Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
:: : ~.*. ~ ~ ~ ~ :: : ~ ~ ::: ~:~ i: it: ~ :: ~ *I \ : :. :~:~:~:~:: :: : ~:~:~ ~ ~~ ~~ ~~ ~ ~~: ~ ~~ ~ i: ::: it.:: ~~:~ ~~:~:::~:~:: ::: L-.: . ~~ ::: i: :: , .~ I:: ~~ ~ ~ ~ ~~ ':: ~ ~ ".~,,'~' '2~, " it''.: :.:.:.:.:: _ :.: :: ' : :~::''~:~::'~:~-~:~.~':- :.:~_' i',: ~ ~ ~ : ~ : : :: :: :: : :::: '~ :: ~~' :: '~ ~. ~ ~~"~:~ i: ~~ ~~ '.~ ''if : ~~ ~ ~ '"" : :":~: ::::~:: E' ~q~~ '::': `. bed i:: ::: Do. _ : :: o - {~01 - i., ~ ':'' ~ O Cal o ho o PA
RUDOLPH LEO BERNHARD MINKOWSKI May 28, 1895-January 4, 1976 BY DONALD E. OSTERBROCK RUDOLPH MINKOWSK! was born in Germany near the end of the last century and died in California during the final quarter of this century. He was trained as a laboratory physicist, but worked most of his life as an observational astronomer. Using the largest optical telescopes in the world, he made important contributions to nearly every branch of nebular and extragalactic astronomy, but his most important contribution of all was to the identification and interpretation of cosmic radio sources. His monument is the National Geographic Society-Palomar Observatory Sky Survey. He guided, encouragecl, and counselecl a generation of radio ant] optical astronomers. Minkowski was born in Strassburg, then part of Germany, on May 2S, TS95. His grandfather hac} hurriedly moved his family to Konigsberg from their native Russia less than twenty-five years before to escape the policy of anti-Semitic persecution adopted by the Czar's government. Rudolph's father Oskar, educates! in Konigsberg, became a physician, and at the time of Ruclolph's birth he was a welI-known pathologist on the Strassburg University medical faculty. His research had played a very important part in understanding the causes of diabetes. Rudolph's ogler uncle, Max, took over the Minkowski family business in Konigsberg, while his 271
272 BIOGRAPHICAL MEMOIRS younger uncle, Hermann, became a worict-famous professor of mathematics, first at Zurich, then in Gottingen. He made many very important discoveries and is perhaps best known for his Plea of the space-time continuum, which provides the simplest ant! best mathematical basis for handing the special theory of relativity. As his father mover! up in the academic hierarchy, Rudolph was educated in Gymnasia at Cologne, Greifswald, and Breslau and then entered the University of Breslau, where he studied physics and earner! his Ph.D. in 1921. He hacI served in the German army during WorIc! War I. At the university he specialized in optics and spectroscopy, and his thesis, done uncler the supervision of Rudolf Ladenburg, was on the Na ~ D lines and the information on the physical and chemical properties of sodium that could be drawn from them. After receiving his Ph.D., Minkowski continued to work briefly at Breslau, with Ladenburg, and then at Gottingen, with James Franck and Max Born. He then mover! on to Hamburg, where he started as an assistant at the Physikalisches Staatsinstitut in 1922; he became a Privat- Dozent in 1926, and he was appointed to a professorship in ~ 93 ~ . Minkowski's research at Hamburg was at first centered on atomic physics and spectral lines. He workoc! in close association with a vigorous group of physicists, including, among others, Albrecht UnsoIct and Wolfgang PauTi. Minkowski, however, had been interested in astronomy from childhood; at Hamburg he soon met Walter Baade, then a young assistant to Max Wolf at the Hamburg Stern- warte. Although he continued his spectroscopic and ex- perimental quantum mechanical research at Hamburg, Minkowski's field of specialization shifted increasingly to astrophysics, and he published his first astronomical paper with Baacle, F. Goos, and P. P. Koch in 1933. It concerned the interferometric measurements of the profiles of emission
RUDOLPH LEO BERNHARD MINKOWSKI 273 lines in the spectrum of the Orion nebula, a subject to which Minkowski's training ant] experience enabled him to make important technical contributions. By this time Adolf Hitler had come to power in Germany. Minkowski had married Luise David in Leipzig on August 23, 1926. Her father, Alfons David, was a judge who had been appointed to the Supreme Court of Germany in 1917. Hitler became Reichschancellor in 1933, and one of his govern- ment's first actions was to order the universities to get rid of almost every "full-blooded Jew" who held a teaching position. Justice David was forced off the high court by the Nazis because he was a Jew. Although Minkowski and his parents were baptized Christians, their family was historically Jewish. Baade, who earlier had spent a year in the United States as a Carnegie International fellow, had emigrated to take a posi- tion on the staff of the Mount Wilson Observatory in Pasa- dena in 1931. He urged his friend to join him there and in 1935, the year in which Hitler proclaimed his so-called "Law for the Protection of German BloocT and Honor," Minkowski, with his wife and their children Eva and Herman, left his homeland. At first he had only a research assistantship at Mount Wilson; in addition he gave a series of lectures on atomic spectra to the staff members, for which they con- tributecl a little cash to help him get established in America. Before the year was out he hacI been appointed to a regular position and was on his way. Under Director Walter Adams, the Mount Wilson staff used the 60-inch and ~ 00-inch reflectors, the latter the largest telescope then in existence, in a highly compartmentalized observational research program. One staff member, Paul Merrill, studied the spectra of M giants, supergiants, and long-periocl variables; another, Roscoe Sanforcl, studiecl the spectra of carbon stars; and a third, Alfrec! Joy, studied the spectra of variable stars that were not long-period variables
274 BIOGRAPHICAL MEMOIRS or carbon stars. Edwin Hubble heacled the attack on the cosmological problem of the expansion of the universe, con- centrating his observational work on the determination of the distances of the galaxies, while Milton Humason took their spectra to measure the redshifts. Baade worked on the stellar content and general properties of star clusters and galaxies. Except for Merrill, they all tended to think in astronomical, rather than physical, terms. Minkowski, with his wide knowledge of spectroscopy, atomic physics, and applied quantum mechanics, became involvect in all these studies, but specialized in work on gas- eous nebulae and related objects. He began by using the fast, low-dispersion spectrographs designed for Humason's mea- surements of galaxies to take spectra of faint supernovae, the highly luminous explocling stars that flare up to a brightness comparable to an entire galaxy, as they were discovered in surveys by Fritz Zwicky, Baacle, anc! others. Minkowski cIassi- fied the emission-line spectra of supernovae ancT studier] their clevelopment in time. The combination of his spectral classification with Baacle's light curves led to the recognition that there are two different types of these objects and that in many cases a supernova's absolute magnitude, ancT hence the distance to the galaxy in which it occurs, can be estimated from a single spectrogram. Minkowski obtained many spectra of various regions in the Crab nebula, which hacl recently been identifiec! by Jan Oort and Nicholas Mayall as the remnant of a supernova that occurrecT in our Galaxy in A.D. 1054. He confirmed Mayall's result, that the spectra of the filaments of the Crab nebula in(licatecl a high velocity of expansion, and that the amor- phous region hac! a purely continuous spectrum. Minkowski measured this continuum and correctly pointed out that it had no Balmer discontinuity, making it impossible to inter- pret as a thermal recombination spectrum. He did not realize
