Interview with the author of the world's most cited article on theoretical astrophysics
What mysteries are concealed in modern astrophysics, why humanities students need to study higher mathematics and how to inspire modern schoolchildren to study astronomy? of Mathematical Sciences, Head of the Department of Relativistic Astrophysics of the SAI MSU.
Nikolai Ivanovich, last year you celebrated your 70th anniversary. But let's remember how in 1973 you, together with astrophysicist Rashid Sunyaev, developed the theory of accretion disks, which underlies the modern theory of X-ray binaries, one of the most cited (over 7,000 references) articles on astrophysics in history. Tell us in words understandable for a person without astrophysical education, what is the essence of the theory of accretion disks?
- The word "accretion" I first heard in the 4th year, when I took the topic of the term paper from Zeldovich. It turned out that accretion is just the fall of matter onto a star under the influence of gravity. The more massive the star, the stronger its attraction. And the force of attraction of black holes is so great that even a ray of light emitted by such a star is turned back by the force of its attraction! And therefore we cannot see or observe such a star.
But it is precisely the phenomenon of disk accretion that allows us to learn something about these unusual stellar objects. The fact is that more than half of the stars in the Universe are not lonely, like our Sun, but double. And sometimes even triple! They revolve around their common center of gravity. If in such a stellar pair one of the stars turns out to be a black hole, with its powerful attraction it will pull on itself the atmosphere of its neighbor. And since both of these stars revolve both around a common center of gravity, and also around their own axis of rotation, this flowing mass of gas winds around the black hole, forming a gas disk around it. The movement of gas inside this disk occurs at tremendous speeds, which leads to the collision of gas particles. And, consequently, to strong heating of the gas in the disk.
This process is accompanied by the release of not only heat, but also light in both the optical and X-ray ranges.
We can already observe the glowing gaseous disk, because it is located at some distance from the black hole, and the latter cannot capture the radiation from the disk. By observing the radiation from this accretion disk, we can learn a lot about the black hole itself and the physical processes in its vicinity, as well as calculate the mass of the black hole, its speed of rotation, and much more.
Together with Rashid Sunyaev (then he was, like me, a graduate student of Zeldovich, now Sunyaev is an academician) at the beginning of the 70s of the last century, we first calculated the possible emission spectra from such an accretion disk. It turned out that most of the energy is emitted in the X-ray range of the electromagnetic spectrum. Almost simultaneously, the results of our calculations were confirmed by observing the accretion disks with instruments installed on the American satellite Uhuru.
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In 1963 you entered the physics department of Moscow State University with a degree in astronomy. However, your parents were not associated with the exact sciences. How then did the decision come to study astrophysics?
- Yes, my parents were not directly connected with the exact sciences. But my father was a front-line soldier and a former tanker. He was well versed in technology, and we, his four sons, passed on an interest in technology and the exact sciences.
Also, I was lucky with the teachers. And even though I did not study in the capital, but in the senior classes at my school (it was in Belarus, in the village of Parichi, near Bobruisk), mathematics was taught by a wonderful teacher Alfred Viktorovich Baranovsky.
Nobody heard of tutors in those years, but the level of teaching even in the village school was such that those who wanted to continue their education could compete in any universities - up to Moscow State University.
Once, while still a student of the 11th grade, in the Bobruisk bookstore I saw the book by Yakov Borisovich Zeldovich "Higher Mathematics for Beginners." I started looking through it with interest - I wanted to find the section where it is shown how to calculate the maxima and minima of functions. The teacher Alfred Viktorovich intrigued us very much! When we passed this topic at school, he said: "But by the method of higher mathematics, such calculations are made easier and more beautiful."
Then I could not even imagine that after only four years Academician Zeldovich would become my scientific advisor.
You are a recognized world authority in the field of modern theoretical astrophysics, you are a member of the International Astronomical Union and the European Astronomical Society. Have you ever had a desire to leave Russia and continue your studies in astrophysics abroad?
- Astronomy is an international science, it is not divided into German, English and French. It is not so important where an astronomer works, it is important what his results are and what is his contribution to the general treasury of human knowledge about the Universe.
I am a theorist, and for work I need my own head, a computer and access to the latest publications (which the Internet provides quite well). Therefore, there is no need to go somewhere. And, by the way, recently international cooperation between astrophysicists has been well established, we are doing joint work, we often meet to discuss scientific problems.
