The worlds of observational astrophysics
and 20th-century astronomy history lost a leading figure on 11 January 2007 when Donald Edward
Osterbrock died suddenly of a heart attack while walking near his office at the University of California,
Santa Cruz. He was respectfully called "DEO" by his former students and postdocs and "Don" by his
many friends. His life spanned the period from when astronomy was a small discipline pursued by
a few hundred practitioners and the most powerful telescope was the 100-inch at Mt. Wilson, California,
to our modern era, with more than 7000 members of the American Astronomical Society (AAS), giant
ground-based telescopes, and space telescopes that observe the universe from x-ray energies
through the far infrared.
Don was born in Cincinnati,
Ohio, on 13 July 1924 into a family of German descent. His father, who dropped out of high school to
work full-time, eventually became a professor of electrical engineering at the University of
Cincinnati. Drawn into the vortex of World War II soon after graduating from high school, Don attended
courses and was trained by the US Army at the University of Chicago, then served in the South Pacific.
After being discharged, he returned to Chicago, where he received a BS in physics in 1948, an MS in
astronomy in 1949, and a PhD in astronomy in 1952. At the university's Yerkes Observatory, he worked
with some of the greats of the time—Bengt Strömgren, W. W. Morgan, and his PhD thesis
adviser, Subrahmanyan Chandrasekhar. As a postdoc at Princeton University, he solved the conundrum
of the inner structure of the ubiquitous red dwarf stars.
He moved to the young astronomy
department at Caltech in 1953 and made the transition from being a theoretician to an observational
astrophysicist. In 1958 Don left Caltech for the University of Wisconsin, where a newly formed
and growing astronomy department offered him the opportunity to pursue observational astrophysics
of gaseous nebulae—a field that he made his own—and live in the Midwest environment
that he valued. He was lured back to California in 1973 to become the director of the University of
California's Lick Observatory, which he led until 1981. He remained in Santa Cruz and attained
emeritus status in 1993. He benefited from contact with others and freely shared his ideas; he enjoyed
extended visits to Yerkes Observatory, the Institute for Advanced Study in New Jersey, University
College London (UCL), Ohio State University, and the University of Minnesota.
The work for which he became
most famous was in the area of gaseous nebulae, clouds of space dust and gas whose luminosity is largely
powered by nearby hot stars. These gaseous nebulae include regions of very recent star formation
and of stars at the other end of their life cycle, as they are losing their outer parts. He drew on a
strong background in quantum mechanics to develop, with Michael Seaton of UCL, the method of accurately
determining the physical conditions and abundance of the elements in these remote objects through
spectroscopy of the emission-line spectra. Later, those diagnostic tools were applied to the
recent field of exotic nuclei of galaxies, the active galactic nuclei, and he derived for the objects
the basic physical model that remains in use today. Much of his work is described in his text, which
was originally published in 1974 as Astrophysics of Gaseous Nebulae (W. H. Freeman), expanded
in 1989 and titled Astrophysics of Gaseous Nebulae and Active Galactic Nuclei (University
Science Books), and revised in 2006 (University Science Books) with Gary Ferland of the University
of Kentucky as coauthor. The book continues to have enormous impact.
Although Don continued
his research on active galactic nuclei after stepping down as director of Lick, he turned increasingly
to the history of 20th-century astronomy, the era of big telescopes. He later explained, "History
is too important to be left to the historians," an opinion guaranteed to rankle the "establishment."
However, he brought the rigor of a scientist to the subject and shared that characteristic with
the best historians. The result was a series of books on Lick's brilliant second director, James
Keeler; the first century of the Lick Observatory (with John R. Gustafson and W. J. Shiloh Unruh);
G. W. Ritchey, George Ellery Hale, and big American telescopes; the Yerkes Observatory, 1892–1950;
and the German-American astronomer Walter Baade. Inreaction to thefashionable theories of deconstruction
and sociological analysis promoted by some professional historians, Don adhered to the "great
man" theory of history, in large part because he had personally known so many of the great men of astrophysics.
He was undaunted by the critics, and his efforts were eventually recognized in 2002 by AAS's historical
astronomy division, which presented him with the LeRoy E. Doggett Prize, the highest award given
to a historian of astronomy; it was possibly his most valued accolade.
Don not only contributed
vastly to astronomy and astrophysics, he was also one of the few astronomers with a sufficiently
broad perspective—matched with psychological insight and literary skill—to have
left a rich body of historical writings that will be consulted by future historians and scholars.
In addition to the Doggett
Prize, Don received numerous awards available to American astronomers, including the 1991 Henry
Norris Russell Lectureship from AAS, the 1991 Catherine Wolfe Bruce Gold Medal from the Astronomical
Society of the Pacific, and the 1997 Gold Medal from the Royal Astronomical Society. He was a member
of the National Academy of Sciences and the Academia Mexicana de Ciencias, and he served as AAS president
from 1988 to 1990.
In a biographical article
in 2000, Don called his career "A Fortunate Life in Astronomy" (Annual Review of Astronomy and
Astrophysics, volume 38, page 1). Those of us who shared that life as his students, postdocs,
and colleagues consider ourselves the fortunate ones.
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