RUDOLPH LEO BERNHARD MINKOWSK! 275 at that time that the continuum was in fact nonthermal synchrotron emission; this was preclicted much later by I. S. Shklovsky after the Crab nebula had been identified as a radio source, and it was observationally confirmed by optical polarization measured by V. A. Dombrovsky and M. A. Vashakidze and also by Oort and T. WahIraven. Minkowski, from his spectra of the two stars identified by Baade as the possible supernova remnants because of their proximity to the center of expansion of the nebula, picked out the correct onenearly thirty years later it became the first optically identified pulsar. Through the years Minkowski obtained spectra of the gaseous remnants of several other galactic supernovae. In particular, his measured radial velocities in the Cygnus loop and other roughly circular remnants have been widely used in theoretical discussions of the ages, dis- tances, and energy outputs of these objects. Planetary nebulae were another subject studied by Minkowski from his first days at Mount Wilson until years after his retirement. in his early work, he obtained spectro- photometric measurements of many low-surface-brightness planetaries that had been too faint for previous investiga- tions, and he proved that their spectra were quite similar in overall pattern to the brighter objects. At Mount Wilson he organized a survey to fins! new planetary nebulae with an objective prism mounted on the 10-inch Cooke wicle-angle camera. He used the 60-inch and 100-inch telescopes to take slit spectrograms of suspected planetaries turned up by this survey, objects with bright Ha and weak or nonexistent con- tinua, and in this way more than doubled the number of known planetary nebulae. Minkowski then arranged for Karl G. Henize to take the same camera to South Africa and com- plete the planetary nebula survey in the southern Milky Way as part of his University of Michigan Ph.D. thesis. Minkowski was engaged in a long program, originally in
276 BIOGRAPHICAL MEMOIRS collaboration with Mayall at Lick Observatory, to measure the radial velocities of all the planetary nebulae, in order to stucly the kinematics of this oIcI, disk system of objects that can be observed out to great distances from the sun. Eventually Minkowski obtained anti measured nearly all the spectro- grams himself, and, although he never published the incli- viclual velocities, he discussed the general results in a naner and in a review chapter published in 1965. 1 ~ Minkowski was fascinated by the forms of planetary nebulae and invested large amounts of observing time with the 100-inch and later with the 200-inch Hale telescope at Palomar in taking direct photographs of inclividual objects. He used various combinations of glass filters and photo- graphic emulsions to isolate narrow spectral regions around specific nebular emission lines, for instance, LO IlI] AA4959, 5007, and Ha + EN IT] AA654S, 6563, 6583. These pictures, many of them taken in conditions of fine seeing, clearly illus- trate the ionization structure of planetary nebulae, their fre- quently cylindrically symmetric overall structure, and their complicated fine structure, often consisting of filaments, con- densations, knots, and the like down to the smallest resolvable scale. Although some of these planetary-nebula pictures were published by Minkowski himself, ant] more were used as il- lustrations in the two International Astronomical Union sym- posium volumes on planetary nebulae, many of them have never been reprocluced. Minkowski observed and analyzed the spectra of many in(liviclual planetaries, always trying to understand them physically: their masses, composition, tem- perature, and density structure, even their evolution. As an expert in applied optics, Minkowski made many instrumental contributions to the Mount Wilson Observatory ~ D. E. Osterbrock and C. R. O'Dell, eds., Planetary Nebulae (Dordrecht: D. Reidel, 1968), xv + 469 pp. and Yervant Terzian, ea., Planetary Nebulae, Observations and Theory (Dordrecht: D. Reidel, 1978), xxi + 373 pp. .
RUDOLPH LEO BERNHARD MINKOWSK! 277 spectrographs. Plane gratings were just coming into regular astronomical use in the 1940s, and Minkowski analyzed the curvature of the spectral lines they introduced, and how this effect may be corrected. His work on this subject received the sincerest form of appreciation when a paper was accepted and published in the Astrophysical Journal on the same subject over thirty-five years later, consisting entirely of results and conclusions that were included in Minkowski's original paper. At Hamburg, Baade and Minkowski were close friends with the eccentric, one-armect optician, Bernhard Schmidt, who invented the Schmidt camera in 1930. This camera, a combination of a spherical mirror with a thin aspheric cor- rector at its center of curvature, forms a very fast, wide-field optical system. Usec! as photographic telescopes, Schmidt cameras can produce excellent deep exposures of nebulae and star fields, as shown by Schmidt himself, and later by Fritz Zwicky, with the TS-inch at Palomar Mountain. Minkowski was one of the leaders in pushing the use of Schmidt cameras in spectrographs, where they are far superior to the lens cameras previously employed. In par- ticular, the/.5 conventional Schmidt anct thef/0.67 solid- block Schmidt cameras designed by Minkowski for the 100-inch Newtonian spectrograph were faster and produced much better images than the ogler, thick-lens, microscope- objective systems used by Humason for obtaining spectra of faint galaxies. By the time Minkowski came to America in 1935, the design and construction of the 200-inch telescope for Palo- mar Observatory was well under way on the campus of the California Institute of Technology in Pasadena. It was built with funds provider! by the Rockefeller Foundation, with the understanding that Palomar was to be operated jointly with Mount Wilson Observatory by Caltech and the Mount Wilson .
