MacTutor
With the death of Ernst Julius Öpik in Bangor, Co. Down, Northern Ireland, on September 10, 1985, the international astronomy community lost one of its most distinguished senior members. His scientific work, carried out in the Soviet Union, Estonia, the United States, Germany, and Ireland, covered almost the whole of astronomy and extended over seven decades. Öpik's ideas were based on keen insight into physical behaviour; their perceived importance tended to increase rather than decrease with the passing years.
Ernst Öpik was born at Port Kunda, Estonia, on October 23, 1893, as a member of a large family. He attended high school in Tallinn until 1911 and entered Moscow University in 1912. He had to augment his income by teaching, but already in 1911-12 his first published notes on astronomical observation appeared in the Russian astronomy journal Mirovedenie, on Venus and Mars and on the Perseid meteors. Interest in meteor astronomy remained with him always, and by 1970 it was possible to list 70 titles of his papers in this field. His particular interest was to investigate, in a long series of papers over 30 years from the early 1930s, the physical processes involved in light emission from meteors. He also took part in the Harvard program of meteor observation. He thought at one time that there was evidence for hyperbolic velocities, but later he found that an assumed statistical uniformity had caused an unwarranted inference
Having graduated with honours in 1916, Öpik joined, in 1919, the groups of academics who were to travel to Tashkent to establish a Turkestan University there in the context of the new Soviet state. In a reminiscent and widely read article of 1977, he recalled 'A University Trek to Central Asia,' a 70-day journey in the freezing winter weather beset by turbulent night raids and by means of a locomotive fueled by wood gathered along the way. His work at Tashkent, which is now an astronomical centre of importance, was generally successful, but he found little taste for the new order and he returned in 1921 to his beloved Tartu in Estonia. He obtained his doctorate there in 1923 with a thesis on meteor observations. There followed for Öpik a prolific period, including the years 1930–34 as a Visiting Lecturer at Harvard College Observatory. He became known to many astronomers who emanated from Harvard; He impressed everyone with the breadth of his knowledge and his skill in astronomical reasoning. Later he returned to Estonia and established his family home there. In 1940-41 Estonia was occupied by the forces of the Soviet Union. Estonia's independence from Russia had always been precarious. For many centuries the country was under the rule of various foreign powers, among them the Teutonic Order, the Swedish crown and the Czars of Russia. Land ownership had been in the hands of a German-speaking aristocracy. In the 1920s compensation for land reform was paid by means of a loan from the League of Nations. In the ensuing years there were pseudo-fascist as well as popular movements. Following the German occupation in 1941, and with the Russian armies about to re-occupy Estonia in 1944, Öpik and his family moved from their farmstead home by horse and cart and eventually reached Hamburg Observatory, where they were hospitably received by Otto Heckman. In the aftermath of the War there was set up, for the scholars and students among the great mass of displaced persons, in Hamburg, the Baltic University. Ernst Öpik became Professor of Astronomy in that organization and Rector for Estonian students. However, that situation could not be permanent. Fortunately, with Öpik's plight becoming known to his former Harvard associates, one of them, Eric Lindsay, director of Armagh Observatory from 1937, who had taken his PhD degree while Öpik was at Harvard, was able to offer him, in December 1947, a special post as Research Associate at Armagh. In this way Armagh Observatory gained a distinguished staff member. On reaching Armagh with his family in June 1948, Õpik was 54 years old and had already been employed as an astronomer for 30 years; even so, he was not yet halfway through his professional career.
At Armagh Observatory, the Öpik family started a new life, and this included entering post-war astronomy, such as it was, with zest. Even though he was a staff member of a very small establishment, Öpik was able to make much more of it, with his broad and devoted interests, than most others. He was especially helped by being in touch with astronomy in the United States through quasi-annual study and lecturing visits to the University of Maryland near Washington, DC.
Öpik's interests spanned a horizon of literally cosmic proportions, and he achieved remarkable insight into the physics of the astronomical world. We can only comment in detail here on his work in stellar physics; to comment meaningfully on all areas to which he contributed would require another Ernst Öpik!
