Title: Wilhelm Heinrich Walter Baade Papers ,
Date (inclusive): 1915-1960
Baade, Wilhelm Heinrich Walter
Extent: 22 boxes and one large folder
The Huntington Library
San Marino, California 91108
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[Identification of item], Wilhelm Heinrich Walter Baade Papers , The Huntington Library, San Marino, California.
Wilhelm Heinrich Walter Baade (he did not often use his first two names) was one of the most important astronomers of the
twentieth century. As an observer at the Mount Wilson Observatory, he ranks alongside Edwin Hubble in significance. Baade,
however, was an excellent theoretician as well as observer. His interest in the stellar content of various star systems led
him to develop his famous concept of stellar populations. And his observing skill led to his unexpected resolution of the
inner parts of the Andromeda galaxy into individual stars. His work with the new 200-inch Hale telescope would eventually
lead to a change in contemporary knowledge of the distances of the galaxies. Though his scientific method resulted in much
of his work being published posthumously, Baade's impact on the development of astronomy was enormous.
Walter Baade was born on March 24, 1893 at Schröttinghausen in Westphalia, Germany. His father Konrad, a schoolteacher, and
his mother Charlotte, planned for Walter to pursue a career in theology. From 1903 to 1912 Baade attended the Friedrichs-Gymnasium
in Herford with this end in mind. Over these years, however, Baade turned away from theology and toward science and mathematics.
He attended the university at Münster from 1912 to 1913 and then continued at Göttingen until 1919. Baade studied mathematics,
physics, and astronomy and spent his last four years at Göttingen as assistant to the great mathematician, Felix Klein. His
Ph.D. dissertation in 1919 was on the spectrum of the double star, ß Lyrae.
Upon receiving his degree, Baade went immediately into astronomical work. He obtained a position as an assistant at the Hamburg
Observatory, being in charge of the 40-inch reflecting telescope. His abilities were soon recognized by others and in 1926
he received a Rockefeller International Education Board Fellowship to study in the United States and Canada. During the next
year, Baade spent a great deal of time at the Harvard College Observatory, the Dominion Astrophysical Observatory, Yerkes,
Lick, and Mount Wilson. The director of Mt. Wilson, Walter S. Adams, later noted that Baade's "ability and personal characteristics
made a strong appeal to the members of our staff." Returning to Hamburg in 1927, Baade's responsibilities grew, and a year
later he was offered the position as Chair of Astronomy at Jena, a position he turned down in order to remain at Hamburg and
its better astronomical facilities. Baade was undoubtedly in line for the directorship at Hamburg, and in 1929 he became a
Privatdozent at the University of Hamburg and was placed in charge of the observatory's eclipse expedition to the Philippines.
However, in the opinion of many at the time, the current director at Hamburg, Richard Schorr, was too conservative and did
not encourage Baade's research into newer and more promising fields of astrophysics. Instead, Baade had to be responsible
for the less glamorous tasks such as confirming the positions of asteroids and comets. This was the situation in 1931 when
Baade was offered a position as astronomer at the Mount Wilson Observatory. The Mt. Wilson astronomers realized that Baade
was a young man of marked promise, capable of developing significant research programs. Even though Baade was reluctant to
leave Germany the offer was one which Baade could not refuse and he joined the Mt. Wilson Observatory in October 1931.
Baade quickly took up his photometric duties, trying to improve and extend the magnitudes in some of Kapteyn's selected areas.
To his credit, however, he soon realized that the work of Stebbins and Whitford in obtaining accurate photoelectric magnitudes
would be more valuable. As a result, he and Hubble encouraged the two astronomers to develop their system using the large
telescopes on Mt. Wilson. Baade's main research thrust continued into the field of the stellar content of various stellar
systems: clusters, galaxies, etc. This work would lead him to his important development of the idea of stellar populations.
After Shapley's 1938 finding of a new type of stellar system, the dwarf elliptical galaxy, Baade and Hubble worked on resolving
these systems into their constituent stars for the first time. World War II soon intervened, but in a bit of irony provided
Baade with the best opportunity to continue his research. Before the war began, Baade had taken out papers to become an American
citizen. After losing these papers while moving to a new house, he did not bother to renew his citizenship efforts. Consequently,
when the war broke out Baade was declared an enemy alien and confined to Pasadena. After some appeals, the Observatory managed
to get special permission for Baade to be at Mt. Wilson after dark in order to do research. Considering that most of the astronomers
at Mt. Wilson were engaged in war work and that Los Angeles was often in a "brown out" situation to protect coastal shipping,
Baade had plenty of time and darkness with which to use the 100-inch telescope. Under these conditions, and by using every
means at his disposal, Baade achived what was then considered impossible with the 100-inch telescope: the resolution into
stars of portions of the nucleus of the Andromeda galaxy (M31) and its two companions. With this accomplished, Baade was able
to flesh out his concept of stellar populations. By the time of the International Astronomical Union's meeting in Rome in
1952, he was able to show evidence that there were two basic populations of stars: young, blue stars in dusty galactic regions
(Population I) and older, redder stars in dust free regions (Population II)
When Palomar Mountain's 200-inch telescope was put into operation in 1949, Baade was there to see if he could delve deeper
into the stellar content of the Andromeda galaxy. Working to the limit of the telescope, Baade failed to discover a particular
class of stars, known as RR Lyrae stars. According to the current knowledge of the intrinsic brightness of RR Lyrae stars,
however, he should have been able to detect them with the 200-inch telescope. This led Baade to realize that the Andromeda
galaxy was more distant than previously imagined. As a result of Baade's work, the size of the universe had to be roughly
doubled. This result was announced at the same 1952 Rome meeting mentioned earlier.
