United States of America · Science / Astronomy. Chronological records rendered directly from the World History Database.
Beginning in 1914, Harlow Shapley began a series of studies of globular clusters, published in about 40 scientific papers. He examined the RR Lyrae variables in the clusters (which he assumed were cepheid variables) and would use their period-luminosity relationship for distance estimates
By assuming a roughly spherical distribution of globular clusters around the galaxys centre, he used the positions of the clusters to estimate the position of the sun relative to the galactic centre.
In 1918, this strongly asymmetrical distribution was used by Harlow Shapley to make a determination of the overall dimensions of the galaxy.
Of the globular clusters within our Milky Way, the majority are found in the vicinity of the galactic core, and the large majority lie on the side of the celestial sky centreed on the core.
While his distance estimate was significant in error, it did demonstrate that the dimensions of the galaxy were much greater than had been previously thought
Harlow Shapley and Helen Sawyer began categorizing clusters according to the degree of concentration the system has toward the core. The most concentrated clusters were identified as Class I, with successively diminishing concentrations ranging to Class XII. This became known as the Shapley-Sawyer Concentration Class
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