278 BIOGRAPHICAL MEMOIRS staff. Undoubtedly, Baade and Minkowski were among the strongest voices in urging Adams, Hubble, and the rest of the Observatory Council to recommend enlarging the project by building the largest Schmidt telescope in the world to supple- ment the largest reflector in the world. The result was the 48-inch Schmidt telescope at Palomar, a magnificentf/2.5 instrument that takes plates covering over six degrees square with excellent definition. The first large task for the 48-inch Schmidt, after it went into regular operation in 1950, was the National Geographic Society-Palomar Observatory Sky Survey. The entire sky from the north pole down to declination -33° was surveyed in 935 preselected, overlapping fields. Two plates a blue exposure, covering the wavelength region AA3600-4800, and a reel exposure, covering AA620~6700 were taken in im- mediate succession. If these exposures passed rigid quality and uniformity requirements, they were reprocluced by a carefully standarclized contact-print procedure ant! dis- tributed to the research institutions that had ordered them. Minkowski was in overall charge of this entire operation. He tested and adjusted the Schmidt telescope; set up the observing procedures; personally supervised Albert G. Wil- son, Robert G. Harrington, and George O. Abell, the ob- servers who took nearly all the plates; and examined all the plates that passed their preliminary screening, macle the final judgment as to whether or not they were acceptable, and constantly inspected the duplicate negatives and final prints ant! plates produced from them. His very high standards, coupled with his technical expertise and experience, made the resulting Sky Survey prints and plates an extremely high- quality body of research material. Every serious observatory and research astronomy department has a set, and they have been used for innumerable research investigations.
RUDOLPH LEO BERNHARD MINKOWSKI 279 The survey was later extended to45° declination, in one spectral region only, AA540~7000, by John Whiteoak, using the Palomar 48-inch Schmidt. The far southern hemisphere is now being surveyed, in a very similar way, by the new European Southern Observatory Schmidt telescope at La SilIa, Chile and the United Kingdom Schmidt telescope at Siding Springs, Australia. When the 200-inch telescope was completest after World War IT and went into operation with the 48-inch Schmidt at Palomar Observatory, Minkowski ant! his colleagues became staff members of Mount Wilson and Palomar Observatories, as the joint operation was named, and faculty members at Caltech. Ira S. Bowen, longtime Caltech laboratory spectros- copist and solver of the puzzle of the identification of the forbiciclen lines in gaseous nebulae, became director of the institution. Convinced of the advantages of Schmidt cameras for astronomical spectroscopy, he took personal charge of the high-ctispersion couple spectrograph of the 200-inch Hale telescope, but left Minkowski responsible for the fast, low- dispersion prime-focus spectrograph and the 48-inch Schmidt. Bowen had macle the final choice of the basic optical parameters of the 48-inch, and as director he insisted that the Sky Survey be completed before the telescope was turned over to the research programs of individual staff members. Bowen and Minkowski tract great respect for one another's optical and instrumental abilities, and they discussed new developments frequently. Caltech started its own astronomy department, to whichin addition to Zwicky Jesse Greenstein, Guido Munch, and ~ were the first three members appointed. Fred Hoyle was a frequent visitor. We had a regular, weekly Astronomy-Physics lunch at the Atheneum, the Caltech faculty club, at which Baade, Minkowski, and Armin Deutsch
280 BIOGRAPHICAL MEMOIRS from the Mount Wilson offices were always faithful par- ticipants, usually along with a few others. Minkowski was always eager to hear of the latest developments in physics and astrophysics and happy to tell William Fowler, Richard Feyn- man, Matthew Sands, Leverett Davis, and the other physicists what he had been doing at the telescopes. With the increased light-collecting power of the 200-inch, Minkowski was able to get better data on fainter supernovae, planetary nebulae, and other nebulous objects. But he soon found himself heavily involves] in the problem of the optical identification of radio sources. Raclio astronomy was born in the early observations of Karl Tansky ant] Grote Reber, but it came to vigorous life after World War Il. Radio engineers and physicists such as E. G. Bowen, }. L. Pawsey, Bernard I,ovell, Martin Ryle, John Bolton, R. Hanbury Brown, anc! Bernard Mills returned to academic and government pos~- tions in England and Australia from the wartime laboratories in which they had cleveloped radar and other advanced detection, location, and identification systems. They had seen solar anc! celestial radio-frequency radiation by its inter- ference effects, and resolved to stucly it to learn more about the universe. Although their first interferometers and reflec- tors gave only very rough angular coordinates of the indi- vidual radio sources (originally often collect radio stars), the very bright source, Taurus A, was soon identified with the Crab nebula by Bolton and Gordon Stanley. In late 1948 Boltonwho with StanIeyancl O. B. Slee had by then also identified Centaurus A and Virgo A with the optical galaxies NGC 5128 and M 87, respectively wrote to several prominent optical astronomers to seek their help in making further identifications. He chose between Baacle and Minkowski by flipping a coin. The luck of the toss decreecI he should write to Minkowski; he slid, and received a reply from Baade. Therefore Bolton addressed his next letter to Baade, .
