Interview with German G. Getmantsev

German G. Getmantsev, 1926-1980. Interviewed 1 August 1978 at the URSI Meeting in Helsinki, length of interview: 40 minutes.

Papers of Woodruff T. Sullivan III

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Oral History

Sullivan, Woodruff T., III

Getmantsev, German G.

Audio cassette tape

40 minutes

1978-08-01

1950s work on synchrotron theory of galactic background, radio halo, claimed detection of deuterium line, polarization of galactic background, cosmic ray lifetimes, interstellar magnetic fields, etc.

This interview was conducted as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009). In preparing Sullivan interviews for web publication, the NRAO/AUI Archives has made a concerted effort to obtain release forms from interviewees or from their heirs or next of kin. In the case of this interview, we have been unable to find anyone to sign a release. In accordance with our open access policy, we are posting the interview. If you suspect alleged copyright infringement on our site, please email archivist @ nrao.edu. Upon request, we will remove material from public view while we address a rights issue. Please contact us if you are able to supply any contact information for the interviewee or his heirs/next of kin.

We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web. Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.

Working Files Series

Individuals Unit

Originally transcribed as typescript only by Pamela M. Jernegan (1979), retyped to digitize by Sheila Marks (2021).

Tape 108B

Woody Sullivan: This is talking with Professor G.G. Getmansev at Helsinki on 1 August 78. Now can you tell me about this first paper that you were involved with Ginzburg, in which you talked about lunar occultations. They had never been done before [tape problem]…..it would be a good technique?

German Getmantsev: I think it was the first publication, but we had no technique to check it, experimentally.

WS: Right.

GG: We had no large telescope to see these sources, but we tried to observe Taurus A with a simple antenna, but had no results at that time.

WS: Did you try that already in 1950, you tried to do –

GG: Sometime later, one or two years later.

WS: One or two years later, right.

GG: We didn’t start with the simple antenna right from simple arrays connected together but we had no large antenna at that time – we had no good results. We had no experimental results from this.

WS: Right. But what were the theoretical problems? What were the main problems as you considered this? Was it quite clear that you could do this or –

GG: On this subject?

WS: Yes, on that subject.

GG: I think that the more difficult problem is, the problem of, to check the moon, as a plane screen. When the line of sight because there is a reflection from the moon surface, it’s very difficult to choose the place the plane screen is right age.

WS: Right, so you thought the reflection effect might. Might cover up the diffraction effects.

GG: Yes, but this shows that it is possible with very small error, 1 or 2%. Now we know that this was quite correct because there is an exact solution from the diffraction of from the sphere (?), we calculate exactly this result.

WS: Were you worried about the irregularities on the moon surface?

GG: Yes. I checked irregularities on the moon surface and showed that there are small effects from the irregularities because the first fresnel zone is approximately larger than the middle irregularities of the moon. But also much of these effects may be negligible.

WS: I see. Now you say this is in your dissertation?

GG: Yes, the main result is in my dissertation, what was published.

WS: What year was this?

GG: My dissertation was in 1952.

WS: And what university was it?

GG: Gorki University.

WS: At Gorki? Okay. And Professor Ginzburg was your advisor?

GG: Yes, my advisor.

WS: Now, then you became interested apparently in work on the galactic background, and what might be causing the galactic background? Can you tell me about that work?

GG: Yes. We have worked on the galactic background, we tried to distinguish the galactic background and on the whole radiation background. On the earth with the help of a simple antenna array, but this is a very difficult problem, so we drew some diagrams, frequency, no, not frequency, in galactic coordinates and effective temperature.

WS: Right, a map of the sky.

GG: Yes, a map of the sky.

WS: And trying to distinguish what were you?

GG: We were trying to distinguish extra-galactic components, yes. Now it is the question of the existence of a halo in the galaxy.

WS: Whether there was a halo or not.

GG: That’s a very difficult question.

WS: Right. Is it correct to say that Shklovskii was the first one to suggest that, or is that not correct?

GG: The point of view of Professor Shklovskii changed very rapidly. You can see before of his point of view (laugh).

WS: I see. But now you and Ginzburg thought that there was definitely a halo in the galaxy?

