page_title: William P. Bidelman
section_title: University of Chicago, Yerkes Observatory
hierarchical_section_title: William P. Bidelman / Career / University of Chicago, Yerkes Observatory
caption_attribution_description: Front View, Yerkes Observatory — Williams Bay, Wisconsin.
context_page_description: William Pendry Bidelman whose friends called him "Billy", 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.
context_section_description: In 1945, when Bidelman left Aberdeen he was hired at Yerkes as an Instructor. Under Otto Struve Yerkes became the leading astrophysics center, when he directed it. In addition to Bidelman, by 1946 the Yerkes astronomy staff included Paul Ledoux, Arne Slettebak, Armin Deutsch, Marshall Wrubel, Arthur D. Code, Carlos Cesco, Víctor M. Blanco, W. W. Morgan, Otto Struve, Jesse L. Greenstein, Gerard P. Kuiper, George Van Biesbroeck, Louis G. Henyey Anne B. Underhill, Guido Münch, Nancy G. Roman, and the two future Nobel Prize winners, Subrahmanyan Chandrasekhar and Gerhard Herzberg. Other astronomers at Yerkes when Bidelman was there were Kaj Strand, W. Albert Hiltner, Aden B. Meinel, and visiting professors Bengt Strömgren from Denmark, and Jan Oort, Hendrik C. van de Hulst and Adriaan Blaauw from the Netherlands. George Herbig, also there, remembered it as an "exciting, stimulating place to work" and a "powerhouse in astronomy" while under Struve's direction.
  Bidelman spent long hours observing in remote west Texas at McDonald Observatory because he, like other Yerkes faculty, was also an astronomer at the University of Texas (UT). At the suggestion of Struve, the two universities had cooperated to create McDonald Observatory when the UT system had no astronomy department but W. J. McDonald gave them money in 1926 for an observatory, while in Wisconsin, the Yerkes astronomers needed a larger telescope but lacked the funds to obtain one.
  Otto Struve, who directed both Yerkes and McDonald, has been described as dedicated yet demanding. His managerial style included daily inspections of the faculty to see if they were working. Despite reports of tensions there was also "close knit camaraderie" and "boisterous parties" evidenced by Yerkes "spontaneous party songs" including "The Billy Bidelman Song". Sung to the tune of "The Battle Hymn of the Republic", it consisted of repeating three times the line: "Struve, Kuiper, Hiltner, Morgan, Chandrasekhar too," followed by: "And Billy Bidelman".
  In 1946, W. W. Morgan and William P. Bidelman published a paper on interstellar reddening using the MK system of spectral classifications and photoelectric photometry. Morgan later said this paper with Bidelman on interstellar reddening was "the principal paper along the way" to the UBV system, which he devised with Harold Johnson.
  In 1947, Bidelman became first to note the concentration of type M supergiant stars around χ Per, suggesting they were young Population I objects.
  This group, along with the Double Cluster, was later named the Perseus OB1 Association. Based on its radial velocity, Bidelman also became first to see that S Persei is part of the Per OB1 association, which was later confirmed. Among the first stars that were studied at far-infrared wavelengths, M-type supergiants may be used to find the spiral arms of our galaxy. Bidelman found four red supergiant stars in 1947, bringing the total then known to 13. How red supergiant stars evolved was considered an "astronomical puzzle", so the Double Cluster was used to test ideas about the evolution of red supergiant stars during the 1960s. The M-type supergiants of h and χ Per became the prototypes of this class of stars, and the major source of data for their properties.
  Unlike most the usual relatively young star clusters including few supergiant stars, 18 were found in the Double Cluster of Perseus by 2007, which Robert F. Wing noted as the 60th anniversary of Bidelman's "important paper", saying Bidelman's 1947 two-dimensional classifications of the then-known supergiants in h and χ Per had "served as the benchmark" for later studies of the red supergiant stars.
  Hydrogen is the most abundant element in the Universe, so stars displaying very little hydrogen in their atmospheres are chemically peculiar stars. There are many kinds of hydrogen-deficient stars. Upsilon Sagittarii is a hydrogen-deficient star. It is a very luminous, variable, and unusual eclipsing binary with a spectrum quite difficult to classify. In 1949, Bidelman was possibly the first to suggest that Upsilon (υ) Sag
caption: Yerkes, located in the village of Williams Bay, Wisconsin[31] is where faculty and students lived, and they rarely visited the Chicago campus.[32]
exif: {}