully understood before this discovery.

More specifically, their results are related to the density profile. That is, how the density of dark matter changes as it moves away from its center, and how this aspect applies to all dark matter halos: from small galaxies to massive clusters. “It’s one profile, which we call ‘self-similar,’” Navarro explains.

To understand the concept more simply, it is worth taking as an example the Earth’s atmosphere, which becomes less dense the farther away from the surface we are, which is equivalent to saying that it is less dense the closer we get to space. This explains what the density profile is and applies to dark matter haloes.

The important thing about this discovery is how this profile – when measured – applies to all haloes, regardless of their dimensions. For this reason, it is used in other research and is cited as a basis when used in work that, for example, wants to measure a galaxy cluster: this model is used, which provides a clear prediction that is easy to compare with observations.

she and him

The interviewee studied astronomy at the National University of Cordoba. The doctorate was supervised by José Luis Sircech, who taught for nearly three decades at the Astronomical Observatory of Cordoba and served as director of the institution from 1982-1983.

One of the stories he cherishes from his time as a student at a public university is saving time when a professor threatened to not let him take his course if he returned to the classroom with a dog he found on the street and followed him everywhere. .

At that time, one of the observatory entrance guards did not allow animals into the building, and the dog remained outside waiting for him. Until he once managed to sneak and jump through one of the small windows in one of the basement classrooms, to take cover under his seat.

“The teacher was a strict and serious person and he expelled me from the class,” he recalls, laughing. The dog was called ‘Gori’ and, as he comments, it was in his honor that they later named the group (IMAF Reform Unit Group) which at that time managed the student center in the current Faculty of Mathematics, Astronomy, Physics and Computing.

Myrtle Frost

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