Interview with Allan R. Sandage

Sullivan: 00:00

19th May '76.  And perhaps we can hold a--

Sandage: 00:06

Sure.

Sullivan: 00:07

Can you just tell me about your early impressions at Mount Wilson and Palomar? In the 50s, you were a student there, I believe.

Sandage: 00:16

Yeah, I finished the degree at Caltech in 1952, and then I went right on with the staff at Carnegie.

Sullivan: 00:25

What's your recollection of how radio is coming and expecting details, if it all?

Sandage: 00:29

Well, no, it meant that almost the whole background of Baade and Minkowski’s time were-- the time had been devoted to their searches. So, Baade was doing the things like variable stars in M31 and IC 1613. But Minkowski on fairly poor positions in the 2C had started to blind photograph-- well, not really blind, but at the positions. And he became more and more discouraged that he couldn't get identifications. And there were peculiar galaxies all over the place. And it was thought that because the first three or four galaxies were peculiar that these would be possibilities. But then I think that by reading the summaries of his symposia that it was a fairly discouraging time in three different summaries, 1955, 1957. And in 1958, he really emphasized that the thing had reached the impasse.

Sullivan: 01:41

The other optical astronomers there, were they looking upon this as a good thing to do, or they were sort of saying, "This is a waste of telescope time?"

Sandage: 01:49

Well, everybody then and everybody now is really independent. So, there's no group project. There's no observatory project. And everybody was given about 30 nights a year, and he could do whatever he pleased. So, I guess, I don't know. There was no unified group action or team action like in Ryle’s group or Manchester. And the optical astronomers were really individual.

Sullivan: 02:16

I see. Do you have any idea what it was in the personalities of Baade and Minkowski that made them pick up this radio astronomy ball, so to speak, and not other astronomers there?

Sandage: 02:30

Well, really they were the only senior people around. Hubble had died in 1953. And the young people, well there were no young people, there was a gap of about 25 years between the people on the staff and the first of the new crop. I was the first of the new crop in 1952. So, people tended not to interfere with anybody else's work. You had a general idea what other people were doing. But the only direct people were Baade, Minkowski and Humason. And Humason was still heavily involved in trying to get redshifts in the conventional way. And Baade is heavily involved in these studies of the stellar content of the Local Group. And Minkowski, he took that over as his principal activity, and I think because of the stimulus and the opportunity that was being created by the Sky Survey plates of which he had sole privilege. So, it was an opportunity either not to do anything. And when the prints came out to have the flood or really try to make the identifications, it just naturally was him.

Sullivan: 03:41

So, you're implying then that if a young person like yourself, for instance, had wanted to work in radio sources, it would have been difficult because that niche had been taken by senior people?

Sandage: 03:51

No, I don't really mean that because everyone was very friendly. But it just naturally felt that this work was being done. And I'm sure that if I had nothing else to do and was just turned on by it and went to Minkowski that it would have been just fine. He was very approachable guy. He was the most approachable, I think, of the three. I had been Hubble's assistant but found him more formal than Baade who was my thesis advisor. But still Minkowski was more a father figure.

Sullivan: 04:28

I see. So just mentioning Hubble's name, I know nothing whatsoever what he thought about this whole radio astronomy thing. Do you have any recollection?

Sandage: 04:36

No, I don't really either. He was concerned very much with the extension of the redshift diagram and all of Humason’s attempts to get large redshifts and also was trying to get the photographs organized for an atlas that he wanted to publish. But the 200 inch Telescope has been in operation only since 1949. So, taking the direct photographs and seeing the structural forms, he still was very interested in the classification problem and even in galaxy counts to faint limits. So, I think he was really, really completely occupied in the four years that he had with beginning the operations [inaudible].

Sullivan: 05:24

Yeah. Well, can you detail when you first crossed into radio astronomy territory, so to speak?

Sandage: 05:31

When essentially Minkowski went out, this left a pretty great vacuum in people that were taking direct plates. Humason took plates for the catalog in the early days. Baade was more or less out of it, and so somebody had to do it. And Tom Matthews then was the liaison with a lot of people on the outside of radio astronomy. So, he had produced lists of very high surface brightness objects, where the diameters were gotten by Jodrell Bank and the positions around the world. He acted as kind of a librarian or catalog of these things. And he suggested that we begin an identification program.

Sullivan: 06:24

What time is it now?

Sandage: 06:25

This was 1959. He would then provide updated radio positions that I guess the 3C or 3CR had either not come out or were being improved upon.

Sullivan: 06:40

Right.

Sandage: 06:41

And he--

Sullivan: 06:42

He started with this process then?

Sandage: 06:44

Yeah. And there were students at Caltech, for example, Richard Read, Richard may not be his first name, I guess it is. Who had begun the next phase in getting positions. And he got declinations good to maybe five seconds of arc, which was an incredible improvement over the 3CR. And then maybe even the adjudant business at Malvern had begun. But anyway, Tom Matthews had privy to information that was not published.

Sullivan: 07:13

[inaudible] on this.

Sandage: 07:15

That's right. And it was really his list of high surface brightness objects. And that list still exists. And it's interesting now to see what objects are on that list. All the quasars are on that list. So, he produced lists, and I would take photographs, and I turned the photographs over to him. And it was really he that made the optical identification of the stellar objects.

Sullivan: 07:39

Right. I had talked to him, so I had this [inaudible].