An early piece of work, in 1915, considered the surface brightness and densities of the binary star Eridani, where Öpik correctly estimated a stellar density of gmcm. At about the same time, Adams determined the spectral type of Sirius B and thus discovered white dwarfs. Unfortunately, Öpik regarded the density he found as 'impossible' and thus a major discovery at the age of 22 eluded him. It is tempting to suggest that this experience convinced him of the necessity to follow through to an ultimate conclusion any apparently sound idea, even if there appeared to be serious difficulties. This determination led him occasionally, but not often, into a position that subsequently proved to be erroneous
In the field of stellar physics, perhaps Öpik's best-known insight concerns the role of non-uniform chemical composition in determining the internal structure of giant stars. The fact that chemical non-uniformities are created and could be built up inside a star such as the Sun, as a result of nuclear transformations, was recognized by Öpik as a possible source of occasional mixing periods for the solar core. He used this as a model for solar variation on the longest known timescale (of the order of 100 Myr), which can be traced in the Ice Age record. Õpik's model of episodic mixing in the solar core has recently become of renewed interest as a possible explanation for the 'missing' solar neutrinos due to the hypothesis that the current flux is non-representative.
Less well-known was his insight into the turbulent mixing of gas flows in stellar convection zones. This mixing provides an important source of energy exchange in the upper layers of cool stars, where conditions are far from adiabatic. Õpik succeeded in parameterizing the mixing based on measurements of turbulent air flow near the ground, which he himself had made in Estonia as part of civil defense measures against chemical warfare. Ironically, his first application of his model of convection to the Sun was made when war had forced him to become a refugee; the work was eventually published in the Monthly Notices of the Society.
The possibility that the violent death of one star might serve to spawn a new generation of stars was a daring idea when Öpik first proposed it in 1953. The process of vindicating this insight by acquiring new astronomical data and other contributions lasted almost 30 years. Öpik appreciated that a more quiescent process of star formation might also be required to account for the appearance of new stars in dust clouds. In such cases, perhaps applicable to the formation of low-mass stars, he pointed out that the collection of a dust core may play a primary role in the agglomeration of a new star. Once again, this gives rise to the possibility of chemical non-uniformities in the interiors of low-mass stars, with possible consequences for neutrino generation.
The breadth of Öpik's grasp of matters astronomical was truly astounding It is difficult to understand how he managed to keep abreast of developments in so many different areas, so as to be able to return again and again to certain topics, perhaps after 10 years of silence, in order to provide incisive commentary. One of his methods centred around a system of summarising succinctly the contents of a paper in a notebook, where the material was grouped according to subject areas. His years as a refugee had taught him the value of a sheet of paper and his literature summary reflected this; the writing was small and every last square inch of the sheet was used. Thus many years of journal articles could be summarized in a notebook which could be carried in a pocket. One of us (DJM) has first-hand experience of the value of such a system; he still uses a notebook purchased in Armagh when he worked with Öpik in 1970. Each entry is made in writing which is as small as possible and, as a result, on any page one is confronted with a personalized summary of articles in a particular topic acquired over a 2-3 year period.
In 1950, by the initiative of Eric Lindsay and with the active support of Hermann Brück in Dublin, the Irish Astronomical Society began publication of the Irish Astronomical Journal with Ernst Öpik as editor. The proprietorship of the Journal changed after a hiatus from 1960 to 1962, during which time Öpik's 'News and Comments' were much missed; Õpik remained as chief editor until 1981 and he was still an associate editor at the time of his death. His formal retirement from Armagh Observatory took place in 1981. During those decades the Irish Astronomical Journal became 'Öpik's Journal'; in an economical form it acted as a repository for much of his thinking, astronomical, scientific and philosophical.
For 33 years at Armagh, with interludes at College Park, Öpik worked unremittingly on tasks of high attainment or, if necessary, at a humble level. In a Special Issue of the Irish Astronomical Journal, Volume 10, published in 1972 but intended to mark his 75th birthday in 1968, there were collected together testimonies from just a few of his friends and associates. In 80 pages, a remarkable variety of contributions was referenced, a total of nearly 300 published papers, with considerable support by way of personal reminiscence. The final section presented Öpik's fluency in musical performance and composition, and it seems likely that he could have made a successful career in music. In 1974, by a generous act, he presented Armagh Observatory with Dr. Lindsay's piano, where it gently reminds visitors of their cultural heritage.
