# Samuel Alfred Mitchell
**Samuel Alfred Mitchell** directed the Leander McCormick Observatory of the [University of Virginia](https://www.edgepedia.org/university-of-virginia) from 1913 to 1945 and became a leading observer of total solar eclipses. He was elected to the National Academy of Sciences in 1933.[1](https://nasonline.org/member-directory/deceased-members/20000744.html)
| Key facts | |
|---|---|
| Field | Astronomy: stellar parallaxes, solar eclipses[2](https://iopscience.iop.org/article/10.1086/127524/pdf) |
| PhD | Johns Hopkins University, 1898, on the concave diffraction grating[3](https://astrogen.aas.org/front/searchdetails.php?agnumber=9869) |
| Directorship | Leander McCormick Observatory and professor of astronomy, University of Virginia, 1913–45[2](https://iopscience.iop.org/article/10.1086/127524/pdf) |
| Parallax program | Approximately 1,700 stellar parallaxes determined with the McCormick 26-inch refractor[2](https://iopscience.iop.org/article/10.1086/127524/pdf) |
| Eclipses | Ten total solar eclipses observed, 1900–1937, more than 100,000 miles of travel[4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell) |
| Honors | National Academy of Sciences (1933); James Craig Watson Medal (1948)[1](https://nasonline.org/member-directory/deceased-members/20000744.html) • [4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell) |
## Early life and training
In 1890, at age 16 and holding a Governor General's scholarship, he began studies at Queen's University.[4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell)
His 1898 doctoral thesis, recorded by the Astronomy Genealogy Project in two parts as "The theory of the concave grating" and "Use of the concave grating in stellar spectroscopy",[3](https://astrogen.aas.org/front/searchdetails.php?agnumber=9869) took the concave diffraction grating as the instrument for photographing stellar spectra, throwing the star image directly into the grating's focus.
## Career record
Mitchell's posts, in dated steps:[2](https://iopscience.iop.org/article/10.1086/127524/pdf)
- Research assistant, [Yerkes Observatory](https://www.edgepedia.org/yerkes-observatory), 1898–99.
- Instructor and adjunct professor, Columbia University, 1899–1913. According to Charles P. Olivier, during the Columbia years Mitchell spent summers at Yerkes in 1907 and 1909–13, working with [Frank Schlesinger](https://www.edgepedia.org/frank-schlesinger) on the photographic determination of stellar parallaxes.[2](https://iopscience.iop.org/article/10.1086/127524/pdf)
- Director of the Leander McCormick Observatory and professor of astronomy, University of Virginia, 1913–45.
- Director emeritus, 1945; in 1947 he wrote a history of the observatory.[4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell)
He died at the home of his son Allan in [Bloomington, Indiana](https://www.edgepedia.org/bloomington-indiana), and was buried in [Charlottesville, Virginia](https://www.edgepedia.org/charlottesville-virginia).[4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell)
## Representative work
**Stellar parallaxes at McCormick.** Working with Schlesinger, who had perfected the photographic method of determining stellar parallaxes, Mitchell made photographic trigonometric parallaxes the main program of the McCormick 26-inch refractor; according to Olivier, he and his staff determined approximately 1,700 parallaxes, a large percentage of all then in the lists.[2](https://iopscience.iop.org/article/10.1086/127524/pdf) The Queen's University guide puts the published total higher, at more than 2,000 stellar parallaxes; the PASP obituary's figure of approximately 1,700 is the contemporary estimate.[2](https://iopscience.iop.org/article/10.1086/127524/pdf) • [4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell) At McCormick he also inaugurated programs on variable stars and comparison-star magnitudes, stellar proper motions, and, with a 10-inch short-focus refractor, spectral classification.[2](https://iopscience.iop.org/article/10.1086/127524/pdf)
**Eclipse expeditions.** Mitchell was a specialist in observing total solar eclipses, present at those in Georgia (1900), Sumatra (1901), Spain (1905), Oregon (1918), California (1923), [Connecticut](https://www.edgepedia.org/connecticut) (1925), Norway (1927), Niuafoou Island (1930), Quebec (1932), and Canton Island (1937), traveling more than 100,000 miles in pursuit of them.[2](https://iopscience.iop.org/article/10.1086/127524/pdf) • [4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell) The expeditions observed from Daroca, Spain (August 30, 1905); Baker, Oregon (June 8, 1918); San Diego, California (September 10, 1923); Van Vleck Observatory, Middletown, Connecticut (January 24, 1925); Fagernas, Norway (June 29, 1927); and Niuafoou, known as "Tin-Can" Island.[5](https://web.archive.org/web/20210121033930/https:/faculty.virginia.edu/mccormick-observatory/mitchell.html) His work on the flash spectrum at the 1905 eclipse was particularly important, and was followed up at later eclipses.[2](https://iopscience.iop.org/article/10.1086/127524/pdf)
**Eclipses of the Sun.** Mitchell published his major work, *Eclipses of the Sun*, in 1923, revised it through the 1930s and 1940s, and issued the fifth and final edition in 1951; the National Academy of Sciences memoir calls it a standard reference book.[4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell)
## Honors and societies
Mitchell was elected to the National Academy of Sciences in 1933,[1](https://nasonline.org/member-directory/deceased-members/20000744.html) which awarded him the James Craig Watson Medal in 1948 for his eclipse observations.[2](https://iopscience.iop.org/article/10.1086/127524/pdf) • [4](https://guides.library.queensu.ca/STEMbookdisplays/Mitchell) The Royal Astronomical Society elected him an Associate on April 12, 1933,[6](https://ras.ac.uk/obituaries/Samuel_Alfred/Mitchell) and the American Academy of Arts and Sciences elected him in 1923, listing him as an astronomer, educator, and observatory administrator of the University of Virginia.[7](https://www.amacad.org/person/samuel-alfred-mitchell) He was also a member of the [American Philosophical Society](https://www.edgepedia.org/american-philosophical-society), served as president of the International Astronomical Union commissions on Solar Eclipses and on Stellar Parallaxes and Proper Motions, and received the LL.D. from Queen's University.[2](https://iopscience.iop.org/article/10.1086/127524/pdf)
## References
1. "Member Directory: Samuel Mitchell", National Academy of Sciences, deceased members. https://nasonline.org/member-directory/deceased-members/20000744.html
2. Charles P. Olivier, "Samuel Alfred Mitchell, 1874–1960", Publications of the Astronomical Society of the Pacific 72 (1960). https://iopscience.iop.org/article/10.1086/127524/pdf
3. "AstroGen – The Astronomy Genealogy Project", entry 9869. https://astrogen.aas.org/front/searchdetails.php?agnumber=9869
4. "Kingston's First Eclipse Chaser", Queen's University Library research guide. https://guides.library.queensu.ca/STEMbookdisplays/Mitchell
5. "Samuel A. Mitchell – Director, 1913–1945", Leander McCormick Observatory, University of Virginia. https://web.archive.org/web/20210121033930/https:/faculty.virginia.edu/mccormick-observatory/mitchell.html
6. "RAS Obituaries: Samuel Alfred Mitchell", Royal Astronomical Society. https://ras.ac.uk/obituaries/Samuel_Alfred/Mitchell
7. "Samuel Alfred Mitchell", American Academy of Arts and Sciences. https://www.amacad.org/person/samuel-alfred-mitchell
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*Topic: Encyclopedia › Physical world and mathematics › Physical and mathematical scientists › Physicists and astronomers › Researchers in planetary science, exoplanets, and observational astronomy › Stellar and galactic astronomers › Modern stellar and galactic astronomers*
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