PARKHURST, JOHN ADELBERT

(b. Dixon, Illinois, 24 September 1861; d.Williams Bay, Wisconsin, 1 March 1925)

astronomy.

Parkhurst was the son of Sanford and Clarissa J. Hubbard Parkhurst. Upon the death of his mother, when he was five years old, he was adopted by his aunt and uncle Dr. and Mrs. Abner Hagar, who lived in Marengo, Illinois. After completing public schools there, he attended Wheaton College, Wheaton, Illinois, from 1878 to 1881. Parkhurst graduated from the Rose Polytechnic Institute, Terre Haute, Indiana, in 1886 with a B.S. in mechanical engineering and remained there as instructor of mathematics for the next two years; in 1897 he received an M.S. from Rose.

He married Anna Greenleaf of Terre Haute, Indiana, in 1888; their only child died in infancy. From childhood, when he walked with crutches, until his death, caused by a cerebral hemorrhage, Parkhurst suffered from poor health but nevertheless worked diligently. He was a member of the American Astronomical Society, the British Astronomical Association, and the Astronomische Gesellschaft of Hamburg, and was a fellow of the Royal Astronomical Society. For many years he was active in the Congregational Church in Williams Bay and was elected the first town supervisor.

Parkhurst’s interest in astronomy was stimulated by reading the works of Thomas Dick. Although his time in Marengo was devoted principally to business, he spent his leisure hours making astronomical observations, mainly of variable stars. Within a decade that part-time research had led to approximately fifty published papers.

After occasionally serving as a nonresident computer of the Washburn Observatory, Parkhurst made an important change in his professional life with the opening in 1897 of the University of Chicago’s Yerkes Observatory. In 1898 he became a volunteer research assistant at Yerkes; and in 1900, with his appointment as assistant, he began working full time on astronomy. He remained at Yerkes until his death twenty-five years later, having progressed to the rank of associate professor in 1919.

Parkhurst’s first published paper at Yerkes, “The Spectra of Stars of Secchi’s Fourth Type,” was written with George E. Hale and Ferdinand Ellerman. His specialty was stellar photometry, both visual and photographic. In 1906 the Carnegie Institution of Washington published his longest work, Researches in Stellar Photometry During the Years 1894 to 1906, Made Chiefly at the Yerkes observatory. Perhaps his most important paper, however, was “Yerkes Actinometry, “published in 1912. It contained his determinations of the visual and photographic magnitudes, color indexes, and spectral classes of all stars brighter than apparent magnitude 7.5 between +73° north declination and the celestial north pole.

As Yerke’s representative, Parkhurst began collaborating in 1900 with Harvard, Lick, and McCormick observatories in a comparison, published in 1923, of the brightnesses of faint stars with those of known bright stars. He also helped prepare no. XII of the appendix to J. G. Hagen’s Atlas stellarum variabilium; and he determined the photographic magnitudes and color indexes of 1,500 stars in twenty-four Kapteyn Fields, the report of which was published posthumously.

Parkhurst participated in three solar eclipse expeditions to measure coronal brightness but encountered clear skies for only one—that of 24 January 1925, shortly before his death.

BIBLIOGRAPHY

I. Original Works. Parkhurst published nearly 100 papers, principally in Astronomical Journal, Astrophysical Journal, Astronomische Nachrichten, and Popular Astronomy. His key works include Researches in Stellar Photometry During the Years 1894 to 1906, Made Chiefly at the Yerkes Observatory (Washington, D.C., 1906); “Yerkes Actinometry,” in Astrophysical Journal, 36 (1912), 169–227; “Photometric Magnitudes of Faint Standard Stars Measured Visually at Harvard, Yerkes, Lick and McCormick Observatories,” in Memories of the American Academy of Arts and Sciences, 14 , no. 4 (1923), 209–307, written with S. A. Mitchell et al.; “Methods Used in Stellar Photographic Photometry at the Yerkes Observatory Between 1914 to 1924,” in Astrophysical Journal,62 (1925), 179–190, written with Alice Hall Farnsworth; and “Zone +45^o of Kapteyn’s Selected Area: Photographic Photometry for 1,550 Stars,” in Publications of the Yerkes Observatory, 4 , pt. 6 (1927), 230–289.

II. Secondary Literature. Biographical information is given in J. McKeen and Dean R. Brimell, eds., American Men of Science (Lancaster, Pa., 1921), 526; and in Poggendorff, VI , 1951. A biographical sketch by Raymond S. Dugan is in Dictionary of American Biography, XIV, 246–247. Obituaries are by R. G. Aitken and E. B. Frost, in Publications of the Astronomical Society of the Pacific,37 (1925), 85–88; by Storrs B . Barrett, in Popular Astronomy, 33 (1925), 280-284,which includesa portrait from 1923; and by E. B. Frost in Astrophysical Journal, 61 (1925), 454. There are unsigned obituaries in Astronomische Nachrichten,224 (1925), 147–148; in Observatory,48 (1925), 120; and in Monthly Notices of the Royal Astronomical Society, 86 (1926), 185–186.

Richard Berendzen