Victor Ambartsumian

Victor Amazaspovich Ambartsumian (Russian: Ви́ктор Амаза́спович Амбарцумя́н; Armenian: Վիկտոր Համազասպի Համբարձումյան, Viktor Hamazaspi Hambardzumyan; 18 September [O.S. 5 September] 1908 – 12 August 1996) was a Soviet Armenian scientist, and one of the founders of theoretical astrophysics. He worked in the field of physics of stars and nebulae, stellar astronomy, dynamics of stellar systems and cosmogony of stars and galaxies, and contributed to mathematical physics.
Ambartsumian founded the Byurakan Observatory in 1946. He was the second and longest-serving president of the Armenian Academy of Sciences (1947–93) and also served as the president of the International Astronomical Union from 1961 to 1964 and was twice elected the President of the International Council of Scientific Unions (1966–72).
He was a foreign member of numerous academies, including the Royal Society, the US National Academy of Sciences, and the Indian Academy of Sciences. Among his numerous awards are Stalin Prize (1946, 1950), the Hero of Socialist Labor (1968, 1978), the State Prize of the Russian Federation, the Gold Medal of the Royal Astronomical Society, the Bruce Gold Medal, and National Hero of Armenia.

Ambartsumian museum in Byurakan

Ambartsumian was born to an Armenian family in Tiflis (Tbilisi) in 1908. His father was the philologist and writer Hamazasp Asaturovich Ambartsumian, the translator of Homer’s Iliad into Armenian. In 1924 Victor entered the physico-mathematical department of Leningrad State Pedagogical Institute and then of Leningrad State University. As a student, in 1926, he published his first scientific article, devoted to sun jets. Ambartsumian continued his postgraduate studies at Pulkovo Observatory, under the guidance of professor Aristarkh Belopolsky in 1928–1931.

His work first came to prominence in physics when in 1929 with Dmitry Ivanenko he published a paper demonstrating that atomic nuclei could not be made from protons and electrons. Three years later this was confirmed when Sir James Chadwick discovered neutrons, which with protons make up atomic nuclei. In 1930 he married Vera Feodorovna Klochihina (born at Lisva, Solikamsk uyezd, Perm). After three years of affiliation at Leningrad University in 1934 Ambartsumian founded and headed the first astrophysics chair. In 1939–1941 Ambartsumian was the director of the Leningrad University Observatory. In 1940 he joined the Communist Party.

The war found him holding the position of the pro-rector of Leningrad State University. The scientific laboratories of the University were evacuated in 1941 to remote Elabuga (Tatarstan) where Ambartsumian spent four years directing the work of the refugee laboratories. In 1939 Ambartsumian was elected a correspondent member of the Academy of Sciences of the USSR. In 1953 he became a full academician of the Academy. In 1943, the Armenian Academy of Sciences was founded. Iosif Orbeli was appointed as the president and Ambartsumian as the vice president of the Armenian Academy of Sciences.

In 1947 Ambartsumian was elected as the president of the Armenian SSR Academy and since then he was invariably re-elected to the position till 1993. In 1993 he became the Honorary President of the Armenian National Academy. In 1946 the Byurakan Astrophysical Observatory was founded. Ambartsumian became its first director and headed the Observatory until 1988. Ambartsumian was the President of the International Astronomical Union from 1961 to 1964. He was twice elected the President of the International Council of Scientific Unions (1966–1972).

Congratulating Ambartsumian on his eightieth birthday, Subrahmanyan Chandrasekhar, who won the Nobel Prize for Physics in 1983, wrote,

The only other astronomer of this century who compares with Academician Ambartsumian in his consistency and devotion to astronomy is Professor Jan Oort; but they would appear to be dissimilar in every other way. It will be a worthy theme for a historian of science of the twenty-first century to compare and contrast these two great men of science. He is an astronomer. There can be no more than two or three astronomers in this century who can look back on a life so worthily devoted to the progress of astronomy.

Ambartsumian died in August 1996 in Byurakan and is buried next to the Grand Telescope Tower.

