She was born in Cheadle, Staffordshire, and lived her entire life in that locale. Mary was the daughter of a solicitor, John Charles Blagg, and France Caroline Foottit. She trained herself in mathematics by reading her brother’s textbooks. In 1875 she was sent to a finishing school in Kensington. There she studied algebra and German. She later worked as a sunday school teacher and was the branch secretary of the “Girls’ Friendly Society”.
By middle age she became interested in astronomy after attending a university extension course, taught by Mr. J. A. Hardcastle. Her tutor suggested working in the area of selenography, particularly on the problem of developing a uniform system of lunar nomenclature. (Several major lunar maps of the period had significant discrepancies in terms of naming the various features.)
In 1905 she was appointed by the newly-formed International Association of Academies to build a collated list of all of the lunar features. She worked with Mr S. A. Saunder on this very tedious and lengthy task, and the result was published in 1913. Her work produced a long list of discrepancies that the association would need to resolve. She also performed considerable work on the subject of variable stars, in collaboration with Professor H. H. Turner. These were published in a series of ten articles in the Monthly Notices, in which the Professor admitted that the large majority of the work had been performed by Mary Blagg.
After the publication of several research papers for the Royal Astronomical Society, she was elected as a fellow in 1916, after being nominated by Professor Turner. She was the first woman to be allowed entry into that society.
In 1920, she joined the Lunar Commission of the newly-formed International Astronomical Union. They tasked her with continuing her work on standardizing the nomenclature, and, together with Karl Müller of Vienna, she produced a two volume set in 1935 that became the standard reference on the subject.
During her life she performed volunteer work, including caring for Belgian refugee children during World War I. One of her favorite hobbies was chess. She was described in her obituary as being of “modest and retiring disposition, in fact very much of a recluse”, and rarely attended meetings.
Blagg crater on the Moon is named for her, on the suggestion of M. Làmech.
* Blagg, M.A., On a Suggested Substitute for Bode’s Law, Monthly Notices of the Royal Astronomical Society, Vol. LXXIII 6, April 1913:414:422.
* M. A. Blagg, Collated List of Lunar Formations, Edinburgh, 1913.
* M. A. Blagg and Karl Müller, Named Lunar Formations, London,1935 — vol. 1, catalogue; vol. 2, map