Rubin, Vera, 1928–2016, American astronomer, b. Philadelphia as Vera Florence Cooper, Ph.D. Georgetown (1954). After teaching at Georgetown, she joined (1965) the Carnegie Institution's department of terrestrial magnetism in Washington, D.C.; she became the first woman authorized to use the Palomar Observatory. In the 1960s, Rubin's interest in how stars orbit the galactic center led to her studies with colleague Kent Ford. Mapping the distribution of mass in several spiral galaxies through measurements of their rotation, expecting to find that objects farther from the visible concentration of mass near the center would orbit slower than those closer to it (in conformation with gravitational theory), they discovered that stars on the outskirts of galaxies traveled as fast as those near the center. This led them to conclude that something other than the visible matter was responsible for the stars' motions, and their work affirmed the existence of what is now known as dark matter , which makes up about 85% of all matter in the universe. Rubin was awarded the National Medal of Science in 1993.
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