Physics of stellar shells and gas nebulae

In 1932 Monthly Notices of the Royal Astronomical Society published a paper by Ambartsumian "On the radiative equilibrium of a planetary nebula" nowadays considered to be the cornerstone of the modern theory of the gas nebulae. In a series of research articles by Ambartsumian that topic was developed further. In one of these articles Ambartsumian (with N. A. Kozyrev) managed to evaluate for the first time the masses of the gas shells ejected by the novas. Elaborate methods developed by Ambartsumian were applied in the research of gas shells of the non-stationary stars. The evaluations of the masses proved significant in the problems of the stellar evolution. In particular they resulted in the identification of the symptoms of the pending changes in the life of a star. Ambartsumian laid the foundation of the theory of the star shells and gas nebulae and explained many particularities of their spectra.

Dynamics and statistical mechanics of the stellar systems

In 1936 Ambartsumian gave an elegant solution of a mathematical problem posed by British scientist Arthur Eddington, viz. determination of the distribution of the stars spatial speeds basing on the distribution of their radial speeds. The solution was published in the “Monthly Notices” by recommendation of Arthur Eddington himself. Decades later the same mathematical problem reappeared in the context of medical computer diagnostics. Eventually (in 1979) that mathematical topic was marked by the Nobel Prize in medicine “For the development of computer assisted tomography”. The research conducted by Ambartsumian in the stellar systems statistics and dynamics laid the foundations of the statistical mechanics of the stellar systems. For this particular contribution Ambartsumian was rewarded with the Russian Federation's State Prize in 1995.

In 1935–1937 Ambartsumian engaged in a debate with British scientist James Jeans over the age of the Milky Way, proving that the Milky Way is at least 1000 times younger than the estimate given by Jeans and previously accepted by the scientific community.

The nature of the inter-stellar matter and theory of fluctuations

A series of Ambartsumian's articles is dedicated to the research of inter-stellar matter in the Galaxy. Ambartsumian puts forward an entirely new concept, that the light absorption in the Galaxy is caused by the presence of numerous dust nebulae or “absorbing clouds” in the inter-stellar space. Based on this concept of patchy structure of the inter-stellar absorbing matter the fluctuation theory was developed, which became a new direction in the astronomy.

Ambartsumian's marvelously elegant formulation of the fluctuations in brightness in the Milky Way: in the limit of infinite optical depth, the probability distribution of the fluctuations in the brightness of the Milky Way is invariant to the location of the observer. In the related series of investigations, in part in association with Academician Markarian, Ambartsumian introduced for the first time the now commonly accepted notion that interstellar matter occurs in the form of clouds.

The theory of light diffusion in turbid medium

During the years of the World War II, Ambartsumian created a new theory of light diffusion in turbid media, based on invariance principle invention of his own. Using that mathematical tool Ambartsumian resolved a number of nonlinear problems of the light diffusion. The invariance principle formulated by Ambartsumian and various modifications of this principle presently are being widely used to solve extremely complicated problems in astrophysics, mathematical and theoretical physics, electronics, geophysics, atmospheric physics, and other areas of science. These problems and the associated mathematical apparatus are constantly becoming more complicated, but the basis is still Ambartsumian's invariance principle. In their book Invariant Imbedding, R.E. Bellman, R.E. Kalaba and M.C. Prestrud write that "As a result of this pioneering work, new analytic treatments were made available and simplified computational solutions were obtained. These ideas were further developed and extensively generalized by Subrahmanyan Chandrasekhar in a series of fundamental papers and in 1950 in his book... Many otherwise intractable problems were tamed, and great advances were made." Ambartsumian, himself, held the invariance principle in special regard and always considered it to be one of his most successful and beloved creations. In 1946 for the creation of the theory of lights diffusion in turbid media Ambartsumian was awarded his first Stalins Prize.

The stellar associations, evolution associations and the stars evolution

Stellar associations

Ambartsumian's theoretical analysis based on the observational material for stellar systems belonging to our Galaxy resulted in a discovery of a new type of stellar systems. These expanding systems endowed with a positive energy he named “stellar associations” and proved their relatively young age. This proved to be a revolutionary basis in stellar cosmology, since it implied that the star formation process in the Galaxy is going on even today and the stars are born in groups. In 1950 Ambartsumian was awarded his second Stalin Prize for the discovery and the research of the new type of stellar systems.

The concept of stellar association was not immediately accepted by the astronomical community though. Many years later Subrahmanyan Chandrasekhar wrote: "I recall the early scepticism with which this discovery was received by the astronomers of the 'establishment' when I first gave an account of (Ambartsumian's) paper at the colloquium at the Yerkes Observatory in late 1950."

