William Pendry Bidelman ( ; September 25, 1918 – May 3, 2011) was an American astronomer. Born in Los Angeles, and raised in North Dakota, he was noted for classifying the spectra of stars, and considered a pioneer in recognizing and classifying sub-groups of the peculiar stars. Bidelman's undergraduate degree was from Harvard College, and his Ph.D. in astronomy was from the University of Chicago under advisor William Wilson Morgan. He was a physicist in the Army during World War II. A professional astronomer for over 50 years, Bidelman taught for ~41 years at The University of Chicago, The University of California, He co-discovered the class of barium stars with Philip Keenan, the phosphorus and the mercury stars, and was the first to describe the hydrogen-deficient carbon stars. Born in Los Angeles, California, Bidelman was raised in North Dakota, where he met his future wife of 69 years. He was a father of four and a grandfather. As an Emeritus Professor William P. Bidelman continued working in astronomy after he retired from teaching, and was 92 when he died in Murfreesboro, Tennessee. Education As an undergraduate at Harvard College, Bidelman received an Honorary Harvard College Scholarship for academic excellence in 1939. He graduated in 1940. Bidelman entered the graduate program at the University of Chicago affiliated with Yerkes Observatory. His doctoral advisor was William W.Morgan, who discovered the first definite evidence that the Milky Way Galaxy is a spiral galaxy, and, with Philip Keenan, the Morgan-Keener (MK) system of stellar classification. As a graduate student, Bidelman assisted Morgan and Keenan by taking some of the spectrograms for their book, An Atlas of Stellar Spectra. For his 1943 dissertation, Bidelman reported the Double Cluster in the I Persei association is physically associated with neighborhood supergiant stars, and is part of an association of O- and B-type stars, and designated 47 stars as its members. Bidelman received his Ph.D. in 1943. The Yerkes astronomy graduate program directed by Otto Struve began issuing degrees in 1940, and he was among their first ten graduates. Career Bidelman served in the U.S. Army's Ballistic Research Laboratory at Aberdeen Proving Ground for over 2 years during World War II,. He attended the 1942 American Astronomical Society's annual meeting despite a small assembly due to gasoline rationing during World War II. University of Chicago, Yerkes Observatory In 1945, when Bidelman left Aberdeen he was hired at Yerkes