Ernst Öpik, especially in later years, was often reckoned to be 'difficult,' a reputation partly produced because of his one-man running of 'his' journal. At meetings he would sometimes become a formidable critic either of scientific matter, of notation, or of presentation. At the age of 80 he had, perforce, to undertake the duties of Acting Director of Armagh Observatory, following Eric Lindsay's sudden death in 1974. This could have been difficult indeed for his colleagues, but it was not so. He was always tolerant of those whose actions were well-founded, even though he might have favored a different course. He was aware of his own shortcomings, even if he gave the impression of admitting no lapse. What he sought was firm and sound confrontation and challenge, and he did not always meet his match! Altogether he was, at his best, an entertaining personality. He could be depended on, when a suitably festive occasion came, to lighten any gathering with humour and pathos.
Ernst Öpik received many honours for his contributions to astronomy He was a Fellow of the Estonian Academy of Sciences from 1938, a Member of the Royal Irish Academy from 1954, and a Foreign Associate of the US National Academy of Sciences from 1975. He was also a Foreign Honorary Member of the American Academy of Arts and Sciences from 1977. He was conferred with Honorary Degrees of Doctor of Science by Queen's University, Belfast, in 1968 and by the University of Sheffield in 1977. He was a recipient of the J. Lawrence Smith Medal of the US National Academy of Sciences in 1960, the F.C. Leonard Medal of the International Meteoritical Society in 1968, one of six Gold Medals of the American Association for the Advancement of Science in 1974 in connection with the fourth centenary of Kepler's birth, the Gold Medal of the Royal Astronomical Society in 1975, and the Catherine Wolfe Bruce Gold Medal of the Astronomical Society of the Pacific in 1976, and the Louis Jacot Grand Prix, Pensée University, Paris, in 1978. He was elected a Fellow of the Society in 1949.
Ernst Öpik is survived by his second wife Alide, who shared his experiences of departure from their native country and resettlement in Ireland, and by one son and five daughters. These are Dr. Uno Öpik, Senior Lecturer in the Department of Applied Mathematics and Theoretical Physics at Queen's University, Belfast; Dr. Helgi Öpik, a Senior Lecturer in Botany at University College, Swansea; Dr. Tiiu Miller, a psychologist formerly at the University of Edinburgh; Elina Jaanits at the Estonian Academy of Sciences; Inna Strauts, retired; and Maija Konston of the US Library of Congress.
P.A. WAYMAN
D.J. MULLAN
Ernst Öpik was born at Port Kunda, Estonia, on October 23, 1893, as a member of a large family. He attended high school in Tallinn until 1911 and entered Moscow University in 1912. He had to augment his income by teaching, but already in 1911-12 his first published notes on astronomical observation appeared in the Russian astronomy journal Mirovedenie, on Venus and Mars and on the Perseid meteors. Interest in meteor astronomy remained with him always, and by 1970 it was possible to list 70 titles of his papers in this field. His particular interest was to investigate, in a long series of papers over 30 years from the early 1930s, the physical processes involved in light emission from meteors. He also took part in the Harvard program of meteor observation. He thought at one time that there was evidence for hyperbolic velocities, but later he found that an assumed statistical uniformity had caused an unwarranted inference
Having graduated with honours in 1916, Öpik joined, in 1919, the groups of academics who were to travel to Tashkent to establish a Turkestan University there in the context of the new Soviet state. In a reminiscent and widely read article of 1977, he recalled 'A University Trek to Central Asia,' a 70-day journey in the freezing winter weather beset by turbulent night raids and by means of a locomotive fueled by wood gathered along the way. His work at Tashkent, which is now an astronomical centre of importance, was generally successful, but he found little taste for the new order and he returned in 1921 to his beloved Tartu in Estonia. He obtained his doctorate there in 1923 with a thesis on meteor observations. There followed for Öpik a prolific period, including the years 1930–34 as a Visiting Lecturer at Harvard College Observatory. He became known to many astronomers who emanated from Harvard; He impressed everyone with the breadth of his knowledge and his skill in astronomical reasoning. Later he returned to Estonia and established his family home there. In 1940-41 Estonia was occupied by the forces of the Soviet Union. Estonia's independence from Russia had always been precarious. For many centuries the country was under the rule of various foreign powers, among them the Teutonic Order, the Swedish crown and the Czars of Russia. Land ownership had been in the hands of a German-speaking aristocracy. In the 1920s compensation for land reform was paid by means of a loan from the League of Nations. In the ensuing years there were pseudo-fascist as well as popular movements. Following the German occupation in 1941, and with the Russian armies about to re-occupy Estonia in 1944, Öpik and his family moved from their farmstead home by horse and cart and eventually reached Hamburg Observatory, where they were hospitably received by Otto Heckman. In the aftermath of the War there was set up, for the scholars and students among the great mass of displaced persons, in Hamburg, the Baltic University. Ernst Öpik became Professor of Astronomy in that organization and Rector for Estonian students. However, that situation could not be permanent. Fortunately, with Öpik's plight becoming known to his former Harvard associates, one of them, Eric Lindsay, director of Armagh Observatory from 1937, who had taken his PhD degree while Öpik was at Harvard, was able to offer him, in December 1947, a special post as Research Associate at Armagh. In this way Armagh Observatory gained a distinguished staff member. On reaching Armagh with his family in June 1948, Õpik was 54 years old and had already been employed as an astronomer for 30 years; even so, he was not yet halfway through his professional career.