RUDOLPH LEO BERNHARD MINKOWSK! 281 and received a reply from Minkowski. They were both highly interested in the radio-source identification problem, and collaborated very closely in their investigations; Minkowski did all of the spectroscopic work and shared with Baade the taking of the direct exposures. As senior members of the Mount Wilson and Palomar Observatories staff, they were able to command large amounts of prime dark observing time with the two most powerful telescopes in existence, and they were willing to commit a sizeable fraction of their time to searching for the optical counterparts of radio sources. Some of their first iclentifications were additional super- nova remnants within our galaxy, such as Cassiopeia A and Puppis A; others were galaxies with strong broad emission lines, such as Cygnus A and Perseus A. These galaxies opened the fascinating hope of a whole new attack on the cosmological problem. Cygnus A, for instance, is a faint and insignificant optical object, but one of the strongest radio sources in the sky. Surely among the numerous weak radio sources there must be other galaxies physically similar to Cygnus A, faint only because of their great distances, greater than the distances of any galaxies then known. To recognize such objects was the task Baade and Minkowski set for them- seIves. The problem was always the insufficient accuracy of the radio positions. In their papers, in their correspondence, in their personal conversations with all the radio astronomers whom they met at conferences and who visited Pasadena, Baade and Minkowski constantly urged the necessity of im- proving the positional accuracy to the standard of optical astronomy which the radio astronomers have by now essen- tially achieved, with probable errors of order one-tenth of a second of arc, rather than the several degrees of the early days. By their pioneering identification work, Baade ant! Minkowski established that some strong radio sources are
282 BIOGRAPHICAL MEMOIRS supernova remnants within our Galaxy and that many others are galaxies with strong emission lines in their spectra, some- times distorted in form, sometimes heavily obscured by crust. They were less successful in their physical interpretation of the radio galaxies as galaxies in collision, an idea derived from Baacle's earlier work with Lyman Spitzer on S0 galaxies. The spectra and forms of Cygnus A, Perseus A, and Cen- taurus A suggested that these objects were actual examples of colliding galaxies, but this interpretation has now generally gone by the board. Most astronomers anti astrophysicists are now seeking the basic cause of the generation of magnetic fields and relativistic electrons that produce the observed nonthermal radio radiation in the galactic nuclei. A still greater contribution to radio astronomy by Baade and Minkowski was the welcome anct encouragement they extendecl to the early radio physicists. They passed on their optical knowledge, skills, and resources to the newcomers, helping them to become respecter! members of the astronom- ical community. Caltech's Owens Valley Radio Observatory was built as a result of Baade, Greenstein, and Minkowski urging that the Institute get into this important new fielcl of research. Baade's participation in the radio work ended when he retired from the Mount Wilson and Palomar Observatories' staff in 195S, at the age of sixty-five. After brief periods as a visiting professor at Harvard and at the Australian National Observatory in Canberra, he moved to Gottingen, where he died less than two years after his retirement, leaving un- finished many projects he had hoped to complete. Minkowski continued to identify and obtain spectra of radio sources alone after Baa~le's retirement, but he in turn had to retire two years later, on June 30, 1960. A few months before his retirement, he used the 200-inch to take a spectro- gram of the faint radio galaxy 3c 295, which had been iclenti- fied by Bolton on a 48-inch Schmidt plate from an accurate
RUDOLPH LEO BERNHARD MINKOWSKI 283 radio position. On his spectrogram Minkowski identified the single emission line as tO IT] A3727, the only reasonable identification possible, anct measured its recTshift as z = 0.46, nearly half the velocity of light. This broke the observational barrier at about z = 0.2 for normal galaxies, which Humason had been struggling to surpass for nearly ten years. Minkow- ski's record redshift remained the largest known for a galaxy for over fifteen years, until it was topped by Hyron Spinrad, James Westphal, Jerome Kristian, and AlIan Sandage with z = 0.75 for 3c 343. ~ The first quasistelIar radio sources, or quasars, were iclentified after Minkowski's retirement, again from very accurate radio positions. The ricictIe of their spec- tra was broken by Maarten Schmidt, who thus proved that they have very large redshifts. At the present writing, the quasar with the largest known reclshift is oQ 172, with z = 3.53 or 91 percent of the velocity of light. Minkowski also worked on another important problem, the mass-luminosity ratio in elliptical galaxies. Although in spiral galaxies it is possible to measure the rotational velocity as a function of distance from the center, and thus derive the mass distribution, in elliptical galaxies there are no H TI re- gions or bright Mostar associations that can be observed spectroscopically, as there are in spirals. Minkowski realized that the only way to proceed was to obtain good, high- clispersion spectra of the nuclei of elliptical galaxies, measure the width of the absorption lines to get the velocity ctisper- sion of the stars near the nuclei, and thus determine the central mass densities. The values of mass-to-luminosity ratios he clerived in this way were the best available for many years, until they were recently supplanted by Sandra M. Faber, W. L. W. Sargent, and others using detectors much more sensitive than the photographic plates available to Minkowski. After his retirement from Mount Wilson and Palomar Observatories, Minkowski spent the year 196~1961 as a visit-