GG: I think now that from our measurements and theoretical investigations that there is an observable halo. But I think that it’s very difficult to check that correctly. Because there are very large inhomogeneities.

WS: Spurs. Right, right.

GG: Yes, of course. And it might be a mistake.

WS: Right. Well, so you think that now in 1978 you think that, but what did you think then? That’s what I am more interested in.

GG: I have no answer about this question, but if we show simple measurements about this with antenna arrays not so small widths, we shall show that the large galaxy exists, because we tried to grow simple effective temperature (??) and galactic latitude.

WS: Okay, temperature versus galactic latitude.

GG: And we shall try to draw the (??) models, some elliptical, -elliptical component and fatter elliptical component.

WS: Right.

GG: And spherical background. And we tried to vary the apparatus of these three elliptical components. The better coincidence between the theoretical and experimental results in this case, is that the comparable large halo exists.

WS: And so you felt probably…..

GG: But it might be mistakes (laugh).

WS: Right. Ok, but of course the trouble was then – where did the halo come from? And also once you believed that the radiation was due to synchrotron radiation, then you had to understand where the electrons came from and so forth. Now can you tell me about - where did the suggestion for the synchrotron radiation come from - who?

GG: Oh, yes. I think that my work was, I think, ten or twelve years ago about this subject. I think that the electron component, of course, of cosmic rays. I don’t think now that it’s from supernova remnants. I don’t believe in this, because there is a difference between the magnetic spectrum of supernova and from the frequency spectrum of background radiation. If we check synchrotron losses for electrons in galaxy, the only thing losses is, comparable losses, because the frequency spectrum of the discrete sources temperature rose so rapidly.

WS: It’s steeper.

GG: Steeper, yes. So steeper than not possible, I think.

WS: But I am more interested in what you thought twenty-five years ago rather than what you think now.

Tape 109A
Date: 1 August 1978

WS: So what were you thinking then, in the early fifties, about this problem?

GG: I think that the main part of the electron component must be of relict origin, and a small part near the galaxy plane may be from supernova remnants. I think that the diffusion of cosmic rays from the galactic plane from north or south is so slowly that the time of life of cosmic ray electrons; they can’t penetrate from the galactic plane to the . . .

WS: They cannot penetrate, you say?

GG: They can not penetrate because there is a reflection of cosmic rays from the magnetic field lines. There are very small irregularities. They reflected, they moved in the other way.

WS: So you don’t think the electrons could get to the halo?

GG: Oh, yes.

WS: So they could not get to the halo right now. Who was the one who made the suggestion for the cosmic ray electrons causing the background radiation? Did you first make the suggestion, or was it Ginzburg, or both of you? Whose idea was it? That’s what I am trying to find out.

GG: Oh, about the origin of cosmic ray radio emission.

WS: Right.

GG: It was just work in Physical Review of Professor Alfven and Dr Herleson.

WS: Herlofson.

GG: Yes, Herlofson, right. But Dr. Herlofson made a mistake in the intensity of cosmic radio emission. Professor Ginzburg checked more correctly, but I checked the spectrum of cosmic ray radio emission.

WS: Right.

GG: And connected it with energetic spectrum of cosmic radio emission. I drew a (??) connected the energetic spectrum and the frequency spectrum of non-thermal radio emission. This law is intensity equals coefficient g, multiplied by frequency, one minus gamma, divided by 2.

WS: Right.

GG: But I checked in my first work, for instance in the Doklady of the Russian Academy of Science reports coefficient of E; I checked not quite correctly. Dr. Ginzburg said to me about this “I checked it quite correctly, very rapidly, during two hours” [laughter], And after this, it was published by Dr. Ginzburg and I. Dr. Ginzburg drew this formula in a report of Academy of Science and indicated in this article that my previous publication, was a mistake in this coefficient.

WS: Right. Now, at that time were you quite certain that the galactic background was due to the synchrotron mechanism, or was it just a suggestion that it might be due to it? How certain were you that this was probably the mechanism? How sure were you that this was the right explanation, or was it just another suggestion of possible cause?

