Photo courtesy Yerkes Observatory, University of Chicago
Walter Sydney Adams
20 December 1876	1928 Bruce Medalist	11 May 1956

Walter Adams was born in Syria, the son of American missionaries. After receiving his bachelor's degree at Dartmouth College, he accompanied his astronomy professor, Edwin B. Frost, to Yerkes Observatory, where he began graduate study. After two years there and one more year of study at Munich, he was summoned by his Yerkes director, George Ellery Hale, to help establish the Mt. Wilson Solar Observatory. There he served first as Hale's deputy and later as director from 1923 to 1945. His spectroscopic studies of the sun, done with Hale and others, led to the discovery that the sunspots are regions of lower temperatures and stronger magnetic fields than their surroundings. Turning to the stars, he made the discovery, with Arnold Kohlschütter, of a spectroscopic method for determining stellar distances: they showed that the relative intensities of spectral lines could be used to determine absolute magnitudes of both giant and main sequence stars. Adams used photography to measure the differential rotation of the sun. He shared with Theodore Dunham, Jr. in the discoveries of carbon dioxide in the atmosphere of Venus and the molecules CN and CH in interstellar gas clouds. Adams identified Sirius B as the first white dwarf star known, and his measurement of its gravitational redshift was taken as confirming evidence for the general theory of relativity. In retirement he continued his research at the Hale Solar Laboratory in Pasadena, California.

Presentation of Bruce medal
Merrill, Paul W., PASP 40, 2-10 (1928).

Other awards
American Astronomical Society, Henry Norris Russell Lectureship, 1947.
French Academy of Sciences, Janssen Medal, 1935.
National Academy of Sciences, Henry Draper Medal, 1918.
Royal Astronomical Society, Gold medal, 1917, presented by R.A. Sampson, MNRAS 77, 395-410 (1917)
Société Astronomique de France, Janssen Prize, 1926.

Some offices held
American Astronomical Society, President, 1931-34.
Astronomical Society of the Pacific, President, 1923.

Biographical materials
Adams, Sue Kelly, About Walter Sydney Adams’ Role in Making Mt. Wilson and Palomar (Trafford Publishing, Victoria, BC, Canada, 2003).
American Philosophical Society
Joy, A.H., Biographical Memoirs of the National Academy of Sciences 31, 1-31 (1958).
Seares, F.H., “Retirement of Dr. Walter S. Adams,” PASP 57, 296-301 (1945).
Stratton, F.J.M., Biographical Memoirs of the Royal Society 2, 1-18 (1956).
Tenn, Joseph S., “Walter S. Adams: The Twenty-Third Bruce Medalist,” Mercury  23, 2, 20 (1994).
Tenn, Joseph S., Biographical Encyclopedia of Astronomers (Springer, NY, 2007), pp. 13-15.
Wright, Helen, Dictionary of Scientific Biography 1, 54-58 (1970-80).

Obituaries
Joy, A.H., PASP 68, 285-95 (1956).
Merrill, Paul W., Year Book of the American Philosophical Society 1956, pp. 103-105.
Merrill, Paul W., “Walter S. Adams, Observer of Sun and Stars,” Science 124, 67 (1956).
Merrill, Paul W., MNRAS 117, 243-44 (1957).
Shapley, Harlow, “A Master of Stellar Spectra,” Sky & Telescope 15, 401 (1956).
Stratton, F.J.M., “Walter S. Adams, 1876-1956,” Observatory 76, 139-140 (1956).

Portraits
AIP Center for History of Physics
Caltech Archives (many)
Dibner Library

Named after him
Lunar crater Adams (with John Couch Adams and Charles H. Adams)
Mars Crater Adams
Minor Planet #3145 Walter Adams

More references