284 l BIOGRAPHICAL MEMOIRS ing professor at the University of Wisconsin. He lectured on gaseous nebulae, supernovae, and radio sources ant! started C. R. O'Dell on a thesis on the evolution of planetary nebulae and their central stars, a thesis O'Dell completec! uncler my supervision. Earlier, at Caltech, Minkowski hac! been an unofficial adviser for Abell's thesis on clusters of galaxies, for which I was also the official sponsor; ~ believe that these were the only two Ph.D. theses with which Minkowski was closely involved. After his year at Madison, Minkowski spent some months as a guest investigator in Australia, working with Bolton on radio-source identifications. In 1961 Minkowski was appointed a research astronomer at the Berkeley Radio Astronomy Laboratory of the Univer- sity of California. He and his wife mover! their home to Berkeley, where they were close to both their children. There he continued writing up his own research results as well as several review articles and served as a constant source of encouragement and advice to faculty members, postdoctoral fellows, and graduate students. He collaborated on several projects, particularly on the properties of normal galaxies, with various Berkeley faculty members. In 1964 he took part in the Solvay Conference in Brussels on the structure and evolution of galaxies. In 1965 he formally retired a second time at the mandatory age of seventy, but continued to come to the campus regularly and (liscuss research. The last paper he wrote, fittingly enough, was a report on the accomplish- ments of the Palomar 48-inch Schmidt telescope, which he presented at a conference in Hamburg devoted to planning the European and United Kingdom southern-hemisphere Schmidt surveys. Minkowski was elected to the National Academy of Sciences in 1957 and was awarcled the Catherine Bruce Gold Mecial of the Astronomical Society of the Pacific in 1961 for his clistinguishec! services to astronomy. In 196S, at the cen-
RUDOLPH LEO BERNHARD MINKOWSKI 285 tennial of the University of California, Minkowski received an honorary doctorate at the Berkeley commencement exer- cises for his outstanding astronomical achievements. Personally, Minkowski was a large, friencTly, bearlike per- son. He was much stronger than most astronomers, and he could always get an extra turn out of any screw, clamp, or guiding eyepiece adjustment. The designers and instru- ment makers at the Mount Wilson shops used to joke that their products had to be not only "astronomer-proof" but "Minkowski-proof." His office, at the Mount Wilson headquarters on Santa Barbara Street in Pasadena, was famous for being the most cluttered of any in the building, no mean distinction. Over the years he had accumulated tremendous quantities of folders of measurements, calculations, drafts of papers, re- prints, preliminary results, and the like. His standard pro- cedure was to keep this material piled on top of his desk where he could get at it. Photographic plates of the objects he was studying, in paper envelopes, were immersed in these piles, which were heaped up to the angle of repose. if a visitor came into his office to discuss some planetary nebula with him, Minkowski would begin to talk about it; then dive un- erringly into the right place in the right pile to come up with a plate of its spectrum; open the envelope; pull out the tiny glass plate that should have been, but often was not, mounted on a microscope stifle; blow the cigarette ashes off of it; some- times stick it together with scotch tape if it had fallen off the desk and broken in some previous conference; look at it through an eyepiece and describe it while a lightec] cigarette dangled from his mouth a few inches from the plate; hand the visitor the plate and an eyepiece while he continued ex- pounding; recapture the plate; wipe it off with the side of his hancI; put it back in the envelope; and put the envelope back in the exact same place in the exact same pile. There was
286 BIOGRAPHICAL MEMOIRS clearly a higher system to the mess, which he alone uncler- stood. Minkowski was a very good observer. He was ex- perienced, skilled, understood the telescope and the spectro- scopes, what they conic! do and could not do, and what he himself could clo and could not do. He was a curious mixture of patience and impatience. Setting on a faint planetary nebula or supernova remnant, he was impatient and eager to begin. For some years the night assistants at Palomar had a tape, surreptitiously recordecI, of Minkowski talking to him- self in the prime-focus cage of the 200-inch as he maple a setting: "Where is that thing? . . . ~ think that's it over there. [Sound of slow motion motor] Damn! Wrong button [SIow motion again].... There it is.... Now where's that little double to the left? ... No that's not it.... ETo the night assistant] Try a little west.... Stop! [To himself Here it comes ESIow motion].... Yes ~ think that's it.... Pull it down a little [Slow motion].... Ah! Too Much! ESIow mo- tionl.... Now I've got it [Sound of dark slide opening- then, to the night assistant] Start the exposure! I'll take three hours on this one. You can rest a while." This is followed by a long sigh, then he began to hum the "Ode to Joy" from Beethoven's Ninth Symphony, and the tape mercifully ends. He was very patient in the guiding, doing a careful job all during the tiresome long exposures he took, but impatient to see the results. He would hurry into the darkroom with a recently exposed plate, develop it, give it quick rinse in water, plunge it into the hypo fixing solution, count thirty seconds, light a cigarette, and have the plate out of the hypo and be looking at it with his eyepiece before it had cleared. ~ well remember when he showed me how to use the nebular spectrograph at the Newtonian focus of the ~ OO-inch telescope one hot summer night in 1954. Minkowski, in his shirt sleeves, was wearing a fur-linecI cap of the type popu- larized by the Chinese infantrymen in Korea a few winters