GG: Dr. Ginzburg told me that I could investigate non-cosmic radio emission and that I must investigate synchrotron radiation. I checked the connection between energetic spectrum, but Dr. Ginzburg did not tell me about this. But when I investigated this connection, I believe that it is quite correct. Because the coincidence between the experimental results and theoretical results was quite good and synchrotron losses and (?) losses is influenced in such manner in the energetic spectrum that they have a low which coincides with experimental results.

WS: Right. With the steep spectrum of the background.

GG: Yes, steep spectrum is quite correct.

WS: But cosmic ray electrons, however, had not ever been observed, at that time, right?

GG: Yes, yes, yes.

WS: But you felt for sure that they must exist, along with the protons? Because it was not until 1960 that the first detection of cosmic ray electrons was made.

GG: Yes. We had no experiments.

WS: Right, there were no experiments, but you felt that they must exist, the electrons must exist along with the protons in the cosmic rays?

GG: Yes, protons can’t be responsible for the non-thermal cosmic radio emission because there is no possibility to explain . . .

WS: Right.

GG: The mass is too large from the protons and emission is too small from the protons.

WS: But the electrons, though, had never been observed.

GG: Yes, of course, but . . .

WS: But you felt they must be there.

GG: We felt that they might exist in very small amounts; they are necessary to explain. The radio emission they might be absorbed in solar system. It’s very difficult to speak about electrons components in the Galaxy, on the base of their existence in the solar system.

WS: Now there were several papers in the early 1950s by Soviet scientists, including yourself, about the synchrotron mechanism and so forth, and yet it seems to me that in the Western countries, that people were not thinking about synchrotron radiation as much as in the Soviet Union. Do you have any ideas why this was, why there was this reluctance?

GG: I published my first result about the connection between the spectral index alpha and the energetic index gamma, alpha is equal to one minus gamma divided by two, in 1950 –

WS: Right, 1951 actually I have it. [actually1952, 1952DoSSR..83..557G]

GG: I made this result by numerical calculations, firstly. And I have seen that this law is quite correct. (??) After this, I did it more formally. I gave the formula for synchrotron radiation –

WS: Analytical method?

GG: Yes, yes. But I made a mistake in the calculation of the coefficient of proportionality in this formula.

WS: But do you have any idea why it was not until the late 1950s that the idea of synchrotron radiation was not generally accepted in the Western countries – why did it have such a slow acceptance amongst Western astronomers? Do you have any thoughts about that?

GG: My thought about this only a paper in Physical Review by Alfven and Herlofson and Dr. Kiepenheuer.

WS: Okay.

GG: Professor Shklovskii was my opponent when I –

WS: When you defended your dissertation?

GG: Yes, dissertation. He spoke that this was a mistake, synchrotron radio emission does not exist.

WS: I see.

GG: He spoke that it was radio stars connected with background radiation, a large amount of radio stars (??) spherical components.

WS: Right, right.

GG: But two months later he wrote an article where he talked about this quite correct mechanism and used it in the explanation of the non-thermal radio emission of discrete sources.

WS: Right, I know the paper you mean by Shklovskii. I know it.

GG: Astronomical Journal [Astronomicheskii Zhurnal (1953) 30, 15]

WS: Right. But now there’s a paper that you have in the Gorki Univ., I’m not sure if this is Yuchenski or something of Gorki Univ., 1954.

GG: With (name?)

WS: And here you were looking at the space distribution of the sources of the background radiation, so were you thinking that the cosmic rays came from discrete sources – what kind of sources were you thinking of?

GG: What kind of sources? I think that they might be supernova remnants.

WS: So they were not in the halo, they were in the plane.

GG: In the plane, but in the halo also.

WS: Oh, in the halo also. But we don’t see supernova remnants in the halo though.

GG: Supernova remnants is in the plane component.

WS: Right.

GG: The cosmic rays which penetrate along the magnetic line, and they may travel –

WS: Oh, I see. So the electrons go away from the plane. And did it look like the lifetimes of the electrons worked out all right so that they could radiate far above the galactic plane?

GG: Oh, this is a very difficult question because it is a question closely connected with the time of diffusion and the character of diffusion is a very difficult question. Because if the diffusion is a simple diffusion along the line of force –

WS: A very complicated path.