Observations of expansion (as predicted by Ambartsumian) were reported for some associations, e.g. by A. Blaauw for Perseus II, Scorpio-Centaurus, etc.

The physics of the young stars and the stellar energy sources

Protostar, an early stage of star formation, postulated for the first time by Ambartsumian

No less interesting are the results of Ambartsumian's research in the so-called continuous emission, observed in the spectras of the young stars of the TAU Taurus type and their satellite non-stationary stars. This research led to important conclusions as regards the nature of the stellar energy sources. Ambartsumian's proposed principally new concept of p-star matter. As opposite to the classical hypotheses suggesting that the stars have been formed as a result of condensation of diffuse matter, the new hypothesis postulated the existence of massive bodies, the "proto-stars." The process of disintegration of proto-stars is responsible for the formation of the stars in the associations.

In interpreting the cosmogonic role of stellar associations Ambartsumian's went on to argue the necessity of change to existing views on star formation; namely, for dissolution and against condensation. Clearly, his early work on the expansion of the planetary nebulae and the fact that those objects result from the ejection of the outer layers of stars-the dynamical dissolution of star clusters via evaporation and of associations-created a logical background for his radical conclusion that the basic evolutionary processes in the Universe are not contraction and condensation. On the contrary, they are always outgoing from some denser state of matter. Thus, he postulated the existence of proto-stars, i.e. superdense objects as progenitors of stars, nebulae, diffuse matter, etc.

Extra-galactic astronomy

Ambartsumian dedicated much research to the evolution of the galaxies – huge stellar systems resembling our Galaxy. He authored the new concept of activity of the galactic nuclei (cores, central condensations), to have a decisive role in the genesis and evolution of the galaxies and their systems. Owing to that vision, the study of the grand scale non-stationary phenomena, observed in the galaxies became the central subject of the extra-galaxy astronomy. An important research of Ambartsumian and his followers was dedicated to the blue ejections from the nuclei of the gigantic galaxies, galaxy systems of new type, the so-called compact galaxies, etc. Ambartsumian's first Solvay lecture, delivered in 1958, concerning the explosion of nuclei of the galaxies, was groundbreaking. That first lecture and the development it starts were described by Jerzy Neyman in his article "Reminiscences of a Revolutionary Period in Cosmology." As Neyman recalled, despite initial skepticism, "Ambartsumian’s arguments and many-sided documentation made the attending scholars think, and there followed several important international developments..." Neyman concluded that "Evidence in favor of the Ambartsumian’s hypothesis is now overwhelming. My hearty congratulations to Professor V. A. Hambardzumyan, the Copernican Revolutionary...!"

Quantization of space

Viktor Hambardzumyan on the Armenian bill 100 dram

At the beginning of Ambartsumian's career, at the end of the 1920s and beginning of the 1930s, the range of scientific interests of Viktor Ambartsumian was very far reaching. He studied several extremely timely problems in physics and mathematics. Among the very first of these studies was his talk, given in 1929 at the Kharkov Physico-Technical Institute, where prestigious international conferences on quantum physics were organized at that time. Then Ambartsumian proposed for the first time an entirely new idea regarding the quantization of space. Although is true that the idea was not accepted then, its incorrectness was not proven; Ambartsumian did not continue his studies in this area, somehow obeying the opinion of authoritative scientists who thought that nothing good would result if our continuous space were made discrete.

In his article entitled "On the New Quantum Crisis," about the quantization of space, a pioneer of quantum gravity Matvei Bronshtein, who was shot in 1937, wrote: "Since we are obviously speaking here about a four-dimensional grid that includes both space and time, a privileged coordinate system clearly designates an absolute time and three predominant directions in a motionless space. But this contradicts both the theory of relativity and experiment: in reality space-time is isotropic, all coordinate systems are equivalent in it, and all the equations are, as they say, invariant with respect to Lorentz transformations (that is, they have the same form in all coordinate systems). This is the difficulty with relativistic invariance (invariance with respect to Lorentz transformations) and Heisenberg could not overcome it; a remarkable way of overcoming it has been found by Hambardzumyan and the young Cambridge mathematician Ursell." Almost 80 years have passed since that time, but the problem of space quantization has still not been completely solved, although from time to time some researchers return to the topic, which confirms the ongoing timeliness of the problem.