RUDOLPH LEO BERNHARD MINKOWSKI 287 before. Sweat was dripping clown his face as he clemonstrated how to raise the heavy spectroscope to see the star field, and then lower the instrument again to center the object and start the exposure. "Why clo you wear that hat?", I asked him. "Makes a good crash helmet," he muttered, and I laughed. ~ understood what he meant the next month when, observing by myself, ~ hurried down the lacicler from the platform with a just-exposed plate to develop, dashed across the observing floor toward the stairs to the darkroom, ant! slammed my bare head into the black, steel, absolutely immovable bottom end of the 100-inch. My head stopped right there, but my feet kept on going, ant! I was knocked out for a second. As I came to, lying flat on my back, feeling for the telescope above me, ~ resolved to pay a little more attention to what Rudolph was trying to teach me. With me, as with everyone else who approached him, he was extremely friendly, very helpful, and always happy to talk astronomy. Minkowski worker] very hard anct single-mindedly on re- search. ~ once told Luise, his wife, that when I was a student, some years before, ~ had seen a magazine article about the staff members who were to work at Palomar and what their hobbies were. In a picture in that article Rudolph had been shown at his hobby, playing the piano, anal ~ asked her if he still played. (Humason had been shown in the same article, washing his car.) She replied in her emphatic way "Oh, ~ remember that article. That reporter didn't understand any- thing! He wanted hobbies, but I toIcI him none of those men had any hobby but astronomy! He wouldn't believe it. Rudolph usec} to play the piano, ages ago when he was young, but he hasn't touched it for years." How right she was. Yet he always enjoyed the outdoors and manager! to find time for camping and fishing expeditions with his family in the High Sierras, just as in earlier years he had made time for climbing expeditions in the Alps with his fellow students. Minkowski and Baade remained close friends all the years
288 BIOGRAPHICAL MEMOIRS they were together at Pasadena. Baacle, two years older, was far more intense, mercurial, and flamboyant. His conversa- tion and lectures were peppered with stories, always apt, always interesting, sometimes true. He once correctly cle- scribed his own voice as "sounding like a barking (log." Minkowski was quiter, more phIegmatiic, but never at a loss for words. Often the two of them were at Mount Wilson together, on the 60-inch and 100-inch telescopes, or later at Palomar, on the 200-inch and the 48-inch Schmidt. Then they wouicl walk together slowly up to the domes in the even- ing and back to the monastery in the morning, discussing astronomy loudly, in voices that carried all over the mountaintops. As they argued vehemently in a queer mix- ture of German and English, it sounded to the uninitiated as if a battle were about to begin, but they always listened to one another and remained fast friends. Minkowski and his wife were completely Americanized, in a way Baade and his wife never were. Ruclolph and Luise and their children became naturalized United States citizens as soon as they could, in 1940. During WorIct War IT, Minkowski worked as a civilian scientist on one of the Office of Scientific Research and Development projects at Caltech, while Luise went to night school to learn to be a ciraftsman, which enabled her to get a job at the Lockheed plant in Burbank. They never thought of retiring anywhere but in America. Throughout their lives they were both very hospitable people; there were few astronomical visitors to Pasadena whom they die] not entertain. Even after his retirement from his second job at the age of seventy, Minkowski remained in good health until, in the 1970s, he began to suffer from kidney disease. His condition gradually worsened, although he was up and about until the end. In his later years he had become a television football afflict, and the last game he saw, and enjoyed mightily, was
RUDOLPH LEO BERNHARD MINKOWSKI 289 the 1976 Rose Bow! in which UCLA roundly defeated Ohio State. He cliec! in Berkeley of a sudden stroke on January 4, 1976. The Astronomical Society of the Pacific, under the leadership of HaroIcT F. Weaver, organizer] a memorial symposium in Minkowski's honor, held at their annual meet- ing in June 1977 at Berkeley, in which reviews were pre- sentecT of the various subfields of astronomy in which he had speciaTizecl. His wife and daughter atten(lecl part of the sym- posium, and Louise particularly enjoyed a luncheon in con- nection with it, at which she renewed her acquaintance with many old friends. Although she was in goocl health then, she was soon attacked by a very rapidly developing case of cancer and ctied on March 1 1, 1978. Their children, Eva Minkowski Thomas and Herman O. Minkowski, together with seven grandchildren, survive them in California. In summary, Rudolph Minkowski was an outstanding ob- servational astronomer and astrophysicist. His life was de- voted to science. His work act~ec! greatly to our knowledge of planetary nebulae, supernovae anct their remnants, radio sources, and galaxies; present research in these fields is along lines shaped in no small measure by his results. THIS MEMOIR iS based largely on the written record of Rudolph Minkowski's research, published in the papers listed in his bibliog- raphy, and on my personal conversations with him and with his wife Luise over the years since 1953, when I went to Caltech as a young faculty member and began working closely with him. I have also been able to use clippings, articles, news releases, letters, docu- ments, and reminiscences provided through the kindness of his children, Eva M. Thomas and Herman 0. Minkowski, and of many of his friends, colleagues, and fellow scientists. I am deeply in- debted to all of them for their help.
290 BIOGRAPHICAL MEMOIRS BIBLIOGRAPHY 1921 Untersuchungen uber die magnetische Drehung der Polarisation- sebene in nichtleuchtenden Na-Dampf. Ann. Phys. 66:20~26. .. Uber den Einfluss des Druckes fremder Gase auf D-Linien in gesattigtem Na-Dampf. Phys. Z., 23:6~73. With R. Ladenburg. Die Verdampfungswarme des Natriums und die Ubergangswahrscheinlichkeit des Na-Atoms aus dem Re- sonanz- in den Normalzustand auf Grund optischer Mes- sungen. Z. Phys., 6:153-64. 1922 A With R. Ladenburg. Die chemische Konstante des Na und K. Z. Phys., 8:137~1. 1923 With H. Sponer. Uber die freie Weglange langsamer Elektronen in Gasen. Z. Phys., 15:399~08. Uber die freie Weglange langsamer Elektronen in Hg- und Cd- Dampf. Z. Phys., 18:258-62. 1926 Naturliche Breite und Druckverbreiterung von Specktrallinien. Z. Phys., 36:839-58. 1928 With R. Ladenburg. Uber die Messung der Lebensdauer ange- regter Na-Atome aus der Helligkeit von Na-Flammen und uber den Dissoziationsgrad von Natriumsalzen in der Flamme. Ann. Phys., 87: 298-306. 1929 .. Uber die Abhangigkeit des Intensitatsverlaufs in druckverbreiter- ten Spektrallinien vom verbreiterndem Gas. Z. Phys., 55: 16-27. With W. Gordon. Uber die Intensitaten der Starkeffektkompo- nenten der Balmerserie. Naturwissenschaften, 17:368. Die paramagnetische Drehung der Polarisationsebene in der Nahe von Absorptionslinien. Naturwissenschaften, 17: 567-68.
