Reference Work Entry

Biographical Encyclopedia of Astronomers

pp 571-572

Date:

Deutsch, Armin Joseph

  • Léo HouziauxAffiliated withClass of Sciences, Royal Academy of Belgium Email author 

Born Chicago, Illinois, USA, 25 January 1918

Died Pasadena, California, USA, 11 November 1969

American spectroscopist Armin Deutsch focused on the analysis of the hot (type A) stars, particularly those with strong magnetic fields, with patchy distributions of heavy elements like europium on their surfaces. Deutsch received his BS from the University of Arizona (1940) and his Ph.D. from the University of Chicago (1946) for work at Yerkes Observatory on the spectra of A-type variable stars. His graduate career was interrupted by service as an instructor at a technical training school of the United States Army Air Force at Chanute Field, Illinois (1942–1944). He held positions as assistant astronomer at Yerkes Observatory (1944–1946), instructor at Ohio State University (1946/1947), and instructor (1947–1949) and lecturer (1949/50) at Harvard University, before joining the staff of Mount Wilson and Palomar Observatory in Pasadena in 1951, where he remained until his death.

Beginning at Yerkes and continuing at Mount Wilson and Palomar, Deutsch gradually established that the variations in brightness, absorption line profiles, Zeeman broadening, and surface abundances of the chemical elements of a subset of the A stars, called Ap (for peculiar), could all be explained by an “oblique rotator model,” originally put forward by Horace Babcock and Douglas W. N. Stibbs. The idea was that the north–south axis of a strong magnetic field was not parallel to the rotation axis, so that, through the rotation period (typically a day or two), we see both different field strengths and parts of the surface in which different chemical elements have been concentrated. Particularly important was an analysis of the star α2Canum Venaticorum, carried out with Jesse Greenstein and their student Judith Cohen (now professor of astronomy at the California Institute of Technology).

Toward the end of his life, Deutsch addressed several other problems in hot stars and stellar rotation, particularly the so called blue stragglers (stars whose temperatures and brightnesses make them look younger than the clusters in which they are found). He recognized that many of these are rapid rotators, and suggested that, even though their surfaces slowed down, many stars (including the Sun) might maintain rapidly rotating cores, which could be revealed again later. This connected directly with the gravitation theory of Robert Dicke and Carl Brans, which required the inside of the Sun to rotate rapidly. The correct explanation for straggler rotation is probably that they are merged binary-star pairs.

Deutsch also wrote scientifically-based science fiction, some of which was anthologized in his lifetime.

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