Quantum field theory

Ambartsumian, together with Ivanenko, first proposed the idea that in the course of interactions of elementary particles with nonzero rest masses, some of them might be created or annihilated. The idea of the creation of particles with nonzero rest masses was absolutely new and did not follow from classical notions. The Ambarzumian – Ivanenko hypothesis of creation of massive particles ( 1930) became a cornerstone of contemporary quantum field theory.

Atomic nucleus

Another paper by Ambartsumian, written jointly with Dmitri Ivanenko in the very beginning of Ambartsumian's scientific career can be included in the list of the most outstanding papers on the structure of the atomic nucleus. Contrary to the prevailing opinion of the time that the nucleus consists of protons and electrons, they proved that free electrons cannot exist within the nucleus and that some neutral particles must be present besides the protons. In fact, this was a prediction of the existence of the neutron, made two years before James Chadwick discovered this particle.

Inverse problems

While still a student Ambartsumian was very much interested in quantum physics, and thoroughly studied the theory of atomic structure, the formation of energy levels, and Schroedinger's equation and its properties, and when he mastered the theory of eigenvalues of differential equations, he pointed out the apparent analogy between discrete energy levels and the eigenvalues of differential equations. He then asked: given a family of eigenvalues, is it possible to find the form of the equations whose eigenvalues they are? Essentially Ambartsumian was examining the inverse Sturm-Liouville problem, which dealt with determining the equations of a vibrating string. This paper was published in 1929 in the German physics journal Zeitschrift für Physik and remained in oblivion for a rather long time. Describing this situation after many decades, Ambartsumian said, "If an astronomer publishes an article with a mathematical content in a physics journal, then the most likely thing that will happen to it is oblivion." Nevertheless, toward the end of the Second World War this article was found by Swedish mathematicians and formed the starting point for a large series of studies. Thus, an article by the 20-year-old Ambartsumian opened up a whole area of research on inverse problems and became the foundation of an entire discipline.

It is interesting to note that when Ambartsumian summarized the types of research results from his long scientific career, he always placed "inverse problems" as a special group of his most beloved creations.

Active galactic nucleus (AGN)

Image of a 5000 light-year long jet being ejected from the active nucleus of galaxy

It was in the early 1950s when Prof. Victor Ambartsumian first raised the issue of the Activity of Nuclei of Galaxies (AGN). In his famous report at the Solvay Conference on Physics (Brussels, 1958) Ambartsumian said that enormous explosions take place in galactic nuclei and as a result a huge amount of mass is expelled. In addition, if this was so, these galactic nuclei must contain bodies of a huge mass and unknown nature. During a break in the session Walter Baade went up to Ambartsumian and said, "Professor Ambartsumian, you have come from the Soviet Union, and I from America. Logically speaking, you should be a materialist, and I an idealist. But what you have just said is nothing other than a pure idealism! It’s fantastic! You speak about some kind of 'non-stellar' objects which no one has seen. So it must be something inexplicable, mysterious."

The idea about the activity of galactic nuclei at first was accepted skeptically and only after many years, under the pressure of observations (the discovery of quasars, radio outbursts of galaxies, consequences of explosions in nuclei, ejection from nuclei, etc.) did it gain recognition. The concept of AGN now is widely accepted.

Ten years after the Solvay conference, at the plenary session of the IAU in Prague, the well-known American astronomer Alan Sandage said, “today, no astronomer would deny the mystery surrounding the nuclei of galaxies or that the first to recognize the rich reward held in this treasury was Viktor Ambartsumian.” As Victor Ambartsumian himself noted, the concept of active galactic nuclei occupies a special place among his scientific ideas. It was proposed by Ambartsumian more than half a century ago and was recognized by the U.S. National Academy of Sciences as revolutionary, on a copernican scale.

Contribution to tomography

Ambartzumian's works contributed to the development of Tomography. In particular He was the first to give numerical inversion of the Radon transform. This involved the 3D velocity distribution of stars in the Galaxy. After many years nobel prize winner for Tomography Allan McLeod Cormack (Dept. of Physics, Tufts University) would write in this connection: "Ambartsumian gave the first numerical inversion of the Radon transform and it gives the lie to the often made statement that computed tomography would have been impossible without computers".