Baade was active in many fields of astronomy. One important one was his work to show that there was indeed a class of novae
which were 10,000 times brighter than the classical novae. His results went far towards proving that these exceptionally brilliant
exploding stars, called supernovae, did exist as a distinct phenomenon. Baade also studied historical supernovae, eventually
discovering the remnant of Kepler's supernova of 1604 in the constellation Ophiuchus.
Another field of research in which Baade entered was the optical identification of radio sources. As radio astronomy became
more sophisticated, many astronomers began to chart the exact locations of celestial sources of radio waves. Baade, along
with his colleague Rudolph Minkowski whom Baade had aided in leaving Germany and coming to Mt. Wilson in 1933, aided greatly
in the effort to match these radio sources with optically visible objects, such as galaxies and supernova remnants.
Baade also continued to occasionally pursue the asteroids, as he did at the Hamburg Observatory. In 1925 at Hamburg, he discovered
Hidalgo (944), an asteroid whose orbit takes it farther from the Sun than any other known at the time. Then in 1944, he discovered
another unusual minor planet, Icarus (1566), one of a few which occasionally pass near to the earth.
In 1958, Baade retired from the Mt. Wilson and Palomar Observatories. Spending some time at Harvard and the Mount Stromlo
Observatory in Australia, he returned to Germany in 1959 with his wife of thirty years, Johanna "Muschi" Bohlmann, and became
Gauss professor at his old school, Göttingen. On June 25, 1960, while convalescing after an operation to correct his chronic
hip problem, Baade suffered heart failure and died suddenly.
Before he published any of his work, Baade always insisted on having enough observational evidence to leave his claims without
any doubt. This explains why, after 1944, Baade published very little. The enormous task which Baade undertook, to unify stellar
astronomy, left him too little time to collect enough evidence to publish his results before he died. However, Baade did not
feel compelled to publish; he was always in constant contact with the leading astronomers, letting them know of his ideas
and research. Paul Scherer, former executive officer of the Carnegie Institution of Washington once said, "We all recognize
at the Institution that Baade publishes very little in the journals but we know for a fact that he is indeed one of the most
prolific of our staff members. He 'publishes' his data by conversations in his office with the world's astronomers." Indeed,
Baade's communication with others was so intense that he rearranged his office hours to enable him to work at home from 8
P.M. to 2 A.M.
The amount of unpublished material Baade left behind was great. This fact was realized among astronomers, and Jan Oort and
Ira Bowen managed to collect his notes and measurements from Germany and parcel them out to his colleagues who were able to
organize, reduce, and publish the material. Among those at the Mount Wilson and Palomar Observatories who aided in this were
Henrietta Swope, Halton C. Arp, and Allan Sandage. Some material remains at the Leiden Observatory, but most of it was sent
to Mt. Wilson. The bulk of Baade's papers, which were returned to Pasadena, were organized by Henrietta Swope and stored in
the attic of the Mt. Wilson and Palomar Observatories office building. Her labels have been retained for the time being until
Baade's papers are more fully catalogued.
Baade's papers at present consist in 22 boxes and one large folder. The first 14 boxes (1-14) are 5-inch legal sized Hollinger
boxes. The next 5 boxes (15-19) are 5-inch letter sized Hollinger boxes. Box 20 is a flat Hollinger box, 202" x 162" x 3",
containing oversized charts and photographic prints. Boxes 21-22 are flat Hollinger boxes, 24" x 20" x 3" containing oversized
charts and photographic prints. The oversize folder contains large charts which would not fit into the standard boxes. The
following list denotes the content of each box giving a very general description of the subject of the material included.
The numbers in parentheses following each major heading corresponds to the numbers on Henrietta Swope's list and need not
be retained after further cataloguing.
Arp, Halton Christian. "Wilhelm Heinrich Walter Baade, 1893-1960."
Journal of the Royal Astronomical Society of Canada 55 (1961): 113-16.
Dieke, Sally H. "Wilhelm Heinrich Walter Baade."
Dictionary of Scientific Biography, C. C. Gillispie, ed. New York: Charles Scribner's Sons, 1970.
Jackson, John. "The President's Address on the Award of the Gold Medal to Dr. Walter Baade."
Monthly Notices of the Royal Astronomical Society 114 (1954): 370-83.
Sandage, Allan R. "Wilhelm Heinrich Walter Baade."
Quarterly Journal of the Royal Astronomical Society 2 (1961): 118-21.
Sandage, Allan R. "Wilhelm Heinrich Walter Baade (1893-1960)."
Year Book of the American Philosohical Society (1960): 108-13.
Wilson, Olin Chaddock. "The Award of the Bruce Gold Medal to Dr. Walter Baade."
Publications of the Astronomical Society of the Pacific 67 (1955): 56-61.