RUDOLPH LEO BERNHARD MINKOWSKI 291 1930 Bemerkungen uber den Einfluss der Selbstabsorption auf Intensi- tatsmessungen von Spektrallinien. Z. Phys., 63:188-97. With W. Muhlenbruch. Die Ubergangswahrscheinlichkeit in den beiden ersten Dubletts der Hauptserie des Casiums. Z. Phys., 63: 198-209. 1933 With W. Baade, F. Goos, und P. P. Koch. Die Intensitatsverteilung in den Spektrallinien des Orion-Nebels. Z. Astrophys., 6:355- 84. 1934 Die Intensitatsverteilung in den Spektrallinien des Orionnebels. II. Z. Astrophys., 9:202-14. 1935 Die Intensitatsverteilung in druckverbreiterten Spektrallinien. Z. Phys., 93:731~0. With H. Bruck. Die Intensitatsverteilung der in Molekularstrahl erzeugten Spektrallinien. Z. Phys., 93:272-83. Die Intensitatsverteilung der roten Cd-Linie im Molekularstrahl bei Anregung durch Elektronenstoss. Z. Phys., 95:284-98. Wahre und scheinbare Breite von Spektrallinien. Z. Phys., 95: 299-301. With H. G. Muller and M. Weber-Schafer. Uber die Bestimmung .. der Ubergangswahrscheinlichkeit der D-Linien des Natriums aus absoluten Helligskeitsmessungen, die Dissoziation von Na- triumsalzen und die Halbweite der D-Linien in der Leuchtgas- Luftflamme. Z. Phys., 94:145-71. 1936 With W. Baade. The spectrum of comet Peltier (1935a). Publ. Astron. Soc. Pac., 48:277-78. 1937 Note on the motion of masses of gas near novae. Astrophys. }., 85: 18-25.
292 B IOGRAPH I CAL M EMOI RS With W. Baade. The Trapezium cluster of the Orion nebula. Astro- phys.J.,86:119-22. With W. Baade. Spectrophotometric investigations of some o- and e-type stars connected with the Orion nebula. Astrophys. }., 86: 123-35. The spectrum of comet Finsler. Publ. Astron. Soc. Pac., 49:276-78. 1938 With I. S. Bowen. Effect of collisions on the intensities of nebular lines. Nature, 142:107~80. 1939 The spectra of the supernovae in arc 4182 and NGC 1003. Astrophys. }., 89:156-217. With R. Richardson. The spectra of bright chromospheric erup- tions from A 3300 to A 11500. Astrophys. }., 89:347-55. Note on the spectrum of T Coronae. Publ. Astron. Soc. Pac.,51:54. 1940 With M. L. Humason. A supernova in NGC 5907. Publ. Astron. Soc. Pac., 52:146-47. Spectra of the supernova in NGC 4725. Publ. Astron. Soc. Pac., 52:206-7. 1941 With M. L. Humason. The spectrum of the supernova in NGC 4559. Publ. Astron. Soc. Pac., 53:194. Spectra of supernovae. Publ. Astron. Soc. Pac., 53:224-25. 1942 Spectra of planetary nebulae of low surface brightness. Astrophys. J., 95:243-47. The Crab nebula. Astrophys. }., 96:199-213. Curvature of the lines in plane-grating spectra. Astrophys. }., 96: 306-8. The origin of cometary nebulae. Publ. Astron. Soc. Pac., 54: 190- 94.
RUDOLPH LEO BERNHARD MINKOWSKI 293 1943 The spectrum of the nebulosity near Kepler's nova of 1604. Astro- phys. J., 97:128-29. With P. Swings and A. McKellar. Cometary emission spectra in the visual region. Astrophys. J., 98: 142-52. The spectrum of comet Whipple 2 (1942f). Publ. Astron. Soc. Pac., 55:87-91. Nova T Coronae Borealis. Publ. Astron. Soc. Pac., 55:101-3. 1944 Schmidt systems as spectrograph cameras. J. Opt. Soc. Am., 34: 89-92. 1946 With L. H. Aller. The infrared spectrum of the planetary nebula NGC 7027. Publ. Astron. Soc. Pac., 58:258 - 60. New emission nebulae. Publ. Astron. Soc. Pac., 58:305-9. The distance of the Orion nebula. Publ. Astron. Soc. Pac., 58:356- 58. The continuous spectrum of the Crab nebula. Ann. Astrophys., 9:97-98. 1947 New emission nebulae (II). Publ. Astron. Soc. Pac., 59:256-58. 1948 Novae and planetary nebulae. Astrophys. I., 107: 106. New emission nebulae (III). Publ. Astron. Soc. Pac., 60:386-88. 1949 The diffuse nebula in Monoceros. Publ. Astron. Soc. Pac., 61 53. 1951 :151- Galactic distribution of planetary nebulae and Be stars. Publ. Obs. Univ. Mich., 10:25-32.
294 BIOGRAPHICAL MEMOIRS 1953 With {. L. Greenstein. The Crab nebula as a radio source. Astro- phys. J., 118:1-15. The electron temperature in the planetary nebula arc 418. Publ. Astron. Soc. Pac., 65:161-62. 1954 With W. Baade. Identification of the radio sources in Cassiopeia, Cygnus A, and Puppis A. Astrophys. J., 119:20~14. With W. Baade. On the identification of radio sources. Astrophys. J., 119:215-31. With L. H. Aller. The spectrum of the radio source in Cassiopeia. Astrophys. J., 119:232-37. With }. L. Greenstein. The power radiated by some discrete sources of radio noise. Astrophys. J., 119:238-42. With L. H. Aller. The structure of the Owl nebula. Astrophys. I., 120:261-64. With W. Baade. Abnormal galaxies as radio sources. Observatory, 74: 130-31. 1955 The observational background of cosmical gas dynamics. In: Gas Dynamics of Cosmic Clouds, ed. J. M. Burgers and H. C. van de Hulst, pp. 3-12. Amsterdam: North Holland. Radiative and collisional excitation. In: Gas Dynamics of Cosmic Clouds, ed. J. M. Burgers and H. C. van de Hulst, pp. 106-10. Amsterdam: North Holland. With L. H. Aller and I. S. Bowen. The spectrum of NGC 7027. Astrophys. }., 122:62-71. 1956 With O. C. Wilson. Proportionality of nebular redshifts to wave- length. Astrophys. J., 123:373-76. With L. H. Aller. Spectrophotometry of planetary nebulae. Astro- phys. J., 124:93-109. With L. H. Aller. The interpretation of the spectrum of NGC 7027. Astrophys. J., 124: 110-15.