Ambartsumian combined his work in science with lecturing and other pedagogic activity. He is the author of the first in the USSR manual “Theoretical astrophysics” (1939) and a co-author of the course “Theoretical astrophysics” (1952), translated into many languages. From 1931 he lectured at Leningrad University. In 1937 Ambartsumian founded the first in the USSR Faculty of Astrophysics at Leningrad University, which he headed till 1947. In 1939–1941 Ambartsumian held the positions of the Director of the LU Observatory and the pro-rector of LU for science. In 1941–1943 he was the Director of the Elabuga branch of Leningrad University. In 1944 Ambartsumian founded a faculty of Astrophysics at the Yerevan State University. He also founded scientific schools in Leningrad and Byurakan that had influenced many branches of astronomy. Ambartsumian immensely contributed into science popularization by publishing booklets and articles on different problems of astrophysics.

Ambartsumian was a noted science organizer in Armenia, Russia and on the international level. He was the founder and the director of Byurakan Observatory – one of the main astronomy centers of the USSR. As his obituary in the The Independent noted, "Ambartsumian put Armenia on the astronomical map." He was the vice-president and then the president of Armenian Academy of Sciences, member of presidium of Academy of Sciences of the USSR, the vice-president (1948–1955) and the president (1961–1964 of the International Astronomical Union and twice was elected as the president of the International Council of Scientific Unions (1966–1972).

In 1940 Ambartsumian became a member of the Communist Party of the USSR. In 1947 was elected to the Supreme Soviet of the Armenian SSR. From 1948 until 1989 Ambartsumian was a member of the Central Committee of the Communist Party of Armenia. In fact Ambartsumian personified the state policy of promotion of Science in the Soviet Republic of Armenia that included considerable capital investments and repatriation of scientists. He was a permanent delegate from Armenia to the USSR Supreme Soviet between 1950 and 1990, was a delegate of the 19th, 22d and 25th Congresses of the Communist Party of the USSR; in 1989 was elected to the USSR Congress of the People's Deputies.

Ambartsumian was awarded two Stalin Prizes (1946, 1950), the Russian Federation State Award and the M.V. Lomonosov Gold Medal of Academy of Science of the USSR (1971). Ambartsumian was twice nominated the title of a Hero of Socialist Labor, and received many medals and orders.

Ambartsumian was elected as an honoree or international member of the Academies of Science of Austria, Belgium, Bulgaria, Democratic Republic of Germany, Georgia, Denmark, Italy, the Netherlands (1970), the United States, France, Sweden, New York Academy of Science, German Academy of Science (“Leopoldina”) in Halle (DRG), the Royal Astronomical Societies of England and Canada, American Astronomical Society, Philosophical Society of Cambridge, as an honorary doctor of the University of Liège, the Australian National University, La Plata Astronomical Observatory, the University of Paris and the Nicolaus Copernicus University in Toruń. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1958.

Ambartsumian was awarded Gold Medals of the Astronomical Society of the Pacific (1959) and British Royal Astronomical Societies (1960), Gold Medal of Slovak Academy of Science (1970), Prix Jules Janssen of the French Astronomical Society (1956), Helmgolz Medal of German Academy of Science in Berlin (1971), Cotenius Medal of the German Academy of Science (“Leopoldina”) in Halle (DRG) (1974), Medal of the Czechoslovak Academy of Science (1984). A minor planet discovered by T. M. Smirnova on 14 May 1972 in Crimea Observatory was named after Ambartsumian (1905 Ambartsumian).

Named after him

• Minor planet 1905 Ambartsumian
• Byurakan Astrophysical Observatory

• "Victor A. Ambartsumian (1908 - 1996)". Royal Netherlands Academy of Arts and Sciences. Retrieved 6 August 2015. 
• "Book of Members, 1780–2010: Chapter A" (PDF). American Academy of Arts and Sciences. Retrieved 17 April 2011. 

The President of the Republic of Armenia has instituted a new science award: the Viktor Ambartsumian International Prize. It is to be granted for outstanding contributions in the field of astrophysics and in adjacent scientific fields, i.e., mathematics and physics. The prize which is worth of $500,000 will be awarded independently of winner's nationality. The prize was awarded for the first time in 2010.