GG: But (??) reflection of cosmic rays from the shock waves –

WS: Right, from discontinuities –

GG: They move another term. The time of diffusion must be very large. And lifetime of electrons is too small to penetrate in the halo.

WS: Okay. Now you had a paper with Ginzburg in 1952 in Doklady explaining solar bursts by synchrotron radiation, also.

GG: Yes, yes.

WS: Can you tell me about that?

GG: Yes, it is very interesting for us to explain some solar events with the help of synchrotron radiation because we have seen that it is a very plausible conception connected with cosmic background radiation. You know that today there is synchrotron radiation in some events, but the main thing is mainly connected with it; plasma resonance, synchrotron mechanism, harmonics.

WS: But don’t worry about today so much, what were you thinking then? Why did it look like a good idea in 1952?

GG: I think now that this idea in 1952 and later stimulate the work in this region; Prof. Zheleznyakov made it very many results in this region.

WS: Did you say, what was his name?

GG: Zheleznyakov.

WS: Right.

GG: But I don’t think that this is the main mechanism of the non-thermal observation, plasma mechanism.

WS: I think we should go back now.

[Continuing now after a break]

WS: tell me about the deuterium line.

GG: Yes, I don’t know if our result about the deuterium line is correct or not, because after our publication of (?) a strong shift resulted and is not quite correct because they used 64-meter antenna in Parkes and observed the deuterium line in absorption with the help of the Cassiopeia A radiation. They report that, about the absence of a deuterium in the galaxy; if deuterium exists, the amount of deuterium is one-thousandth in comparison with that amount that we measured. Because of this I think that we made a mistake.

WS: What exactly was your experiment? Can you describe to me what were the observations?

GG: Oh, we used in our observations a 5- meter antenna with some simple dipole system in the focus. And simple receivers with noise factor, but not cool of course because they’re very old measurements. And we delayed the frequency during each session and repeated many times.

WS: So you had one channel?

GG: One channel, one antenna.

WS: And you moved in frequency.

GG: One channel moved, yes, it changed frequency. And after this we averaged all our results during the three or four months and the total number of observations during two or three weeks total number of observations was maybe forty or sixty; we had some results that the deuterium line exists. Additional averaging during time did not change this result.

WS: So it looked pretty good, then?

GG: Yes. But after the Australian publication, we think that we made a mistake and we show that we observe non-thermal cosmic background radio emission polarization component, which maybe rotates with changing frequency and can give us such an effect as a deuterium line. Because we observed over a not very large frequency interval we can see only one oscillation. Since we moved frequency there was, but (?)

WS: So you think it might be polarization effect?

GG: Oh, really, yes.

WS: But you’re not sure, of course.

GG: I think that I should repeat in the near future, during one or two years with the help of a 22-meter parabolic antenna in Serpukhev or Crimean antenna and to try to repeat with a more plausible technique, a more modern technique.

WS: Right. Now let me just make sure I understand the effect you’re talking about. It would be due to the polarization of the galactic background varying with frequency?

GG: We change frequency 100 or 150 kilocycles. It is maybe due to Faraday effect (?) components from the Sagitarrius A (?) galaxy syndrome (?) rotates and gives such an effect as a deuterium line.

WS: I see. What was your comparison? Were you taking off spectra also? Or were you frequency switching?

GG: Yes, yes. Frequency switched slowly.

WS: But I mean were you frequency switching fast?

GG: No.

WS: Or were you beam switching?

GG: Oh, no, frequency switched too fast for reception of this signal.

WS: Right. And then switching –

GG: – slow (?) for detection of line.

WS: Okay.

GG: It was a general comparison.

WS: Right. Can you tell me in the late 1950s now your ideas changed –

GG: 19 – ?

WS: Well, in 1957-58, you were writing about the galactic halo and the cosmic rays and so forth, did you still think by that time that the electrons were probably coming from supernova remnants – that that was probably the source of the electrons?

GG: It is a very difficult question. If the observing halo exists I think there is no possibility to explain cosmic rays and halo as cosmic electrons and cosmic rays from supernova remnants. But if the observer (?) not exists and we can see only a flat radio component, it is not necessary to propose that they can have the cosmic rays of relict origin or extra-galactic origin – it may be explained from the supernova remnants.