For many years you have been reading special courses for students of the Astronomy Department of the Physics Department of Moscow State University, working with students and graduate students, preparing candidates of science. Do you think that the level of students has decreased or increased recently? And why?
- Previously, there was a huge competition for natural science faculties at Moscow State University - 8-10 people per seat. The selection was the toughest, the strongest entered. But in the wake of this general fashion for physics, many well-trained, but at the same time insufficiently motivated children entered the university. Many of these physicists went into business in the 90s.
Now the competition has become smaller, but real amateurs of astronomy enter the university. Wonderful and strong students come to me to take topics for term papers and theses!
What topics are you working on at the moment?
I am currently continuing to investigate various types of complex accretion discs.
What do you think is the state of modern astrophysics in our country?
- Russian astrophysics now faces a number of difficulties. In particular, our country has difficulties in funding science. These problems have especially affected observational astronomy: modern telescopes are very expensive. Nevertheless, Moscow State University recently built an excellent observatory with a modern telescope near Kislovodsk. We have high hopes for this observatory.
Good results are obtained by an automatic network of small telescopes developed in our country under the leadership of Moscow University professor Vladimir Lipunov - the Master system, with which one can continuously observe the sky in many parts of the world. This system, by the way, has already revealed many previously unknown stellar objects.
How to explain to a person far from science, what is the point of spending on astrophysical research? What is the practical meaning of such research?
- Trying to look beyond the horizon is a very human quality! Otherwise, how would we differ from animals? Investments in the development of space systems are already providing very tangible benefits for the national economy. I'm talking about tracking the movement of atmospheric vortices, fixing and assessing areas of forest fires from space, tracking and forecasting asteroid hazard. The list goes on.
In addition, a country without developed astronomy cannot claim the role of a great world power - it will be doomed to rely on someone else's information, it will not have incentives to develop its scientific base for fundamental science. All this will lead to the degradation of society and the country, to its lag behind other states.
And astronomy is also the most philosophical science: we have to imagine in what world and in what universe we live.
Most modern schools no longer have astronomy. What do you think about this? How, in your opinion, can a modern schoolchild be inspired to study astrophysics and astronomy?
“Both the teaching of astronomy in schools and the quality of textbooks leave much to be desired. The lack of astronomy in schools can (and should!) Be compensated for by a good and systematic showing of popular science films and television programs. Perhaps it will even have a greater effect than studying a boring textbook presented by boring teachers.
There is a series of great BBC films on astronomy that should be purchased and shown more often on television.
It would also be good to create interactive teaching programs on astronomy on the Internet with the opportunity to receive advice and answers to questions of interest from qualified astronomers-specialists.
I would also like the country to have more planetariums - at least in every regional city! And at the planetariums - thematic circles for lovers of astronomy.
A certain minimum of astronomical knowledge should be given, of course, at school as well - perhaps by supplementing a physics textbook with chapters on the basics of the structure of the Universe and our solar system.
What, in your opinion, are the main mysteries of modern astrophysics? The nature of black holes, the formation of exoplanets?
- One of the main mysteries is dark matter, which is not visible, but manifests itself in gravitational effects. Visible matter is visible stars, star clusters, gas clusters, and this is only 4% of the substance of the Universe! Everything else is mysterious dark matter and equally mysterious dark energy. Anyway, the exploration of our solar system constantly brings new surprises and new unexpected discoveries. And in the solar system, believe me, there are still many unknowns.
Today there is a huge gap between scientists and society. Astrophysics, for example, is an area that strikes fear in the average humanist. How can this gap be overcome and is it possible in conditions when even physicists working in different fields do not always understand the subject of each other's research?
Society needs to watch popular science films on astronomy - then the gap will narrow and the fear will disappear.
As for the narrow specialization - it is inevitable, but for this, the basic university education is given - the foundation that makes it easy to switch and easily engage in various fields of research.
This is precisely the advantage of our system of training scientific personnel, which developed in the 1950s and 1960s. Unlike, for example, American, with its too early narrowly focused specialization.
And for the humanities it would be good to introduce a mandatory minimum course in higher mathematics, because this is a basic element of the general culture - the culture of thinking! There will be fewer problems in mutual understanding, there will be less disunity in society.
Remember that, entering the humanities faculty of the university, Lev Nikolaevich Tolstoy passed the entrance exam in mathematics. And he got a ticket with Newton's binomial!
Ekaterina Shutova