At Armagh Observatory, the Öpik family started a new life, and this included entering post-war astronomy, such as it was, with zest. Even though he was a staff member of a very small establishment, Öpik was able to make much more of it, with his broad and devoted interests, than most others. He was especially helped by being in touch with astronomy in the United States through quasi-annual study and lecturing visits to the University of Maryland near Washington, DC.
Öpik's interests spanned a horizon of literally cosmic proportions, and he achieved remarkable insight into the physics of the astronomical world. We can only comment in detail here on his work in stellar physics; to comment meaningfully on all areas to which he contributed would require another Ernst Öpik!
An early piece of work, in 1915, considered the surface brightness and densities of the binary star Eridani, where Öpik correctly estimated a stellar density of gmcm. At about the same time, Adams determined the spectral type of Sirius B and thus discovered white dwarfs. Unfortunately, Öpik regarded the density he found as 'impossible' and thus a major discovery at the age of 22 eluded him. It is tempting to suggest that this experience convinced him of the necessity to follow through to an ultimate conclusion any apparently sound idea, even if there appeared to be serious difficulties. This determination led him occasionally, but not often, into a position that subsequently proved to be erroneous
In the field of stellar physics, perhaps Öpik's best-known insight concerns the role of non-uniform chemical composition in determining the internal structure of giant stars. The fact that chemical non-uniformities are created and could be built up inside a star such as the Sun, as a result of nuclear transformations, was recognized by Öpik as a possible source of occasional mixing periods for the solar core. He used this as a model for solar variation on the longest known timescale (of the order of 100 Myr), which can be traced in the Ice Age record. Õpik's model of episodic mixing in the solar core has recently become of renewed interest as a possible explanation for the 'missing' solar neutrinos due to the hypothesis that the current flux is non-representative.
Less well-known was his insight into the turbulent mixing of gas flows in stellar convection zones. This mixing provides an important source of energy exchange in the upper layers of cool stars, where conditions are far from adiabatic. Õpik succeeded in parameterizing the mixing based on measurements of turbulent air flow near the ground, which he himself had made in Estonia as part of civil defense measures against chemical warfare. Ironically, his first application of his model of convection to the Sun was made when war had forced him to become a refugee; the work was eventually published in the Monthly Notices of the Society.
The possibility that the violent death of one star might serve to spawn a new generation of stars was a daring idea when Öpik first proposed it in 1953. The process of vindicating this insight by acquiring new astronomical data and other contributions lasted almost 30 years. Öpik appreciated that a more quiescent process of star formation might also be required to account for the appearance of new stars in dust clouds. In such cases, perhaps applicable to the formation of low-mass stars, he pointed out that the collection of a dust core may play a primary role in the agglomeration of a new star. Once again, this gives rise to the possibility of chemical non-uniformities in the interiors of low-mass stars, with possible consequences for neutrino generation.