WS: Now when you say relict origin, do you mean from the primeval universe?

GG: Yes.

WS: From the beginning, it’s always been there.

GG: Yes, yes, from the explosion of our center of galaxy in the case of cataclysm.

WS: Okay, now what about the business of polarization of the galactic background? On the synchrotron theory, there should be some polarization, and did you ever do any experiments to try to find the polarization in the background?

GG: We talk about the polarizations with Prof. Razin in 19-, I forget exactly, ’43 or ’44.

WS: ’43? During World War II?

GG: We published a theoretical article where we checked the percent of polarization which we might expect.

WS: This would be 1953.

GG: 1953 or 1954.

WS: Okay, okay.

GG: We published this in Astronomical Journal [Astronomicheskii Zhurnal?] at I forgot exactly when Dr. Razin observed firstly the polarization; I think it was in 1955 or 1956.

WS: And was this the expected amount? Were there any surprises in what he found or was it about as expected?

GG: Yes, yes, we have a model for checking polarization that our galaxy is full of cosmic rays, irregularities of magnetic fields, this diffusion of cosmic rays in those irregularities. We checked results polarization components as the sum of many independent sources, (?) line of polarization. There is a simple formula for the expression, percentage of polarization must be one or three percent irregularities – not too large, not too small. Dr. Razin measured much more percent of polarization, but we know today that there are some regions of the sky where that percent of polarization is indeed more large than in our model.

WS: You had a paper in the Astronomical Journal [Astronomicheskii Zhurnal] in 1959 about what you called magnetized clouds or something like this, meaning the –

GG: Oh, yes, yes, yes.

WS: What did you mean by a magnetized cloud?

GG: About cosmic (ray?) losses –

WS: But you were trying to find out about the innomogeneities in the galactic background and trying to get the size of these magnetized clouds, and you said that they were smaller than 75 parsecs in size.

GG: Maybe a short communication.

WS: In the Astronomical Journal [Astronomicheskii Zhurnal] in 1959. Don’t remember that one?

GG: I forgot about this. I remember where I checked losses of energy of temperature rise in cosmic ray particles during movement of a galactic magnetic field. This very plausible mechanism to the interstellar medium. I talked about not so energetic cosmic ray electrons because relativistic ray electrons energy not too large, but the cosmic ray energies much more than 10 minus 7, 10 minus 8 is plausible for it to be not interstellar medium.

WS: Okay. Well, that pretty much comes to the end of these papers. But let me ask you a general question, what would you say are the main contributions of the Soviet Union to radio astronomy before 1960?

GG: Before 1960? The theory of nature of the cosmic non-thermal radio emission, the synchrotron mechanism, I think the work of first of all, Prof. Shklovskii checked (?) in connection with the radiation of discrete sources.

WS: Of the Crab Nebula?

GG: The Crab Nebular in particular. Yes. I think also that measurements of (?) with the help of Crab Nebula.

WS: Ah, yes, solar occultation.

GG: Solar occultation’s of Crab Nebula and other sources and measurements of the solar wind irregularities. This was not pure radio astronomy.

WS: Right, right.

GG: But it is related. Yes. I think that the discovery of polarization by Prof. Razin was a very interesting result also.

WS: Okay, that’s good. Another question would be, it seems to me that the theory was stronger than the experimental work in the Soviet Union in the forties and fifties. Do you agree with that?

GG: Yes, I think that the theory was much better than experimental work in radio astronomy.

WS: Right. Why is that?

GG: We have no good instruments.

WS: But why is that? Has there been a decision made somewhere?

GG: Well, now we have RATAN 600

WS: Now, but I’m talking about the 1950s. In the 1950s, was there a decision made that Soviet radio astronomy would concentrate on theory and not on instruments? What do you think was the reason for this?

GG: I think that Soviet radio astronomers were not specialists, only in theory. But if we have before good instruments, we can do good experimental works. We believe that in the future we shall have good instruments; but it’s very difficult to do good works with a small dish.

WS: Oh, that’s for sure.

GG: But now we –

WS: That ends the interview with Getmantsev on 1 August 78.