Sandage: 07:42

Yeah. I don't know what he tells you. That's really the way he sees it, but I think he was crucial in this whole business of getting radio position. He didn't get the radio positions himself, in general, but he was the central clearing and did begin the program of the high surface brightness sources.

Sullivan: 08:06

Are you saying that you did not get involved in the interpretation of these? Then you simply took the--

Sandage: 08:11

I didn't make the optical measurements for the position. For example, in 3C48, I turned the plates over to him and he said, "Well, okay. In the error box that exists from the radio position, there is this object. That was October 1960. And the next run then we did follow up on that object, spectroscopy, and it was the strangest spectra that I ever seen. And I took the spectrometer off and did photometry and it was the strangest UBV. But Tom really had pointed out the object measure and he did the same thing in 287 and 196.

Sullivan: 08:49

What did you make of these strange spectra?

Sandage: 08:51

Well, not being a spectroscopist, I didn't make anything. I measured the wavelengths. And clearly at that time no star could have a redshift. No stellar like could have a redshift. Here's the case that the whole tradition of the past was so weighty that anyone that had been associated with that tradition just could not believe that these things could be redshifted.

Sullivan: 09:17

Very highly redshift, you mean.

Sandage: 09:19

Well, have anything to do with galaxies or cosmological redshifts.

Sullivan: 09:26

[Redshift?] was also from an old tradition. Certainly, in line with--

Sandage: 09:29

That's right. But these spectra lay around for three years, from October 1960 until 1963. And Schmidt made the identification, 3C273, on a plate that had been taken in this program with Matthews. I took the plate. Tom told me where to take the plate. I didn't look at the plate after it got out of the hypo. I turned it over to Tom. Tom turned it over to Schmidt. And Schmidt made the identification. And then it was so bright that he could get higher dispersion spectra.

Sullivan: 10:03

You're saying there was a three-year gap in there between them.

Sandage: 10:05

I'm not sure when the direct plate 3C273 was taken, though. I can check the records too. But the breakthrough of the interpretation of the spectrum did not occur until ‘63. But the spectra 3C48 existed since October 1960 and Greenstein had interpreted it in terms of oxygen V or some sort. I went to Bowen, who was an expert, and said, "I cannot interpret the spectrum. Can we talk it over?" So, all the lines are measured and relative intensities. And he looked at the stuff for a couple of days and he said, I can't interpret it, but Greenstein has recently been looking into the high excitation lines of O stars. Let's take the spectrum down to him. So, at the end of an observatory committee meeting, we turned to-- Or Bowen said, "Can you stay for a little bit?" And then both Dr. Bowen and I showed the spectrogram to Greenstein and he said, "Do you mind if I begin to work on this?" And then he took a few more spectra and Münch took a few more spectra, and then it was easy after Schmidt got 3C273 for them just to redshift the 3C48.

Sullivan: 11:27

Are there any other things that you can think of that you might like to comment from the optical side, how you've seen radios developed in the 50s and early 60s?

Sandage: 11:37

[laughter] I think that we viewed the tremendous change of direction of the program or been laid out for the 200-Inch in a very unhappy life. Unhappy, since one had set one’s sights at a particular problem, namely the evolution of galaxies and the extension of the Hubble diagram with galaxies.

Sullivan: 12:17

Is that program written down anywhere?

Sandage: 12:19

Yes, there's a paper by Hubble which was at the American Philosophical Society meeting in 1946 called “A Program for Cosmological Investigations with the 200-Inch” and primary at that time was the question of the distance scale. So, in 1949 or 1950 the question of the distance scale still came up and we knew what had to be done. Cepheids had to be found outside the Local Group. Just what's now happened in the last-- It's all been finished.

Sullivan: 12:55

Do you think it was delayed essentially?

Sandage: 12:57

Yes, it was delayed. And at the time it seemed to me that although the physics was interesting, fascinating, and I was primarily an astronomer. Am primarily astronomer, not a physicist. So, the geometry of space, the counts of galaxies, the isotropy of the expansion, the distance scale, the time scale, the inverse Hubble time, even at that time the question of the deceleration was understood. Hubble's book in 1938 discussed deceleration his observational approach to cosmology. He had the sign wrong. He said if it curves up, it's decelerating, if it curves down, it's accelerating. But at least the principle that you're looking back in time when you look out in space was clearly described.

Sullivan: 13:53

If you had your druthers…

Sandage: 13:54

It upset the conservative way of progressing step by step and of course the great advances are done that way. And clearly the excitement opened up new realms. I'm a more tidier-upper than an innovator.

Sullivan: 14:21

You need both.

Sandage: 14:22

But now the quasars, it seems to me, themselves offer the most important proof besides the three degree radiation for cosmology and that's their limit of redshift. If that can be shown to be real, that the quasars stop at some finite redshift, say like four or it doesn't matter what the number is. But if there's a wall and limit, that means you're looking back so far in time that you're seeing matter as it first turned on and you can't see any further back in time.

Sullivan: 14:55

Because as you said you're looking at the end.

Sandage: 14:57

Yeah, in a strange way, yeah. I should have not used that. I said it and I wrote some papers on it and if that can be shown, it really will be important. More important than this more conservative approach.

Sullivan: 15:14

Well, one never knows. Thank you very much.  That ends the interview with Allan Sandage on 19th May 1976.