RUDOLPH LEO BERNHARD MINKOWSK! 295 1957 Optical investigations of radio sources. In: Radio Astronomy, ed. H. C. van de Hulst, pp. 107-22. Cambridge: Cambridge Uni- versity Press. 1958 The problem of the identification of extragalactic radio sources. Publ. Astron. Soc. Pac., 70:143-51. Cygnus loop and some related nebulosities. Rev. Mod. Phys., 30: 048-52. 1959 Optical observations of nonthermal galactic radio sources. In: Paris Symposium on Radio Astronomy, ed. Ronald N. Bracewell, pp.315- 22. Stanford: Stanford University Press. With D. Osterbrock. Interstellar matter in elliptical nebulae. Astro- phys. J., 129:583-95. Observations of a galaxy in the Hercules cluster of nebulae. Astro- phys. J., 130:1028. 1960 Problems of extragalactic spectroscopy. Ann. Astrophys., 23:385- 96. With D. E. Osterbrock. Electron densities in two planetary nebulae. Astrophys. i, 1 3 1: 537-40. A new distant cluster of galaxies. Astrophys. T. 132:908-10. With J. L. Greenstein. Spectra of nuclei of planetary nebulae of very low surface brightness. Mem. Soc. R. Sci. Liege, 16:51-52. International cooperative efforts directed toward optical identifica- tion of radio sources. Proc. Natl. Acad. Sci. USA, 46: 13-19. 1961 The luminosity function of extragalactic radio sources. In: Proceed- ings of the Fourth Berkeley Symposium on Mathematical Statistics and Probability, Volume III, ed. Jerzy Neyman, pp. 245-59. Berkeley: University of California Press. NGC 6166 and the cluster Abell 2199. Astron. J., 66:558-61.
296 BIOGRAPHICAL MEMOIRS Internal dispersion of velocities in other galaxies. In: Problems of Extra-Galactic Research, ed. G. C. McVittie, pp. 112-17. New York: Macmillan. Identification with optical objects. In:ProblemsofExtra-GalacticRe- search, ed. G. C. McVittie, pp. 201-9. New York: Macmillan. Problems of observation and interpretation. In: Problems of Extra- Galactic Research, ed. G. C. McVittie, pp. 379-89. New York: Macmillan. 1963 With G.. O. Abell. The National Geographic Society-Palomar Observatory sky survey. In: Basic Astronomical Data, ed. K. Aa. Strand, pp. 481-87. Chicago: University of Chicago Press. Radio sources, galaxies, and clusters of galaxies. Proc. Natl. Acad. Sci. USA, 49:779-84. With G. O. Abell. The galactic distribution of planetary nebulae. Publ. Astron. Soc. Pac., 75:488-91. The spectrum of the supernova of 1954 in NGC 4214. Publ. Astron. Soc. Pac., 75:505-8. 1964 Supernovae and supernova remnants. Annul Rev. Astron. Astro- phys., 2:247-66. With I. L. Greenstein. The central stars of planetary nebulae of low surface brightness. Astrophys. I., 140:1601-3. The sub-system of planetary nebulae. Publ. Astron. Soc. Pac., 76: 197-209. 1965 The suspected supernova of AD 1006. Astron. J., 70:755. Planetary nebulae. In: Galactic Structure, ed. Adriaan Blaauw and Maarten Schmidt, pp. 321-43. Chicago: University of Chicago Press. 1966 Supernova of + 1066. Astron. I., 71:371-73. With I. R. King. Some properties of elliptical galaxies. Astrophys. J., 143:1002-3. The radio source Cassiopeia A. Nature, 209: 1339 40.
RUDOLPH LEO BERNHARD MINKOWSKI 297 Radio observations and cosmology. In: Atti Convegno sulfa Cosmo- log~ca, pp. 82-87. Firenze: G. Barbera. 1967 Supernova remnants. In: Radio Astronomy and the Galactic System, ed. Hugo van Woerden, p. 367. London: Academic Press. With H. M. Johnson. The peculiar nebula NGC 6302. Astrophys. I., 148:65~62. 1968 Introductory remarks ton Seyfert galaxies and related objects]. Astron. }., 73:842~5. Nonthermal galactic radio sources. In: Nebulae and Interstellar Mat- ter, ed. Barbara M. Middlehurst and Lawrence H. Aller, pp. 623-66. Chicago: University of Chicago Press. Radio galaxies (optical properties). In: Non-Stable Phenomena in Galaxies, ed. V. A. Ambarzumian, pp. 163-68. Yerevan, Arme- nia: Academy of Sciences of Armenian S.S.R. 1970 Spectroscopic observations of the central star tof the Crab nebula]. Publ. Astron. Soc. Pac., 82:47~77. 1971 Comments on supernova remnants and ancient novae. In: The Crab Nebula, ed. R. D. Davies and F. G. Smith, pp.241~7. Dordrecht, Holland: D. Reidel. 1972 Twenty years astronomy with the 48-inch Schmidt telescope on Palomar Mountain. In: The Role of Schmidt Telescopes in Astron- omy, ed. U. Haug, pp. 5-8. Hamburg: Hamburg Observatory. With }. Silk and R. S. Siluk. Bright nebulae near concentrations of high-velocity gas. Astrophys. J . (Lett. ), 1 75: L 1 23-2 5 . With I. R. King. Mass-luminosity ratios and sizes of giant elliptical galaxies. In: External Galaxies and Quasi-stellar Objects, ed. David S. Evans, pp. 87-88. Dordrecht, Holland: D. Reidel.
298 BIOGRAPHICAL MEMOIRS 1973 With Jesse L. Greenstein. An atlas of supernova spectra. Astrophys. J., 182:225 43. 1975 The identification of radio sources. In: Galaxies and the Universe, ed. Allan Sandage, Mary Sandage, and Jerome Kristian, pp. 177- 97. Chicago: University of Chicago Press.