Biographical Memoirs Volume 47 (1975) / Chapter Skim
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6 Alfred Harrison Joy
6 Alfred Harrison Joy
Pages 224-247
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C WILSON THE MOUNT WILSON OBSERVATORY was founded in 1904 by George Ellery Hale who at that time succeeded in enlisting the support of the Carnegie Institution of Washington.
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This was a method that had recently been worked out by Adams and A Kohlschutter to determine absolute magnitudes of stars by noting the relative intensities of certain absorption lines in their spectra.
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The installation of the large Mount Wilson reflectors, together with improved spectrographs and photographic plates, now began to open up for exploration a vast region of fainter objects containing a great variety of fascinating stars of widely divergent properties. Joy and the other members of the spectroscopic group at Mount Wilson lost no time in taking advantage of these opportunities.
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Much of this work originated in the large observatory observing programs previously mentioned. But while this work leas in progress Joy was also busy collecting information on a wide variety of variable stars.
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Even today, the proper relationship of these stars to other variable or nonvariable objects does not appear to be certa~n. In connection with his studies of the intrinsically bright variable stars, Joy obtained spectrograms of W Vir as early as 1925 that showed that this type of Cepheid differed in spectral behavior from the standard ones as well as having different spatial distribution in the galaxy.
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One of the most significant results was that Joy was able to identify most of the absorption features that annear in the strong hv~lro~en emission lines as due to metallic or molecular lines, thus demonstrating that the region where the hydrogen emission is produced lies below that responsible for the normal absorption line spectrum. To this point we have dealt with Joy's work on intrinsically bright variables.
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As the eclipse of the B9 star progressed, Joy found that the hydrogen lines showed first a widely red displaced emission component, then no emission at all near the center of eclipse, and lastly a widely violet displaced emission component. These observations indicate that the B9 star is surrounded by a rapidly rotating ring of matter in which the emission lines are produced.
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Alfred {oy was secretary of the Mount Wilson Observatory from 1920 until his retirement in 1948 and thus had a number of administrative chores in addition to his research. He served as president of the Astronomical Society of the Pacific several times and as president of the American Astronomical Society in 1950-1952.
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- Astronomical Society of the Pacific Leaflet Astrophys.
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Eighteen stars with spectra similar to those of the Cepheid variables.
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Evidence regarding the giant and dwarf division of stars afforded by recent Mount Wilson parallaxes.
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Spectroscopic notes on some variable stars.
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Ninety-seven stars with variable radial velocity.
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Spectral types, absolute magnitudes, and spectroscopic parallaxes of 412 M-type stars.
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The relationship of spectral type to period among variable stars. Science, 65:453; Proc.
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J., 75:127. The dispersion in the radial velocities and the galactic distribution of variable stars of intermediate and short period.
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Spectroscopic observations of V Canum Venaticorum. Astrophys.
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i., 92:396-99. 1941 A survey of the spectra of variable stars having irregular light changes or periods from 50 to 180 days.
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Pac., 57: 171-74. T Tauri variable stars.
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J., 108: 234-36. 1949 Eight faint dwarf stars having no emission lines.
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l., 57:16. 1954 Variable stars of low luminosity.
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8 pp. 1960 Spectra of dwarf variable stars.
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8 pp. Mount Wilson solar physicist dies (Harold D
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