The breadth of Öpik's grasp of matters astronomical was truly astounding It is difficult to understand how he managed to keep abreast of developments in so many different areas, so as to be able to return again and again to certain topics, perhaps after 10 years of silence, in order to provide incisive commentary. One of his methods centred around a system of summarising succinctly the contents of a paper in a notebook, where the material was grouped according to subject areas. His years as a refugee had taught him the value of a sheet of paper and his literature summary reflected this; the writing was small and every last square inch of the sheet was used. Thus many years of journal articles could be summarized in a notebook which could be carried in a pocket. One of us (DJM) has first-hand experience of the value of such a system; he still uses a notebook purchased in Armagh when he worked with Öpik in 1970. Each entry is made in writing which is as small as possible and, as a result, on any page one is confronted with a personalized summary of articles in a particular topic acquired over a 2-3 year period.
In 1950, by the initiative of Eric Lindsay and with the active support of Hermann Brück in Dublin, the Irish Astronomical Society began publication of the Irish Astronomical Journal with Ernst Öpik as editor. The proprietorship of the Journal changed after a hiatus from 1960 to 1962, during which time Öpik's 'News and Comments' were much missed; Õpik remained as chief editor until 1981 and he was still an associate editor at the time of his death. His formal retirement from Armagh Observatory took place in 1981. During those decades the Irish Astronomical Journal became 'Öpik's Journal'; in an economical form it acted as a repository for much of his thinking, astronomical, scientific and philosophical.
For 33 years at Armagh, with interludes at College Park, Öpik worked unremittingly on tasks of high attainment or, if necessary, at a humble level. In a Special Issue of the Irish Astronomical Journal, Volume 10, published in 1972 but intended to mark his 75th birthday in 1968, there were collected together testimonies from just a few of his friends and associates. In 80 pages, a remarkable variety of contributions was referenced, a total of nearly 300 published papers, with considerable support by way of personal reminiscence. The final section presented Öpik's fluency in musical performance and composition, and it seems likely that he could have made a successful career in music. In 1974, by a generous act, he presented Armagh Observatory with Dr. Lindsay's piano, where it gently reminds visitors of their cultural heritage.
Ernst Öpik, especially in later years, was often reckoned to be 'difficult,' a reputation partly produced because of his one-man running of 'his' journal. At meetings he would sometimes become a formidable critic either of scientific matter, of notation, or of presentation. At the age of 80 he had, perforce, to undertake the duties of Acting Director of Armagh Observatory, following Eric Lindsay's sudden death in 1974. This could have been difficult indeed for his colleagues, but it was not so. He was always tolerant of those whose actions were well-founded, even though he might have favored a different course. He was aware of his own shortcomings, even if he gave the impression of admitting no lapse. What he sought was firm and sound confrontation and challenge, and he did not always meet his match! Altogether he was, at his best, an entertaining personality. He could be depended on, when a suitably festive occasion came, to lighten any gathering with humour and pathos.
Ernst Öpik received many honours for his contributions to astronomy He was a Fellow of the Estonian Academy of Sciences from 1938, a Member of the Royal Irish Academy from 1954, and a Foreign Associate of the US National Academy of Sciences from 1975. He was also a Foreign Honorary Member of the American Academy of Arts and Sciences from 1977. He was conferred with Honorary Degrees of Doctor of Science by Queen's University, Belfast, in 1968 and by the University of Sheffield in 1977. He was a recipient of the J. Lawrence Smith Medal of the US National Academy of Sciences in 1960, the F.C. Leonard Medal of the International Meteoritical Society in 1968, one of six Gold Medals of the American Association for the Advancement of Science in 1974 in connection with the fourth centenary of Kepler's birth, the Gold Medal of the Royal Astronomical Society in 1975, and the Catherine Wolfe Bruce Gold Medal of the Astronomical Society of the Pacific in 1976, and the Louis Jacot Grand Prix, Pensée University, Paris, in 1978. He was elected a Fellow of the Society in 1949.
Ernst Öpik is survived by his second wife Alide, who shared his experiences of departure from their native country and resettlement in Ireland, and by one son and five daughters. These are Dr. Uno Öpik, Senior Lecturer in the Department of Applied Mathematics and Theoretical Physics at Queen's University, Belfast; Dr. Helgi Öpik, a Senior Lecturer in Botany at University College, Swansea; Dr. Tiiu Miller, a psychologist formerly at the University of Edinburgh; Elina Jaanits at the Estonian Academy of Sciences; Inna Strauts, retired; and Maija Konston of the US Library of Congress.
P.A. WAYMAN
D.J. MULLAN
Ernst Julius Öpik's obituary appeared in Journal of the Royal Astronomical Society 27:3 (1986), 508-512.